diff --git a/BUILD.bazel b/BUILD.bazel
index 38d79cf..a9631dc 100644
--- a/BUILD.bazel
+++ b/BUILD.bazel
@@ -66,6 +66,7 @@ cc_library(
     srcs = ["util/topology.cc"],
     hdrs = ["util/topology.h"],
     deps = [
+        "@highway//:bit_set",
         "@highway//:hwy",
         "@highway//:topology",
     ],
@@ -111,6 +112,7 @@ cc_library(
         ":threading",
         ":topology",
         ":zones",
+        "//io",
         "@highway//:hwy",
         "@highway//:hwy_test_util",
         "@highway//:profiler",
@@ -139,7 +141,7 @@ cc_test(
         ":kv_cache",
         ":mat",
         ":matmul",
-        ":ops",
+        ":test_util",
         ":threading_context",
         ":weights",
         "@googletest//:gtest_main",  # buildcleaner: keep
@@ -172,8 +174,11 @@ cc_library(
     name = "test_util",
     hdrs = ["util/test_util.h"],
     deps = [
+        ":basics",
+        ":mat",
         "@highway//:hwy",
         "@highway//:hwy_test_util",
+        "@highway//:nanobenchmark",
         "@highway//:stats",
     ],
 )
@@ -440,9 +445,9 @@ cc_test(
         ":gemma_lib",
         ":mat",
         ":ops",
+        ":query",
         ":test_util",
         ":threading_context",
-        ":zones",
         "@googletest//:gtest_main",  # buildcleaner: keep
         "//compression:test_util",
         "//compression:types",
@@ -519,32 +524,70 @@ cc_library(
     ],
 )
 
+cc_test(
+    name = "kv_cache_test",
+    srcs = ["gemma/kv_cache_test.cc"],
+    deps = [
+        ":configs",
+        ":gemma_args",
+        ":kv_cache",
+        ":threading_context",
+        "//testing/base/public:gunit_main",
+        "@highway//:hwy",
+    ],
+)
+
+cc_library(
+    name = "query",
+    hdrs = ["gemma/query.h"],
+    deps = [
+        ":basics",
+        ":gemma_args",
+        ":kv_cache",
+        "@highway//:hwy",
+    ],
+)
+
 cc_library(
     name = "gemma_args",
     hdrs = ["gemma/gemma_args.h"],
     deps = [
         ":args",
         ":basics",
+        ":configs",
         ":mat",
+        ":threading_context",
         "//io",
         "@highway//:hwy",
         "@highway//:profiler",
     ],
 )
 
+cc_test(
+    name = "gemma_args_test",
+    srcs = ["gemma/gemma_args_test.cc"],
+    deps = [
+        ":gemma_args",
+        "@googletest//:gtest_main",  # buildcleaner: keep
+    ],
+)
+
 cc_library(
     name = "gemma_lib",
     srcs = [
         "gemma/attention.cc",
         "gemma/flash_attention.cc",
         "gemma/gemma.cc",
+        "gemma/tensor_stats.cc",
         "gemma/vit.cc",
     ],
     hdrs = [
         "gemma/activations.h",
         "gemma/attention.h",
         "gemma/flash_attention.h",
+        "gemma/flash_structs.h",
         "gemma/gemma.h",
+        "gemma/tensor_stats.h",
         "gemma/vit.h",
     ],
     exec_properties = {
@@ -555,6 +598,7 @@ cc_library(
         "gemma/gemma-inl.h",
     ],
     deps = [
+        ":allocator",
         ":basics",
         ":configs",
         ":gemma_args",
@@ -564,6 +608,7 @@ cc_library(
         ":matmul_env",
         ":model_store",
         ":ops",
+        ":query",
         ":threading",
         ":threading_context",
         ":weights",
@@ -577,8 +622,34 @@ cc_library(
         "@highway//:hwy",
         "@highway//:nanobenchmark",  # timer
         "@highway//:profiler",
+        "@highway//:stats",
         "@highway//:thread_pool",
         "@highway//hwy/contrib/sort:vqsort",
+    ] +
+    [
+    ],
+)
+
+cc_test(
+    name = "gemma_lib_test",
+    srcs = ["gemma/attention_test.cc"],
+    # MatMulEnvs are up to 20GB large.
+    tags = ["requires-mem:28g"],
+    deps = [
+        ":configs",
+        ":gemma_args",
+        ":gemma_lib",
+        ":kv_cache",
+        ":mat",
+        ":matmul_env",
+        ":test_util",
+        ":threading_context",
+        ":weights",
+        "@googletest//:gtest_main",  # buildcleaner: keep
+        "//compression:compress",
+        "//compression:types",
+        "@highway//:hwy",
+        "@highway//:hwy_test_util",
     ],
 )
 
@@ -604,7 +675,6 @@ cc_library(
         ":gemma_args",
         ":gemma_lib",
         ":matmul_env",
-        ":ops",
         ":threading_context",
         ":tokenizer",
         "@google_benchmark//:benchmark",
diff --git a/CMakeLists.txt b/CMakeLists.txt
index a707078..47d7c4c 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -22,7 +22,7 @@ set(CMAKE_CXX_STANDARD 17)
 set(CMAKE_CXX_STANDARD_REQUIRED ON)
 set(CMAKE_EXPORT_COMPILE_COMMANDS ON)
 
-FetchContent_Declare(highway GIT_REPOSITORY https://github.com/google/highway.git GIT_TAG 2a16a50ff61071bb25ddef0ce35d92b0e2b9c579 EXCLUDE_FROM_ALL)
+FetchContent_Declare(highway GIT_REPOSITORY https://github.com/google/highway.git GIT_TAG 3b680cde3a556bead9cc23c8f595d07a44d5a0d5 EXCLUDE_FROM_ALL)
 FetchContent_MakeAvailable(highway)
 
 ## Note: absl needs to be installed by sentencepiece. This will only happen if
@@ -82,6 +82,7 @@ set(SOURCES
   gemma/configs.h
   gemma/flash_attention.cc
   gemma/flash_attention.h
+  gemma/flash_structs.h
   gemma/gemma_args.h
   gemma/gemma-inl.h
   gemma/gemma.cc
@@ -221,6 +222,7 @@ set(GEMMA_TEST_FILES
   compression/nuq_test.cc
   compression/sfp_test.cc
   evals/gemma_test.cc
+  gemma/gemma_args_test.cc
   gemma/flash_attention_test.cc
   gemma/tensor_info_test.cc
   io/blob_store_test.cc
diff --git a/MODULE.bazel b/MODULE.bazel
index 861daba..d60c0f4 100644
--- a/MODULE.bazel
+++ b/MODULE.bazel
@@ -18,7 +18,7 @@ bazel_dep(name = "google_benchmark", version = "1.8.5")
 # Require a more recent version.
 git_override(
     module_name = "highway",
-    commit = "2a16a50ff61071bb25ddef0ce35d92b0e2b9c579",
+    commit = "3b680cde3a556bead9cc23c8f595d07a44d5a0d5",
     remote = "https://github.com/google/highway",
 )
 
diff --git a/README.md b/README.md
index 6294920..0aedf38 100644
--- a/README.md
+++ b/README.md
@@ -55,7 +55,6 @@ Guidelines](https://opensource.google.com/conduct/).
 
     -   CPU-only inference for: Gemma 2-3, PaliGemma 2.
     -   Sampling with TopK and temperature.
-    -   Backward pass (VJP) and Adam optimizer for Gemma research.
 
 -   Optimizations
 
@@ -452,7 +451,7 @@ FetchContent_MakeAvailable(sentencepiece)
 FetchContent_Declare(gemma GIT_REPOSITORY https://github.com/google/gemma.cpp GIT_TAG origin/main)
 FetchContent_MakeAvailable(gemma)
 
-FetchContent_Declare(highway GIT_REPOSITORY https://github.com/google/highway.git GIT_TAG 2a16a50ff61071bb25ddef0ce35d92b0e2b9c579)
+FetchContent_Declare(highway GIT_REPOSITORY https://github.com/google/highway.git GIT_TAG 3b680cde3a556bead9cc23c8f595d07a44d5a0d5)
 FetchContent_MakeAvailable(highway)
 ```
 
@@ -520,13 +519,19 @@ Mikhaylov, Eugene Kliuchnikov, Jan Wassenberg, Jyrki Alakuijala, Lode
 Vandevenne, Luca Versari, Martin Bruse, Phil Culliton, Sami Boukortt, Thomas
 Fischbacher and Zoltan Szabadka. It was removed in 2025-09.
 
-Gemma-2 support was implemented in June/July 2024 with the help of several
-people.
+Gemma 2 support was implemented in June/July 2024 with the help of several
+people including Daniel Keysers and Phil Culliton.
 
 PaliGemma support was implemented in September 2024 with contributions from
 Daniel Keysers.
 
+Gemma 3 support was implemented in January-March 2025 with contributions from
+Daniel Keysers and Phil Culliton.
+
 [Jan Wassenberg](mailto:janwas@google.com) has continued to contribute many
 improvements, including major gains in efficiency, since the initial release.
 
+[Phil Culliton](mailto:philculliton@google.com) has worked on model releases,
+eval and validation, GTM, and quantization, since the initial release.
+
 This is not an officially supported Google product.
diff --git a/compression/BUILD.bazel b/compression/BUILD.bazel
index c04bd08..4221a8d 100644
--- a/compression/BUILD.bazel
+++ b/compression/BUILD.bazel
@@ -1,4 +1,4 @@
-# Weight compression and analysis.
+# Compressed tensor types.
 
 load("@rules_cc//cc:cc_library.bzl", "cc_library")
 load("@rules_cc//cc:cc_test.bzl", "cc_test")
@@ -101,13 +101,11 @@ cc_test(
     # for test_suite.
     tags = ["hwy_ops_test"],
     deps = [
-        ":distortion",
         ":int",
         "@googletest//:gtest_main",  # buildcleaner: keep
         "//:test_util",
         "@highway//:hwy",
         "@highway//:hwy_test_util",
-        "@highway//:nanobenchmark",
     ],
 )
 
@@ -135,8 +133,8 @@ cc_test(
     # for test_suite.
     tags = ["hwy_ops_test"],
     deps = [
+        ":compress",
         ":distortion",
-        ":sfp",
         "@googletest//:gtest_main",  # buildcleaner: keep
         "//:test_util",
         "@highway//:hwy",
@@ -182,7 +180,6 @@ cc_library(
         "//:mat",
         "//:threading_context",
         "@highway//:hwy",
-        "@highway//:nanobenchmark",
         "@highway//:profiler",
         "@highway//:stats",
         "@highway//:thread_pool",
@@ -209,19 +206,3 @@ cc_test(
         "@highway//:hwy_test_util",
     ],
 )
-
-# For internal experimentation
-cc_library(
-    name = "analyze",
-    textual_hdrs = ["analyze.h"],
-    deps = [
-        ":int",
-        ":nuq",
-        ":sfp",
-        ":types",
-        "@highway//:hwy",
-        "@highway//:stats",
-        "@highway//:thread_pool",
-        "@highway//hwy/contrib/sort:vqsort",
-    ],
-)
diff --git a/compression/analyze.h b/compression/analyze.h
deleted file mode 100644
index 7d41633..0000000
--- a/compression/analyze.h
+++ /dev/null
@@ -1,238 +0,0 @@
-// Copyright 2024 Google LLC
-// SPDX-License-Identifier: Apache-2.0
-//
-// Licensed under the Apache License, Version 2.0 (the "License");
-// you may not use this file except in compliance with the License.
-// You may obtain a copy of the License at
-//
-//     https://www.apache.org/licenses/LICENSE-2.0
-//
-// Unless required by applicable law or agreed to in writing, software
-// distributed under the License is distributed on an "AS IS" BASIS,
-// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
-// See the License for the specific language governing permissions and
-// limitations under the License.
-
-// Normal include guard to placate lint.
-#ifndef THIRD_PARTY_GEMMA_CPP_COMPRESSION_ANALYZE_H_
-#define THIRD_PARTY_GEMMA_CPP_COMPRESSION_ANALYZE_H_
-
-#include <stddef.h>
-#include <stdint.h>
-#include <stdio.h>
-#include <string.h>  // memcpy
-
-#include <cmath>    // std::signbit
-#include <cstdlib>  // std::abs
-#include <vector>
-
-#include "compression/types.h"
-#include "hwy/base.h"
-#include "hwy/contrib/thread_pool/thread_pool.h"
-#include "hwy/stats.h"
-
-#endif  // THIRD_PARTY_GEMMA_CPP_COMPRESSION_ANALYZE_H_
-
-// Actual per-target include guard.
-#if defined(THIRD_PARTY_GEMMA_CPP_ANALYZE_TOGGLE) == defined(HWY_TARGET_TOGGLE)
-#ifdef THIRD_PARTY_GEMMA_CPP_ANALYZE_TOGGLE
-#undef THIRD_PARTY_GEMMA_CPP_ANALYZE_TOGGLE
-#else
-#define THIRD_PARTY_GEMMA_CPP_ANALYZE_TOGGLE
-#endif
-
-#include "compression/nuq-inl.h"
-#include "compression/sfp-inl.h"
-#include "hwy/contrib/sort/vqsort-inl.h"
-#include "hwy/highway.h"
-
-HWY_BEFORE_NAMESPACE();
-namespace gcpp {
-namespace HWY_NAMESPACE {
-
-class PerThread {
- public:
-  void NotifyGroup(const float* group) {
-    constexpr size_t kGroupSize = NuqStream::kGroupSize;
-    hwy::Stats s_group;
-    for (size_t i = 0; i < kGroupSize; ++i) {
-      // Skip zero so we can see the lowest actual magnitude
-      if (group[i] == 0.0f || group[i] == -0.0f) continue;
-      s_all_.Notify(group[i]);
-      s_group.Notify(group[i]);
-
-      num_tiny_ += std::abs(group[i]) < 1e-3f;
-
-      // b_magn100_.Notify(group[i] * 40.0f + 20.0f);
-      const uint32_t binary32 =
-          hwy::BitCastScalar<uint32_t>(std::abs(group[i]));
-
-      // const int32_t exp = (binary32 >> 23) - 127;
-      b_exp256_.Notify(binary32 >> 23);
-      const uint32_t m4 = (binary32 & 0x7FFFFF) >> (23 - 4);
-      b_m4_.Notify(m4);
-    }
-    s_group_ranges_.Notify(s_group.Max() - s_group.Min());
-    s_group_mins_.Notify(s_group.Min());
-    s_group_maxs_.Notify(s_group.Max());
-
-    float desc[kGroupSize];
-    memcpy(desc, group, kGroupSize * sizeof(group[0]));
-    hn::VQSortStatic(desc, kGroupSize, hwy::SortDescending());
-
-    // Find largest |max/min| (dynamic range)
-    float max_ratio = 0.0f;
-    for (size_t i = 0; i < kGroupSize; ++i) {
-      if (desc[i] != 0.0f && desc[i] != -0.0f) {
-        max_ratio = std::max(max_ratio, std::abs(desc[0] / desc[i]));
-      }
-    }
-    s_group_max_vs_min_.Notify(max_ratio);
-
-    // Relative errors
-    float diffs[kGroupSize];
-    for (size_t i = 0; i < kGroupSize - 1; ++i) {
-      // was in descending order. Avoid div by 0. Ignore sign changes.
-      diffs[i] = std::abs(desc[i]) < 1e-5
-                     ? 0
-                     : std::abs((desc[i] - desc[i + 1]) / desc[i]);
-    }
-    hn::VQSortStatic(diffs, kGroupSize, hwy::SortDescending());
-    s_cut15_.Notify(diffs[15]);
-  }
-
-  void Assimilate(const PerThread& other) {
-    num_tiny_ += other.num_tiny_;
-    s_all_.Assimilate(other.s_all_);
-    s_group_ranges_.Assimilate(other.s_group_ranges_);
-    s_group_mins_.Assimilate(other.s_group_mins_);
-    s_group_maxs_.Assimilate(other.s_group_maxs_);
-    s_group_max_vs_min_.Assimilate(other.s_group_max_vs_min_);
-    s_erange_.Assimilate(other.s_erange_);
-    s_km_1_.Assimilate(other.s_km_1_);
-    s_km_2_.Assimilate(other.s_km_2_);
-    s_cut15_.Assimilate(other.s_cut15_);
-    b_magn100_.Assimilate(other.b_magn100_);
-    b_exp256_.Assimilate(other.b_exp256_);
-    b_m4_.Assimilate(other.b_m4_);
-  }
-
-  void PrintAll() {
-    const int skip = hwy::Stats::kNoGeomean;
-    fprintf(stderr, "num tiny %zu\n", num_tiny_);
-    fprintf(stderr, "weights %s\n", s_all_.ToString(skip).c_str());
-    fprintf(stderr, " ranges %s\n", s_group_ranges_.ToString(skip).c_str());
-    fprintf(stderr, "   mins %s\n", s_group_mins_.ToString(skip).c_str());
-    fprintf(stderr, "   maxs %s\n", s_group_maxs_.ToString(skip).c_str());
-    fprintf(stderr, "   Mvm  %s\n", s_group_max_vs_min_.ToString(skip).c_str());
-    fprintf(stderr, "  cut15 %s\n", s_cut15_.ToString(skip).c_str());
-    fprintf(stderr, " erange %s\n", s_erange_.ToString(skip).c_str());
-    fprintf(stderr, "   km1 %s\n", s_km_1_.ToString(skip).c_str());
-    fprintf(stderr, "   km2 %s\n", s_km_2_.ToString(skip).c_str());
-
-    // b_magn100_.Print("magn100");
-    // b_exp256_.Print("exp");
-    // b_m4_.Print("mantissa bits4");
-
-    fprintf(stderr, "\n");
-  }
-
- private:
-  size_t num_tiny_ = 0;
-  hwy::Stats s_all_;
-  hwy::Stats s_group_ranges_;
-  hwy::Stats s_group_mins_;
-  hwy::Stats s_group_maxs_;
-  hwy::Stats s_group_max_vs_min_;
-  hwy::Stats s_erange_;
-  hwy::Stats s_km_1_;
-  hwy::Stats s_km_2_;
-  hwy::Stats s_cut15_;
-  hwy::Bins<100> b_magn100_;
-  hwy::Bins<256> b_exp256_;
-  hwy::Bins<16> b_m4_;
-  uint8_t padding_[64];  // prevent false sharing
-};
-
-class PerLayer {
- public:
-  void NotifyGroup(const float* group) {
-    for (size_t i = 0; i < NuqStream::kGroupSize; ++i) {
-      s_layer_.Notify(group[i]);
-    }
-  }
-
-  void UpdateOutliers(const float* layer, size_t weights_per_layer) {
-    const float layer_mean = s_layer_.Mean();
-    const float layer_sd = s_layer_.StandardDeviation();
-    for (size_t i = 0; i < weights_per_layer; ++i) {
-      num_outliers_ +=
-          std::abs(std::abs(layer[i]) - layer_mean) >= 3.0f * layer_sd;
-    }
-  }
-
-  const hwy::Stats& GetStats() const { return s_layer_; }
-  size_t Outliers() const { return num_outliers_; }
-
- private:
-  hwy::Stats s_layer_;
-  size_t num_outliers_ = 0;
-  uint8_t padding[64];  // prevent false sharing
-};
-
-static HWY_NOINLINE void Analyze(const char* caption, float* mat, size_t layers,
-                                 size_t weights_per_layer,
-                                 hwy::ThreadPool& pool) {
-  std::vector<PerThread> tls;
-  std::vector<PerLayer> per_layer(layers);
-  const auto init = [&](size_t num_threads) {
-    tls.resize(num_threads);
-    return true;
-  };
-
-  pool.Run(0, static_cast<uint32_t>(layers), init,
-           [&](uint32_t idx_layer, size_t idx_thread) {
-             PerThread& self = tls[idx_thread];
-             const float* layer = &mat[idx_layer * weights_per_layer];
-             // For each whole group in the layer
-             for (size_t group_start = 0;
-                  group_start + NuqStream::kGroupSize <= weights_per_layer;
-                  group_start += NuqStream::kGroupSize) {
-               const float* group = layer + group_start;
-               per_layer[idx_layer].NotifyGroup(group);
-               self.NotifyGroup(group);
-             }
-
-             per_layer[idx_layer].UpdateOutliers(layer, weights_per_layer);
-           });
-
-  const int skip = hwy::Stats::kNoGeomean;
-  fprintf(stderr, "\n------------%s\n", caption);
-
-  for (size_t i = 1; i < pool.NumWorkers(); ++i) {
-    tls[0].Assimilate(tls[i]);
-  }
-  tls[0].PrintAll();
-
-  hwy::Stats s_layer_ranges;
-  hwy::Stats s_layer_outliers;
-  for (size_t i = 0; i < layers; ++i) {
-    fprintf(stderr, "  %02zu %s\n", i,
-            per_layer[i].GetStats().ToString(skip).c_str());
-    const float range =
-        per_layer[i].GetStats().Max() - per_layer[i].GetStats().Min();
-    s_layer_ranges.Notify(range);
-    s_layer_outliers.Notify((100.0 * per_layer[i].Outliers()) /
-                            weights_per_layer);
-  }
-  fprintf(stderr, "layer outliers%% %s\n",
-          s_layer_outliers.ToString(skip).c_str());
-  fprintf(stderr, "layer ranges %s\n", s_layer_ranges.ToString(skip).c_str());
-}
-
-// NOLINTNEXTLINE(google-readability-namespace-comments)
-}  // namespace HWY_NAMESPACE
-}  // namespace gcpp
-HWY_AFTER_NAMESPACE();
-
-#endif  // THIRD_PARTY_GEMMA_CPP_COMPRESSION_ANALYZE_H_
diff --git a/compression/compress-inl.h b/compression/compress-inl.h
index 10ce57c..e7bb9d6 100644
--- a/compression/compress-inl.h
+++ b/compression/compress-inl.h
@@ -82,6 +82,8 @@ struct CompressTraits<float> {
     hn::StoreU(raw1, df, packed.ptr + packed_ofs + NF);
   }
 
+  static float ToFloatSlow(const Packed x) { return x; }
+
   template <class DBF16, HWY_IF_BF16_D(DBF16), class VBF16 = hn::Vec<DBF16>>
   static HWY_INLINE void Load2(DBF16 dbf16,
                                const PackedSpan<const Packed>& packed,
@@ -254,6 +256,10 @@ struct CompressTraits<BF16> {
                packed.ptr + packed_ofs);
   }
 
+  static float ToFloatSlow(const Packed x) {
+    return hwy::ConvertScalarTo<float>(x);
+  }
+
   template <class DBF16, HWY_IF_BF16_D(DBF16)>
   static HWY_INLINE void Load2(DBF16 dbf16,
                                const PackedSpan<const Packed>& packed,
@@ -397,6 +403,27 @@ struct CompressTraits<SfpStream> {
     }
   }
 
+  // NOTE: this does not take into account the per-tensor scale.
+  static float ToFloatSlow(const Packed x) {
+    uint32_t sfp = x.byte;
+    HWY_ASSERT(sfp != 0x80);  // -0 is reserved
+
+    const uint32_t sign32 = (sfp & 0x80) << 24;
+    sfp &= 0x7F;
+    const bool large_e = sfp >= 64;
+    const size_t m_bits = large_e ? 3 : 2;
+    uint32_t m = sfp & ((1u << m_bits) - 1u);
+    size_t e = sfp >> m_bits;
+    if (sfp == 0) return 0.0f;
+    const uint32_t e_bias = large_e ? 15 : 23;
+    const uint32_t exp32 = static_cast<uint32_t>(127 + e - e_bias) << 23;
+    const uint32_t mnt32 = m << (23 - m_bits);
+    const uint32_t binary32 = sign32 | exp32 | mnt32;
+    float result;
+    hwy::CopySameSize(&binary32, &result);
+    return result;
+  }
+
   template <class D>  // Caller checks this is f32 or bf16
   static HWY_INLINE void Load2(D d, const PackedSpan<const Packed>& packed,
                                const size_t packed_ofs, hn::Vec<D>& raw0,
@@ -437,6 +464,12 @@ struct CompressTraits<I8Stream> {
     IntCodec::Dec2(d, packed, packed_ofs, raw0, raw1);
   }
 
+  static float ToFloatSlow(const Packed x) {
+    HWY_DASSERT(!"Not supported - requires a stream");
+    return 0.0f;
+  }
+  // Store2 is not yet implemented.
+
   template <class D, typename Raw>
   static HWY_INLINE void DecompressAndZeroPad(
       D d, const PackedSpan<const Packed>& packed, const size_t packed_ofs,
@@ -483,6 +516,10 @@ struct CompressTraits<NuqStream> {
     NuqCodec::Dec2(d, packed, packed_ofs, raw0, raw1);
   }
 
+  static float ToFloatSlow(const Packed x) {
+    HWY_DASSERT(!"Not supported - requires a stream");
+    return 0.0f;
+  }
   // Store2 is not yet implemented.
 
   template <class D, typename Raw>
@@ -604,6 +641,13 @@ HWY_INLINE void DecompressAndZeroPad(DRaw d, const PackedSpan<Packed>& packed,
   Traits::DecompressAndZeroPad(d, MakeConst(packed), packed_ofs, raw, num);
 }
 
+// NOTE: the following are the recommended way to iterate over arrays of
+// potentially compressed elements, including remainder handling. Prefer them
+// over calling `Decompress2` directly, which does not handle remainders.
+// `DecompressAndCall` is for algorithms expressed as `Kernel` objects, such as
+// `Dot`. `Decompress*AndCompress*` are for varying numbers of input arrays and
+// user code expressed as lambdas.
+
 // Invokes `kernel` for the `v.num` elements of `w` and `v`. Decompresses from
 // both into groups of four vectors with lane type `Kernel::Raw`, passes them to
 // `kernel.Update4`; loads the final vector(s) with zero-padding, then passes
@@ -733,8 +777,8 @@ HWY_INLINE float DecompressAndCall(D, const PackedSpan<const VT> v,
                        comp3);
 }
 
-// Similar to `hn::Transform*`, but for compressed `T`. Used by ops-inl.h.
-// `DF` is the decompressed type, typically `float`.
+// Similar to `hn::Transform*`, but for compressed `T`. Used by `ops-inl.h`.
+// `DF` is the decompressed type, typically `float`. Calls `func(df, v_inout)`.
 template <class DF, typename T, class Func>
 HWY_INLINE void DecompressAndCompressInplace(DF df, T* HWY_RESTRICT inout,
                                              size_t num, Func&& func) {
@@ -773,6 +817,7 @@ HWY_INLINE void DecompressAndCompressInplace(DF df, T* HWY_RESTRICT inout,
 }
 
 // One extra argument. `DF` is the decompressed type, typically `float`.
+// Calls `func(df, v_inout, v1)`.
 template <class DF, typename T, typename T1, class Func>
 HWY_INLINE void Decompress1AndCompressInplace(DF df, T* HWY_RESTRICT inout,
                                               size_t num,
@@ -821,8 +866,64 @@ HWY_INLINE void Decompress1AndCompressInplace(DF df, T* HWY_RESTRICT inout,
   }
 }
 
+// Two extra arguments. `DF` is the decompressed type, typically `float`.
+// Calls `func(df, v_inout, v1, v2)`.
+template <class DF, typename T, typename T1, typename T2, class Func>
+HWY_INLINE void Decompress2AndCompressInplace(
+    DF df, T* HWY_RESTRICT inout, size_t num, const T1* HWY_RESTRICT p1,
+    const T2* HWY_RESTRICT p2, const size_t p2_ofs, Func&& func) {
+  const auto packed_inout = MakeSpan(inout, num);
+  const auto packed1 = MakeSpan(p1, num);
+  const auto packed2 = MakeSpan(p2, p2_ofs + num);
+
+  using VF = hn::Vec<decltype(df)>;
+  HWY_LANES_CONSTEXPR const size_t NF = hn::Lanes(df);
+  size_t i = 0;
+  if (num >= 2 * NF) {
+    for (; i <= num - 2 * NF; i += 2 * NF) {
+      VF v0, v1;
+      Decompress2(df, packed_inout, i, v0, v1);
+      VF v10, v11;
+      Decompress2(df, packed1, i, v10, v11);
+      VF v20, v21;
+      Decompress2(df, packed2, p2_ofs + i, v20, v21);
+      const VF out0 = func(df, v0, v10, v20);
+      const VF out1 = func(df, v1, v11, v21);
+      Compress2(df, out0, out1, packed_inout, i);
+    }
+  }
+
+  const size_t remaining = num - i;
+  HWY_DASSERT(remaining < 2 * NF);
+  if (HWY_UNLIKELY(remaining != 0)) {
+    HWY_ALIGN float buf_inout[2 * hn::MaxLanes(df)];
+    HWY_ALIGN float buf1[2 * hn::MaxLanes(df)];
+    HWY_ALIGN float buf2[2 * hn::MaxLanes(df)];
+    // Ensure the second vector is zeroed even if remaining <= NF.
+    hn::Store(hn::Zero(df), df, buf_inout + NF);
+    hn::Store(hn::Zero(df), df, buf1 + NF);
+    hn::Store(hn::Zero(df), df, buf2 + NF);
+    DecompressAndZeroPad(df, packed_inout, i, buf_inout, remaining);
+    DecompressAndZeroPad(df, packed1, i, buf1, remaining);
+    DecompressAndZeroPad(df, packed2, p2_ofs + i, buf2, remaining);
+    const VF v0 = hn::Load(df, buf_inout);
+    const VF v1 = hn::Load(df, buf_inout + NF);
+    const VF v10 = hn::Load(df, buf1);
+    const VF v11 = hn::Load(df, buf1 + NF);
+    const VF v20 = hn::Load(df, buf2);
+    const VF v21 = hn::Load(df, buf2 + NF);
+    const VF out0 = func(df, v0, v10, v20);
+    const VF out1 = func(df, v1, v11, v21);
+    Compress2(df, out0, out1, MakeSpan(buf_inout, 2 * NF), 0);
+    // Clang generates incorrect code for CopyBytes if num = 2.
+    for (size_t j = 0; j < remaining; ++j) {
+      inout[i + j] = hwy::ConvertScalarTo<T>(buf_inout[j]);
+    }
+  }
+}
+
 // Single input, separate output. `DF` is the decompressed type, typically
-// `float`.
+// `float`.  Calls `func(df, v1)`.
 template <class DF, typename T, typename T1, class Func>
 HWY_INLINE void Decompress1AndCompressTo(DF df, T* HWY_RESTRICT out, size_t num,
                                          const T1* HWY_RESTRICT p1,
@@ -863,7 +964,8 @@ HWY_INLINE void Decompress1AndCompressTo(DF df, T* HWY_RESTRICT out, size_t num,
   }
 }
 
-// Two inputs. `DF` is the decompressed type, typically `float`.
+// Two inputs, separate output. `DF` is the decompressed type, typically
+// `float`. Calls `func(df, v1, v2)`.
 template <class DF, typename T, typename T1, typename T2, class Func>
 HWY_INLINE void Decompress2AndCompressTo(DF df, T* HWY_RESTRICT out, size_t num,
                                          const T1* HWY_RESTRICT p1,
@@ -912,7 +1014,8 @@ HWY_INLINE void Decompress2AndCompressTo(DF df, T* HWY_RESTRICT out, size_t num,
   }
 }
 
-// Three inputs. `DF` is the decompressed type, typically `float`.
+// Three inputs, separate output. `DF` is the decompressed type, typically
+// `float`. Calls `func(df, v1, v2, v3)`.
 template <class DF, typename T, typename T1, typename T2, typename T3,
           class Func>
 HWY_INLINE void Decompress3AndCompressTo(DF df, T* HWY_RESTRICT out, size_t num,
diff --git a/compression/compress_test.cc b/compression/compress_test.cc
index 987f409..421492e 100644
--- a/compression/compress_test.cc
+++ b/compression/compress_test.cc
@@ -259,6 +259,13 @@ class TestDecompressAndCompress {
             [](DF, VF v, VF v1) HWY_ATTR -> VF { return hn::Add(v, v1); });
         HWY_ASSERT_ARRAY_EQ(expected2.get(), out.get(), num);
 
+        // `out` already contains v + v1.
+        Decompress2AndCompressInplace(
+            df, out.get(), num, p1.get(), p2.get(), /*p2_ofs=*/0,
+            [](DF, VF v, VF /*v1*/, VF v2)
+                HWY_ATTR -> VF { return hn::Add(v, v2); });
+        HWY_ASSERT_ARRAY_EQ(expected3.get(), out.get(), num);
+
         Decompress1AndCompressTo(df, out.get(), num, p.get(),
                                  [](DF, VF v) HWY_ATTR -> VF { return v; });
         HWY_ASSERT_ARRAY_EQ(expected1.get(), out.get(), num);
diff --git a/compression/nuq-inl.h b/compression/nuq-inl.h
index 997bb5b..ce387f9 100644
--- a/compression/nuq-inl.h
+++ b/compression/nuq-inl.h
@@ -480,9 +480,12 @@ class NibbleCodec {
     static_assert(kHalf <= 1);
     const size_t N = hn::Lanes(d8);
     constexpr size_t kMaxN = hn::MaxLanes(d8);
+    constexpr bool kPermuteAcrossBlocks =
+        HWY_TARGET <= HWY_AVX3_DL || !HWY_ARCH_X86;
     // For kHalf=1 and 512-bit vectors, kAdd would be 16, which is out of
     // bounds for TableLookupBytes. We instead BroadcastBlock<1> there.
-    constexpr uint8_t kAdd = kMaxN < 64 ? kHalf * kMaxN / 4 : 0;
+    constexpr uint8_t kAdd =
+        kMaxN < 64 || kPermuteAcrossBlocks ? kHalf * kMaxN / 4 : 0;
     // The only performance-portable op to replicate bytes is TableLookupBytes,
     // but this only works if vectors are 128-bit or we first BroadcastBlock,
     // which only works for <= 512-bit vectors. For scalable vectors, we
@@ -506,7 +509,7 @@ class NibbleCodec {
     } else if constexpr (kMaxN <= 16) {  // <= 128-bit
       // No BroadcastBlock, we anyway only have one block.
       return hn::TableLookupBytes(bytes, hn::Load(d8, kRep4));
-    } else if constexpr (HWY_TARGET <= HWY_AVX3_DL || !HWY_ARCH_X86) {
+    } else if constexpr (kPermuteAcrossBlocks) {
       // No BroadcastBlock, can directly permute across blocks.
       return hn::TableLookupLanes(bytes, hn::SetTableIndices(d8, kRep4));
     } else {  // 256..512-bit, no efficient TableLookupLanes
diff --git a/compression/python/BUILD.bazel b/compression/python/BUILD.bazel
index 4d9b2ac..e3b7e36 100644
--- a/compression/python/BUILD.bazel
+++ b/compression/python/BUILD.bazel
@@ -26,7 +26,6 @@ cc_library(
         "//io",
         "//io:blob_store",
         "@highway//:hwy",
-        "@highway//:thread_pool",
     ],
 )
 
diff --git a/compression/sfp_test.cc b/compression/sfp_test.cc
index 8e49ceb..df3e846 100644
--- a/compression/sfp_test.cc
+++ b/compression/sfp_test.cc
@@ -37,37 +37,23 @@
 #include "hwy/foreach_target.h"  // IWYU pragma: keep
 #include "hwy/highway.h"
 // After highway.h
-#include "compression/sfp-inl.h"
+#include "compression/compress-inl.h"
 #include "hwy/tests/test_util-inl.h"
 
 HWY_BEFORE_NAMESPACE();
 namespace gcpp {
 namespace HWY_NAMESPACE {
 
-// Decode
-float F32FromSFP8(uint32_t sfp) {
-  HWY_ASSERT(sfp < 256);
-  HWY_ASSERT(sfp != 0x80);  // -0 is reserved
+HWY_INLINE_VAR constexpr bool kPrint = false;
 
-  const uint32_t sign32 = (sfp & 0x80) << 24;
-  sfp &= 0x7F;
-  const bool large_e = sfp >= 64;
-  const size_t m_bits = large_e ? 3 : 2;
-  uint32_t m = sfp & ((1u << m_bits) - 1u);
-  size_t e = sfp >> m_bits;
-  if (sfp == 0) return 0.0f;
-  const uint32_t e_bias = large_e ? 15 : 23;
-  const uint32_t exp32 = static_cast<uint32_t>(127 + e - e_bias) << 23;
-  const uint32_t mnt32 = m << (23 - m_bits);
-  const uint32_t binary32 = sign32 | exp32 | mnt32;
-  float result;
-  hwy::CopySameSize(&binary32, &result);
-  return result;
+static float F32FromSFP8(uint32_t sfp) {
+  return CompressTraits<SfpStream>::ToFloatSlow(
+      SfpStream{static_cast<uint8_t>(sfp)});
 }
 
 // Used for HWY_AVX3_DL and newer.
 void PrintTables() {
-  if (HWY_ONCE && false) {
+  if (HWY_ONCE && kPrint) {
     uint8_t hi[128];
     fprintf(stderr, "lo\n");
     for (uint32_t sfp = 0; sfp < 128; ++sfp) {
@@ -92,7 +78,7 @@ void TestAllUnique() {
     unique.insert(F32FromSFP8(sfp));
   }
   HWY_ASSERT_EQ(size_t{255}, unique.size());
-  if (false) {
+  if (kPrint) {
     for (float f : unique) {
       fprintf(stderr, "%e\n", f);
     }
@@ -163,7 +149,7 @@ HWY_INLINE uint32_t SFP8FromF32(float f) {
     if (m == 0) m = 1;
   }
 
-  if (false) {
+  if (kPrint) {
     fprintf(stderr, "in %x round %x rounded %x e %d m %x large_e %d\n",
             org_binary32, round, rounded, e, m, large_e);
   }
diff --git a/compression/test_util-inl.h b/compression/test_util-inl.h
index 81442f7..f2c8b8c 100644
--- a/compression/test_util-inl.h
+++ b/compression/test_util-inl.h
@@ -105,7 +105,7 @@ MatStorageT<MatT> GenerateMat(const Extents2D& extents, MatPadding padding,
   MatStorageT<float> raw("raw", extents, ctx.allocator, MatPadding::kPacked);
   MatStorageT<MatT> compressed("mat", extents, ctx.allocator, padding);
   const float scale = SfpStream::kMax / extents.Area();
-  ParallelFor(ParallelismStrategy::kFlat, extents.rows, ctx, /*cluster_idx=*/0,
+  ParallelFor(Parallelism::kFlat, extents.rows, ctx, /*cluster_idx=*/0,
               Callers::kTest, [&](size_t r, size_t thread) {
                 float* HWY_RESTRICT row = raw.Row(r);
                 for (size_t c = 0; c < extents.cols; c++) {
@@ -134,7 +134,7 @@ MatStorageT<MatT> GenerateTransposedMat(const Extents2D extents,
   MatStorageT<float> raw("raw", extents, ctx.allocator, MatPadding::kPacked);
   MatStorageT<MatT> compressed("trans", extents, ctx.allocator, padding);
   const float scale = SfpStream::kMax / extents.Area();
-  ParallelFor(ParallelismStrategy::kFlat, extents.rows, ctx, /*cluster_idx=*/0,
+  ParallelFor(Parallelism::kFlat, extents.rows, ctx, /*cluster_idx=*/0,
               Callers::kTest, [&](size_t r, size_t thread) {
                 float* HWY_RESTRICT row = raw.Row(r);
                 for (size_t c = 0; c < extents.cols; c++) {
diff --git a/evals/benchmark.cc b/evals/benchmark.cc
index 4dec9ee..69cd644 100644
--- a/evals/benchmark.cc
+++ b/evals/benchmark.cc
@@ -23,7 +23,9 @@ using json = nlohmann::json;
 
 class BenchmarkArgs : public ArgsBase<BenchmarkArgs> {
  public:
-  BenchmarkArgs(int argc, char* argv[]) { InitAndParse(argc, argv); }
+  BenchmarkArgs(int argc, char* argv[], ConsumedArgs& consumed) {
+    InitAndParse(argc, argv, consumed);
+  }
 
   Path summarize_text;
   Path cross_entropy;
@@ -127,9 +129,16 @@ int BenchmarkTriviaQA(GemmaEnv& env, const Path& json_file,
 }  // namespace gcpp
 
 int main(int argc, char** argv) {
-  gcpp::GemmaEnv env(argc, argv);
-  gcpp::BenchmarkArgs benchmark_args(argc, argv);
+  gcpp::ConsumedArgs consumed(argc, argv);
+  gcpp::GemmaArgs args(argc, argv, consumed);
+  gcpp::BenchmarkArgs benchmark_args(argc, argv, consumed);
+  if (gcpp::HasHelp(argc, argv)) {
+    args.Help();
+    return 0;
+  }
+  consumed.AbortIfUnconsumed();
 
+  gcpp::GemmaEnv env(args);
   if (!benchmark_args.summarize_text.Empty()) {
     return BenchmarkSummary(env, benchmark_args.summarize_text);
   } else if (!benchmark_args.cross_entropy.Empty()) {
diff --git a/evals/benchmark_helper.cc b/evals/benchmark_helper.cc
index a495dea..30d364f 100644
--- a/evals/benchmark_helper.cc
+++ b/evals/benchmark_helper.cc
@@ -36,30 +36,29 @@
 
 namespace gcpp {
 
-GemmaEnv::GemmaEnv(const LoaderArgs& loader, const ThreadingArgs& threading,
-                   const InferenceArgs& inference)
-    : ctx_(threading), env_(ctx_), gemma_(loader, inference, ctx_) {
+GemmaEnv::GemmaEnv(const GemmaArgs& args)
+    : initializer_value_(gcpp::InternalInit()),
+      ctx_(args.threading),
+      env_(ctx_),
+      gemma_(args, ctx_) {
   const ModelConfig& config = gemma_.Config();
   // Only allocate one for starters because GenerateBatch might not be called.
-  kv_caches_.push_back(KVCache(config, inference, ctx_.allocator));
+  kv_caches_.push_back(KVCache(config, args.inference, ctx_.allocator));
 
-  if (inference.verbosity >= 2) {
-    ShowConfig(loader, threading, inference, config, gemma_.WeightReadMode(),
-               ctx_);
+  if (args.inference.verbosity >= 2) {
+    ShowConfig(args, config, gemma_.WeightReadMode(), ctx_);
   }
+  if (args.inference.verbosity >= 3) env_.print_best = true;
+  if (args.inference.verbosity >= 4) env_.print_config = true;
 
   runtime_config_ = {
-      .max_generated_tokens = inference.max_generated_tokens,
-      .temperature = inference.temperature,
-      .verbosity = inference.verbosity,
+      .max_generated_tokens = args.inference.max_generated_tokens,
+      .temperature = args.inference.temperature,
+      .verbosity = args.inference.verbosity,
   };
-  inference.CopyTo(runtime_config_);
+  args.inference.CopyTo(runtime_config_);
 }
 
-GemmaEnv::GemmaEnv(int argc, char** argv)
-    : GemmaEnv(LoaderArgs(argc, argv), ThreadingArgs(argc, argv),
-               InferenceArgs(argc, argv)) {}
-
 QueryResult GemmaEnv::QueryModel(const std::vector<int>& tokens) {
   QueryResult result;
 
@@ -229,19 +228,19 @@ static constexpr const char* CompiledConfig() {
   }
 }
 
-void ShowConfig(const LoaderArgs& loader, const ThreadingArgs& threading,
-                const InferenceArgs& inference, const ModelConfig& config,
+void ShowConfig(const GemmaArgs& args, const ModelConfig& config,
                 const WeightsPtrs::Mode weight_read_mode,
                 const ThreadingContext& ctx) {
-  threading.Print(inference.verbosity);
-  loader.Print(inference.verbosity);
-  inference.Print(inference.verbosity);
-  fprintf(
-      stderr, "Model                         : %s, to_bf16 %d, mmap %d => %s\n",
-      config.Specifier().c_str(), static_cast<int>(loader.to_bf16),
-      static_cast<int>(loader.map), WeightsPtrs::ToString(weight_read_mode));
+  args.threading.Print(args.inference.verbosity);
+  args.loader.Print(args.inference.verbosity);
+  args.inference.Print(args.inference.verbosity);
+  fprintf(stderr,
+          "Model                         : %s, to_bf16 %d, mmap %d => %s\n",
+          config.Specifier().c_str(), static_cast<int>(args.loader.to_bf16),
+          static_cast<int>(args.loader.map),
+          WeightsPtrs::ToString(weight_read_mode));
 
-  if (inference.verbosity >= 2) {
+  if (args.inference.verbosity >= 2) {
     time_t now = time(nullptr);
     char* dt = ctime(&now);  // NOLINT
     char cpu100[100] = "unknown";
@@ -254,7 +253,7 @@ void ShowConfig(const LoaderArgs& loader, const ThreadingArgs& threading,
             "Instruction set               : %s (%zu bits)\n"
             "Compiled config               : %s, profiler %d\n"
             "Memory MiB                    : %4zu\n",
-            dt, cpu100, static_cast<int>(threading.bind),
+            dt, cpu100, static_cast<int>(args.threading.bind),
             ctx.topology.TopologyString(), ctx.pools.PinString(),
             CacheString().c_str(), hwy::TargetName(hwy::DispatchedTarget()),
             ctx.cache_info.VectorBytes() * 8, CompiledConfig(),
@@ -262,22 +261,4 @@ void ShowConfig(const LoaderArgs& loader, const ThreadingArgs& threading,
   }
 }
 
-void ShowHelp(const LoaderArgs& loader, const ThreadingArgs& threading,
-              const InferenceArgs& inference) {
-  std::cerr
-      << "\n\ngemma.cpp : a lightweight, standalone C++ inference engine\n"
-         "==========================================================\n\n"
-         "To run with pre-2025 weights, specify --tokenizer and --weights.\n"
-         "With the single-file weights format, specify just --weights.\n";
-  std::cerr << "\n*Example Usage*\n\n./gemma --tokenizer tokenizer.spm "
-               "--weights gemma2-2b-it-sfp.sbs\n";
-  std::cerr << "\n*Model Loading Arguments*\n\n";
-  loader.Help();
-  std::cerr << "\n*Threading Arguments*\n\n";
-  threading.Help();
-  std::cerr << "\n*Inference Arguments*\n\n";
-  inference.Help();
-  std::cerr << "\n";
-}
-
 }  // namespace gcpp
diff --git a/evals/benchmark_helper.h b/evals/benchmark_helper.h
index 2380dbf..203174c 100644
--- a/evals/benchmark_helper.h
+++ b/evals/benchmark_helper.h
@@ -23,7 +23,7 @@
 
 #include "gemma/configs.h"
 #include "gemma/gemma.h"
-#include "gemma/gemma_args.h"
+#include "gemma/gemma_args.h"  // IWYU pragma: export
 #include "gemma/tokenizer.h"  // WrapAndTokenize
 #include "ops/matmul.h"
 #include "util/threading_context.h"
@@ -50,10 +50,8 @@ struct QueryResultAndMetrics {
 // Convenience class to load a model and run inference.
 class GemmaEnv {
  public:
-  // Calls the other constructor with *Args arguments initialized from argv.
-  GemmaEnv(int argc, char** argv);
-  GemmaEnv(const LoaderArgs& loader, const ThreadingArgs& threading,
-           const InferenceArgs& inference);
+  explicit GemmaEnv(const GemmaArgs& args);
+
   MatMulEnv& Env() { return env_; }
 
   size_t MaxGeneratedTokens() const {
@@ -125,6 +123,8 @@ class GemmaEnv {
   MatMulEnv& MutableEnv() { return env_; }
 
  private:
+  // This is used to ensure that InternalInit is called before anything else.
+  int initializer_value_ = 0;
   ThreadingContext ctx_;
   MatMulEnv env_;
   Gemma gemma_;
@@ -135,12 +135,9 @@ class GemmaEnv {
 // Logs the inference speed in tokens/sec.
 void LogSpeedStats(double time_start, size_t total_tokens);
 
-void ShowConfig(const LoaderArgs& loader, const ThreadingArgs& threading,
-                const InferenceArgs& inference, const ModelConfig& config,
+void ShowConfig(const GemmaArgs& args, const ModelConfig& config,
                 WeightsPtrs::Mode weight_read_mode,
                 const ThreadingContext& ctx);
-void ShowHelp(const LoaderArgs& loader, const ThreadingArgs& threading,
-              const InferenceArgs& inference);
 
 }  // namespace gcpp
 
diff --git a/evals/benchmarks.cc b/evals/benchmarks.cc
index 3cb3d3f..f44c62b 100644
--- a/evals/benchmarks.cc
+++ b/evals/benchmarks.cc
@@ -98,7 +98,11 @@ BENCHMARK(BM_coding_prompt)
     ->UseRealTime();
 
 int main(int argc, char** argv) {
-  gcpp::GemmaEnv env(argc, argv);
+  gcpp::ConsumedArgs consumed(argc, argv);
+  gcpp::GemmaArgs args(argc, argv, consumed);
+  consumed.AbortIfUnconsumed();
+
+  gcpp::GemmaEnv env(args);
   env.SetMaxGeneratedTokens(256);
   gcpp::s_env = &env;
 
diff --git a/evals/debug_prompt.cc b/evals/debug_prompt.cc
index 66fa466..a6cf8c4 100644
--- a/evals/debug_prompt.cc
+++ b/evals/debug_prompt.cc
@@ -31,7 +31,9 @@ namespace gcpp {
 
 class PromptArgs : public ArgsBase<PromptArgs> {
  public:
-  PromptArgs(int argc, char* argv[]) { InitAndParse(argc, argv); }
+  PromptArgs(int argc, char* argv[], ConsumedArgs& consumed) {
+    InitAndParse(argc, argv, consumed);
+  }
 
   Path layers_output;  // optional
   std::string prompt;
@@ -51,11 +53,15 @@ class PromptArgs : public ArgsBase<PromptArgs> {
 };
 
 int Run(int argc, char** argv) {
-  PromptArgs prompt_args(argc, argv);
+  ConsumedArgs consumed(argc, argv);
+  const GemmaArgs args(argc, argv, consumed);
+  const PromptArgs prompt_args(argc, argv, consumed);
   AbortIfInvalidArgs(prompt_args);
+  consumed.AbortIfUnconsumed();
 
   json json_output;
-  GemmaEnv env(argc, argv);
+  GemmaEnv env(args);
+
   env.MutableConfig().layers_output =
       prompt_args.layers_output.Empty()
           ? LayersOutputFunc()
diff --git a/evals/gemma_batch_bench.cc b/evals/gemma_batch_bench.cc
index 4a6f5ea..dd9cb45 100644
--- a/evals/gemma_batch_bench.cc
+++ b/evals/gemma_batch_bench.cc
@@ -48,7 +48,7 @@ class GemmaBatchBench : public ::testing::Test {
   }
 };
 
-TEST_F(GemmaBatchBench, RandomQuestionsBatched) {
+std::vector<std::string> GenerateInputs() {
   std::vector<std::string> prompts = {
       {"Describe dynamic programming."},
       {"Explain how electric cars work."},
@@ -122,33 +122,38 @@ TEST_F(GemmaBatchBench, RandomQuestionsBatched) {
     inputs.push_back(prompts[qpos++]);
     if (qpos == prompts.size()) qpos = 0;
   }
-  s_env->SetMaxGeneratedTokens(24);
-  std::vector<std::string> responses = BatchGemmaReply(inputs);
-  for (size_t i = 0; i < HWY_MIN(hwy::Unpredictable1() * 3, responses.size());
-       ++i) {
-    fprintf(stderr, "Batch answer %zu '%s'\n\n", i, responses[i].c_str());
-  }
-
-  PROFILER_PRINT_RESULTS();
-
-  // Run again: prefill will be faster due to autotuning. Fewer decode steps
-  // because those are already fast.
-  s_env->SetMaxGeneratedTokens(2);
-  responses = BatchGemmaReply(inputs);
-
-  PROFILER_PRINT_RESULTS();
+  return inputs;
 }
+
+TEST_F(GemmaBatchBench, RandomQuestionsBatched) {
+  s_env->SetMaxGeneratedTokens(12);
+  const std::vector<std::string> inputs = GenerateInputs();
+
+  // Run multiple times so that auto-tuning is closer to complete.
+  for (size_t rep = 0; rep < 4; ++rep) {
+    std::vector<std::string> responses = BatchGemmaReply(inputs);
+    for (size_t i = 0; i < HWY_MIN(hwy::Unpredictable1() * 3, responses.size());
+         ++i) {
+      fprintf(stderr, "Rep %zu batch answer %zu '%s'\n\n", rep, i,
+              responses[i].c_str());
+    }
+    PROFILER_PRINT_RESULTS();
+  }
+}
+
 }  // namespace
 }  // namespace gcpp
 
 int main(int argc, char** argv) {
   fprintf(stderr, "GemmaEnv setup..\n");
-  gcpp::GemmaEnv env(argc, argv);
+  gcpp::ConsumedArgs consumed(argc, argv);
+  gcpp::GemmaArgs args(argc, argv, consumed);
+  consumed.AbortIfUnconsumed();
+
+  gcpp::GemmaEnv env(args);
   gcpp::s_env = &env;
 
   testing::InitGoogleTest(&argc, argv);
 
   return RUN_ALL_TESTS();
 }
-
-
diff --git a/evals/gemma_test.cc b/evals/gemma_test.cc
index 04eb20a..a581561 100644
--- a/evals/gemma_test.cc
+++ b/evals/gemma_test.cc
@@ -22,7 +22,6 @@
 
 #include "evals/benchmark_helper.h"
 #include "gemma/configs.h"
-#include "io/io.h"
 #include "hwy/base.h"
 #include "hwy/tests/hwy_gtest.h"
 
@@ -42,7 +41,11 @@ class GemmaTest : public ::testing::Test {
   // Requires argc/argv, hence do not use `SetUpTestSuite`.
   static void InitEnv(int argc, char** argv) {
     HWY_ASSERT(s_env == nullptr);  // Should only be called once.
-    s_env = new GemmaEnv(argc, argv);
+    ConsumedArgs consumed(argc, argv);
+    GemmaArgs args(argc, argv, consumed);
+    consumed.AbortIfUnconsumed();
+
+    s_env = new GemmaEnv(args);
     const gcpp::ModelConfig& config = s_env->GetGemma()->Config();
     fprintf(stderr, "Using %s\n", config.Specifier().c_str());
   }
@@ -130,7 +133,7 @@ TEST_F(GemmaTest, Multiturn) {
   // Note: we do not rewind any <end_of_turn> tokens here. If the model
   // produced one and WrapAndTokenize() inserts another one, it will just be
   // duplicated.
-  mutable_prompt = "Please repeat all prior statements.";
+  mutable_prompt = "Please repeat what I just told you.";
   tokens = WrapAndTokenize(model->Tokenizer(), model->ChatTemplate(),
                            config.wrapping, abs_pos, mutable_prompt);
 
@@ -167,6 +170,9 @@ TEST_F(GemmaTest, CrossEntropySmall) {
     case gcpp::Model::GEMMA2_27B:
       EXPECT_NEAR(entropy, 1.30f, 0.02f);
       break;
+    case gcpp::Model::GEMMA3_270M:
+      EXPECT_NEAR(entropy, 1.41f, 0.02f);
+      break;
     default:
       FAIL() << "no entropy expectation for this model";
       break;
@@ -178,7 +184,6 @@ TEST_F(GemmaTest, CrossEntropySmall) {
 
 int main(int argc, char** argv) {
   testing::InitGoogleTest(&argc, argv);
-  gcpp::InternalInit();
   gcpp::GemmaTest::InitEnv(argc, argv);
   int ret = RUN_ALL_TESTS();
   gcpp::GemmaTest::DeleteEnv();
diff --git a/evals/run_mmlu.cc b/evals/run_mmlu.cc
index 04a6e00..c6ce972 100644
--- a/evals/run_mmlu.cc
+++ b/evals/run_mmlu.cc
@@ -31,7 +31,9 @@
 namespace gcpp {
 
 struct JsonArgs : public ArgsBase<JsonArgs> {
-  JsonArgs(int argc, char* argv[]) { InitAndParse(argc, argv); }
+  JsonArgs(int argc, char* argv[], ConsumedArgs& consumed) {
+    InitAndParse(argc, argv, consumed);
+  }
 
   Path input;
 
@@ -151,10 +153,14 @@ void Run(GemmaEnv& env, JsonArgs& json) {
 int main(int argc, char** argv) {
   {
     PROFILER_ZONE("Startup.all");
-    gcpp::GemmaEnv env(argc, argv);
-    gcpp::JsonArgs json(argc, argv);
-    gcpp::AbortIfInvalidArgs(json);
-    gcpp::Run(env, json);
+    gcpp::ConsumedArgs consumed(argc, argv);
+    gcpp::GemmaArgs args(argc, argv, consumed);
+    gcpp::JsonArgs json_args(argc, argv, consumed);
+    gcpp::AbortIfInvalidArgs(json_args);
+    consumed.AbortIfUnconsumed();
+
+    gcpp::GemmaEnv env(args);
+    gcpp::Run(env, json_args);
   }
   PROFILER_PRINT_RESULTS();  // Must call outside the zone above.
   return 0;
diff --git a/examples/hello_world/CMakeLists.txt b/examples/hello_world/CMakeLists.txt
index 1ff827e..2fd94b4 100644
--- a/examples/hello_world/CMakeLists.txt
+++ b/examples/hello_world/CMakeLists.txt
@@ -18,7 +18,7 @@ set(CMAKE_CXX_STANDARD 17)
 set(CMAKE_CXX_STANDARD_REQUIRED ON)
 
 include(FetchContent)
-FetchContent_Declare(highway GIT_REPOSITORY https://github.com/google/highway.git GIT_TAG 2a16a50ff61071bb25ddef0ce35d92b0e2b9c579)
+FetchContent_Declare(highway GIT_REPOSITORY https://github.com/google/highway.git GIT_TAG 3b680cde3a556bead9cc23c8f595d07a44d5a0d5)
 FetchContent_MakeAvailable(highway)
 FetchContent_Declare(sentencepiece GIT_REPOSITORY https://github.com/google/sentencepiece GIT_TAG 9045b2f60fa2b323dfac0eaef8fc17565036f9f9)
 FetchContent_MakeAvailable(sentencepiece)
diff --git a/examples/hello_world/run.cc b/examples/hello_world/run.cc
index f67324d..9cd8b0e 100644
--- a/examples/hello_world/run.cc
+++ b/examples/hello_world/run.cc
@@ -24,20 +24,20 @@
 #include <vector>
 
 #include "gemma/gemma.h"
-#include "gemma/gemma_args.h"  // LoaderArgs
+#include "gemma/gemma_args.h"  // GemmaArgs
 #include "gemma/tokenizer.h"
 #include "util/args.h"
 #include "util/threading_context.h"
 #include "hwy/base.h"
 
 int main(int argc, char** argv) {
-  gcpp::LoaderArgs loader(argc, argv);
-  gcpp::ThreadingArgs threading(argc, argv);
-  gcpp::InferenceArgs inference(argc, argv);
+  gcpp::ConsumedArgs consumed(argc, argv);
+  gcpp::GemmaArgs args(argc, argv, consumed);
   if (gcpp::HasHelp(argc, argv)) {
-    loader.Help();
+    args.Help();
     return 0;
   }
+  consumed.AbortIfUnconsumed();
 
   // Demonstrate constrained decoding by never outputting certain tokens.
   std::set<int> reject_tokens;
@@ -49,10 +49,10 @@ int main(int argc, char** argv) {
   }
 
   // Instantiate model and KV Cache
-  gcpp::ThreadingContext ctx(threading);
+  gcpp::ThreadingContext ctx(args.threading);
   gcpp::MatMulEnv env(ctx);
-  gcpp::Gemma gemma(loader, inference, ctx);
-  gcpp::KVCache kv_cache(gemma.Config(), inference, ctx.allocator);
+  gcpp::Gemma gemma(args, ctx);
+  gcpp::KVCache kv_cache(gemma.Config(), args.inference, ctx.allocator);
   size_t generated = 0;
 
   // Tokenize instructions.
diff --git a/examples/simplified_gemma/CMakeLists.txt b/examples/simplified_gemma/CMakeLists.txt
index 2fd4228..ca2e405 100644
--- a/examples/simplified_gemma/CMakeLists.txt
+++ b/examples/simplified_gemma/CMakeLists.txt
@@ -18,7 +18,7 @@ set(CMAKE_CXX_STANDARD 17)
 set(CMAKE_CXX_STANDARD_REQUIRED ON)
 
 include(FetchContent)
-FetchContent_Declare(highway GIT_REPOSITORY https://github.com/google/highway.git GIT_TAG 2a16a50ff61071bb25ddef0ce35d92b0e2b9c579)
+FetchContent_Declare(highway GIT_REPOSITORY https://github.com/google/highway.git GIT_TAG 3b680cde3a556bead9cc23c8f595d07a44d5a0d5)
 FetchContent_MakeAvailable(highway)
 FetchContent_Declare(sentencepiece GIT_REPOSITORY https://github.com/google/sentencepiece GIT_TAG 53de76561cfc149d3c01037f0595669ad32a5e7c)
 FetchContent_MakeAvailable(sentencepiece)
diff --git a/examples/simplified_gemma/gemma.hpp b/examples/simplified_gemma/gemma.hpp
index e5bb1d8..4a69923 100644
--- a/examples/simplified_gemma/gemma.hpp
+++ b/examples/simplified_gemma/gemma.hpp
@@ -23,7 +23,7 @@
 #include <vector>
 
 #include "third_party/gemma_cpp/gemma/gemma.h"
-#include "third_party/gemma_cpp/gemma/gemma_args.h"  // LoaderArgs
+#include "third_party/gemma_cpp/gemma/gemma_args.h"  // GemmaArgs
 #include "third_party/gemma_cpp/gemma/tokenizer.h"
 #include "third_party/gemma_cpp/ops/matmul.h"
 #include "third_party/gemma_cpp/util/threading_context.h"
@@ -31,18 +31,11 @@
 
 class SimplifiedGemma {
  public:
-  SimplifiedGemma(const gcpp::LoaderArgs& loader,
-                  const gcpp::ThreadingArgs& threading = gcpp::ThreadingArgs(),
-                  const gcpp::InferenceArgs& inference = gcpp::InferenceArgs())
-      : ctx_(threading),
+  SimplifiedGemma(const gcpp::GemmaArgs& args)
+      : ctx_(args.threading),
         env_(ctx_),
-        gemma_(loader, inference, ctx_),
-        kv_cache_(gemma_.Config(), inference, ctx_.allocator) {}
-
-  SimplifiedGemma(int argc, char** argv)
-      : SimplifiedGemma(gcpp::LoaderArgs(argc, argv),
-                        gcpp::ThreadingArgs(argc, argv),
-                        gcpp::InferenceArgs(argc, argv)) {}
+        gemma_(args, ctx_),
+        kv_cache_(gemma_.Config(), args.inference, ctx_.allocator) {}
 
   void Generate(std::string& prompt, size_t max_generated_tokens = 1024,
                 float temperature = 0.7,
diff --git a/examples/simplified_gemma/run.cc b/examples/simplified_gemma/run.cc
index b7af134..58356d2 100644
--- a/examples/simplified_gemma/run.cc
+++ b/examples/simplified_gemma/run.cc
@@ -18,28 +18,18 @@
 #include <string>
 
 #include "third_party/gemma_cpp/examples/simplified_gemma/gemma.hpp"
-#include "gemma/gemma_args.h"  // LoaderArgs
+#include "gemma/gemma_args.h"
 
 int main(int argc, char** argv) {
-  // Standard usage: LoaderArgs takes argc and argv as input, then parses
-  // necessary flags.
-  gcpp::LoaderArgs loader(argc, argv);
+  // Sets arguments from argc and argv. Note that you can instead pass in
+  // LoaderArgs, ThreadingArgs, and InferenceArgs directly.
+  gcpp::ConsumedArgs consumed(argc, argv);
+  gcpp::GemmaArgs args(argc, argv, consumed);
+  consumed.AbortIfUnconsumed();
 
-  // Optional: LoaderArgs can also take tokenizer and weights paths directly.
-  //
-  // gcpp::LoaderArgs loader("/path/to/tokenizer", "/path/to/weights",
-  // "model_identifier");
-
-  // Optional: ThreadingArgs and InferenceArgs can be passed in as well. If not
-  // specified, default values will be used.
-  //
-  // gcpp::InferenceArgs inference(argc, argv);
-  // gcpp::ThreadingArgs threading(argc, argv);
-  // SimplifiedGemma gemma(loader, threading, inference);
-
-  SimplifiedGemma gemma(loader);
+  SimplifiedGemma gemma(args);
   std::string prompt = "Write a greeting to the world.";
   gemma.Generate(prompt, 256, 0.6);
 
   return 0;
-}
\ No newline at end of file
+}
diff --git a/gemma/activations.h b/gemma/activations.h
index f474c84..adb6d02 100644
--- a/gemma/activations.h
+++ b/gemma/activations.h
@@ -23,44 +23,54 @@
 #include <atomic>
 #include <vector>
 
-#include "gemma/configs.h"  // ModelConfig
-#include "ops/ops.h"        // CreateInvTimescale
-#include "util/basics.h"    // BF16
-#include "util/mat.h"       // MatStorageT
+#include "gemma/configs.h"     // ModelConfig
+#include "gemma/gemma_args.h"  // AttentionImpl
+#include "gemma/kv_cache.h"
+#include "gemma/tensor_stats.h"
+#include "ops/ops.h"      // CreateInvTimescale
+#include "util/basics.h"  // BF16
+#include "util/mat.h"     // MatStorageT
 #include "util/threading_context.h"
 
 namespace gcpp {
 
-struct AttentionActivations {
-  // Returns the scale value to use for the query in the attention computation.
-  // Also called by ops_test.
-  static inline float ChooseQueryScale(const ModelConfig& config) {
-    const LayerConfig& layer_config = config.layer_configs[0];
-    if (config.query_scale == QueryScaleType::SqrtModelDimDivNumHeads)
-      return 1.0f /
-             sqrtf(static_cast<float>(config.model_dim / layer_config.heads));
-    // QueryScaleType::SqrtKeySize
-    return 1.0f / sqrtf(static_cast<float>(layer_config.qkv_dim));
-  }
+// Returns the scale value to use for the query in the attention computation.
+// Also called by ops_test.
+static inline float ChooseQueryScale(const ModelConfig& config) {
+  const LayerConfig& layer_config = config.layer_configs[0];
+  if (config.query_scale == QueryScaleType::SqrtModelDimDivNumHeads)
+    return 1.0f /
+           sqrtf(static_cast<float>(config.model_dim / layer_config.heads));
+  // QueryScaleType::SqrtKeySize
+  return 1.0f / sqrtf(static_cast<float>(layer_config.qkv_dim));
+}
 
+struct AttentionActivations {
   AttentionActivations(
       const ModelConfig& config, const LayerConfig& layer_config,
-      size_t batch_size, size_t seq_len, const Allocator& allocator,
+      size_t batch_size, size_t seq_len, const RuntimeConfig& runtime_config,
+      const Allocator& allocator,
       std::vector<hwy::AlignedFreeUniquePtr<uint8_t*[]>>& row_ptrs)
-      : config(config),
-
-        // `vocab_size == 0` means it is for Vit part, VitAttention is still MHA
-        // and does not use an external KV cache.
+      :  // `vocab_size == 0` means it is for Vit part, VitAttention is still
+         // MHA and does not use an external KV cache.
         q(MatFactory("q", batch_size,
                      config.vocab_size == 0
                          ? layer_config.heads * 3 * layer_config.qkv_dim
                          : layer_config.heads * layer_config.qkv_dim,
                      allocator)),
+        q_bf(MatFactory("q_bf", batch_size,
+                        config.vocab_size == 0
+                            ? layer_config.heads * 3 * layer_config.qkv_dim
+                            : layer_config.heads * layer_config.qkv_dim,
+                        allocator)),
         q_T(MatFactory("q_T", layer_config.qkv_dim,
                        config.vocab_size == 0
                            ? batch_size * layer_config.heads * 3
                            : batch_size * layer_config.heads,
                        allocator)),
+        vit_Q(MatFactory("Q2", batch_size, layer_config.qkv_dim, allocator)),
+        vit_K(MatFactory("K2", seq_len, layer_config.qkv_dim, allocator)),
+        vit_C(MatFactory("C2", batch_size, seq_len, allocator)),
         pre_att_rms_out(MatFactory("pre_att_rms_out", batch_size,
                                    config.model_dim, allocator)),
         att(MatFactory("att", batch_size, layer_config.heads * seq_len,
@@ -68,6 +78,10 @@ struct AttentionActivations {
         att_out(MatFactory("att_out", batch_size,
                            layer_config.heads * layer_config.qkv_dim,
                            allocator)),
+        softmax_max(MatFactory("softmax_max", batch_size, layer_config.heads,
+                               allocator)),
+        softmax_d(
+            MatFactory("softmax_d", batch_size, layer_config.heads, allocator)),
         att_sums(
             MatFactory("att_sums", batch_size, config.model_dim, allocator)),
 
@@ -76,11 +90,7 @@ struct AttentionActivations {
                                layer_config.post_qk == PostQKType::HalfRope)),
         inv_timescale_global(CreateInvTimescale(
             allocator, layer_config.qkv_dim,
-            layer_config.post_qk == PostQKType::HalfRope, 1000000.0)),
-
-        div_seq_len(static_cast<uint32_t>(seq_len)),
-        div_heads(static_cast<uint32_t>(layer_config.heads)),
-        query_scale(ChooseQueryScale(config)) {
+            layer_config.post_qk == PostQKType::HalfRope, 1000000.0)) {
     // Batch size can be 0 in experimental code so do not assert.
     if (batch_size == 0) {
       static std::atomic_flag warned = ATOMIC_FLAG_INIT;
@@ -94,44 +104,153 @@ struct AttentionActivations {
     // If we forget any MatMul outputs here, debug builds print a warning but
     // fill them in each MatMul call.
     q.AllocateAndAttachRowPtrs(row_ptrs);
+    q_bf.AllocateAndAttachRowPtrs(row_ptrs);
     q_T.AllocateAndAttachRowPtrs(row_ptrs);
+    vit_C.AllocateAndAttachRowPtrs(row_ptrs);
     att_sums.AllocateAndAttachRowPtrs(row_ptrs);
   }
 
   void SetBatchSize(size_t batch_size) {
     q.OverrideRows(batch_size);
+    q_bf.OverrideRows(batch_size);
     // q_T rows are always qkv_dim!
 
+    vit_Q.OverrideRows(batch_size);
+    // vit_K stays seq_len!
+    vit_C.OverrideRows(batch_size);
+
     pre_att_rms_out.OverrideRows(batch_size);
     att.OverrideRows(batch_size);
     att_out.OverrideRows(batch_size);
+    softmax_max.OverrideRows(batch_size);
+    softmax_d.OverrideRows(batch_size);
     att_sums.OverrideRows(batch_size);
+
+    // `inv_timescale*` are not batched.
   }
 
-  const ModelConfig& config;
-
   MatStorageT<float> q;  // query
-  MatStorageT<float> q_T;  // Transposed to maximize attention speed.
+  MatStorageT<BF16> q_bf;
+  MatStorageT<BF16> q_T;  // Transposed to maximize attention speed.
+
+  MatStorageT<float> vit_Q;
+  MatStorageT<float> vit_K;
+  MatStorageT<float> vit_C;
 
   MatStorageT<float> pre_att_rms_out;
-  MatStorageT<float> att;      // attention vector
-  MatStorageT<float> att_out;  // attention output
+  MatStorageT<float> att;          // attention vector
+  MatStorageT<float> att_out;      // attention output
+  MatStorageT<float> softmax_max;  // see OnlineSoftmaxState
+  MatStorageT<float> softmax_d;    // see OnlineSoftmaxState
   // Accumulation of attention outputs over heads
   MatStorageT<BF16> att_sums;
 
   // Rope
   MatStorageT<float> inv_timescale;
   MatStorageT<float> inv_timescale_global;
+};
 
+// A non-owning view of AttentionActivations.
+struct AttentionActivationsPtrs {
+  AttentionActivationsPtrs(const ModelConfig& config, size_t seq_len)
+      : config(config),
+        div_seq_len(static_cast<uint32_t>(seq_len)),
+        div_heads(static_cast<uint32_t>(config.layer_configs[0].heads)),
+        query_scale(ChooseQueryScale(config)) {}
+
+  AttentionActivationsPtrs(const ModelConfig& config, size_t seq_len,
+                           const AttentionActivations& activations)
+      : AttentionActivationsPtrs(config, seq_len) {
+    q = activations.q;
+    q_bf = activations.q_bf;
+    q_T = activations.q_T;
+    vit_Q = activations.vit_Q;
+    vit_K = activations.vit_K;
+    vit_C = activations.vit_C;
+    pre_att_rms_out = activations.pre_att_rms_out;
+    att = activations.att;
+    att_out = activations.att_out;
+    softmax_max = activations.softmax_max;
+    softmax_d = activations.softmax_d;
+    att_sums = activations.att_sums;
+    inv_timescale = activations.inv_timescale;
+    inv_timescale_global = activations.inv_timescale_global;
+  }
+
+  void SetBatchSize(size_t batch_size) {
+    q.OverrideRows(batch_size);
+    q_bf.OverrideRows(batch_size);
+    // q_T rows are always qkv_dim!
+
+    vit_Q.OverrideRows(batch_size);
+    // vit_K stays seq_len!
+    vit_C.OverrideRows(batch_size);
+
+    pre_att_rms_out.OverrideRows(batch_size);
+    att.OverrideRows(batch_size);
+    att_out.OverrideRows(batch_size);
+    softmax_max.OverrideRows(batch_size);
+    softmax_d.OverrideRows(batch_size);
+    att_sums.OverrideRows(batch_size);
+    // `inv_timescale*` are not batched.
+  }
+
+  size_t SeqLen() const {
+    return static_cast<size_t>(div_seq_len.GetDivisor());
+  }
+
+  const ModelConfig& config;
+
+  // For the matrices below, the batch_size dimension is really qbatch.Size() *
+  // token_batch_size, but in all known uses, one of those is 1.  Specifically,
+  // during PrefillTBatch, it is prompt length (up to some max batch size)
+  // and otherwise it's qbatch.Size().
+
+  // Query matrix of size batch_size x (q_heads * qkv_dim).
+  MatPtrT<float> q;
+  // Query matrix of size batch_size x (q_heads * qkv_dim).
+  MatPtrT<BF16> q_bf;
+  // Transposed query matrix for faster Q*K^T.
+  MatPtrT<BF16> q_T;
+
+  MatPtrT<float> vit_Q;
+  MatPtrT<float> vit_K;
+  MatPtrT<float> vit_C;
+
+  // Output of RMSNorm before attention, size batch_size x model_dim.
+  MatPtrT<float> pre_att_rms_out;
+  // Attention scores computed from Q*K^T, size batch_size x (q_heads *
+  // seq_len).
+  MatPtrT<float> att;
+  // Attention output computed from att * V, size batch_size x (q_heads *
+  // qkv_dim).
+  MatPtrT<float> att_out;
+  // The maximum logit value encountered when computing att_out from att,
+  // size batch_size x q_heads . See OnlineSoftmaxState for details.
+  // WARNING: Only filled in for AttentionImpl::kOld.
+  MatPtrT<float> softmax_max;
+  // The sum of scaled exponentials when computing att_out from att,
+  // size batch_size x q_heads . See OnlineSoftmaxState for details.
+  // WARNING: Only filled in for AttentionImpl::kOld.
+  MatPtrT<float> softmax_d;
+  // Accumulation of attention outputs over heads, size batch_size x
+  // model_dim.
+  MatPtrT<BF16> att_sums;
+  // Inverse timescales for RoPE computation.
+  MatPtrT<float> inv_timescale;
+  // Inverse timescales for global RoPE computation.
+  MatPtrT<float> inv_timescale_global;
+  // Divisor for faster division by sequence length.
   hwy::Divisor div_seq_len;
-  // Unfortunately, some models have had non-power-of-two heads.
+  // Divisor for faster division by number of heads.
   hwy::Divisor div_heads;
+  // Query scaling factor for attention computation.
   float query_scale;
 };
 
 struct Activations {
-  Activations(const ModelConfig& config, size_t batch_size, size_t seq_len,
-              ThreadingContext& ctx,
+  Activations(const RuntimeConfig& runtime_config, const ModelConfig& config,
+              size_t batch_size, size_t seq_len, ThreadingContext& ctx,
               std::vector<hwy::AlignedFreeUniquePtr<uint8_t*[]>>& row_ptrs)
       : layer_config(config.layer_configs[0]),
 
@@ -150,8 +269,18 @@ struct Activations {
         ffw_out(
             MatFactory("ffw_out", batch_size, config.model_dim, ctx.allocator)),
 
-        attention(config, layer_config, batch_size, seq_len, ctx.allocator,
-                  row_ptrs) {
+        max_workers(ctx.pools.MaxWorkers()),
+        s_ffw_in(config.num_layers, max_workers),
+        s_ffw_hidden(config.num_layers, max_workers),
+        s_ffw_out(config.num_layers, max_workers),
+
+        s_w_gating_einsum_w1(config.num_layers, max_workers),
+        s_w_gating_einsum_w2(config.num_layers, max_workers),
+        s_w_linear_w(config.num_layers, max_workers),
+        attention_impl(runtime_config.attention_impl),
+        attention_storage(config, layer_config, batch_size, seq_len,
+                          runtime_config, ctx.allocator, row_ptrs),
+        attention(config, seq_len, attention_storage) {
     HWY_ASSERT(batch_size != 0);
 
     // For MatMul outputs, precompute their row pointers.
@@ -167,6 +296,12 @@ struct Activations {
     // Note that BindC on any MatMul output considerably slows down Prefill.
   }
 
+  ~Activations() {
+    s_ffw_in.ReduceAndPrint("ffw_in");
+    s_ffw_hidden.ReduceAndPrint("ffw_hidden");
+    s_ffw_out.ReduceAndPrint("ffw_out");
+  }
+
   // Negligible CPU time.
   void SetBatchSize(size_t batch_size) {
     x.OverrideRows(batch_size);
@@ -179,12 +314,15 @@ struct Activations {
     C2.OverrideRows(batch_size);
     ffw_out.OverrideRows(batch_size);
 
+    attention_storage.SetBatchSize(batch_size);
+    // `AttentionActivationsPtrs` holds `MatPtrT` which also require updating;
+    // their row override is not updated when the underlying storage changes.
     attention.SetBatchSize(batch_size);
   }
 
   const LayerConfig& layer_config;
 
-  MatStorageT<float> x;  // input
+  MatStorageT<float> x;    // input
   MatStorageT<BF16> x_bf;  // output of final RMSNorm, input to EmbeddingMatmul
   MatStorageT<float> logits;      // TODO: BF16 after Softmax supports that.
   MatStorageT<uint32_t> sampled;  // batch_size x 3 (padded)
@@ -195,7 +333,19 @@ struct Activations {
   MatStorageT<BF16> C2;
   MatStorageT<float> ffw_out;
 
-  AttentionActivations attention;
+  const size_t max_workers;
+  TensorStats s_ffw_in;
+  TensorStats s_ffw_hidden;  // after Activation+gating
+  TensorStats s_ffw_out;
+
+  TensorStats s_w_gating_einsum_w1;
+  TensorStats s_w_gating_einsum_w2;
+  TensorStats s_w_linear_w;
+
+  AttentionImpl attention_impl;
+
+  AttentionActivations attention_storage;
+  AttentionActivationsPtrs attention;
 };
 
 }  // namespace gcpp
diff --git a/gemma/api_client.cc b/gemma/api_client.cc
index 1f64d96..e6ce191 100644
--- a/gemma/api_client.cc
+++ b/gemma/api_client.cc
@@ -15,18 +15,22 @@
 
 // Test client for API server
 
-#include <iostream>
-#include <string>
-#include <sstream>
+#include <stdio.h>
+
 #include <cstdlib>
 #include <cstring>
+#include <iostream>
+#include <sstream>
+#include <string>
 
 #include "httplib.h"
-#include "nlohmann/json.hpp"
 #include "gemma/gemma_args.h"
+#include "nlohmann/json.hpp"
 
 using json = nlohmann::json;
 
+namespace gcpp {
+
 // ANSI color codes
 const std::string RESET = "\033[0m";
 const std::string BOLD = "\033[1m";
@@ -37,9 +41,15 @@ const std::string YELLOW = "\033[33m";
 const std::string RED = "\033[31m";
 
 class APIClient {
-public:
-  APIClient(const std::string& host, int port, const std::string& api_key = "", const std::string& model = "gemma3-4b") 
-    : host_(host), port_(port), api_key_(api_key), model_(model), use_https_(port == 443), interactive_mode_(false) {
+ public:
+  APIClient(const std::string& host, int port, const std::string& api_key = "",
+            const std::string& model = "gemma3-4b")
+      : host_(host),
+        port_(port),
+        api_key_(api_key),
+        model_(model),
+        use_https_(port == 443),
+        interactive_mode_(false) {
     if (use_https_) {
       ssl_client_ = std::make_unique<httplib::SSLClient>(host, port);
       ssl_client_->set_read_timeout(60, 0);
@@ -55,22 +65,25 @@ public:
   // Unified request processing for both public and local APIs
   json ProcessRequest(const json& request, bool stream = true) {
     bool is_public_api = !api_key_.empty();
-    
+
     std::string endpoint;
     if (is_public_api) {
-      endpoint = stream ? "/v1beta/models/gemini-2.0-flash:streamGenerateContent?alt=sse" 
-                        : "/v1beta/models/gemini-2.0-flash:generateContent";
+      endpoint =
+          stream
+              ? "/v1beta/models/gemini-2.0-flash:streamGenerateContent?alt=sse"
+              : "/v1beta/models/gemini-2.0-flash:generateContent";
     } else {
-      endpoint = stream ? "/v1beta/models/" + model_ + ":streamGenerateContent" 
+      endpoint = stream ? "/v1beta/models/" + model_ + ":streamGenerateContent"
                         : "/v1beta/models/" + model_ + ":generateContent";
     }
-    
+
     // Only show verbose output in non-interactive mode
     if (!interactive_mode_) {
-      std::cout << "\n" << BOLD << BLUE << "📤 POST " << endpoint << RESET << std::endl;
+      std::cout << "\n"
+                << BOLD << BLUE << "📤 POST " << endpoint << RESET << std::endl;
       std::cout << "Request: " << request.dump(2) << std::endl;
     }
-    
+
     if (stream) {
       return ProcessStreamingRequest(request, endpoint);
     } else {
@@ -81,21 +94,24 @@ public:
   void TestGenerateContent(const std::string& prompt, bool stream = true) {
     json request = CreateAPIRequest(prompt);
     json response = ProcessRequest(request, stream);
-    
+
     if (response.contains("error")) {
-      std::cerr << RED << "❌ Error: " << response["error"]["message"] << RESET << std::endl;
+      std::cerr << RED << "❌ Error: " << response["error"]["message"] << RESET
+                << std::endl;
     }
   }
 
   void TestListModels() {
-    std::cout << "\n" << BOLD << BLUE << "📤 GET /v1beta/models" << RESET << std::endl;
-    
+    std::cout << "\n"
+              << BOLD << BLUE << "📤 GET /v1beta/models" << RESET << std::endl;
+
     httplib::Headers headers;
     if (!api_key_.empty()) {
       headers.emplace("X-goog-api-key", api_key_);
     }
-    auto res = use_https_ ? ssl_client_->Get("/v1beta/models", headers) : client_->Get("/v1beta/models", headers);
-    
+    auto res = use_https_ ? ssl_client_->Get("/v1beta/models", headers)
+                          : client_->Get("/v1beta/models", headers);
+
     if (res && res->status == 200) {
       json response = json::parse(res->body);
       std::cout << GREEN << "✅ Available models:" << RESET << std::endl;
@@ -106,49 +122,53 @@ public:
   }
 
   void InteractiveChat() {
-    std::cout << "\n" << BOLD << CYAN << "💬 Interactive Chat Mode (with session)" << RESET << std::endl;
+    std::cout << "\n"
+              << BOLD << CYAN << "💬 Interactive Chat Mode (with session)"
+              << RESET << std::endl;
     std::cout << "Type ':gemma %q' to end.\n" << std::endl;
-    
+
     interactive_mode_ = true;
     json messages;
-    
+
     while (true) {
       std::cout << BOLD << BLUE << "You: " << RESET;
       std::string input;
       std::getline(std::cin, input);
-      
+
       if (input == ":gemma %q") {
         std::cout << BOLD << YELLOW << "👋 Goodbye!" << RESET << std::endl;
         break;
       }
-      
+
       if (input.empty()) continue;
-      
+
       // Add user message with proper role
       json user_message = {{"parts", {{{"text", input}}}}};
       if (!api_key_.empty()) {
         user_message["role"] = "user";
       }
       messages.push_back(user_message);
-      
+
       // Create request using unified logic
       json request = CreateAPIRequest("", messages);
-      
+
       std::cout << BOLD << GREEN << "Assistant: " << RESET;
-      
+
       // Use unified processing - streaming for real-time output
       json response = ProcessRequest(request, true);
-      
+
       if (response.contains("candidates") && !response["candidates"].empty()) {
         auto& candidate = response["candidates"][0];
-        if (candidate.contains("content") && candidate["content"].contains("parts")) {
+        if (candidate.contains("content") &&
+            candidate["content"].contains("parts")) {
           for (const auto& part : candidate["content"]["parts"]) {
             if (part.contains("text")) {
               std::string assistant_response = part["text"].get<std::string>();
-              
+
               // For streaming, the response is already displayed in real-time
               // Just add to message history for context
-              json assistant_message = {{"parts", {{{"text", assistant_response}}}}};
+              json assistant_message = {
+                  {"parts", {{{"text", assistant_response}}}}};
               if (!api_key_.empty()) {
                 assistant_message["role"] = "model";
               }
@@ -157,23 +177,21 @@ public:
           }
         }
       } else if (response.contains("error")) {
-        std::cerr << RED << "❌ Error: " << response["error"]["message"] << RESET << std::endl;
+        std::cerr << RED << "❌ Error: " << response["error"]["message"]
+                  << RESET << std::endl;
       }
-      
+
       std::cout << std::endl;
     }
   }
 
-private:
-  json CreateAPIRequest(const std::string& prompt, const json& messages = json::array()) {
+ private:
+  json CreateAPIRequest(const std::string& prompt,
+                        const json& messages = json::array()) {
     json request = {
-      {"generationConfig", {
-        {"temperature", 0.9},
-        {"topK", 1},
-        {"maxOutputTokens", 1024}
-      }}
-    };
-    
+        {"generationConfig",
+         {{"temperature", 0.9}, {"topK", 1}, {"maxOutputTokens", 1024}}}};
+
     if (messages.empty()) {
       // Single prompt
       json user_message = {{"parts", {{{"text", prompt}}}}};
@@ -185,44 +203,48 @@ private:
       // Use provided message history
       request["contents"] = messages;
     }
-    
+
     return request;
   }
 
-  json ProcessNonStreamingRequest(const json& request, const std::string& endpoint) {
+  json ProcessNonStreamingRequest(const json& request,
+                                  const std::string& endpoint) {
     httplib::Headers headers = {{"Content-Type", "application/json"}};
     if (!api_key_.empty()) {
       headers.emplace("X-goog-api-key", api_key_);
     }
-    
-    auto res = use_https_ ? ssl_client_->Post(endpoint, headers, request.dump(), "application/json") 
-                          : client_->Post(endpoint, headers, request.dump(), "application/json");
-    
+
+    auto res = use_https_ ? ssl_client_->Post(endpoint, headers, request.dump(),
+                                              "application/json")
+                          : client_->Post(endpoint, headers, request.dump(),
+                                          "application/json");
+
     if (res && res->status == 200) {
       json response = json::parse(res->body);
       if (!interactive_mode_) {
-        std::cout << "\n" << BOLD << GREEN << "📥 Response:" << RESET << std::endl;
+        std::cout << "\n"
+                  << BOLD << GREEN << "📥 Response:" << RESET << std::endl;
         std::cout << response.dump(2) << std::endl;
       }
       return response;
     } else {
-      json error_response = {
-        {"error", {
-          {"message", "Request failed"},
-          {"status", res ? res->status : -1}
-        }}
-      };
+      json error_response = {{"error",
+                              {{"message", "Request failed"},
+                               {"status", res ? res->status : -1}}}};
       if (res && !res->body.empty()) {
         error_response["error"]["details"] = res->body;
       }
-      std::cerr << RED << "❌ Request failed. Status: " << (res ? res->status : -1) << RESET << std::endl;
+      std::cerr << RED
+                << "❌ Request failed. Status: " << (res ? res->status : -1)
+                << RESET << std::endl;
       return error_response;
     }
   }
 
-  json ProcessStreamingRequest(const json& request, const std::string& endpoint) {
+  json ProcessStreamingRequest(const json& request,
+                               const std::string& endpoint) {
     std::string accumulated_response;
-    
+
     // Use same SSE logic for both public and local APIs
     httplib::Request req;
     req.method = "POST";
@@ -232,72 +254,73 @@ private:
       req.set_header("X-goog-api-key", api_key_);
     }
     req.body = request.dump();
-    
-    req.content_receiver = [&accumulated_response, this](const char* data, size_t data_length, uint64_t offset, uint64_t total_length) -> bool {
-        std::string chunk(data, data_length);
-        std::istringstream stream(chunk);
-        std::string line;
-        
-        while (std::getline(stream, line)) {
-          if (line.substr(0, 6) == "data: ") {
-            std::string event_data = line.substr(6);
-            
-            if (event_data == "[DONE]") {
-              if (!interactive_mode_) {
-                std::cout << "\n\n" << GREEN << "✅ Generation complete!" << RESET << std::endl;
-              }
-            } else {
-              try {
-                json event = json::parse(event_data);
-                if (event.contains("candidates") && !event["candidates"].empty()) {
-                  auto& candidate = event["candidates"][0];
-                  if (candidate.contains("content") && candidate["content"].contains("parts")) {
-                    for (const auto& part : candidate["content"]["parts"]) {
-                      if (part.contains("text")) {
-                        std::string text = part["text"].get<std::string>();
-                        std::cout << text << std::flush;
-                        accumulated_response += text;
-                      }
+
+    req.content_receiver = [&accumulated_response, this](
+                               const char* data, size_t data_length,
+                               uint64_t offset, uint64_t total_length) -> bool {
+      std::string chunk(data, data_length);
+      std::istringstream stream(chunk);
+      std::string line;
+
+      while (std::getline(stream, line)) {
+        if (line.substr(0, 6) == "data: ") {
+          std::string event_data = line.substr(6);
+
+          if (event_data == "[DONE]") {
+            if (!interactive_mode_) {
+              std::cout << "\n\n"
+                        << GREEN << "✅ Generation complete!" << RESET
+                        << std::endl;
+            }
+          } else {
+            try {
+              json event = json::parse(event_data);
+              if (event.contains("candidates") &&
+                  !event["candidates"].empty()) {
+                auto& candidate = event["candidates"][0];
+                if (candidate.contains("content") &&
+                    candidate["content"].contains("parts")) {
+                  for (const auto& part : candidate["content"]["parts"]) {
+                    if (part.contains("text")) {
+                      std::string text = part["text"].get<std::string>();
+                      std::cout << text << std::flush;
+                      accumulated_response += text;
                     }
                   }
                 }
-              } catch (const json::exception& e) {
-                // Skip parse errors
               }
+            } catch (const json::exception& e) {
+              // Skip parse errors
             }
           }
         }
-        return true;
-      };
-    
+      }
+      return true;
+    };
+
     httplib::Response res;
     httplib::Error error;
-    bool success = use_https_ ? ssl_client_->send(req, res, error) : client_->send(req, res, error);
-    
+    bool success = use_https_ ? ssl_client_->send(req, res, error)
+                              : client_->send(req, res, error);
+
     if (res.status == 200 && !accumulated_response.empty()) {
       return json{
-        {"candidates", {{
-          {"content", {
-            {"parts", {{{"text", accumulated_response}}}}
-          }}
-        }}}
-      };
+          {"candidates",
+           {{{"content", {{"parts", {{{"text", accumulated_response}}}}}}}}}};
     } else {
       json error_response = {
-        {"error", {
-          {"message", "Streaming request failed"},
-          {"status", res.status}
-        }}
-      };
+          {"error",
+           {{"message", "Streaming request failed"}, {"status", res.status}}}};
       if (!res.body.empty()) {
         error_response["error"]["details"] = res.body;
       }
-      std::cerr << RED << "❌ Streaming request failed. Status: " << res.status << RESET << std::endl;
+      std::cerr << RED << "❌ Streaming request failed. Status: " << res.status
+                << RESET << std::endl;
       return error_response;
     }
   }
 
-private:
+ private:
   std::unique_ptr<httplib::Client> client_;
   std::unique_ptr<httplib::SSLClient> ssl_client_;
   std::string host_;
@@ -308,19 +331,55 @@ private:
   bool interactive_mode_;
 };
 
+struct ClientArgs : public ArgsBase<ClientArgs> {
+  ClientArgs(int argc, char* argv[], ConsumedArgs& consumed) {
+    InitAndParse(argc, argv, consumed);
+  }
+  ClientArgs() { Init(); };
+
+  std::string host;
+  int port;
+  std::string api_key;
+  std::string model;
+  std::string prompt;
+  bool interactive;
+
+  template <class Visitor>
+  void ForEach(const Visitor& visitor) {
+    visitor(host, "host", std::string("localhost"),
+            "Server host (default: localhost)");
+    visitor(port, "port", 8080, "Server port (default: 8080)");
+    visitor(api_key, "api_key", std::string(""),
+            "Use public API with key (changes host to "
+            "generativelanguage.googleapis.com:443)");
+    visitor(model, "model", std::string("gemma3-4b"),
+            "Model name to use (default: gemma3-4b)");
+    visitor(prompt, "prompt", std::string("Hello! How are you?"),
+            "Prompt for generation (default: 'Hello! How are you?')");
+    visitor(interactive, "interactive", false,
+            "Start interactive chat mode (0 = no, 1 = yes)");
+  }
+};
+
+}  // namespace gcpp
+
 int main(int argc, char* argv[]) {
-  gcpp::ClientArgs client_args(argc, argv);
-  
+  gcpp::ConsumedArgs consumed(argc, argv);
+  gcpp::ClientArgs client_args(argc, argv, consumed);
+
   if (gcpp::HasHelp(argc, argv)) {
-    std::cout << "\nAPI Client for gemma.cpp\n";
-    std::cout << "========================\n\n";
+    fprintf(stderr,
+            "\nAPI Client for gemma.cpp\n"
+            "========================\n\n");
     client_args.Help();
-    std::cout << std::endl;
-    std::cout << "Environment Variables:" << std::endl;
-    std::cout << "  GOOGLE_API_KEY : Automatically use public Google API if set" << std::endl;
+    fprintf(stderr,
+            "\n*Environment Variables:\n"
+            "  GOOGLE_API_KEY : Automatically use public Google API if set\n");
     return 0;
   }
-  
+
+  consumed.AbortIfUnconsumed();
+
   // Check for GOOGLE_API_KEY environment variable
   const char* env_api_key = std::getenv("GOOGLE_API_KEY");
   if (env_api_key != nullptr && strlen(env_api_key) > 0) {
@@ -328,32 +387,34 @@ int main(int argc, char* argv[]) {
     client_args.host = "generativelanguage.googleapis.com";
     client_args.port = 443;
   }
-  
+
   // Handle API key override
   if (!client_args.api_key.empty()) {
     client_args.host = "generativelanguage.googleapis.com";
     client_args.port = 443;
   }
-  
-  std::cout << BOLD << YELLOW << "🚀 Testing API Server at " 
-            << client_args.host << ":" << client_args.port << RESET << std::endl;
-  
+
+  std::cout << BOLD << YELLOW << "🚀 Testing API Server at " << client_args.host
+            << ":" << client_args.port << RESET << std::endl;
+
   try {
-    APIClient client(client_args.host, client_args.port, client_args.api_key, client_args.model);
-    
+    APIClient client(client_args.host, client_args.port, client_args.api_key,
+                     client_args.model);
+
     if (client_args.interactive) {
       client.InteractiveChat();
     } else {
       client.TestListModels();
       client.TestGenerateContent(client_args.prompt, true);
     }
-    
   } catch (const std::exception& e) {
     std::cerr << RED << "❌ Error: " << e.what() << RESET << std::endl;
     std::cerr << "Make sure the API server is running:" << std::endl;
-    std::cerr << "  ./build/gemma_api_server --tokenizer <path> --weights <path>" << std::endl;
+    std::cerr
+        << "  ./build/gemma_api_server --tokenizer <path> --weights <path>"
+        << std::endl;
     return 1;
   }
-  
+
   return 0;
 }
diff --git a/gemma/api_server.cc b/gemma/api_server.cc
index f05447b..8f71043 100644
--- a/gemma/api_server.cc
+++ b/gemma/api_server.cc
@@ -15,22 +15,19 @@
 
 // HTTP API server for gemma.cpp with SSE support
 
-#include <stdio.h>
 #include <signal.h>
+#include <stdio.h>
 
-#include <iostream>
-#include <memory>
-#include <random>
-#include <string>
-#include <string_view>
-#include <vector>
-#include <thread>
 #include <atomic>
 #include <chrono>
-#include <sstream>
-#include <iomanip>
+#include <iostream>
+#include <memory>
 #include <mutex>
+#include <sstream>
+#include <string>
+#include <thread>  // NOLINT
 #include <unordered_map>
+#include <vector>
 
 // HTTP server library
 #undef CPPHTTPLIB_OPENSSL_SUPPORT
@@ -38,16 +35,12 @@
 #include "httplib.h"
 
 // JSON library
-#include "nlohmann/json.hpp"
-
-#include "compression/types.h"
 #include "gemma/gemma.h"
 #include "gemma/gemma_args.h"
-#include "gemma/tokenizer.h"
 #include "ops/matmul.h"
 #include "util/args.h"
 #include "hwy/base.h"
-#include "hwy/profiler.h"
+#include "nlohmann/json.hpp"
 
 using json = nlohmann::json;
 
@@ -90,7 +83,8 @@ struct ServerState {
     std::lock_guard<std::mutex> lock(sessions_mutex);
     auto& session = sessions[session_id];
     if (!session.kv_cache) {
-      session.kv_cache = std::make_unique<KVCache>(gemma->Config(), InferenceArgs(), env->ctx.allocator);
+      session.kv_cache = std::make_unique<KVCache>(
+          gemma->Config(), InferenceArgs(), env->ctx.allocator);
     }
     session.last_access = std::chrono::steady_clock::now();
     return session;
@@ -107,7 +101,8 @@ std::string GenerateSessionId() {
   return ss.str();
 }
 
-// Wraps messages with start_of_turn markers - handles both with and without roles
+// Wraps messages with start_of_turn markers - handles both with and without
+// roles
 std::string WrapMessagesWithTurnMarkers(const json& contents) {
   std::string prompt;
 
@@ -121,12 +116,14 @@ std::string WrapMessagesWithTurnMarkers(const json& contents) {
           std::string text = part["text"];
 
           if (role == "user") {
-            prompt += "<start_of_turn>user\n" + text + "\n<start_of_turn>model\n";
+            prompt +=
+                "<start_of_turn>user\n" + text + "\n<start_of_turn>model\n";
           } else if (role == "model") {
             prompt += text + "\n";
           } else if (role.empty()) {
             // Local format without roles - for now, treat as user input
-            prompt += "<start_of_turn>user\n" + text + "\n<start_of_turn>model\n";
+            prompt +=
+                "<start_of_turn>user\n" + text + "\n<start_of_turn>model\n";
           }
         }
       }
@@ -163,18 +160,15 @@ RuntimeConfig ParseGenerationConfig(const json& request) {
   return config;
 }
 
-// Unified response formatter - creates consistent format regardless of request type
-json CreateAPIResponse(const std::string& text, bool is_streaming_chunk = false) {
+// Unified response formatter - creates consistent format regardless of request
+// type
+json CreateAPIResponse(const std::string& text,
+                       bool is_streaming_chunk = false) {
   json response = {
-    {"candidates", {{
-      {"content", {
-        {"parts", {{{"text", text}}}},
-        {"role", "model"}
-      }},
-      {"index", 0}
-    }}},
-    {"promptFeedback", {{"safetyRatings", json::array()}}}
-  };
+      {"candidates",
+       {{{"content", {{"parts", {{{"text", text}}}}, {"role", "model"}}},
+         {"index", 0}}}},
+      {"promptFeedback", {{"safetyRatings", json::array()}}}};
 
   // Only add finishReason for non-streaming chunks
   if (!is_streaming_chunk) {
@@ -185,7 +179,9 @@ json CreateAPIResponse(const std::string& text, bool is_streaming_chunk = false)
 }
 
 // Handle generateContent endpoint (non-streaming)
-void HandleGenerateContentNonStreaming(ServerState& state, const httplib::Request& req, httplib::Response& res) {
+void HandleGenerateContentNonStreaming(ServerState& state,
+                                       const httplib::Request& req,
+                                       httplib::Response& res) {
   try {
     json request = json::parse(req.body);
 
@@ -199,7 +195,9 @@ void HandleGenerateContentNonStreaming(ServerState& state, const httplib::Reques
       prompt = WrapMessagesWithTurnMarkers(request["contents"]);
     } else {
       res.status = 400;
-      res.set_content(json{{"error", {{"message", "Missing 'contents' field"}}}}.dump(), "application/json");
+      res.set_content(
+          json{{"error", {{"message", "Missing 'contents' field"}}}}.dump(),
+          "application/json");
       return;
     }
 
@@ -209,12 +207,7 @@ void HandleGenerateContentNonStreaming(ServerState& state, const httplib::Reques
     // Set up runtime config
     RuntimeConfig runtime_config = ParseGenerationConfig(request);
 
-    // Collect full response
-    std::string full_response;
-    runtime_config.stream_token = [&full_response](int token, float) {
-      // Skip EOS token
-      return true;
-    };
+    runtime_config.stream_token = [](int token, float) { return true; };
 
     // Tokenize prompt
     std::vector<int> tokens = WrapAndTokenize(
@@ -227,7 +220,8 @@ void HandleGenerateContentNonStreaming(ServerState& state, const httplib::Reques
 
     // Temporarily redirect output to capture response
     std::stringstream output;
-    runtime_config.stream_token = [&output, &state, &session, &tokens](int token, float) {
+    runtime_config.stream_token = [&output, &state, &session, &tokens](
+                                      int token, float) {
       // Skip prompt tokens
       if (session.abs_pos < tokens.size()) {
         session.abs_pos++;
@@ -279,7 +273,9 @@ void HandleGenerateContentNonStreaming(ServerState& state, const httplib::Reques
 }
 
 // Handle streamGenerateContent endpoint with SSE)
-void HandleGenerateContentStreaming(ServerState& state, const httplib::Request& req, httplib::Response& res) {
+void HandleGenerateContentStreaming(ServerState& state,
+                                    const httplib::Request& req,
+                                    httplib::Response& res) {
   try {
     json request = json::parse(req.body);
 
@@ -293,7 +289,9 @@ void HandleGenerateContentStreaming(ServerState& state, const httplib::Request&
       prompt = WrapMessagesWithTurnMarkers(request["contents"]);
     } else {
       res.status = 400;
-      res.set_content(json{{"error", {{"message", "Missing 'contents' field"}}}}.dump(), "application/json");
+      res.set_content(
+          json{{"error", {{"message", "Missing 'contents' field"}}}}.dump(),
+          "application/json");
       return;
     }
 
@@ -305,88 +303,85 @@ void HandleGenerateContentStreaming(ServerState& state, const httplib::Request&
 
     // Set up chunked content provider for SSE
     res.set_chunked_content_provider(
-      "text/event-stream",
-      [&state, request, prompt, session_id](size_t offset, httplib::DataSink& sink) {
-        try {
-          // Lock for inference
-          std::lock_guard<std::mutex> lock(state.inference_mutex);
-          auto& session = state.GetOrCreateSession(session_id);
+        "text/event-stream", [&state, request, prompt, session_id](
+                                 size_t offset, httplib::DataSink& sink) {
+          try {
+            // Lock for inference
+            std::lock_guard<std::mutex> lock(state.inference_mutex);
+            auto& session = state.GetOrCreateSession(session_id);
 
-          // Set up runtime config
-          RuntimeConfig runtime_config = ParseGenerationConfig(request);
+            // Set up runtime config
+            RuntimeConfig runtime_config = ParseGenerationConfig(request);
 
-          // Tokenize prompt
-          std::vector<int> tokens = WrapAndTokenize(
-              state.gemma->Tokenizer(), state.gemma->ChatTemplate(),
-              state.gemma->Config().wrapping, session.abs_pos, prompt);
+            // Tokenize prompt
+            std::vector<int> tokens = WrapAndTokenize(
+                state.gemma->Tokenizer(), state.gemma->ChatTemplate(),
+                state.gemma->Config().wrapping, session.abs_pos, prompt);
+
+            // Stream token callback
+            std::string accumulated_text;
+            auto stream_token = [&](int token, float) {
+              // Skip prompt tokens
+              if (session.abs_pos < tokens.size()) {
+                session.abs_pos++;
+                return true;
+              }
 
-          // Stream token callback
-          std::string accumulated_text;
-          auto stream_token = [&](int token, float) {
-            // Skip prompt tokens
-            if (session.abs_pos < tokens.size()) {
               session.abs_pos++;
+
+              // Check for EOS
+              if (state.gemma->Config().IsEOS(token)) {
+                return true;
+              }
+
+              // Decode token
+              std::string token_text;
+              state.gemma->Tokenizer().Decode(std::vector<int>{token},
+                                              &token_text);
+              accumulated_text += token_text;
+
+              // Send SSE event using unified formatter
+              json event = CreateAPIResponse(token_text, true);
+
+              std::string sse_data = "data: " + event.dump() + "\n\n";
+              sink.write(sse_data.data(), sse_data.size());
+
               return true;
-            }
+            };
 
-            session.abs_pos++;
+            runtime_config.stream_token = stream_token;
 
-            // Check for EOS
-            if (state.gemma->Config().IsEOS(token)) {
-              return true;
-            }
+            // Run inference with KV cache
+            TimingInfo timing_info = {.verbosity = 0};
+            size_t prefix_end = 0;
 
-            // Decode token
-            std::string token_text;
-            state.gemma->Tokenizer().Decode(std::vector<int>{token}, &token_text);
-            accumulated_text += token_text;
+            state.gemma->Generate(runtime_config, tokens, session.abs_pos,
+                                  prefix_end, *session.kv_cache, *state.env,
+                                  timing_info);
 
-            // Send SSE event using unified formatter
-            json event = CreateAPIResponse(token_text, true);
+            // Send final event using unified formatter
+            json final_event = CreateAPIResponse("", false);
+            final_event["usageMetadata"] = {
+                {"promptTokenCount", tokens.size()},
+                {"candidatesTokenCount", session.abs_pos - tokens.size()},
+                {"totalTokenCount", session.abs_pos}};
 
-            std::string sse_data = "data: " + event.dump() + "\n\n";
-            sink.write(sse_data.data(), sse_data.size());
+            std::string final_sse = "data: " + final_event.dump() + "\n\n";
+            sink.write(final_sse.data(), final_sse.size());
 
-            return true;
-          };
-
-          runtime_config.stream_token = stream_token;
-
-          // Run inference with KV cache
-          TimingInfo timing_info = {.verbosity = 0};
-          size_t prefix_end = 0;
-
-          state.gemma->Generate(runtime_config, tokens, session.abs_pos,
-                                prefix_end, *session.kv_cache, *state.env,
-                                timing_info);
-
-          // Send final event using unified formatter
-          json final_event = CreateAPIResponse("", false);
-          final_event["usageMetadata"] = {
-            {"promptTokenCount", tokens.size()},
-            {"candidatesTokenCount", session.abs_pos - tokens.size()},
-            {"totalTokenCount", session.abs_pos}
-          };
-
-          std::string final_sse = "data: " + final_event.dump() + "\n\n";
-          sink.write(final_sse.data(), final_sse.size());
-
-          // Send done event
-          sink.write("data: [DONE]\n\n", 15);
-
-          // Ensure all data is sent
-          sink.done();
-          return false;  // End streaming
-
-        } catch (const std::exception& e) {
-          json error_event = {{"error", {{"message", e.what()}}}};
-          std::string error_sse = "data: " + error_event.dump() + "\n\n";
-          sink.write(error_sse.data(), error_sse.size());
-          return false;
-        }
-      }
-    );
+            // Send done event
+            sink.write("data: [DONE]\n\n", 15);
 
+            // Ensure all data is sent
+            sink.done();
+            return false;  // End streaming
+          } catch (const std::exception& e) {
+            json error_event = {{"error", {{"message", e.what()}}}};
+            std::string error_sse = "data: " + error_event.dump() + "\n\n";
+            sink.write(error_sse.data(), error_sse.size());
+            return false;
+          }
+        });
   } catch (const json::exception& e) {
     res.status = 400;
     res.set_content(
@@ -398,20 +393,20 @@ void HandleGenerateContentStreaming(ServerState& state, const httplib::Request&
 }
 
 // Handle models list endpoint
-void HandleListModels(ServerState& state, const InferenceArgs& inference, const httplib::Request& req, httplib::Response& res) {
+void HandleListModels(ServerState& state, const InferenceArgs& inference,
+                      const httplib::Request& req, httplib::Response& res) {
   json response = {
-    {"models", {{
-      {"name", "models/" + inference.model},
-      {"version", "001"},
-      {"displayName", inference.model},
-      {"description", inference.model + " model running locally"},
-      {"inputTokenLimit", 8192},
-      {"outputTokenLimit", 8192},
-      {"supportedGenerationMethods", json::array({"generateContent", "streamGenerateContent"})},
-      {"temperature", 1.0},
-      {"topK", 1}
-    }}}
-  };
+      {"models",
+       {{{"name", "models/" + inference.model},
+         {"version", "001"},
+         {"displayName", inference.model},
+         {"description", inference.model + " model running locally"},
+         {"inputTokenLimit", 8192},
+         {"outputTokenLimit", 8192},
+         {"supportedGenerationMethods",
+          json::array({"generateContent", "streamGenerateContent"})},
+         {"temperature", 1.0},
+         {"topK", 1}}}}};
 
   res.set_content(response.dump(), "application/json");
 }
@@ -421,39 +416,45 @@ void HandleListModels(ServerState& state, const InferenceArgs& inference, const
 //   server_running = false;
 // }
 
-void RunServer(const LoaderArgs& loader, const ThreadingArgs& threading,
-               const InferenceArgs& inference) {
+void RunServer(const GemmaArgs& args) {
   std::cerr << "Loading model..." << std::endl;
 
   // Initialize model
-  ThreadingContext ctx(threading);
+  ThreadingContext ctx(args.threading);
   MatMulEnv env(ctx);
-
   ServerState state;
-  state.gemma = std::make_unique<Gemma>(loader, inference, ctx);
+  state.gemma = std::make_unique<Gemma>(args, ctx);
   state.env = &env;
   state.ctx = &ctx;
 
+  const InferenceArgs& inference = args.inference;
+
   httplib::Server server;
 
   // Set up routes
-  server.Get("/", [&inference](const httplib::Request&, httplib::Response& res) {
-    res.set_content("API Server (gemma.cpp) - Use POST /v1beta/models/" + inference.model + ":generateContent", "text/plain");
-  });
+  server.Get(
+      "/", [&inference](const httplib::Request&, httplib::Response& res) {
+        res.set_content("API Server (gemma.cpp) - Use POST /v1beta/models/" +
+                            inference.model + ":generateContent",
+                        "text/plain");
+      });
 
   // API endpoints
-  server.Get("/v1beta/models", [&state, &inference](const httplib::Request& req, httplib::Response& res) {
+  server.Get("/v1beta/models", [&state, &inference](const httplib::Request& req,
+                                                    httplib::Response& res) {
     HandleListModels(state, inference, req, res);
   });
 
   std::string model_endpoint = "/v1beta/models/" + inference.model;
-  server.Post(model_endpoint + ":generateContent", [&state](const httplib::Request& req, httplib::Response& res) {
-    HandleGenerateContentNonStreaming(state, req, res);
-  });
+  server.Post(model_endpoint + ":generateContent",
+              [&state](const httplib::Request& req, httplib::Response& res) {
+                HandleGenerateContentNonStreaming(state, req, res);
+              });
 
-  server.Post(model_endpoint + ":streamGenerateContent", [&state](const httplib::Request& req, httplib::Response& res) {
-    HandleGenerateContentStreaming(state, req, res);
-  });
+  server.Post(model_endpoint + ":streamGenerateContent",
+              [&state](const httplib::Request& req, httplib::Response& res) {
+                HandleGenerateContentStreaming(state, req, res);
+              });
 
   // Periodic cleanup of old sessions
   std::thread cleanup_thread([&state]() {
@@ -466,12 +467,15 @@ void RunServer(const LoaderArgs& loader, const ThreadingArgs& threading,
   std::cerr << "Starting API server on port " << inference.port << std::endl;
   std::cerr << "Model loaded successfully" << std::endl;
   std::cerr << "Endpoints:" << std::endl;
-  std::cerr << "  POST /v1beta/models/" << inference.model << ":generateContent" << std::endl;
-  std::cerr << "  POST /v1beta/models/" << inference.model << ":streamGenerateContent (SSE)" << std::endl;
+  std::cerr << "  POST /v1beta/models/" << inference.model << ":generateContent"
+            << std::endl;
+  std::cerr << "  POST /v1beta/models/" << inference.model
+            << ":streamGenerateContent (SSE)" << std::endl;
   std::cerr << "  GET  /v1beta/models" << std::endl;
 
   if (!server.listen("0.0.0.0", inference.port)) {
-    std::cerr << "Failed to start server on port " << inference.port << std::endl;
+    std::cerr << "Failed to start server on port " << inference.port
+              << std::endl;
   }
 
   cleanup_thread.join();
@@ -482,35 +486,27 @@ void RunServer(const LoaderArgs& loader, const ThreadingArgs& threading,
 int main(int argc, char** argv) {
   gcpp::InternalInit();
 
-  gcpp::LoaderArgs loader(argc, argv);
-  gcpp::ThreadingArgs threading(argc, argv);
-  gcpp::InferenceArgs inference(argc, argv);
+  gcpp::ConsumedArgs consumed(argc, argv);
+  gcpp::GemmaArgs args(argc, argv, consumed);
 
   if (gcpp::HasHelp(argc, argv)) {
-    std::cerr << "\n\nAPI server for gemma.cpp\n";
-    std::cout << "========================\n\n";
-    std::cerr << "Usage: " << argv[0] << " --weights <path> --tokenizer <path> [options]\n";
-    std::cerr << "\nOptions:\n";
-    std::cerr << "  --port PORT      Server port (default: 8080)\n";
-    std::cerr << "  --model MODEL    Model name for endpoints (default: gemma3-4b)\n";
-    std::cerr << "\n";
-    std::cerr << "\n*Model Loading Arguments*\n\n";
-    loader.Help();
-    std::cerr << "\n*Threading Arguments*\n\n";
-    threading.Help();
-    std::cerr << "\n*Inference Arguments*\n\n";
-    inference.Help();
-    std::cerr << "\n";
+    fprintf(
+        stderr,
+        "\n\nAPI server for gemma.cpp\n"
+        "========================\n\n"
+        "  --port PORT      Server port (default: 8080)\n"
+        "  --model MODEL    Model name for endpoints (default: gemma3-4b)\n");
+    args.Help();
     return 0;
   }
 
-  // Arguments are now handled by InferenceArgs
+  consumed.AbortIfUnconsumed();
 
   // // Set up signal handler
   // signal(SIGINT, gcpp::HandleShutdown);
   // signal(SIGTERM, gcpp::HandleShutdown);
 
-  gcpp::RunServer(loader, threading, inference);
+  gcpp::RunServer(args);
 
   return 0;
 }
diff --git a/gemma/attention.cc b/gemma/attention.cc
index 117b533..eccfd25 100644
--- a/gemma/attention.cc
+++ b/gemma/attention.cc
@@ -43,6 +43,7 @@
 // After highway.h
 #include "compression/compress-inl.h"
 #include "gemma/flash_attention.h"
+#include "gemma/gemma-inl.h"
 #include "ops/ops-inl.h"
 
 HWY_BEFORE_NAMESPACE();
@@ -57,33 +58,35 @@ static HWY_INLINE void QDotK(const size_t start_pos, const size_t last_pos,
                              const MatPtrT<KV_t>& k, float* HWY_RESTRICT att,
                              ThreadingContext& ctx, const size_t worker) {
   GCPP_ZONE(ctx, worker, Zones::kGenAttentionQDotK);
-  if (HWY_LIKELY(last_pos < static_cast<size_t>(div_seq_len.GetDivisor()))) {
-    // Slightly faster: no wraparound.
-    for (size_t pos = start_pos; pos <= last_pos; ++pos) {
-      const float score = Dot(q, k.Row(pos), k.Cols());
-      att[pos] = score;
-    }
-  } else {
-    for (size_t pos = start_pos; pos <= last_pos; ++pos) {
-      const size_t pos_modulo = div_seq_len.Remainder(pos);
-      const float score = Dot(q, k.Row(pos_modulo), k.Cols());
-      att[pos_modulo] = score;
-    }
+  const hn::ScalableTag<BF16> dbf;
+  const size_t qkv_dim = k.Cols();
+  HWY_ALIGN BF16 q_bf[kMaxQKVDim];
+
+  CompressPerThread tls;
+  const hn::ScalableTag<float> df;
+  CompressTraits<BF16>::Compress(df, q, qkv_dim, tls, MakeSpan(q_bf, qkv_dim),
+                                 0);
+
+  // --seq_len must be large enough to avoid wraparound.
+  HWY_DASSERT(last_pos < static_cast<size_t>(div_seq_len.GetDivisor()));
+  for (size_t pos = start_pos; pos <= last_pos; ++pos) {
+    const float score =
+        Dot(dbf, MakeConstSpan(q_bf, qkv_dim), 0, k.Row(pos), qkv_dim);
+    att[pos] = score;
   }
 }
 
 void PositionalEncodingQK(float* qk, const size_t layer_idx,
-                          const LayerWeightsPtrs& layer,
-                          const AttentionActivations& activations,
+                          const AttentionActivationsPtrs& activations,
                           ThreadingContext& ctx, const size_t worker,
                           const size_t pos, const float mul) {
-  const size_t qkv_dim = layer.layer_config.qkv_dim;
-  const PostQKType& post_qk = layer.layer_config.post_qk;
+  const LayerConfig& layer_config = activations.config.layer_configs[layer_idx];
+  const size_t qkv_dim = layer_config.qkv_dim;
+  const PostQKType& post_qk = layer_config.post_qk;
   // qk is either q or k, so qkv_dim is the length we operate on.
   const float* inv_timescale = activations.inv_timescale.PackedScale1();
   const bool is_global_layer = activations.config.IsGlobalLayer(layer_idx);
-  // TODO: add a config flag instead of hardcoding the model.
-  if (is_global_layer && IsVLM(activations.config.model)) {
+  if (is_global_layer && activations.config.use_global_timescale) {
     inv_timescale = activations.inv_timescale_global.PackedScale1();
   }
   // PostQKType::Rope
@@ -104,62 +107,52 @@ static HWY_INLINE void WeightedSumV(
     const hwy::Divisor& div_seq_len, const float* HWY_RESTRICT att,
     const MatPtrT<KV_t>& v, float* HWY_RESTRICT att_out, ThreadingContext& ctx,
     const size_t worker) {
-  if (HWY_LIKELY(last_pos < static_cast<size_t>(div_seq_len.GetDivisor()))) {
-    // Slightly faster: no wraparound. Could be replaced with MatMul(att, v) if
-    // we supported non-transposed B.
-    // TODO: 2..4x unroll
-    MulByConstTo(att[start_pos], v.Row(start_pos), att_out, v.Cols(), ctx,
-                 worker);
-    for (size_t pos = start_pos + 1; pos <= last_pos; ++pos) {
-      MulByConstAndAdd(att[pos], v.Row(pos), att_out, v.Cols());
-    }
-  } else {
-    {
-      const size_t pos_mod = div_seq_len.Remainder(start_pos);
-      MulByConstTo(att[pos_mod], v.Row(pos_mod), att_out, v.Cols(), ctx,
-                   worker);
-    }
-    for (size_t pos = start_pos + 1; pos <= last_pos; ++pos) {
-      const size_t pos_mod = div_seq_len.Remainder(pos);
-      MulByConstAndAdd(att[pos_mod], v.Row(pos_mod), att_out, v.Cols());
-    }
+  // --seq_len must be large enough to avoid wraparound.
+  HWY_DASSERT(last_pos < static_cast<size_t>(div_seq_len.GetDivisor()));
+  // TODO: replace with MatMul(att, v) after it supports non-transposed B.
+  MulByConstTo(att[start_pos], v.Row(start_pos), att_out, v.Cols(), ctx,
+               worker);
+  for (size_t pos = start_pos + 1; pos <= last_pos; ++pos) {
+    MulByConstAndAdd(att[pos], v.Row(pos), att_out, v.Cols());
   }
 }
 
 // Calculates the attention outputs for a single q, which may be updated
 // in place for RMSNorm.
 void SingleDotSoftmaxWeightedSum(
-    const size_t pos, const size_t start_pos, const size_t last_pos,
+    const size_t q_pos, const size_t kv_start_pos, const size_t kv_last_pos,
     float* HWY_RESTRICT q, const MatPtrT<KV_t>& k, const MatPtrT<KV_t>& v,
-    const size_t layer_idx, const LayerWeightsPtrs& layer,
-    const AttentionActivations& activations, float* HWY_RESTRICT att,
-    float* HWY_RESTRICT att_out, ThreadingContext& ctx, const size_t worker) {
+    const MatPtr& query_norm_scale, const size_t layer_idx,
+    const AttentionActivationsPtrs& activations, float* HWY_RESTRICT att,
+    float* HWY_RESTRICT att_out, const SMOptions& sm_options,
+    ThreadingContext& ctx, const size_t worker) {
   const float att_cap = activations.config.att_cap;
   const float query_scale = activations.query_scale;
-  const size_t seq_len =
-      static_cast<size_t>(activations.div_seq_len.GetDivisor());
+  // --seq_len must be large enough to avoid wraparound.
+  HWY_DASSERT(kv_last_pos < activations.SeqLen());
+  const LayerConfig& layer_config = activations.config.layer_configs[layer_idx];
 
   // Apply rope and scaling to Q.
-  if (layer.query_norm_scale.HasPtr()) {
-    CallUpcasted(&layer.query_norm_scale, [&](const auto* weights_t) {
+  if (query_norm_scale.HasPtr()) {
+    CallUpcasted(&query_norm_scale, [&](const auto* weights_t) {
       RMSNormInplace(weights_t->PackedScale1(), /*w_ofs=*/0, q,
-                     layer.layer_config.qkv_dim, ctx, worker);
+                     layer_config.qkv_dim, ctx, worker);
     });
   }
 
-  PositionalEncodingQK(q, layer_idx, layer, activations, ctx, worker, pos,
+  PositionalEncodingQK(q, layer_idx, activations, ctx, worker, q_pos,
                        query_scale);
 
-  QDotK(start_pos, last_pos, activations.div_seq_len, q, k, att, ctx, worker);
+  QDotK(kv_start_pos, kv_last_pos, activations.div_seq_len, q, k, att, ctx,
+        worker);
 
   // SoftMax with optional SoftCap yields "probabilities" in att.
-  const size_t att_len = HWY_MIN(last_pos + 1, seq_len);
-  const Logits logits(att, att_len);
+  const Logits logits(att, kv_last_pos + 1);
   MaybeLogitsSoftCap(att_cap, logits, ctx, worker);
-  Softmax(logits, ctx, worker, /*temperature=*/1.0f);
+  Softmax(logits, ctx, worker, /*temperature=*/1.0f, sm_options);
 
-  WeightedSumV(start_pos, last_pos, activations.div_seq_len, att, v, att_out,
-               ctx, worker);
+  WeightedSumV(kv_start_pos, kv_last_pos, activations.div_seq_len, att, v,
+               att_out, ctx, worker);
 }
 
 // The attention window usually starts at 0 unless `pos` is larger than
@@ -170,13 +163,13 @@ size_t StartPos(size_t pos, const ModelConfig& config, size_t layer_idx) {
 }
 
 void DotSoftmaxWeightedSum(const size_t num_tokens, const size_t layer_idx,
-                           const LayerWeightsPtrs& layer,
-                           AttentionActivations& activations, QBatch& qbatch,
-                           ThreadingContext& ctx) {
+                           const MatPtr& query_norm_scale,
+                           AttentionActivationsPtrs& activations,
+                           QBatch& qbatch, ThreadingContext& ctx) {
   GCPP_ZONE(ctx, 0, Zones::kGenAttentionDotSoftmaxWeightedSumInclusive);
 
   const hwy::Divisor div_qbatch(qbatch.Size());
-  const LayerConfig& layer_config = layer.layer_config;
+  const LayerConfig& layer_config = activations.config.layer_configs[layer_idx];
   const size_t qkv_dim = layer_config.qkv_dim;
 
   // A "head group" in the context of GQA refers to a collection of query
@@ -184,8 +177,7 @@ void DotSoftmaxWeightedSum(const size_t num_tokens, const size_t layer_idx,
   const size_t kHeadGroups = layer_config.heads / layer_config.kv_heads;
 
   const size_t cache_layer_size = layer_config.CacheLayerSize();
-  const size_t seq_len =
-      static_cast<size_t>(activations.div_seq_len.GetDivisor());
+  const size_t seq_len = activations.SeqLen();
   // All layers should have the same number of heads.
   HWY_DASSERT(activations.div_heads.GetDivisor() == layer_config.heads);
 
@@ -196,12 +188,12 @@ void DotSoftmaxWeightedSum(const size_t num_tokens, const size_t layer_idx,
     GCPP_ZONE(ctx, worker, Zones::kGenAttentionDotSoftmaxWeightedSumPar);
 
     const size_t qi = div_qbatch.Remainder(tq_idx);
-    const size_t batch_idx = div_qbatch.Divide(tq_idx);
+    const size_t token_idx = div_qbatch.Divide(tq_idx);
     auto& kv_cache = qbatch.KV(qi).kv_cache;
 
     // Find the token position in the query and calculate
     // the range of cache positions to attend to.
-    const size_t pos = qbatch.Pos(qi) + batch_idx;
+    const size_t pos = qbatch.Pos(qi) + token_idx;
     const size_t start_pos = StartPos(pos, activations.config, layer_idx);
     size_t last_pos = pos;
     const size_t prefix_end = qbatch.PrefixEnd(qi);
@@ -214,6 +206,8 @@ void DotSoftmaxWeightedSum(const size_t num_tokens, const size_t layer_idx,
     float* HWY_RESTRICT att = activations.att.Row(tq_idx) + head * seq_len;
     float* HWY_RESTRICT att_out =
         activations.att_out.Row(tq_idx) + head * qkv_dim;
+    SMOptions sm_options{.max_out = activations.softmax_max.Row(tq_idx) + head,
+                         .d_out = activations.softmax_d.Row(tq_idx) + head};
 
     // Make strided read-only views into the kv cache for
     // this query and head.
@@ -224,8 +218,10 @@ void DotSoftmaxWeightedSum(const size_t num_tokens, const size_t layer_idx,
     MatPtrT<KV_t> v("v_view", Extents2D(seq_len, qkv_dim));
     v.SetPtr(kv_cache.Row(0) + kv_head_offset + qkv_dim, kv_cache.Stride());
 
-    SingleDotSoftmaxWeightedSum(pos, start_pos, last_pos, q, k, v, layer_idx,
-                                layer, activations, att, att_out, ctx, worker);
+    constexpr size_t offset = 0;  // placeholder, do not remove
+    SingleDotSoftmaxWeightedSum(pos + offset, start_pos, last_pos, q, k, v,
+                                query_norm_scale, layer_idx, activations, att,
+                                att_out, sm_options, ctx, worker);
   };
 
   {
@@ -246,7 +242,7 @@ void DotSoftmaxWeightedSum(const size_t num_tokens, const size_t layer_idx,
 // Fills activations.q and writes to KV cache.
 static HWY_INLINE void ComputeQKV(size_t num_tokens, const size_t layer_idx,
                                   const LayerWeightsPtrs& layer,
-                                  AttentionActivations& activations,
+                                  AttentionActivationsPtrs& activations,
                                   const QBatch& qbatch, const int flags,
                                   MatMulEnv& env) {
   GCPP_ZONE(env.ctx, hwy::Profiler::GlobalIdx(),
@@ -271,10 +267,14 @@ static HWY_INLINE void ComputeQKV(size_t num_tokens, const size_t layer_idx,
                                         layer.qkv_einsum_w2.Rows()));
   for (size_t interleaved_idx = 0; interleaved_idx < num_interleaved;
        ++interleaved_idx) {
+    // Index into qbatch, within [0, qbatch.Size()]
     const size_t qi = div_qbatch.Remainder(interleaved_idx);
-    const size_t batch_idx = div_qbatch.Divide(interleaved_idx);
-    const size_t cache_pos =
-        activations.div_seq_len.Remainder(qbatch.Pos(qi) + batch_idx);
+    // Index along token sequence, within [0, num_tokens)
+    const size_t token_idx = div_qbatch.Divide(interleaved_idx);
+    const size_t cache_pos = qbatch.Pos(qi) + token_idx;
+    // --seq_len must be large enough to avoid wraparound.
+    HWY_DASSERT(cache_pos < activations.SeqLen());
+
     env.row_ptrs[0][interleaved_idx] = reinterpret_cast<uint8_t*>(
         qbatch.KV(qi).kv_cache.Row(cache_pos) + layer_idx * cache_layer_size);
   }
@@ -286,15 +286,16 @@ static HWY_INLINE void ComputeQKV(size_t num_tokens, const size_t layer_idx,
   // Note that 2D parallelism is not worth the fork/join overhead because the
   // tasks are very lightweight.
   ParallelFor(
-      ParallelismStrategy::kFlat, kv_heads * num_interleaved, env.ctx,
+      Parallelism::kFlat, kv_heads * num_interleaved, env.ctx,
       /*cluster_idx=*/0, Callers::kAttComputeQKV,
       [&](size_t task, size_t worker) HWY_ATTR {
         const size_t head = task % kv_heads;
         const size_t interleaved_idx = task / kv_heads;
         const size_t qi = div_qbatch.Remainder(interleaved_idx);
-        const size_t batch_idx = div_qbatch.Divide(interleaved_idx);
-        const size_t pos = qbatch.Pos(qi) + batch_idx;
-        const size_t cache_pos = activations.div_seq_len.Remainder(pos);
+        const size_t token_idx = div_qbatch.Divide(interleaved_idx);
+        const size_t cache_pos = qbatch.Pos(qi) + token_idx;
+        // --seq_len must be large enough to avoid wraparound.
+        HWY_DASSERT(cache_pos < activations.SeqLen());
         auto& kv_cache = qbatch.KV(qi).kv_cache;
         KV_t* HWY_RESTRICT kv = kv_cache.Row(cache_pos) +
                                 layer_idx * cache_layer_size +
@@ -313,35 +314,18 @@ static HWY_INLINE void ComputeQKV(size_t num_tokens, const size_t layer_idx,
           });
         }
 
-        PositionalEncodingQK(kv_f32, layer_idx, layer, activations, env.ctx,
-                             worker, pos, /*mul=*/1.0f);
+        constexpr size_t offset = 0;  // placeholder, do not remove
+        PositionalEncodingQK(kv_f32, layer_idx, activations, env.ctx, worker,
+                             cache_pos + offset,
+                             /*mul=*/1.0f);
         CompressPerThread tls;
         Compress(kv_f32, 2 * qkv_dim, tls, MakeSpan(kv, 2 * qkv_dim), 0);
       });
 }
 
-// Sums encoded (`att_out`) over num_heads (`layer_config.heads`) and
-// head_dim (`qkv_dim`) into output (`layer_out`).
-static HWY_INLINE void SumHeads(const LayerWeightsPtrs& layer,
-                                AttentionActivations& activations,
-                                MatMulEnv& env) {
-  GCPP_ZONE(env.ctx, hwy::Profiler::GlobalIdx(), Zones::kGenAttentionSumHeads);
-  const LayerConfig& layer_config = layer.layer_config;
-  (void)layer_config;  // For HWY_DASSERT
-  // att_weights and att_out are concatenated heads, each of length
-  // layer_config.qkv_dim. Thus the [num_interleaved,
-  // layer_config.model_dim] matmul output is the sum over heads. Compare
-  // gemma/modules.py: attn_output = self.attn_vec_einsum('BTNH,NHD->BTD',
-  // encoded)
-  HWY_DASSERT(layer_config.model_dim != 0 && layer_config.heads != 0 &&
-              layer_config.qkv_dim != 0);
-  CallMatMul(activations.att_out, layer.att_weights, /*add=*/nullptr, env,
-             activations.att_sums);
-}
-
 void GemmaAttention(size_t num_tokens, const size_t layer_idx,
                     const LayerWeightsPtrs& layer,
-                    AttentionActivations& activations, QBatch& qbatch,
+                    AttentionActivationsPtrs& activations, QBatch& qbatch,
                     MatMulEnv& env, int flags) {
   GCPP_ZONE(env.ctx, hwy::Profiler::GlobalIdx(), Zones::kGenAttention);
 
@@ -353,13 +337,14 @@ void GemmaAttention(size_t num_tokens, const size_t layer_idx,
 
   ComputeQKV(num_tokens, layer_idx, layer, activations, qbatch, flags, env);
   if (flags & kAttentionUseOld) {
-    DotSoftmaxWeightedSum(num_tokens, layer_idx, layer, activations, qbatch,
-                          env.ctx);
+    DotSoftmaxWeightedSum(num_tokens, layer_idx, layer.query_norm_scale,
+                          activations, qbatch, env.ctx);
   } else {
     // * 2 does not help on Turin.
     FlashAttention(num_tokens,
                    /*target_parallelism=*/env.ctx.pools.MaxWorkers() * 1,
-                   layer_idx, layer, activations, qbatch, env.ctx);
+                   layer_idx, layer.query_norm_scale, activations, qbatch,
+                   env.ctx);
   }
   SumHeads(layer, activations, env);
 }
diff --git a/gemma/attention.h b/gemma/attention.h
index 6c4a48e..60e6823 100644
--- a/gemma/attention.h
+++ b/gemma/attention.h
@@ -29,8 +29,7 @@ namespace gcpp {
 #define GEMMA_DECL_ATTENTION(TARGET, NAMESPACE)                               \
   namespace NAMESPACE {                                                       \
   void PositionalEncodingQK(float* qk, size_t layer_idx,                      \
-                            const LayerWeightsPtrs& layer,                    \
-                            const AttentionActivations& activations,          \
+                            const AttentionActivationsPtrs& activations,      \
                             ThreadingContext& ctx, size_t worker, size_t pos, \
                             float mul);                                       \
                                                                               \
@@ -39,18 +38,18 @@ namespace gcpp {
   void SingleDotSoftmaxWeightedSum(                                           \
       const size_t pos, const size_t start_pos, const size_t last_pos,        \
       float* HWY_RESTRICT q, const MatPtrT<KV_t>& k, const MatPtrT<KV_t>& v,  \
-      size_t layer_idx, const LayerWeightsPtrs& layer,                        \
-      const AttentionActivations& activations, float* HWY_RESTRICT att,       \
+      const MatPtr& query_norm_scale, size_t layer_idx,                       \
+      const AttentionActivationsPtrs& activations, float* HWY_RESTRICT att,   \
       float* HWY_RESTRICT att_out, ThreadingContext& ctx, size_t worker);     \
                                                                               \
   void DotSoftmaxWeightedSum(const size_t num_tokens, size_t layer_idx,       \
-                             const LayerWeightsPtrs& layer,                   \
-                             AttentionActivations& activations,               \
+                             const MatPtr& query_norm_scale,                  \
+                             AttentionActivationsPtrs& activations,           \
                              QBatch& qbatch, ThreadingContext& ctx);          \
                                                                               \
   void GemmaAttention(size_t num_tokens, const size_t layer_idx,              \
                       const LayerWeightsPtrs& layer,                          \
-                      AttentionActivations& activations, QBatch& qbatch,      \
+                      AttentionActivationsPtrs& activations, QBatch& qbatch,  \
                       MatMulEnv& env, int flags);                             \
   /* NOLINTNEXTLINE(google-readability-namespace-comments) */                 \
   }  // namespace NAMESPACE
diff --git a/gemma/attention_test.cc b/gemma/attention_test.cc
new file mode 100644
index 0000000..53f1d01
--- /dev/null
+++ b/gemma/attention_test.cc
@@ -0,0 +1,570 @@
+#include <cstddef>
+#include <cstring>  // strcmp
+#include <memory>
+#include <numeric>
+#include <optional>
+#include <vector>
+
+#include "gtest/gtest.h"
+#include "compression/types.h"  // GEMMA_DISABLED_TARGETS
+#include "gemma/activations.h"
+#include "gemma/gemma.h"
+#include "gemma/gemma_args.h"
+#include "gemma/kv_cache.h"
+#include "gemma/weights.h"
+#include "ops/matmul.h"
+#include "util/mat.h"
+#include "util/threading_context.h"
+#include "hwy/aligned_allocator.h"
+#include "hwy/base.h"
+#ifndef HWY_DISABLED_TARGETS
+// These tests aren't designed to suss out instruction set specific problems.
+// Disable most targets to keep the tests fast and simple and not have to
+// worry about tolerances on floating point results.
+#define HWY_DISABLED_TARGETS GEMMA_DISABLED_TARGETS
+#endif  // HWY_DISABLED_TARGETS
+
+// clang-format off
+#undef HWY_TARGET_INCLUDE
+#define HWY_TARGET_INCLUDE "gemma/attention_test.cc"  // NOLINT
+// clang-format on
+#include "hwy/foreach_target.h"  // IWYU pragma: keep
+#include "hwy/highway.h"
+// After highway.h
+#include "compression/compress-inl.h"
+#include "gemma/attention.h"
+#include "gemma/configs.h"
+#include "util/test_util.h"
+#include "hwy/tests/test_util-inl.h"
+
+HWY_BEFORE_NAMESPACE();
+namespace gcpp {
+namespace HWY_NAMESPACE {
+
+void FillRandom(MatPtrT<float>& mat, uint64_t seed) {
+  hwy::RandomState rng(seed);
+  for (size_t r = 0; r < mat.Rows(); ++r) {
+    float* row = mat.Row(r);
+    for (size_t c = 0; c < mat.Cols(); ++c) {
+      row[c] = static_cast<float>(RandomGaussian(rng));
+    }
+  }
+}
+
+void AllocateAndFillRandom(MatPtr& mat, const Allocator& allocator,
+                           std::vector<MatOwner>& mat_owners, uint64_t seed) {
+  if (mat.IsEmpty()) return;
+  if (mat.GetType() == Type::kUnknown) {
+    mat.SetType(Type::kF32);
+  }
+  mat_owners.emplace_back();
+  mat_owners.back().AllocateFor(mat, allocator, MatPadding::kPacked);
+  MatPtrT<float> mat_f32(mat);
+  FillRandom(mat_f32, seed);
+}
+
+struct TestState {
+  TestState() : ctx({}), env(ctx) {}
+  ThreadingContext ctx;
+  std::vector<MatOwner> mat_owners;
+  MatMulEnv env;
+};
+
+struct TestModelState {
+  TestModelState(TestState& state)
+      : config(Model::GEMMA2_2B, Type::kF32, PromptWrapping::GEMMA_PT),
+        tensor_info_registry(config),
+        layer_config(config.layer_configs[0]),
+        layer(0, layer_config, tensor_info_registry) {
+    config.att_cap = 1024.0f;
+    AllocateAndFillRandom(layer.qkv_einsum_w, state.ctx.allocator,
+                          state.mat_owners, 42);
+    AllocateAndFillRandom(layer.attn_vec_einsum_w, state.ctx.allocator,
+                          state.mat_owners, 43);
+    AllocateAndFillRandom(layer.gating_einsum_w, state.ctx.allocator,
+                          state.mat_owners, 44);
+    AllocateAndFillRandom(layer.linear_w, state.ctx.allocator, state.mat_owners,
+                          45);
+    layer.Fixup(state.mat_owners, state.ctx);
+  }
+
+  ModelConfig config;
+  TensorInfoRegistry tensor_info_registry;
+  const LayerConfig& layer_config;
+  LayerWeightsPtrs layer;
+};
+
+struct TestAttentionState {
+  TestAttentionState(TestState& state, TestModelState& model_state,
+                     size_t num_tokens, size_t qbatch_size,
+                     AttentionImpl attention_impl)
+      : num_tokens(num_tokens),
+        qbatch_size(qbatch_size),
+        batch_size(qbatch_size * num_tokens),
+        runtime_config{.attention_impl = attention_impl},
+        tokens(num_tokens),
+        attention_storage_(model_state.config, model_state.layer_config,
+                           batch_size, num_tokens, runtime_config,
+                           state.ctx.allocator, row_ptrs_),
+        attention(model_state.config, num_tokens, attention_storage_) {
+    for (size_t i = 0; i < qbatch_size; ++i) {
+      kv_caches.emplace_back(model_state.config, inference_args,
+                             state.ctx.allocator);
+    }
+    activations.emplace(
+        runtime_config, model_state.config, runtime_config.prefill_tbatch_size,
+        kv_caches[0].SeqLen(), state.env.ctx, state.env.row_ptrs);
+    // Tokens don't matter, since we fill in pre_att_rms_out before calling
+    // GemmaAttention.
+    std::iota(tokens.begin(), tokens.end(), 1);
+    for (size_t i = 0; i < qbatch_size; ++i) {
+      prompts.emplace_back(tokens);
+    }
+    all_queries.emplace(prompts,
+                        hwy::Span<KVCache>(kv_caches.data(), kv_caches.size()));
+    qbatch.emplace(/*start=*/0, /*max_size=*/qbatch_size, *all_queries);
+    FillRandom(attention.pre_att_rms_out, 46);
+  }
+
+  const size_t num_tokens;
+  const size_t qbatch_size;
+  const size_t batch_size;
+  InferenceArgs inference_args;
+  RuntimeConfig runtime_config;
+  std::vector<KVCache> kv_caches;
+  std::optional<Activations> activations;
+  std::vector<int> tokens;
+  std::vector<PromptTokens> prompts;
+  std::optional<AllQueries> all_queries;
+  std::optional<QBatch> qbatch;
+  std::vector<hwy::AlignedFreeUniquePtr<uint8_t*[]>> row_ptrs_;
+  AttentionActivations attention_storage_;
+  AttentionActivationsPtrs attention;
+};
+
+double GetTolerance() {
+  const char* target_name = hwy::TargetName(HWY_TARGET);
+  if (strncmp(target_name, "AVX2", 4) == 0) {
+    return 2e-2;
+  } else if (strncmp(target_name, "AVX3", 4) == 0) {
+    return 3e-4;
+  } else if (strncmp(target_name, "NEON", 4) == 0) {
+    return 5e-3;
+  } else {
+    return 1e-7;
+  }
+}
+
+template <size_t kNumTokens, size_t kQBatchSize, size_t kDims>
+void CompareAttSumsWithGolden(
+    const AttentionActivationsPtrs& attention,
+    const float (&golden)[kNumTokens][kQBatchSize][kDims]) {
+  ASSERT_EQ(attention.att_sums.Rows(), kNumTokens * kQBatchSize);
+  ASSERT_LE(kDims, attention.att_sums.Cols());
+
+  hwy::AlignedFreeUniquePtr<float[]> actual_row =
+      hwy::AllocateAligned<float>(kDims);
+  for (size_t token_idx = 0; token_idx < kNumTokens; ++token_idx) {
+    for (size_t qi = 0; qi < kQBatchSize; ++qi) {
+      const size_t i = token_idx * kQBatchSize + qi;
+      for (size_t j = 0; j < kDims; ++j) {
+        actual_row[j] = hwy::F32FromBF16(attention.att_sums.Row(i)[j]);
+      }
+      EXPECT_TRUE(hwy::CompareArraySimilar(
+          golden[token_idx][qi], actual_row.get(), kDims, GetTolerance(),
+          hwy::TargetName(HWY_TARGET), __FILE__, __LINE__))
+          << "att_sums mismatch for token_idx=" << token_idx << " qi=" << qi;
+    }
+  }
+}
+
+template <size_t kNumTokens, size_t kQBatchSize, size_t kDims>
+void CompareKVCacheWithGolden(
+    const ModelConfig& config, hwy::Span<KVCache> kv_caches, const size_t layer,
+    const size_t kv_head,
+    const float (&k_golden)[kNumTokens][kQBatchSize][kDims],
+    const float (&v_golden)[kNumTokens][kQBatchSize][kDims]) {
+  const size_t qbatch_size = kv_caches.size();
+  ASSERT_EQ(kQBatchSize, qbatch_size);
+  const size_t start_offset = 0;
+  const size_t qkv_dim = config.layer_configs[0].qkv_dim;
+
+  hwy::AlignedFreeUniquePtr<float[]> actual_k_row =
+      hwy::AllocateAligned<float>(kDims);
+  hwy::AlignedFreeUniquePtr<float[]> actual_v_row =
+      hwy::AllocateAligned<float>(kDims);
+
+  const size_t cache_layer_size = config.layer_configs[layer].CacheLayerSize();
+  const size_t head_offset = kv_head * qkv_dim * 2;
+  const size_t kv_offset = layer * cache_layer_size + head_offset;
+
+  for (size_t token_idx = 0; token_idx < kNumTokens; ++token_idx) {
+    for (size_t qi = 0; qi < kQBatchSize; ++qi) {
+      const float* cache_row =
+          kv_caches[qi].kv_cache.Row(start_offset + token_idx);
+      for (size_t j = 0; j < kDims; ++j) {
+        actual_k_row[j] = cache_row[kv_offset + j];
+        actual_v_row[j] = cache_row[kv_offset + qkv_dim + j];
+      }
+      EXPECT_TRUE(hwy::CompareArraySimilar(
+          k_golden[token_idx][qi], actual_k_row.get(), kDims, GetTolerance(),
+          hwy::TargetName(HWY_TARGET), __FILE__, __LINE__))
+          << "K cache mismatch for token_idx=" << token_idx << " qi=" << qi
+          << " kv_head=" << kv_head;
+      EXPECT_TRUE(hwy::CompareArraySimilar(
+          v_golden[token_idx][qi], actual_v_row.get(), kDims, GetTolerance(),
+          hwy::TargetName(HWY_TARGET), __FILE__, __LINE__))
+          << "V cache mismatch for token_idx=" << token_idx << " qi=" << qi
+          << " kv_head=" << kv_head;
+    }
+  }
+}
+
+template <size_t kNumTokens, size_t kQBatchSize, size_t kDims>
+void CompareQVecsWithGolden(
+    const ModelConfig& config, const AttentionActivationsPtrs& attention,
+    const size_t q_head,
+    const float (&q_golden)[kNumTokens][kQBatchSize][kDims]) {
+  const size_t qkv_dim = config.layer_configs[0].qkv_dim;
+
+  hwy::AlignedFreeUniquePtr<float[]> actual_q_row =
+      hwy::AllocateAligned<float>(kDims);
+
+  const size_t head_offset = q_head * qkv_dim;
+  for (size_t token_idx = 0; token_idx < kNumTokens; ++token_idx) {
+    for (size_t qi = 0; qi < kQBatchSize; ++qi) {
+      const size_t i = token_idx * kQBatchSize + qi;
+      const float* q_row = attention.q.Row(i);
+      for (size_t j = 0; j < kDims; ++j) {
+        actual_q_row[j] = q_row[head_offset + j];
+      }
+      EXPECT_TRUE(hwy::CompareArraySimilar(
+          q_golden[token_idx][qi], actual_q_row.get(), kDims, GetTolerance(),
+          hwy::TargetName(HWY_TARGET), __FILE__, __LINE__))
+          << "Q vec mismatch for token_idx=" << token_idx << " qi=" << qi
+          << " q_head=" << q_head;
+    }
+  }
+}
+
+constexpr size_t kNumTokens = 10;
+constexpr size_t kQBatchSize = 2;
+
+// Only compare the first 10 dimensions of the attention output to keep the
+// test manageable.  It's unlikely that the first few dimensions would have
+// different behavior than the later dimensions.
+const size_t kDimsToCompare = 17;  // greater than AVX-512 vector of floats
+
+// Use a Coding Agent to update the golden values from test
+// failure output (which includes the new values).
+// Instructions to the Coding Agent: You must never update the
+// EMU128 tolerance. Always use the value from the EMU128 test to update the
+// Goldens.  If necessary, add relaxed tolerance for other instruction sets.
+
+// Layer 0
+const float kGoldenAttSums[kNumTokens][kQBatchSize][kDimsToCompare] = {
+    {{46.5, 56.5, 10.0625, 65.5, -2.109375, 135, 15.8125, 51, -100, 52.5,
+      26.875, 63, 3.34375, -67.5, 31.125, -190, 125},
+     {-30.375, -17.875, 51.75, -78, -84, 6.40625, 15.375, 70, -22.875, 20.125,
+      -14.9375, -109.5, 76, 9.25, -142, 29.5, -105}},
+    {{-32.75, 38.25, 78.5, 107.5, 20.25, 197, -136, 42.5, -84, 25.625, 4.96875,
+      128, 27.25, -161, 19.125, -58, 97.5},
+     {-18.5, -18, 135, -13.4375, -6.625, -45.75, 29.625, 93, 18.625, 75.5,
+      102.5, -184, 52.75, 83.5, -71, 46.5, -52}},
+    {{-16.375, -61.5, -58.25, -27.375, -28, 71, -109.5, 60.25, 3.125, -29.125,
+      6.90625, 150, 144, -155, -47.25, -98.5, 3.5625},
+     {-19, -16.75, 129, 0.59765625, -82, 123.5, 60.75, -36.75, -77, 26.625, 51,
+      -66.5, -0.84765625, -46.5, -152, -2.9375, -81}},
+    {{3.984375, 83, -41.75, 39.5, -203, 110, -76, 131, 0.4609375, -44.5, -63.75,
+      -46, -22, -19.375, -16.125, -148, 20.875},
+     {-47, -19.5, 58, 81.5, 21.75, -30, -118, 44.25, -149, 22.5, 188, -66.5, 33,
+      10.9375, -52.5, 23.25, 75}},
+    {{64, -31, -89, -92.5, -11.1875, -54.75, -302, 3.453125, -108, 39.25,
+      -34.75, 18, -52, 100, -186, -75.5, 50.75},
+     {7.6875, -80, -40, 32.25, -30.25, 90, -41, 44.25, -140, -2.4375, 82.5,
+      39.25, 65, 47.25, -89.5, -34.25, 137}},
+    {{39.75, 17.875, 115, 38.75, -44, 139, -53.25, -23.875, -13.0625, 38.5,
+      32.5, 53.75, 109, 4.09375, 57.5, -20.5, 132},
+     {143, 249, 5.09375, 0.83984375, 27.875, -5.84375, 30.25, -101.5, 65.5,
+      13.5, 195, -10.0625, 97.5, 2.203125, -97.5, -100, -19.25}},
+    {{-30.125, -169, -150, 58, -35.75, 22.75, 36.5, -32.25, -8.9375, 55.25,
+      -117, 26.375, 39.5, 125, 66, 48.75, 20.75},
+     {137, 5.25, 61.25, 37, -42.75, 240, 62, -164, 11.3125, 173, 174, 23.5,
+      88.5, 48.5, -46.25, -36.75, 101.5}},
+    {{-103, -47.5, 39, -48, -67.5, 121, -136, 99, 80, -47.5, 107.5, 48.75, 97.5,
+      125, -53.5, -14.625, 262},
+     {29.875, 7.34375, -36.75, -14.5, -27.5, 44.75, -67.5, -40.75, 71.5, 172,
+      81, -27.25, -3.03125, 111, -167, 59, 176}},
+    {{-37.25, 109.5, -26.125, -115.5, 108, 57.25, 1.3671875, 72, -122.5, 59.25,
+      -52, -12.625, 43.25, 16.25, -41.75, 26.5, 70.5},
+     {40.25, 53.25, -142, 78.5, 38, 4.3125, -27.75, -134, -85, 107.5, 2.5, 93.5,
+      58.25, 173, -53.5, 25.125, 4.8125}},
+    {{-8.4375, -35, -35.5, 131, -33.25, 106, 109.5, -92, -135, 80, 21.5,
+      -17.125, 15.25, 143, -27, 103, 101},
+     {-77, 40.75, -10.125, 33.25, -33, 104, -7.6875, 85.5, -40, 93, 61, 14.5625,
+      8.125, -99.5, 13.6875, -11.6875, 33}},
+};
+
+// Layer 0, *K*V Head 0
+const float kGoldenK[kNumTokens][kQBatchSize][kDimsToCompare] = {
+    {{-4.51717567, 6.93118095, 6.48003578, 9.12825584, 2.38755274, 11.8121576,
+      1.65376127, 5.04456615, -7.19549274, 2.57609844, 3.55331731, -3.48494458,
+      -8.90498638, 9.66047478, -0.379868984, 6.37043715, -2.24351144},
+     {0.152208567, 3.14520073, -8.35154343, 5.44226503, -6.74000502,
+      -1.43484437, -4.72092056, -9.48932, -6.12409401, -1.55352509, -3.90701318,
+      2.12124252, 3.93649936, -8.09877586, -3.30277514, -0.898857355,
+      1.76684189}},
+    {{4.378829, 5.05565643, -7.63948059, -5.74608946, 2.90109587, 0.155819178,
+      4.56115055, 1.37885749, 1.48427355, -1.07145202, 2.82399392, -1.20864201,
+      3.05434561, -2.65185618, -0.0731391, -8.2279253, 7.63228416},
+     {-0.702698231, 1.49563932, 6.42149782, -6.68306589, 1.85317755,
+      -7.70267582, 2.07357907, -7.60303402, -0.514724255, 0.308567047,
+      5.99250412, -4.67359257, -3.49322176, -2.62086344, -3.18411255,
+      2.04027057, -4.29057407}},
+    {{-1.20844436, 4.14724302, 6.04515219, 8.7753458, -0.975198627, 0.564640105,
+      5.39941597, 4.64036179, 0.366614938, 3.48258138, -0.470701456, 15.2267399,
+      4.63302803, 9.12662697, -5.89148045, 2.25731587, 5.24449492},
+     {4.57078934, -4.60315752, -3.3364439, 1.29875994, -3.40833569, -6.95262,
+      -6.39040232, -6.60212612, 6.63269806, -0.815209687, -5.0346446,
+      -4.13564968, 8.25674057, -6.0910182, -8.21130085, -8.91020393,
+      10.6188011}},
+    {{0.602011144, 2.22505236, 3.62411499, -4.07026958, 12.8036356, 3.76139069,
+      6.99502087, 7.02500725, -2.51568675, 4.2489934, 0.00210827589,
+      -1.43267739, -2.10394144, -0.0506809056, -1.54883039, 4.3740139,
+      -1.61869526},
+     {-6.37204599, -3.34989691, 2.10935307, 4.23634195, 5.79134035, 13.502944,
+      -2.19158888, -1.55771351, -1.22244942, 3.36499929, -2.11375904,
+      -4.5448761, 1.0611912, -2.47849369, -0.212709218, 0.363292456,
+      7.91467094}},
+    {{-8.85739231, -4.08585882, -0.618261, 6.52911091, 5.14922285, 7.6869874,
+      0.750387549, -0.812200725, 2.7509625, 6.29693508, -1.77248931, 5.68896484,
+      -6.9369607, -4.61359406, 0.184977874, -1.27769828, -2.1619854},
+     {-8.2555, 2.84032059, -1.03791106, 2.07648611, -4.94546843, 1.76888537,
+      -1.75901175, 11.2628574, 1.41086221, -3.58669901, -2.85925198, 2.29133463,
+      1.55509436, -0.0553357825, -10.0363655, 1.94261, -2.95691729}},
+    {{0.919141412, 1.97533965, -11.3202848, -3.3137629, -4.7161727, 5.07012081,
+      1.76256621, 8.20588207, 6.05700159, -3.89765406, -1.13639557, -1.32326794,
+      -3.01544905, -0.585309267, 2.60637712, 2.83708405, -3.39202118},
+     {9.11918, 2.11261511, -5.87290621, 11.6033278, -4.66597795, -7.13774204,
+      -9.10563755, -2.48294282, 3.35282946, -3.75122213, 0.404774547,
+      -9.11625195, 4.85711479, 1.43184578, 1.47673059, -4.75093, -3.45323014}},
+    {{4.17705393, -4.95192289, -10.5068378, 3.90004015, -3.51306129, 5.38068056,
+      0.901511431, 11.222868, 2.67285442, 9.18779, 5.61346769, 3.06534624,
+      -3.78898215, 0.767340839, 15.8207836, -4.14079094, -4.63177109},
+     {3.61795235, -7.00262165, 2.08284521, -6.70515728, 1.93205631, 2.84467721,
+      3.94591737, -6.18882942, -1.78465152, -9.39100933, -10.8780289,
+      6.32468653, 6.53142738, -3.30765963, 2.89132166, 4.53347206, 1.89792418}},
+    {{-0.361971855, -1.57735932, 5.07296801, -1.55669761, -1.44996238,
+      7.29838896, 5.23075104, -0.512441278, -3.59834242, 2.38584423, 6.48518324,
+      -1.48220074, -2.4264791, 10.7237988, 5.64735842, 5.6251297, -7.04244423},
+     {-0.795628309, 7.30230665, -1.71035647, -16.6999454, 3.05102086,
+      -4.9243927, 4.28508186, -0.694577456, 6.58464718, 4.40330124, 3.3250041,
+      1.90579033, -6.29048729, 2.55308104, -4.9746747, -0.681708, -5.98152351}},
+    {{2.57555652, -3.5651083, 0.784440041, -4.7043705, 2.37520599, -3.62385964,
+      -3.48913693, -7.28049421, -5.48726082, 1.95519221, 7.25192928, 3.07074118,
+      -11.9897156, 5.92244673, 5.07564354, 0.162699938, -6.00809956},
+     {5.56260443, -5.7683115, 1.26402235, -17.507719, 4.18873024, -3.20694613,
+      -4.42512083, 1.78077614, -3.25167561, 0.864362717, 0.474019766,
+      -7.92327404, -2.27795148, -0.436354101, -3.15722394, 0.415780187,
+      2.60931611}},
+    {{-9.43858051, 0.391518891, -2.74012518, 4.9842453, 7.48263216, -16.3434925,
+      -4.75156116, -1.99114823, 3.99918842, -5.95400572, 10.8700314, 1.07596064,
+      0.30389142, 8.39548779, -5.11913681, 5.45641088, -5.63240337},
+     {-1.22347319, 9.57339382, -1.31736016, -5.02770805, -4.81617355,
+      -1.96618557, -0.456317186, 12.6451035, -1.50221801, 6.7991147,
+      -5.97842169, 1.85410941, -8.44729, 0.378282309, 0.0442156792, 17.6773052,
+      -7.43491}},
+};
+
+// Layer 0, K*V* Head 0
+const float kGoldenV[kNumTokens][kQBatchSize][kDimsToCompare] = {
+    {{2.77553034, -7.67514181, -1.60433948, 4.67795134, -1.75084186, 8.57896423,
+      -1.15065813, -3.75088787, -4.7442131, -1.68890858, -10.0202332,
+      -4.20167446, 9.36844635, 13.7364845, 11.5634, 2.95288706, 2.89380026},
+     {-4.79950905, -1.66658688, 4.14471292, -4.95649052, -5.4200325, 3.52626801,
+      -10.9432049, 0.338347554, -1.53204226, 0.473476171, -0.58271, 1.42195463,
+      0.301399827, -4.40214968, -2.12298298, 9.27825642, -0.690600872}},
+    {{-10.6566734, 4.12785721, 4.54053593, -1.39667869, -1.55028772, 0.20508635,
+      -0.00620913506, 2.93214, -0.788117647, 2.78032446, -2.68898249, 9.5985508,
+      -10.6630878, -11.9006901, 0.851743698, 0.581826329, 5.21927929},
+     {-0.322291255, 2.63848567, -2.30808377, -13.0153809, 2.74378228,
+      3.21460533, 0.688529968, 2.37544608, 6.06825066, 4.57566404, 1.17124248,
+      -7.96587658, -2.65279341, 4.75271225, -4.09937954, -10.3570251,
+      3.30500841}},
+    {{-3.34342527, 6.03099537, 6.335958, 0.993818045, 0.905343294, 6.93058586,
+      3.9635396, 10.8044815, 7.8620863, -10.1157322, -3.92666101, -0.183003783,
+      -5.27309418, -1.45110512, -8.96734, -2.63866425, 2.19913912},
+     {16.416317, -1.62025332, 2.3161006, 3.32571959, -1.79581594, -10.2925539,
+      -5.86338425, -6.36642933, 9.18872166, 5.95524168, 6.38640785, 8.23832,
+      -6.57342291, -14.2017632, 1.10925388, 4.27255058, -2.65661311}},
+    {{6.58254147, -6.96165133, -4.97437, -2.33467388, 5.83671236, -0.794236898,
+      -2.03117108, -3.93387103, -5.96872902, 5.83316422, 3.01795, -4.05260706,
+      -4.39556885, 3.24399853, 10.1573639, 4.71967888, 0.274738848},
+     {7.13243389, -8.04649162, 2.53055143, 2.0771277, -0.667295456, -13.0285645,
+      0.960428238, -2.11983275, 8.18105602, -6.72609901, -5.46944714,
+      0.204244614, 0.0900330544, 8.86620903, 4.63697529, 3.19756651,
+      2.99392676}},
+    {{9.52539158, -4.3840766, -6.94514465, -2.75913763, -10.8364506,
+      -3.95606327, 2.43603897, -5.78482246, -0.801304817, 8.23436832,
+      -7.11484337, 2.53943753, -0.652261257, 9.77392, 3.53345847, -9.62052822,
+      16.0471916},
+     {6.89768124, 2.36394405, -2.08569574, -0.682706833, 3.38872, -6.28313875,
+      4.79594612, 4.93417454, -6.40791416, -10.7355442, -5.66094208, 2.44881392,
+      1.99794042, -9.19855404, -4.02383137, -3.63013959, -5.65853405}},
+    {{1.64614546, -3.93421197, -0.48935914, 5.48284435, -7.69781828, 11.8203125,
+      1.81672478, -1.42535269, -5.26496315, -5.31612349, -4.19499826,
+      7.06049395, 0.18029356, -0.0519902706, 10.317358, 2.19345617, 3.5296216},
+     {7.52353811, 3.56836724, 0.414305687, 0.340799928, 2.44263697, 7.52111912,
+      0.246491909, -11.1172791, -3.82061529, 3.24794388, 0.751524329,
+      3.14019632, 6.33881855, -0.169233799, 7.82640171, 1.5389179, 8.15851307}},
+    {{-2.48950672, -8.55112743, 8.04663277, -5.77116871, -0.637019753,
+      -7.65882111, -7.49037457, 3.8041625, -3.57038307, 9.37715435, -6.42604256,
+      1.62610793, -1.54000568, 2.52110147, 5.30775261, -4.10454893,
+      -4.96251774},
+     {-2.95554614, -5.18210888, 1.00015664, -4.03864431, -7.14954519,
+      5.99929142, 5.86350155, 2.03810191, -4.23009968, 9.39885902, -5.68198299,
+      2.72845244, 11.7133255, 0.838779449, -13.2235403, 2.94607735,
+      -2.7902379}},
+    {{2.86876941, -0.836064458, -0.374509573, -0.277966499, 3.20654631,
+      -3.68510771, -7.76134634, 2.23905277, -8.35530376, 5.25071716,
+      -1.38490796, -2.93542218, 0.509032726, -3.57361269, -2.82580233,
+      -4.49954033, 2.91235542},
+     {-4.37938213, 4.78577232, 2.03453469, 5.48564529, -1.05589461, -1.65940428,
+      4.0130887, 5.26074123, 4.67537832, 0.791350365, 6.3880868, 2.50402451,
+      7.6603322, -3.16343474, -2.71949649, 4.61576128, 1.3817997}},
+    {{0.289200783, 7.06031752, -1.15099299, -5.29136801, -1.343642, -8.36283112,
+      4.13158274, -1.93137062, 3.16199875, 2.21854591, 2.18270063, 0.77002573,
+      6.90393353, -0.644045949, -5.62211609, -1.09085155, 1.07821059},
+     {-3.04716778, -2.52233481, -5.99031925, 2.80152273, 0.340899587,
+      0.667474508, -2.39674735, 8.83768654, -5.45613146, -1.55994594, -2.216362,
+      1.49354, -4.27255821, -9.05310917, 5.90691471, -1.29772806, -8.50278}},
+    {{-3.1383903, -7.71573353, 3.38072681, 6.07642221, -2.39587545, -7.84178352,
+      -1.60108304, -8.6121521, -5.151721, 4.17612457, -2.86532378, 1.64645958,
+      -0.37970829, -4.34561253, -0.454322815, 0.331385136, -5.74550819},
+     {4.77026033, -5.51171303, -7.38155365, -5.38462543, 2.95842505, 5.18372536,
+      0.521988213, 7.23966122, -4.90852165, 7.18465281, 2.99289083, 10.0519466,
+      -2.09695673, 7.34368706, -2.40495348, 3.61603308, 0.131510735}},
+};
+
+// Layer 0, QHead 0
+const float kGoldenQ[kNumTokens][kQBatchSize][kDimsToCompare] = {
+    {{-0.574401975, 0.370210886, -0.426894158, -0.543187439, -0.0266762674,
+      -0.177960411, -0.00839618221, 0.411925405, 0.536462784, 0.528389931,
+      -0.499812007, -0.123897657, -0.0170236826, 0.266041577, -0.0781469196,
+      -0.44081074, 0.185976267},
+     {0.270543516, -0.109283224, -0.58602041, -0.358663559, -0.393124342,
+      -0.0895933211, -0.632167816, 0.386703, 0.314152211, 0.0554139167,
+      0.0241559595, -0.194484815, 0.143893063, 0.103837147, -0.384245932,
+      -0.00418212265, 0.385817379}},
+    {{-0.0331106335, -0.100827977, 0.322449774, 0.225943685, -0.384854138,
+      -0.208085626, 0.0206767023, 0.287796348, -0.139513299, 0.255447835,
+      -0.0845065042, -0.0619940236, 0.477489054, 0.517492294, -0.0172665715,
+      -0.0302075297, 0.365989387},
+     {-0.0266781822, -0.453293771, 0.560033202, 0.105156079, -0.35259968,
+      0.711447716, -0.253611088, 0.0487165749, -0.086192511, -0.0338740349,
+      -0.655441046, 0.00413730741, -0.510472536, -0.0748229772, -0.29113093,
+      -0.0432077348, 0.09223634}},
+    {{-0.321974993, -0.466039479, 0.207254037, -0.126807183, -0.192775592,
+      -0.0953654051, 0.209789664, 0.405356169, -0.00627984107, -0.0590961352,
+      0.0907663852, -0.190793216, -0.730463982, 0.340142608, -0.295675993,
+      -0.165913597, -0.233714506},
+     {-0.345578939, 0.394073665, 0.299743414, -0.0075177839, -0.288939595,
+      0.127782941, -0.207550645, 0.0655022636, -0.705084503, -0.241842598,
+      0.333820701, 0.217911497, 0.29735288, 0.0147881694, -0.152306199,
+      -0.589594781, -0.373093933}},
+    {{0.216089666, 0.0918798149, 0.0560657382, -0.157523662, -0.00141695142,
+      0.51770103, 0.596379519, -0.271057904, 0.241035417, -0.275827706,
+      0.112851456, 0.026878573, -0.579843462, -0.5116328, 0.192026839,
+      0.125176072, 0.34234497},
+     {-0.0744233653, 0.180814236, 0.170143247, -0.337861449, -0.175804421,
+      0.213403732, -0.173699334, 0.109528325, -0.385727316, 0.109683953,
+      0.475667775, 0.253016889, 0.477347463, 0.111096457, 0.394625545,
+      0.0172286481, -0.357992649}},
+    {{-0.350524545, -0.142550975, -0.212269634, -0.0589753427, -0.434021264,
+      0.384472728, 0.445421219, -0.635599554, -0.246593416, 0.120986834,
+      0.623568773, -0.161932915, -0.702406883, 0.44038102, 0.268234134,
+      0.480264157, 0.103595078},
+     {-0.227436215, 0.357608706, -0.25339672, -0.0683218762, -0.179259315,
+      0.23657614, 0.559984326, 0.165754288, -0.0402980596, -0.101906747,
+      -0.278261065, -0.16327399, 0.235923961, -0.428657919, -0.290629387,
+      0.579215467, -0.0717103705}},
+    {{-0.246389642, -0.266164362, -0.0967710763, -0.4011603, 0.242542207,
+      0.0869855583, 0.20158039, 0.207793877, -0.0875666738, -0.242263764,
+      -0.0462955758, -0.617374003, 0.454443514, 0.207072973, -0.0235372931,
+      -0.0193868056, -0.660622239},
+     {0.703284621, 0.0382430181, 0.43997851, -0.858277559, 0.342218578,
+      0.414044619, 0.403636098, -0.579880178, -1.12243, -0.112913512,
+      0.629238605, -0.0285760984, -0.152203664, -0.088969171, -0.0681343,
+      0.476349175, 0.283238202}},
+    {{0.138267457, 0.483219147, 0.230450034, -0.568304598, 0.204461277,
+      -0.286731184, -0.416590065, -0.483460307, -0.561008453, 0.395195067,
+      0.104367018, -0.196090236, -0.324770749, -0.0881370157, -0.626873195,
+      0.0936089084, 0.262185335},
+     {0.282603383, 0.0723766163, -0.206548154, 0.561849833, 0.482716829,
+      0.135281503, -0.438841999, 0.472577304, -0.346201897, -0.0211652666,
+      -0.0905084163, -0.168639392, -0.154975936, -0.303443581, -0.41771856,
+      0.400717318, 0.426146686}},
+    {{-0.0537007451, -0.227346331, -0.2871463, 0.247746795, -0.0975416005,
+      -0.0123391449, 0.0612513907, -0.374673814, 0.283457696, 0.40945363,
+      0.137944818, -0.0119741419, 0.775918365, -0.308365196, 0.230615795,
+      -0.440364927, 0.218536288},
+     {0.0688965544, -0.149037778, -0.246169299, 0.0599289536, -0.456733435,
+      0.0808929354, 0.115154952, 0.0997388735, -0.408117741, 0.576600909,
+      -0.193775773, 0.0340575948, -0.29254055, 0.695465446, 0.373336494,
+      0.421431482, 0.00197479129}},
+    {{0.402076721, -0.118151993, 0.542394996, 0.0382412486, -0.614983976,
+      0.28617692, 0.318540633, -0.299300969, -0.177486539, 0.394140214,
+      0.0644133314, -0.0321308076, 0.671587527, -0.0173831787, -0.219400048,
+      -0.340277791, 0.5130288},
+     {0.105372488, -0.145784974, 0.0695323348, -0.106080391, -0.755512118,
+      0.975362539, -0.15056029, 0.58882606, -0.059625227, -0.810613,
+      -0.321623206, 0.193939567, 0.0340242684, -0.626081824, 0.109950632,
+      -0.141072854, 0.0177994221}},
+    {{0.243249148, 0.0904035419, -0.472183734, -0.176162, 0.314925164,
+      -0.191137731, 0.492265761, -0.0120046511, 0.824757636, 0.298175,
+      0.148151726, -0.0197859108, -0.64297086, 0.432318538, -0.555079758,
+      0.101636633, 0.155741245},
+     {0.0523641109, 0.224086404, 0.0143201668, 0.0090854, 0.304901183,
+      -0.391372293, 0.267655343, 0.117368169, 0.645064473, 0.336050332,
+      -0.282133281, -0.231817603, 0.376230389, -0.575031936, -0.628365576,
+      0.484799922, 0.0824087635}},
+};
+
+void RunAttentionTest(AttentionImpl attention_impl) {
+  TestState state;
+  TestModelState model_state(state);
+  TestAttentionState attention_state(state, model_state, kNumTokens,
+                                     kQBatchSize, attention_impl);
+
+  GemmaAttention(attention_state.tokens.size(), 0, model_state.layer,
+                 attention_state.attention, *attention_state.qbatch, state.env,
+                 AttentionImplToFlags(attention_impl, HWY_NATIVE_DOT_BF16));
+
+  CompareAttSumsWithGolden(attention_state.attention, kGoldenAttSums);
+  CompareKVCacheWithGolden(model_state.config,
+                           hwy::Span<KVCache>(attention_state.kv_caches.data(),
+                                              attention_state.kv_caches.size()),
+                           /*layer=*/0, /*kv_head=*/0, kGoldenK, kGoldenV);
+  CompareQVecsWithGolden(model_state.config, attention_state.attention,
+                         /*q_head=*/0, kGoldenQ);
+}
+
+void TestGemmaAttentionOld() { RunAttentionTest(AttentionImpl::kOld); }
+
+void TestGemmaAttentionFlash() { RunAttentionTest(AttentionImpl::kFlash); }
+
+}  // namespace HWY_NAMESPACE
+}  // namespace gcpp
+HWY_AFTER_NAMESPACE();
+
+#if HWY_ONCE
+
+namespace gcpp {
+HWY_BEFORE_TEST(AttentionTest);
+HWY_EXPORT_AND_TEST_P(AttentionTest, TestGemmaAttentionOld);
+HWY_EXPORT_AND_TEST_P(AttentionTest, TestGemmaAttentionFlash);
+HWY_AFTER_TEST();
+
+}  // namespace gcpp
+
+#endif
diff --git a/gemma/bindings/context.cc b/gemma/bindings/context.cc
index 5741d70..5db3adc 100644
--- a/gemma/bindings/context.cc
+++ b/gemma/bindings/context.cc
@@ -73,45 +73,38 @@ GemmaContext* GemmaContext::Create(const char* tokenizer_path,
   ThreadingArgs threading_args;
   threading_args.spin = gcpp::Tristate::kFalse;
 
-  LoaderArgs loader(tokenizer_path, weights_path);
-  LogDebug("LoaderArgs created");
+  threading_args.spin = gcpp::Tristate::kFalse;
+  GemmaArgs args(LoaderArgs(tokenizer_path, weights_path), threading_args);
 
   // Initialize cached args
   LogDebug("Initializing inference args");
-  InferenceArgs inference_args;
-  inference_args.Init();
-  inference_args.max_generated_tokens = max_generated_tokens;
-  inference_args.temperature = 0.7f;
-  inference_args.top_k = 1;
-  inference_args.deterministic = false;
+  args.inference.max_generated_tokens = max_generated_tokens;
+  args.inference.temperature = 0.7f;
+  args.inference.top_k = 1;
+  args.inference.deterministic = false;
 
   ss.str("");
   ss << "Inference args initialized with max_tokens: " << max_generated_tokens
-     << ", temperature: " << inference_args.temperature
-     << ", top_k: " << inference_args.top_k << ", deterministic: "
-     << (inference_args.deterministic ? "true" : "false");
+     << ", temperature: " << args.inference.temperature
+     << ", top_k: " << args.inference.top_k << ", deterministic: "
+     << (args.inference.deterministic ? "true" : "false");
   LogDebug(ss.str().c_str());
 
-  return new GemmaContext(loader, inference_args, threading_args,
-                          max_generated_tokens);
+  return new GemmaContext(args, max_generated_tokens);
 }
 
-GemmaContext::GemmaContext(const LoaderArgs& loader,
-                           const InferenceArgs& inference_args,
-                           const ThreadingArgs& threading_args,
-                           int max_generated_tokens)
-    : inference_args(inference_args),
-      threading_args(threading_args),
-      ctx(threading_args),
+GemmaContext::GemmaContext(const GemmaArgs& args, int max_generated_tokens)
+    : args(args),
+      ctx(args.threading),
       matmul_env(ctx),
       active_conversation_name("default"),
-      model(loader, inference_args, matmul_env.ctx) {
+      model(args, matmul_env.ctx) {
   std::stringstream ss;
 
   LogDebug("Creating initial ConversationData");
   // Create the initial ConversationData object using make_shared
   active_conversation = std::make_shared<ConversationData>(
-      model.Config(), inference_args, ctx.allocator);
+      model.Config(), args.inference, ctx.allocator);
 
   LogDebug(
       "Storing initial ConversationData in conversation_cache[\"default\"]");
@@ -172,8 +165,8 @@ int GemmaContext::GenerateInternal(const char* prompt_string,
   // set up runtime config
   TimingInfo timing_info = {};
   RuntimeConfig runtime_config = {.stream_token = stream_token,
-                                  .use_spinning = threading_args.spin};
-  inference_args.CopyTo(runtime_config);
+                                  .use_spinning = args.threading.spin};
+  args.inference.CopyTo(runtime_config);
   size_t prefix_end = 0;
 
   const ModelConfig& model_config = model.Config();
@@ -247,7 +240,7 @@ int GemmaContext::GenerateInternal(const char* prompt_string,
                  timing_info);
 
   // prepare for next turn
-  if (!inference_args.multiturn ||
+  if (!args.inference.multiturn ||
       model_config.wrapping == PromptWrapping::PALIGEMMA) {
     // If not multiturn, or Paligemma (which handles turns differently),
     // reset the *active* conversation's position.
diff --git a/gemma/bindings/context.h b/gemma/bindings/context.h
index 00648fc..5aa3412 100644
--- a/gemma/bindings/context.h
+++ b/gemma/bindings/context.h
@@ -53,8 +53,7 @@ typedef void (*GemmaLogCallback)(const char* message, void* user_data);
 
 class GemmaContext {
  private:
-  GemmaContext(const LoaderArgs& loader, const InferenceArgs& inference_args,
-               const ThreadingArgs& threading_args, int max_generated_tokens);
+  GemmaContext(const GemmaArgs& args, int max_generated_tokens);
 
  public:
   static GemmaContext* Create(const char* tokenizer_path,
@@ -81,37 +80,37 @@ class GemmaContext {
 
   // Set max generated tokens
   void SetMaxGeneratedTokens(size_t value) {
-    inference_args.max_generated_tokens = value;
+    args.inference.max_generated_tokens = value;
     LogDebug("Setting max_generated_tokens to configured value");
   }
 
   // Set multiturn flag (0 = disabled, 1 = enabled)
   void SetMultiturn(int value) {
-    inference_args.multiturn = value;
+    args.inference.multiturn = value;
     LogDebug("Setting multiturn to configured value");
   }
 
   // Set temperature for token generation
   void SetTemperature(float value) {
-    inference_args.temperature = value;
+    args.inference.temperature = value;
     LogDebug("Setting temperature to configured value");
   }
 
   // Set top_k parameter for sampling
   void SetTopK(int value) {
-    inference_args.top_k = value;
+    args.inference.top_k = value;
     LogDebug("Setting top_k to configured value");
   }
 
   // Set deterministic flag
   void SetDeterministic(bool value) {
-    inference_args.deterministic = value;
+    args.inference.deterministic = value;
     LogDebug("Setting deterministic flag to configured value");
   }
 
   // Set prefill_tbatch_size
   void SetPrefillTbatchSize(size_t value) {
-    inference_args.prefill_tbatch_size = value;
+    args.inference.prefill_tbatch_size = value;
     LogDebug("Setting prefill_tbatch_size to configured value");
   }
 
@@ -175,7 +174,7 @@ class GemmaContext {
       active_conversation->abs_pos = 0;
       // Replace the cache within the current ConversationData object
       active_conversation->kv_cache = std::make_unique<KVCache>(
-          model.Config(), inference_args, ctx.allocator);
+          model.Config(), args.inference, ctx.allocator);
 
       LogDebug((log_prefix + "Successfully rewound to initial state.").c_str());
     } else {
@@ -193,7 +192,7 @@ class GemmaContext {
     LogDebug("Creating new conversation");
     // Create a new ConversationData object using make_shared
     conversation_cache[name] = std::make_shared<ConversationData>(
-        model.Config(), inference_args, ctx.allocator);
+        model.Config(), args.inference, ctx.allocator);
     return true;
   }
 
@@ -274,8 +273,7 @@ class GemmaContext {
   std::vector<int> token_buffer;
 
   // Cached args (remain global for the context)
-  InferenceArgs inference_args;
-  ThreadingArgs threading_args;
+  GemmaArgs args;
   ThreadingContext ctx;
   MatMulEnv matmul_env;
 
diff --git a/gemma/configs.cc b/gemma/configs.cc
index 8856203..cb508e8 100644
--- a/gemma/configs.cc
+++ b/gemma/configs.cc
@@ -22,8 +22,8 @@
 #include <vector>
 
 #include "compression/types.h"  // Type
-#include "io/fields.h"           // IFields
-#include "io/io.h"               // Path
+#include "io/fields.h"          // IFields
+#include "io/io.h"              // Path
 #include "hwy/base.h"
 
 namespace gcpp {
@@ -238,6 +238,7 @@ static ModelConfig ConfigGemma3_1B() {
   config.display_name = "Gemma3_1B";
   config.model = Model::GEMMA3_1B;
   config.wrapping = PromptWrapping::GEMMA_VLM;
+  config.use_global_timescale = true;
   config.model_dim = 1152;
   config.vocab_size = kGemmaV3VocabSize;  // new vocab size / tokenizer
   config.max_seq_len = 32 * 1024;
@@ -288,6 +289,7 @@ static ModelConfig ConfigGemma3_4B() {
   config.display_name = "Gemma3_4B";
   config.model = Model::GEMMA3_4B;
   config.wrapping = PromptWrapping::GEMMA_VLM;
+  config.use_global_timescale = true;
   AddVitConfig(config, /*image_size=*/896);
   config.vocab_size = kGemmaV3VocabSize;
   config.vit_config.pool_dim = 4;
@@ -337,6 +339,7 @@ static ModelConfig ConfigGemma3_12B() {
   config.display_name = "Gemma3_12B";
   config.model = Model::GEMMA3_12B;
   config.wrapping = PromptWrapping::GEMMA_VLM;
+  config.use_global_timescale = true;
   AddVitConfig(config, /*image_size=*/896);
   config.vocab_size = kGemmaV3VocabSize;
   config.vit_config.pool_dim = 4;
@@ -386,6 +389,7 @@ static ModelConfig ConfigGemma3_27B() {
   config.display_name = "Gemma3_27B";
   config.model = Model::GEMMA3_27B;
   config.wrapping = PromptWrapping::GEMMA_VLM;
+  config.use_global_timescale = true;
   AddVitConfig(config, /*image_size=*/896);
   config.vocab_size = kGemmaV3VocabSize;
   config.vit_config.pool_dim = 4;
@@ -495,19 +499,19 @@ const char* ModelPrefix(Model model) {
 }
 
 PromptWrapping ChooseWrapping(const Model model, Tristate wrapping) {
-  if (IsPaliGemma(model)) {
+  const PromptWrapping config_wrapping = ConfigFromModel(model).wrapping;
+
+  // For models with a fixed wrapping mode, ignore user override.
+  if (config_wrapping == PromptWrapping::PALIGEMMA ||
+      config_wrapping == PromptWrapping::GEMMA_VLM) {
     if (wrapping != Tristate::kDefault) {
-      HWY_WARN("Ignoring unnecessary --wrapping for PaliGemma models.");
+      HWY_WARN("Ignoring unnecessary --wrapping for model %s.",
+               ModelPrefix(model));
     }
-    return PromptWrapping::PALIGEMMA;
+    return config_wrapping;
   }
-  if (IsVLM(model)) {
-    if (wrapping != Tristate::kDefault) {
-      HWY_WARN("Ignoring unnecessary --wrapping for VLM models.");
-    }
-    return PromptWrapping::GEMMA_VLM;
-  }
-  // Default to IT unless --wrapping=0.
+
+  // For other models, default to IT unless --wrapping=0 is passed.
   return wrapping == Tristate::kFalse ? PromptWrapping::GEMMA_PT
                                       : PromptWrapping::GEMMA_IT;
 }
@@ -674,7 +678,9 @@ Model DeduceModel(const Path& blob_path, size_t layers, int layer_types) {
       return Model::GEMMA3_270M;
 
     case 26:
-      if (layer_types & kDeducedViT) return Model::GEMMA3_1B;
+      if (layer_types & (kDeducedViT|kDeducedKqNorm)) {
+        return Model::GEMMA3_1B;
+      }
       return Model::GEMMA2_2B;
     case 27:
       return (layer_types & kDeduced448) ? Model::PALIGEMMA2_3B_448
@@ -706,4 +712,11 @@ Model DeduceModel(const Path& blob_path, size_t layers, int layer_types) {
   }
 }
 
+AttentionImpl GetAttentionImpl(const std::string& impl) {
+  if (impl == "old") return AttentionImpl::kOld;
+  if (impl == "flash") return AttentionImpl::kFlash;
+  HWY_WARN("Unknown attention implementation: %s. Using kOld.\n", impl.c_str());
+  return AttentionImpl::kOld;
+}
+
 }  // namespace gcpp
diff --git a/gemma/configs.h b/gemma/configs.h
index 275f374..b727480 100644
--- a/gemma/configs.h
+++ b/gemma/configs.h
@@ -80,6 +80,38 @@ static inline bool EnumValid(LayerAttentionType type) {
   return type == LayerAttentionType::kGemma || type == LayerAttentionType::kVit;
 }
 
+enum class AttentionImpl {
+  kOld,
+  kFlash,
+  kSentinel,
+};
+
+AttentionImpl GetAttentionImpl(const std::string& impl);
+
+/*
+ * Returns a bitmask of flags to pass to attention functions based on the
+ * attention implementation selected.
+ *
+ * If `hwy_native_dot_bf16` is true, the function will use the old attention
+ * implementation, ignoring `impl`.
+ *
+ * `hwy_native_dot_bf16` needs to be passed in, because the HWY_NATIVE_DOT_BF16
+ * macro is not available outside of highway instrumented translation units and
+ * cannot be made accessible from .h files.
+ */
+static inline int AttentionImplToFlags(AttentionImpl impl,
+                                       int hwy_native_dot_bf16) {
+  if (hwy_native_dot_bf16) return kAttentionUseOld;
+
+  switch (impl) {
+    case AttentionImpl::kOld:
+      return kAttentionUseOld;
+    case AttentionImpl::kFlash:
+    default:
+      return 0;
+  }
+}
+
 // Post attention and ffw normalization type.
 enum class PostNormType {
   None,
@@ -184,13 +216,6 @@ enum class Model {
 // in Specifier and thus does not change.
 const char* ModelPrefix(Model model);
 
-// Gemma3 is multimodal and has a different prompt wrapping than PaliGemma.
-// This is used for deducing the PromptWrapping for pre-2025 BlobStore.
-static inline bool IsVLM(Model model) {
-  return model == Model::GEMMA3_4B || model == Model::GEMMA3_1B ||
-         model == Model::GEMMA3_12B || model == Model::GEMMA3_27B;
-}
-
 static inline bool IsPaliGemma(Model model) {
   if (model == Model::PALIGEMMA2_3B_224 || model == Model::PALIGEMMA2_3B_448 ||
       model == Model::PALIGEMMA2_10B_224 ||
@@ -280,7 +305,7 @@ struct LayerConfig : public IFields {
   uint32_t kv_heads = 0;
   uint32_t qkv_dim = 0;  // length of Q, K, V vectors (contiguous).
   bool ff_biases = false;
-  bool optimized_gating = true;             // for Gemma3
+  bool optimized_gating = true;  // for Gemma3
   PostNormType post_norm = PostNormType::None;
   LayerAttentionType type = LayerAttentionType::kGemma;
   ActivationType activation = ActivationType::Gelu;
@@ -383,6 +408,8 @@ struct ModelConfig : public IFields {
 
     internal.VisitFields(visitor);
 
+    visitor(use_global_timescale);
+
     // Append new fields here, then update `python/configs.cc`.
   }
 
@@ -481,6 +508,7 @@ struct ModelConfig : public IFields {
   std::vector<std::string> scale_base_names;
 
   InternalModelConfig internal;
+  bool use_global_timescale = false;  // for Gemma 3
 };
 
 // Returns the sub-config for the ViT model of the PaliGemma model.
@@ -489,6 +517,7 @@ ModelConfig GetVitConfig(const ModelConfig& config);
 enum DeducedLayerTypes {
   kDeducedViT = 2,
   kDeduced448 = 4,   // For ViT, 448x448 resolution instead of 224x224.
+  kDeducedKqNorm = 8,
 };
 
 // layer_types is one or more of `DeducedLayerTypes`.
diff --git a/gemma/flash_attention.cc b/gemma/flash_attention.cc
index bf3aede..671efb4 100644
--- a/gemma/flash_attention.cc
+++ b/gemma/flash_attention.cc
@@ -17,12 +17,18 @@
 #include <stdint.h>
 
 #include <algorithm>
+#include <array>
 #include <cmath>
+#include <cstdlib>
+#include <iostream>
 #include <limits>
+#include <vector>
 
 #include "compression/types.h"  // GEMMA_DISABLED_TARGETS
+#include "gemma/flash_structs.h"
 #include "util/threading_context.h"
 #include "util/zones.h"
+#include "hwy/base.h"
 #ifndef HWY_DISABLED_TARGETS
 #define HWY_DISABLED_TARGETS GEMMA_DISABLED_TARGETS
 #endif  // HWY_DISABLED_TARGETS
@@ -30,7 +36,6 @@
 #include "gemma/activations.h"
 #include "gemma/configs.h"  // kMaxQKVDim
 #include "gemma/gemma.h"
-#include "gemma/weights.h"
 #include "util/threading.h"
 #include "hwy/profiler.h"
 
@@ -59,7 +64,7 @@ static constexpr size_t kNFx8HTileSize = 8;
 // q has shape [batch, qbatch][head, qkv_dim].
 // q_t has shape [qkv_dim][qbatch, head, batch] in order to make the maximum
 // possible consecutive elements have the same KV.
-static void TransposeQ(const MatPtrT<float>& q, MatPtrT<float>& q_t,
+static void TransposeQ(const MatPtrT<float>& q, MatPtrT<BF16>& q_t,
                        const size_t qbatch_size, ThreadingContext& ctx) {
   // Group floats by the number of floats in a cache line.
   const size_t kNF = ctx.cache_info.LineBytes() / sizeof(float);
@@ -70,12 +75,13 @@ static void TransposeQ(const MatPtrT<float>& q, MatPtrT<float>& q_t,
     for (size_t lane = 0; lane < kNF; ++lane) {
       size_t q_row = task * kNF + lane;
       if (q_row >= q_t.Rows()) break;
-      float* HWY_RESTRICT qt_row = q_t.Row(q_row);
+      BF16* HWY_RESTRICT qt_row = q_t.Row(q_row);
       for (size_t qi = 0; qi < qbatch_size; ++qi) {
         for (size_t h = 0; h < num_heads; ++h) {
           for (size_t b = 0; b < batch_size; ++b) {
             qt_row[(qi * num_heads + h) * batch_size + b] =
-                q.Row(b * qbatch_size + qi)[h * q_t.Rows() + q_row];
+                hwy::ConvertScalarTo<BF16>(
+                    q.Row(b * qbatch_size + qi)[h * q_t.Rows() + q_row]);
           }
         }
       }
@@ -84,45 +90,48 @@ static void TransposeQ(const MatPtrT<float>& q, MatPtrT<float>& q_t,
   {
     const size_t num_tasks = hwy::DivCeil(q_t.Rows(), kNF);
     // Better than kFlat.
-    ParallelFor(ParallelismStrategy::kHierarchical, num_tasks, ctx,
+    ParallelFor(Parallelism::kHierarchical, num_tasks, ctx,
                 /*cluster_idx=*/0, Callers::kFlashTransposeQ, func);
   }
 }
 
 // Updates q in place for RMSNorm and positional encoding.
 void RMSNormAndPositionalEncoding(const size_t num_tokens, const QBatch& qbatch,
-                                  MatPtrT<KV_t>& q, const size_t layer_idx,
-                                  const LayerWeightsPtrs& layer,
-                                  const AttentionActivations& activations,
+                                  MatPtrT<float>& q,
+                                  const MatPtr& query_norm_scale,
+                                  const size_t layer_idx,
+                                  const AttentionActivationsPtrs& activations,
                                   ThreadingContext& ctx) {
+  const LayerConfig& layer_config = activations.config.layer_configs[layer_idx];
   const float query_scale = activations.query_scale;
   const hwy::Divisor div_qbatch(qbatch.Size());
   const auto func = [&](const size_t task, size_t worker) HWY_ATTR {
     GCPP_ZONE(ctx, worker, Zones::kFlashAttentionRmsNormAndPositionalEncoding);
     size_t qi = div_qbatch.Remainder(task);
     size_t batch_idx = div_qbatch.Divide(task);
-    for (size_t h = 0; h < layer.layer_config.heads; ++h) {
+    for (size_t h = 0; h < layer_config.heads; ++h) {
       const size_t tq_idx = qbatch.Size() * batch_idx + qi;
       // Find the token position in the query and calculate
       // the range of cache positions to attend to.
-      const size_t pos = qbatch.Pos(qi) + batch_idx;
-      float* HWY_RESTRICT q_row =
-          q.Row(tq_idx) + h * layer.layer_config.qkv_dim;
+      constexpr size_t offset = 0;  // placeholder, do not remove
+      const size_t pos =
+          qbatch.Pos(qi) + batch_idx + offset;
+      float* HWY_RESTRICT q_row = q.Row(tq_idx) + h * layer_config.qkv_dim;
       // Apply rope and scaling to Q.
-      if (layer.query_norm_scale.HasPtr()) {
-        CallUpcasted(&layer.query_norm_scale, [&](const auto* weights_t) {
+      if (query_norm_scale.HasPtr()) {
+        CallUpcasted(&query_norm_scale, [&](const auto* weights_t) {
           RMSNormInplace(weights_t->PackedScale1(), /*w_ofs=*/0, q_row,
-                         layer.layer_config.qkv_dim, ctx, worker);
+                         layer_config.qkv_dim, ctx, worker);
         });
       }
-      PositionalEncodingQK(q_row, layer_idx, layer, activations, ctx, worker,
-                           pos, query_scale);
+      PositionalEncodingQK(q_row, layer_idx, activations, ctx, worker, pos,
+                           query_scale);
     }
   };
   {
     // kHierarchical is not worth the extra sync overhead because the tasks are
     // very lightweight.
-    ParallelFor(ParallelismStrategy::kFlat, num_tokens * qbatch.Size(), ctx,
+    ParallelFor(Parallelism::kFlat, num_tokens * qbatch.Size(), ctx,
                 /*cluster_idx=*/0, Callers::kFlashRMSNormAndPositionalEncoding,
                 func);
   }
@@ -152,15 +161,20 @@ void HWY_INLINE SingleFlashAttentionStep(float x, float cap, float& old_max,
 
 // Calculates the complete attention outputs for a single row of q.
 void SingleFlashAttention(const size_t start_pos, const size_t last_pos,
-                          const float* HWY_RESTRICT q, const MatPtrT<KV_t>& k,
+                          const BF16* HWY_RESTRICT q, const MatPtrT<KV_t>& k,
                           const MatPtrT<KV_t>& v, const size_t layer_idx,
-                          const LayerWeightsPtrs& layer,
-                          const AttentionActivations& activations,
+                          const AttentionActivationsPtrs& activations,
                           float* HWY_RESTRICT att_out, ThreadingContext& ctx,
                           const size_t worker) {
   GCPP_ZONE(ctx, worker, Zones::kFlashAttentionSingleFlashAttention);
+  const hn::ScalableTag<BF16> dbf;
+  const size_t qkv_dim = k.Cols();
+
   const size_t pos_mod = activations.div_seq_len.Remainder(start_pos);
-  float m = Dot(q, k.Row(pos_mod), k.Cols());
+  // TODO: Mixed-mode can be further improved for Turin: we can demote right
+  // before we do the dot product instruction, rather than promote both to f32.
+  // But some potential accuracy loss there, needs evaluation first.
+  float m = Dot(dbf, MakeConstSpan(q, qkv_dim), 0, k.Row(pos_mod), qkv_dim);
   if (float cap = activations.config.att_cap; cap > 0.0f) {
     // Compute tanh(x / cap) * cap, being LogitsSoftCap on the scalar x.
     m = cap * std::tanh(m / cap);
@@ -170,7 +184,7 @@ void SingleFlashAttention(const size_t start_pos, const size_t last_pos,
   MulByConstTo(d, v.Row(pos_mod), att_out, v.Cols(), ctx, worker);
   for (size_t pos = start_pos + 1; pos <= last_pos; ++pos) {
     const size_t pos_mod = activations.div_seq_len.Remainder(pos);
-    float x = Dot(q, k.Row(pos_mod), k.Cols());
+    float x = Dot(dbf, MakeConstSpan(q, qkv_dim), 0, k.Row(pos_mod), qkv_dim);
     SingleFlashAttentionStep(x, activations.config.att_cap, m, d,
                              v.Row(pos_mod), v.Cols(), att_out);
   }
@@ -180,25 +194,27 @@ void SingleFlashAttention(const size_t start_pos, const size_t last_pos,
 // the dot products of NF rows of Q for a single K timestep.
 template <class DF, class VF = hn::Vec<DF>>
 VF QDotKVector(DF df, const uint32_t* HWY_RESTRICT q_offsets,
-               const size_t k_pos, const MatPtrT<KV_t>& q,
+               const size_t k_pos, const MatPtrT<BF16>& q,
                const MatPtrT<KV_t>& k) {
+  const hn::ScalableTag<BF16> dbf;
+  const size_t qkv_dim = k.Cols();
+
   hn::TFromD<DF> results[hn::MaxLanes(df)];
   for (size_t i = 0; i < hn::Lanes(df); ++i) {
-    results[i] = Dot(q.Row(0) + q_offsets[i], k.Row(k_pos), k.Cols());
+    results[i] = Dot(dbf, MakeConstSpan(q.Row(0) + q_offsets[i], qkv_dim), 0,
+                     k.Row(k_pos), qkv_dim);
   }
   return hn::LoadU(df, results);
 }
 
-// Returns an NF Q rows by 8 K rows tile of Q.K dot products, in single
-// precision.
+// Returns an NF Q rows by 8 K rows tile of Q.K dot products.
 // This is the result of NF rows of Q against 8 K timesteps, with positions
 // given by k_pos[0..7]. Q has been transposed so that the NF rows are read in
 // consecutive elements, and other columns by adding q_stride.
 template <class DF, class VF = hn::Vec<DF>>
-void QDotKTileFloat(DF df, const float* HWY_RESTRICT q, const size_t q_stride,
-                    const MatPtrT<KV_t>& k, const size_t* k_pos, VF& sum0,
-                    VF& sum1, VF& sum2, VF& sum3, VF& sum4, VF& sum5, VF& sum6,
-                    VF& sum7) {
+void QDotKTile(DF df, const BF16* HWY_RESTRICT q, const size_t q_stride,
+               const MatPtrT<KV_t>& k, const size_t* k_pos, VF& sum0, VF& sum1,
+               VF& sum2, VF& sum3, VF& sum4, VF& sum5, VF& sum6, VF& sum7) {
   constexpr size_t kHTileSize = kNFx8HTileSize;
   sum0 = hn::Zero(df);
   sum1 = hn::Zero(df);
@@ -209,11 +225,16 @@ void QDotKTileFloat(DF df, const float* HWY_RESTRICT q, const size_t q_stride,
   sum6 = hn::Zero(df);
   sum7 = hn::Zero(df);
   const float* HWY_RESTRICT k_row[kHTileSize];
-  for (int i = 0; i < kHTileSize; ++i) {
+  for (size_t i = 0; i < kHTileSize; ++i) {
     k_row[i] = k.Row(k_pos[i]);
   }
+
+  const hn::Rebind<BF16, DF> dbfh;
+  using VBF = hn::Vec<decltype(dbfh)>;
+
   for (size_t i = 0; i < k.Cols(); ++i) {
-    VF q_vec = hn::Load(df, q);
+    const VBF q_vec_bf = hn::Load(dbfh, q);
+    const VF q_vec = hn::PromoteTo(df, q_vec_bf);
     VF k_0 = hn::Set(df, k_row[0][i]);
     sum0 = hn::MulAdd(q_vec, k_0, sum0);
     VF k_1 = hn::Set(df, k_row[1][i]);
@@ -266,31 +287,30 @@ VF HWY_INLINE ElementwiseSumOf8(DF df, const VF& x0, const VF& x1, const VF& x2,
 // min_last_pos, then sweeps the remaining timesteps in the range (min_last_pos,
 // max_last_pos].
 void TileFlashAttention(
-    const MatPtrT<float>& q, const uint32_t* HWY_RESTRICT q_offsets,
-    const StridedView<float>& qT, const MatPtrT<KV_t>& k,
-    const size_t start_pos, const uint32_t* HWY_RESTRICT last_pos,
-    const size_t min_last_pos, const size_t max_last_pos,
-    const MatPtrT<KV_t>& v, const size_t layer_idx,
-    const LayerWeightsPtrs& layer, const AttentionActivations& activations,
-    MatPtrT<float>& att_out, const uint32_t* HWY_RESTRICT out_offsets,
-    ThreadingContext& ctx, const size_t worker) {
+    const MatPtrT<BF16>& q, const uint32_t* HWY_RESTRICT q_offsets,
+    const StridedView<BF16>& qT, const MatPtrT<KV_t>& k, const size_t start_pos,
+    const uint32_t* HWY_RESTRICT last_pos, const size_t min_last_pos,
+    const size_t max_last_pos, const MatPtrT<KV_t>& v, const size_t layer_idx,
+    const AttentionActivationsPtrs& activations, MatPtrT<float>& att_out,
+    const uint32_t* HWY_RESTRICT out_offsets, ThreadingContext& ctx,
+    const size_t worker) {
   GCPP_ZONE(ctx, worker, Zones::kFlashAttentionTileFlashAttention);
-  constexpr int kHTileSize = kNFx8HTileSize;
+  constexpr size_t kHTileSize = kNFx8HTileSize;
   using DF = hn::ScalableTag<float>;
   const DF df;
   using VF = hn::Vec<DF>;
   using DI = hn::ScalableTag<uint32_t>;
   const DI di;
   using VI = hn::Vec<DI>;
-  const int kVTileSize = hn::Lanes(df);
-  for (int i = 0; i < kVTileSize; ++i) {
+  const size_t kVTileSize = hn::Lanes(df);
+  for (size_t i = 0; i < kVTileSize; ++i) {
     hwy::ZeroBytes(att_out.Row(0) + out_offsets[i],
                    v.Cols() * sizeof(att_out.Row(0)[0]));
   }
   VI lasts = hn::LoadU(di, last_pos);
   VF old_m = hn::Set(df, -std::numeric_limits<float>::max() / 2.0f);
   VF old_d = hn::Zero(df);
-  const float* HWY_RESTRICT qT_row = qT.Row(0);
+  const BF16* HWY_RESTRICT qT_row = qT.Row(0);
   const size_t qT_stride = qT.Stride();
   size_t position = start_pos;
   while (position + kHTileSize - 1 <= min_last_pos) {
@@ -299,8 +319,7 @@ void TileFlashAttention(
       k_pos[i] = activations.div_seq_len.Remainder(position + i);
     }
     VF x0, x1, x2, x3, x4, x5, x6, x7;
-    QDotKTileFloat(df, qT_row, qT_stride, k, k_pos, x0, x1, x2, x3, x4, x5, x6,
-                   x7);
+    QDotKTile(df, qT_row, qT_stride, k, k_pos, x0, x1, x2, x3, x4, x5, x6, x7);
     if (activations.config.att_cap > 0.0f) {
       // Compute tanh(x / cap) * cap, being LogitsSoftCap on the tile.
       VF cap = hn::Set(df, activations.config.att_cap);
@@ -374,7 +393,7 @@ void TileFlashAttention(
 // This is the result of 4 rows of Q against NF K timesteps, with positions
 // given by k_offsets[0..NF].
 template <class DF, class VF = hn::Vec<DF>>
-void QDotKTilex4(DF df, const float* HWY_RESTRICT q,
+void QDotKTilex4(DF df, const BF16* HWY_RESTRICT q,
                  const uint32_t* HWY_RESTRICT q_offsets, const MatPtrT<KV_t>& k,
                  const int32_t* HWY_RESTRICT k_offsets, VF& sum0, VF& sum1,
                  VF& sum2, VF& sum3) {
@@ -389,13 +408,13 @@ void QDotKTilex4(DF df, const float* HWY_RESTRICT q,
   VI k_offsets_vec = hn::LoadU(di, k_offsets);
   for (size_t i = 0; i < k.Cols(); ++i) {
     VF k_vec = hn::GatherIndex(df, k_base + i, k_offsets_vec);
-    VF q_0 = hn::Set(df, q[q_offsets[0] + i]);
+    VF q_0 = hn::Set(df, hwy::ConvertScalarTo<float>(q[q_offsets[0] + i]));
     sum0 = hn::MulAdd(q_0, k_vec, sum0);
-    VF q_1 = hn::Set(df, q[q_offsets[1] + i]);
+    VF q_1 = hn::Set(df, hwy::ConvertScalarTo<float>(q[q_offsets[1] + i]));
     sum1 = hn::MulAdd(q_1, k_vec, sum1);
-    VF q_2 = hn::Set(df, q[q_offsets[2] + i]);
+    VF q_2 = hn::Set(df, hwy::ConvertScalarTo<float>(q[q_offsets[2] + i]));
     sum2 = hn::MulAdd(q_2, k_vec, sum2);
-    VF q_3 = hn::Set(df, q[q_offsets[3] + i]);
+    VF q_3 = hn::Set(df, hwy::ConvertScalarTo<float>(q[q_offsets[3] + i]));
     sum3 = hn::MulAdd(q_3, k_vec, sum3);
   }
 }
@@ -410,23 +429,202 @@ float HWY_INLINE SingleFlashAttentionRowVector(DF df, VF& x, float& old_max,
   float scale = old_d * std::exp(old_max - m);
   old_d = hn::ReduceSum(df, x) + scale;
   old_max = m;
-  float one_over_d = 1.0f / old_d;
-  scale *= one_over_d;
-  x = hn::Mul(x, hn::Set(df, one_over_d));
+  if (old_d > 0.0f) {
+    const float one_over_d = 1.0f / old_d;
+    scale *= one_over_d;
+    x = hn::Mul(x, hn::Set(df, one_over_d));
+  } else {
+    scale = 0.0f;
+    x = hn::Zero(df);
+  }
   return scale;
 }
 
-// Sweeps a tile of 4 Q rows by NF K timesteps accumulators from start_pos to
-// min_last_pos, then sweeps the remaining timesteps in the range (min_last_pos,
-// max_last_pos].
-void TileFlashAttention4(
-    const MatPtrT<float>& q, const uint32_t* HWY_RESTRICT q_offsets,
+// Reduces each of x and stores in following lanes of max (tested with float32)
+template <class DF, typename T = hn::TFromD<DF>,
+          class DF4 = hn::CappedTag<T, 4>, class VF4 = hn::Vec<DF4>,
+          class VF = hn::Vec<DF>, typename F>
+static VF4 HWY_INLINE Reduce4(DF df, VF x_0, VF x_1, VF x_2, VF x_3,
+                              F reducer) {
+  const DF4 df4;
+  constexpr size_t kMaxLanes = hn::MaxLanes(df);
+  HWY_LANES_CONSTEXPR size_t kLanes = hn::Lanes(df);
+  HWY_ALIGN T x_transposed[4 * kMaxLanes];
+  hn::StoreInterleaved4<DF>(x_0, x_1, x_2, x_3, df, x_transposed);
+  VF4 result = hn::Load(df4, x_transposed);
+  for (int i = 1; i < kLanes; ++i) {
+    result = reducer(result, hn::Load(df4, x_transposed + i * 4));
+  }
+  return result;
+}
+
+// Handles Up to 4 Q rows by NF*2 timesteps of flash attention.
+template <int kNumQueries, class DF, class VF = hn::Vec<DF>>
+static void HWY_INLINE FlashAttentionTileStepAndApplySoftCap(
+    DF df, float att_cap, float one_over_att_cap, VF& x_0_p0, VF& x_0_p1,
+    VF& x_1_p0, VF& x_1_p1, VF& x_2_p0, VF& x_2_p1, VF& x_3_p0, VF& x_3_p1,
+    float* HWY_RESTRICT old_max, float* HWY_RESTRICT old_d,
+    float* HWY_RESTRICT scales) {
+  using DF4 = hn::CappedTag<float, 4>;
+  const DF4 df4;
+  using VF4 = hn::Vec<DF4>;
+  static_assert(kNumQueries >= 1 && kNumQueries <= 4);
+  VF4 new_max = hn::Set(df4, -std::numeric_limits<float>::max() / 2.0f);
+  VF max_0, max_1, max_2, max_3 = hn::Zero(df);
+  max_0 = hn::Max(x_0_p0, x_0_p1);
+  if constexpr (kNumQueries >= 2) {
+    max_1 = hn::Max(x_1_p0, x_1_p1);
+  }
+  if constexpr (kNumQueries >= 3) {
+    max_2 = hn::Max(x_2_p0, x_2_p1);
+  }
+  if constexpr (kNumQueries >= 4) {
+    max_3 = hn::Max(x_3_p0, x_3_p1);
+  }
+  if constexpr (kNumQueries == 1) {
+    new_max = hn::InsertLane(new_max, 0, hn::ReduceMax(df, max_0));
+  } else {
+    new_max = Reduce4(df, max_0, max_1, max_2, max_3,
+                             [](auto a, auto b) { return hn::Max(a, b); });
+  }
+  if (att_cap > 0.0f) {
+    VF4 cap = hn::Set(df4, att_cap);
+    VF4 one_over_cap = hn::Set(df4, one_over_att_cap);
+    new_max = hn::Mul(cap, hn::Tanh(df4, hn::Mul(new_max, one_over_cap)));
+  }
+  VF4 old_max_vf = hn::Set(df4, -std::numeric_limits<float>::max() / 2.0f);
+  old_max_vf = hn::LoadU(df4, old_max);
+  new_max = hn::Max(new_max, old_max_vf);
+  // TODO figure out what was wrong with broadcasts and change to that.
+  HWY_ALIGN float tmp_max[4];
+  hn::Store(new_max, df4, tmp_max);
+  if constexpr (kNumQueries >= 1) {
+    const VF new_max_0 = hn::Set(df, tmp_max[0]);
+    x_0_p0 = hn::Exp(df, hn::Sub(x_0_p0 , new_max_0));
+    x_0_p1 = hn::Exp(df, hn::Sub(x_0_p1, new_max_0));
+  }
+  if constexpr (kNumQueries >= 2) {
+    const VF new_max_0 = hn::Set(df, tmp_max[1]);
+    x_1_p0 = hn::Exp(df, hn::Sub(x_1_p0, new_max_0));
+    x_1_p1 = hn::Exp(df, hn::Sub(x_1_p1, new_max_0));
+  }
+  if constexpr (kNumQueries >= 3) {
+    const VF new_max_0 = hn::Set(df, tmp_max[2]);
+    x_2_p0 = hn::Exp(df, hn::Sub(x_2_p0, new_max_0));
+    x_2_p1 = hn::Exp(df, hn::Sub(x_2_p1, new_max_0));
+  }
+  if constexpr (kNumQueries >= 4) {
+    const VF new_max_0 = hn::Set(df, tmp_max[3]);
+    x_3_p0 = hn::Exp(df, hn::Sub(x_3_p0, new_max_0));
+    x_3_p1 = hn::Exp(df, hn::Sub(x_3_p1, new_max_0));
+  }
+  VF4 old_d_vf = hn::Set(df4, 0.0f);
+  old_d_vf = hn::LoadU(df4, old_d);
+  VF4 scale = hn::Mul(old_d_vf, hn::Exp(df4, hn::Sub(old_max_vf, new_max)));
+
+  hn::StoreU(new_max, df4, old_max);
+
+  VF4 x_sum = hn::Zero(df4);
+  if constexpr (kNumQueries == 1) {
+    x_sum = hn::Set(df4, hn::ReduceSum(df, x_0_p0) + hn::ReduceSum(df, x_0_p1));
+  } else {
+    VF x_0_sum = hn::Add(x_0_p0, x_0_p1);
+    VF x_1_sum = hn::Add(x_1_p0, x_1_p1);
+    VF x_2_sum = hn::Add(x_2_p0, x_2_p1);
+    VF x_3_sum = hn::Add(x_3_p0, x_3_p1);
+    x_sum = Reduce4(df, x_0_sum, x_1_sum, x_2_sum, x_3_sum,
+                           [](auto a, auto b) { return hn::Add(a, b); });
+  }
+  old_d_vf = hn::Add(scale, x_sum);
+  auto non_zero_mask = hn::Gt(old_d_vf, hn::Set(df4, 0.0f));
+  const VF zero = hn::Zero(df);
+  const VF4 zero4 = hn::Zero(df4);
+  const VF4 one_over_d =
+      hn::MaskedDivOr(zero4, non_zero_mask, hn::Set(df4, 1.0f), old_d_vf);
+  float tmp_one_over_d[4];
+  hn::Store(one_over_d, df4, tmp_one_over_d);
+  hn::Store(old_d_vf, df4, old_d);
+  scale = hn::Mul(scale, one_over_d);
+  hn::Store(scale, df4, scales);
+  if (hn::ExtractLane(old_d_vf, 0) > 0.0f) {
+    const VF one_over_d_0 = hn::Set(df, tmp_one_over_d[0]);
+    x_0_p0 = hn::Mul(x_0_p0, one_over_d_0);
+    x_0_p1 = hn::Mul(x_0_p1, one_over_d_0);
+  } else {
+    x_0_p0 = zero;
+    x_0_p1 = zero;
+  }
+  if constexpr (kNumQueries >= 2) {
+    if (hn::ExtractLane(old_d_vf, 1) > 0.0f) {
+      const VF one_over_d_1 = hn::Set(df, tmp_one_over_d[1]);
+      x_1_p0 = hn::Mul(x_1_p0, one_over_d_1);
+      x_1_p1 = hn::Mul(x_1_p1, one_over_d_1);
+    } else {
+      x_1_p0 = zero;
+      x_1_p1 = zero;
+    }
+  }
+  if constexpr (kNumQueries >= 3) {
+    if (hn::ExtractLane(old_d_vf, 2) > 0.0f) {
+      const VF one_over_d_2 = hn::Set(df, tmp_one_over_d[2]);
+      x_2_p0 = hn::Mul(x_2_p0, one_over_d_2);
+      x_2_p1 = hn::Mul(x_2_p1, one_over_d_2);
+    } else {
+      x_2_p0 = zero;
+      x_2_p1 = zero;
+    }
+  }
+  if constexpr (kNumQueries >= 4) {
+    if (hn::ExtractLane(old_d_vf, 3) > 0.0f) {
+      const VF one_over_d_3 = hn::Set(df, tmp_one_over_d[3]);
+      x_3_p0 = hn::Mul(x_3_p0, one_over_d_3);
+      x_3_p1 = hn::Mul(x_3_p1, one_over_d_3);
+    } else {
+      x_3_p0 = zero;
+      x_3_p1 = zero;
+    }
+  }
+}
+
+// Implements flash attention for a strip of 4 query vectors.
+// It iterates through timesteps in K from `start_pos` up to `max_last_pos`.
+// Timesteps up to `min_last_pos` (*) are processed in tiles of shape 4 Q rows
+// by NF timesteps in K for efficiency while timesteps between `min_last_pos +
+// 1` and `max_last_pos` are processed one-by-one to handle differing `last_pos`
+// values within the strip.
+// (*) Actually, it only iterates through
+// `min_last_pos - (min_last_pos + 1 - start_pos) % NF` in tiles, as the tiled
+// computation can, for obvious reasons, only process an integer number of
+// tiles.
+//
+// @param q The query matrix [batch_size * q_heads, qkv_dim] in BF16 format.
+// @param q_offsets Offsets from `q.Row(0)` to the start of the 4 query
+//   vectors to be processed in this tile.
+// @param k Key matrix [seq_len, qkv_dim] from KV cache.
+// @param start_pos The first token position in the KV cache to attend to.
+// @param last_pos An array of 4 indices giving the last token position
+//   (inclusive) that each of the 4 queries may attend to.
+// @param min_last_pos The minimum value in `last_pos`. Timesteps up to this
+//   position can be processed efficiently in batches.
+// @param max_last_pos The maximum value in `last_pos`. Timesteps between
+//   `min_last_pos + 1` and this position are processed individually to
+//   respect each query's `last_pos` limit.
+// @param v Value matrix [seq_len, qkv_dim] from KV cache.
+// @param layer_idx The index of the current transformer layer.
+// @param activations Attention configurations and buffers.
+// @param att_out Output buffer for attention results.
+// @param out_offsets Offsets from `att_out.Row(0)` to store the 4 output
+//   vectors.
+// @param ctx Threading context.
+// @param worker Worker thread index.
+Tile4FlashState TileFlashAttention4(
+    const MatPtrT<BF16>& q, const uint32_t* HWY_RESTRICT q_offsets,
     const MatPtrT<KV_t>& k, const size_t start_pos,
     const uint32_t* HWY_RESTRICT last_pos, const size_t min_last_pos,
     const size_t max_last_pos, const MatPtrT<KV_t>& v, const size_t layer_idx,
-    const LayerWeightsPtrs& layer, const AttentionActivations& activations,
-    MatPtrT<float>& att_out, const uint32_t* HWY_RESTRICT out_offsets,
-    ThreadingContext& ctx, const size_t worker) {
+    const AttentionActivationsPtrs& activations, MatPtrT<float>& att_out,
+    const uint32_t* HWY_RESTRICT out_offsets, ThreadingContext& ctx,
+    const size_t worker) {
   GCPP_ZONE(ctx, worker, Zones::kFlashAttentionTileFlashAttention4);
   using DF = hn::ScalableTag<float>;
   const DF df;
@@ -440,14 +638,7 @@ void TileFlashAttention4(
     hwy::ZeroBytes(att_out.Row(0) + out_offsets[i],
                    v.Cols() * sizeof(att_out.Row(0)[0]));
   }
-  float old_m0 = -std::numeric_limits<float>::max() / 2.0f;
-  float old_m1 = -std::numeric_limits<float>::max() / 2.0f;
-  float old_m2 = -std::numeric_limits<float>::max() / 2.0f;
-  float old_m3 = -std::numeric_limits<float>::max() / 2.0f;
-  float old_d0 = 0.0f;
-  float old_d1 = 0.0f;
-  float old_d2 = 0.0f;
-  float old_d3 = 0.0f;
+  Tile4FlashState state;
   size_t position = start_pos;
   while (position + kHTileSize - 1 <= min_last_pos) {
     int32_t k_offsets[kMaxNF];
@@ -467,46 +658,62 @@ void TileFlashAttention4(
       x2 = hn::Mul(cap, hn::Tanh(df, hn::Mul(x2, one_over_cap)));
       x3 = hn::Mul(cap, hn::Tanh(df, hn::Mul(x3, one_over_cap)));
     }
-    scales[0] = SingleFlashAttentionRowVector(df, x0, old_m0, old_d0);
-    scales[1] = SingleFlashAttentionRowVector(df, x1, old_m1, old_d1);
-    scales[2] = SingleFlashAttentionRowVector(df, x2, old_m2, old_d2);
-    scales[3] = SingleFlashAttentionRowVector(df, x3, old_m3, old_d3);
+    scales[0] = SingleFlashAttentionRowVector(df, x0, state.row_states[0].max,
+                                              state.row_states[0].d);
+    scales[1] = SingleFlashAttentionRowVector(df, x1, state.row_states[1].max,
+                                              state.row_states[1].d);
+    scales[2] = SingleFlashAttentionRowVector(df, x2, state.row_states[2].max,
+                                              state.row_states[2].d);
+    scales[3] = SingleFlashAttentionRowVector(df, x3, state.row_states[3].max,
+                                              state.row_states[3].d);
     MulByConstAndAddTile4(df, scales, x0, x1, x2, x3, v, v_pos, att_out.Row(0),
                           out_offsets, v.Cols());
     position += kHTileSize;
   }
+  const hn::ScalableTag<BF16> dbf;
+  const size_t qkv_dim = k.Cols();
+
   while (position <= max_last_pos) {
     size_t k_pos = activations.div_seq_len.Remainder(position);
     if (position <= last_pos[0]) {
       // Past the last position, x0 doesn't count.
-      float x0 = Dot(q.Row(0) + q_offsets[0], k.Row(k_pos), k.Cols());
-      SingleFlashAttentionStep(x0, activations.config.att_cap, old_m0, old_d0,
+      float x0 = Dot(dbf, MakeConstSpan(q.Row(0) + q_offsets[0], qkv_dim), 0,
+                     k.Row(k_pos), qkv_dim);
+      SingleFlashAttentionStep(x0, activations.config.att_cap,
+                               state.row_states[0].max, state.row_states[0].d,
                                v.Row(k_pos), v.Cols(),
                                att_out.Row(0) + out_offsets[0]);
     }
     if (position <= last_pos[1]) {
       // Past the last position, x1 doesn't count.
-      float x1 = Dot(q.Row(0) + q_offsets[1], k.Row(k_pos), k.Cols());
-      SingleFlashAttentionStep(x1, activations.config.att_cap, old_m1, old_d1,
+      float x1 = Dot(dbf, MakeConstSpan(q.Row(0) + q_offsets[1], qkv_dim), 0,
+                     k.Row(k_pos), qkv_dim);
+      SingleFlashAttentionStep(x1, activations.config.att_cap,
+                               state.row_states[1].max, state.row_states[1].d,
                                v.Row(k_pos), v.Cols(),
                                att_out.Row(0) + out_offsets[1]);
     }
     if (position <= last_pos[2]) {
       // Past the last position, x2 doesn't count.
-      float x2 = Dot(q.Row(0) + q_offsets[2], k.Row(k_pos), k.Cols());
-      SingleFlashAttentionStep(x2, activations.config.att_cap, old_m2, old_d2,
+      float x2 = Dot(dbf, MakeConstSpan(q.Row(0) + q_offsets[2], qkv_dim), 0,
+                     k.Row(k_pos), qkv_dim);
+      SingleFlashAttentionStep(x2, activations.config.att_cap,
+                               state.row_states[2].max, state.row_states[2].d,
                                v.Row(k_pos), v.Cols(),
                                att_out.Row(0) + out_offsets[2]);
     }
     if (position <= last_pos[3]) {
       // Past the last position, x3 doesn't count.
-      float x3 = Dot(q.Row(0) + q_offsets[3], k.Row(k_pos), k.Cols());
-      SingleFlashAttentionStep(x3, activations.config.att_cap, old_m3, old_d3,
+      float x3 = Dot(dbf, MakeConstSpan(q.Row(0) + q_offsets[3], qkv_dim), 0,
+                     k.Row(k_pos), qkv_dim);
+      SingleFlashAttentionStep(x3, activations.config.att_cap,
+                               state.row_states[3].max, state.row_states[3].d,
                                v.Row(k_pos), v.Cols(),
                                att_out.Row(0) + out_offsets[3]);
     }
     ++position;
   }
+  return state;
 }
 
 // Rounds n to a number that can be used as the number of Q rows in a tile
@@ -589,14 +796,25 @@ size_t GetVTileSize(size_t kNF, size_t num_head_groups, size_t num_tokens,
 // grouped together so that mode 1 or 2 can be used, and choosing which of the
 // 3 modes to use for best efficiency.
 void FlashAttention(const size_t num_tokens, const size_t target_parallelism,
-                    const size_t layer_idx, const LayerWeightsPtrs& layer,
-                    AttentionActivations& activations, QBatch& qbatch,
+                    const size_t layer_idx, const MatPtr& query_norm_scale,
+                    AttentionActivationsPtrs& activations, QBatch& qbatch,
                     ThreadingContext& ctx) {
   GCPP_ZONE(ctx, 0, Zones::kFlashAttentionInclusive);
-  RMSNormAndPositionalEncoding(num_tokens, qbatch, activations.q, layer_idx,
-                               layer, activations, ctx);
+  RMSNormAndPositionalEncoding(num_tokens, qbatch, activations.q,
+                               query_norm_scale, layer_idx, activations, ctx);
   const hwy::Divisor div_qbatch(qbatch.Size());
-  const LayerConfig& layer_config = layer.layer_config;
+  // Compress q to q_bf.
+  ParallelFor(
+      Parallelism::kWithinCluster, activations.q.Rows(), ctx,
+      /*cluster_idx=*/0, Callers::kFlashAttention,
+      [&](size_t row, size_t worker) {
+        CompressPerThread tls;
+        const hn::ScalableTag<float> df;
+        CompressTraits<BF16>::Compress(
+            df, activations.q.Row(row), activations.q.Cols(), tls,
+            MakeSpan(activations.q_bf.Row(row), activations.q_bf.Cols()), 0);
+      });
+  const LayerConfig& layer_config = activations.config.layer_configs[layer_idx];
   const size_t qkv_dim = layer_config.qkv_dim;
 
   // A "head group" in the context of GQA refers to a collection of query
@@ -684,14 +902,14 @@ void FlashAttention(const size_t num_tokens, const size_t target_parallelism,
       size_t last = pos;
       const size_t prefix_end = qbatch.PrefixEnd(qi);
       if (prefix_end > 0 && prefix_end - 1 > last) {
-        // last_pos in QDotK and WeightedSumV is inclusive.
+        // last_pos in `TileFlashAttention` is inclusive.
         last = prefix_end - 1;
       }
       last_pos[offset] = last;
       min_last_pos = HWY_MIN(min_last_pos, last);
       max_last_pos = HWY_MAX(max_last_pos, last);
-      q_offsets[offset] =
-          activations.q.Row(tq_idx) + head * qkv_dim - activations.q.Row(0);
+      q_offsets[offset] = activations.q_bf.Row(tq_idx) + head * qkv_dim -
+                          activations.q_bf.Row(0);
       out_offsets[offset] = activations.att_out.Row(tq_idx) + head * qkv_dim -
                             activations.att_out.Row(0);
       const size_t kv_index = head / kHeadGroups;
@@ -719,9 +937,9 @@ void FlashAttention(const size_t num_tokens, const size_t target_parallelism,
         // To avoid duplicating the code to setup K and V, the call to
         // TileFlashAttention is inside the loop over tasks, even though it
         // handles all rows in the task at once.
-        StridedView<float> qT =
-            StridedView<float>(activations.q_T.Row(0) + first_task, kVTileSize,
-                               activations.q_T.Stride());
+        StridedView<BF16> qT =
+            StridedView<BF16>(activations.q_T.Row(0) + first_task, kVTileSize,
+                              activations.q_T.Stride());
         if (kVTileSize == kNF) {
           // We can still use TileFlashAttention even if we didn't transpose Q
           // above. The condition used for transposing Q above is more general
@@ -730,14 +948,14 @@ void FlashAttention(const size_t num_tokens, const size_t target_parallelism,
           // kNFx8HTileSize. In this case, qT is never used. Some tasks might
           // use qT and some might not, which is why the more general condition
           // is used above to catch all cases where qT will be used.
-          TileFlashAttention(activations.q, q_offsets, qT, k,
+          TileFlashAttention(activations.q_bf, q_offsets, qT, k,
                              start_positions[offset], last_pos, min_last_pos,
-                             max_last_pos, v, layer_idx, layer, activations,
+                             max_last_pos, v, layer_idx, activations,
                              activations.att_out, out_offsets, ctx, worker);
         } else if (kVTileSize == 4) {
-          TileFlashAttention4(activations.q, q_offsets, k,
+          TileFlashAttention4(activations.q_bf, q_offsets, k,
                               start_positions[offset], last_pos, min_last_pos,
-                              max_last_pos, v, layer_idx, layer, activations,
+                              max_last_pos, v, layer_idx, activations,
                               activations.att_out, out_offsets, ctx, worker);
         } else {
           HWY_UNREACHABLE;
@@ -745,8 +963,8 @@ void FlashAttention(const size_t num_tokens, const size_t target_parallelism,
         break;
       } else {
         SingleFlashAttention(start_positions[offset], last_pos[offset],
-                             activations.q.Row(0) + q_offsets[offset], k, v,
-                             layer_idx, layer, activations,
+                             activations.q_bf.Row(0) + q_offsets[offset], k, v,
+                             layer_idx, activations,
                              activations.att_out.Row(0) + out_offsets[offset],
                              ctx, worker);
       }
diff --git a/gemma/flash_attention.h b/gemma/flash_attention.h
index 959b227..b8a70ea 100644
--- a/gemma/flash_attention.h
+++ b/gemma/flash_attention.h
@@ -20,36 +20,48 @@
 
 #include <stddef.h>
 
+#include <cstdint>
+
+#include "gemma/flash_structs.h"
 #include "gemma/gemma.h"
 #include "hwy/highway.h"
 
 namespace gcpp {
 
 // Passed to HWY_VISIT_TARGETS; declares for one target.
-#define GEMMA_DECL_FLASH_ATTENTION(TARGET, NAMESPACE)                        \
-  namespace NAMESPACE {                                                      \
-  void RMSNormAndPositionalEncoding(size_t num_tokens, const QBatch& qbatch, \
-                                    MatPtrT<KV_t>& q, size_t layer_idx,      \
-                                    const LayerWeightsPtrs& layer,           \
-                                    const AttentionActivations& activations, \
-                                    ThreadingContext& ctx);                  \
-                                                                             \
-  void SingleFlashAttention(size_t start_pos, size_t last_pos,               \
-                            const float* HWY_RESTRICT q,                     \
-                            const MatPtrT<KV_t>& k, const MatPtrT<KV_t>& v,  \
-                            size_t layer_idx, const LayerWeightsPtrs& layer, \
-                            const AttentionActivations& activations,         \
-                            float* HWY_RESTRICT att_out,                     \
-                            ThreadingContext& ctx, size_t worker);           \
-                                                                             \
-  size_t GetVTileSize(size_t kNF, size_t num_head_groups, size_t num_tokens, \
-                      size_t total_tasks, size_t target_parallelism);        \
-                                                                             \
-  void FlashAttention(size_t num_tokens, size_t target_parallelism,          \
-                      size_t layer_idx, const LayerWeightsPtrs& layer,       \
-                      AttentionActivations& activations, QBatch& qbatch,     \
-                      ThreadingContext& ctx);                                \
-  /* NOLINTNEXTLINE(google-readability-namespace-comments) */                \
+#define GEMMA_DECL_FLASH_ATTENTION(TARGET, NAMESPACE)                          \
+  namespace NAMESPACE {                                                        \
+  void RMSNormAndPositionalEncoding(                                           \
+      size_t num_tokens, const QBatch& qbatch, MatPtrT<float>& q,              \
+      const MatPtr& query_norm_scale, size_t layer_idx,                        \
+      const AttentionActivationsPtrs& activations, ThreadingContext& ctx);     \
+                                                                               \
+  void SingleFlashAttention(size_t start_pos, size_t last_pos,                 \
+                            const BF16* HWY_RESTRICT q,                        \
+                            const MatPtrT<KV_t>& k, const MatPtrT<KV_t>& v,    \
+                            size_t layer_idx,                                  \
+                            const AttentionActivationsPtrs& activations,       \
+                            float* HWY_RESTRICT att_out,                       \
+                            ThreadingContext& ctx, size_t worker);             \
+                                                                               \
+  Tile4FlashState TileFlashAttention4(                                         \
+      const MatPtrT<BF16>& q, const uint32_t* HWY_RESTRICT q_offsets,          \
+      const MatPtrT<KV_t>& k, size_t start_pos,                                \
+      const uint32_t* HWY_RESTRICT last_pos, size_t min_last_pos,              \
+      size_t max_last_pos, const MatPtrT<KV_t>& v, size_t layer_idx,           \
+      const LayerWeightsPtrs& layer, const AttentionActivations& activations,  \
+      MatPtrT<float>& att_out, const uint32_t* HWY_RESTRICT out_offsets,       \
+      ThreadingContext& ctx, const size_t worker);                             \
+                                                                               \
+  size_t GetVTileSize(size_t kNF, size_t num_head_groups, size_t num_tokens,   \
+                      size_t total_tasks, size_t target_parallelism);          \
+                                                                               \
+  void FlashAttention(size_t num_tokens, size_t target_parallelism,            \
+                      size_t layer_idx, const MatPtr& query_norm_scale,        \
+                      AttentionActivationsPtrs& activations, QBatch& qbatch,   \
+                      ThreadingContext& ctx);                                  \
+                                                                               \
+  /* NOLINTNEXTLINE(google-readability-namespace-comments) */                  \
   }  // namespace NAMESPACE
 
 // Function declarations for each SIMD target. Allows direct call from the
diff --git a/gemma/flash_attention_test.cc b/gemma/flash_attention_test.cc
index 4147e38..f0a90fa 100644
--- a/gemma/flash_attention_test.cc
+++ b/gemma/flash_attention_test.cc
@@ -14,6 +14,8 @@
 // limitations under the License.
 
 #include <cstring>
+#include <iostream>
+#include <limits>
 #include <numeric>
 #include <vector>
 
@@ -24,6 +26,7 @@
 #include "gemma/kv_cache.h"
 #include "gemma/weights.h"
 #include "ops/matmul.h"
+#include "util/test_util.h"
 #ifndef HWY_DISABLED_TARGETS
 #define HWY_DISABLED_TARGETS GEMMA_DISABLED_TARGETS
 #endif  // HWY_DISABLED_TARGETS
@@ -109,11 +112,14 @@ void TestFlashAttention(size_t target_parallelism) {
   const LayerConfig& layer_config = config.layer_configs[0];
   const LayerWeightsPtrs layers(0, layer_config, tensor_info_registry);
   InferenceArgs inference_args;
+  inference_args.attention_impl = "flash";
   RuntimeConfig runtime_config;
+  inference_args.CopyTo(runtime_config);
   KVCache kv_cache(config, inference_args, ctx.allocator);
   MatMulEnv env(ctx);
-  Activations activations(config, runtime_config.prefill_tbatch_size,
-                          kv_cache.SeqLen(), env.ctx, env.row_ptrs);
+  Activations activations(runtime_config, config,
+                          runtime_config.prefill_tbatch_size, kv_cache.SeqLen(),
+                          env.ctx, env.row_ptrs);
   std::vector<int> tokens(kOuter);
   std::iota(tokens.begin(), tokens.end(), 1);
   PromptTokens prompt(tokens);
@@ -122,8 +128,10 @@ void TestFlashAttention(size_t target_parallelism) {
   QBatch qbatch(/*start=*/0, /*max_size=*/kOuter, all_queries);
   const size_t batch_size = kOuter;
   std::vector<hwy::AlignedFreeUniquePtr<uint8_t*[]>> row_ptrs;
-  AttentionActivations attention(config, layer_config, batch_size, kOuter,
-                                 ctx.allocator, row_ptrs);
+  AttentionActivations attention_storage(config, layer_config, batch_size,
+                                         kOuter, runtime_config, ctx.allocator,
+                                         row_ptrs);
+  AttentionActivationsPtrs attention(config, kOuter, attention_storage);
   const size_t qkv_dim = layer_config.qkv_dim;
   ASSERT_EQ(qkv_dim, kInner);
   const hwy::Divisor div_qbatch(qbatch.Size());
@@ -145,7 +153,8 @@ void TestFlashAttention(size_t target_parallelism) {
     SetMat(h + layer_config.heads * 2, v);
   }
   SetMat(1, attention.q);
-  DotSoftmaxWeightedSum(tokens.size(), 0, layers, attention, qbatch, ctx);
+  DotSoftmaxWeightedSum(tokens.size(), 0, layers.query_norm_scale, attention,
+                        qbatch, ctx);
   // Copy the output to saved_att to allow for comparison.
   auto saved_att = MakeCopyOfMat(attention.att_out, ctx.allocator);
   SetMat(1, attention.q);
@@ -158,8 +167,8 @@ void TestFlashAttention(size_t target_parallelism) {
                                          total_tasks, target_parallelism);
   printf("FlashAttention: target_parallelism=%zu, kNF=%zu, kVTileSize=%zu\n",
          target_parallelism, kNF, kVTileSize);
-  FlashAttention(tokens.size(), target_parallelism, 0, layers, attention,
-                 qbatch, ctx);
+  FlashAttention(tokens.size(), target_parallelism, 0, layers.query_norm_scale,
+                 attention, qbatch, ctx);
   AssertClose(attention.att_out, *saved_att);
   ctx.profiler.PrintResults();
 }
diff --git a/gemma/flash_structs.h b/gemma/flash_structs.h
new file mode 100644
index 0000000..73563fe
--- /dev/null
+++ b/gemma/flash_structs.h
@@ -0,0 +1,31 @@
+#ifndef THIRD_PARTY_GEMMA_CPP_GEMMA_FLASH_STRUCTS_H_
+#define THIRD_PARTY_GEMMA_CPP_GEMMA_FLASH_STRUCTS_H_
+
+#include <stddef.h>
+
+#include <limits>
+
+namespace gcpp {
+
+// State for computing softmax in a streaming ("online") manner,
+// avoiding large intermediate values by subtracting the running maximum.
+// For a sequence x_1, ..., x_n:
+// m_i = max(m_{i-1}, x_i)
+// d_i = d_{i-1} * exp(m_{i-1} - m_i) + exp(x_i - m_i)
+// softmax_i = exp(x_i - m_i) / d_i
+struct OnlineSoftmaxState {
+  // Maximum logit value encountered so far.
+  float max = -std::numeric_limits<float>::max() / 2.0f;
+  // Sum of exponentials scaled by exp(-max).
+  float d = 0.0f;
+};
+
+static constexpr size_t kVTileSize4 = 4;
+
+struct Tile4FlashState {
+  OnlineSoftmaxState row_states[kVTileSize4];
+};
+
+}  // namespace gcpp
+
+#endif  // THIRD_PARTY_GEMMA_CPP_GEMMA_FLASH_STRUCTS_H_
diff --git a/gemma/gemma-inl.h b/gemma/gemma-inl.h
index dc7efea..0cd364a 100644
--- a/gemma/gemma-inl.h
+++ b/gemma/gemma-inl.h
@@ -20,6 +20,7 @@
 
 #include "gemma/activations.h"
 #include "gemma/configs.h"
+#include "gemma/tensor_stats.h"
 #include "gemma/weights.h"
 #include "ops/matmul.h"
 #include "util/mat.h"
@@ -70,7 +71,7 @@ template <class Mat>
 void ActivationBatched(
     ActivationType activation, Mat& c1, ThreadingContext& ctx,
     size_t cluster_idx = 0,
-    ParallelismStrategy parallelism = ParallelismStrategy::kFlat) {
+    Parallelism parallelism = Parallelism::kFlat) {
   using T = typename Mat::T;
   ParallelFor(parallelism, c1.Rows(), ctx, cluster_idx,
               Callers::kActivationBatched, [&](uint64_t task, size_t worker) {
@@ -115,7 +116,7 @@ template <class Mat1, class Mat2>
 HWY_NOINLINE void ActivationBatched(
     ActivationType activation, Mat1& c1, const Mat2* c2, ThreadingContext& ctx,
     size_t cluster_idx = 0,
-    ParallelismStrategy parallelism = ParallelismStrategy::kFlat) {
+    Parallelism parallelism = Parallelism::kFlat) {
   HWY_DASSERT(c1.SameShape(*c2));
   if (c2 && c2->HasPtr()) {
     ParallelFor(parallelism, c1.Rows(), ctx, cluster_idx,
@@ -158,6 +159,9 @@ static inline void FFWNoVit(const LayerWeightsPtrs& layer,
 
   HWY_DASSERT(!layer_config.ff_biases);  // Only used in Vit.
 
+  activations.s_ffw_in.Notify(layer.layer_idx, activations.pre_ffw_rms_out,
+                              env.ctx);
+
 #if GEMMA_FUSED_FFN
   const auto fused = [&](RowPtrsBF C1, IndexRange range_r, IndexRange range_c,
                          StridedViewBF C2, size_t worker) {
@@ -179,8 +183,31 @@ static inline void FFWNoVit(const LayerWeightsPtrs& layer,
                     env.ctx);
 #endif
 
+  activations.s_ffw_hidden.Notify(layer.layer_idx, activations.C1, env.ctx);
+
   // Hidden layer -> output layer.
   CallMatMul(activations.C1, layer.linear_w, nullptr, env, activations.ffw_out);
+
+  activations.s_ffw_out.Notify(layer.layer_idx, activations.ffw_out, env.ctx);
+}
+
+// Sums encoded (`att_out`) over num_heads (`layer_config.heads`) and
+// head_dim (`qkv_dim`) into output (`layer_out`).
+static HWY_INLINE void SumHeads(const LayerWeightsPtrs& layer,
+                                AttentionActivationsPtrs& activations,
+                                MatMulEnv& env) {
+  GCPP_ZONE(env.ctx, hwy::Profiler::GlobalIdx(), Zones::kGenAttentionSumHeads);
+  const LayerConfig& layer_config = layer.layer_config;
+  (void)layer_config;  // For HWY_DASSERT
+  // att_weights and att_out are concatenated heads, each of length
+  // layer_config.qkv_dim. Thus the [num_interleaved,
+  // layer_config.model_dim] matmul output is the sum over heads. Compare
+  // gemma/modules.py: attn_output = self.attn_vec_einsum('BTNH,NHD->BTD',
+  // encoded)
+  HWY_DASSERT(layer_config.model_dim != 0 && layer_config.heads != 0 &&
+              layer_config.qkv_dim != 0);
+  CallMatMul(activations.att_out, layer.att_weights, /*add=*/nullptr, env,
+             activations.att_sums);
 }
 
 // NOLINTNEXTLINE(google-readability-namespace-comments)
diff --git a/gemma/gemma.cc b/gemma/gemma.cc
index 7991c35..0ce6ab3 100644
--- a/gemma/gemma.cc
+++ b/gemma/gemma.cc
@@ -18,12 +18,16 @@
 
 #include "gemma/gemma.h"
 
+#include <optional>
+
 #include "compression/types.h"  // GEMMA_DISABLED_TARGETS
-#include "util/zones.h"
 #ifndef HWY_DISABLED_TARGETS
 #define HWY_DISABLED_TARGETS GEMMA_DISABLED_TARGETS
 #endif  // HWY_DISABLED_TARGETS
 
+#include "gemma/tensor_stats.h"
+#include "util/zones.h"
+
 // Compiles this file for multiple architectures via "foreach_target.h", to
 // which we pass the filename via macro 'argument'.
 // clang-format off
@@ -35,7 +39,7 @@
 // After highway.h
 #include "gemma/attention.h"  // includes highway.h
 #include "gemma/gemma-inl.h"
-#include "gemma/vit.h"      // includes highway.h
+#include "gemma/vit.h"  // includes highway.h
 
 #ifndef GEMMA_CC_ONCE
 #define GEMMA_CC_ONCE
@@ -73,10 +77,12 @@ namespace HWY_NAMESPACE {
 void Attention(LayerAttentionType type, const size_t num_tokens,
                const size_t layer_idx, const LayerWeightsPtrs& layer,
                Activations& activations, QBatch& qbatch, MatMulEnv& env) {
+
   if (type == LayerAttentionType::kGemma) {
     // TODO: remove flag to enable FlashAttention.
-    GemmaAttention(num_tokens, layer_idx, layer, activations.attention, qbatch,
-                   env, HWY_NATIVE_DOT_BF16 ? kAttentionUseOld : 0);
+    GemmaAttention(
+        num_tokens, layer_idx, layer, activations.attention, qbatch, env,
+        AttentionImplToFlags(activations.attention_impl, HWY_NATIVE_DOT_BF16));
   }
 }
 
@@ -355,6 +361,10 @@ static HWY_NOINLINE void PrefillQBatch(const size_t max_prompt_size,
         (void)runtime_config.StreamToken(qbatch.QueryIdx(qi), pos_in_prompt,
                                          token, 0.0f);
         qbatch.MutablePos(qi) = pos_in_prompt;
+      } else {
+        // This prevents the kv cache of eos_id to be written to last prefilled
+        // token.
+        qbatch.MutablePos(qi) = qbatch.Prompt(qi).size();
       }
 
       qbatch.PrevToken(qi) = token;
@@ -426,7 +436,7 @@ static void SampleAndStream(const ModelConfig& config,
   timing_info.NotifyGenerated(non_eos.Count());
 
   ParallelFor(
-      ParallelismStrategy::kFlat, qbatch.Size(), env.ctx,
+      Parallelism::kFlat, qbatch.Size(), env.ctx,
       /*cluster_idx=*/0, Callers::kSampleAndStream,
       [&](size_t qi, size_t worker) {
         if (!non_eos.Get(qi)) return;
@@ -484,12 +494,11 @@ ChooseSampleFunc(const RuntimeConfig& runtime_config,
   };
 }
 
-// Decode: generates one continuation token for each query in `qbatch`.
-static void GenerateT(const ModelConfig& config,
-                      const RuntimeConfig& runtime_config,
-                      const AesCtrEngine& engine, const WeightsPtrs& weights,
-                      Activations& activations, QBatch& qbatch, MatMulEnv& env,
-                      TimingInfo& timing_info) {
+static size_t PrefillTBatchOrQBatch(const ModelConfig& config,
+                                    const RuntimeConfig& runtime_config,
+                                    const WeightsPtrs& weights,
+                                    Activations& activations, QBatch& qbatch,
+                                    MatMulEnv& env, TimingInfo& timing_info) {
   size_t max_prompt_size = 0;
   bool all_prefix_end_are_zero = true;
   size_t total_prefill_tokens = 0;  // only for throughput stats.
@@ -511,14 +520,14 @@ static void GenerateT(const ModelConfig& config,
     // We use a single divisor, so all sequence lengths must be the same.
     HWY_ASSERT(qbatch.KV(qi).SeqLen() == seq_len);
   }
-  if (max_prompt_size >= seq_len) {
-    HWY_ABORT("max_prompt_size = %zu, increase --seq_len to at least that.",
-              max_prompt_size);
+  if (max_prompt_size > seq_len) {
+    HWY_ABORT(
+        "max_prompt_size = %zu, seq_len = %zu, increase --seq_len to at least "
+        "that.",
+        max_prompt_size, seq_len);
   }
   HWY_ASSERT(activations.attention.div_seq_len.GetDivisor() == seq_len);
 
-  // Lacks a constructor to bulk-set, hence initialized by Prefill* which have
-  // qi loops anyway.
   hwy::BitSet4096<> non_eos;  // indexed by qi
 
   timing_info.prefill_start = hwy::platform::Now();
@@ -536,18 +545,6 @@ static void GenerateT(const ModelConfig& config,
   timing_info.NotifyPrefill(total_prefill_tokens);
   // queries_pos have been incremented by Prefill.
 
-  // Stream the last prompt token from each query, fill activations.gen_tokens.
-  for (size_t qi = 0; qi < qbatch.Size(); ++qi) {
-    const size_t last_pos_in_prompt = qbatch.Pos(qi) - qbatch.InitialPos(qi);
-
-    const size_t pos = qbatch.Pos(qi);  // during prefill, pos is still correct.
-    // In autoregressive mode, we have not prefilled the last token, so do
-    // not advance.
-    const bool update_pos = (qbatch.Pos(qi) < qbatch.PrefixEnd(qi));
-    StreamAndUpdateEOS(qi, pos, qbatch.Prompt(qi)[last_pos_in_prompt], 0.0f,
-                       config, runtime_config, qbatch, update_pos, non_eos);
-  }
-
   size_t max_gen_steps = runtime_config.max_generated_tokens;
   if (max_prompt_size + max_gen_steps > seq_len) {
     HWY_WARN("prefill %zu + max_gen_steps %zu > seq_len %zu, truncating.",
@@ -555,6 +552,55 @@ static void GenerateT(const ModelConfig& config,
     max_gen_steps = seq_len - max_prompt_size;
   }
 
+  return max_gen_steps;
+}
+
+static void StreamAndUpdateEOSAfterPrefill(const ModelConfig& config,
+                                          const RuntimeConfig& runtime_config,
+                                          QBatch& qbatch,
+                                          hwy::BitSet4096<>& non_eos,
+                                          size_t qi) {
+  const size_t last_pos_in_prompt = qbatch.Pos(qi) - qbatch.InitialPos(qi);
+
+  const size_t pos = qbatch.Pos(qi);  // during prefill, pos is still correct.
+  // In autoregressive mode, we have not prefilled the last token, so do
+  // not advance.
+  const bool update_pos = (qbatch.Pos(qi) < qbatch.PrefixEnd(qi));
+  StreamAndUpdateEOS(qi, pos, qbatch.Prompt(qi)[last_pos_in_prompt], 0.0f,
+                     config, runtime_config, qbatch, update_pos, non_eos);
+}
+
+void SetWeightStats(const LayerWeightsPtrs& layer, Activations& a,
+                    ThreadingContext& ctx) {
+  const size_t layer_idx = layer.layer_idx;
+  a.s_w_gating_einsum_w1.Notify(layer_idx, layer.gating_einsum_w1, ctx,
+                                kTensorStatsIsWeight);
+  a.s_w_gating_einsum_w2.Notify(layer_idx, layer.gating_einsum_w2, ctx,
+                                kTensorStatsIsWeight);
+  a.s_w_linear_w.Notify(layer_idx, layer.linear_w, ctx, kTensorStatsIsWeight);
+}
+
+// Decode: generates one continuation token for each query in `qbatch`.
+static void GenerateT(const ModelConfig& config,
+                      const RuntimeConfig& runtime_config,
+                      const AesCtrEngine& engine, const WeightsPtrs& weights,
+                      Activations& activations, QBatch& qbatch, MatMulEnv& env,
+                      TimingInfo& timing_info) {
+  for (const LayerWeightsPtrs& layer : weights.c_layers) {
+    SetWeightStats(layer, activations, env.ctx);
+  }
+
+  const size_t max_gen_steps = PrefillTBatchOrQBatch(
+      config, runtime_config, weights, activations, qbatch, env, timing_info);
+
+  hwy::BitSet4096<> non_eos;  // indexed by qi
+
+  // Stream the last prompt token from each query, fill activations.gen_tokens.
+  for (size_t qi = 0; qi < qbatch.Size(); ++qi) {
+    non_eos.Set(qi);
+    StreamAndUpdateEOSAfterPrefill(config, runtime_config, qbatch, non_eos, qi);
+  }
+
   const SampleFunc sample_token =
       ChooseSampleFunc(runtime_config, engine, env.ctx);
 
@@ -567,14 +613,66 @@ static void GenerateT(const ModelConfig& config,
   timing_info.NotifyGenerateDone();
 }
 
+// Same as GenerateT, but uses ContinuousQBatch.
+static void GenerateTWithContinuousBatching(
+    const ModelConfig& config, const RuntimeConfig& runtime_config,
+    const AesCtrEngine& engine, const WeightsPtrs& weights,
+    Activations& activations, AllQueries& all_queries, MatMulEnv& env,
+    TimingInfo& timing_info) {
+  const size_t qbatch_size = runtime_config.decode_qbatch_size;
+
+  QBatch qbatch(0, qbatch_size, all_queries);
+  ContinuousQBatch prefill_batch(qbatch_size, all_queries);
+
+  hwy::BitSet4096<> non_eos;
+  const SampleFunc sample_token =
+      ChooseSampleFunc(runtime_config, engine, env.ctx);
+
+  size_t query_inserted = 0;
+  while (non_eos.Any() || query_inserted < all_queries.NumQueries()) {
+    for (size_t qi = 0; qi < qbatch.Size(); ++qi) {
+      // Continue if qi slot is still processing.
+      if (non_eos.Get(qi)) continue;
+      // Collect the kv_cache from the qi slot in the qbatch to the
+      // available_kv_caches_ in the prefill_batch.
+      prefill_batch.MaybeReleaseKV(qbatch.Single(qi));
+
+      // Prefill if no available prefilled queries to insert.
+      if (prefill_batch.ShouldPrefill()) {
+        prefill_batch.SetupNextBatchForPrefill();
+        PrefillTBatchOrQBatch(config, runtime_config, weights, activations,
+                              prefill_batch, env, timing_info);
+        activations.SetBatchSize(qbatch.Size());
+      }
+
+      // Get the next query to insert to the generate batch.
+      std::optional<size_t> qi_to_insert = prefill_batch.GetNextToInsert();
+      if (qi_to_insert) {
+        qbatch.Insert(qi_to_insert.value(), qi);
+        query_inserted++;
+
+        non_eos.Set(qi);
+        StreamAndUpdateEOSAfterPrefill(config, runtime_config, qbatch, non_eos,
+                                       qi);
+      }
+    }
+
+    Transformer(config, runtime_config, weights, activations, qbatch, env);
+    SampleAndStream(config, runtime_config, weights, sample_token, activations,
+                    qbatch, env, non_eos, timing_info);
+  }
+  timing_info.NotifyGenerateDone();
+}
+
 void GenerateSingleT(const PromptTokens& prompt, size_t pos, size_t prefix_end,
                      const ModelConfig& config,
                      const RuntimeConfig& runtime_config,
                      const AesCtrEngine& engine, const WeightsPtrs& weights,
                      KVCache& kv_cache, MatMulEnv& env,
                      TimingInfo& timing_info) {
-  Activations activations(config, runtime_config.prefill_tbatch_size,
-                          kv_cache.SeqLen(), env.ctx, env.row_ptrs);
+  Activations activations(runtime_config, config,
+                          runtime_config.prefill_tbatch_size, kv_cache.SeqLen(),
+                          env.ctx, env.row_ptrs);
 
   AllQueries all_queries(prompt, pos, prefix_end,
                          hwy::Span<KVCache>(&kv_cache, 1));
@@ -592,16 +690,21 @@ void GenerateBatchT(const ModelConfig& config,
                     TimingInfo& timing_info) {
   const size_t max_batch_size = HWY_MAX(runtime_config.decode_qbatch_size,
                                         runtime_config.prefill_tbatch_size);
-  Activations activations(config, max_batch_size,
+  Activations activations(runtime_config, config, max_batch_size,
                           all_queries[0].kv_cache.SeqLen(), env.ctx,
                           env.row_ptrs);
 
-  for (size_t start = 0; start < all_queries.NumQueries();
-       start += runtime_config.decode_qbatch_size) {
-    QBatch qbatch(start, runtime_config.decode_qbatch_size, all_queries);
-    // Generate a batch of one token for each of `qbatch.Size()` queries.
-    GenerateT(config, runtime_config, engine, weights, activations, qbatch, env,
-              timing_info);
+  if (runtime_config.use_continuous_batching) {
+    GenerateTWithContinuousBatching(config, runtime_config, engine, weights,
+                                    activations, all_queries, env, timing_info);
+  } else {
+    for (size_t start = 0; start < all_queries.NumQueries();
+         start += runtime_config.decode_qbatch_size) {
+      QBatch qbatch(start, runtime_config.decode_qbatch_size, all_queries);
+      // Generate a batch of one token for each of `qbatch.Size()` queries.
+      GenerateT(config, runtime_config, engine, weights, activations, qbatch,
+                env, timing_info);
+    }
   }
 }
 
@@ -617,8 +720,8 @@ void GenerateImageTokensT(const ModelConfig& config,
   const size_t num_tokens = vit_config.max_seq_len;
   prefill_runtime_config.prefill_tbatch_size =
       num_tokens / (vit_config.pool_dim * vit_config.pool_dim);
-  Activations prefill_activations(vit_config, num_tokens, num_tokens, env.ctx,
-                                  env.row_ptrs);
+  Activations prefill_activations(runtime_config, vit_config, num_tokens,
+                                  num_tokens, env.ctx, env.row_ptrs);
   // Weights are for the full PaliGemma model, not just the ViT part.
   PrefillVit(config, weights, prefill_runtime_config, image, image_tokens,
              prefill_activations, env);
@@ -635,17 +738,16 @@ HWY_EXPORT(GenerateSingleT);
 HWY_EXPORT(GenerateBatchT);
 HWY_EXPORT(GenerateImageTokensT);
 
-Gemma::Gemma(const LoaderArgs& loader, const InferenceArgs& inference,
-             ThreadingContext& ctx)
-    : reader_(loader.weights),
-      model_(reader_, loader.tokenizer, loader.wrapping),
+Gemma::Gemma(const GemmaArgs& args, ThreadingContext& ctx)
+    : reader_(args.loader.weights),
+      model_(reader_, args.loader.tokenizer, args.loader.wrapping),
       weights_(model_.Config()),
       chat_template_(model_.Tokenizer(), model_.Config().model),
-      inference_(inference),
-      aes_ctr_engine_(inference.deterministic) {
+      inference_(args.inference),
+      aes_ctr_engine_(args.inference.deterministic) {
   // Negligible CPU time in the ctor body (except ReadFromBlobs).
-  weight_read_mode_ = weights_.ReadFromBlobs(model_, reader_, loader, inference,
-                                             mat_owners_, ctx);
+  weight_read_mode_ = weights_.ReadFromBlobs(model_, reader_, args.loader,
+                                             args.inference, mat_owners_, ctx);
   // Read everything into memory, or `weights_.mapped_` keeps the mapping alive.
   reader_.CloseFile();
 }
@@ -698,5 +800,64 @@ void Gemma::GenerateImageTokens(const RuntimeConfig& runtime_config,
   env.ctx.pools.MaybeStopSpinning(runtime_config.use_spinning);
 }
 
+ContinuousQBatch::ContinuousQBatch(size_t max_size, AllQueries& queries)
+    : QBatch(0, max_size, queries) {
+  for (size_t i = start_; i < queries_.NumQueries(); ++i) {
+    if (!queries_[i].kv_cache.IsEmpty()) {
+      // Put the kv_cache to the available_kv_caches_ instead; leaving the
+      // kv_cache in the queries_ is very confusing. This simplifies the logic
+      // of kv_cache management.
+      available_kv_caches_.push_back(queries_[i].kv_cache);
+      queries_[i].kv_cache = KVCachePtr();
+    }
+  }
+}
+
+bool ContinuousQBatch::ShouldPrefill() const {
+  const bool no_available_to_insert = next_to_insert_ == next_to_prefill_;
+  const int more_queries_to_prefill = next_to_prefill_ < queries_.NumQueries();
+  return no_available_to_insert && more_queries_to_prefill;
+}
+
+void ContinuousQBatch::SetupNextBatchForPrefill() {
+  start_ = next_to_prefill_;
+  size_ = HWY_MIN(max_size_, queries_.NumQueries() - start_);
+  HWY_DASSERT(size_ != 0);
+  HWY_DASSERT(start_ + size_ <= queries_.NumQueries());
+  query_idx_.clear();
+  query_idx_.reserve(size_);
+  for (size_t i = 0; i < size_; ++i) {
+    const size_t next_query_idx = start_ + i;
+    query_idx_.push_back(next_query_idx);
+    HWY_ASSERT(queries_[next_query_idx].kv_cache.IsEmpty());
+    queries_[next_query_idx].kv_cache = available_kv_caches_.back();
+    available_kv_caches_.pop_back();
+  }
+  next_to_prefill_ += size_;
+}
+
+std::optional<size_t> ContinuousQBatch::GetNextToInsert() {
+  if (next_to_insert_ == next_to_prefill_) {
+    return std::nullopt;
+  }
+  next_to_insert_++;
+  return next_to_insert_ - 1;
+}
+
+void ContinuousQBatch::MaybeReleaseKV(const QBatch& from) {
+  const int query_to_collect = from.QueryIdx(0);
+  // Only collect if the query to collect is not the same as the next query to
+  // insert. This happens at the beginning of each Generate call.
+  if (query_to_collect != next_to_insert_) {
+    // Only clear the KV cache if there are more queries to insert; Otherwise
+    // we get a crash because Transformer will still access that KV cache.
+    if (next_to_insert_ < queries_.NumQueries()) {
+      available_kv_caches_.push_back(from.KV(0));
+      ZeroInit(from.KV(0).kv_cache);
+      from.KV(0) = KVCachePtr();
+    }
+  }
+}
+
 }  // namespace gcpp
 #endif  // HWY_ONCE
diff --git a/gemma/gemma.h b/gemma/gemma.h
index 771cd1c..b630a8c 100644
--- a/gemma/gemma.h
+++ b/gemma/gemma.h
@@ -18,6 +18,7 @@
 
 #include <stdio.h>
 
+#include <optional>
 #include <vector>
 
 // IWYU pragma: begin_exports
@@ -26,6 +27,7 @@
 #include "gemma/gemma_args.h"
 #include "gemma/kv_cache.h"
 #include "gemma/model_store.h"
+#include "gemma/query.h"
 #include "gemma/weights.h"
 #include "io/blob_store.h"
 #include "io/io.h"       // Path
@@ -38,132 +40,28 @@
 
 namespace gcpp {
 
-struct PerQuery {
-  PromptTokens prompt;
-
-  // Position in the KV cache: initially zero for the first turn, or when
-  // multi-turn is NOT desired. Incremented by prefill and `StreamAndUpdateEOS`.
-  size_t mutable_pos;
-  // Allows computing the last prefill token as `mutable_pos - initial_pos`,
-  // which might differ from `prompt.size() - 1` for prefix-LM.
-  size_t initial_pos;
-  // Zero for causal attention, or the end of the prefix for prefix-LM style
-  // attention in Paligemma.
-  size_t prefix_end;
-
-  KVCache& kv_cache;
-
-  // Previous token generated for this query, or the last prompt token. Will be
-  // fed into the next Transformer() call.
-  int prev_token = 0;
-};
-
-// Array of `PerQuery`. Referenced by `QBatch` and passed to `GenerateBatch`.
-struct AllQueries {
-  AllQueries() = default;
-
-  // For `GenerateSingleT`: same prompt/pos, replicated for each KV cache.
-  AllQueries(const PromptTokens& prompt, size_t pos, size_t prefix_end,
-             const hwy::Span<KVCache>& kv_caches) {
-    per_query_.reserve(kv_caches.size());
-    for (size_t i = 0; i < kv_caches.size(); ++i) {
-      HWY_ASSERT(kv_caches[i].SeqLen() == kv_caches[0].SeqLen());
-      per_query_.push_back(PerQuery{
-          .prompt = prompt,
-          .mutable_pos = pos,
-          .initial_pos = pos,
-          .prefix_end = prefix_end,
-          .kv_cache = kv_caches[i],
-      });
-    }
-  }
-
-  // Batch of queries with initial position set to zero. Causal attention
-  // is requested via empty or all-zero `prefix_end`.
-  AllQueries(
-      const hwy::Span<const PromptTokens>& prompts,
-      const hwy::Span<KVCache>& kv_caches,
-      const hwy::Span<const size_t>& prefix_end = hwy::Span<const size_t>()) {
-    HWY_ASSERT(prompts.size() == kv_caches.size());
-    HWY_ASSERT(prompts.size() == prefix_end.size() || prefix_end.size() == 0);
-    per_query_.reserve(kv_caches.size());
-    for (size_t i = 0; i < kv_caches.size(); ++i) {
-      HWY_ASSERT(kv_caches[i].SeqLen() == kv_caches[0].SeqLen());
-      per_query_.push_back(PerQuery{
-          .prompt = prompts[i],
-          .mutable_pos = 0,
-          .initial_pos = 0,
-          .prefix_end = prefix_end.size() == 0 ? 0 : prefix_end[i],
-          .kv_cache = kv_caches[i],
-      });
-    }
-  }
-
-  void Reserve(size_t size) { per_query_.reserve(size); }
-  void Append(const PerQuery& query) { per_query_.push_back(query); }
-
-  size_t NumQueries() const { return per_query_.size(); }
-
-  PerQuery& operator[](size_t query_idx) {
-    HWY_DASSERT(query_idx < NumQueries());
-    return per_query_[query_idx];
-  }
-  const PerQuery& operator[](size_t query_idx) const {
-    HWY_DASSERT(query_idx < NumQueries());
-    return per_query_[query_idx];
-  }
-
- private:
-  std::vector<PerQuery> per_query_;
-};
-
-// View into AllQueries: either a batch of queries, or a single query for use
-// in PrefillTBatch or GenerateSingleT. Cheap to create because it holds a
-// reference to AllQueries.
-class QBatch {
+// Used for continuous batching.
+class ContinuousQBatch : public QBatch {
  public:
-  QBatch(size_t start, size_t max_size, AllQueries& queries)
-      : start_(start),
-        max_size_(max_size),
-        queries_(queries),
-        size_(HWY_MIN(max_size_, queries_.NumQueries() - start_)) {
-    HWY_ASSERT(max_size_ <= kMaxBatchSize);
-    HWY_DASSERT(size_ != 0);
-    HWY_DASSERT(start_ + size_ <= queries_.NumQueries());
-  }
+  ContinuousQBatch(size_t max_size, AllQueries& queries);
 
-  // Returns a single-query view starting at `qi` relative to this batch.
-  QBatch Single(size_t qi) const { return QBatch(start_ + qi, 1, queries_); }
+  // Whether we should prefill the next batch, i.e. next_to_insert_ ==
+  // next_to_prefill_.
+  bool ShouldPrefill() const;
 
-  // How many queries in this batch, <= `queries_.NumQueries()` and `max_size_`.
-  size_t Size() const { return size_; }
+  // Setup the query_idx_ to point to the next group of queries to prefill.
+  void SetupNextBatchForPrefill();
 
-  // Returns index for use with `AllQueries` and `BatchStreamToken`.
-  size_t QueryIdx(size_t qi) const {
-    HWY_DASSERT(qi < size_);
-    return start_ + qi;
-  }
+  // Get the next query to insert to the generate batch.
+  std::optional<size_t> GetNextToInsert();
 
-  // Accessor functions to bridge the previous SoA and current AoS layout.
-  const PromptTokens& Prompt(size_t qi) const {
-    return queries_[QueryIdx(qi)].prompt;
-  }
-  size_t Pos(size_t qi) const { return queries_[QueryIdx(qi)].mutable_pos; }
-  size_t& MutablePos(size_t qi) { return queries_[QueryIdx(qi)].mutable_pos; }
-  size_t InitialPos(size_t qi) const {
-    return queries_[QueryIdx(qi)].initial_pos;
-  }
-  size_t PrefixEnd(size_t qi) const {
-    return queries_[QueryIdx(qi)].prefix_end;
-  }
-  KVCache& KV(size_t qi) const { return queries_[QueryIdx(qi)].kv_cache; }
-  int& PrevToken(size_t qi) { return queries_[QueryIdx(qi)].prev_token; }
+  // Collect the kv_cache from QBatch to available_kv_caches_.
+  void MaybeReleaseKV(const QBatch& from);
 
- private:
-  size_t start_;
-  size_t max_size_;
-  AllQueries& queries_;
-  size_t size_;
+ public:
+  int next_to_prefill_ = 0;
+  int next_to_insert_ = 0;
+  std::vector<KVCachePtr> available_kv_caches_;
 };
 
 struct TimingInfo {
@@ -232,11 +130,16 @@ struct TimingInfo {
 // separate `ThreadingContext` and `MatMulEnv` for each concurrent `Generate`.
 class Gemma {
  public:
-  // Reads weights/config/tokenizer from the `BlobStore` at `loader.weights`.
+  // Reads weights/config/tokenizer from `BlobStore` at `args.loader.weights`.
   // `ctx` is only used to read tensors and not stored. Calls to `Generate*`
   // may reference the same, or other `ThreadingContext` via `MatMulEnv`.
+  Gemma(const GemmaArgs& args, ThreadingContext& ctx);
+
+  // Deprecated prior interface for backwards compatibility.
   Gemma(const LoaderArgs& loader, const InferenceArgs& inference,
-        ThreadingContext& ctx);
+        ThreadingContext& ctx)
+      : Gemma(GemmaArgs(loader, ThreadingArgs(), inference), ctx) {}
+
   ~Gemma();
 
   const ModelConfig& Config() const { return model_.Config(); }
diff --git a/gemma/gemma_args.h b/gemma/gemma_args.h
index 3135f50..ba72db6 100644
--- a/gemma/gemma_args.h
+++ b/gemma/gemma_args.h
@@ -24,10 +24,12 @@
 #include <functional>
 #include <string>
 
-#include "io/io.h"  // Path
-#include "util/args.h"
+#include "gemma/configs.h"
+#include "io/io.h"        // Path
+#include "util/args.h"    // IWYU pragma: export
 #include "util/basics.h"  // Tristate
 #include "util/mat.h"
+#include "util/threading_context.h"
 #include "hwy/aligned_allocator.h"  // Span
 #include "hwy/base.h"               // HWY_ABORT
 #include "hwy/profiler.h"
@@ -35,7 +37,9 @@
 namespace gcpp {
 
 struct LoaderArgs : public ArgsBase<LoaderArgs> {
-  LoaderArgs(int argc, char* argv[]) { InitAndParse(argc, argv); }
+  LoaderArgs(int argc, char* argv[], ConsumedArgs& consumed) {
+    InitAndParse(argc, argv, consumed);
+  }
   LoaderArgs(const std::string& tokenizer_path,
              const std::string& weights_path) {
     Init();  // Init sets to defaults, so assignments must come after Init().
@@ -139,6 +143,9 @@ struct RuntimeConfig {
 
   int verbosity;  // Controls verbosity of printed messages.
 
+  // Which attention implementation to use.
+  AttentionImpl attention_impl = AttentionImpl::kFlash;
+
   // Functions operating on the generated tokens.
   StreamFunc stream_token;
   BatchStreamFunc batch_stream_token;
@@ -159,10 +166,15 @@ struct RuntimeConfig {
   // default decision is likely sufficient because it is based on whether
   // threads are successfully pinned.
   mutable Tristate use_spinning = Tristate::kDefault;
+
+  // Whether to use continuous batching.
+  bool use_continuous_batching = false;
 };
 
 struct InferenceArgs : public ArgsBase<InferenceArgs> {
-  InferenceArgs(int argc, char* argv[]) { InitAndParse(argc, argv); }
+  InferenceArgs(int argc, char* argv[], ConsumedArgs& consumed) {
+    InitAndParse(argc, argv, consumed);
+  }
   InferenceArgs() { Init(); };
 
   bool IsInteractive() const { return prompt.empty() && prompt_file.Empty(); }
@@ -187,6 +199,7 @@ struct InferenceArgs : public ArgsBase<InferenceArgs> {
   // For prompts longer than the Linux terminal's 4K line edit buffer.
   Path prompt_file;
   std::string eot_line;
+  std::string attention_impl;
 
   template <class Visitor>
   void ForEach(const Visitor& visitor) {
@@ -240,6 +253,8 @@ struct InferenceArgs : public ArgsBase<InferenceArgs> {
         "before the line where only the given string appears.\n    Default = "
         "When a newline is encountered, that signals the end of the turn.",
         2);
+    visitor(attention_impl, "attention_impl", std::string("flash"),
+            "Attention implementation to use. See configs.cc for options.", 2);
   }
 
   void CopyTo(RuntimeConfig& runtime_config) const {
@@ -261,36 +276,39 @@ struct InferenceArgs : public ArgsBase<InferenceArgs> {
 
     runtime_config.temperature = temperature;
     runtime_config.top_k = top_k;
+    runtime_config.attention_impl = GetAttentionImpl(attention_impl);
   }
 };
 
-struct ClientArgs : public ArgsBase<ClientArgs> {
-  ClientArgs(int argc, char* argv[]) { InitAndParse(argc, argv); }
-  ClientArgs() { Init(); };
+// Bundles all args required to construct a `GemmaEnv` or the equivalent.
+struct GemmaArgs {
+  // For callers that do not parse command line args.
+  GemmaArgs(const LoaderArgs& loader,
+            const ThreadingArgs& threading = ThreadingArgs(),
+            const InferenceArgs& inference = InferenceArgs())
+      : loader(loader), threading(threading), inference(inference) {}
 
-  std::string host;
-  int port;
-  std::string api_key;
-  std::string model;
-  std::string prompt;
-  bool interactive;
+  GemmaArgs(int argc, char** argv, ConsumedArgs& consumed)
+      : loader(argc, argv, consumed),
+        threading(argc, argv, consumed),
+        inference(argc, argv, consumed) {}
 
-  template <class Visitor>
-  void ForEach(const Visitor& visitor) {
-    visitor(host, "host", std::string("localhost"),
-            "Server host (default: localhost)");
-    visitor(port, "port", 8080,
-            "Server port (default: 8080)");
-    visitor(api_key, "api_key", std::string(""),
-            "Use public API with key (changes host to "
-            "generativelanguage.googleapis.com:443)");
-    visitor(model, "model", std::string("gemma3-4b"),
-            "Model name to use (default: gemma3-4b)");
-    visitor(prompt, "prompt", std::string("Hello! How are you?"),
-            "Prompt for generation (default: 'Hello! How are you?')");
-    visitor(interactive, "interactive", false,
-            "Start interactive chat mode (0 = no, 1 = yes)");
+  void Help() {
+    fprintf(stderr,
+            "To run with pre-2025 weights, specify --tokenizer and --weights.\n"
+            "With the single-file weights format, specify just --weights.\n"
+            "\n*Model Loading Arguments*\n");
+    loader.Help();
+    fprintf(stderr, "\n*Threading Arguments*\n");
+    threading.Help();
+    fprintf(stderr, "\n*Inference Arguments*\n");
+    inference.Help();
+    fprintf(stderr, "\n");
   }
+
+  LoaderArgs loader;
+  ThreadingArgs threading;
+  InferenceArgs inference;
 };
 
 }  // namespace gcpp
diff --git a/gemma/gemma_args_test.cc b/gemma/gemma_args_test.cc
new file mode 100644
index 0000000..d9ee8b7
--- /dev/null
+++ b/gemma/gemma_args_test.cc
@@ -0,0 +1,74 @@
+#include "gemma/gemma_args.h"
+
+#include <stddef.h>
+
+#include <string>
+#include <vector>
+
+#include "gtest/gtest.h"
+
+namespace gcpp {
+
+void FillPtrs(const std::vector<std::string>& args, std::vector<char*>& ptrs) {
+  ptrs.reserve(args.size());
+  for (const std::string& arg : args) {
+    ptrs.push_back(const_cast<char*>(arg.data()));
+  }
+}
+
+static void CheckAllConsumed(const std::vector<std::string>& args) {
+  std::vector<char*> ptrs;
+  FillPtrs(args, ptrs);
+  const int argc = static_cast<int>(args.size());
+  char** argv = const_cast<char**>(ptrs.data());
+
+  ConsumedArgs consumed(argc, argv);
+  GemmaArgs gemma_args(argc, argv, consumed);
+  consumed.AbortIfUnconsumed();
+}
+
+static void CheckUnconsumed(const std::vector<std::string>& args,
+                            size_t expected) {
+  std::vector<char*> ptrs;
+  FillPtrs(args, ptrs);
+  const int argc = static_cast<int>(args.size());
+  char** argv = const_cast<char**>(ptrs.data());
+
+  ConsumedArgs consumed(argc, argv);
+  GemmaArgs gemma_args(argc, argv, consumed);
+  ASSERT_EQ(expected, consumed.FirstUnconsumed());
+}
+
+// Note: do not use --help because that is not actually consumed; it is actually
+// special-cased in `HasHelp`.
+TEST(GemmaArgsTest, AllConsumedArgs) {
+  // Single arg
+  CheckAllConsumed({"gemma", "--weights=x"});
+  // Two args, one with =
+  CheckAllConsumed({"gemma", "--weights=x", "--verbosity=1"});
+  // Two args, one with extra value
+  CheckAllConsumed({"gemma", "--weights=x", "--verbosity", "2"});
+  // Two args with values
+  CheckAllConsumed({"gemma", "--verbosity", "2", "--deterministic=true"});
+}
+
+TEST(GemmaArgsTest, UnconsumedArgs) {
+  // Single unconsumed arg
+  CheckUnconsumed({"gemma", "--UNDEFINED"}, 1);
+  // Single unconsumed arg, no --
+  CheckUnconsumed({"gemma", "UNDEFINED"}, 1);
+  // Single unconsumed arg after valid arg
+  CheckUnconsumed({"gemma", "--weights=x", "--UNDEFINED"}, 2);
+  // Single unconsumed arg before valid arg
+  CheckUnconsumed({"gemma", "--UNDEFINED", "--weights=x"}, 1);
+  // Single unconsumed arg with = after valid arg
+  CheckUnconsumed({"gemma", "--weights=x", "--UNDEFINED=1"}, 2);
+  // Single unconsumed arg with = before valid arg
+  CheckUnconsumed({"gemma", "--UNDEFINED=false", "--weights=x"}, 1);
+  // Multiple unconsumed args
+  CheckUnconsumed({"gemma", "--UNDEFINED", "--XXX"}, 1);
+  // Multiple unconsumed args with valid arg between
+  CheckUnconsumed({"gemma", "--UNDEFINED", "--weights=x", "--XXX"}, 1);
+}
+
+}  // namespace gcpp
diff --git a/gemma/kv_cache.cc b/gemma/kv_cache.cc
index ca814f4..2fe6885 100644
--- a/gemma/kv_cache.cc
+++ b/gemma/kv_cache.cc
@@ -16,6 +16,7 @@
 #include "gemma/kv_cache.h"
 
 #include <stddef.h>
+#include <vector>
 
 #include "gemma/configs.h"
 #include "gemma/gemma_args.h"
@@ -50,8 +51,16 @@ KVCache KVCache::Copy() {
   KVCache copy(kv_cache.Extents(), allocator_);
 
   CopyMat(kv_cache, copy.kv_cache);
-
   return copy;
 }
 
+std::vector<KVCachePtr> ToKVCachePtrs(const hwy::Span<KVCache>& kv_caches) {
+  std::vector<KVCachePtr> ptrs;
+  ptrs.reserve(kv_caches.size());
+  for (size_t i = 0; i < kv_caches.size(); ++i) {
+    ptrs.push_back(kv_caches[i].ToPtr());
+  }
+  return ptrs;
+}
+
 }  // namespace gcpp
diff --git a/gemma/kv_cache.h b/gemma/kv_cache.h
index 31e964b..bad66fa 100644
--- a/gemma/kv_cache.h
+++ b/gemma/kv_cache.h
@@ -18,7 +18,10 @@
 
 #include <stddef.h>
 
-#include "gemma/configs.h"  // ModelConfig
+#include <optional>
+#include <vector>
+
+#include "gemma/configs.h"     // ModelConfig
 #include "gemma/gemma_args.h"  // InferenceArgs
 #include "util/basics.h"       // BF16
 #include "util/mat.h"
@@ -27,18 +30,33 @@ namespace gcpp {
 
 using KV_t = float;
 
+// A non-owning view of a KVCache.
+struct KVCachePtr {
+  bool IsEmpty() const { return kv_cache.Rows() == 0; }
+  size_t SeqLen() const;
+
+  MatPtrT<KV_t> kv_cache;
+};
+
 struct KVCache {
   KVCache(const ModelConfig& config, const InferenceArgs& inference_args,
           const Allocator& allocator);
-
   // Returns a deep copy of the KVCache. Use explicit function instead of
   // copy ctor to make the cost explicit.
   KVCache Copy();
 
-  size_t SeqLen() const { return kv_cache.Rows(); }
+  size_t SeqLen() const {
+    return kv_cache.Rows();
+  }
 
   MatStorageT<KV_t> kv_cache;  // [seq_len, layers * kv_heads * qkv_dim * 2]
 
+  KVCachePtr ToPtr() {
+    return KVCachePtr{
+        .kv_cache = kv_cache,
+    };
+  }
+
  private:
   const Allocator& allocator_;
 
@@ -46,6 +64,13 @@ struct KVCache {
   KVCache(const Extents2D& kv_extents, const Allocator& allocator);
 };
 
+inline size_t KVCachePtr::SeqLen() const {
+  return kv_cache.Rows();
+}
+
+// Convenience function to create views into KVCaches.
+std::vector<KVCachePtr> ToKVCachePtrs(const hwy::Span<KVCache>& kv_caches);
+
 }  // namespace gcpp
 
 #endif  // THIRD_PARTY_GEMMA_CPP_GEMMA_KV_CACHE_H_
diff --git a/gemma/kv_cache_test.cc b/gemma/kv_cache_test.cc
new file mode 100644
index 0000000..157b3d9
--- /dev/null
+++ b/gemma/kv_cache_test.cc
@@ -0,0 +1,43 @@
+#include "gemma/kv_cache.h"
+
+#include <cstddef>
+#include <vector>
+
+#include "gtest/gtest.h"
+#include "gemma/configs.h"
+#include "gemma/gemma_args.h"
+#include "util/threading_context.h"
+#include "hwy/aligned_allocator.h"
+namespace gcpp {
+namespace {
+
+TEST(KVCacheTest, KVCacheToPtrs) {
+  ModelConfig model_config;
+  model_config.max_seq_len = 1024;
+  model_config.num_layers = 2;
+  for (int i = 0; i < model_config.num_layers; ++i) {
+    model_config.layer_configs.push_back(LayerConfig());
+    model_config.layer_configs.back().kv_heads = 4;
+    model_config.layer_configs.back().qkv_dim = 256;
+  }
+  InferenceArgs inference_args;
+  inference_args.seq_len = 1024;
+  RuntimeConfig runtime_config;
+  runtime_config.attention_impl = AttentionImpl::kFlash;
+  ThreadingArgs threading_args;
+  ThreadingContext ctx(threading_args);
+  std::vector<KVCache> caches;
+  caches.emplace_back(model_config, inference_args, runtime_config,
+                      ctx.allocator);
+  inference_args.seq_len = 512;
+  caches.emplace_back(model_config, inference_args, runtime_config,
+                      ctx.allocator);
+
+  std::vector<KVCachePtr> ptrs = ToKVCachePtrs({caches.data(), caches.size()});
+  ASSERT_EQ(ptrs.size(), 2);
+  EXPECT_EQ(ptrs[0].kv_cache.Row(0), caches[0].kv_cache.Row(0));
+  EXPECT_EQ(ptrs[1].kv_cache.Row(0), caches[1].kv_cache.Row(0));
+}
+
+}  // namespace
+}  // namespace gcpp
diff --git a/gemma/model_store.cc b/gemma/model_store.cc
index 2f3e1ec..204dee9 100644
--- a/gemma/model_store.cc
+++ b/gemma/model_store.cc
@@ -221,6 +221,8 @@ static size_t DeduceNumLayers(const KeyVec& keys) {
 // This works with or without type prefixes because it searches for substrings.
 static int DeduceLayerTypes(const BlobReader& reader) {
   int layer_types = 0;
+  bool has_key_norm = false;
+  bool has_query_norm = false;
   for (size_t key_idx = 0; key_idx < reader.Keys().size(); ++key_idx) {
     const std::string& key = reader.Keys()[key_idx];
     if (key.find("qkv_ein_w") != std::string::npos) {  // NOLINT
@@ -232,6 +234,15 @@ static int DeduceLayerTypes(const BlobReader& reader) {
         layer_types |= kDeduced448;
       }
     }
+    if (key.find("key_norm") != std::string::npos) {  // NOLINT
+      has_key_norm = true;
+    }
+    if (key.find("query_norm") != std::string::npos) {  // NOLINT
+      has_query_norm = true;
+    }
+  }
+  if (has_key_norm && has_query_norm) {
+    layer_types |= kDeducedKqNorm;
   }
   return layer_types;
 }
diff --git a/gemma/query.h b/gemma/query.h
new file mode 100644
index 0000000..36e8ee5
--- /dev/null
+++ b/gemma/query.h
@@ -0,0 +1,186 @@
+// Copyright 2024 Google LLC
+// SPDX-License-Identifier: Apache-2.0
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     https://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#ifndef THIRD_PARTY_GEMMA_CPP_GEMMA_QUERY_H_
+#define THIRD_PARTY_GEMMA_CPP_GEMMA_QUERY_H_
+
+#include <vector>
+
+#include "gemma/gemma_args.h"
+#include "gemma/kv_cache.h"
+#include "util/basics.h"
+#include "hwy/aligned_allocator.h"  // Span
+#include "hwy/base.h"
+
+namespace gcpp {
+
+struct PerQuery {
+  PromptTokens prompt;
+
+  // Position in the KV cache: initially zero for the first turn, or when
+  // multi-turn is NOT desired. Incremented by prefill and `StreamAndUpdateEOS`.
+  size_t mutable_pos;
+  // Allows computing the last prefill token as `mutable_pos - initial_pos`,
+  // which might differ from `prompt.size() - 1` for prefix-LM.
+  size_t initial_pos;
+  // Zero for causal attention, or the end of the prefix for prefix-LM style
+  // attention in Paligemma.
+  size_t prefix_end;
+
+  KVCachePtr kv_cache;
+
+  // Previous token generated for this query, or the last prompt token. Will be
+  // fed into the next Transformer() call.
+  int prev_token = 0;
+};
+
+// Array of `PerQuery`. Referenced by `QBatch` and passed to `GenerateBatch`.
+struct AllQueries {
+  AllQueries() = default;
+
+  // For `GenerateSingleT`: same prompt/pos, replicated for each KV cache.
+  AllQueries(const PromptTokens& prompt, size_t pos, size_t prefix_end,
+             const hwy::Span<KVCachePtr>& kv_caches) {
+    per_query_.reserve(kv_caches.size());
+    for (size_t i = 0; i < kv_caches.size(); ++i) {
+      HWY_ASSERT(kv_caches[i].SeqLen() == kv_caches[0].SeqLen());
+      per_query_.push_back(PerQuery{
+          .prompt = prompt,
+          .mutable_pos = pos,
+          .initial_pos = pos,
+          .prefix_end = prefix_end,
+          .kv_cache = kv_caches[i],
+      });
+    }
+  }
+
+  AllQueries(const PromptTokens& prompt, size_t pos, size_t prefix_end,
+             const hwy::Span<KVCache>& kv_caches)
+      : AllQueries(prompt, pos, prefix_end,
+                   hwy::Span<KVCachePtr>(ToKVCachePtrs(kv_caches))) {}
+
+  // Batch of queries with initial position set to zero. Causal attention
+  // is requested via empty or all-zero `prefix_end`.
+  AllQueries(
+      const hwy::Span<const PromptTokens>& prompts,
+      const hwy::Span<KVCachePtr>& kv_caches,
+      const hwy::Span<const size_t>& prefix_end = hwy::Span<const size_t>()) {
+    HWY_ASSERT(prompts.size() == prefix_end.size() || prefix_end.size() == 0);
+    per_query_.reserve(prompts.size());
+    for (size_t i = 0; i < prompts.size(); ++i) {
+      HWY_ASSERT(kv_caches.size() == 0 ||
+                 kv_caches[i].SeqLen() == kv_caches[0].SeqLen());
+      per_query_.push_back(PerQuery{
+          .prompt = prompts[i],
+          .mutable_pos = 0,
+          .initial_pos = 0,
+          .prefix_end = prefix_end.size() == 0 ? 0 : prefix_end[i],
+          .kv_cache = kv_caches.size() == 0 ? KVCachePtr() : kv_caches[i],
+      });
+    }
+  }
+
+  AllQueries(
+      const hwy::Span<const PromptTokens>& prompts,
+      const hwy::Span<KVCache>& kv_caches,
+      const hwy::Span<const size_t>& prefix_end = hwy::Span<const size_t>())
+      : AllQueries(prompts, hwy::Span<KVCachePtr>(ToKVCachePtrs(kv_caches)),
+                   prefix_end) {}
+
+  void Reserve(size_t size) { per_query_.reserve(size); }
+  void Append(const PerQuery& query) { per_query_.push_back(query); }
+
+  size_t NumQueries() const { return per_query_.size(); }
+
+  PerQuery& operator[](size_t query_idx) {
+    HWY_DASSERT(query_idx < NumQueries());
+    return per_query_[query_idx];
+  }
+  const PerQuery& operator[](size_t query_idx) const {
+    HWY_DASSERT(query_idx < NumQueries());
+    return per_query_[query_idx];
+  }
+
+ private:
+  std::vector<PerQuery> per_query_;
+};
+
+// View into AllQueries: either a batch of queries, or a single query for use
+// in PrefillTBatch or GenerateSingleT. Cheap to create because it holds a
+// reference to AllQueries.
+class QBatch {
+ public:
+  QBatch(size_t start, size_t max_size, AllQueries& queries)
+      : start_(start),
+        max_size_(max_size),
+        queries_(queries),
+        size_(HWY_MIN(max_size_, queries_.NumQueries() - start_)) {
+    HWY_ASSERT(max_size_ <= kMaxBatchSize);
+    HWY_DASSERT(size_ != 0);
+    HWY_DASSERT(start_ + size_ <= queries_.NumQueries());
+    query_idx_.reserve(size_);
+    for (size_t i = 0; i < size_; ++i) {
+      query_idx_.push_back(start_ + i);
+    }
+  }
+
+  // Returns a single-query view starting at `qi` relative to this batch.
+  QBatch Single(size_t qi) const { return QBatch(QueryIdx(qi), 1, queries_); }
+
+  // How many queries in this batch, <= `queries_.NumQueries()` and `max_size_`.
+  size_t Size() const { return size_; }
+
+  // Returns index for use with `AllQueries` and `BatchStreamToken`.
+  size_t QueryIdx(size_t qi) const {
+    HWY_DASSERT(qi < size_);
+    return query_idx_[qi];
+  }
+
+  // Accessor functions to bridge the previous SoA and current AoS layout.
+  const PromptTokens& Prompt(size_t qi) const {
+    return queries_[QueryIdx(qi)].prompt;
+  }
+  size_t Pos(size_t qi) const { return queries_[QueryIdx(qi)].mutable_pos; }
+  size_t& MutablePos(size_t qi) { return queries_[QueryIdx(qi)].mutable_pos; }
+  size_t InitialPos(size_t qi) const {
+    return queries_[QueryIdx(qi)].initial_pos;
+  }
+  size_t PrefixEnd(size_t qi) const {
+    return queries_[QueryIdx(qi)].prefix_end;
+  }
+  KVCachePtr& KV(size_t qi) const { return queries_[QueryIdx(qi)].kv_cache; }
+  int& PrevToken(size_t qi) { return queries_[QueryIdx(qi)].prev_token; }
+
+  // let query_idx_[to] point to the from in the queries_; this is only used if
+  // the slot in the QBatch is less than the number of queries.
+  void Insert(size_t from, size_t to) {
+    if (from == to) return;
+    HWY_ASSERT(!queries_[from].kv_cache.IsEmpty());
+    HWY_ASSERT(queries_[to].kv_cache.IsEmpty());
+    // Conceptually, insert from.query to location to.
+    query_idx_[to] = from;
+  }
+
+ protected:
+  size_t start_;
+  size_t max_size_;
+  AllQueries& queries_;
+  std::vector<size_t> query_idx_;
+  size_t size_;
+};
+
+}  // namespace gcpp
+
+#endif  // THIRD_PARTY_GEMMA_CPP_GEMMA_QUERY_H_
diff --git a/gemma/run.cc b/gemma/run.cc
index 7e2059f..6c6f4d0 100644
--- a/gemma/run.cc
+++ b/gemma/run.cc
@@ -89,9 +89,11 @@ std::string GetPrompt(const InferenceArgs& inference) {
 }
 
 // The main Read-Eval-Print Loop.
-void ReplGemma(const ThreadingArgs& threading, const InferenceArgs& inference,
-               const Gemma& gemma, KVCache& kv_cache, MatMulEnv& env) {
+void ReplGemma(const GemmaArgs& args, const Gemma& gemma, KVCache& kv_cache,
+               MatMulEnv& env) {
   PROFILER_ZONE("Gen.misc");
+  const InferenceArgs& inference = args.inference;
+  const int verbosity = inference.verbosity;
   size_t abs_pos = 0;                     // across turns
   size_t tokens_generated_this_turn = 0;  // differentiates prefill from reply
   size_t prompt_size = 0;
@@ -113,12 +115,12 @@ void ReplGemma(const ThreadingArgs& threading, const InferenceArgs& inference,
     HWY_ASSERT(image.ReadPPM(inference.image_file.path));
     const size_t image_size = config.vit_config.image_size;
     image.Resize(image_size, image_size);
-    RuntimeConfig runtime_config = {.verbosity = inference.verbosity,
-                                    .use_spinning = threading.spin};
+    RuntimeConfig runtime_config = {.verbosity = verbosity,
+                                    .use_spinning = args.threading.spin};
     double image_tokens_start = hwy::platform::Now();
     gemma.GenerateImageTokens(runtime_config, kv_cache.SeqLen(), image,
                               image_tokens, env);
-    if (inference.verbosity >= 1) {
+    if (verbosity >= 1) {
       double image_tokens_duration = hwy::platform::Now() - image_tokens_start;
       fprintf(stderr,
               "\n\n[ Timing info ] Image token generation took: %d ms\n",
@@ -129,11 +131,15 @@ void ReplGemma(const ThreadingArgs& threading, const InferenceArgs& inference,
   // callback function invoked for each generated token.
   auto batch_stream_token = [&](size_t query_idx, size_t pos, int token,
                                 float) {
-    std::string token_text;
-    HWY_ASSERT(gemma.Tokenizer().Decode(std::vector<int>{token}, &token_text));
-
     HWY_ASSERT(pos == abs_pos);
     ++abs_pos;
+
+    std::string token_text;
+    if (!gemma.Tokenizer().Decode(std::vector<int>{token}, &token_text)) {
+      if (token == -2) return true;  // Gemma 3 ViT?
+      HWY_WARN("Failed to decode token %d.", token);
+    }
+
     const bool in_prompt = tokens_generated_this_turn < prompt_size;
     const bool first_response_token = tokens_generated_this_turn == prompt_size;
     ++tokens_generated_this_turn;
@@ -185,7 +191,7 @@ void ReplGemma(const ThreadingArgs& threading, const InferenceArgs& inference,
     TimingInfo timing_info = {.verbosity = inference.verbosity};
     RuntimeConfig runtime_config = {.verbosity = inference.verbosity,
                                     .batch_stream_token = batch_stream_token,
-                                    .use_spinning = threading.spin};
+                                    .use_spinning = args.threading.spin};
     inference.CopyTo(runtime_config);
     std::vector<int> prompt;
     size_t prefix_end = 0;
@@ -248,14 +254,14 @@ void ReplGemma(const ThreadingArgs& threading, const InferenceArgs& inference,
   }
 }
 
-void Run(const LoaderArgs& loader, const ThreadingArgs& threading,
-         const InferenceArgs& inference) {
+void Run(const GemmaArgs& args) {
   PROFILER_ZONE("Run.misc");
 
-  ThreadingContext ctx(threading);
+  ThreadingContext ctx(args.threading);
   MatMulEnv env(ctx);
+  const InferenceArgs& inference = args.inference;
   if (inference.verbosity >= 3) env.print_best = true;
-  const Gemma gemma(loader, inference, ctx);
+  const Gemma gemma(args, ctx);
   KVCache kv_cache(gemma.Config(), inference, ctx.allocator);
 
   if (inference.verbosity >= 1) {
@@ -283,13 +289,12 @@ void Run(const LoaderArgs& loader, const ThreadingArgs& threading,
     if (inference.IsInteractive()) {
       std::cout << "\033[2J\033[1;1H"  // clear screen
                 << kAsciiArtBanner << "\n\n";
-      ShowConfig(loader, threading, inference, gemma.Config(),
-                 gemma.WeightReadMode(), ctx);
+      ShowConfig(args, gemma.Config(), gemma.WeightReadMode(), ctx);
       std::cout << "\n" << instructions << "\n";
     }
   }
 
-  ReplGemma(threading, inference, gemma, kv_cache, env);
+  ReplGemma(args, gemma, kv_cache, env);
 }
 
 }  // namespace gcpp
@@ -298,17 +303,24 @@ int main(int argc, char** argv) {
   gcpp::InternalInit();
   {
     // Negligible CPU time.
-    gcpp::LoaderArgs loader(argc, argv);
-    gcpp::ThreadingArgs threading(argc, argv);
-    gcpp::InferenceArgs inference(argc, argv);
+    gcpp::ConsumedArgs consumed(argc, argv);
+    gcpp::GemmaArgs args(argc, argv, consumed);
 
     if (gcpp::HasHelp(argc, argv)) {
       std::cerr << gcpp::kAsciiArtBanner;
-      gcpp::ShowHelp(loader, threading, inference);
+      fprintf(stderr,
+              "\n\ngemma.cpp : a lightweight, standalone C++ inference engine\n"
+              "==========================================================\n\n"
+              "*Example Usage*\n\n./gemma --tokenizer tokenizer.spm "
+              "--weights gemma2-2b-it-sfp.sbs\n\n");
+      args.Help();
       return 0;
     }
 
-    gcpp::Run(loader, threading, inference);
+    // After `HasHelp` so that we print --help even if unconsumed args remain.
+    consumed.AbortIfUnconsumed();
+
+    gcpp::Run(args);
   }
   PROFILER_PRINT_RESULTS();  // Must call outside the zone above.
   return 0;
diff --git a/gemma/tensor_info.cc b/gemma/tensor_info.cc
index 05f829b..2810307 100644
--- a/gemma/tensor_info.cc
+++ b/gemma/tensor_info.cc
@@ -1,3 +1,18 @@
+// Copyright 2025 Google LLC
+// SPDX-License-Identifier: Apache-2.0
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     https://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
 #include "gemma/tensor_info.h"
 
 #include <stddef.h>
diff --git a/gemma/tensor_info.h b/gemma/tensor_info.h
index 6becb29..60decf8 100644
--- a/gemma/tensor_info.h
+++ b/gemma/tensor_info.h
@@ -1,3 +1,18 @@
+// Copyright 2025 Google LLC
+// SPDX-License-Identifier: Apache-2.0
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     https://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
 #ifndef THIRD_PARTY_GEMMA_CPP_GEMMA_TENSOR_INFO_H_
 #define THIRD_PARTY_GEMMA_CPP_GEMMA_TENSOR_INFO_H_
 
diff --git a/gemma/tensor_stats.cc b/gemma/tensor_stats.cc
new file mode 100644
index 0000000..53203b6
--- /dev/null
+++ b/gemma/tensor_stats.cc
@@ -0,0 +1,205 @@
+// Copyright 2025 Google LLC
+// SPDX-License-Identifier: Apache-2.0
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     https://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#include "gemma/tensor_stats.h"
+
+#if GCPP_TENSOR_STATS
+#include <stddef.h>
+#include <stdint.h>
+#include <stdio.h>
+
+#include <atomic>
+#include <cmath>
+#include <memory>
+
+#include "io/io.h"
+#include "util/mat.h"
+#include "util/threading_context.h"
+#include "util/zones.h"
+#include "hwy/profiler.h"  // StringTable
+
+// Compiles this file for multiple architectures via "foreach_target.h", to
+// which we pass the filename via macro 'argument'.
+// clang-format off
+#undef HWY_TARGET_INCLUDE
+#define HWY_TARGET_INCLUDE "gemma/tensor_stats.cc"  // NOLINT
+// clang-format on
+#include "hwy/foreach_target.h"  // IWYU pragma: keep
+#include "hwy/highway.h"
+// After highway.h
+#include "compression/compress-inl.h"
+#include "ops/dot-inl.h"
+
+HWY_BEFORE_NAMESPACE();
+namespace gcpp {
+namespace HWY_NAMESPACE {
+
+float Correlation(const float* x, size_t num) {
+  double sum = 0.0;
+  for (size_t i = 0; i < num; ++i) {
+    sum += x[i];
+  }
+  const double mean = sum / static_cast<double>(num);
+
+  double numerator = 0.0;
+  double sum_sq_current = 0.0;
+  double sum_sq_next = 0.0;
+
+  for (size_t i = 0; i < num - 1; ++i) {
+    const double diff_current = static_cast<double>(x[i]) - mean;
+    const double diff_next = static_cast<double>(x[i + 1]) - mean;
+
+    numerator += diff_current * diff_next;
+    sum_sq_current += diff_current * diff_current;
+    sum_sq_next += diff_next * diff_next;
+  }
+
+  if (sum_sq_current == 0.0 || sum_sq_next == 0.0) return 0.0f;
+  const double denominator = std::sqrt(sum_sq_current * sum_sq_next);
+  const float corr = static_cast<float>(numerator / denominator);
+  HWY_DASSERT(-1.0f <= corr && corr <= 1.0f);
+  return corr;
+}
+
+// Only write tensor data the first time it is encountered per layer. This is
+// a concurrent string+layer -> flag map which avoids std::mutex (incompatible
+// with fibers). We use a string table to index into per-layer atomic flags.
+static bool ShouldWrite(const char* name, size_t layer_idx) {
+  constexpr size_t kMaxNames = 128;
+  constexpr size_t kMaxLayers = 128;
+  HWY_DASSERT(layer_idx < kMaxLayers);
+  static hwy::StringTable<kMaxNames> s_table;
+  const size_t name_idx = s_table.Add(name);
+  static std::atomic_flag flags[kMaxNames * kMaxLayers] = {};
+  return !flags[name_idx * kMaxLayers + layer_idx].test_and_set(
+      std::memory_order_acq_rel);
+}
+
+std::unique_ptr<File> MaybeOpenFile(size_t layer_idx, const MatPtr& type_erased,
+                                    const Path& tensor_output) {
+  if (tensor_output.Empty()) return nullptr;
+  if (!ShouldWrite(type_erased.Name(), layer_idx)) return nullptr;
+  char path[1024];
+  snprintf(path, sizeof(path), "%s/%s_L%02zu_%zux%zu_%s.bin",
+           tensor_output.path.c_str(), type_erased.Name(), layer_idx,
+           type_erased.Rows(), type_erased.Cols(),
+           TypeName(type_erased.GetType()));
+  return OpenFileOrAbort(Path(path), "wb");
+}
+
+void MaybeWriteRow(const std::unique_ptr<File>& file, const MatPtr& type_erased,
+                   size_t row_idx) {
+  if (!file) return;
+  const size_t bytes_per_row = type_erased.Cols() * type_erased.ElementBytes();
+  file->Write(type_erased.RowBytes(row_idx), bytes_per_row,
+              bytes_per_row * row_idx);
+}
+
+// First dispatch to the type, then parallel over rows, then vectorized
+// decompress and Notify for each value.
+void UpdateStatsT(TensorStats& stats, size_t layer_idx,
+                  const MatPtr& type_erased, ThreadingContext& ctx, int flags,
+                  size_t cluster_idx, Parallelism parallelism) {
+  std::unique_ptr<File> file =
+      MaybeOpenFile(layer_idx, type_erased, ctx.tensor_output);
+
+  if ((flags & kTensorStatsIsWeight) && layer_idx != 0) {
+    // Still compute stats, but remember not to print them.
+    stats.Get(layer_idx, 0).DoNotPrint();
+  }
+
+  CallUpcasted(&type_erased, [&](const auto* mat) {
+    const size_t cols = mat->Cols();
+
+    ParallelFor(
+        parallelism, mat->Rows(), ctx, cluster_idx, Callers::kTensorStats,
+        [&](size_t row_idx, size_t global_idx) {
+          GCPP_ZONE(ctx, global_idx, Zones::kGenStats);
+
+          auto* HWY_RESTRICT row = mat->Row(row_idx);
+          MaybeWriteRow(file, type_erased, row_idx);
+
+          using Packed = hwy::RemoveCvRef<decltype(*row)>;
+          PackedSpan<Packed> packed(const_cast<Packed*>(row), cols);
+
+          TensorStatsAccumulator& my_stats = stats.Get(layer_idx, global_idx);
+          my_stats.NotifyCond(ConditionNumber(row, cols));
+
+          namespace hn = hwy::HWY_NAMESPACE;
+          hn::ScalableTag<float> df;
+          using VF = hn::Vec<decltype(df)>;
+          HWY_LANES_CONSTEXPR size_t NF = hn::Lanes(df);
+          HWY_ALIGN float buf[2 * hn::MaxLanes(df)];
+
+          size_t packed_ofs = 0;
+          if (cols >= 2 * NF) {
+            for (; packed_ofs <= cols - 2 * NF; packed_ofs += 2 * NF) {
+              VF v0, v1;
+              Decompress2(df, packed, packed_ofs, v0, v1);
+              hn::Store(v0, df, buf);
+              hn::Store(v1, df, buf + NF);
+              const VF min_mag = hn::Min(hn::Abs(v0), hn::Abs(v1));
+              const VF max_mag = hn::Max(hn::Abs(v0), hn::Abs(v1));
+              const float min = hn::ReduceMin(df, min_mag);
+              if (min != 0.0f) {  // Avoid division by zero.
+                my_stats.NotifyGroup(min, hn::ReduceMax(df, max_mag));
+              }
+
+              for (size_t i = 0; i < 2 * NF; ++i) {
+                my_stats.Notify(buf[i], row_idx, packed_ofs + i);
+              }
+              my_stats.NotifyCorr(Correlation(buf, 2 * NF));
+            }
+          }
+
+          // Zero to two vectors remaining.
+          for (; packed_ofs < cols; packed_ofs += NF) {
+            const size_t remaining = HWY_MIN(NF, cols - packed_ofs);
+            DecompressAndZeroPad(df, packed, packed_ofs, buf, remaining);
+            // Skip NotifyGroup for this partial group.
+            for (size_t i = 0; i < remaining; ++i) {
+              my_stats.Notify(buf[i], row_idx, packed_ofs + i);
+            }
+            my_stats.NotifyCorr(Correlation(buf, remaining));
+          }
+        });
+  });
+}
+
+// NOLINTNEXTLINE(google-readability-namespace-comments)
+}  // namespace HWY_NAMESPACE
+}  // namespace gcpp
+HWY_AFTER_NAMESPACE();
+
+#if HWY_ONCE
+namespace gcpp {
+HWY_EXPORT(UpdateStatsT);
+
+// Must reside in .cc file so that we can #include compress-inl.h.
+void TensorStats::Notify(size_t layer_idx, const MatPtr& type_erased,
+                         ThreadingContext& ctx, int flags, size_t cluster_idx,
+                         Parallelism parallelism) {
+  // Ignore empty tensors.
+  if (type_erased.GetType() == Type::kUnknown || type_erased.Cols() == 0) {
+    return;
+  }
+  HWY_DYNAMIC_DISPATCH(UpdateStatsT)(*this, layer_idx, type_erased, ctx, flags,
+                                     cluster_idx, parallelism);
+}
+
+}  // namespace gcpp
+#endif  // HWY_ONCE
+
+#endif  // GCPP_TENSOR_STATS
diff --git a/gemma/tensor_stats.h b/gemma/tensor_stats.h
new file mode 100644
index 0000000..6975ab5
--- /dev/null
+++ b/gemma/tensor_stats.h
@@ -0,0 +1,347 @@
+// Copyright 2025 Google LLC
+// SPDX-License-Identifier: Apache-2.0
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     https://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#ifndef THIRD_PARTY_GEMMA_CPP_GEMMA_TENSOR_STATS_H_
+#define THIRD_PARTY_GEMMA_CPP_GEMMA_TENSOR_STATS_H_
+
+#include <stddef.h>
+#include <stdint.h>
+#include <stdio.h>
+
+#include "util/basics.h"
+#include "hwy/base.h"
+
+#ifndef GCPP_TENSOR_STATS
+#define GCPP_TENSOR_STATS 0
+#endif
+
+#include "util/mat.h"
+#include "util/threading_context.h"
+
+#if GCPP_TENSOR_STATS
+#include <cmath>
+#include <vector>
+
+#include "hwy/stats.h"
+#endif  // GCPP_TENSOR_STATS
+
+namespace gcpp {
+
+// For flags. Used to inhibit printing per-layer stats for weights.
+HWY_INLINE_VAR constexpr int kTensorStatsIsWeight = 1;
+
+#if GCPP_TENSOR_STATS
+
+HWY_INLINE_VAR constexpr size_t kStatsMaxCols = 8192;
+
+// Separate summary of the per-layer stats, updated by `TensorStatsAccumulator`.
+// We pass per-layer statistics such as the mean value to `hwy::Stats::Notify``
+// to see the distribution of per-layer means.
+struct TensorStatsAcrossLayers {
+  bool IsEmpty() const { return s_frobenius.Count() == 0; }
+
+  void Print() {
+    const int skip = hwy::Stats::kNoGeomean;
+    fprintf(stderr, "frob    %s\n", s_frobenius.ToString(skip).c_str());
+    fprintf(stderr, "cnd.min %s\n", s_cond_min.ToString(skip).c_str());
+    fprintf(stderr, "cnd.avg %s\n", s_cond_avg.ToString(skip).c_str());
+    fprintf(stderr, "cnd.max %s\n", s_cond_max.ToString(skip).c_str());
+    fprintf(stderr, "val.min %s\n", s_val_min.ToString(skip).c_str());
+    fprintf(stderr, "val.avg %s\n", s_val_avg.ToString(skip).c_str());
+    fprintf(stderr, "val.krt %s\n", s_val_kurt.ToString(skip).c_str());
+    fprintf(stderr, "mag.min %s\n", s_mag_min.ToString(skip).c_str());
+    fprintf(stderr, "mag.avg %s\n", s_mag_avg.ToString(skip).c_str());
+    fprintf(stderr, "mag.max %s\n", s_mag_max.ToString(skip).c_str());
+    if (hwy::ScalarAbs(s_corr_avg.Max()) > 0.05f) {
+      fprintf(stderr, "cor.avg %s\n", s_corr_avg.ToString(skip).c_str());
+    }
+    fprintf(stderr, "cor.max %s\n", s_corr_max.ToString(skip).c_str());
+    fprintf(stderr, "rng_avg %s\n", s_range_avg.ToString(skip).c_str());
+    fprintf(stderr, "exp.min %s\n", s_exp_min.ToString(skip).c_str());
+    fprintf(stderr, "exp.max %s\n", s_exp_max.ToString(skip).c_str());
+    fprintf(stderr, "exp.mod %s\n", s_exp_mode.ToString(skip).c_str());
+    if (s_exp_subnormal.Min() != 0.0f) {
+      fprintf(stderr, "exp.sub %s\n", s_exp_subnormal.ToString(skip).c_str());
+    }
+    if (s_big_cols.Count() != 0) {
+      fprintf(stderr, "bigCols %s\n", s_big_cols.ToString(skip).c_str());
+      const size_t modal_col = b_big_cols.ModalBinIdx();
+      const size_t num_outlier_cols = b_big_cols.NumNonzero();
+      if (num_outlier_cols > 256) {
+        fprintf(stderr, "bigCols: all up to %zu (max at %zu: %u layers):\n",
+                b_big_cols.LastNonzero(), modal_col, b_big_cols.Bin(modal_col));
+      } else {
+        fprintf(stderr, "bigCols (max at %zu: %u layers):\n", modal_col,
+                b_big_cols.Bin(modal_col));
+        for (size_t i = 0; i < kStatsMaxCols; ++i) {
+          if (b_big_cols.Bin(i) > 2) {
+            fprintf(stderr, " %3zu: %u\n", i, b_big_cols.Bin(i));
+          }
+        }
+      }
+    }
+    fprintf(stderr, "\n");
+  }
+
+  hwy::Stats s_frobenius;
+
+  hwy::Stats s_cond_min;
+  hwy::Stats s_cond_avg;
+  hwy::Stats s_cond_max;
+
+  hwy::Stats s_val_min;
+  hwy::Stats s_val_avg;
+  hwy::Stats s_val_kurt;
+
+  hwy::Stats s_mag_min;
+  hwy::Stats s_mag_avg;
+  hwy::Stats s_mag_max;
+
+  hwy::Stats s_corr_avg;
+  hwy::Stats s_corr_max;
+
+  hwy::Stats s_range_avg;
+
+  hwy::Stats s_exp_min;
+  hwy::Stats s_exp_max;
+  hwy::Stats s_exp_mode;
+  hwy::Stats s_exp_subnormal;
+
+  hwy::Stats s_big_cols;                // total number of outlier cols
+  hwy::Bins<kStatsMaxCols> b_big_cols;  // # layers with outlier per col
+};
+
+// Per-thread and layer.
+class TensorStatsAccumulator {
+ public:
+  void Notify(float val, size_t row_idx, size_t col_idx) {
+    const double dval = static_cast<double>(val);
+    sum_sq_ += dval * dval;
+
+    s_val_.Notify(val);
+    const float mag = hwy::ScalarAbs(val);
+
+    if (HWY_UNLIKELY(mag >= 64.0f)) {
+      if (row_idx < kMaxBatchSize) b_big_row_.Notify(row_idx);
+      if (col_idx < kStatsMaxCols) b_big_col_.Notify(col_idx);
+    }
+
+    // Skip zero so we can see the lowest actual magnitude
+    if (mag != 0.0f && mag != -0.0f) s_mag_.Notify(mag);
+
+    const uint32_t binary32 = hwy::BitCastScalar<uint32_t>(mag);
+    // Use biased exponent because Bins wants unsigned values.
+    const uint32_t biased_exp = binary32 >> 23;
+    HWY_DASSERT(biased_exp < 256);  // already cleared sign bit
+    b_exp256_.Notify(biased_exp);
+  }
+
+  void DoNotPrint() { skip_.fetch_or(1); }
+  bool ShouldPrint() const { return skip_.load() == 0; }
+
+  // Vector code computed the min/max of a group (= two vectors); this is
+  // faster than doing it in `Notify`.
+  void NotifyGroup(float min, float max) {
+    s_group_min_.Notify(min);
+    s_group_max_.Notify(max);
+    // Caller ensures min != 0.
+    s_group_range_.Notify(max / min);
+  }
+
+  void NotifyCorr(float corr) { s_corr_.Notify(corr); }
+  void NotifyCond(double cond) { s_cond_.Notify(cond); }
+
+  void Assimilate(const TensorStatsAccumulator& other) {
+    skip_.fetch_or(other.skip_.load());
+
+    sum_sq_ += other.sum_sq_;
+    b_exp256_.Assimilate(other.b_exp256_);
+    b_big_row_.Assimilate(other.b_big_row_);
+    b_big_col_.Assimilate(other.b_big_col_);
+    s_val_.Assimilate(other.s_val_);
+    s_mag_.Assimilate(other.s_mag_);
+    s_corr_.Assimilate(other.s_corr_);
+    s_group_min_.Assimilate(other.s_group_min_);
+    s_group_max_.Assimilate(other.s_group_max_);
+    s_group_range_.Assimilate(other.s_group_range_);
+  }
+
+  // Called on the per-layer representative after reducing across threads.
+  void NotifyAcrossLayer(TensorStatsAcrossLayers& s) {
+    s.s_frobenius.Notify(std::sqrt(sum_sq_));
+
+    s.s_cond_min.Notify(s_cond_.Min());
+    s.s_cond_avg.Notify(s_cond_.Mean());
+    s.s_cond_max.Notify(s_cond_.Max());
+
+    s.s_val_min.Notify(s_val_.Min());
+    s.s_val_avg.Notify(s_val_.Mean());
+    s.s_val_kurt.Notify(s_val_.Kurtosis());
+
+    s.s_mag_min.Notify(s_mag_.Min());
+    s.s_mag_avg.Notify(s_mag_.Mean());
+    s.s_mag_max.Notify(s_mag_.Max());
+
+    s.s_corr_avg.Notify(s_corr_.Mean());
+    s.s_corr_max.Notify(s_corr_.Max());
+
+    s.s_range_avg.Notify(s_group_range_.Mean());
+
+    const uint32_t subnormals = b_exp256_.Bin(0);
+    // Prevent subnormals from hiding the min exponent.
+    b_exp256_.ResetBin(0);
+    s.s_exp_min.Notify(b_exp256_.FirstNonzero());
+    s.s_exp_max.Notify(b_exp256_.LastNonzero());
+    s.s_exp_mode.Notify(b_exp256_.ModalBinIdx());
+    s.s_exp_subnormal.Notify(subnormals);
+
+    const uint32_t num_outliers = b_big_col_.NumNonzero();
+    if (num_outliers != 0) {
+      s.s_big_cols.Notify(num_outliers);
+      // For each col, count the number of layers that have an outlier there.
+      for (size_t i = 0; i < kStatsMaxCols; ++i) {
+        if (b_big_col_.Bin(i) != 0) s.b_big_cols.Notify(i);
+      }
+    }
+  }
+
+  bool IsEmpty() const { return s_val_.Count() == 0; }
+
+  void PrintAll() {
+    fprintf(stderr, "Frob %.2E\n", std::sqrt(sum_sq_));
+    const int skip = hwy::Stats::kNoGeomean;
+    fprintf(stderr, "cnd  %s\n", s_cond_.ToString(skip).c_str());
+    fprintf(stderr, "val  %s\n", s_val_.ToString(skip).c_str());
+    fprintf(stderr, "mag  %s\n", s_mag_.ToString(skip).c_str());
+    fprintf(stderr, "corr %s\n", s_corr_.ToString(skip).c_str());
+    fprintf(stderr, "group_min   %s\n", s_group_min_.ToString(skip).c_str());
+    fprintf(stderr, "group_max   %s\n", s_group_max_.ToString(skip).c_str());
+    fprintf(stderr, "group_range %s\n", s_group_range_.ToString(skip).c_str());
+    b_exp256_.Print("exp");
+    PrintBinRanges(b_big_row_, "big row");
+    PrintBinRanges(b_big_col_, "big col");
+    fprintf(stderr, "\n");
+  }
+
+ private:
+  template <size_t N>
+  void PrintBinRanges(const hwy::Bins<N>& b, const char* name) {
+    uint64_t total = 0;
+    for (size_t i = 0; i < N; ++i) {
+      total += b.Bin(i);
+    }
+    if (total == 0) return;
+
+    // If all bins are at least 10% of a uniform distribution, print the range
+    // to vastly reduce the log size.
+    const size_t min = HWY_MAX(1, total / (N * 10));
+    size_t last = 0;
+    for (; last < N; ++last) {
+      if (b.Bin(last) < min) break;
+    }
+    if (last >= N / 2) {
+      // Also require all subsequent bins to be zero, otherwise we should
+      // print the outlier bins.
+      bool all_zero = true;
+      for (size_t i = last + 1; i < N; ++i) {
+        if (b.Bin(last) != 0) {
+          all_zero = false;
+          break;
+        }
+      }
+      if (all_zero) {
+        fprintf(stderr, "%s: uniform up to %zu\n", name, last);
+        return;
+      }
+    }
+
+    b.Print(name, /*skip_zero=*/true);
+  }
+
+  double sum_sq_ = 0.0;      // for Frobenius norm
+  hwy::Bins<256> b_exp256_;  // exponent
+  hwy::Bins<kMaxBatchSize> b_big_row_;
+  hwy::Bins<kStatsMaxCols> b_big_col_;
+  hwy::Stats s_val_;
+  hwy::Stats s_mag_;
+  hwy::Stats s_cond_;  // condition number
+  hwy::Stats s_corr_;  // lag-1 autocorrelation
+  hwy::Stats s_group_min_;
+  hwy::Stats s_group_max_;
+  hwy::Stats s_group_range_;
+  std::atomic<int> skip_{0};
+};
+
+class TensorStats {
+ public:
+  TensorStats(size_t num_layers, size_t max_workers)
+      : num_layers_(num_layers),
+        max_workers_(max_workers),
+        acc_(num_layers * max_workers) {}
+
+  // Parallelized across rows. If `ctx.tensor_output` is not empty, writes
+  // tensor data to disk for offline analysis, once per tensor and layer.
+  void Notify(size_t layer_idx, const MatPtr& type_erased,
+              ThreadingContext& ctx, int flags = 0, size_t cluster_idx = 0,
+              Parallelism parallelism = Parallelism::kFlat);
+
+  // For use by `UpdateStatsT`.
+  TensorStatsAccumulator& Get(size_t layer_idx, size_t global_idx) {
+    const size_t idx = layer_idx * max_workers_ + global_idx;
+    HWY_DASSERT(idx < acc_.size());
+    return acc_[idx];
+  }
+
+  void ReduceAndPrint(const char* prefix) {
+    for (size_t layer_idx = 0; layer_idx < num_layers_; ++layer_idx) {
+      TensorStatsAccumulator& per_layer = Get(layer_idx, 0);
+      for (size_t global_idx = 1; global_idx < max_workers_; ++global_idx) {
+        per_layer.Assimilate(Get(layer_idx, global_idx));
+      }
+      if (per_layer.IsEmpty()) continue;
+      per_layer.NotifyAcrossLayer(across_layers_);
+      if (per_layer.ShouldPrint()) {
+        fprintf(stderr, "-------------------- %s %zu\n", prefix, layer_idx);
+        per_layer.PrintAll();
+      }
+    }
+
+    if (!across_layers_.IsEmpty()) {
+      fprintf(stderr, "================= across layers %s\n", prefix);
+      across_layers_.Print();
+    }
+  }
+
+ private:
+  size_t num_layers_;
+  size_t max_workers_;
+  std::vector<TensorStatsAccumulator> acc_;
+  TensorStatsAcrossLayers across_layers_;
+};
+
+#else  // GCPP_TENSOR_STATS
+
+class TensorStats {
+ public:
+  TensorStats(size_t, size_t) {}
+  void Notify(size_t, const MatPtr&, ThreadingContext&, int = 0, size_t = 0,
+              Parallelism = Parallelism::kFlat) {}
+  void ReduceAndPrint(const char*) {}
+};
+
+#endif  // GCPP_TENSOR_STATS
+}  // namespace gcpp
+
+#endif  // THIRD_PARTY_GEMMA_CPP_GEMMA_TENSOR_STATS_H_
diff --git a/gemma/vit.cc b/gemma/vit.cc
index b00efda..31c6f0f 100644
--- a/gemma/vit.cc
+++ b/gemma/vit.cc
@@ -78,13 +78,9 @@ class VitAttention {
     const float query_scale = 1.0f / sqrtf(static_cast<float>(qkv_dim));
     PROFILER_ZONE("Gen.VitAttention.DotSoftmax");
 
-    // Shift Q, K, VT to MatStorageT.
-    MatStorageT<float> Q("Q2", Extents2D(num_tokens_, qkv_dim),
-                         env_.ctx.allocator, MatPadding::kPacked);
-    MatStorageT<float> K("K2", Extents2D(seq_len, qkv_dim), env_.ctx.allocator,
-                         MatPadding::kPacked);
-    MatStorageT<float> C("C2", Extents2D(num_tokens_, seq_len),
-                         env_.ctx.allocator, MatPadding::kPacked);
+    MatPtrT<float>& Q = activations_.attention.vit_Q;
+    MatPtrT<float>& K = activations_.attention.vit_K;
+    MatPtrT<float>& C = activations_.attention.vit_C;
 
     // Initialize att_out to zero prior to head loop.
     ZeroInit(activations_.attention.att_out);
@@ -295,19 +291,20 @@ static HWY_NOINLINE void EmbedImagePatches(const Image& image,
   const size_t model_dim = model_config.vit_config.model_dim;
   const size_t patch_width = model_config.vit_config.patch_width;
   const size_t num_tokens = model_config.vit_config.seq_len;
-  const size_t patch_size = patch_width * patch_width * 3;
+  const size_t patch_area = patch_width * patch_width * 3;
+  const hwy::Divisor div_patch_dim(patch_width);
   HWY_DASSERT(weights.vit_img_embedding_kernel.Rows() == model_dim);
-  HWY_DASSERT(weights.vit_img_embedding_kernel.Cols() == patch_size);
+  HWY_DASSERT(weights.vit_img_embedding_kernel.Cols() == patch_area);
   HWY_DASSERT(activations.x.Cols() == model_dim);
   (void)model_dim;
   // img/embedding/kernel has original shape (14, 14, 3, 1152)
   // H x W x C x D transposed to D x (H x W x C) so here (1152, 14 * 14 * 3)
   // image_patches is (256, 14 * 14 * 3)
   // Must be padded, see `DoDecompressA`.
-  MatStorageT<float> image_patches("patches", Extents2D(num_tokens, patch_size),
+  MatStorageT<float> image_patches("patches", Extents2D(num_tokens, patch_area),
                                    env.ctx.allocator, MatPadding::kOdd);
   for (size_t i = 0; i < num_tokens; ++i) {
-    image.GetPatch(i, image_patches.Row(i));
+    image.GetPatch(i, div_patch_dim, image_patches.Row(i));
   }
   CallMatMul(image_patches, weights.vit_img_embedding_kernel,
              weights.vit_img_embedding_bias.PackedScale1(), env, activations.x);
diff --git a/gemma/weights.cc b/gemma/weights.cc
index e1e01bf..00c12c6 100644
--- a/gemma/weights.cc
+++ b/gemma/weights.cc
@@ -431,12 +431,12 @@ void WeightsPtrs::CopyFrom(const WeightsPtrs& other) {
 void WeightsPtrs::Fixup(std::vector<MatOwner>& mat_owners,
                         ThreadingContext& ctx) {
   const size_t cluster_idx = 0;
-  ParallelFor(ParallelismStrategy::kFlat, c_layers.size(), ctx, cluster_idx,
+  ParallelFor(Parallelism::kFlat, c_layers.size(), ctx, cluster_idx,
               Callers::kFixupWeights, [&](uint64_t layer, size_t /*worker*/) {
                 GetLayer(layer)->Fixup(mat_owners, ctx);
               });
 
-  ParallelFor(ParallelismStrategy::kFlat, vit_layers.size(), ctx, cluster_idx,
+  ParallelFor(Parallelism::kFlat, vit_layers.size(), ctx, cluster_idx,
               Callers::kFixupWeights, [&](uint64_t layer, size_t /*worker*/) {
                 VitLayer(layer)->Fixup(mat_owners, ctx);
               });
@@ -527,7 +527,7 @@ static void AllocateAndBindAll(std::vector<TensorToRead>& tensors,
 
   // Allocate in parallel because faulting in large tensors is slow.
   ParallelFor(
-      ParallelismStrategy::kFlat, tensors.size(), ctx, /*cluster_idx=*/0,
+      Parallelism::kFlat, tensors.size(), ctx, /*cluster_idx=*/0,
       Callers::kAllocateAndBindAll, [&](uint64_t task, size_t /*thread*/) {
         TensorToRead& tensor = tensors[task];
         MatPtr& mat = *tensor.mat;
@@ -586,10 +586,9 @@ static void DecompressToBF16(MatPtr& mat,
 static void ReadAllToBF16(const std::vector<TensorToRead>& tensors,
                           const BlobReader& reader, ThreadingContext& ctx) {
   // Especially TSAN is slow enough to warrant hierarchical parallelism.
-  const ParallelismStrategy strategy = HWY_IS_DEBUG_BUILD
-                                           ? ParallelismStrategy::kHierarchical
-                                           : ParallelismStrategy::kFlat;
-  ParallelFor(strategy, tensors.size(), ctx, /*cluster_idx=*/0,
+  const Parallelism parallelism =
+      HWY_IS_DEBUG_BUILD ? Parallelism::kHierarchical : Parallelism::kFlat;
+  ParallelFor(parallelism, tensors.size(), ctx, /*cluster_idx=*/0,
               Callers::kReadAllToBF16, [&](uint64_t task, size_t thread) {
                 GCPP_ZONE(ctx, thread, Zones::kStartupWeightsReadAllToBF16);
                 const TensorToRead& tensor = tensors[task];
@@ -677,7 +676,7 @@ static void ReadBatches(const BlobReader& reader,
                         const std::vector<IOBatch>& batches,
                         ThreadingContext& ctx) {
   // >5x speedup from parallel reads when cached.
-  ParallelFor(ParallelismStrategy::kHierarchical, batches.size(), ctx,
+  ParallelFor(Parallelism::kHierarchical, batches.size(), ctx,
               /*cluster_idx=*/0, Callers::kReadBatches,
               [&](uint64_t task, size_t thread) {
                 GCPP_ZONE(ctx, thread, Zones::kStartupWeightsReadBatches);
diff --git a/gemma/weights.h b/gemma/weights.h
index 3661869..4476e22 100644
--- a/gemma/weights.h
+++ b/gemma/weights.h
@@ -96,7 +96,8 @@ struct LayerWeightsPtrs {
   // other values for purposes of the KV cache.
   LayerWeightsPtrs(size_t layer_idx, const LayerConfig& config,
                    const TensorInfoRegistry& tensors)
-      : finder_(LayerSuffix(layer_idx), tensors),
+      : layer_idx(layer_idx),
+        finder_(LayerSuffix(layer_idx), tensors),
         qkv_einsum_w(finder_("qkv_ein")),
         qkv_einsum_w1(finder_("qkv1_w")),
         qkv_einsum_w2(finder_("qkv2_w")),
@@ -135,6 +136,7 @@ struct LayerWeightsPtrs {
   }
   ~LayerWeightsPtrs() = default;
 
+  const size_t layer_idx;
   const MatFinder finder_;
 
   // Files either have qkv_einsum_w with 2 stacked matrices or separate
diff --git a/io/blob_compare.cc b/io/blob_compare.cc
index 30a2199..9bb860e 100644
--- a/io/blob_compare.cc
+++ b/io/blob_compare.cc
@@ -106,7 +106,7 @@ void ReadBlobs(BlobReader& reader, const RangeVec& ranges, BlobVec& blobs,
                ThreadingContext& ctx, size_t cluster_idx) {
   HWY_ASSERT(reader.Keys().size() == blobs.size());
   HWY_ASSERT(ranges.size() == blobs.size());
-  ParallelFor(ParallelismStrategy::kWithinCluster, blobs.size(), ctx,
+  ParallelFor(Parallelism::kWithinCluster, blobs.size(), ctx,
               cluster_idx, Callers::kTest, [&](size_t i, size_t /*thread*/) {
                 HWY_ASSERT(ranges[i].bytes == blobs[i].size());
                 reader.file().Read(ranges[i].offset, ranges[i].bytes,
@@ -122,7 +122,7 @@ void ReadBothBlobs(BlobReader& reader1, BlobReader& reader2,
   const double t0 = hwy::platform::Now();
   HWY_WARN("Reading %zu GiB, %zu clusters: ", total_bytes >> 30,
            ctx.pools.NumClusters());
-  ParallelFor(ParallelismStrategy::kAcrossClusters, 2, ctx, 0, Callers::kTest,
+  ParallelFor(Parallelism::kAcrossClusters, 2, ctx, 0, Callers::kTest,
               [&](const size_t task, size_t cluster_idx) {
                 ReadBlobs(task ? reader1 : reader2, task ? ranges1 : ranges2,
                           task ? blobs1 : blobs2, ctx, cluster_idx);
@@ -189,7 +189,7 @@ void CompareBlobs(const KeyVec& keys, BlobVec& blobs1, BlobVec& blobs2,
   const double t0 = hwy::platform::Now();
   std::atomic<size_t> blobs_equal{};
   std::atomic<size_t> blobs_diff{};
-  ParallelFor(ParallelismStrategy::kHierarchical, keys.size(), ctx, 0,
+  ParallelFor(Parallelism::kHierarchical, keys.size(), ctx, 0,
               Callers::kTest, [&](size_t i, size_t /*thread*/) {
                 const size_t mismatches =
                     BlobDifferences(blobs1[i], blobs2[i], keys[i]);
diff --git a/io/blob_store.cc b/io/blob_store.cc
index af9f81d..8346e4b 100644
--- a/io/blob_store.cc
+++ b/io/blob_store.cc
@@ -488,11 +488,10 @@ void BlobWriter::Add(const std::string& key, const void* data, size_t bytes) {
   EnqueueChunks(keys_.size() - 1, curr_offset_, bytes,
                 static_cast<const uint8_t*>(data), writes);
 
-  const ParallelismStrategy strategy = file_->IsAppendOnly()
-                                           ? ParallelismStrategy::kNone
-                                           : ParallelismStrategy::kFlat;
+  const Parallelism parallelism =
+      file_->IsAppendOnly() ? Parallelism::kNone : Parallelism::kFlat;
   ParallelFor(
-      strategy, writes.size(), ctx_,
+      parallelism, writes.size(), ctx_,
       /*cluster_idx=*/0, Callers::kBlobWriter,
       [this, &writes](uint64_t i, size_t /*thread*/) {
         const BlobRange& range = writes[i].range;
diff --git a/io/blob_store.h b/io/blob_store.h
index e5f2221..82c2357 100644
--- a/io/blob_store.h
+++ b/io/blob_store.h
@@ -131,7 +131,7 @@ class BlobWriter {
   std::vector<size_t> blob_sizes_;
   ThreadingContext& ctx_;
   // Current offset in the file used for writing.
-  int64_t curr_offset_ = 0;
+  uint64_t curr_offset_ = 0;
 };
 
 }  // namespace gcpp
diff --git a/io/blob_store_test.cc b/io/blob_store_test.cc
index bb41c7e..cf96684 100644
--- a/io/blob_store_test.cc
+++ b/io/blob_store_test.cc
@@ -130,7 +130,7 @@ TEST(BlobStoreTest, TestNumBlobs) {
     HWY_ASSERT_EQ(reader.Keys().size(), num_blobs);
 
     ParallelFor(
-        ParallelismStrategy::kFlat, num_blobs, ctx, /*cluster_idx=*/0,
+        Parallelism::kFlat, num_blobs, ctx, /*cluster_idx=*/0,
         Callers::kTest, [&](uint64_t i, size_t /*thread*/) {
           HWY_ASSERT_STRING_EQ(reader.Keys()[i].c_str(),
                                std::to_string(i).c_str());
diff --git a/io/fields_test.cc b/io/fields_test.cc
index 37bb942..f720c15 100644
--- a/io/fields_test.cc
+++ b/io/fields_test.cc
@@ -20,6 +20,8 @@
 #include <stdio.h>
 
 #include <limits>
+#include <string>
+#include <vector>
 #include <type_traits>
 
 #include "hwy/tests/hwy_gtest.h"
diff --git a/io/io.cc b/io/io.cc
index 9363b07..2f479b2 100644
--- a/io/io.cc
+++ b/io/io.cc
@@ -110,7 +110,8 @@ class FilePosix : public File {
         HWY_WARN(
             "Read failure at pos %zu within size %zu with offset %zu and "
             "errno %d\n",
-            pos, size, offset, errno);
+            static_cast<size_t>(pos), static_cast<size_t>(size),
+            static_cast<size_t>(offset), errno);
         break;
       }
       pos += bytes_read;
@@ -130,7 +131,8 @@ class FilePosix : public File {
         HWY_WARN(
             "Write failure at pos %zu within size %zu with offset %zu and "
             "errno %d\n",
-            pos, size, offset, errno);
+            static_cast<size_t>(pos), static_cast<size_t>(size),
+            static_cast<size_t>(offset), errno);
         break;
       }
       pos += bytes_written;
@@ -194,9 +196,9 @@ std::unique_ptr<File> OpenFileOrNull(const Path& filename, const char* mode) {
 namespace gcpp {
 
 std::unique_ptr<File> OpenFileOrAbort(const Path& filename, const char* mode) {
-  std::unique_ptr<File> file = OpenFileOrNull(filename, "r");
+  std::unique_ptr<File> file = OpenFileOrNull(filename, mode);
   if (!file) {
-    HWY_ABORT("Failed to open %s", filename.path.c_str());
+    HWY_ABORT("Failed to open %s, errno %d", filename.path.c_str(), errno);
   }
   return file;
 }
@@ -234,7 +236,9 @@ bool IOBatch::Add(void* mem, size_t bytes) {
   return true;
 }
 
-void InternalInit() {
+int InternalInit() {
+  // currently unused, except for init list ordering in GemmaEnv.
+  return 0;
 }
 
 uint64_t IOBatch::Read(const File& file) const {
diff --git a/io/io.h b/io/io.h
index f90a636..d051715 100644
--- a/io/io.h
+++ b/io/io.h
@@ -150,7 +150,7 @@ std::string ReadFileToString(const Path& path);
 
 // No-op in open-source. Must be called at the beginning of a binary, before
 // any I/O or flag usage.
-void InternalInit();
+int InternalInit();
 
 }  // namespace gcpp
 
diff --git a/io/migrate_weights.cc b/io/migrate_weights.cc
index d20835f..beb268e 100644
--- a/io/migrate_weights.cc
+++ b/io/migrate_weights.cc
@@ -23,7 +23,9 @@ namespace gcpp {
 namespace {
 
 struct WriterArgs : public ArgsBase<WriterArgs> {
-  WriterArgs(int argc, char* argv[]) { InitAndParse(argc, argv); }
+  WriterArgs(int argc, char* argv[], ConsumedArgs& consumed) {
+    InitAndParse(argc, argv, consumed);
+  }
 
   Path output_weights;
 
@@ -38,12 +40,15 @@ struct WriterArgs : public ArgsBase<WriterArgs> {
 }  // namespace gcpp
 
 int main(int argc, char** argv) {
-  gcpp::WriterArgs args(argc, argv);
-  if (args.output_weights.Empty()) {
+  gcpp::ConsumedArgs consumed(argc, argv);
+  gcpp::GemmaArgs args(argc, argv, consumed);
+  gcpp::WriterArgs writer_args(argc, argv, consumed);
+  if (writer_args.output_weights.Empty()) {
     HWY_ABORT("Missing --output_weights flag, a file for the model weights.");
   }
+  consumed.AbortIfUnconsumed();
 
-  gcpp::GemmaEnv env(argc, argv);
-  env.GetGemma()->Save(args.output_weights, env.Env().ctx);
+  gcpp::GemmaEnv env(args);
+  env.GetGemma()->Save(writer_args.output_weights, env.Env().ctx);
   return 0;
 }
diff --git a/ops/dot-inl.h b/ops/dot-inl.h
index dae2106..ecf1ecf 100644
--- a/ops/dot-inl.h
+++ b/ops/dot-inl.h
@@ -413,7 +413,8 @@ using DotKernelDefault =
 template <class D, typename WT, typename VT>
 HWY_INLINE float Dot(D d, const PackedSpan<const WT>& w, size_t w_ofs,
                      const VT* HWY_RESTRICT vec, size_t num) {
-  return DecompressAndCall(d, w, w_ofs, MakeSpan(vec, num), DotKernelDefault());
+  return DecompressAndCall(d, w, w_ofs, MakeConstSpan(vec, num),
+                           DotKernelDefault());
 }
 
 // Adapter for two pointers, no bounds checking.
diff --git a/ops/dot_test.cc b/ops/dot_test.cc
index 827b6b4..bce8904 100644
--- a/ops/dot_test.cc
+++ b/ops/dot_test.cc
@@ -891,18 +891,6 @@ class DotStats {
   hwy::Stats s_times[kVariants];
 };
 
-// Returns normalized value in [-1, 1).
-float RandomFloat(RngStream& rng) {
-  const uint32_t exp = hwy::BitCastScalar<uint32_t>(1.0f);
-  const uint32_t mantissa_mask = hwy::MantissaMask<float>();
-  const uint32_t representation = exp | (rng() & mantissa_mask);
-  const float f12 = hwy::BitCastScalar<float>(representation);
-  HWY_DASSERT(1.0f <= f12 && f12 < 2.0f);  // exponent is 2^0, only mantissa
-  const float f = (2.0f * (f12 - 1.0f)) - 1.0f;
-  HWY_DASSERT(-1.0f <= f && f < 1.0f);
-  return f;
-}
-
 // `raw` holds the decompressed values, so that the test measures only the
 // error from the Dot algorithms, not the compression.
 template <typename Packed>
@@ -1126,7 +1114,7 @@ void TestAllDot() {
     std::array<DotStats, kMaxWorkers> all_stats;
 
     ParallelFor(
-        ParallelismStrategy::kWithinCluster, kReps, ctx, 0, Callers::kTest,
+        Parallelism::kWithinCluster, kReps, ctx, 0, Callers::kTest,
         [&](size_t rep, size_t thread) {
           float* HWY_RESTRICT pa = a.Row(thread);
           float* HWY_RESTRICT pb = b.Row(thread);
diff --git a/ops/matmul-inl.h b/ops/matmul-inl.h
index 96cd4f1..4b217a1 100644
--- a/ops/matmul-inl.h
+++ b/ops/matmul-inl.h
@@ -837,10 +837,11 @@ class MMImpl {
                                hwy::platform::InvariantTicksPerSecond();
     const double flops = 2 * M * K * N * num_B / min_elapsed;  // * 2 for FMA
     if (HWY_UNLIKELY(env.print_measurement && tuner.ShouldPrint())) {
-      fprintf(stderr, "%zu,%zu,%zu,%zu,%7.1f,%.2f,%zu,%4zu,%4zu,%5zu,%s,%zu\n",
-              M, K, N, num_B, flops * 1E-9, min_elapsed * 1E3, cfg.MR(),
-              cfg.MC(), cfg.KC(), cfg.NC(), StringFromOrder(cfg.Order()),
-              cfg.InnerTasks());
+      fprintf(
+          stderr,
+          "%4zu,%4zu,%4zu,B%zu,%7.1f,%.2f ms, MR%zu,%4zu,%4zu,%5zu,%-7s,%zu\n",
+          M, K, N, num_B, flops * 1E-9, min_elapsed * 1E3, cfg.MR(), cfg.MC(),
+          cfg.KC(), cfg.NC(), StringFromOrder(cfg.Order()), cfg.InnerTasks());
     }
     if (HWY_UNLIKELY(env.print_best && tuner.Best())) {
       const auto ratio = [&tuner](uint64_t ticks) -> double {
@@ -850,7 +851,8 @@ class MMImpl {
       const MMConfig& best = *tuner.Best();
       fprintf(
           stderr,
-          "\n%zu,%zu,%zu,%zu,%7.1f,%.2f,%zu,%4zu,%4zu,%5zu,%s,%zu,%.2f,%.2f\n",
+          "\n%4zu,%4zu,%4zu,B%zu,%7.1f,%.2f ms, MR%zu,%4zu,%4zu,%5zu,%-7s,%zu, "
+          "%.2fx,%.2fx\n",
           M, K, N, num_B, flops * 1E-9, min_elapsed * 1E3, best.MR(), best.MC(),
           best.KC(), best.NC(), StringFromOrder(best.Order()),
           best.InnerTasks(), ratio(tuner.WorstMinTicks()),
@@ -906,8 +908,8 @@ class MMLoops {
     const auto zone = args.env.ctx.profiler_zones.Get(Zones::kMMNT);
     HWY_DASSERT(args.ranges_mc.NumTasks() == 1);
     HWY_DASSERT(args.ranges_kc.NumTasks() == 1);
-    const IndexRange& range_mc = args.ranges_mc.Range(0);
-    const IndexRange& range_kc = args.ranges_kc.Range(0);
+    const IndexRange& range_mc = args.ranges_mc.Range(0);  // whole M
+    const IndexRange& range_kc = args.ranges_kc.Range(0);  // whole K
 
     parallel.ForN(
         args.env.ctx, args.range_n, MultipleN(sizeof(TC), args.line_bytes),
@@ -941,7 +943,7 @@ class MMLoops {
                               const MMArgs& args) {
     const auto zone = args.env.ctx.profiler_zones.Get(Zones::kMMNT_K);
     HWY_DASSERT(args.ranges_mc.NumTasks() == 1);
-    const IndexRange& range_mc = args.ranges_mc.Range(0);
+    const IndexRange& range_mc = args.ranges_mc.Range(0);  // whole M
 
     parallel.ForN(args.env.ctx, args.range_n,
                   MultipleN(sizeof(TC), args.line_bytes), args.inner_tasks,
@@ -977,7 +979,7 @@ class MMLoops {
                               const MMArgs& args) {
     const auto zone = args.env.ctx.profiler_zones.Get(Zones::kMMNT_MT);
     HWY_DASSERT(args.ranges_kc.NumTasks() == 1);
-    const IndexRange& range_kc = args.ranges_kc.Range(0);
+    const IndexRange& range_kc = args.ranges_kc.Range(0);  // whole K
 
     parallel.ForRangesMC_NC(
         args.env.ctx, args.ranges_mc, args.ranges_nc, args.options.cluster_idx,
@@ -1158,8 +1160,9 @@ HWY_NOINLINE MMPerKey* TwoMatMul(const MatPtrT<BF16>& A, const MatPtrT<TB>& B1,
     HWY_ASSERT(K <= MMEntireA::kMaxK);
     HWY_ASSERT(N % kNR == 0);
     MMImpl::EnsureAligned(A, cache.VectorBytes());
-    tuner.SetCandidates(
-        MMCandidates(cache, M, K, N, num_B, sizeof(BF16), env.print_config));
+    const size_t max_M = MMKeys::BucketM(M);
+    tuner.SetCandidates(MMCandidates(cache, max_M, K, N, num_B, sizeof(BF16),
+                                     env.print_config));
   }
 
   const MMConfig& cfg = tuner.NextConfig();
diff --git a/ops/matmul.cc b/ops/matmul.cc
index ebeff9b..c01943d 100644
--- a/ops/matmul.cc
+++ b/ops/matmul.cc
@@ -21,6 +21,7 @@
 #include <stdint.h>
 #include <stdio.h>
 
+#include <string>
 #include <vector>
 
 #include "util/allocator.h"
@@ -46,7 +47,9 @@ size_t RoundDownWithFloor(size_t value, size_t multiple) {
 // multiple of `multiple`, or 0 if none exists.
 size_t PrevDivisor(const size_t begin, const size_t end, const size_t dim,
                    const size_t multiple) {
-  HWY_DASSERT(end != 0 && dim != 0 && multiple != 0);
+  HWY_DASSERT(end != 0);
+  HWY_DASSERT(dim != 0);
+  HWY_DASSERT(multiple != 0);
   size_t prev = RoundDownWithFloor(end, multiple);
   // Avoid returning `end` if rounding down had no effect.
   if (prev == end) prev -= multiple;
@@ -62,10 +65,10 @@ size_t PrevDivisor(const size_t begin, const size_t end, const size_t dim,
 // and holds most of their arguments in member variables.
 class GenerateCandidates {
  public:
-  GenerateCandidates(const CacheInfo& cache, size_t M, size_t K, size_t N,
+  GenerateCandidates(const CacheInfo& cache, size_t max_M, size_t K, size_t N,
                      size_t num_B, size_t sizeof_TC, bool print_config)
       : cache_(cache),
-        M_(M),
+        max_M_(max_M),
         K_(K),
         N_(N),
         num_B_(num_B),
@@ -89,14 +92,14 @@ class GenerateCandidates {
           for (size_t mc : MC(mr, kc, order)) {
             for (size_t nc : NC(mr, mc, kc, order)) {
               for (int inner_tasks : all_inner_tasks) {
-                const MMConfig config(K_, N_, mr, mc, kc, nc, kc_multiple_,
-                                      nc_multiple_, order, inner_tasks);
-                const size_t M_tasks = config.RangesOfMC(M_).NumTasks();
+                const MMConfig config(max_M_, K_, N_, mr, mc, kc, nc,
+                                      kc_multiple_, nc_multiple_, order,
+                                      inner_tasks);
+                const size_t M_tasks = config.RangesOfMC(max_M_).NumTasks();
                 const size_t K_tasks = config.RangesOfKC(K_).NumTasks();
 
-                // Blocks only make sense when there are multiple M tasks.
-                if (IsBlock(order) != (M_tasks > 1)) continue;
-                // Single KC only makes sense when there is a single K task.
+                // Do not use single-MC/KC order if there are multiple.
+                if (IsOneMC(order) != (M_tasks == 1)) continue;
                 if (IsOneKC(order) != (K_tasks == 1)) continue;
 
                 candidates.push_back(config);
@@ -114,6 +117,25 @@ class GenerateCandidates {
  private:
   using SizeVec = std::vector<size_t>;
 
+  // Concatenate and print once because this can be called concurrently.
+  void MaybePrintSizes(size_t dim, size_t max, const char* caption,
+                       const SizeVec& sizes) const {
+    if (!print_config_ || sizes.empty()) return;
+    std::string out("num_B ");
+    out += std::to_string(num_B_);
+    out += " (";
+    out += std::to_string(dim);
+    out += ", max ";
+    out += std::to_string(max);
+    out += ") ";
+    out += caption;
+    out += ": ";
+    for (size_t size : sizes) {
+      out += std::to_string(size) + " ";
+    }
+    fprintf(stderr, "%s\n", out.c_str());
+  }
+
   // How many rows of A per call to `MMKernel::LoopKC`. Lower values may
   // be better for SIMD targets with fewer registers.
   SizeVec MR() const {
@@ -125,14 +147,14 @@ class GenerateCandidates {
     SizeVec all_mr;
     all_mr.reserve(3);
     // AVX2's 16 registers are not enough for four rows, but SSE4 may benefit.
-    if (M_ >= kMaxMR && !is_avx2) all_mr.push_back(kMaxMR);
+    if (max_M_ >= kMaxMR && !is_avx2) all_mr.push_back(kMaxMR);
     // Allow for AVX-512 but not SSE4 (for which 4 are usually better). Also
     // enable if not enough rows for 4.
-    if (M_ >= 2 && (M_ < kMaxMR || (!is_sse && !is_wasm))) {
+    if (max_M_ >= 2 && (max_M_ < kMaxMR || (!is_sse && !is_wasm))) {
       all_mr.push_back(size_t{2});
     }
     // Even SSE4 usually prefers 2 rows; only enable for single rows.
-    if (M_ == 1) all_mr.push_back(size_t{1});
+    if (max_M_ == 1) all_mr.push_back(size_t{1});
     HWY_ASSERT(!all_mr.empty());
     return all_mr;
   }
@@ -143,18 +165,26 @@ class GenerateCandidates {
     for (size_t order_idx = 0;; ++order_idx) {
       const MMOrder order = static_cast<MMOrder>(order_idx);
       if (StringFromOrder(order) == nullptr) return orders;  // done
-      // 2D blocking is useless for a single row of M.
-      if (IsBlock(order) && M_ <= mr) continue;
+      // Multiple-MC is useless for a single row of M.
+      if (!IsOneMC(order) && max_M_ <= mr) continue;
       // Conversely, N-only parallelism is uncompetitive for large M.
-      if (!IsBlock(order) && M_ >= kMaxTilesM * mr) continue;
+      if (IsOneMC(order) && max_M_ >= 8 * mr) continue;
       orders.push_back(order);
     }
   }
 
   // The number of A and B columns to read between updating `C`.
   SizeVec KC(size_t mr, MMOrder order) const {
+    if (IsOneKC(order)) {
+      // A single KC range is infeasible when K exceeds the max. The caller
+      // will skip all configs with `order`.
+      if (K_ > kMaxKC) return SizeVec();
+      // Must return the actual value: although ignored by `RangesOfKC`, this
+      // will be used in MC() and NC().
+      return SizeVec(1, K_);
+    }
     // `LoopKC` handles up to `mr` rows of A.
-    const size_t rows_a = HWY_MIN(M_, mr);
+    const size_t rows_a = HWY_MIN(max_M_, mr);
 
     // After looping over `kc` columns, we write `mr x 4` outputs and 16 vector
     // `buf`. To amortize the write cost, we want to maximize `kc`. However, it
@@ -186,7 +216,7 @@ class GenerateCandidates {
 
       // If we can afford a single K task, that's usually best; only try one
       // more. Otherwise, blocks may require smaller kc (more options).
-      const size_t reps = (kc_max == K_) ? 1 : IsBlock(order) ? 3 : 2;
+      const size_t reps = (kc_max == K_) ? 1 : IsOneMC(order) ? 2 : 3;
 
       size_t prev = kc_max;
       for (size_t rep = 0; rep < reps; ++rep) {
@@ -196,22 +226,27 @@ class GenerateCandidates {
       }
     }
 
-    if (print_config_ && all_kc.size() > 1) {
-      fprintf(stderr, "num_B %zu: KC: ", num_B_);
-      for (size_t kc : all_kc) {
-        fprintf(stderr, "%zu ", kc);
-      }
-      fprintf(stderr, "\n");
-    }
-
+    MaybePrintSizes(K_, kc_max, "KC", all_kc);
     return all_kc;
   }
 
   // The number of (L2 resident) A rows for `A2C0` to loop over.
   SizeVec MC(size_t mr, size_t kc, MMOrder order) const {
+    if (max_M_ <= mr) return SizeVec(1, max_M_);
+    if (IsOneMC(order)) {
+      // A single MC range is infeasible when M exceeds the max. The caller
+      // will skip all configs with `order`.
+      if (max_M_ > kMaxMC) return SizeVec();
+      // Must return the actual value: although ignored by `RangesOfMC`, this
+      // will be used in NC().
+      return SizeVec(1, max_M_);
+    }
+
     // Typically 12-24K. The B rows are pinned in L1, but also occupy L2 because
     // it is typically inclusive.
     const size_t bytes_b = kNR * kc * (sizeof(SfpStream) + sizeof(BF16));
+    // `kc` was chosen to fit in L1, hence this should not exceed L2.
+    HWY_ASSERT(bytes_b <= cache_.L2Bytes());
 
     // Choose the largest feasible `mc_max` (A/C rows) to maximize reuse of the
     // packed B. We want `mc * kc` elements of A to fit in L2, alongside
@@ -219,35 +254,45 @@ class GenerateCandidates {
     const size_t bytes_per_mc = kc * sizeof(BF16) + cache_.LineBytes();
     size_t mc_max = hwy::DivCeil(cache_.L2Bytes() - bytes_b, bytes_per_mc);
     mc_max = HWY_MIN(mc_max, HWY_MIN(kMaxBatchSize, kMaxMC));
-    HWY_DASSERT(mc_max != 0);
-    mc_max = HWY_MIN(mc_max, M_);
-    mc_max = hwy::RoundDownTo(mc_max, mr);
+    mc_max = HWY_MIN(mc_max, max_M_);
+    HWY_ASSERT(mc_max != 0);
 
-    SizeVec all_mc(1, mc_max);
-    // Larger MC is better for non-blocks, otherwise we want more small options,
-    // especially for two B.
-    const size_t reps = !IsBlock(order) ? 2 : (2 + num_B_);
+    SizeVec all_mc;
+    all_mc.reserve(6);
 
-    size_t prev = mc_max;
-    for (size_t rep = 0; rep < reps; ++rep) {
-      prev = PrevDivisor(1, prev, M_, mr);
-      if (prev >= mc_max || prev == 0) break;
+    const size_t rounded_M = HWY_MAX(mr, hwy::RoundDownTo(max_M_, mr));
+    size_t prev = hwy::RoundDownTo(mc_max, mr);
+
+    // If mc_max is large enough, allow using the whole range without rounding
+    // down (which may require two ranges).
+    if (mc_max == max_M_ && (max_M_ % mr) != 0) {
+      all_mc.push_back(max_M_);
+      // The next option should be considerably smaller than `max_M_`.
+      prev = HWY_MAX(mr, hwy::RoundDownTo(3 * prev / 4, mr));
+    } else {
       all_mc.push_back(prev);
     }
 
-    // Blocks: largest is not useful.
-    if (IsBlock(order) && all_mc.size() > 1) {
-      all_mc.erase(all_mc.begin(), all_mc.begin() + 1);
-    }
-
-    if (print_config_ && all_mc.size() > 1) {
-      fprintf(stderr, "num_B %zu: MC: ", num_B_);
-      for (size_t mc : all_mc) {
-        fprintf(stderr, "%zu ", mc);
+    // We know `order` is multiple MC, where more/smaller values of `mc` are
+    // helpful, especially for two B, hence add iterations.
+    const size_t reps = 2 + num_B_;
+    for (size_t rep = 0; rep < reps; ++rep) {
+      prev = PrevDivisor(mr, prev, rounded_M, mr);
+      if (prev == 0) break;  // none found
+      if (prev == mr) {
+        if (all_mc.back() != prev) all_mc.push_back(prev);
+        break;
       }
-      fprintf(stderr, "\n");
+      if (prev <= mc_max / 8) break;
+      all_mc.push_back(prev);
     }
 
+    if (all_mc.size() <= 2) {
+      if (max_M_ > mr) all_mc.push_back(max_M_ / 2);
+      if (mc_max > mr) all_mc.push_back(mc_max / 2);
+    }
+
+    MaybePrintSizes(max_M_, mc_max, "MC", all_mc);
     return all_mc;
   }
 
@@ -257,7 +302,7 @@ class GenerateCandidates {
     // Only if there will be reuse of B: choose the largest `nc_max` (C cols)
     // such that `nc x kc` of B and `mc x nc` of `C` fit in L3. Otherwise,
     // leave it unbounded.
-    if (M_ > mr) {
+    if (max_M_ > mr) {
       const size_t bytes_per_nc = (kc * sizeof(BF16) + mc * sizeof_TC_);
       nc_max = HWY_MIN(hwy::DivCeil(cache_.L3Bytes(), bytes_per_nc), kMaxNC);
     }
@@ -271,8 +316,8 @@ class GenerateCandidates {
       nc_max = RoundDownWithFloor(N_ / 2, nc_multiple_);
     }
 
-    // Non-block calls ForNP, which ignores `range_nc` and uses `range_np`.
-    if (!IsBlock(order)) return SizeVec(1, N_);
+    // Single-MC calls `ForNP`, which ignores `range_nc`.
+    if (IsOneMC(order)) return SizeVec(1, N_);
 
     SizeVec all_nc(1, nc_max);
 
@@ -282,7 +327,7 @@ class GenerateCandidates {
       // hence autotune a wider range of nc than the other dimensions.
       size_t reps = 9 + num_B_;
       // For small M, we can afford larger NC, hence allow fewer small options.
-      if (M_ <= 2 * mr) reps -= 1;
+      if (max_M_ <= 2 * mr) reps -= 1;
 
       size_t prev = nc_max;
       for (size_t rep = 0; rep < reps; ++rep) {
@@ -302,14 +347,7 @@ class GenerateCandidates {
                    all_nc.begin() + HWY_MIN(want_delete, max_delete));
     }
 
-    if (print_config_ && all_nc.size() > 1) {
-      fprintf(stderr, "num_B %zu: NC: ", num_B_);
-      for (size_t nc : all_nc) {
-        fprintf(stderr, "%zu ", nc);
-      }
-      fprintf(stderr, "\n");
-    }
-
+    MaybePrintSizes(N_, nc_max, "NC", all_nc);
     return all_nc;
   }
 
@@ -319,8 +357,8 @@ class GenerateCandidates {
     std::vector<int> inner_tasks;
     inner_tasks.reserve(3);
     inner_tasks.push_back(1);
-    // Blocks have one task per mc/nc range and ignore this parameter.
-    if (!IsBlock(order)) {
+    // Multiple-MC have one task per mc/nc range and ignore this parameter.
+    if (IsOneMC(order)) {
       inner_tasks.push_back(2);
       inner_tasks.push_back(4);
     }
@@ -328,7 +366,7 @@ class GenerateCandidates {
   }
 
   const CacheInfo& cache_;
-  const size_t M_;
+  const size_t max_M_;
   const size_t K_;
   const size_t N_;
   const size_t num_B_;
@@ -343,10 +381,11 @@ class GenerateCandidates {
 }  // namespace
 
 // Facade to avoid exposing `GenerateCandidates` in the header.
-std::vector<MMConfig> MMCandidates(const CacheInfo& cache, size_t M, size_t K,
-                                   size_t N, size_t num_B, size_t sizeof_TC,
-                                   bool print_config) {
-  return GenerateCandidates(cache, M, K, N, num_B, sizeof_TC, print_config)();
+std::vector<MMConfig> MMCandidates(const CacheInfo& cache, size_t max_M,
+                                   size_t K, size_t N, size_t num_B,
+                                   size_t sizeof_TC, bool print_config) {
+  return GenerateCandidates(cache, max_M, K, N, num_B, sizeof_TC,
+                            print_config)();
 }
 
 MatMulEnv::MatMulEnv(ThreadingContext& ctx)
diff --git a/ops/matmul.h b/ops/matmul.h
index ea7c090..85deb62 100644
--- a/ops/matmul.h
+++ b/ops/matmul.h
@@ -61,7 +61,7 @@ HWY_INLINE_VAR constexpr size_t kMaxNC = 16384;
 // of BF16 A and B fit in 32 KiB L1, but there may be `kMaxMR` and `kNR`.
 HWY_INLINE_VAR constexpr size_t kMaxKC = 8 * 1024;
 
-// Policy classes for parallelism, implementing some of `ParallelismStrategy`.
+// Policy classes for parallelism, implementing some of `Parallelism`.
 
 struct MMParallelNone {
   template <class Func>
@@ -103,18 +103,14 @@ struct MMParallelWithinCluster {
   template <class Func>
   void ForN(ThreadingContext& ctx, const IndexRange& range_n, size_t n_multiple,
             size_t inner_tasks, size_t cluster_idx, const Func& func) const {
-    HWY_DASSERT(1 <= inner_tasks && inner_tasks <= 4);
+    const hwy::pool::Caller caller =
+        ctx.pool_callers.Get(Callers::kMMClusterForN);
 
-    hwy::ThreadPool& cluster = ctx.pools.Cluster(cluster_idx);
-    const size_t base = ctx.Worker(cluster_idx);
-
-    const IndexRangePartition ranges_n = StaticPartition(
-        range_n, cluster.NumWorkers() * inner_tasks, n_multiple);
-    ParallelizeOneRange(ranges_n, cluster,
-                        ctx.pool_callers.Get(Callers::kMMClusterForN),
-                        [&](const IndexRange& worker_range, size_t worker) {
-                          func(worker_range, base + worker);
-                        });
+    ParallelPartitionWithinCluster(
+        range_n, n_multiple, inner_tasks, ctx, cluster_idx, caller,
+        [&](const IndexRange& worker_range, size_t worker) {
+          func(worker_range, worker);
+        });
   }
 
   template <class Func>
@@ -122,79 +118,56 @@ struct MMParallelWithinCluster {
                       const IndexRangePartition& ranges_mc,
                       const IndexRangePartition& ranges_nc, size_t cluster_idx,
                       const Func& func) const {
-    hwy::ThreadPool& cluster = ctx.pools.Cluster(cluster_idx);
-    const size_t base = ctx.Worker(cluster_idx);
+    const hwy::pool::Caller caller =
+        ctx.pool_callers.Get(Callers::kMMClusterForMCNC);
 
-    // Low-batch: avoid Divide/Remainder.
-    if (HWY_UNLIKELY(ranges_mc.NumTasks() == 1)) {
-      ParallelizeOneRange(ranges_nc, cluster,
-                          ctx.pool_callers.Get(Callers::kMMClusterForMCNC),
-                          [&](const IndexRange& range_nc, size_t worker) {
-                            func(ranges_mc.Range(0), range_nc, base + worker);
-                          });
-    } else {
-      ParallelizeTwoRanges(
-          ranges_mc, ranges_nc, cluster,
-          ctx.pool_callers.Get(Callers::kMMClusterForMCNC),
-          [&](const IndexRange& range_mc, const IndexRange& range_nc,
-              size_t worker) { func(range_mc, range_nc, base + worker); });
-    }
+    // We are running on one pool, hence collapse into a 1D range.
+    const hwy::Divisor div_m(static_cast<uint32_t>(ranges_mc.NumTasks()));
+    const auto get_mc = [&](uint64_t task) {
+      return ranges_mc.Range(div_m.Remainder(static_cast<uint32_t>(task)));
+    };
+    const auto get_nc = [&](uint64_t task) {
+      return ranges_nc.Range(div_m.Divide(static_cast<uint32_t>(task)));
+    };
+    const size_t num_tasks = ranges_mc.NumTasks() * ranges_nc.NumTasks();
+
+    ParallelForWithinCluster(num_tasks, ctx, cluster_idx, caller,
+                             [&](uint64_t task, size_t worker) {
+                               func(get_mc(task), get_nc(task), worker);
+                             });
   }
 
   template <class Func>
   void ForRangeMC(ThreadingContext& ctx, const IndexRange& range_mc,
                   size_t cluster_idx, const Func& func) const {
-    hwy::ThreadPool& cluster = ctx.pools.Cluster(cluster_idx);
-    const size_t base = ctx.Worker(cluster_idx);
+    const hwy::pool::Caller caller =
+        ctx.pool_callers.Get(Callers::kMMClusterForMC);
 
-    cluster.Run(
-        range_mc.begin(), range_mc.end(),
-        ctx.pool_callers.Get(Callers::kMMClusterForMC),
-        [&](uint64_t row_a, size_t worker) { func(row_a, base + worker); });
+    ParallelForWithinCluster(
+        range_mc.Num(), ctx, cluster_idx, caller,
+        [&](uint64_t i, size_t worker) { func(range_mc.begin() + i, worker); });
   }
 };
 
 struct MMParallelHierarchical {
-  // Cluster/CCX-aware parallel-for over B rows in `range_n`. `n_multiple` is
-  // the granularity of per-cluster tasks. Calls `func(worker_range, worker)`.
+  // Similar to `HierarchicalParallelFor`, but over *sub-ranges* of B rows in
+  // `range_n` governed by `n_multiple` and `inner_tasks`.
   template <class Func>
   void ForN(ThreadingContext& ctx, const IndexRange& range_n, size_t n_multiple,
-            size_t inner_tasks, HWY_MAYBE_UNUSED size_t caller_cluster_idx,
+            size_t inner_tasks, size_t caller_cluster_idx,
             const Func& func) const {
-    HWY_DASSERT(1 <= inner_tasks && inner_tasks <= 4);
     HWY_DASSERT(caller_cluster_idx == 0);
+    (void)caller_cluster_idx;
     const hwy::pool::Caller caller = ctx.pool_callers.Get(Callers::kMMHierForN);
 
-    // Single cluster: parallel-for over static partition of `range_n`.
-    hwy::ThreadPool& all_clusters = ctx.pools.AllClusters();
-    const size_t num_clusters = all_clusters.NumWorkers();
-    if (num_clusters == 1) {
-      const size_t cluster_idx = 0;
-      hwy::ThreadPool& cluster = ctx.pools.Cluster(cluster_idx);
-      const IndexRangePartition ranges_n = StaticPartition(
-          range_n, cluster.NumWorkers() * inner_tasks, n_multiple);
-      return ParallelizeOneRange(
-          ranges_n, cluster, caller,
-          [&](const IndexRange& worker_range, size_t worker) {
-            func(worker_range, worker);
-          });
-    }
-
-    // Assign each cluster a sub-range of `range_n` (typically hundreds).
-    const IndexRangePartition ranges_n =
-        StaticPartition(range_n, num_clusters, n_multiple);
-    ParallelizeOneRange(
-        ranges_n, all_clusters, caller,
-        [&](const IndexRange& n_range, const size_t cluster_idx) {
-          hwy::ThreadPool& cluster = ctx.pools.Cluster(cluster_idx);
-          const size_t cluster_base = ctx.Worker(cluster_idx);
-          // Parallel-for over sub-ranges of `cluster_range` within the cluster.
-          const IndexRangePartition worker_ranges = StaticPartition(
-              n_range, cluster.NumWorkers() * inner_tasks, n_multiple);
-          ParallelizeOneRange(
-              worker_ranges, cluster, caller,
+    // Assign clusters (if any) a sub-range of `range_n` (typically hundreds).
+    ParallelPartitionAcrossClusters(
+        range_n, n_multiple, /*inner_tasks=*/1, ctx, caller,
+        [&](const IndexRange& cluster_range, size_t cluster_idx) {
+          ParallelPartitionWithinCluster(
+              cluster_range, n_multiple, inner_tasks, ctx, cluster_idx, caller,
               [&](const IndexRange& worker_range, size_t worker) {
-                func(worker_range, cluster_base + worker);
+                func(worker_range, worker);
               });
         });
   }
@@ -205,69 +178,56 @@ struct MMParallelHierarchical {
   void ForRangesMC_NC(ThreadingContext& ctx,
                       const IndexRangePartition& ranges_mc,
                       const IndexRangePartition& ranges_nc,
-                      HWY_MAYBE_UNUSED size_t caller_cluster_idx,
-                      const Func& func) const {
+                      size_t caller_cluster_idx, const Func& func) const {
     HWY_DASSERT(caller_cluster_idx == 0);
+    (void)caller_cluster_idx;
     const hwy::pool::Caller caller =
         ctx.pool_callers.Get(Callers::kMMHierForMCNC);
 
-    hwy::ThreadPool& all_clusters = ctx.pools.AllClusters();
-    // `all_clusters` is a pool with one worker per cluster in a package.
-    const size_t num_clusters = all_clusters.NumWorkers();
-    // Single (big) cluster: collapse two range indices into one parallel-for
-    // to reduce the number of fork-joins.
-    if (num_clusters == 1) {
-      const size_t cluster_idx = 0;
-      hwy::ThreadPool& cluster = ctx.pools.Cluster(cluster_idx);
-      // Low-batch: avoid Divide/Remainder.
-      if (HWY_UNLIKELY(ranges_mc.NumTasks() == 1)) {
-        return ParallelizeOneRange(
-            ranges_nc, cluster, caller,
-            [&](const IndexRange& range_nc, size_t worker) {
-              func(ranges_mc.Range(0), range_nc, worker);
-            });
-      } else {
-        return ParallelizeTwoRanges(
-            ranges_mc, ranges_nc, cluster, caller,
-            [&](const IndexRange& range_mc, const IndexRange& range_nc,
-                size_t worker) { func(range_mc, range_nc, worker); });
-      }
-    }
+    // Collapse two range indices into a 1D range for better load-balancing,
+    // because `ranges_mc` may just have one task.
+    const hwy::Divisor div_m(static_cast<uint32_t>(ranges_mc.NumTasks()));
+    const auto get_mc = [&](uint64_t task) {
+      return ranges_mc.Range(div_m.Remainder(static_cast<uint32_t>(task)));
+    };
+    const auto get_nc = [&](uint64_t task) {
+      return ranges_nc.Range(div_m.Divide(static_cast<uint32_t>(task)));
+    };
+    const IndexRange all_range(0, ranges_mc.NumTasks() * ranges_nc.NumTasks());
 
-    // Multiple clusters: N across clusters (both are usually the larger), and
-    // M within each cluster. We assume auto-tuning finds small MC/NC tasks.
-    ParallelizeOneRange(
-        ranges_nc, all_clusters, caller,
-        [&](const IndexRange range_nc, size_t cluster_idx) {
-          const size_t cluster_base = ctx.Worker(cluster_idx);
-          hwy::ThreadPool& cluster = ctx.pools.Cluster(cluster_idx);
-          ParallelizeOneRange(ranges_mc, cluster, caller,
-                              [&](const IndexRange& range_mc, size_t worker) {
-                                func(range_mc, range_nc, cluster_base + worker);
-                              });
+    ParallelPartitionAcrossClusters(
+        all_range, /*task_multiple=*/1, /*inner_tasks=*/1, ctx, caller,
+        [&](const IndexRange& cluster_range, size_t cluster_idx) {
+          ParallelForWithinCluster(cluster_range.Num(), ctx, cluster_idx,
+                                   caller, [&](uint64_t i, size_t worker) {
+                                     const size_t task =
+                                         cluster_range.begin() + i;
+                                     func(get_mc(task), get_nc(task), worker);
+                                   });
         });
   }
 
-  // Calls `func(row_a, worker)` in parallel.
+  // No multiple/inner_tasks, so this is just HierarchicalParallelFor.
   template <class Func>
   void ForRangeMC(ThreadingContext& ctx, const IndexRange& range_mc,
                   size_t caller_cluster_idx, const Func& func) const {
-    HierarchicalParallelFor(range_mc.Num(), ctx, Callers::kMMHierForMC,
-                            [&](size_t task, size_t worker) {
-                              func(range_mc.begin() + task, worker);
-                            });
+    HWY_DASSERT(caller_cluster_idx == 0);
+    (void)caller_cluster_idx;
+    HierarchicalParallelFor(
+        range_mc.Num(), ctx, Callers::kMMHierForMC,
+        [&](size_t i, size_t worker) { func(range_mc.begin() + i, worker); });
   }
 };
 
 template <class Func, typename... Args>
-void DispatchParallelism(ParallelismStrategy parallelism, const Func& func,
+void DispatchParallelism(Parallelism parallelism, const Func& func,
                          Args&&... args) {
   switch (parallelism) {
-    case ParallelismStrategy::kNone:
+    case Parallelism::kNone:
       return func(MMParallelNone(), std::forward<Args>(args)...);
-    case ParallelismStrategy::kWithinCluster:
+    case Parallelism::kWithinCluster:
       return func(MMParallelWithinCluster(), std::forward<Args>(args)...);
-    case ParallelismStrategy::kHierarchical:
+    case Parallelism::kHierarchical:
       return func(MMParallelHierarchical(), std::forward<Args>(args)...);
     default:
       HWY_UNREACHABLE;
@@ -371,8 +331,8 @@ void DispatchOrder(MMOrder order, const Func& func, Args&&... args) {
   }
 }
 
-static inline bool IsBlock(MMOrder order) {
-  return order == MMOrder::kNT_MT_K || order == MMOrder::kNT_MT;
+static inline bool IsOneMC(MMOrder order) {
+  return order == MMOrder::kNT || order == MMOrder::kNT_K;
 }
 
 static inline bool IsOneKC(MMOrder order) {
@@ -421,6 +381,8 @@ static inline const char* StringFromParA(MMParA par_a) {
 // `mc` := A rows such that `kc` columns fit in L2,
 // `nc` := B rows such that `kc` columns fit in L3 alongside `mc x nc` C.
 // Also includes loop order and task granularity.
+//
+// This is shared by multiple M which return the same `BucketM`.
 #pragma pack(push, 1)
 class MMConfig {
  public:
@@ -428,8 +390,8 @@ class MMConfig {
   // `mr` is the number of A rows per call to `MMKernel::LoopKC`.
   // `MMOrder` is how to parallelize the outer loops.
   // `inner_tasks` chooses the within-cluster task granularity in `ForN`.
-  MMConfig(size_t K, size_t N, size_t mr, size_t mc, size_t kc, size_t nc,
-           size_t kc_multiple, size_t nc_multiple, MMOrder order,
+  MMConfig(size_t M, size_t K, size_t N, size_t mr, size_t mc, size_t kc,
+           size_t nc, size_t kc_multiple, size_t nc_multiple, MMOrder order,
            int inner_tasks)
       : mr_(static_cast<uint32_t>(mr)),
         mc_(static_cast<uint32_t>(mc)),
@@ -441,11 +403,7 @@ class MMConfig {
         inner_tasks_(static_cast<uint8_t>(inner_tasks)),
         reserved_{} {
     HWY_DASSERT(mr == 1 || mr == 2 || mr == 4);
-    if (mc % mr != 0) {
-      HWY_WARN("mc %zu not a multiple of mr %zu", mc, mr);
-    }
-    // Do not warn for single-kc tasks; some models unfortunately have K which
-    // are not multiples of `kc_multiple`.
+    // Some models have K which are not multiples of `kc_multiple`.
     if (kc != K && (kc % kc_multiple) != 0) {
       HWY_WARN("kc %zu not a multiple of kc_multiple %zu", kc, kc_multiple);
     }
@@ -457,11 +415,21 @@ class MMConfig {
   }
 
   // Splits M/N into blocks which are visited sequentially or in parallel.
-  // K is always sequential, see `MMOrder`.
   IndexRangePartition RangesOfMC(size_t M) const {
-    return MaxSizePartition(IndexRange(0, M), mc_, mr_);
+    if (IsOneMC(order_)) {
+      // Must have exactly one M range/tile, regardless of `mr_` and `mc_`.
+      return IndexRangePartition(M);
+    }
+    const size_t mc = HWY_MIN(M, MC());
+    const size_t mr = HWY_MIN(M, MR());
+    return MaxSizePartition(IndexRange(0, M), mc, mr);
   }
+  // K is either a single range, or a sequential loop.
   IndexRangePartition RangesOfKC(size_t K) const {
+    if (IsOneKC(order_)) {
+      // Must have exactly one K range/tile, regardless of `kc_`.
+      return IndexRangePartition(K);
+    }
     return MaxSizePartition(IndexRange(0, K), kc_, kc_multiple_);
   }
   IndexRangePartition RangesOfNC(size_t N) const {
@@ -488,7 +456,7 @@ class MMConfig {
   uint32_t kc_multiple_;
   MMOrder order_;
   uint8_t inner_tasks_;
-  HWY_MAYBE_UNUSED uint8_t reserved_[6];
+  HWY_MEMBER_VAR_MAYBE_UNUSED uint8_t reserved_[6];
 };
 static_assert(sizeof(MMConfig) == 32);  // for faster indexing
 #pragma pack(pop)
@@ -597,26 +565,27 @@ class MMAutoTune {
 
 //------------------------------------------------------------------------------
 
-// Minimum M, in units of tile rows of height mr={1, 2, 4}, from which
-// `MMOrder::kNT[_K]` are no longer allowed. They require a single MC range,
-// but choosing the same config for a larger M can result in multiple MC ranges.
-// Thus M less than this must have unique keys/configs.
-HWY_INLINE_VAR constexpr size_t kMaxTilesM = 8;
-
 // Map of previously seen dimensions to index via linear search.
 class MMKeys {
-  // Group batch size into buckets to reduce #auto-tunes.
-  static size_t BucketM(size_t M) {
-    if (M < kMaxTilesM * kMaxMR) return M;  // See kMaxTilesM above.
-    if (M <= 128) return 128;
-    return 512;
-  }
-
  public:
   using Key = uint64_t;
   // KeyFromDims will only return this if all dims are zero, which is invalid.
   static constexpr Key kPadding = 0;
 
+  // Returns the maximum permissible M in the bucket, for grouping batch sizes
+  // into buckets to reduce #auto-tunes.
+  static size_t BucketM(size_t M) {
+    HWY_DASSERT(M != 0);
+    // Small M: 1..3, 4..7, 8..15, etc. share the same config.
+    if (M < 64) return M | (kMaxMR - 1);
+    // Larger M use power of two buckets: 64..127, 128..255, etc.
+    const size_t floor_log2_M =
+        31 - hwy::Num0BitsAboveMS1Bit_Nonzero32(static_cast<uint32_t>(M));
+    const size_t min_M = size_t{1} << floor_log2_M;
+    HWY_DASSERT(min_M <= M && M < 2 * min_M);
+    return 2 * min_M - 1;
+  }
+
   // Compresses the dimensions into a single Key for faster comparison.
   static Key KeyFromDims(size_t M, size_t K, size_t N, size_t num_B) {
     HWY_DASSERT(M < (Key{1} << 16));  // batch sizes are smaller
@@ -747,7 +716,7 @@ class MMOptions {
   const void* opaque = nullptr;
 
   uint32_t cluster_idx = 0;  // for `parallelism == kWithinCluster`.
-  ParallelismStrategy parallelism = ParallelismStrategy::kHierarchical;
+  Parallelism parallelism = Parallelism::kHierarchical;
 };
 
 // Arguments to MatMul() that are independent of the A/B/C types. Reduces
diff --git a/ops/matmul_test.cc b/ops/matmul_test.cc
index 2aaf301..4787122 100644
--- a/ops/matmul_test.cc
+++ b/ops/matmul_test.cc
@@ -195,9 +195,10 @@ HWY_INLINE void MatMulSlow(const MatPtrT<TA> A, const MatPtrT<TB> B,
   const size_t multiple = env.ctx.allocator.QuantumBytes() / sizeof(TB);
   const IndexRangePartition get_col_c =
       StaticPartition(all_cols_c, all_clusters.NumWorkers(), multiple);
-  ParallelizeOneRange(
-      get_col_c, all_clusters, env.ctx.pool_callers.Get(Callers::kTest),
-      [&](const IndexRange& cols_c, size_t cluster_idx) HWY_ATTR {
+  ParallelForAcrossClusters(
+      get_col_c.NumTasks(), env.ctx, env.ctx.pool_callers.Get(Callers::kTest),
+      [&](size_t range_idx, size_t cluster_idx) HWY_ATTR {
+        const IndexRange cols_c = get_col_c.Range(range_idx);
         for (size_t r : all_rows_c) {
           TC* HWY_RESTRICT C_row = C.Row(r);
           for (size_t c : cols_c) {
diff --git a/ops/ops-inl.h b/ops/ops-inl.h
index f2933ca..0eeec31 100644
--- a/ops/ops-inl.h
+++ b/ops/ops-inl.h
@@ -25,9 +25,11 @@
 #include <cstdint>
 #include <random>
 #include <type_traits>  // std::enable_if_t
+#include <utility>
 #include <vector>
 
 #include "ops/matmul.h"
+#include "ops/ops.h"
 #include "util/allocator.h"
 #include "util/basics.h"  // TokenAndProb, RngStream
 #include "util/mat.h"
@@ -61,6 +63,9 @@ namespace gcpp {
 namespace HWY_NAMESPACE {
 namespace hn = hwy::HWY_NAMESPACE;
 
+// Computes C = A * B + add via MatMulStatic.
+// This function uses CallUpcasted to dispatch to the correct MatMulStatic
+// instantiation based on the runtime type of B.
 template <typename TA, typename TC>
 MMPerKey* CallMatMul(const MatPtrT<TA>& A, const MatPtr& B,
                      const float* HWY_RESTRICT add, MatMulEnv& env,
@@ -497,10 +502,10 @@ void RMSNormBatched(const MatPtrT<XT>& activations, const MatPtr& weights,
                     size_t cluster_idx = 0) {
   HWY_DASSERT(weights.Rows() == 1);
   HWY_DASSERT(weights.Cols() == activations.Cols());
-  HWY_DASSERT(activations.SameShape(out));
+  activations.DebugCheckSameShape(out);
 
   CallUpcasted(&weights, [&](const auto* weights_t) {
-    ParallelFor(ParallelismStrategy::kFlat, activations.Rows(), ctx,
+    ParallelFor(Parallelism::kFlat, activations.Rows(), ctx,
                 cluster_idx, Callers::kOpsRMSNormBatched,
                 [&](uint64_t token_idx, size_t worker) {
                   RMSNorm(activations.Row(token_idx), weights_t->PackedScale1(),
@@ -517,7 +522,7 @@ void RMSNormInplaceBatched(const MatPtr& weights, MatPtrT<XT>& inout,
   HWY_DASSERT(weights.Cols() == inout.Cols());
 
   CallUpcasted(&weights, [&](const auto* weights_t) {
-    ParallelFor(ParallelismStrategy::kFlat, inout.Rows(), ctx, cluster_idx,
+    ParallelFor(Parallelism::kFlat, inout.Rows(), ctx, cluster_idx,
                 Callers::kOpsRMSNormInplaceBatched,
                 [&](uint64_t token_idx, size_t worker) {
                   RMSNormInplace(weights_t->PackedScale1(), /*w_ofs=*/0,
@@ -550,7 +555,7 @@ static HWY_INLINE void AddFromBatched(const MatPtrT<XT>& x, MatPtrT<float>& out,
                                       size_t cluster_idx = 0) {
   HWY_DASSERT(out.SameShape(x));
   ParallelFor(
-      ParallelismStrategy::kFlat, out.Rows(), ctx, cluster_idx,
+      Parallelism::kFlat, out.Rows(), ctx, cluster_idx,
       Callers::kOpsAddFromBatched, [&](uint64_t token_idx, size_t worker) {
         AddFrom(x.Row(token_idx), out.Row(token_idx), x.Cols(), ctx, worker);
       });
@@ -1122,9 +1127,25 @@ HWY_NOINLINE HWY_MAYBE_UNUSED void MulByConstAndAddVector(
 
 // See below for a specialized version for top-1 sampling.
 // TODO: support bf16 logits using Decompress2.
+// Computes softmax probabilities for the given logits, normalizing in-place.
+// The calculation is numerically stable, using the max-subtraction trick to
+// compute exp(logits[i] - max(logits)) before normalizing by the sum.
+// If temperature is provided and not 1.0, each intermediate exp() result is
+// divided by temperature before normalization; however, this division by
+// temperature cancels out during the final normalization step, meaning
+// temperature currently has no effect on the output probabilities.
+// @param logits In-out: on input, contains logits; on output, overwritten with
+// probabilities.
+// @param ctx Input: threading context for parallelism and profiling.
+// @param worker Input: worker thread index.
+// @param temperature Input: softmax temperature.
+// @param softmax_max_out Optional output: if not null, stores the max logit
+// value.
+// @param softmax_d_out Optional output: if softmax_max is not null, this must
+// not be null and stores the sum of exp(logit - max).
 static HWY_NOINLINE void Softmax(Logits logits, ThreadingContext& ctx,
-                                 const size_t worker,
-                                 float temperature = 1.0f) {
+                                 const size_t worker, float temperature = 1.0f,
+                                 const SMOptions& sm_options = {}) {
   GCPP_ZONE(ctx, worker, Zones::kOpsSoftmax);
   HWY_DASSERT(logits.size() != 0);
 
@@ -1168,6 +1189,10 @@ static HWY_NOINLINE void Softmax(Logits logits, ThreadingContext& ctx,
   // Double-precision reciprocal does not appear to affect the results.
   const float mul = 1.0f / sum_exp;
   MulByConst(mul, logits.data(), logits.size());
+  if (sm_options.max_out) {
+    *sm_options.max_out = hn::GetLane(vmax);
+    *sm_options.d_out = sum_exp;
+  }
 }
 
 // Note: https://arxiv.org/pdf/2001.04438 proposes to replace the three max /
@@ -1290,7 +1315,7 @@ static HWY_INLINE HWY_MAYBE_UNUSED void MaybeLogitsSoftCapBatched(
     const float cap, MatPtrT<float>& x, const hwy::BitSet4096<>& non_eos,
     ThreadingContext& ctx, size_t cluster_idx = 0) {
   if (cap == 0.0f) return;
-  ParallelFor(ParallelismStrategy::kFlat, x.Rows(), ctx, cluster_idx,
+  ParallelFor(Parallelism::kFlat, x.Rows(), ctx, cluster_idx,
               Callers::kOpsMaybeLogitsSoftCapBatched,
               [&](uint64_t task, size_t worker) {
                 if (non_eos.Get(task)) {
diff --git a/ops/ops.h b/ops/ops.h
index 03b023b..002cb97 100644
--- a/ops/ops.h
+++ b/ops/ops.h
@@ -41,6 +41,11 @@ static inline HWY_MAYBE_UNUSED MatStorageT<float> CreateInvTimescale(
   return inv_timescale;
 }
 
+struct SMOptions {
+  float* HWY_RESTRICT max_out = nullptr;
+  float* HWY_RESTRICT d_out = nullptr;
+};
+
 }  // namespace gcpp
 
 #endif  // THIRD_PARTY_GEMMA_CPP_OPS_OPS_H_
diff --git a/ops/ops_test.cc b/ops/ops_test.cc
index 4d94b61..0f83df1 100644
--- a/ops/ops_test.cc
+++ b/ops/ops_test.cc
@@ -14,7 +14,6 @@
 // limitations under the License.
 
 #include "compression/types.h"
-#include "util/zones.h"
 #ifndef HWY_DISABLED_TARGETS
 #define HWY_DISABLED_TARGETS GEMMA_DISABLED_TARGETS
 #endif  // HWY_DISABLED_TARGETS
@@ -38,7 +37,6 @@
 #include "util/mat.h"     // MatStorageT
 #include "util/test_util.h"
 #include "util/threading_context.h"
-#include "hwy/profiler.h"
 #include "hwy/tests/hwy_gtest.h"
 
 // clang-format off
@@ -348,6 +346,51 @@ void TestAllSoftmax() {
   hn::ForPartialVectors<ForeachCountAndMisalign<TestSoftmax>>()(float());
 }
 
+class TestSoftmaxState {
+ public:
+  template <class D>
+  void operator()(D d, size_t count, size_t misalign_a, size_t misalign_b,
+                  hwy::RandomState& rng) {
+    if (count == 0) return;  // *Softmax would assert
+    if (misalign_b == 0) return;
+    using T = hn::TFromD<D>;
+
+    hwy::AlignedFreeUniquePtr<T[]> px =
+        hwy::AllocateAligned<T>(HWY_MAX(1, misalign_a + count));
+    hwy::AlignedFreeUniquePtr<T[]> pe =
+        hwy::AllocateAligned<T>(HWY_MAX(1, misalign_a + count));
+    HWY_ASSERT(px && pe);
+
+    T* x = px.get() + misalign_a;
+    T* initial_logits = pe.get() + misalign_a;
+
+    for (size_t i = 0; i < count; ++i) {
+      x[i] = Random<T>(rng);
+      initial_logits[i] = x[i];
+    }
+
+    float softmax_max;
+    float softmax_d;
+    Softmax(Logits(x, count), Ctx(), /*worker=*/0, /*temperature=*/1.0f,
+            {.max_out = &softmax_max, .d_out = &softmax_d});
+
+    const float maxval =
+        *std::max_element(initial_logits, initial_logits + count);
+
+    float sum_exp = 0.0f;
+    for (size_t i = 0; i < count; ++i) {
+      sum_exp += std::exp(initial_logits[i] - maxval);
+    }
+
+    ASSERT_NEAR(softmax_max, maxval, 1e-6);
+    ASSERT_NEAR(softmax_d, sum_exp, 1e-6);
+  }
+};
+
+void TestAllSoftmaxState() {
+  hn::ForPartialVectors<ForeachCountAndMisalign<TestSoftmaxState>>()(float());
+}
+
 template <size_t k>
 struct TestCreateDistribution {
   void operator()(hwy::RandomState& rng) {
@@ -456,7 +499,7 @@ void TestRopeAndMulBy() {
     x.Row(0)[i] = random_float();
   }
 
-  const float qmul = AttentionActivations::ChooseQueryScale(config);
+  const float qmul = ChooseQueryScale(config);
   constexpr float kmul = 1.0f;
 
   MatStorageT<float> qexpected("qexpected", dim_qkv, ctx.allocator);
@@ -771,6 +814,7 @@ HWY_EXPORT_AND_TEST_P(OpsTest, TestAllMulByConst);
 HWY_EXPORT_AND_TEST_P(OpsTest, TestAllMulByConstTo);
 HWY_EXPORT_AND_TEST_P(OpsTest, TestAllMulByConstAndAdd);
 HWY_EXPORT_AND_TEST_P(OpsTest, TestAllSoftmax);
+HWY_EXPORT_AND_TEST_P(OpsTest, TestAllSoftmaxState);
 HWY_EXPORT_AND_TEST_P(OpsTest, TestAllCreateDistribution);
 HWY_EXPORT_AND_TEST_P(OpsTest, TestAllSigmoid);
 HWY_EXPORT_AND_TEST_P(OpsTest, TestAllGelu);
diff --git a/paligemma/BUILD.bazel b/paligemma/BUILD.bazel
index 7a2e870..cc6c6e1 100644
--- a/paligemma/BUILD.bazel
+++ b/paligemma/BUILD.bazel
@@ -29,6 +29,7 @@ cc_test(
     deps = [
         ":image",
         "@googletest//:gtest_main",  # buildcleaner: keep
+        "@highway//:hwy",
     ],
 )
 
diff --git a/paligemma/image.cc b/paligemma/image.cc
index 20ecad8..d8b0cfc 100644
--- a/paligemma/image.cc
+++ b/paligemma/image.cc
@@ -37,8 +37,6 @@
 
 namespace gcpp {
 namespace {
-// Hardcoded for PaliGemma ViT input.
-constexpr size_t kPatchSize = 14;
 
 // Returns the linearly scaled index in [0, to_size) closest to the
 // value in [0, from_size).
@@ -208,24 +206,25 @@ bool Image::WriteBinary(const std::string& filename) const {
 }
 
 // Image.data() is H x W x 3.
-// We want the N-th patch of size kPatchSize x kPatchSize x 3.
-void Image::GetPatch(size_t patch_num, float* patch) const {
+// We want the N-th patch of size patch_dim x patch_dim x 3.
+void Image::GetPatch(size_t patch_num, const hwy::Divisor& div_patch_dim,
+                     float* patch) const {
   PROFILER_FUNC;
   constexpr size_t kNumChannels = 3;
-  constexpr size_t kBytesPerPixel = (kNumChannels * sizeof(float));
-  constexpr size_t kBytesPerRow = (kPatchSize * kBytesPerPixel);
-  const size_t kDataSize = width_ * height_ * kNumChannels;
+  constexpr size_t kBytesPerPixel = kNumChannels * sizeof(float);
+  const size_t patch_dim = div_patch_dim.GetDivisor();
+  const size_t bytes_per_row = (patch_dim * kBytesPerPixel);
   const size_t in_bytes_to_next_row = (width_ * kBytesPerPixel);
-  HWY_ASSERT(size() == kDataSize);
-  HWY_ASSERT(width_ % kPatchSize == 0);
-  HWY_ASSERT(height_ % kPatchSize == 0);
-  const size_t kNumPatchesPerRow = width_ / kPatchSize;
-  size_t patch_y = patch_num / kNumPatchesPerRow;
-  size_t patch_x = patch_num % kNumPatchesPerRow;
-  HWY_ASSERT(0 <= patch_y && patch_y < height_ / kPatchSize);
-  HWY_ASSERT(0 <= patch_x && patch_x < kNumPatchesPerRow);
-  patch_y *= kPatchSize;
-  patch_x *= kPatchSize;
+  HWY_ASSERT(size() == width_ * height_ * kNumChannels);
+  HWY_ASSERT(div_patch_dim.Remainder(width_) == 0);
+  HWY_ASSERT(div_patch_dim.Remainder(height_) == 0);
+  const size_t patches_x = div_patch_dim.Divide(width_);
+  size_t patch_y = patch_num / patches_x;
+  size_t patch_x = patch_num % patches_x;
+  HWY_DASSERT(0 <= patch_y && patch_y < div_patch_dim.Divide(height_));
+  HWY_DASSERT(0 <= patch_x && patch_x < patches_x);
+  patch_y *= patch_dim;
+  patch_x *= patch_dim;
 
   // Move `out` and `in` to the start of the patch.
   char* out = reinterpret_cast<char*>(patch);
@@ -233,9 +232,9 @@ void Image::GetPatch(size_t patch_num, float* patch) const {
   in += (((patch_y * width_) + patch_x) * kBytesPerPixel);
 
   // Copy the patch one row at a time.
-  for (size_t y = 0; y < kPatchSize; ++y) {
-    std::memcpy(out, in, kBytesPerRow);
-    out += kBytesPerRow;
+  for (size_t y = 0; y < patch_dim; ++y) {
+    std::memcpy(out, in, bytes_per_row);
+    out += bytes_per_row;
     in += in_bytes_to_next_row;
   }
 }
diff --git a/paligemma/image.h b/paligemma/image.h
index e0b1530..e54bf86 100644
--- a/paligemma/image.h
+++ b/paligemma/image.h
@@ -21,6 +21,7 @@
 #include <vector>
 
 #include "hwy/aligned_allocator.h"  // Span
+#include "hwy/base.h"               // Divisor
 
 namespace gcpp {
 
@@ -44,11 +45,12 @@ class Image {
   bool WriteBinary(const std::string& filename) const;
   // Stores the patch for the given patch number in `patch`.
   // Patches are numbered in usual raster-order. E.g. for an image of size
-  // 224 x 224, there are 16 x 16 = 256 patches.
-  // `patch` should have space for at least 14 * 14 * 3 = 588 floats.
+  // 224 x 224 and patch_dim = 14, there are 16 x 16 = 256 patches.
+  // `patch` should have space for at least patch_dim * patch_dim * 3.
   // Requires that Normalize() has been called and that the image width and
-  // height are multiples of 14.
-  void GetPatch(size_t patch_num, float* patch) const;
+  // height are multiples of patch_dim.
+  void GetPatch(size_t patch_num, const hwy::Divisor& div_patch_dim,
+                float* patch) const;
 
   float *data() { return data_.data(); }
   const float *data() const { return data_.data(); }
diff --git a/paligemma/image_test.cc b/paligemma/image_test.cc
index e2c4bbf..3721363 100644
--- a/paligemma/image_test.cc
+++ b/paligemma/image_test.cc
@@ -20,6 +20,7 @@
 #include <vector>
 
 #include "gtest/gtest.h"
+#include "hwy/base.h"
 
 namespace gcpp {
 namespace {
@@ -61,11 +62,12 @@ TEST(ImageTest, LoadResize224GetPatch) {
   EXPECT_EQ(image.data()[image.size() - 1], Normalize(122));
   // Extract two patches.
   float patch[588];
-  image.GetPatch(0, patch);
+  const hwy::Divisor div_patch_dim(14);
+  image.GetPatch(0, div_patch_dim, patch);
   EXPECT_EQ(patch[0], Normalize(160));
   EXPECT_EQ(patch[1], Normalize(184));
   EXPECT_EQ(patch[2], Normalize(188));
-  image.GetPatch(18, patch);
+  image.GetPatch(18, div_patch_dim, patch);
   // Check the first row of the patch.
   for (size_t i = 0; i < 14 * 3; ++i) {
     EXPECT_EQ(patch[i], image.data()[(14 * 224 + 2 * 14) * 3 + i]);
@@ -108,14 +110,15 @@ TEST(ImageTest, Non224) {
   // Extract two patches.
   const size_t kPatchValues = 14 * 14 * 3;  // = 588
   float patch[kPatchValues];
+  const hwy::Divisor div_patch_dim(14);
   // Patch 0 is just the "start" of the image.
-  image.GetPatch(0, patch);
+  image.GetPatch(0, div_patch_dim, patch);
   EXPECT_NEAR(patch[0], Normalize(0.0f, max_value), 1e-6);
   EXPECT_NEAR(patch[1], Normalize(1.0f, max_value), 1e-6);
   EXPECT_NEAR(patch[2], Normalize(2.0f, max_value), 1e-6);
   // The "image" has 4x3 patches, so patch 6 has coordinates (1, 2) and its
   // pixel coordinates are offset by (14, 28).
-  image.GetPatch(6, patch);
+  image.GetPatch(6, div_patch_dim, patch);
   for (size_t n = 0; n < kPatchValues; ++n) {
     size_t k = n % 3;
     size_t j = ((n - k) / 3) % 14;
diff --git a/paligemma/paligemma_test.cc b/paligemma/paligemma_test.cc
index 0a7401a..7bfd78c 100644
--- a/paligemma/paligemma_test.cc
+++ b/paligemma/paligemma_test.cc
@@ -21,10 +21,9 @@
 #include "evals/benchmark_helper.h"
 #include "gemma/configs.h"
 #include "gemma/gemma.h"
-#include "io/io.h"
+#include "paligemma/paligemma_helper.h"
 #include "util/allocator.h"
 #include "hwy/tests/hwy_gtest.h"
-#include "paligemma/paligemma_helper.h"
 
 // This test can be run manually with the downloaded PaliGemma weights.
 // It should pass for `paligemma-3b-mix-224` and `paligemma2-3b-pt-448`.
@@ -72,9 +71,12 @@ TEST_F(PaliGemmaTest, QueryObjects) {
 
 int main(int argc, char** argv) {
   testing::InitGoogleTest(&argc, argv);
-  gcpp::InternalInit();
 
-  gcpp::GemmaEnv env(argc, argv);
+  gcpp::ConsumedArgs consumed(argc, argv);
+  gcpp::GemmaArgs args(argc, argv, consumed);
+  consumed.AbortIfUnconsumed();
+
+  gcpp::GemmaEnv env(args);
   gcpp::s_env = &env;
 
   return RUN_ALL_TESTS();
diff --git a/python/configs.cc b/python/configs.cc
index e544bb0..0d505dc 100644
--- a/python/configs.cc
+++ b/python/configs.cc
@@ -173,6 +173,8 @@ PYBIND11_MODULE(configs, py_module) {
       .def_readwrite("secondary_eos_id", &ModelConfig::secondary_eos_id)
       .def_readwrite("scale_base_names", &ModelConfig::scale_base_names)
       .def_readwrite("internal", &ModelConfig::internal)
+      .def_readwrite("use_global_timescale",
+                     &ModelConfig::use_global_timescale)
 
       .def("add_layer_config", &ModelConfig::AddLayerConfig,
            arg("layer_config"))
diff --git a/python/gemma_py.cc b/python/gemma_py.cc
index 1bab194..0d056d9 100644
--- a/python/gemma_py.cc
+++ b/python/gemma_py.cc
@@ -45,10 +45,7 @@ static void RemoveTrailingZeros(std::vector<int> &vec) {
 // Wrapper around GemmaEnv to expose to Python.
 class GemmaModel {
  public:
-  GemmaModel(const gcpp::LoaderArgs& loader,
-             const gcpp::ThreadingArgs& threading,
-             const gcpp::InferenceArgs& inference)
-      : env_(loader, threading, inference), last_prob_(0.0f) {}
+  GemmaModel(const gcpp::GemmaArgs& args) : env_(args), last_prob_(0.0f) {}
 
   // Generates a single example, given a prompt and a callback to stream the
   // generated tokens.
@@ -254,13 +251,15 @@ PYBIND11_MODULE(gemma, mod) {
   py::class_<GemmaModel>(mod, "GemmaModel")
       .def(py::init([](const std::string& tokenizer, const std::string& weights,
                        size_t max_threads) {
-             const gcpp::LoaderArgs loader(tokenizer, weights);
              gcpp::ThreadingArgs threading;
              threading.max_lps = max_threads;
+
              gcpp::InferenceArgs inference;
              inference.max_generated_tokens = 512;
-             auto gemma =
-                 std::make_unique<GemmaModel>(loader, threading, inference);
+
+             const gcpp::GemmaArgs args(gcpp::LoaderArgs(tokenizer, weights),
+                                        threading, inference);
+             auto gemma = std::make_unique<GemmaModel>(args);
              if (!gemma->ModelIsLoaded()) {
                throw std::invalid_argument("Could not load model.");
              }
diff --git a/util/args.h b/util/args.h
index 32d54fb..8c6423b 100644
--- a/util/args.h
+++ b/util/args.h
@@ -22,6 +22,7 @@
 
 #include <algorithm>  // std::transform
 #include <string>
+#include <vector>
 
 #include "io/io.h"        // Path
 #include "util/basics.h"  // Tristate
@@ -29,6 +30,56 @@
 
 namespace gcpp {
 
+// For checking which args were not matched/consumed. Passed to each `*Args`
+// ctor that parses argc/argv to ensure that their args are tracked, without
+// requiring global state.
+class ConsumedArgs {
+ public:
+  ConsumedArgs(int argc, char** argv) : argv_(argv), consumed_(argc) {
+    // We assume argc >= 1, because argv[0] is the binary name. That allows us
+    // to signal "called AbortIfUnconsumed" with an empty vector.
+    HWY_ASSERT(!consumed_.empty());
+  }
+
+  ~ConsumedArgs() {
+    if (HWY_UNLIKELY(!consumed_.empty())) {
+      HWY_ABORT("AbortIfUnconsumed was not called.");
+    }
+  }
+
+  void NotifyConsumed(size_t idx) {
+    HWY_ASSERT(idx < consumed_.size());
+    HWY_ASSERT(consumed_[idx] == 0);
+    consumed_[idx] = 1;
+  }
+
+  // Returns index of first unconsumed arg, or 0 if none. Also disarms the
+  // warning in the dtor checking whether this/`AbortIfUnconsumed` were called.
+  size_t FirstUnconsumed() {
+    // Ignore argv[0], which is the binary name.
+    for (size_t i = 1; i < consumed_.size(); ++i) {
+      if (HWY_UNLIKELY(consumed_[i] == 0)) {
+        consumed_.clear();
+        return i;
+      }
+    }
+
+    consumed_.clear();
+    return 0;
+  }
+
+  void AbortIfUnconsumed() {
+    const size_t i = FirstUnconsumed();
+    if (HWY_UNLIKELY(i != 0)) {
+      HWY_ABORT("Unrecognized arg %zu: %s\n", i, argv_[i]);
+    }
+  }
+
+ private:
+  char** argv_;
+  std::vector<uint8_t> consumed_;
+};
+
 // Args is a class that provides a ForEach member function which visits each of
 // its member variables. ArgsBase provides functions called by Args to
 // initialize values to their defaults (passed as an argument to the visitor),
@@ -93,12 +144,14 @@ class ArgsBase {
   // consider adding a hash-map to speed this up.
   class ParseVisitor {
    public:
-    ParseVisitor(int argc, char* argv[]) : argc_(argc), argv_(argv) {}
+    ParseVisitor(int argc, char* argv[], ConsumedArgs& consumed)
+        : argc_(argc), argv_(argv), consumed_(consumed) {}
 
     template <typename T>
     void operator()(T& t, const char* name, const T& /*init*/,
                     const char* /*help*/, int /*print_verbosity*/ = 0) const {
       const std::string prefixed = std::string("--") + name;
+      const std::string prefixed_eq = prefixed + "=";
       for (int i = 1; i < argc_; ++i) {
         if (std::string(argv_[i]) == prefixed) {
           if (i + 1 >= argc_) {
@@ -107,6 +160,16 @@ class ArgsBase {
           if (!SetValue(argv_[i + 1], t)) {
             HWY_ABORT("Invalid value for %s, got %s\n", name, argv_[i + 1]);
           }
+          consumed_.NotifyConsumed(i);
+          consumed_.NotifyConsumed(i + 1);
+          return;
+        }
+        if (std::string(argv_[i]).find(prefixed_eq) == 0) {
+          const char* value = argv_[i] + prefixed_eq.length();
+          if (!SetValue(value, t)) {
+            HWY_ABORT("Invalid value for %s, got %s\n", name, value);
+          }
+          consumed_.NotifyConsumed(i);
           return;
         }
       }
@@ -173,8 +236,9 @@ class ArgsBase {
       }
     }
 
-    int argc_;
-    char** argv_;
+    const int argc_;
+    char** const argv_;
+    ConsumedArgs& consumed_;
   };  // ParseVisitor
 
   template <class Visitor>
@@ -203,15 +267,15 @@ class ArgsBase {
     ForEach(visitor);
   }
 
-  void Parse(int argc, char* argv[]) {
-    ParseVisitor visitor(argc, argv);
+  void Parse(int argc, char* argv[], ConsumedArgs& consumed) {
+    ParseVisitor visitor(argc, argv, consumed);
     ForEach(visitor);
   }
 
   // For convenience, enables single-line constructor.
-  void InitAndParse(int argc, char* argv[]) {
+  void InitAndParse(int argc, char* argv[], ConsumedArgs& consumed) {
     Init();
-    Parse(argc, argv);
+    Parse(argc, argv, consumed);
   }
 };
 
diff --git a/util/basics.h b/util/basics.h
index 5a7f0d5..49996ba 100644
--- a/util/basics.h
+++ b/util/basics.h
@@ -33,6 +33,9 @@ namespace gcpp {
 // For hwy::BitSet4096. Note that KVs are extremely large for such batches.
 HWY_INLINE_VAR constexpr size_t kMaxBatchSize = 4096;
 
+// Multiplier so a u64 occupies an entire cache line; avoids false sharing.
+HWY_INLINE_VAR constexpr size_t kU64PerLine = HWY_ALIGNMENT / sizeof(uint64_t);
+
 enum class Tristate : int32_t { kFalse = 0, kTrue = 1, kDefault = -1 };
 
 static inline const char* ToString(Tristate t) {
diff --git a/util/mat.h b/util/mat.h
index 59eceaa..83d03b1 100644
--- a/util/mat.h
+++ b/util/mat.h
@@ -181,7 +181,15 @@ class MatPtr : public IFields {
   Extents2D Extents() const { return Extents2D(Rows(), cols_); }
   bool IsEmpty() const { return Rows() == 0 || cols_ == 0; }
   bool SameShape(const MatPtr& other) const {
-    return Rows() == other.Rows() && cols_ == other.cols_;
+    return Rows() == other.Rows() && Cols() == other.Cols();
+  }
+  void DebugCheckSameShape(const MatPtr& other) const {
+    if constexpr (HWY_IS_DEBUG_BUILD) {
+      if (!SameShape(other)) {
+        HWY_ABORT("%s: shape mismatch %zu x %zu vs %zu x %zu\n", name_.c_str(),
+                  Rows(), Cols(), other.Rows(), Cols());
+      }
+    }
   }
   // Future calls to `Rows()` during this class' lifetime (not serialized)
   // will return this value. Used to set the actual number of rows for
@@ -284,6 +292,9 @@ class MatPtrT : public MatPtr {
  public:
   using T = MatT;
 
+  // Default constructor for use with uninitialized views.
+  MatPtrT() = default;
+
   // Called by `MatStorageT`.
   MatPtrT(const char* name, Extents2D extents)
       : MatPtr(name, TypeEnum<MatT>(), extents) {}
@@ -296,7 +307,10 @@ class MatPtrT : public MatPtr {
     if (GetType() == Type::kUnknown) {
       SetType(TypeEnum<MatT>());
     } else {
-      HWY_ASSERT(other.GetType() == TypeEnum<MatT>());
+      if (HWY_UNLIKELY(other.GetType() != TypeEnum<MatT>())) {
+        HWY_ABORT("Type mismatch: MatT %s, constructing from %s",
+                  TypeName<MatT>(), TypeName(other.GetType()));
+      }
     }
   }
   MatPtrT& operator=(const MatPtr& other) {
@@ -440,6 +454,21 @@ decltype(auto) CallUpcastedActivation(const MatPtr* base, const Func& func,
   }
 }
 
+// Like CallUpcasted, but only for kv_cache types: kBF16 and kF32.
+template <class Func, typename... Args>
+decltype(auto) CallUpcastedKV(const MatPtr* base, const Func& func,
+                                      Args&&... args) {
+  if (base->GetType() == Type::kF32) {
+    const MatPtrT<float> mat(*base);
+    return func(&mat, std::forward<Args>(args)...);
+  } else if (base->GetType() == Type::kBF16) {
+    const MatPtrT<BF16> mat(*base);
+    return func(&mat, std::forward<Args>(args)...);
+  } else {
+    HWY_ABORT("Unhandled type %s.", TypeName(base->GetType()));
+  }
+}
+
 void CopyMat(const MatPtr& from, MatPtr& to);
 void ZeroInit(MatPtr& mat);
 
diff --git a/util/test_util.h b/util/test_util.h
index 355b096..f0c37f9 100644
--- a/util/test_util.h
+++ b/util/test_util.h
@@ -19,20 +19,51 @@
 #include <stddef.h>
 #include <stdint.h>
 
+#include <algorithm>  // std::sort
 #include <cmath>
+#include <iostream>
 
+#include "util/basics.h"  // RngStream
+#include "util/mat.h"
 #include "hwy/base.h"
 
 // IWYU pragma: begin_exports
+#include "hwy/nanobenchmark.h"
 #include "hwy/stats.h"
 #include "hwy/tests/test_util.h"  // RandomState
 // IWYU pragma: end_exports
 
 namespace gcpp {
 
+// Excludes outliers; we might not have enough samples for a reliable mode.
+HWY_INLINE double TrimmedMean(double* seconds, size_t num) {
+  std::sort(seconds, seconds + num);
+  double sum = 0;
+  int count = 0;
+  for (size_t i = num / 4; i < num / 2; ++i) {
+    sum += seconds[i];
+    count += 1;
+  }
+  HWY_DASSERT(num != 0);
+  return sum / count;
+}
+
+// Returns normalized value in [-1, 1).
+HWY_INLINE float RandomFloat(RngStream& rng) {
+  const uint32_t exp = hwy::BitCastScalar<uint32_t>(1.0f);
+  const uint32_t mantissa_mask = hwy::MantissaMask<float>();
+  const uint32_t representation = exp | (rng() & mantissa_mask);
+  const float f12 = hwy::BitCastScalar<float>(representation);
+  HWY_DASSERT(1.0f <= f12 && f12 < 2.0f);  // exponent is 2^0, only mantissa
+  const float f = (2.0f * (f12 - 1.0f)) - 1.0f;
+  HWY_DASSERT(-1.0f <= f && f < 1.0f);
+  return f;
+}
+
 // Returns random Gaussian (mean=0, stddev=1/3 similar to expected weights)
 // using the central limit theorem. Avoid std::normal_distribution for
 // consistent cross-platform output.
+// TODO: use RngStream instead of RandomState.
 HWY_INLINE double RandomGaussian(hwy::RandomState& rng) {
   uint64_t sum = 0;
   constexpr int kReps = 40;
@@ -71,6 +102,25 @@ HWY_INLINE void VerifyGaussian(hwy::Stats& stats) {
   HWY_ASSERT(IsNear(3.0, stats.Kurtosis(), 0.3));
 }
 
+template <typename T>
+void FillMatPtrT(MatPtrT<T>& mat) {
+  for (int i = 0; i < mat.Rows(); ++i) {
+    for (int j = 0; j < mat.Cols(); ++j) {
+      mat.Row(i)[j] = hwy::Unpredictable1() * 0.01f * (i + j + 1);
+    }
+  }
+}
+
+template <typename T>
+void PrintMatPtr(MatPtrT<T> mat) {
+  for (int i = 0; i < mat.Rows(); ++i) {
+    for (int j = 0; j < mat.Cols(); ++j) {
+      std::cerr << mat.Row(i)[j] << " ,";
+    }
+    std::cerr << std::endl;
+  }
+};
+
 }  // namespace gcpp
 
 #endif  // THIRD_PARTY_GEMMA_CPP_UTIL_TEST_UTIL_H_
diff --git a/util/threading.h b/util/threading.h
index dcdcf24..3fb0227 100644
--- a/util/threading.h
+++ b/util/threading.h
@@ -187,7 +187,9 @@ class NestedPools {
 // functions below.
 class IndexRangePartition {
  public:
-  IndexRangePartition() = default;  // for MMPartitions
+  explicit IndexRangePartition(size_t single_task)
+      : range_(0, single_task), task_size_(single_task), num_tasks_(1) {}
+
   IndexRangePartition(const IndexRange& range, const size_t task_size)
       : range_(range), task_size_(static_cast<uint32_t>(task_size)) {
     const uint32_t num = static_cast<uint32_t>(range.Num());
@@ -262,43 +264,6 @@ static inline IndexRangePartition StaticPartition(const IndexRange& range,
   return IndexRangePartition(range, size);
 }
 
-// Parallel-for over a single range. This takes care of translating the task
-// index to a range.
-template <class Func>
-void ParallelizeOneRange(const IndexRangePartition& get1, hwy::ThreadPool& pool,
-                         hwy::pool::Caller caller, const Func& func) {
-  const size_t num_tasks = get1.NumTasks();
-  pool.Run(0, num_tasks, caller, [&](uint64_t task, size_t thread) {
-    const IndexRange range1 = get1.Range(task);
-    func(range1, thread);
-  });
-}
-
-// Parallel-for over the Cartesian product of the two sets of ranges. This
-// combines their indices into a single 'task' so they can be executed by one
-// `pool.Run`, which increases the amount of work available to workers and
-// reduces fork-join overhead vs. nested parallel-for loops. Calls `func` with
-// the two ranges and the thread index within `pool`.
-template <class Func>
-void ParallelizeTwoRanges(const IndexRangePartition& get1,
-                          const IndexRangePartition& get2,
-                          hwy::ThreadPool& pool, hwy::pool::Caller caller,
-                          const Func& func) {
-  const hwy::Divisor div1(static_cast<uint32_t>(get1.NumTasks()));
-
-  const size_t num_tasks = get1.NumTasks() * get2.NumTasks();
-  pool.Run(0, num_tasks, caller, [&](uint64_t task, size_t thread) {
-    HWY_DASSERT(task < (uint64_t{1} << 32));
-    const size_t idx2 = div1.Divide(static_cast<uint32_t>(task));
-    const size_t idx1 = div1.Remainder(static_cast<uint32_t>(task));
-    HWY_DASSERT(idx1 < get1.NumTasks());
-    HWY_DASSERT(idx2 < get2.NumTasks());
-    const IndexRange range1 = get1.Range(idx1);
-    const IndexRange range2 = get2.Range(idx2);
-    func(range1, range2, thread);
-  });
-}
-
 }  // namespace gcpp
 
 #endif  // THIRD_PARTY_GEMMA_CPP_UTIL_THREADING_H_
diff --git a/util/threading_context.cc b/util/threading_context.cc
index e725ce3..4a3b927 100644
--- a/util/threading_context.cc
+++ b/util/threading_context.cc
@@ -43,12 +43,9 @@ static void TunePool(hwy::PoolWaitMode wait_mode, hwy::ThreadPool& pool) {
   const size_t num_tasks[4] = {HWY_MAX(1, num_workers / 2), num_workers * 1,
                                num_workers * 5, num_workers * 20};
 
-  // Count tasks executed to ensure workers aren't optimized out. One per
-  // cache line to avoid false sharing.
-  const size_t kSizePerLine = HWY_ALIGNMENT / sizeof(size_t);
-
-  std::vector<size_t> counters(num_workers * kSizePerLine);
-  size_t prev_total = 0;  // avoids having to reset counters.
+  // Count tasks executed to ensure workers aren't optimized out.
+  std::vector<uint64_t> counters(num_workers * kU64PerLine);
+  uint64_t prev_total = 0;  // avoids having to reset counters.
 
   hwy::RandomState rng;
   for (size_t rep = 0; rep < 500; ++rep) {
@@ -63,13 +60,13 @@ static void TunePool(hwy::PoolWaitMode wait_mode, hwy::ThreadPool& pool) {
     pool.Run(begin, end, [&](uint64_t task, size_t thread) {
       HWY_ASSERT(begin <= task && task < end);
       HWY_ASSERT(thread < num_workers);
-      counters[thread * kSizePerLine]++;
+      counters[thread * kU64PerLine]++;
     });
 
     // Reduce count and ensure it matches the expected number of tasks.
-    size_t total = 0;
+    uint64_t total = 0;
     for (size_t i = 0; i < num_workers; ++i) {
-      total += counters[i * kSizePerLine];
+      total += counters[i * kU64PerLine];
     }
     const size_t expected = end - begin;
     HWY_ASSERT(total == prev_total + expected);
@@ -100,7 +97,8 @@ ThreadingContext::ThreadingContext(const ThreadingArgs& args)
                BoundedSlice(args.skip_lps, args.max_lps)),
       cache_info(topology),
       allocator(topology, cache_info, args.bind != Tristate::kFalse),
-      pools(topology, allocator, args.max_threads, args.pin) {
+      pools(topology, allocator, args.max_threads, args.pin),
+      tensor_output(args.tensor_output) {
   PROFILER_ZONE("Startup.ThreadingContext autotune");
   TunePools(hwy::PoolWaitMode::kSpin, *this);
   // kBlock is the default, hence set/tune it last.
diff --git a/util/threading_context.h b/util/threading_context.h
index 251888f..7e595ba 100644
--- a/util/threading_context.h
+++ b/util/threading_context.h
@@ -23,6 +23,7 @@
 #include <stdint.h>
 
 // IWYU pragma: begin_exports
+#include "io/io.h"  // Path
 #include "util/allocator.h"
 #include "util/args.h"
 #include "util/basics.h"  // Tristate
@@ -37,7 +38,9 @@ namespace gcpp {
 // Optional arguments for `ThreadingContext` from the command line.
 class ThreadingArgs : public ArgsBase<ThreadingArgs> {
  public:
-  ThreadingArgs(int argc, char* argv[]) { InitAndParse(argc, argv); }
+  ThreadingArgs(int argc, char* argv[], ConsumedArgs& consumed) {
+    InitAndParse(argc, argv, consumed);
+  }
   ThreadingArgs() { Init(); };
 
   // For BoundedTopology:
@@ -55,6 +58,8 @@ class ThreadingArgs : public ArgsBase<ThreadingArgs> {
   Tristate pin;        // pin threads?
   Tristate spin;       // use spin waits?
 
+  Path tensor_output;  // empty, or directory for tensor output
+
   template <class Visitor>
   void ForEach(const Visitor& visitor) {
     // These can be used to partition CPU packages/sockets and their
@@ -85,6 +90,9 @@ class ThreadingArgs : public ArgsBase<ThreadingArgs> {
 
     visitor(bind, "bind", Tristate::kDefault,
             "Bind memory to sockets? -1 = auto, 0 = no, 1 = yes.", 2);
+
+    visitor(tensor_output, "tensor_output", Path(),
+            "Empty, or directory for tensor output.", 2);
   }
 };
 
@@ -100,7 +108,7 @@ struct ThreadingContext {
 
   // Returns a worker index compatible with those from `ParallelFor`, assuming
   // the current thread is running on one thread per cluster, which happens
-  // when `ParallelismStrategy` is `kAcrossClusters`.
+  // when `Parallelism` is `kAcrossClusters`.
   size_t Worker(size_t cluster_idx) const {
     return cluster_idx * pools.MaxWorkersPerCluster();
   }
@@ -124,13 +132,15 @@ struct ThreadingContext {
 
   // Per-package/cluster/within cluster pools of threads, matching `topology`.
   NestedPools pools;
+
+  Path tensor_output;  // used by `TensorStats::Notify`.
 };
 
 #define GCPP_ZONE(ctx, global_idx, zone_enum) \
   PROFILER_ZONE3(ctx.profiler, global_idx, ctx.profiler_zones.Get(zone_enum))
 
 // Describes the strategy for distributing parallel work across cores.
-enum class ParallelismStrategy : uint8_t {
+enum class Parallelism : uint8_t {
   // Execute using a single-threaded loop on the calling thread. The `worker`
   // index passed to the user's `Func` is unique across clusters.
   kNone,
@@ -154,56 +164,110 @@ enum class ParallelismStrategy : uint8_t {
   kHierarchical,
 };
 
-// Calls `func(task, worker)` for each task in `[0, num_tasks)`. Parallelizes
-// over clusters of ONE package, then within each cluster.
+// Helper functions used to implement `ParallelFor`, also reused in multiple
+// places. User code should call `ParallelFor` instead, which accepts the more
+// convenient `Callers` enum.
+//
+// These call `func(task, worker)` for each task in `[0, num_tasks)`.
+
+// NOTE: the worker argument is actually the `cluster_idx`, so that `Func` can
+// pass that to `ParallelForWithinCluster`.
+template <class Func>
+void ParallelForAcrossClusters(size_t num_tasks, ThreadingContext& ctx,
+                               hwy::pool::Caller caller, const Func& func) {
+  ctx.pools.AllClusters().Run(
+      0, num_tasks, caller,
+      [&](uint64_t task, size_t cluster_idx) { func(task, cluster_idx); });
+}
+
+template <class Func>
+void ParallelForWithinCluster(size_t num_tasks, ThreadingContext& ctx,
+                              size_t cluster_idx, hwy::pool::Caller caller,
+                              const Func& func) {
+  const size_t cluster_base = ctx.Worker(cluster_idx);
+  ctx.pools.Cluster(cluster_idx)
+      .Run(0, num_tasks, caller, [&](uint64_t task, size_t worker) {
+        func(task, cluster_base + worker);
+      });
+}
+
+// Calls `func(range, cluster_idx)`, for passing to `*WithinCluster`.
+template <class Func>
+void ParallelPartitionAcrossClusters(const IndexRange range,
+                                     size_t task_multiple, size_t inner_tasks,
+                                     ThreadingContext& ctx,
+                                     hwy::pool::Caller caller,
+                                     const Func& func) {
+  HWY_DASSERT(1 <= inner_tasks && inner_tasks <= 4);
+  const IndexRangePartition ranges = StaticPartition(
+      range, ctx.pools.NumClusters() * inner_tasks, task_multiple);
+  ParallelForAcrossClusters(ranges.NumTasks(), ctx, caller,
+                            [&](uint64_t task, size_t cluster_idx) {
+                              func(ranges.Range(task), cluster_idx);
+                            });
+}
+
+// Calls `func(range, worker)`.
+template <class Func>
+void ParallelPartitionWithinCluster(const IndexRange range,
+                                    size_t task_multiple, size_t inner_tasks,
+                                    ThreadingContext& ctx, size_t cluster_idx,
+                                    hwy::pool::Caller caller,
+                                    const Func& func) {
+  HWY_DASSERT(1 <= inner_tasks && inner_tasks <= 4);
+  const size_t num_workers = ctx.pools.Cluster(cluster_idx).NumWorkers();
+  const IndexRangePartition ranges =
+      StaticPartition(range, num_workers * inner_tasks, task_multiple);
+  ParallelForWithinCluster(
+      ranges.NumTasks(), ctx, cluster_idx, caller,
+      [&](uint64_t task, size_t worker) { func(ranges.Range(task), worker); });
+}
+
+// Parallelizes across clusters, then within each cluster.
 template <class Func>
 void HierarchicalParallelFor(size_t num_tasks, ThreadingContext& ctx,
                              Callers callers, const Func& func) {
   const hwy::pool::Caller caller = ctx.pool_callers.Get(callers);
-  // If few tasks, run on a single cluster. Also avoids a bit of overhead if
-  // there is only one cluster.
-  hwy::ThreadPool& all_clusters = ctx.pools.AllClusters();
-  const size_t num_clusters = all_clusters.NumWorkers();
-  hwy::ThreadPool& cluster = ctx.pools.Cluster(0);
-  if (num_clusters == 1 || num_tasks <= cluster.NumWorkers()) {
-    return cluster.Run(0, num_tasks, caller, [&](uint64_t task, size_t thread) {
-      func(task, thread);
-    });
+
+  // If at most one task per cluster worker, run on a single cluster to avoid
+  // the expensive cross-cluster barrier.
+  {
+    const size_t cluster_idx = 0;
+    const size_t cluster_workers = ctx.pools.Cluster(cluster_idx).NumWorkers();
+    if (HWY_UNLIKELY(num_tasks <= cluster_workers)) {
+      return ParallelForWithinCluster(num_tasks, ctx, cluster_idx, caller,
+                                      func);
+    }
   }
 
-  // Assign each cluster a sub-range.
-  const IndexRangePartition ranges =
-      StaticPartition(IndexRange(0, num_tasks), num_clusters, 1);
-  ParallelizeOneRange(ranges, all_clusters, caller,
-                      [&](const IndexRange& range, const size_t cluster_idx) {
-                        hwy::ThreadPool& cluster =
-                            ctx.pools.Cluster(cluster_idx);
-                        const size_t cluster_base =
-                            cluster_idx * ctx.pools.MaxWorkersPerCluster();
-                        cluster.Run(range.begin(), range.end(), caller,
-                                    [&](uint64_t task, size_t thread) {
-                                      func(task, cluster_base + thread);
-                                    });
-                      });
+  ParallelPartitionAcrossClusters(
+      IndexRange(0, num_tasks), /*task_multiple=*/1, /*inner_tasks=*/1, ctx,
+      caller, [&](const IndexRange& cluster_range, size_t cluster_idx) {
+        ParallelForWithinCluster(cluster_range.Num(), ctx, cluster_idx, caller,
+                                 [&](uint64_t i, size_t worker) {
+                                   func(cluster_range.begin() + i, worker);
+                                 });
+      });
 }
 
 // Calls `func(task, worker)` for each `task` in `[0, num_tasks)`, with the
-// number/type of workers determined by `parallelism`. `cluster_idx` is for
-// `parallelism == kWithinCluster`, and should be 0 if unknown.
+// number/type of workers determined by `parallelism`. NOTE: worker is actually
+// `cluster_idx` for `kAcrossClusters`. The `cluster_idx` argument is for
+// `parallelism == {kWithinCluster, kNone}`, and should be 0 if unknown.
 template <class Func>
-void ParallelFor(ParallelismStrategy parallelism, size_t num_tasks,
+void ParallelFor(Parallelism parallelism, size_t num_tasks,
                  ThreadingContext& ctx, size_t cluster_idx, Callers callers,
                  const Func& func) {
   HWY_DASSERT(cluster_idx < ctx.topology.NumClusters());
   if (cluster_idx != 0) {
     // If already running across clusters, only use within-cluster modes.
-    HWY_DASSERT(parallelism == ParallelismStrategy::kNone ||
-                parallelism == ParallelismStrategy::kWithinCluster);
+    HWY_DASSERT(parallelism == Parallelism::kNone ||
+                parallelism == Parallelism::kWithinCluster);
   }
   const hwy::pool::Caller caller = ctx.pool_callers.Get(callers);
 
   switch (parallelism) {
-    case ParallelismStrategy::kNone: {
+    case Parallelism::kNone: {
       const size_t worker = ctx.Worker(cluster_idx);
       for (size_t task = 0; task < num_tasks; ++task) {
         func(task, worker);
@@ -211,40 +275,28 @@ void ParallelFor(ParallelismStrategy parallelism, size_t num_tasks,
       return;
     }
 
-    case ParallelismStrategy::kAcrossClusters:
-      return ctx.pools.AllClusters().Run(
-          0, num_tasks, caller,
+    case Parallelism::kAcrossClusters:
+      return ParallelForAcrossClusters(
+          num_tasks, ctx, caller,
           [&](uint64_t task, size_t cluster_idx) { func(task, cluster_idx); });
 
-    case ParallelismStrategy::kWithinCluster: {
-      // Ensure the worker argument is unique across clusters, because it is
-      // used for TLS indexing for example in profiler.h.
-      const size_t base = ctx.Worker(cluster_idx);
-      return ctx.pools.Cluster(cluster_idx)
-          .Run(0, num_tasks, caller, [&](uint64_t task, size_t worker) {
-            func(task, base + worker);
-          });
-    }
+    case Parallelism::kWithinCluster:
+      return ParallelForWithinCluster(num_tasks, ctx, cluster_idx, caller,
+                                      func);
 
-    case ParallelismStrategy::kFlat: {
-      // Check for single cluster; if not, we must compute `cluster_base` for
-      // consistent and non-overlapping worker indices.
-      hwy::ThreadPool& all_clusters = ctx.pools.AllClusters();
-      const size_t num_clusters = all_clusters.NumWorkers();
-      if (num_clusters == 1) {
-        return ctx.pools.Cluster(cluster_idx)
-            .Run(0, num_tasks, caller,
-                 [&](uint64_t task, size_t worker) { func(task, worker); });
+    case Parallelism::kFlat:
+      // Choose a single pool: the only cluster, or across all clusters
+      // (slower synchronization, but more memory bandwidth)
+      if (HWY_UNLIKELY(ctx.pools.NumClusters() == 1)) {
+        return ParallelForWithinCluster(num_tasks, ctx, cluster_idx, caller,
+                                        func);
       }
+      return ParallelForAcrossClusters(num_tasks, ctx, caller,
+                                       [&](uint64_t task, size_t cluster_idx) {
+                                         func(task, ctx.Worker(cluster_idx));
+                                       });
 
-      return all_clusters.Run(0, num_tasks, caller,
-                              [&](uint64_t task, size_t cluster_idx) {
-                                const size_t worker = ctx.Worker(cluster_idx);
-                                func(task, worker);
-                              });
-    }
-
-    case ParallelismStrategy::kHierarchical:
+    case Parallelism::kHierarchical:
       return HierarchicalParallelFor(num_tasks, ctx, callers, func);
   }
 }
diff --git a/util/threading_test.cc b/util/threading_test.cc
index 14ea1a0..b5d1858 100644
--- a/util/threading_test.cc
+++ b/util/threading_test.cc
@@ -202,59 +202,7 @@ TEST(ThreadingTest, TestStaticPartition) {
   }
 }
 
-TEST(ThreadingTest, TestParallelizeOneRange) {
-  const IndexRange range(0, 10);
-  const IndexRangePartition partition = StaticPartition(range, 2, 4);
-  hwy::ThreadPool null_pool(0);
-  size_t calls = 0;
-  ParallelizeOneRange(partition, null_pool, kCaller,
-                      [&](const IndexRange& range, size_t) {
-                        if (++calls == 1) {
-                          HWY_ASSERT(range.begin() == 0 && range.end() == 8);
-                        } else {
-                          HWY_ASSERT(range.begin() == 8 && range.end() == 10);
-                        }
-                      });
-  HWY_ASSERT(calls == 2);
-}
-
-TEST(ThreadingTest, TestParallelizeTwoRanges) {
-  const IndexRangePartition partition1 =
-      StaticPartition(IndexRange(0, 10), 2, 4);
-  const IndexRangePartition partition2 =
-      MaxSizePartition(IndexRange(128, 256), 32, 32);
-  HWY_ASSERT(partition2.NumTasks() == 4);
-  hwy::ThreadPool null_pool(0);
-  {
-    size_t calls = 0;
-    ParallelizeTwoRanges(
-        partition1, partition2, null_pool, kCaller,
-        [&](const IndexRange& range1, const IndexRange& range2, size_t) {
-          ++calls;
-          HWY_ASSERT(range1.begin() == 0 || range1.begin() == 8);
-          HWY_ASSERT(range2.begin() % 32 == 0);
-          HWY_ASSERT(range2.Num() % 32 == 0);
-        });
-    HWY_ASSERT(calls == 2 * 4);
-  }
-
-  // Also swap order to test Remainder() logic.
-  {
-    size_t calls = 0;
-    ParallelizeTwoRanges(
-        partition2, partition1, null_pool, kCaller,
-        [&](const IndexRange& range2, const IndexRange& range1, size_t) {
-          ++calls;
-          HWY_ASSERT(range1.begin() == 0 || range1.begin() == 8);
-          HWY_ASSERT(range2.begin() % 32 == 0);
-          HWY_ASSERT(range2.Num() % 32 == 0);
-        });
-    HWY_ASSERT(calls == 2 * 4);
-  }
-}
-
-static constexpr size_t kU64PerThread = HWY_ALIGNMENT / sizeof(size_t);
-static uint64_t outputs[hwy::kMaxLogicalProcessors * kU64PerThread];
+static uint64_t outputs[hwy::kMaxLogicalProcessors * kU64PerLine];
 
 std::vector<uint64_t> MeasureForkJoin(hwy::ThreadPool& pool) {
   // Governs duration of test; avoid timeout in debug builds.
@@ -268,7 +216,7 @@ std::vector<uint64_t> MeasureForkJoin(hwy::ThreadPool& pool) {
   const double t0 = hwy::platform::Now();
   for (size_t reps = 0; reps < 1200; ++reps) {
     pool.Run(0, pool.NumWorkers(), kCaller, [&](uint64_t task, size_t thread) {
-      outputs[thread * kU64PerThread] = base + thread;
+      outputs[thread * kU64PerLine] = base + thread;
     });
     hwy::PreventElision(outputs[base]);
     if (pool.AutoTuneComplete()) break;
@@ -309,7 +257,7 @@ std::vector<uint64_t> MeasureForkJoin(hwy::ThreadPool& pool) {
       const uint64_t t0 = hwy::timer::Start();
       pool.Run(0, pool.NumWorkers(), kCaller,
                [&](uint64_t task, size_t thread) {
-                 outputs[thread * kU64PerThread] = base + thread;
+                 outputs[thread * kU64PerLine] = base + thread;
                });
       const uint64_t t1 = hwy::timer::Stop();
       times.push_back(t1 - t0);
@@ -319,7 +267,7 @@ std::vector<uint64_t> MeasureForkJoin(hwy::ThreadPool& pool) {
       const uint64_t t0 = hwy::timer::Start();
       pool.Run(0, pool.NumWorkers(), kCaller,
                [&](uint64_t task, size_t thread) {
-                 outputs[thread * kU64PerThread] = base + thread;
+                 outputs[thread * kU64PerLine] = base + thread;
                });
       const uint64_t t1 = hwy::timer::Start();
       times.push_back(t1 - t0);
@@ -366,10 +314,10 @@ TEST(ThreadingTest, BenchJoin) {
 
     // Verify outputs to ensure the measured code is not a no-op.
     for (size_t lp = 0; lp < pool.NumWorkers(); ++lp) {
-      HWY_ASSERT(outputs[lp * kU64PerThread] >= 1);
-      HWY_ASSERT(outputs[lp * kU64PerThread] <= 1 + pool.NumWorkers());
-      for (size_t i = 1; i < kU64PerThread; ++i) {
-        HWY_ASSERT(outputs[lp * kU64PerThread + i] == 0);
+      HWY_ASSERT(outputs[lp * kU64PerLine] >= 1);
+      HWY_ASSERT(outputs[lp * kU64PerLine] <= 1 + pool.NumWorkers());
+      for (size_t i = 1; i < kU64PerLine; ++i) {
+        HWY_ASSERT(outputs[lp * kU64PerLine + i] == 0);
       }
     }
   };
diff --git a/util/topology.cc b/util/topology.cc
index f20b7f9..fae1dee 100644
--- a/util/topology.cc
+++ b/util/topology.cc
@@ -21,12 +21,14 @@
 #include <vector>
 
 #include "hwy/base.h"
+#include "hwy/bit_set.h"
 
 namespace gcpp {
 
 // Returns set of LPs available for use.
 static LPS EnabledLPs(const BoundedSlice& lp_slice) {
   LPS enabled_lps;
+  const size_t num_lps = hwy::TotalLogicalProcessors();
 
   // Thread-safe caching during the first call because subsequent pinning
   // overwrites the main thread's affinity.
@@ -35,6 +37,7 @@ static LPS EnabledLPs(const BoundedSlice& lp_slice) {
     if (!GetThreadAffinity(affinity)) affinity = LPS();
     return affinity;
   }();
+
   if (HWY_LIKELY(affinity.Any())) {
     // To honor taskset/numactl *and* the users's `lp_slice`, we interpret
     // the latter as a slice of the 1-bits of `enabled_lps`. Note that this
@@ -48,18 +51,32 @@ static LPS EnabledLPs(const BoundedSlice& lp_slice) {
       }
       ++enabled_idx;
     });
-  } else {
-    const size_t num_lps = hwy::TotalLogicalProcessors();
-    // Do not warn on Apple, where affinity is not supported.
-    if (!HWY_OS_APPLE) {
-      HWY_WARN("unknown OS affinity, max %zu LPs and slice %zu.", num_lps,
-               lp_slice.Num(num_lps));
+  }
+
+  if (HWY_UNLIKELY(!enabled_lps.Any())) {
+    // First warn: either about unknown affinity, or no overlap with `lp_slice`.
+    if (!affinity.Any()) {
+      // Do not warn on Apple, where affinity is not supported.
+      if (!HWY_OS_APPLE) {
+        HWY_WARN("unknown OS affinity, max %zu LPs and slice %zu.", num_lps,
+                 lp_slice.Num(num_lps));
+      }
+    } else {
+      HWY_WARN("LP slice [%zu, %zu) of initial affinity %zu is empty.",
+               lp_slice.Begin(), lp_slice.End(num_lps), affinity.Count());
     }
+
+    // Set `enabled_lps` based only on `lp_slice` and total logical processors.
     for (size_t lp = 0; lp < num_lps; ++lp) {
       if (lp_slice.Contains(num_lps, lp)) {
         enabled_lps.Set(lp);
       }
     }
+
+    if (!enabled_lps.Any()) {
+      HWY_WARN("no enabled LPs of total %zu, slice [%zu, %zu).", num_lps,
+               lp_slice.Begin(), lp_slice.End(affinity.Count()));
+    }
   }
 
   // Without threading support, only keep the first enabled LP; it might still
@@ -72,6 +89,7 @@ static LPS EnabledLPs(const BoundedSlice& lp_slice) {
     HWY_WARN("Warning, threads not supported, using only the main thread.");
   }
 
+  HWY_ASSERT(enabled_lps.Any());
   return enabled_lps;
 }
 
@@ -156,12 +174,13 @@ constexpr size_t kMaxLPsPerCluster = 6;
 
 #if !GEMMA_DISABLE_TOPOLOGY
 
-static size_t CoresFromLPs(const LPS& lps, const hwy::Topology& topology) {
-  LPS cores;
-  lps.Foreach([&](size_t lp) {
-    if (topology.lps[lp].smt == 0) cores.Set(lp);
-  });
-  return cores.Count();
+// Returns number of distinct SMT (hyperthreads).
+static size_t NumSMT(const hwy::Topology& topology) {
+  hwy::BitSet64 smt;
+  for (const hwy::Topology::LP& lp : topology.lps) {
+    smt.Set(lp.smt);
+  }
+  return smt.Count();
 }
 
 // tcluster is a modifiable copy of the first cluster in the package.
@@ -187,34 +206,66 @@ void BoundedTopology::SplitLargeCluster(const LPS& enabled_lps,
   }
 }
 
-// Main part of ctor, called when topology is known.
-bool BoundedTopology::InitFromTopology(const LPS& enabled_lps) {
-  const size_t tpkg_idx = package_slice_.Begin();
-  HWY_ASSERT(tpkg_idx < topology_.packages.size());
-  const hwy::Topology::Package& tpackage = topology_.packages[tpkg_idx];
-  const std::vector<hwy::Topology::Cluster>& tclusters = tpackage.clusters;
+using TClusters = std::vector<hwy::Topology::Cluster>;
+
+// Returns false if no cluster in `tclusters` has any enabled LPs.
+static bool AnyEnabledLPs(const TClusters& tclusters, const LPS& enabled_lps) {
   if (HWY_UNLIKELY(tclusters.empty())) {
-    HWY_WARN("Topology: no clusters found in package %zu.", tpkg_idx);
+    HWY_WARN("Topology: no clusters found.");
     return false;
   }
 
-  size_t max_tcluster_cores = 0;
-  size_t max_tcluster_lps = 0;
   for (const hwy::Topology::Cluster& tcluster : tclusters) {
-    const size_t cores = CoresFromLPs(tcluster.lps, topology_);
-    const size_t lps = tcluster.lps.Count();
-    max_tcluster_cores = HWY_MAX(max_tcluster_cores, cores);
-    max_tcluster_lps = HWY_MAX(max_tcluster_lps, lps);
+    bool any_lp_enabled = false;
+    tcluster.lps.Foreach(
+        [&](size_t lp) { any_lp_enabled |= (enabled_lps.Get(lp)); });
+    if (any_lp_enabled) return true;
   }
-  HWY_ASSERT(max_tcluster_cores != 0);
-  HWY_ASSERT(max_tcluster_lps >= max_tcluster_cores);
+
+  // No warning: this can happen if OS affinity limits us to the second package.
+  return false;
+}
+
+// Returns nullptr on failure. Also attempts `1 - tpkg_idx`, which is suitable
+// for the common case of up to two packages.
+static const TClusters* GetPackageClusters(const hwy::Topology& topology,
+                                           size_t tpkg_idx,
+                                           const LPS& enabled_lps) {
+  const size_t num_packages = topology.packages.size();
+  HWY_ASSERT(tpkg_idx < num_packages);
+  {
+    const TClusters& tclusters = topology.packages[tpkg_idx].clusters;
+    if (AnyEnabledLPs(tclusters, enabled_lps)) return &tclusters;
+  }
+
+  // Retry with the other package, if any.
+  tpkg_idx ^= 1;
+  if (tpkg_idx == num_packages) return nullptr;
+  {
+    const TClusters& tclusters = topology.packages[tpkg_idx].clusters;
+    if (AnyEnabledLPs(tclusters, enabled_lps)) return &tclusters;
+  }
+
+  HWY_WARN(
+      "Ignoring topology (%zu tpackages) because no clusters overlap with the "
+      "OS affinity (%zu enabled LPs): ",
+      num_packages, enabled_lps.Count());
+  enabled_lps.Foreach([](size_t lp) { fprintf(stderr, "%zu, ", lp); });
+  return nullptr;
+}
+
+// Main part of ctor, called when topology is known.
+bool BoundedTopology::InitFromTopology(const LPS& enabled_lps) {
+  const TClusters* maybe_tclusters =
+      GetPackageClusters(topology_, package_slice_.Begin(), enabled_lps);
+  if (!maybe_tclusters) return false;
+  const TClusters& tclusters = *maybe_tclusters;
 
   // Populate `clusters` with the subset of clusters in `cluster_slice` that
   // have any enabled LPs.
   clusters_.reserve(cluster_slice_.Num(tclusters.size()));
   cluster_slice_.Foreach("cluster", tclusters.size(), [&](size_t cluster_idx) {
-    const hwy::Topology::Cluster& tcluster = tpackage.clusters[cluster_idx];
-    Cluster cluster(enabled_lps, topology_.lps, tcluster);
+    Cluster cluster(enabled_lps, topology_.lps, tclusters[cluster_idx]);
 
     // Skip if empty, i.e. too few `enabled_lps`.
     if (HWY_LIKELY(cluster.NumWorkers() != 0)) {
@@ -223,14 +274,10 @@ bool BoundedTopology::InitFromTopology(const LPS& enabled_lps) {
       nodes_.Set(cluster.Node());
     }
   });
-  if (HWY_UNLIKELY(clusters_.empty())) {
-    HWY_WARN("Too restrictive cluster_slice or enabled_lps, no clusters left.");
-    return false;
-  }
 
   if (kSplitLargeClusters && clusters_.size() == 1 &&
       enabled_lps.Count() >= 16) {
-    SplitLargeCluster(enabled_lps, tpackage.clusters[0]);
+    SplitLargeCluster(enabled_lps, tclusters[0]);
   }
 
   // Sort by descending 'size' so that users who only use one get the largest.
@@ -239,20 +286,23 @@ bool BoundedTopology::InitFromTopology(const LPS& enabled_lps) {
               return a.NumWorkers() > b.NumWorkers();
             });
 
-  // Largest number of enabled workers in any cluster, for `topology_string_`.
-  // This may be less than `max_tcluster_cores` if `enabled_lps` excludes some.
-  size_t max_cluster_workers = 0;
-  for (const Cluster& c : clusters_) {
-    max_cluster_workers = HWY_MAX(max_cluster_workers, c.NumWorkers());
+  // Happens if all LPs are HTs (we checked that at least some LPs are enabled).
+  if (HWY_UNLIKELY(clusters_.empty())) {
+    HWY_WARN(
+        "Ignoring topology - no usable clusters. cluster_slice [%zu, %zu), "
+        "%zu tclusters, %zu tLPs, %zu enabled LPs: ",
+        cluster_slice_.Begin(), cluster_slice_.End(tclusters.size()),
+        tclusters.size(), topology_.lps.size(), enabled_lps.Count());
+    enabled_lps.Foreach([](size_t lp) { fprintf(stderr, "%zu, ", lp); });
+    return false;
   }
-  HWY_ASSERT(max_cluster_workers <= max_tcluster_cores);
-  // Do not warn about large clusters: GNR has 40.
 
+  const size_t num_smt = NumSMT(topology_);
   snprintf(topology_string_, sizeof(topology_string_),
            "%zuS %zuX %zuC %zuH, using %zuX %zuC (nodes=%zu)",
-           topology_.packages.size(), tclusters.size(), max_tcluster_cores,
-           max_tcluster_lps / max_tcluster_cores, NumClusters(),
-           max_cluster_workers, nodes_.Count());
+           topology_.packages.size(), tclusters.size(),
+           tclusters[0].lps.Count() / num_smt, num_smt, NumClusters(),
+           clusters_[0].NumWorkers(), nodes_.Count());
   return true;
 }
 
diff --git a/util/topology.h b/util/topology.h
index d4f80cc..b4a03fe 100644
--- a/util/topology.h
+++ b/util/topology.h
@@ -93,7 +93,7 @@ class BoundedTopology {
 
   class Cluster {
    public:
-    Cluster(const LPS& lps);
+    explicit Cluster(const LPS& lps);
     Cluster(const LPS& enabled_lps,
             const std::vector<hwy::Topology::LP>& all_lps,
             const hwy::Topology::Cluster& tcluster);
diff --git a/util/zones.cc b/util/zones.cc
index a474311..6480b96 100644
--- a/util/zones.cc
+++ b/util/zones.cc
@@ -51,6 +51,8 @@ const char* ZoneName(Zones zone) {
       return "Gen.SampleTop1";
     case Zones::kGenSampleTopK:
       return "Gen.SampleTopK";
+    case Zones::kGenStats:
+      return "Gen.Stats";
     case Zones::kMMDecompressA:
       return "MM.DecompressA";
     case Zones::kMMDispatch:
@@ -163,6 +165,8 @@ const char* CallerName(Callers caller) {
       return "ReadBatches";
     case Callers::kSampleAndStream:
       return "SampleAndStream";
+    case Callers::kTensorStats:
+      return "TensorStats";
     case Callers::kTest:  // only for unit tests.
       return "Test-only!";
     case Callers::kTunePool:
diff --git a/util/zones.h b/util/zones.h
index 5624e24..f324086 100644
--- a/util/zones.h
+++ b/util/zones.h
@@ -31,6 +31,7 @@ enum class Zones {  // Keep sorted
   kGenFFW,
   kGenSampleTop1,
   kGenSampleTopK,
+  kGenStats,
   kMMDecompressA,
   kMMDispatch,
   kMMMatMul,
@@ -96,6 +97,7 @@ enum class Callers {  // Keep sorted
   kReadAllToBF16,
   kReadBatches,
   kSampleAndStream,
+  kTensorStats,
   kTest,  // only for unit tests.
   kTunePool,
   kVitDotSoftmax1,