diff --git a/tools/server/server-models.cpp b/tools/server/server-models.cpp
index be3226ada3..95b2efdbf1 100644
--- a/tools/server/server-models.cpp
+++ b/tools/server/server-models.cpp
@@ -10,6 +10,8 @@
 #include <mutex>
 #include <condition_variable>
 #include <cstring>
+#include <atomic>
+#include <chrono>
 
 #ifdef _WIN32
 #include <winsock2.h>
@@ -60,7 +62,10 @@ static std::filesystem::path get_server_exec_path() {
 #else
     char path[FILENAME_MAX];
     ssize_t count = readlink("/proc/self/exe", path, FILENAME_MAX);
-    return std::filesystem::path(std::string(path, (count > 0) ? count: 0));
+    if (count <= 0) {
+        throw std::runtime_error("failed to resolve /proc/self/exe");
+    }
+    return std::filesystem::path(std::string(path, count));
 #endif
 }
 
@@ -203,22 +208,27 @@ std::vector<server_model_meta> server_models::get_all_meta() {
 }
 
 void server_models::load(const std::string & name) {
-    auto meta = get_meta(name);
-    if (!meta.has_value()) {
+    std::lock_guard<std::mutex> lk(mutex);
+    if (mapping.find(name) == mapping.end()) {
         throw std::runtime_error("model name=" + name + " is not found");
     }
 
-    std::lock_guard<std::mutex> lk(mutex);
-    if (meta->status != SERVER_MODEL_STATUS_FAILED && meta->status != SERVER_MODEL_STATUS_UNLOADED) {
+    auto meta = mapping[name].meta;
+    if (meta.status != SERVER_MODEL_STATUS_FAILED && meta.status != SERVER_MODEL_STATUS_UNLOADED) {
         SRV_INF("model %s is not ready\n", name.c_str());
         return;
     }
 
+    // prepare new instance info
     instance_t inst;
-    inst.meta        = meta.value();
+    inst.meta        = meta;
     inst.meta.port   = get_free_port();
     inst.meta.status = SERVER_MODEL_STATUS_LOADING;
 
+    if (inst.meta.port <= 0) {
+        throw std::runtime_error("failed to get a port number");
+    }
+
     inst.subproc = std::make_shared<subprocess_s>();
     {
         std::string exec_path = get_server_exec_path().string();
@@ -354,17 +364,25 @@ void server_models::wait_until_loaded(const std::string & name) {
     });
 }
 
-void server_models::ensure_model_loaded(const std::string & name) {
+bool server_models::ensure_model_loaded(const std::string & name) {
     auto meta = get_meta(name);
     if (!meta.has_value()) {
         throw std::runtime_error("model name=" + name + " is not found");
     }
     if (meta->is_active()) {
-        return; // already loaded
+        return false; // already loaded
     }
     SRV_INF("model name=%s is not loaded, loading...\n", name.c_str());
     load(name);
     wait_until_loaded(name);
+    {
+        // check final status
+        meta = get_meta(name);
+        if (!meta.has_value() || meta->status == SERVER_MODEL_STATUS_FAILED) {
+            throw std::runtime_error("model name=" + name + " failed to load");
+        }
+    }
+    return true;
 }
 
 server_http_res_ptr server_models::proxy_request(const server_http_req & req, const std::string & method, const std::string & name) {
@@ -372,7 +390,9 @@ server_http_res_ptr server_models::proxy_request(const server_http_req & req, co
     if (!meta.has_value()) {
         throw std::runtime_error("model name=" + name + " is not found");
     }
-    ensure_model_loaded(name); // TODO: handle failure case
+    if (ensure_model_loaded(name)) {
+        meta = get_meta(name); // refresh meta
+    }
     SRV_INF("proxying request to model %s on port %d\n", name.c_str(), meta->port);
     auto proxy = std::make_unique<server_http_proxy>(
             method,
@@ -439,11 +459,11 @@ struct pipe_t {
     std::atomic<bool> writer_closed{false};
     std::atomic<bool> reader_closed{false};
     void close_write() {
-        writer_closed.store(true);
+        writer_closed.store(true, std::memory_order_relaxed);
         cv.notify_all();
     }
     void close_read() {
-        reader_closed.store(true);
+        reader_closed.store(true, std::memory_order_relaxed);
         cv.notify_all();
     }
     bool read(T & output, const std::function<bool()> & should_stop) {
diff --git a/tools/server/server-models.h b/tools/server/server-models.h
index 3cd070f89a..f8ae757fa4 100644
--- a/tools/server/server-models.h
+++ b/tools/server/server-models.h
@@ -13,7 +13,7 @@
 
 /**
  * state diagram:
- * 
+ *
  * UNLOADED ──► LOADING ──► LOADED
  *                 ▲           │
  *                 │           │
@@ -105,7 +105,8 @@ public:
     void wait_until_loaded(const std::string & name);
 
     // load the model if not loaded, otherwise do nothing
-    void ensure_model_loaded(const std::string & name);
+    // return false if model is already loaded; return true otherwise (meta may need to be refreshed)
+    bool ensure_model_loaded(const std::string & name);
 
     // proxy an HTTP request to the model instance
     server_http_res_ptr proxy_request(const server_http_req & req, const std::string & method, const std::string & name);