From 05d1effc233cb04db7115f94a72115d1f0b2bc1a Mon Sep 17 00:00:00 2001
From: Charisn <ncharis97@gmail.com>
Date: Sun, 15 Feb 2026 13:03:09 +0200
Subject: [PATCH 1/2] Fix UnboundLocalError in OpenAPI schema generation with
 custom response classes

When a route uses a custom response class whose __init__ does not expose
a status_code parameter with an int default, and the route decorator
does not specify an explicit status_code, the status_code local variable
in get_openapi_path() was never assigned. This caused an
UnboundLocalError at the point where status_code is used to populate
the operation responses dict.

The bug does not surface with standard Starlette response classes
(JSONResponse, HTMLResponse, PlainTextResponse, StreamingResponse, etc.)
because they all declare status_code: int = 200 (or 307 for redirects)
in their __init__ signatures. It triggers when users define custom
response classes that wrap or omit the status_code parameter, e.g.:

    class CustomResponse(Response):
        def __init__(self, content, **kwargs):
            super().__init__(content=content, status_code=200, **kwargs)

    @app.get("/items", response_class=CustomResponse)
    async def get_items(): ...

Accessing /openapi.json or /docs would crash with:
    UnboundLocalError: cannot access local variable 'status_code'

Fix: initialize status_code = "200" before the conditional block so it
always has a safe default. The existing branches that extract status_code
from the route or from the response class signature still override this
default when applicable.
---
 fastapi/openapi/utils.py                      |  1 +
 ...pi_custom_response_class_no_status_code.py | 61 +++++++++++++++++++
 2 files changed, 62 insertions(+)
 create mode 100644 tests/test_openapi_custom_response_class_no_status_code.py

diff --git a/fastapi/openapi/utils.py b/fastapi/openapi/utils.py
index 812003aee..910eca72f 100644
--- a/fastapi/openapi/utils.py
+++ b/fastapi/openapi/utils.py
@@ -339,6 +339,7 @@ def get_openapi_path(
                         )
                         callbacks[callback.name] = {callback.path: cb_path}
                 operation["callbacks"] = callbacks
+            status_code = "200"
             if route.status_code is not None:
                 status_code = str(route.status_code)
             else:
diff --git a/tests/test_openapi_custom_response_class_no_status_code.py b/tests/test_openapi_custom_response_class_no_status_code.py
new file mode 100644
index 000000000..18294f181
--- /dev/null
+++ b/tests/test_openapi_custom_response_class_no_status_code.py
@@ -0,0 +1,61 @@
+from starlette.responses import Response
+
+from fastapi import FastAPI
+from fastapi.testclient import TestClient
+from inline_snapshot import snapshot
+
+
+class CustomResponse(Response):
+    """A custom response class whose __init__ does not expose status_code
+    as a parameter with an int default. This previously caused an
+    UnboundLocalError during OpenAPI schema generation when the route
+    did not specify an explicit status_code."""
+
+    media_type = "text/plain"
+
+    def __init__(self, content: str, **kwargs: object) -> None:
+        super().__init__(content=content, status_code=200, **kwargs)
+
+
+app = FastAPI()
+
+
+@app.get("/items", response_class=CustomResponse)
+async def get_items():
+    return "ok"
+
+
+client = TestClient(app)
+
+
+def test_get_response():
+    response = client.get("/items")
+    assert response.status_code == 200
+    assert response.text == "ok"
+
+
+def test_openapi_schema():
+    """OpenAPI generation must not crash when the response class's __init__
+    lacks a status_code parameter with an int default."""
+    response = client.get("/openapi.json")
+    assert response.status_code == 200, response.text
+    assert response.json() == snapshot(
+        {
+            "openapi": "3.1.0",
+            "info": {"title": "FastAPI", "version": "0.1.0"},
+            "paths": {
+                "/items": {
+                    "get": {
+                        "summary": "Get Items",
+                        "operationId": "get_items_items_get",
+                        "responses": {
+                            "200": {
+                                "description": "Successful Response",
+                                "content": {"text/plain": {"schema": {"type": "string"}}},
+                            }
+                        },
+                    }
+                }
+            },
+        }
+    )

From 68a08572c1f814d5dea07a677f519ae6cafed8b6 Mon Sep 17 00:00:00 2001
From: "pre-commit-ci-lite[bot]"
 <117423508+pre-commit-ci-lite[bot]@users.noreply.github.com>
Date: Sun, 15 Feb 2026 11:12:42 +0000
Subject: [PATCH 2/2] =?UTF-8?q?=F0=9F=8E=A8=20Auto=20format?=
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

---
 tests/test_openapi_custom_response_class_no_status_code.py | 7 ++++---
 1 file changed, 4 insertions(+), 3 deletions(-)

diff --git a/tests/test_openapi_custom_response_class_no_status_code.py b/tests/test_openapi_custom_response_class_no_status_code.py
index 18294f181..7ec1d7115 100644
--- a/tests/test_openapi_custom_response_class_no_status_code.py
+++ b/tests/test_openapi_custom_response_class_no_status_code.py
@@ -1,8 +1,7 @@
-from starlette.responses import Response
-
 from fastapi import FastAPI
 from fastapi.testclient import TestClient
 from inline_snapshot import snapshot
+from starlette.responses import Response
 
 
 class CustomResponse(Response):
@@ -51,7 +50,9 @@ def test_openapi_schema():
                         "responses": {
                             "200": {
                                 "description": "Successful Response",
-                                "content": {"text/plain": {"schema": {"type": "string"}}},
+                                "content": {
+                                    "text/plain": {"schema": {"type": "string"}}
+                                },
                             }
                         },
                     }