diff --git a/fastapi/routing.py b/fastapi/routing.py
index ea82ab14a..54687ce8b 100644
--- a/fastapi/routing.py
+++ b/fastapi/routing.py
@@ -232,16 +232,16 @@ class _DefaultLifespan:
         return self
 
 
-# Cache for endpoint context to avoid re-extracting on every request
-_endpoint_context_cache: dict[int, EndpointContext] = {}
+# Cache for endpoint context to avoid re-extracting on every request.
+# Keyed on the function object itself (not id()) so that entries remain valid
+# even if a function is garbage collected and its id is reused by a new object.
+_endpoint_context_cache: dict[Callable[..., Any], EndpointContext] = {}
 
 
 def _extract_endpoint_context(func: Any) -> EndpointContext:
     """Extract endpoint context with caching to avoid repeated file I/O."""
-    func_id = id(func)
-
-    if func_id in _endpoint_context_cache:
-        return _endpoint_context_cache[func_id]
+    if func in _endpoint_context_cache:
+        return _endpoint_context_cache[func]
 
     try:
         ctx: EndpointContext = {}
@@ -255,7 +255,7 @@ def _extract_endpoint_context(func: Any) -> EndpointContext:
     except Exception:
         ctx = EndpointContext()
 
-    _endpoint_context_cache[func_id] = ctx
+    _endpoint_context_cache[func] = ctx
     return ctx