From 1d8169a365595a3c113d398d3b2b435e40a8bef7 Mon Sep 17 00:00:00 2001
From: muhamedfazalps <muhamedfazalps@users.noreply.github.com>
Date: Sat, 20 Jun 2026 17:27:17 +0530
Subject: [PATCH] fix(fastapi): handle _IncludedRouter in FastAPI v0.137.0+

FastAPI v0.137.0 changed router.routes from a flat list to a tree
structure. Included routers are now wrapped in _IncludedRouter objects
that lack a path attribute, causing AttributeError in
_get_route_details().

This fix recurses into the sub-routes of _IncludedRouter (via
original_router.routes) to find the actual matching route and its path.
Also adds try/except for the PARTIAL match path which had the same
latent bug.

Fixes #4699

Assisted-by: Claude Opus 4.6
---
 .changelog/4699.fixed                         |  1 +
 .../instrumentation/fastapi/__init__.py       | 33 +++++++++++++++--
 .../tests/test_fastapi_instrumentation.py     | 35 +++++++++++++++++++
 3 files changed, 66 insertions(+), 3 deletions(-)
 create mode 100644 .changelog/4699.fixed

diff --git a/.changelog/4699.fixed b/.changelog/4699.fixed
new file mode 100644
index 0000000000..d23f900187
--- /dev/null
+++ b/.changelog/4699.fixed
@@ -0,0 +1 @@
+`opentelemetry-instrumentation-fastapi`: fix ``AttributeError`` for ``_IncludedRouter`` in FastAPI v0.137.0+
diff --git a/instrumentation/opentelemetry-instrumentation-fastapi/src/opentelemetry/instrumentation/fastapi/__init__.py b/instrumentation/opentelemetry-instrumentation-fastapi/src/opentelemetry/instrumentation/fastapi/__init__.py
index ab936f0ed5..a3e3212c45 100644
--- a/instrumentation/opentelemetry-instrumentation-fastapi/src/opentelemetry/instrumentation/fastapi/__init__.py
+++ b/instrumentation/opentelemetry-instrumentation-fastapi/src/opentelemetry/instrumentation/fastapi/__init__.py
@@ -488,11 +488,38 @@ def _get_route_details(scope):
             try:
                 route = starlette_route.path
             except AttributeError:
-                # routes added via host routing won't have a path attribute
-                route = scope.get("path")
+                # FastAPI v0.137.0+ wraps included routers in
+                # _IncludedRouter objects that lack a path attribute.
+                # Recurse into the sub-routes to find the actual route.
+                sub_routes = getattr(starlette_route, "routes", None)
+                if sub_routes is None and hasattr(
+                    starlette_route, "original_router"
+                ):
+                    sub_routes = getattr(
+                        starlette_route.original_router, "routes", []
+                    )
+                if sub_routes:
+                    for sub in sub_routes:
+                        sub_match, _ = (
+                            Route.matches(sub, scope)
+                            if isinstance(sub, Route)
+                            else sub.matches(scope)
+                        )
+                        if sub_match == Match.FULL:
+                            try:
+                                route = sub.path
+                            except AttributeError:
+                                route = scope.get("path")
+                            break
+                else:
+                    # routes added via host routing won't have a path attribute
+                    route = scope.get("path")
             break
         if match == Match.PARTIAL:
-            route = starlette_route.path
+            try:
+                route = starlette_route.path
+            except AttributeError:
+                route = scope.get("path")
     return route
 
 
diff --git a/instrumentation/opentelemetry-instrumentation-fastapi/tests/test_fastapi_instrumentation.py b/instrumentation/opentelemetry-instrumentation-fastapi/tests/test_fastapi_instrumentation.py
index 991aec902f..7d38e77248 100644
--- a/instrumentation/opentelemetry-instrumentation-fastapi/tests/test_fastapi_instrumentation.py
+++ b/instrumentation/opentelemetry-instrumentation-fastapi/tests/test_fastapi_instrumentation.py
@@ -358,6 +358,41 @@ def test_custom_api_router(self):
                 span.attributes[HTTP_URL],
             )
 
+    def test_included_router_route_attribute(self):
+        """Ensure that routes from included routers resolve the correct HTTP_ROUTE.
+
+        FastAPI v0.137.0+ wraps included routers in _IncludedRouter objects
+        that do not have a path attribute. The instrumentation must recurse
+        into the sub-routes to find the actual route path.
+        See: https://github.com/open-telemetry/opentelemetry-python-contrib/issues/4699
+        """
+        from fastapi import APIRouter
+
+        app = fastapi.FastAPI()
+        router = APIRouter(prefix="/items")
+
+        @router.get("/{item_id}")
+        async def get_item(item_id: int):
+            return {"item_id": item_id}
+
+        app.include_router(router)
+        otel_fastapi.FastAPIInstrumentor.instrument_app(app)
+
+        client = TestClient(app)
+        resp = client.get("/items/42")
+        self.assertEqual(resp.status_code, 200)
+
+        spans = self.memory_exporter.get_finished_spans()
+        server_spans = [
+            span
+            for span in spans
+            if HTTP_ROUTE in span.attributes
+        ]
+        self.assertTrue(len(server_spans) > 0)
+        self.assertEqual(
+            server_spans[-1].attributes[HTTP_ROUTE], "/items/{item_id}"
+        )
+
     def test_host_fastapi_call(self):
         client = TestClient(self._app, base_url="https://testserver2:443")
         client.get("/")