From 89a99b100fd378647902d69057780c258d8f4cac Mon Sep 17 00:00:00 2001
From: onthebed <1136664562@qq.com>
Date: Tue, 28 Apr 2026 22:32:28 +0800
Subject: [PATCH 1/2] fix(routing): preserve stream metadata in include_router

---
 fastapi/routing.py |  9 +++++++++
 tests/test_sse.py  | 17 ++++++++++++++---
 2 files changed, 23 insertions(+), 3 deletions(-)

diff --git a/fastapi/routing.py b/fastapi/routing.py
index 36acb6b89d..41c3c8aea5 100644
--- a/fastapi/routing.py
+++ b/fastapi/routing.py
@@ -1794,6 +1794,15 @@ class APIRouter(routing.Router):
                         self.strict_content_type,
                     ),
                 )
+                new_route = self.routes[-1]
+                if isinstance(new_route, APIRoute) and route.stream_item_type is not None:
+                    new_route.stream_item_type = route.stream_item_type
+                    new_route.stream_item_field = create_model_field(
+                        name=f"StreamItem_{new_route.unique_id}",
+                        type_=new_route.stream_item_type,
+                        mode="serialization",
+                    )
+                    new_route.app = request_response(new_route.get_route_handler())
             elif isinstance(route, routing.Route):
                 methods = list(route.methods or [])
                 self.add_route(
diff --git a/tests/test_sse.py b/tests/test_sse.py
index 6dfec61838..0772376afc 100644
--- a/tests/test_sse.py
+++ b/tests/test_sse.py
@@ -91,9 +91,9 @@ router = APIRouter()
 
 
 @router.get("/events", response_class=EventSourceResponse)
-async def stream_events():
-    yield {"msg": "hello"}
-    yield {"msg": "world"}
+async def stream_events() -> AsyncIterable[Item]:
+    yield items[0]
+    yield items[1]
 
 
 app.include_router(router, prefix="/api")
@@ -256,6 +256,17 @@ def test_data_and_raw_data_mutually_exclusive():
 
 
 def test_sse_on_router_included_in_app(client: TestClient):
+    route = next(r for r in app.routes if getattr(r, "path", None) == "/api/events")
+    assert route.stream_item_type is Item
+    assert route.stream_item_field is not None
+
+    openapi = app.openapi()
+    item_schema = openapi["paths"]["/api/events"]["get"]["responses"]["200"][
+        "content"
+    ]["text/event-stream"]["itemSchema"]
+    assert "contentSchema" in item_schema["properties"]["data"]
+    assert "Item" in openapi["components"]["schemas"]
+
     response = client.get("/api/events")
     assert response.status_code == 200
     assert response.headers["content-type"] == "text/event-stream; charset=utf-8"

From 41f5f96768d9efdf978e917a2d9b06ea98a9e987 Mon Sep 17 00:00:00 2001
From: "pre-commit-ci-lite[bot]"
 <117423508+pre-commit-ci-lite[bot]@users.noreply.github.com>
Date: Tue, 28 Apr 2026 14:42:42 +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

---
 fastapi/routing.py | 5 ++++-
 tests/test_sse.py  | 6 +++---
 2 files changed, 7 insertions(+), 4 deletions(-)

diff --git a/fastapi/routing.py b/fastapi/routing.py
index 41c3c8aea5..346d96f6ab 100644
--- a/fastapi/routing.py
+++ b/fastapi/routing.py
@@ -1795,7 +1795,10 @@ class APIRouter(routing.Router):
                     ),
                 )
                 new_route = self.routes[-1]
-                if isinstance(new_route, APIRoute) and route.stream_item_type is not None:
+                if (
+                    isinstance(new_route, APIRoute)
+                    and route.stream_item_type is not None
+                ):
                     new_route.stream_item_type = route.stream_item_type
                     new_route.stream_item_field = create_model_field(
                         name=f"StreamItem_{new_route.unique_id}",
diff --git a/tests/test_sse.py b/tests/test_sse.py
index 0772376afc..444b745c29 100644
--- a/tests/test_sse.py
+++ b/tests/test_sse.py
@@ -261,9 +261,9 @@ def test_sse_on_router_included_in_app(client: TestClient):
     assert route.stream_item_field is not None
 
     openapi = app.openapi()
-    item_schema = openapi["paths"]["/api/events"]["get"]["responses"]["200"][
-        "content"
-    ]["text/event-stream"]["itemSchema"]
+    item_schema = openapi["paths"]["/api/events"]["get"]["responses"]["200"]["content"][
+        "text/event-stream"
+    ]["itemSchema"]
     assert "contentSchema" in item_schema["properties"]["data"]
     assert "Item" in openapi["components"]["schemas"]