Merge pull request #489 from jlowin/codex/view-issue-487

Store FastMCP instance on app.state.fastmcp_server

docs/deployment/asgi.mdx

@@ -45,6 +45,9 @@ sse_app = mcp.http_app(transport="sse")
 
 Both approaches return a Starlette application that can be integrated with other ASGI-compatible web frameworks.
 
+The returned app stores the `FastMCP` instance on `app.state.fastmcp_server`, so you
+can access it from custom middleware or routes via `request.app.state.fastmcp_server`.
+
 The MCP server's endpoint is mounted at the root path `/mcp` for Streamable HTTP transport, and `/sse` for SSE transport, though you can change these paths by passing a `path` argument to the `http_app()` method:
 
 ```python

src/fastmcp/server/http.py

@@ -247,11 +247,15 @@ def create_sse_app(
         server_middleware.extend(middleware)
 
     # Create and return the app
-    return create_base_app(
+    app = create_base_app(
         routes=server_routes,
         middleware=server_middleware,
         debug=debug,
     )
+    # Store the FastMCP server instance on the Starlette app state
+    app.state.fastmcp_server = server
+
+    return app
 
 
 def create_streamable_http_app(
@@ -344,9 +348,13 @@ def create_streamable_http_app(
             yield
 
     # Create and return the app with lifespan
-    return create_base_app(
+    app = create_base_app(
         routes=server_routes,
         middleware=server_middleware,
         debug=debug,
         lifespan=lifespan,
     )
+    # Store the FastMCP server instance on the Starlette app state
+    app.state.fastmcp_server = server
+
+    return app

tests/server/test_app_state.py

@@ -0,0 +1,26 @@
+from fastmcp.server import FastMCP
+from fastmcp.server.http import create_sse_app, create_streamable_http_app
+
+
+def test_http_app_sets_mcp_server_state():
+    server = FastMCP(name="StateTest")
+    app = server.http_app()
+    assert app.state.fastmcp_server is server
+
+
+def test_http_app_sse_sets_mcp_server_state():
+    server = FastMCP(name="StateTest")
+    app = server.http_app(transport="sse")
+    assert app.state.fastmcp_server is server
+
+
+def test_create_streamable_http_app_sets_state():
+    server = FastMCP(name="StateTest")
+    app = create_streamable_http_app(server, "/mcp")
+    assert app.state.fastmcp_server is server
+
+
+def test_create_sse_app_sets_state():
+    server = FastMCP(name="StateTest")
+    app = create_sse_app(server, message_path="/message", sse_path="/sse")
+    assert app.state.fastmcp_server is server