fix: use normalized path for sse message endpoint

src/mcp/server/fastmcp/server.py

@@ -742,7 +742,7 @@ async def handle_sse(scope: Scope, receive: Receive, send: Send):
             )
             routes.append(
                 Mount(
-                    self.settings.message_path,
+                    normalized_message_endpoint,
                     app=RequireAuthMiddleware(sse.handle_post_message, required_scopes),
                 )
             )
@@ -762,7 +762,7 @@ async def sse_endpoint(request: Request) -> Response:
             )
             routes.append(
                 Mount(
-                    self.settings.message_path,
+                    normalized_message_endpoint,
                     app=sse.handle_post_message,
                 )
             )

tests/server/fastmcp/test_server.py

@@ -99,7 +99,7 @@ async def test_starlette_routes_with_mount_path(self):
 
         # Verify path values
         assert sse_routes[0].path == "/sse", "SSE route path should be /sse"
-        assert mount_routes[0].path == "/messages", "Mount route path should be /messages"
+        assert mount_routes[0].path == "/api/messages", "Mount route path should be /api/messages"
 
         # Test with mount path as parameter
         mcp = FastMCP()
@@ -115,7 +115,7 @@ async def test_starlette_routes_with_mount_path(self):
 
         # Verify path values
         assert sse_routes[0].path == "/sse", "SSE route path should be /sse"
-        assert mount_routes[0].path == "/messages", "Mount route path should be /messages"
+        assert mount_routes[0].path == "/param/messages", "Mount route path should be /param/messages"
 
     @pytest.mark.anyio
     async def test_non_ascii_description(self):