Use trailing slashes

src/fastmcp/server/http.py

@@ -310,28 +310,12 @@ def create_streamable_http_app(
                 # Re-raise other RuntimeErrors if they don't match the specific message
                 raise
 
-    # Create an ASGI app wrapper that normalizes paths and handles both /mcp and /mcp/
-    class PathNormalizingASGIApp:
-        def __init__(self, app):
-            self.app = app
-            
-        async def __call__(self, scope, receive, send):
-            # Normalize path to remove trailing slash for MCP SDK
-            if scope["type"] == "http":
-                path = scope["path"]
-                if path.endswith("/") and len(path) > 1:
-                    scope = dict(scope)
-                    scope["path"] = path.rstrip("/")
-            
-            await self.app(scope, receive, send)
-
-    # Create the path-normalizing wrapper
-    normalized_handler = PathNormalizingASGIApp(handle_streamable_http)
+    # Ensure the streamable_http_path ends with a trailing slash to avoid automatic redirects
+    # when mounting the application
+    if not streamable_http_path.endswith("/"):
+        streamable_http_path = streamable_http_path + "/"
 
-    # Create path pattern without trailing slash
-    path_pattern = streamable_http_path.rstrip("/")
-
-    # Add StreamableHTTP routes with or without auth - add both with and without trailing slash  
+    # Add StreamableHTTP routes with or without auth  
     if auth:
         auth_middleware, auth_routes, required_scopes = (
             setup_auth_middleware_and_routes(auth)
@@ -340,38 +324,19 @@ def create_streamable_http_app(
         server_routes.extend(auth_routes)
         server_middleware.extend(auth_middleware)
 
-        # Auth is enabled, wrap app with RequireAuthMiddleware
-        wrapped_app = RequireAuthMiddleware(normalized_handler, required_scopes)
-        
-        # Add routes for both with and without trailing slash
-        server_routes.append(
-            Route(
-                path_pattern,
-                endpoint=wrapped_app,
-                methods=["GET", "POST"]
-            )
-        )
+        # Auth is enabled, wrap endpoint with RequireAuthMiddleware
         server_routes.append(
-            Route(
-                path_pattern + "/",
-                endpoint=wrapped_app,
-                methods=["GET", "POST"]
+            Mount(
+                streamable_http_path,
+                app=RequireAuthMiddleware(handle_streamable_http, required_scopes),
             )
         )
     else:
-        # No auth required - add routes for both with and without trailing slash
-        server_routes.append(
-            Route(
-                path_pattern,
-                endpoint=normalized_handler,
-                methods=["GET", "POST"]
-            )
-        )
+        # No auth required
         server_routes.append(
-            Route(
-                path_pattern + "/",
-                endpoint=normalized_handler,
-                methods=["GET", "POST"]
+            Mount(
+                streamable_http_path,
+                app=handle_streamable_http,
             )
         )
 
@@ -400,6 +365,6 @@ def create_streamable_http_app(
     # Store the FastMCP server instance on the Starlette app state
     app.state.fastmcp_server = server
 
-    app.state.path = streamable_http_path.rstrip("/")
+    app.state.path = streamable_http_path
 
     return app

src/fastmcp/settings.py

@@ -192,9 +192,9 @@ class Settings(BaseSettings):
     # HTTP settings
     host: str = "127.0.0.1"
     port: int = 8000
-    sse_path: str = "/sse"
+    sse_path: str = "/sse/"
     message_path: str = "/messages/"
-    streamable_http_path: str = "/mcp"
+    streamable_http_path: str = "/mcp/"
     debug: bool = False
 
     # error handling