Merge pull request #153 from taylorwilsdon/vscode_oauth_support

feat: Streamlined VSCode OAuth Support

README.md

@@ -51,6 +51,8 @@
 
 A production-ready MCP server that integrates all major Google Workspace services with AI assistants. It supports both single-user operation and multi-user authentication via OAuth 2.1, making it a powerful backend for custom applications. Built with FastMCP for optimal performance, featuring advanced authentication handling, service caching, and streamlined development patterns.
 
+**🎉 Simplified Setup**: Now uses Google Desktop OAuth clients - no redirect URIs or port configuration needed!
+
 ## Features
 
 - **🔐 Advanced OAuth 2.0 & OAuth 2.1**: Secure authentication with automatic token refresh, transport-aware callback handling, session management, centralized scope management, and OAuth 2.1 bearer token support for multi-user environments with innovative CORS proxy architecture
@@ -95,6 +97,8 @@ A production-ready MCP server that integrates all major Google Workspace service
 | `GOOGLE_PSE_API_KEY` *(optional)* | API key for Google Custom Search - see [Custom Search Setup](#google-custom-search-setup) |
 | `GOOGLE_PSE_ENGINE_ID` *(optional)* | Programmable Search Engine ID for Custom Search |
 | `MCP_ENABLE_OAUTH21` *(optional)* | Set to `true` to enable OAuth 2.1 support (requires streamable-http transport) |
+| `OAUTH_CUSTOM_REDIRECT_URIS` *(optional)* | Comma-separated list of additional redirect URIs |
+| `OAUTH_ALLOWED_ORIGINS` *(optional)* | Comma-separated list of additional CORS origins |
 | `OAUTHLIB_INSECURE_TRANSPORT=1` | Development only (allows `http://` redirect) |
 
 Claude Desktop stores these securely in the OS keychain; set them once in the extension pane.
@@ -114,12 +118,12 @@ Claude Desktop stores these securely in the OS keychain; set them once in the ex
 ### Configuration
 
 1. **Google Cloud Setup**:
-   - Create OAuth 2.0 credentials (web application) in [Google Cloud Console](https://console.cloud.google.com/)
+   - Create OAuth 2.0 credentials in [Google Cloud Console](https://console.cloud.google.com/)
    - Create a new project (or use an existing one) for your MCP server.
    - Navigate to APIs & Services → Credentials.
    - Click Create Credentials → OAuth Client ID.
-   - Choose Web Application as the application type.
+   - **Choose Desktop Application as the application type** (simpler setup, no redirect URIs needed!)
-   - Add redirect URI: `http://localhost:8000/oauth2callback`
+   - Download your credentials and note the Client ID and Client Secret
 
    - **Enable APIs**:
    - In the Google Cloud Console, go to APIs & Services → Library.
@@ -278,6 +282,29 @@ This architecture enables any OAuth 2.1 compliant client to authenticate users t
 
 </details>
 
+**MCP Inspector**: No additional configuration needed with desktop OAuth client.
+
+**Claude Code Inspector**: No additional configuration needed with desktop OAuth client.
+
+### VS Code MCP Client Support
+
+The server includes native support for VS Code's MCP client:
+
+- **No Configuration Required**: Works out-of-the-box with VS Code's MCP extension
+- **Standards Compliant**: Full OAuth 2.1 compliance with desktop OAuth clients
+
+**VS Code mcp.json Configuration Example**:
+```json
+{
+    "servers": {
+        "google-workspace": {
+            "url": "http://localhost:8000/mcp/",
+            "type": "http"
+        }
+    }
+}
+```
+
 ### Connect to Claude Desktop
 
 The server supports two transport modes:
@@ -422,17 +449,18 @@ If you need to use HTTP mode with Claude Desktop:
 
 ### First-Time Authentication
 
-The server features **transport-aware OAuth callback handling**:
+The server uses **Google Desktop OAuth** for simplified authentication:
 
-- **Stdio Mode**: Automatically starts a minimal HTTP server on port 8000 for OAuth callbacks
+- **No redirect URIs needed**: Desktop OAuth clients handle authentication without complex callback URLs
-- **HTTP Mode**: Uses the existing FastAPI server for OAuth callbacks
+- **Automatic flow**: The server manages the entire OAuth process transparently
-- **Same OAuth Flow**: Both modes use `http://localhost:8000/oauth2callback` for consistency
+- **Transport-agnostic**: Works seamlessly in both stdio and HTTP modes
 
 When calling a tool:
 1. Server returns authorization URL
 2. Open URL in browser and authorize
-3. Server handles OAuth callback automatically (on port 8000 in both modes)
+3. Google provides an authorization code
-4. Retry the original request
+4. Paste the code when prompted (or it's handled automatically)
+5. Server completes authentication and retries your request
 
 ---
 

auth/google_remote_auth_provider.py

@@ -24,6 +24,7 @@ from pydantic import AnyHttpUrl
 try:
     from fastmcp.server.auth import RemoteAuthProvider
     from fastmcp.server.auth.providers.jwt import JWTVerifier
+
     REMOTEAUTHPROVIDER_AVAILABLE = True
 except ImportError:
     REMOTEAUTHPROVIDER_AVAILABLE = False
@@ -35,9 +36,10 @@ except ImportError:
 from auth.oauth_common_handlers import (
     handle_oauth_authorize,
     handle_proxy_token_exchange,
+    handle_oauth_protected_resource,
     handle_oauth_authorization_server,
     handle_oauth_client_config,
-    handle_oauth_register
+    handle_oauth_register,
 )
 
 logger = logging.getLogger(__name__)
@@ -45,12 +47,12 @@ logger = logging.getLogger(__name__)
 
 class GoogleRemoteAuthProvider(RemoteAuthProvider):
     """
-    RemoteAuthProvider implementation for Google Workspace using FastMCP v2.11.1+.
+    RemoteAuthProvider implementation for Google Workspace.
 
     This provider extends RemoteAuthProvider to add:
     - OAuth proxy endpoints for CORS workaround
     - Dynamic client registration support
-    - Enhanced session management with issuer tracking
+    - Session management with issuer tracking
     """
 
     def __init__(self):
@@ -65,51 +67,90 @@ class GoogleRemoteAuthProvider(RemoteAuthProvider):
         self.port = int(os.getenv("PORT", os.getenv("WORKSPACE_MCP_PORT", 8000)))
 
         if not self.client_id:
-            logger.error("GOOGLE_OAUTH_CLIENT_ID not set - OAuth 2.1 authentication will not work")
+            logger.error(
-            raise ValueError("GOOGLE_OAUTH_CLIENT_ID environment variable is required for OAuth 2.1 authentication")
+                "GOOGLE_OAUTH_CLIENT_ID not set - OAuth 2.1 authentication will not work"
+            )
+            raise ValueError(
+                "GOOGLE_OAUTH_CLIENT_ID environment variable is required for OAuth 2.1 authentication"
+            )
 
         # Configure JWT verifier for Google tokens
         token_verifier = JWTVerifier(
             jwks_uri="https://www.googleapis.com/oauth2/v3/certs",
             issuer="https://accounts.google.com",
             audience=self.client_id,  # Always use actual client_id
-            algorithm="RS256"
+            algorithm="RS256",
         )
 
-        # Initialize RemoteAuthProvider with local server as the authorization server
+        # Initialize RemoteAuthProvider with base URL (no /mcp/ suffix)
-        # This ensures OAuth discovery points to our proxy endpoints instead of Google directly
+        # The /mcp/ resource URL is handled in the protected resource metadata endpoint
         super().__init__(
             token_verifier=token_verifier,
             authorization_servers=[AnyHttpUrl(f"{self.base_url}:{self.port}")],
-            resource_server_url=f"{self.base_url}:{self.port}"
+            resource_server_url=f"{self.base_url}:{self.port}",
         )
 
-        logger.debug("GoogleRemoteAuthProvider initialized")
+        logger.debug("GoogleRemoteAuthProvider")
 
     def get_routes(self) -> List[Route]:
         """
-        Add custom OAuth proxy endpoints to the standard protected resource routes.
+        Add OAuth routes at canonical locations.
-        
-        These endpoints work around Google's CORS restrictions and provide
-        dynamic client registration support.
         """
         # Get the standard OAuth protected resource routes from RemoteAuthProvider
-        routes = super().get_routes()
+        parent_routes = super().get_routes()
 
-        # Log what routes we're getting from the parent
+        # Filter out the parent's oauth-protected-resource route since we're replacing it
-        logger.debug(f"Registered {len(routes)} OAuth routes from parent")
+        routes = [
+            r
+            for r in parent_routes
+            if r.path != "/.well-known/oauth-protected-resource"
+        ]
 
-        # Add our custom proxy endpoints using common handlers
+        # Add our custom OAuth discovery endpoint that returns /mcp/ as the resource
-        routes.append(Route("/oauth2/authorize", handle_oauth_authorize, methods=["GET", "OPTIONS"]))
+        routes.append(
+            Route(
+                "/.well-known/oauth-protected-resource",
+                handle_oauth_protected_resource,
+                methods=["GET", "OPTIONS"],
+            )
+        )
 
-        routes.append(Route("/oauth2/token", handle_proxy_token_exchange, methods=["POST", "OPTIONS"]))
+        routes.append(
+            Route(
+                "/.well-known/oauth-authorization-server",
+                handle_oauth_authorization_server,
+                methods=["GET", "OPTIONS"],
+            )
+        )
 
-        routes.append(Route("/oauth2/register", handle_oauth_register, methods=["POST", "OPTIONS"]))
+        routes.append(
+            Route(
+                "/.well-known/oauth-client",
+                handle_oauth_client_config,
+                methods=["GET", "OPTIONS"],
+            )
+        )
 
-        routes.append(Route("/.well-known/oauth-authorization-server", handle_oauth_authorization_server, methods=["GET", "OPTIONS"]))
+        # Add OAuth flow endpoints
-        
+        routes.append(
-        routes.append(Route("/.well-known/oauth-client", handle_oauth_client_config, methods=["GET", "OPTIONS"]))
+            Route(
+                "/oauth2/authorize", handle_oauth_authorize, methods=["GET", "OPTIONS"]
+            )
+        )
+        routes.append(
+            Route(
+                "/oauth2/token",
+                handle_proxy_token_exchange,
+                methods=["POST", "OPTIONS"],
+            )
+        )
+        routes.append(
+            Route(
+                "/oauth2/register", handle_oauth_register, methods=["POST", "OPTIONS"]
+            )
+        )
 
+        logger.info(f"Registered {len(routes)} OAuth routes")
         return routes
 
     async def verify_token(self, token: str) -> Optional[object]:
@@ -121,22 +162,30 @@ class GoogleRemoteAuthProvider(RemoteAuthProvider):
         """
         # Check if this is a Google OAuth access token (starts with ya29.)
         if token.startswith("ya29."):
-            logger.debug("Detected Google OAuth access token, using tokeninfo verification")
+            logger.debug(
+                "Detected Google OAuth access token, using tokeninfo verification"
+            )
 
             try:
                 # Verify the access token using Google's tokeninfo endpoint
                 async with aiohttp.ClientSession() as session:
-                    url = f"https://oauth2.googleapis.com/tokeninfo?access_token={token}"
+                    url = (
+                        f"https://oauth2.googleapis.com/tokeninfo?access_token={token}"
+                    )
                     async with session.get(url) as response:
                         if response.status != 200:
-                            logger.error(f"Token verification failed: {response.status}")
+                            logger.error(
+                                f"Token verification failed: {response.status}"
+                            )
                             return None
 
                         token_info = await response.json()
 
                         # Verify the token is for our client
                         if token_info.get("aud") != self.client_id:
-                            logger.error(f"Token audience mismatch: expected {self.client_id}, got {token_info.get('aud')}")
+                            logger.error(
+                                f"Token audience mismatch: expected {self.client_id}, got {token_info.get('aud')}"
+                            )
                             return None
 
                         # Check if token is expired
@@ -151,7 +200,9 @@ class GoogleRemoteAuthProvider(RemoteAuthProvider):
 
                         # Calculate expires_at timestamp
                         expires_in = int(token_info.get("expires_in", 0))
-                        expires_at = int(time.time()) + expires_in if expires_in > 0 else 0
+                        expires_at = (
+                            int(time.time()) + expires_in if expires_in > 0 else 0
+                        )
 
                         access_token = SimpleNamespace(
                             claims={
@@ -166,12 +217,15 @@ class GoogleRemoteAuthProvider(RemoteAuthProvider):
                             client_id=self.client_id,  # Add client_id at top level
                             # Add other required fields
                             sub=token_info.get("sub", ""),
-                            email=token_info.get("email", "")
+                            email=token_info.get("email", ""),
                         )
 
                         user_email = token_info.get("email")
                         if user_email:
-                            from auth.oauth21_session_store import get_oauth21_session_store
+                            from auth.oauth21_session_store import (
+                                get_oauth21_session_store,
+                            )
+
                             store = get_oauth21_session_store()
                             session_id = f"google_{token_info.get('sub', 'unknown')}"
 
@@ -179,10 +233,13 @@ class GoogleRemoteAuthProvider(RemoteAuthProvider):
                             mcp_session_id = None
                             try:
                                 from fastmcp.server.dependencies import get_context
+
                                 ctx = get_context()
-                                if ctx and hasattr(ctx, 'session_id'):
+                                if ctx and hasattr(ctx, "session_id"):
                                     mcp_session_id = ctx.session_id
-                                    logger.debug(f"Binding MCP session {mcp_session_id} to user {user_email}")
+                                    logger.debug(
+                                        f"Binding MCP session {mcp_session_id} to user {user_email}"
+                                    )
                             except Exception:
                                 pass
 
@@ -193,7 +250,7 @@ class GoogleRemoteAuthProvider(RemoteAuthProvider):
                                 scopes=access_token.scopes,
                                 session_id=session_id,
                                 mcp_session_id=mcp_session_id,
-                                issuer="https://accounts.google.com"
+                                issuer="https://accounts.google.com",
                             )
 
                             logger.info(f"Verified OAuth token: {user_email}")
@@ -214,6 +271,7 @@ class GoogleRemoteAuthProvider(RemoteAuthProvider):
                 user_email = access_token.claims.get("email")
                 if user_email:
                     from auth.oauth21_session_store import get_oauth21_session_store
+
                     store = get_oauth21_session_store()
                     session_id = f"google_{access_token.claims.get('sub', 'unknown')}"
 
@@ -223,9 +281,11 @@ class GoogleRemoteAuthProvider(RemoteAuthProvider):
                         access_token=token,
                         scopes=access_token.scopes or [],
                         session_id=session_id,
-                        issuer="https://accounts.google.com"
+                        issuer="https://accounts.google.com",
                     )
 
-                    logger.debug(f"Successfully verified JWT token for user: {user_email}")
+                    logger.debug(
+                        f"Successfully verified JWT token for user: {user_email}"
+                    )
 
             return access_token

auth/oauth21_integration.py

@@ -160,23 +160,6 @@ def set_auth_layer(auth_layer):
     logger.info("set_auth_layer called - OAuth is now handled by FastMCP")
 
 
-_oauth21_enabled = False
-
-def is_oauth21_enabled() -> bool:
-    """
-    Check if the OAuth 2.1 authentication layer is active.
-    """
-    global _oauth21_enabled
-    return _oauth21_enabled
-
-
-def enable_oauth21():
-    """
-    Enable the OAuth 2.1 authentication layer.
-    """
-    global _oauth21_enabled
-    _oauth21_enabled = True
-    logger.debug("OAuth 2.1 authentication enabled")
 
 
 async def get_legacy_auth_service(
@@ -206,13 +189,16 @@ async def get_authenticated_google_service_oauth21(
     tool_name: str,
     user_google_email: str,
     required_scopes: list[str],
+    session_id: Optional[str] = None,
+    auth_token_email: Optional[str] = None,
+    allow_recent_auth: bool = False,
     context: Optional[Dict[str, Any]] = None,
 ) -> Tuple[Any, str]:
     """
     Enhanced version of get_authenticated_google_service that supports OAuth 2.1.
 
     This function checks for OAuth 2.1 session context and uses it if available,
-    otherwise falls back to legacy authentication.
+    otherwise falls back to legacy authentication based on configuration.
 
     Args:
         service_name: Google service name
@@ -220,20 +206,32 @@ async def get_authenticated_google_service_oauth21(
         tool_name: Tool name for logging
         user_google_email: User's Google email
         required_scopes: Required OAuth scopes
+        session_id: Optional OAuth session ID
+        auth_token_email: Optional authenticated user email from token
+        allow_recent_auth: Whether to allow recently authenticated sessions
         context: Optional context containing session information
 
     Returns:
         Tuple of (service instance, actual user email)
     """
+    # Check if OAuth 2.1 is truly enabled
+    if not is_oauth21_enabled():
+        logger.debug(f"[{tool_name}] OAuth 2.1 disabled, using legacy authentication")
+        return await get_legacy_auth_service(
+            service_name=service_name,
+            version=version,
+            tool_name=tool_name,
+            user_google_email=user_google_email,
+            required_scopes=required_scopes,
+        )
+    
     builder = get_oauth21_service_builder()
 
     # FastMCP handles context now - extract any session info
-    session_id = None
+    if not session_id and context:
-    auth_context = None
-
-    if context:
         session_id = builder.extract_session_from_context(context)
-        auth_context = context.get("auth_context")
+    
+    auth_context = context.get("auth_context") if context else None
 
     return await builder.get_authenticated_service_with_session(
         service_name=service_name,
@@ -244,3 +242,34 @@ async def get_authenticated_google_service_oauth21(
         session_id=session_id,
         auth_context=auth_context,
     )
+
+
+async def get_authenticated_google_service_oauth21_v2(
+    request: "OAuth21ServiceRequest",
+) -> Tuple[Any, str]:
+    """
+    Enhanced version of get_authenticated_google_service that supports OAuth 2.1.
+    
+    This version uses a parameter object to reduce function complexity and
+    improve maintainability. It's the recommended approach for new code.
+    
+    Args:
+        request: OAuth21ServiceRequest object containing all parameters
+        
+    Returns:
+        Tuple of (service instance, actual user email)
+    """
+    
+    # Delegate to the original function for now
+    # This provides a migration path while maintaining backward compatibility
+    return await get_authenticated_google_service_oauth21(
+        service_name=request.service_name,
+        version=request.version,
+        tool_name=request.tool_name,
+        user_google_email=request.user_google_email,
+        required_scopes=request.required_scopes,
+        session_id=request.session_id,
+        auth_token_email=request.auth_token_email,
+        allow_recent_auth=request.allow_recent_auth,
+        context=request.context,
+    )

auth/oauth_callback_server.py

@@ -5,7 +5,6 @@ In streamable-http mode: Uses the existing FastAPI server
 In stdio mode: Starts a minimal HTTP server just for OAuth callbacks
 """
 
-import os
 import asyncio
 import logging
 import threading
@@ -20,7 +19,7 @@ from urllib.parse import urlparse
 from auth.scopes import SCOPES
 from auth.oauth_responses import create_error_response, create_success_response, create_server_error_response
 from auth.google_auth import handle_auth_callback, check_client_secrets
-from core.config import get_oauth_redirect_uri
+from auth.oauth_config import get_oauth_redirect_uri
 
 logger = logging.getLogger(__name__)
 

auth/oauth_common_handlers.py

@@ -16,22 +16,24 @@ from google.oauth2.credentials import Credentials
 from auth.oauth21_session_store import store_token_session
 from auth.google_auth import save_credentials_to_file
 from auth.scopes import get_current_scopes
-from core.config import WORKSPACE_MCP_BASE_URI, WORKSPACE_MCP_PORT, get_oauth_base_url
+from auth.oauth_config import get_oauth_config
+from auth.oauth_error_handling import (
+    OAuthError, OAuthValidationError, OAuthConfigurationError,
+    create_oauth_error_response, validate_token_request,
+    validate_registration_request, get_development_cors_headers,
+    log_security_event
+)
 
 logger = logging.getLogger(__name__)
 
 
 async def handle_oauth_authorize(request: Request):
     """Common handler for OAuth authorization proxy."""
+    origin = request.headers.get("origin")
+    
     if request.method == "OPTIONS":
-        return JSONResponse(
+        cors_headers = get_development_cors_headers(origin)
-            content={},
+        return JSONResponse(content={}, headers=cors_headers)
-            headers={
-                "Access-Control-Allow-Origin": "*",
-                "Access-Control-Allow-Methods": "GET, OPTIONS",
-                "Access-Control-Allow-Headers": "Content-Type"
-            }
-        )
 
     # Get query parameters
     params = dict(request.query_params)
@@ -55,35 +57,40 @@ async def handle_oauth_authorize(request: Request):
     # Build Google authorization URL
     google_auth_url = "https://accounts.google.com/o/oauth2/v2/auth?" + urlencode(params)
 
-    # Return redirect
+    # Return redirect with development CORS headers if needed
+    cors_headers = get_development_cors_headers(origin)
     return RedirectResponse(
         url=google_auth_url,
         status_code=302,
-        headers={
+        headers=cors_headers
-            "Access-Control-Allow-Origin": "*"
-        }
     )
 
 
 async def handle_proxy_token_exchange(request: Request):
-    """Common handler for OAuth token exchange proxy."""
+    """Common handler for OAuth token exchange proxy with comprehensive error handling."""
-    if request.method == "OPTIONS":
+    origin = request.headers.get("origin")
-        return JSONResponse(
-            content={},
-            headers={
-                "Access-Control-Allow-Origin": "*",
-                "Access-Control-Allow-Methods": "POST, OPTIONS",
-                "Access-Control-Allow-Headers": "Content-Type, Authorization"
-            }
-        )
-    try:
-        # Get form data
-        body = await request.body()
-        content_type = request.headers.get("content-type", "application/x-www-form-urlencoded")
     
-        # Parse form data to add missing client credentials
+    if request.method == "OPTIONS":
+        cors_headers = get_development_cors_headers(origin)
+        return JSONResponse(content={}, headers=cors_headers)
+    try:
+        # Get form data with validation
+        try:
+            body = await request.body()
+            content_type = request.headers.get("content-type", "application/x-www-form-urlencoded")
+        except Exception as e:
+            raise OAuthValidationError(f"Failed to read request body: {e}")
+
+        # Parse and validate form data
         if content_type and "application/x-www-form-urlencoded" in content_type:
-            form_data = parse_qs(body.decode('utf-8'))
+            try:
+                form_data = parse_qs(body.decode('utf-8'))
+            except Exception as e:
+                raise OAuthValidationError(f"Invalid form data: {e}")
+
+            # Convert to single values and validate
+            request_data = {k: v[0] if v else '' for k, v in form_data.items()}
+            validate_token_request(request_data)
 
             # Check if client_id is missing (public client)
             if 'client_id' not in form_data or not form_data['client_id'][0]:
@@ -186,43 +193,57 @@ async def handle_proxy_token_exchange(request: Request):
                         except Exception as e:
                             logger.error(f"Failed to store OAuth session: {e}")
 
+                # Add development CORS headers
+                cors_headers = get_development_cors_headers(origin)
+                response_headers = {
+                    "Content-Type": "application/json",
+                    "Cache-Control": "no-store"
+                }
+                response_headers.update(cors_headers)
+                
                 return JSONResponse(
                     status_code=response.status,
                     content=response_data,
-                    headers={
+                    headers=response_headers
-                        "Content-Type": "application/json",
-                        "Access-Control-Allow-Origin": "*",
-                        "Cache-Control": "no-store"
-                    }
                 )
 
+    except OAuthError as e:
+        log_security_event("oauth_token_exchange_error", {
+            "error_code": e.error_code,
+            "description": e.description
+        }, request)
+        return create_oauth_error_response(e, origin)
     except Exception as e:
-        logger.error(f"Error in token proxy: {e}")
+        logger.error(f"Unexpected error in token proxy: {e}", exc_info=True)
-        return JSONResponse(
+        log_security_event("oauth_token_exchange_unexpected_error", {
-            status_code=500,
+            "error": str(e)
-            content={"error": "server_error", "error_description": str(e)},
+        }, request)
-            headers={"Access-Control-Allow-Origin": "*"}
+        error = OAuthConfigurationError("Internal server error")
-        )
+        return create_oauth_error_response(error, origin)
 
 
 async def handle_oauth_protected_resource(request: Request):
-    """Common handler for OAuth protected resource metadata."""
+    """
-    if request.method == "OPTIONS":
+    Handle OAuth protected resource metadata requests.
-        return JSONResponse(
+    """
-            content={},
+    origin = request.headers.get("origin")
-            headers={
-                "Access-Control-Allow-Origin": "*",
-                "Access-Control-Allow-Methods": "GET, OPTIONS",
-                "Access-Control-Allow-Headers": "Content-Type"
-            }
-        )
     
-    base_url = get_oauth_base_url()
+    # Handle preflight
+    if request.method == "OPTIONS":
+        cors_headers = get_development_cors_headers(origin)
+        return JSONResponse(content={}, headers=cors_headers)
+
+    config = get_oauth_config()
+    base_url = config.get_oauth_base_url()
+
+    # For streamable-http transport, the MCP server runs at /mcp
+    # This is the actual resource being protected
+    resource_url = f"{base_url}/mcp"
+
+    # Build metadata response per RFC 9449
     metadata = {
-        "resource": base_url,
+        "resource": resource_url,  # The MCP server endpoint that needs protection
-        "authorization_servers": [
+        "authorization_servers": [base_url],  # Our proxy acts as the auth server
-            base_url
-        ],
         "bearer_methods_supported": ["header"],
         "scopes_supported": get_current_scopes(),
         "resource_documentation": "https://developers.google.com/workspace",
@@ -230,179 +251,143 @@ async def handle_oauth_protected_resource(request: Request):
         "client_configuration_endpoint": f"{base_url}/.well-known/oauth-client",
     }
 
+    # Log the response for debugging
+    logger.debug(f"Returning protected resource metadata: {metadata}")
+
+    # Add development CORS headers
+    cors_headers = get_development_cors_headers(origin)
+    response_headers = {
+        "Content-Type": "application/json; charset=utf-8",
+        "Cache-Control": "public, max-age=3600"
+    }
+    response_headers.update(cors_headers)
+    
     return JSONResponse(
         content=metadata,
-        headers={
+        headers=response_headers
-            "Content-Type": "application/json",
-            "Access-Control-Allow-Origin": "*"
-        }
     )
 
 
 async def handle_oauth_authorization_server(request: Request):
-    """Common handler for OAuth authorization server metadata."""
+    """
+    Handle OAuth authorization server metadata.
+    """
+    origin = request.headers.get("origin")
+    
     if request.method == "OPTIONS":
-        return JSONResponse(
+        cors_headers = get_development_cors_headers(origin)
-            content={},
+        return JSONResponse(content={}, headers=cors_headers)
-            headers={
-                "Access-Control-Allow-Origin": "*",
-                "Access-Control-Allow-Methods": "GET, OPTIONS",
-                "Access-Control-Allow-Headers": "Content-Type"
-            }
-        )
 
-    # Get base URL once and reuse
+    config = get_oauth_config()
-    base_url = get_oauth_base_url()
     
-    try:
+    # Get authorization server metadata from centralized config
-        # Fetch metadata from Google
+    # Pass scopes directly to keep all metadata generation in one place
-        async with aiohttp.ClientSession() as session:
+    metadata = config.get_authorization_server_metadata(scopes=get_current_scopes())
-            url = "https://accounts.google.com/.well-known/openid-configuration"
-            async with session.get(url) as response:
-                if response.status == 200:
-                    metadata = await response.json()
 
-                    # Add OAuth 2.1 required fields
+    logger.debug(f"Returning authorization server metadata: {metadata}")
-                    metadata.setdefault("code_challenge_methods_supported", ["S256"])
-                    metadata.setdefault("pkce_required", True)
 
-                    # Override endpoints to use our proxies
+    # Add development CORS headers
-                    metadata["token_endpoint"] = f"{base_url}/oauth2/token"
+    cors_headers = get_development_cors_headers(origin)
-                    metadata["authorization_endpoint"] = f"{base_url}/oauth2/authorize"
+    response_headers = {
-                    metadata["enable_dynamic_registration"] = True
+        "Content-Type": "application/json; charset=utf-8",
-                    metadata["registration_endpoint"] = f"{base_url}/oauth2/register"
+        "Cache-Control": "public, max-age=3600"
-                    return JSONResponse(
+    }
-                        content=metadata,
+    response_headers.update(cors_headers)
-                        headers={
-                            "Content-Type": "application/json",
-                            "Access-Control-Allow-Origin": "*"
-                        }
-                    )
     
-        # Fallback metadata
+    return JSONResponse(
-        return JSONResponse(
+        content=metadata,
-            content={
+        headers=response_headers
-                "issuer": "https://accounts.google.com",
+    )
-                "authorization_endpoint": f"{base_url}/oauth2/authorize",
-                "token_endpoint": f"{base_url}/oauth2/token",
-                "userinfo_endpoint": "https://www.googleapis.com/oauth2/v2/userinfo",
-                "revocation_endpoint": "https://oauth2.googleapis.com/revoke",
-                "jwks_uri": "https://www.googleapis.com/oauth2/v3/certs",
-                "response_types_supported": ["code"],
-                "code_challenge_methods_supported": ["S256"],
-                "pkce_required": True,
-                "grant_types_supported": ["authorization_code", "refresh_token"],
-                "scopes_supported": get_current_scopes(),
-                "token_endpoint_auth_methods_supported": ["client_secret_basic", "client_secret_post"]
-            },
-            headers={
-                "Content-Type": "application/json",
-                "Access-Control-Allow-Origin": "*"
-            }
-        )
-
-    except Exception as e:
-        logger.error(f"Error fetching auth server metadata: {e}")
-        return JSONResponse(
-            status_code=500,
-            content={"error": "Failed to fetch authorization server metadata"},
-            headers={"Access-Control-Allow-Origin": "*"}
-        )
 
 
 async def handle_oauth_client_config(request: Request):
     """Common handler for OAuth client configuration."""
+    origin = request.headers.get("origin")
+    
     if request.method == "OPTIONS":
-        return JSONResponse(
+        cors_headers = get_development_cors_headers(origin)
-            content={},
+        return JSONResponse(content={}, headers=cors_headers)
-            headers={
-                "Access-Control-Allow-Origin": "*",
-                "Access-Control-Allow-Methods": "GET, OPTIONS",
-                "Access-Control-Allow-Headers": "Content-Type"
-            }
-        )
 
     client_id = os.getenv("GOOGLE_OAUTH_CLIENT_ID")
     if not client_id:
+        cors_headers = get_development_cors_headers(origin)
         return JSONResponse(
             status_code=404,
             content={"error": "OAuth not configured"},
-            headers={"Access-Control-Allow-Origin": "*"}
+            headers=cors_headers
         )
 
+    # Get OAuth configuration
+    config = get_oauth_config()
+
     return JSONResponse(
         content={
             "client_id": client_id,
             "client_name": "Google Workspace MCP Server",
-            "client_uri": f"{WORKSPACE_MCP_BASE_URI}:{WORKSPACE_MCP_PORT}",
+            "client_uri": config.base_url,
             "redirect_uris": [
-                f"{WORKSPACE_MCP_BASE_URI}:{WORKSPACE_MCP_PORT}/oauth2callback",
+                f"{config.base_url}/oauth2callback",
                 "http://localhost:5173/auth/callback"
             ],
             "grant_types": ["authorization_code", "refresh_token"],
             "response_types": ["code"],
             "scope": " ".join(get_current_scopes()),
             "token_endpoint_auth_method": "client_secret_basic",
-            "code_challenge_methods": ["S256"]
+            "code_challenge_methods": config.supported_code_challenge_methods[:1]  # Primary method only
         },
         headers={
-            "Content-Type": "application/json",
+            "Content-Type": "application/json; charset=utf-8",
-            "Access-Control-Allow-Origin": "*"
+            "Cache-Control": "public, max-age=3600",
+            **get_development_cors_headers(origin)
         }
     )
 
 
 async def handle_oauth_register(request: Request):
-    """Common handler for OAuth dynamic client registration."""
+    """Common handler for OAuth dynamic client registration with comprehensive error handling."""
+    origin = request.headers.get("origin")
+    
     if request.method == "OPTIONS":
-        return JSONResponse(
+        cors_headers = get_development_cors_headers(origin)
-            content={},
+        return JSONResponse(content={}, headers=cors_headers)
-            headers={
-                "Access-Control-Allow-Origin": "*",
-                "Access-Control-Allow-Methods": "POST, OPTIONS",
-                "Access-Control-Allow-Headers": "Content-Type, Authorization"
-            }
-        )
 
-    client_id = os.getenv("GOOGLE_OAUTH_CLIENT_ID")
+    config = get_oauth_config()
-    client_secret = os.getenv("GOOGLE_OAUTH_CLIENT_SECRET")
 
-    if not client_id or not client_secret:
+    if not config.is_configured():
-        return JSONResponse(
+        error = OAuthConfigurationError("OAuth client credentials not configured")
-            status_code=400,
+        return create_oauth_error_response(error, origin)
-            content={"error": "invalid_request", "error_description": "OAuth not configured"},
-            headers={"Access-Control-Allow-Origin": "*"}
-        )
 
     try:
-        # Parse the registration request
+        # Parse and validate the registration request
-        body = await request.json()
+        try:
-        logger.info(f"Dynamic client registration request received: {body}")
+            body = await request.json()
+        except Exception as e:
+            raise OAuthValidationError(f"Invalid JSON in registration request: {e}")
+
+        validate_registration_request(body)
+        logger.info("Dynamic client registration request received")
 
         # Extract redirect URIs from the request or use defaults
         redirect_uris = body.get("redirect_uris", [])
         if not redirect_uris:
-            redirect_uris = [
+            redirect_uris = config.get_redirect_uris()
-                f"{WORKSPACE_MCP_BASE_URI}:{WORKSPACE_MCP_PORT}/oauth2callback",
-                "http://localhost:5173/auth/callback"
-            ]
 
         # Build the registration response with our pre-configured credentials
         response_data = {
-            "client_id": client_id,
+            "client_id": config.client_id,
-            "client_secret": client_secret,
+            "client_secret": config.client_secret,
             "client_name": body.get("client_name", "Google Workspace MCP Server"),
-            "client_uri": body.get("client_uri", f"{WORKSPACE_MCP_BASE_URI}:{WORKSPACE_MCP_PORT}"),
+            "client_uri": body.get("client_uri", config.base_url),
             "redirect_uris": redirect_uris,
             "grant_types": body.get("grant_types", ["authorization_code", "refresh_token"]),
             "response_types": body.get("response_types", ["code"]),
             "scope": body.get("scope", " ".join(get_current_scopes())),
             "token_endpoint_auth_method": body.get("token_endpoint_auth_method", "client_secret_basic"),
-            "code_challenge_methods": ["S256"],
+            "code_challenge_methods": config.supported_code_challenge_methods,
             # Additional OAuth 2.1 fields
             "client_id_issued_at": int(time.time()),
             "registration_access_token": "not-required",  # We don't implement client management
-            "registration_client_uri": f"{get_oauth_base_url()}/oauth2/register/{client_id}"
+            "registration_client_uri": f"{config.get_oauth_base_url()}/oauth2/register/{config.client_id}"
         }
 
         logger.info("Dynamic client registration successful - returning pre-configured Google credentials")
@@ -412,15 +397,21 @@ async def handle_oauth_register(request: Request):
             content=response_data,
             headers={
                 "Content-Type": "application/json",
-                "Access-Control-Allow-Origin": "*",
+                "Cache-Control": "no-store",
-                "Cache-Control": "no-store"
+                **get_development_cors_headers(origin)
             }
         )
 
+    except OAuthError as e:
+        log_security_event("oauth_registration_error", {
+            "error_code": e.error_code,
+            "description": e.description
+        }, request)
+        return create_oauth_error_response(e, origin)
     except Exception as e:
-        logger.error(f"Error in dynamic client registration: {e}")
+        logger.error(f"Unexpected error in client registration: {e}", exc_info=True)
-        return JSONResponse(
+        log_security_event("oauth_registration_unexpected_error", {
-            status_code=400,
+            "error": str(e)
-            content={"error": "invalid_request", "error_description": str(e)},
+        }, request)
-            headers={"Access-Control-Allow-Origin": "*"}
+        error = OAuthConfigurationError("Internal server error")
-        )
+        return create_oauth_error_response(error, origin)

auth/oauth_config.py

@@ -0,0 +1,319 @@
+"""
+OAuth Configuration Management
+
+This module centralizes OAuth-related configuration to eliminate hardcoded values
+scattered throughout the codebase. It provides environment variable support and
+sensible defaults for all OAuth-related settings.
+
+Supports both OAuth 2.0 and OAuth 2.1 with automatic client capability detection.
+"""
+
+import os
+from typing import List, Optional, Dict, Any
+
+
+class OAuthConfig:
+    """
+    Centralized OAuth configuration management.
+
+    This class eliminates the hardcoded configuration anti-pattern identified
+    in the challenge review by providing a single source of truth for all
+    OAuth-related configuration values.
+    """
+
+    def __init__(self):
+        # Base server configuration
+        self.base_uri = os.getenv("WORKSPACE_MCP_BASE_URI", "http://localhost")
+        self.port = int(os.getenv("PORT", os.getenv("WORKSPACE_MCP_PORT", "8000")))
+        self.base_url = f"{self.base_uri}:{self.port}"
+
+        # OAuth client configuration
+        self.client_id = os.getenv("GOOGLE_OAUTH_CLIENT_ID")
+        self.client_secret = os.getenv("GOOGLE_OAUTH_CLIENT_SECRET")
+
+        # OAuth 2.1 configuration
+        self.oauth21_enabled = os.getenv("MCP_ENABLE_OAUTH21", "false").lower() == "true"
+        self.pkce_required = self.oauth21_enabled  # PKCE is mandatory in OAuth 2.1
+        self.supported_code_challenge_methods = ["S256", "plain"] if not self.oauth21_enabled else ["S256"]
+
+        # Transport mode (will be set at runtime)
+        self._transport_mode = "stdio"  # Default
+
+        # Redirect URI configuration
+        self.redirect_uri = self._get_redirect_uri()
+
+    def _get_redirect_uri(self) -> str:
+        """
+        Get the OAuth redirect URI, supporting reverse proxy configurations.
+
+        Returns:
+            The configured redirect URI
+        """
+        explicit_uri = os.getenv("GOOGLE_OAUTH_REDIRECT_URI")
+        if explicit_uri:
+            return explicit_uri
+        return f"{self.base_url}/oauth2callback"
+
+    def get_redirect_uris(self) -> List[str]:
+        """
+        Get all valid OAuth redirect URIs.
+
+        Returns:
+            List of all supported redirect URIs
+        """
+        uris = []
+
+        # Primary redirect URI
+        uris.append(self.redirect_uri)
+
+        # Custom redirect URIs from environment
+        custom_uris = os.getenv("OAUTH_CUSTOM_REDIRECT_URIS")
+        if custom_uris:
+            uris.extend([uri.strip() for uri in custom_uris.split(",")])
+
+        # Remove duplicates while preserving order
+        return list(dict.fromkeys(uris))
+
+    def get_allowed_origins(self) -> List[str]:
+        """
+        Get allowed CORS origins for OAuth endpoints.
+
+        Returns:
+            List of allowed origins for CORS
+        """
+        origins = []
+
+        # Server's own origin
+        origins.append(self.base_url)
+
+        # VS Code and development origins
+        origins.extend([
+            "vscode-webview://",
+            "https://vscode.dev",
+            "https://github.dev",
+        ])
+
+        # Custom origins from environment
+        custom_origins = os.getenv("OAUTH_ALLOWED_ORIGINS")
+        if custom_origins:
+            origins.extend([origin.strip() for origin in custom_origins.split(",")])
+
+        return list(dict.fromkeys(origins))
+
+    def is_configured(self) -> bool:
+        """
+        Check if OAuth is properly configured.
+
+        Returns:
+            True if OAuth client credentials are available
+        """
+        return bool(self.client_id and self.client_secret)
+
+    def get_oauth_base_url(self) -> str:
+        """
+        Get OAuth base URL for constructing OAuth endpoints.
+
+        Returns:
+            Base URL for OAuth endpoints
+        """
+        return self.base_url
+
+    def validate_redirect_uri(self, uri: str) -> bool:
+        """
+        Validate if a redirect URI is allowed.
+
+        Args:
+            uri: The redirect URI to validate
+
+        Returns:
+            True if the URI is allowed, False otherwise
+        """
+        allowed_uris = self.get_redirect_uris()
+        return uri in allowed_uris
+
+    def get_environment_summary(self) -> dict:
+        """
+        Get a summary of the current OAuth configuration.
+
+        Returns:
+            Dictionary with configuration summary (excluding secrets)
+        """
+        return {
+            "base_url": self.base_url,
+            "redirect_uri": self.redirect_uri,
+            "client_configured": bool(self.client_id),
+            "oauth21_enabled": self.oauth21_enabled,
+            "pkce_required": self.pkce_required,
+            "transport_mode": self._transport_mode,
+            "total_redirect_uris": len(self.get_redirect_uris()),
+            "total_allowed_origins": len(self.get_allowed_origins()),
+        }
+
+    def set_transport_mode(self, mode: str) -> None:
+        """
+        Set the current transport mode for OAuth callback handling.
+
+        Args:
+            mode: Transport mode ("stdio", "streamable-http", etc.)
+        """
+        self._transport_mode = mode
+
+    def get_transport_mode(self) -> str:
+        """
+        Get the current transport mode.
+
+        Returns:
+            Current transport mode
+        """
+        return self._transport_mode
+
+    def is_oauth21_enabled(self) -> bool:
+        """
+        Check if OAuth 2.1 mode is enabled.
+
+        Returns:
+            True if OAuth 2.1 is enabled
+        """
+        return self.oauth21_enabled
+
+    def detect_oauth_version(self, request_params: Dict[str, Any]) -> str:
+        """
+        Detect OAuth version based on request parameters.
+
+        This method implements a conservative detection strategy:
+        - Only returns "oauth21" when we have clear indicators
+        - Defaults to "oauth20" for backward compatibility
+        - Respects the global oauth21_enabled flag
+
+        Args:
+            request_params: Request parameters from authorization or token request
+
+        Returns:
+            "oauth21" or "oauth20" based on detection
+        """
+        # If OAuth 2.1 is not enabled globally, always return OAuth 2.0
+        if not self.oauth21_enabled:
+            return "oauth20"
+
+        # Use the structured type for cleaner detection logic
+        from auth.oauth_types import OAuthVersionDetectionParams
+        params = OAuthVersionDetectionParams.from_request(request_params)
+
+        # Clear OAuth 2.1 indicator: PKCE is present
+        if params.has_pkce:
+            return "oauth21"
+
+        # For public clients in OAuth 2.1 mode, we require PKCE
+        # But since they didn't send PKCE, fall back to OAuth 2.0
+        # This ensures backward compatibility
+
+        # Default to OAuth 2.0 for maximum compatibility
+        return "oauth20"
+
+    def get_authorization_server_metadata(self, scopes: Optional[List[str]] = None) -> Dict[str, Any]:
+        """
+        Get OAuth authorization server metadata per RFC 8414.
+
+        Args:
+            scopes: Optional list of supported scopes to include in metadata
+
+        Returns:
+            Authorization server metadata dictionary
+        """
+        metadata = {
+            "issuer": self.base_url,
+            "authorization_endpoint": f"{self.base_url}/oauth2/authorize",
+            "token_endpoint": f"{self.base_url}/oauth2/token",
+            "registration_endpoint": f"{self.base_url}/oauth2/register",
+            "jwks_uri": "https://www.googleapis.com/oauth2/v3/certs",
+            "response_types_supported": ["code", "token"],
+            "grant_types_supported": ["authorization_code", "refresh_token"],
+            "token_endpoint_auth_methods_supported": ["client_secret_post", "client_secret_basic"],
+            "code_challenge_methods_supported": self.supported_code_challenge_methods,
+        }
+
+        # Include scopes if provided
+        if scopes is not None:
+            metadata["scopes_supported"] = scopes
+
+        # Add OAuth 2.1 specific metadata
+        if self.oauth21_enabled:
+            metadata["pkce_required"] = True
+            # OAuth 2.1 deprecates implicit flow
+            metadata["response_types_supported"] = ["code"]
+            # OAuth 2.1 requires exact redirect URI matching
+            metadata["require_exact_redirect_uri"] = True
+
+        return metadata
+
+
+# Global configuration instance
+_oauth_config = None
+
+
+def get_oauth_config() -> OAuthConfig:
+    """
+    Get the global OAuth configuration instance.
+
+    Returns:
+        The singleton OAuth configuration instance
+    """
+    global _oauth_config
+    if _oauth_config is None:
+        _oauth_config = OAuthConfig()
+    return _oauth_config
+
+
+def reload_oauth_config() -> OAuthConfig:
+    """
+    Reload the OAuth configuration from environment variables.
+
+    This is useful for testing or when environment variables change.
+
+    Returns:
+        The reloaded OAuth configuration instance
+    """
+    global _oauth_config
+    _oauth_config = OAuthConfig()
+    return _oauth_config
+
+
+# Convenience functions for backward compatibility
+def get_oauth_base_url() -> str:
+    """Get OAuth base URL."""
+    return get_oauth_config().get_oauth_base_url()
+
+
+def get_redirect_uris() -> List[str]:
+    """Get all valid OAuth redirect URIs."""
+    return get_oauth_config().get_redirect_uris()
+
+
+def get_allowed_origins() -> List[str]:
+    """Get allowed CORS origins."""
+    return get_oauth_config().get_allowed_origins()
+
+
+def is_oauth_configured() -> bool:
+    """Check if OAuth is properly configured."""
+    return get_oauth_config().is_configured()
+
+
+def set_transport_mode(mode: str) -> None:
+    """Set the current transport mode."""
+    get_oauth_config().set_transport_mode(mode)
+
+
+def get_transport_mode() -> str:
+    """Get the current transport mode."""
+    return get_oauth_config().get_transport_mode()
+
+
+def is_oauth21_enabled() -> bool:
+    """Check if OAuth 2.1 is enabled."""
+    return get_oauth_config().is_oauth21_enabled()
+
+
+def get_oauth_redirect_uri() -> str:
+    """Get the primary OAuth redirect URI."""
+    return get_oauth_config().redirect_uri

auth/oauth_error_handling.py

@@ -0,0 +1,321 @@
+"""
+OAuth Error Handling and Validation
+
+This module provides comprehensive error handling and input validation for OAuth
+endpoints, addressing the inconsistent error handling identified in the challenge review.
+"""
+
+import logging
+from typing import Optional, Dict, Any, List
+from starlette.responses import JSONResponse
+from starlette.requests import Request
+from urllib.parse import urlparse
+import re
+
+logger = logging.getLogger(__name__)
+
+
+class OAuthError(Exception):
+    """Base exception for OAuth-related errors."""
+    
+    def __init__(self, error_code: str, description: str, status_code: int = 400):
+        self.error_code = error_code
+        self.description = description
+        self.status_code = status_code
+        super().__init__(f"{error_code}: {description}")
+
+
+class OAuthValidationError(OAuthError):
+    """Exception for OAuth validation errors."""
+    
+    def __init__(self, description: str, field: Optional[str] = None):
+        error_code = "invalid_request"
+        if field:
+            description = f"Invalid {field}: {description}"
+        super().__init__(error_code, description, 400)
+
+
+class OAuthConfigurationError(OAuthError):
+    """Exception for OAuth configuration errors."""
+    
+    def __init__(self, description: str):
+        super().__init__("server_error", description, 500)
+
+
+def create_oauth_error_response(error: OAuthError, origin: Optional[str] = None) -> JSONResponse:
+    """
+    Create a standardized OAuth error response.
+    
+    Args:
+        error: The OAuth error to convert to a response
+        origin: Optional origin for development CORS headers
+        
+    Returns:
+        JSONResponse with standardized error format
+    """
+    headers = {
+        "Content-Type": "application/json",
+        "Cache-Control": "no-store"
+    }
+    
+    # Add development CORS headers if needed
+    cors_headers = get_development_cors_headers(origin)
+    headers.update(cors_headers)
+    
+    content = {
+        "error": error.error_code,
+        "error_description": error.description
+    }
+    
+    logger.warning(f"OAuth error response: {error.error_code} - {error.description}")
+    
+    return JSONResponse(
+        status_code=error.status_code,
+        content=content,
+        headers=headers
+    )
+
+
+def validate_redirect_uri(uri: str) -> None:
+    """
+    Validate an OAuth redirect URI.
+    
+    Args:
+        uri: The redirect URI to validate
+        
+    Raises:
+        OAuthValidationError: If the URI is invalid
+    """
+    if not uri:
+        raise OAuthValidationError("Redirect URI is required", "redirect_uri")
+    
+    try:
+        parsed = urlparse(uri)
+    except Exception:
+        raise OAuthValidationError("Malformed redirect URI", "redirect_uri")
+    
+    # Basic URI validation
+    if not parsed.scheme or not parsed.netloc:
+        raise OAuthValidationError("Redirect URI must be absolute", "redirect_uri")
+    
+    # Security checks
+    if parsed.scheme not in ["http", "https"]:
+        raise OAuthValidationError("Redirect URI must use HTTP or HTTPS", "redirect_uri")
+    
+    # Additional security for production
+    if parsed.scheme == "http" and parsed.hostname not in ["localhost", "127.0.0.1"]:
+        logger.warning(f"Insecure redirect URI: {uri}")
+
+
+def validate_client_id(client_id: str) -> None:
+    """
+    Validate an OAuth client ID.
+    
+    Args:
+        client_id: The client ID to validate
+        
+    Raises:
+        OAuthValidationError: If the client ID is invalid
+    """
+    if not client_id:
+        raise OAuthValidationError("Client ID is required", "client_id")
+    
+    if len(client_id) < 10:
+        raise OAuthValidationError("Client ID is too short", "client_id")
+    
+    # Basic format validation for Google client IDs
+    if not re.match(r'^[a-zA-Z0-9\-_.]+$', client_id):
+        raise OAuthValidationError("Client ID contains invalid characters", "client_id")
+
+
+def validate_authorization_code(code: str) -> None:
+    """
+    Validate an OAuth authorization code.
+    
+    Args:
+        code: The authorization code to validate
+        
+    Raises:
+        OAuthValidationError: If the code is invalid
+    """
+    if not code:
+        raise OAuthValidationError("Authorization code is required", "code")
+    
+    if len(code) < 10:
+        raise OAuthValidationError("Authorization code is too short", "code")
+    
+    # Check for suspicious patterns
+    if any(char in code for char in [' ', '\n', '\t', '<', '>']):
+        raise OAuthValidationError("Authorization code contains invalid characters", "code")
+
+
+def validate_scopes(scopes: List[str]) -> None:
+    """
+    Validate OAuth scopes.
+    
+    Args:
+        scopes: List of scopes to validate
+        
+    Raises:
+        OAuthValidationError: If the scopes are invalid
+    """
+    if not scopes:
+        return  # Empty scopes list is acceptable
+    
+    for scope in scopes:
+        if not scope:
+            raise OAuthValidationError("Empty scope is not allowed", "scope")
+        
+        if len(scope) > 200:
+            raise OAuthValidationError("Scope is too long", "scope")
+        
+        # Basic scope format validation
+        if not re.match(r'^[a-zA-Z0-9\-_.:/]+$', scope):
+            raise OAuthValidationError(f"Invalid scope format: {scope}", "scope")
+
+
+def validate_token_request(request_data: Dict[str, Any]) -> None:
+    """
+    Validate an OAuth token exchange request.
+    
+    Args:
+        request_data: The token request data to validate
+        
+    Raises:
+        OAuthValidationError: If the request is invalid
+    """
+    grant_type = request_data.get("grant_type")
+    if not grant_type:
+        raise OAuthValidationError("Grant type is required", "grant_type")
+    
+    if grant_type not in ["authorization_code", "refresh_token"]:
+        raise OAuthValidationError(f"Unsupported grant type: {grant_type}", "grant_type")
+    
+    if grant_type == "authorization_code":
+        code = request_data.get("code")
+        validate_authorization_code(code)
+        
+        redirect_uri = request_data.get("redirect_uri")
+        if redirect_uri:
+            validate_redirect_uri(redirect_uri)
+    
+    client_id = request_data.get("client_id")
+    if client_id:
+        validate_client_id(client_id)
+
+
+def validate_registration_request(request_data: Dict[str, Any]) -> None:
+    """
+    Validate an OAuth client registration request.
+    
+    Args:
+        request_data: The registration request data to validate
+        
+    Raises:
+        OAuthValidationError: If the request is invalid
+    """
+    # Validate redirect URIs if provided
+    redirect_uris = request_data.get("redirect_uris", [])
+    if redirect_uris:
+        if not isinstance(redirect_uris, list):
+            raise OAuthValidationError("redirect_uris must be an array", "redirect_uris")
+        
+        for uri in redirect_uris:
+            validate_redirect_uri(uri)
+    
+    # Validate grant types if provided
+    grant_types = request_data.get("grant_types", [])
+    if grant_types:
+        if not isinstance(grant_types, list):
+            raise OAuthValidationError("grant_types must be an array", "grant_types")
+        
+        allowed_grant_types = ["authorization_code", "refresh_token"]
+        for grant_type in grant_types:
+            if grant_type not in allowed_grant_types:
+                raise OAuthValidationError(f"Unsupported grant type: {grant_type}", "grant_types")
+    
+    # Validate response types if provided
+    response_types = request_data.get("response_types", [])
+    if response_types:
+        if not isinstance(response_types, list):
+            raise OAuthValidationError("response_types must be an array", "response_types")
+        
+        allowed_response_types = ["code"]
+        for response_type in response_types:
+            if response_type not in allowed_response_types:
+                raise OAuthValidationError(f"Unsupported response type: {response_type}", "response_types")
+
+
+def sanitize_user_input(value: str, max_length: int = 1000) -> str:
+    """
+    Sanitize user input to prevent injection attacks.
+    
+    Args:
+        value: The input value to sanitize
+        max_length: Maximum allowed length
+        
+    Returns:
+        Sanitized input value
+        
+    Raises:
+        OAuthValidationError: If the input is invalid
+    """
+    if not isinstance(value, str):
+        raise OAuthValidationError("Input must be a string")
+    
+    if len(value) > max_length:
+        raise OAuthValidationError(f"Input is too long (max {max_length} characters)")
+    
+    # Remove potentially dangerous characters
+    sanitized = re.sub(r'[<>"\'\0\n\r\t]', '', value)
+    
+    return sanitized.strip()
+
+
+def log_security_event(event_type: str, details: Dict[str, Any], request: Optional[Request] = None) -> None:
+    """
+    Log security-related events for monitoring.
+    
+    Args:
+        event_type: Type of security event
+        details: Event details
+        request: Optional request object for context
+    """
+    log_data = {
+        "event_type": event_type,
+        "details": details
+    }
+    
+    if request:
+        log_data["request"] = {
+            "method": request.method,
+            "path": request.url.path,
+            "user_agent": request.headers.get("user-agent", "unknown"),
+            "origin": request.headers.get("origin", "unknown")
+        }
+    
+    logger.warning(f"Security event: {log_data}")
+
+
+def get_development_cors_headers(origin: Optional[str] = None) -> Dict[str, str]:
+    """
+    Get minimal CORS headers for development scenarios only.
+    
+    Only allows localhost origins for development tools and inspectors.
+    
+    Args:
+        origin: The request origin (will be validated)
+        
+    Returns:
+        CORS headers for localhost origins only, empty dict otherwise
+    """
+    # Only allow localhost origins for development
+    if origin and (origin.startswith("http://localhost:") or origin.startswith("http://127.0.0.1:")):
+        return {
+            "Access-Control-Allow-Origin": origin,
+            "Access-Control-Allow-Methods": "GET, POST, OPTIONS",
+            "Access-Control-Allow-Headers": "Content-Type, Authorization",
+            "Access-Control-Max-Age": "3600"
+        }
+    
+    return {}

auth/oauth_types.py

@@ -0,0 +1,78 @@
+"""
+Type definitions for OAuth authentication.
+
+This module provides structured types for OAuth-related parameters,
+improving code maintainability and type safety.
+"""
+
+from dataclasses import dataclass
+from typing import Optional, List, Dict, Any
+
+
+@dataclass
+class OAuth21ServiceRequest:
+    """
+    Encapsulates parameters for OAuth 2.1 service authentication requests.
+    
+    This parameter object pattern reduces function complexity and makes
+    it easier to extend authentication parameters in the future.
+    """
+    service_name: str
+    version: str
+    tool_name: str
+    user_google_email: str
+    required_scopes: List[str]
+    session_id: Optional[str] = None
+    auth_token_email: Optional[str] = None
+    allow_recent_auth: bool = False
+    context: Optional[Dict[str, Any]] = None
+    
+    def to_legacy_params(self) -> dict:
+        """Convert to legacy parameter format for backward compatibility."""
+        return {
+            "service_name": self.service_name,
+            "version": self.version,
+            "tool_name": self.tool_name,
+            "user_google_email": self.user_google_email,
+            "required_scopes": self.required_scopes,
+        }
+
+
+@dataclass
+class OAuthVersionDetectionParams:
+    """
+    Parameters used for OAuth version detection.
+    
+    Encapsulates the various signals we use to determine
+    whether a client supports OAuth 2.1 or needs OAuth 2.0.
+    """
+    client_id: Optional[str] = None
+    client_secret: Optional[str] = None
+    code_challenge: Optional[str] = None
+    code_challenge_method: Optional[str] = None
+    code_verifier: Optional[str] = None
+    authenticated_user: Optional[str] = None
+    session_id: Optional[str] = None
+    
+    @classmethod
+    def from_request(cls, request_params: Dict[str, Any]) -> "OAuthVersionDetectionParams":
+        """Create from raw request parameters."""
+        return cls(
+            client_id=request_params.get("client_id"),
+            client_secret=request_params.get("client_secret"),
+            code_challenge=request_params.get("code_challenge"),
+            code_challenge_method=request_params.get("code_challenge_method"),
+            code_verifier=request_params.get("code_verifier"),
+            authenticated_user=request_params.get("authenticated_user"),
+            session_id=request_params.get("session_id"),
+        )
+    
+    @property
+    def has_pkce(self) -> bool:
+        """Check if PKCE parameters are present."""
+        return bool(self.code_challenge or self.code_verifier)
+    
+    @property
+    def is_public_client(self) -> bool:
+        """Check if this appears to be a public client (no secret)."""
+        return bool(self.client_id and not self.client_secret)

auth/service_decorator.py

@@ -334,9 +334,31 @@ def require_google_service(
                     # Log authentication status
                     logger.debug(f"[{tool_name}] Auth: {authenticated_user or 'none'} via {auth_method or 'none'} (session: {mcp_session_id[:8] if mcp_session_id else 'none'})")
 
-                    from auth.oauth21_integration import is_oauth21_enabled
+                    from auth.oauth_config import is_oauth21_enabled, get_oauth_config
+                    
+                    # Smart OAuth version detection and fallback
+                    use_oauth21 = False
+                    oauth_version = "oauth20"  # Default
                     
                     if is_oauth21_enabled():
+                        # OAuth 2.1 is enabled globally, check client capabilities
+                        # Try to detect from context if this is an OAuth 2.1 capable client
+                        config = get_oauth_config()
+                        
+                        # Build request params from context for version detection
+                        request_params = {}
+                        if authenticated_user:
+                            request_params["authenticated_user"] = authenticated_user
+                        if mcp_session_id:
+                            request_params["session_id"] = mcp_session_id
+                        
+                        # Detect OAuth version based on client capabilities
+                        oauth_version = config.detect_oauth_version(request_params)
+                        use_oauth21 = (oauth_version == "oauth21")
+                        
+                        logger.debug(f"[{tool_name}] OAuth version detected: {oauth_version}, will use OAuth 2.1: {use_oauth21}")
+
+                    if use_oauth21:
                         logger.debug(f"[{tool_name}] Using OAuth 2.1 flow")
                         # The downstream get_authenticated_google_service_oauth21 will handle
                         # whether the user's token is valid for the requested resource.
@@ -352,8 +374,8 @@ def require_google_service(
                             allow_recent_auth=False,
                         )
                     else:
-                        # If OAuth 2.1 is not enabled, always use the legacy authentication method.
+                        # Use legacy OAuth 2.0 authentication
-                        logger.debug(f"[{tool_name}] Using legacy OAuth flow")
+                        logger.debug(f"[{tool_name}] Using legacy OAuth 2.0 flow")
                         service, actual_user_email = await get_authenticated_google_service(
                             service_name=service_name,
                             version=service_version,
@@ -464,7 +486,7 @@ def require_multiple_services(service_configs: List[Dict[str, Any]]):
                         logger.debug(f"[{tool_name}] Could not get FastMCP context: {e}")
 
                     # Use the same logic as single service decorator
-                    from auth.oauth21_integration import is_oauth21_enabled
+                    from auth.oauth_config import is_oauth21_enabled
 
                     if is_oauth21_enabled():
                         logger.debug(f"[{tool_name}] Attempting OAuth 2.1 authentication flow for {service_type}.")

core/config.py

@@ -2,57 +2,34 @@
 Shared configuration for Google Workspace MCP server.
 This module holds configuration values that need to be shared across modules
 to avoid circular imports.
+
+NOTE: OAuth configuration has been moved to auth.oauth_config for centralization.
+This module now imports from there for backward compatibility.
 """
 
 import os
+from auth.oauth_config import (
+    get_oauth_base_url,
+    get_oauth_redirect_uri,
+    set_transport_mode,
+    get_transport_mode,
+    is_oauth21_enabled
+)
 
 # Server configuration
 WORKSPACE_MCP_PORT = int(os.getenv("PORT", os.getenv("WORKSPACE_MCP_PORT", 8000)))
 WORKSPACE_MCP_BASE_URI = os.getenv("WORKSPACE_MCP_BASE_URI", "http://localhost")
 
 # Disable USER_GOOGLE_EMAIL in OAuth 2.1 multi-user mode
-_oauth21_enabled = os.getenv("MCP_ENABLE_OAUTH21", "false").lower() == "true"
+USER_GOOGLE_EMAIL = None if is_oauth21_enabled() else os.getenv("USER_GOOGLE_EMAIL", None)
-USER_GOOGLE_EMAIL = None if _oauth21_enabled else os.getenv("USER_GOOGLE_EMAIL", None)
 
-# Transport mode (will be set by main.py)
+# Re-export OAuth functions for backward compatibility
-_current_transport_mode = "stdio"  # Default to stdio
+__all__ = [
-
+    'WORKSPACE_MCP_PORT',
-
+    'WORKSPACE_MCP_BASE_URI',
-def set_transport_mode(mode: str):
+    'USER_GOOGLE_EMAIL',
-    """Set the current transport mode for OAuth callback handling."""
+    'get_oauth_base_url',
-    global _current_transport_mode
+    'get_oauth_redirect_uri',
-    _current_transport_mode = mode
+    'set_transport_mode',
-
+    'get_transport_mode'
-
+]
-def get_transport_mode() -> str:
-    """Get the current transport mode."""
-    return _current_transport_mode
-
-
-# OAuth Configuration
-# Determine base URL and redirect URI once at startup
-_OAUTH_REDIRECT_URI = os.getenv("GOOGLE_OAUTH_REDIRECT_URI")
-if _OAUTH_REDIRECT_URI:
-    # Extract base URL from the redirect URI (remove the /oauth2callback path)
-    _OAUTH_BASE_URL = _OAUTH_REDIRECT_URI.removesuffix("/oauth2callback")
-else:
-    # Construct from base URI and port if not explicitly set
-    _OAUTH_BASE_URL = f"{WORKSPACE_MCP_BASE_URI}:{WORKSPACE_MCP_PORT}"
-    _OAUTH_REDIRECT_URI = f"{_OAUTH_BASE_URL}/oauth2callback"
-
-def get_oauth_base_url() -> str:
-    """Get OAuth base URL for constructing OAuth endpoints.
-    
-    Returns the base URL (without paths) for OAuth endpoints,
-    respecting GOOGLE_OAUTH_REDIRECT_URI for reverse proxy scenarios.
-    """
-    return _OAUTH_BASE_URL
-
-def get_oauth_redirect_uri() -> str:
-    """Get OAuth redirect URI based on current configuration.
-    
-    Returns the redirect URI configured at startup, either from
-    GOOGLE_OAUTH_REDIRECT_URI environment variable or constructed
-    from WORKSPACE_MCP_BASE_URI and WORKSPACE_MCP_PORT.
-    """
-    return _OAUTH_REDIRECT_URI

core/server.py

@@ -7,7 +7,6 @@ from fastapi.responses import HTMLResponse, JSONResponse
 from starlette.applications import Starlette
 from starlette.requests import Request
 from starlette.middleware import Middleware
-from fastapi.middleware.cors import CORSMiddleware
 
 from fastmcp import FastMCP
 
@@ -19,8 +18,6 @@ from auth.auth_info_middleware import AuthInfoMiddleware
 from auth.fastmcp_google_auth import GoogleWorkspaceAuthProvider
 from auth.scopes import SCOPES
 from core.config import (
-    WORKSPACE_MCP_PORT,
-    WORKSPACE_MCP_BASE_URI,
     USER_GOOGLE_EMAIL,
     get_transport_mode,
     set_transport_mode as _set_transport_mode,
@@ -41,31 +38,25 @@ logger = logging.getLogger(__name__)
 _auth_provider: Optional[Union[GoogleWorkspaceAuthProvider, GoogleRemoteAuthProvider]] = None
 
 # --- Middleware Definitions ---
-cors_middleware = Middleware(
-    CORSMiddleware,
-    allow_origins=["*"],
-    allow_credentials=True,
-    allow_methods=["*"],
-    allow_headers=["*"],
-)
 session_middleware = Middleware(MCPSessionMiddleware)
 
-# Custom FastMCP that adds CORS to streamable HTTP
+# Custom FastMCP that adds secure middleware stack for OAuth 2.1
-class CORSEnabledFastMCP(FastMCP):
+class SecureFastMCP(FastMCP):
     def streamable_http_app(self) -> "Starlette":
-        """Override to add CORS and session middleware to the app."""
+        """Override to add secure middleware stack for OAuth 2.1."""
         app = super().streamable_http_app()
-        # Add session middleware first (to set context before other middleware)
+
+        # Add middleware in order (first added = outermost layer)
+        # Session Management - extracts session info for MCP context
         app.user_middleware.insert(0, session_middleware)
-        # Add CORS as the second middleware
+
-        app.user_middleware.insert(1, cors_middleware)
         # Rebuild middleware stack
         app.middleware_stack = app.build_middleware_stack()
-        logger.info("Added session and CORS middleware to streamable HTTP app")
+        logger.info("Added middleware stack: Session Management")
         return app
 
 # --- Server Instance ---
-server = CORSEnabledFastMCP(
+server = SecureFastMCP(
     name="google_workspace",
     auth=None,
 )
@@ -86,32 +77,37 @@ def configure_server_for_http():
     This must be called BEFORE server.run().
     """
     global _auth_provider
+
     transport_mode = get_transport_mode()
 
     if transport_mode != "streamable-http":
         return
 
-    oauth21_enabled = os.getenv("MCP_ENABLE_OAUTH21", "false").lower() == "true"
+    # Use centralized OAuth configuration
+    from auth.oauth_config import get_oauth_config
+    config = get_oauth_config()
+    
+    # Check if OAuth 2.1 is enabled via centralized config
+    oauth21_enabled = config.is_oauth21_enabled()
 
     if oauth21_enabled:
-        if not os.getenv("GOOGLE_OAUTH_CLIENT_ID"):
+        if not config.is_configured():
-            logger.warning("⚠️  OAuth 2.1 enabled but GOOGLE_OAUTH_CLIENT_ID not set")
+            logger.warning("⚠️  OAuth 2.1 enabled but OAuth credentials not configured")
             return
 
         if GOOGLE_REMOTE_AUTH_AVAILABLE:
-            logger.info("🔐 OAuth 2.1 enabled")
+            logger.info("🔐 OAuth 2.1 enabled with automatic OAuth 2.0 fallback for legacy clients")
             try:
                 _auth_provider = GoogleRemoteAuthProvider()
                 server.auth = _auth_provider
                 set_auth_provider(_auth_provider)
-                from auth.oauth21_integration import enable_oauth21
+                logger.debug("OAuth 2.1 authentication enabled")
-                enable_oauth21()
             except Exception as e:
                 logger.error(f"Failed to initialize GoogleRemoteAuthProvider: {e}", exc_info=True)
         else:
             logger.error("OAuth 2.1 is enabled, but GoogleRemoteAuthProvider is not available.")
     else:
-        logger.info("OAuth 2.1 is DISABLED. Server will use legacy tool-based authentication.")
+        logger.info("OAuth 2.0 mode - Server will use legacy authentication.")
         server.auth = None
 
 def get_auth_provider() -> Optional[Union[GoogleWorkspaceAuthProvider, GoogleRemoteAuthProvider]]:

install_claude.py

@@ -1,256 +0,0 @@
-#!/usr/bin/env python3
-"""
-Auto-installer for Google Workspace MCP in Claude Desktop
-Enhanced version with OAuth configuration and installation options
-"""
-
-import json
-import os
-import platform
-import sys
-from pathlib import Path
-from typing import Dict, Optional, Tuple
-
-
-def get_claude_config_path() -> Path:
-    """Get the Claude Desktop config file path for the current platform."""
-    system = platform.system()
-    if system == "Darwin":  # macOS
-        return Path.home() / "Library/Application Support/Claude/claude_desktop_config.json"
-    elif system == "Windows":
-        appdata = os.environ.get("APPDATA")
-        if not appdata:
-            raise RuntimeError("APPDATA environment variable not found")
-        return Path(appdata) / "Claude/claude_desktop_config.json"
-    else:
-        raise RuntimeError(f"Unsupported platform: {system}")
-
-
-def prompt_yes_no(question: str, default: bool = True) -> bool:
-    """Prompt user for yes/no question."""
-    default_str = "Y/n" if default else "y/N"
-    while True:
-        response = input(f"{question} [{default_str}]: ").strip().lower()
-        if not response:
-            return default
-        if response in ['y', 'yes']:
-            return True
-        if response in ['n', 'no']:
-            return False
-        print("Please answer 'y' or 'n'")
-
-
-def get_oauth_credentials() -> Tuple[Optional[Dict[str, str]], Optional[str]]:
-    """Get OAuth credentials from user."""
-    print("\n🔑 OAuth Credentials Setup")
-    print("You need Google OAuth 2.0 credentials to use this server.")
-    print("\nYou can provide credentials in two ways:")
-    print("1. Environment variables (recommended for production)")
-    print("2. Client secrets JSON file")
-
-    use_env = prompt_yes_no("\nDo you want to use environment variables?", default=True)
-
-    env_vars = {}
-    client_secret_path = None
-
-    if use_env:
-        print("\n📝 Enter your OAuth credentials:")
-        client_id = input("Client ID (ends with .apps.googleusercontent.com): ").strip()
-        client_secret = input("Client Secret: ").strip()
-
-        if not client_id or not client_secret:
-            print("❌ Both Client ID and Client Secret are required!")
-            return None, None
-
-        env_vars["GOOGLE_OAUTH_CLIENT_ID"] = client_id
-        env_vars["GOOGLE_OAUTH_CLIENT_SECRET"] = client_secret
-
-        # Optional redirect URI
-        custom_redirect = input("Redirect URI (press Enter for default http://localhost:8000/oauth2callback): ").strip()
-        if custom_redirect:
-            env_vars["GOOGLE_OAUTH_REDIRECT_URI"] = custom_redirect
-
-    else:
-        print("\n📁 Client secrets file setup:")
-        default_path = "client_secret.json"
-        file_path = input(f"Path to client_secret.json file [{default_path}]: ").strip()
-
-        if not file_path:
-            file_path = default_path
-
-        # Check if file exists
-        if not Path(file_path).exists():
-            print(f"❌ File not found: {file_path}")
-            return None, None
-
-        client_secret_path = file_path
-
-    # Optional: Default user email
-    print("\n📧 Optional: Default user email (for single-user setups)")
-    user_email = input("Your Google email (press Enter to skip): ").strip()
-    if user_email:
-        env_vars["USER_GOOGLE_EMAIL"] = user_email
-
-    # Development mode
-    if prompt_yes_no("\n🔧 Enable development mode (OAUTHLIB_INSECURE_TRANSPORT)?", default=False):
-        env_vars["OAUTHLIB_INSECURE_TRANSPORT"] = "1"
-
-    return env_vars, client_secret_path
-
-
-def get_installation_options() -> Dict[str, any]:
-    """Get installation options from user."""
-    options = {}
-
-    print("\n⚙️  Installation Options")
-
-    # Installation method
-    print("\nChoose installation method:")
-    print("1. uvx (recommended - auto-installs from PyPI)")
-    print("2. Development mode (requires local repository)")
-
-    method = input("Select method [1]: ").strip()
-    if method == "2":
-        options["dev_mode"] = True
-        cwd = input("Path to google_workspace_mcp repository [current directory]: ").strip()
-        options["cwd"] = cwd if cwd else os.getcwd()
-    else:
-        options["dev_mode"] = False
-
-    # Single-user mode
-    if prompt_yes_no("\n👤 Enable single-user mode (simplified authentication)?", default=False):
-        options["single_user"] = True
-
-    # Tool selection
-    print("\n🛠️  Tool Selection")
-    print("Available tools: gmail, drive, calendar, docs, sheets, forms, chat")
-    print("Leave empty to enable all tools")
-    tools = input("Enter tools to enable (comma-separated): ").strip()
-    if tools:
-        options["tools"] = [t.strip() for t in tools.split(",")]
-
-    # Transport mode
-    if prompt_yes_no("\n🌐 Use HTTP transport mode (for debugging)?", default=False):
-        options["http_mode"] = True
-
-    return options
-
-
-def create_server_config(options: Dict, env_vars: Dict, client_secret_path: Optional[str]) -> Dict:
-    """Create the server configuration."""
-    config = {}
-
-    if options.get("dev_mode"):
-        config["command"] = "uv"
-        config["args"] = ["run", "--directory", options["cwd"], "main.py"]
-    else:
-        config["command"] = "uvx"
-        config["args"] = ["workspace-mcp"]
-
-    # Add command line arguments
-    if options.get("single_user"):
-        config["args"].append("--single-user")
-
-    if options.get("tools"):
-        config["args"].extend(["--tools"] + options["tools"])
-
-    if options.get("http_mode"):
-        config["args"].extend(["--transport", "streamable-http"])
-
-    # Add environment variables
-    if env_vars or client_secret_path:
-        config["env"] = {}
-
-    if env_vars:
-        config["env"].update(env_vars)
-
-    if client_secret_path:
-        config["env"]["GOOGLE_CLIENT_SECRET_PATH"] = client_secret_path
-
-    return config
-
-
-def main():
-    print("🚀 Google Workspace MCP Installer for Claude Desktop")
-    print("=" * 50)
-
-    try:
-        config_path = get_claude_config_path()
-
-        # Check if config already exists
-        existing_config = {}
-        if config_path.exists():
-            with open(config_path, 'r') as f:
-                existing_config = json.load(f)
-
-            if "mcpServers" in existing_config and "Google Workspace" in existing_config["mcpServers"]:
-                print(f"\n⚠️  Google Workspace MCP is already configured in {config_path}")
-                if not prompt_yes_no("Do you want to reconfigure it?", default=True):
-                    print("Installation cancelled.")
-                    return
-
-        # Get OAuth credentials
-        env_vars, client_secret_path = get_oauth_credentials()
-        if env_vars is None and client_secret_path is None:
-            print("\n❌ OAuth credentials are required. Installation cancelled.")
-            sys.exit(1)
-
-        # Get installation options
-        options = get_installation_options()
-
-        # Create server configuration
-        server_config = create_server_config(options, env_vars, client_secret_path)
-
-        # Prepare final config
-        if "mcpServers" not in existing_config:
-            existing_config["mcpServers"] = {}
-
-        existing_config["mcpServers"]["Google Workspace"] = server_config
-
-        # Create directory if needed
-        config_path.parent.mkdir(parents=True, exist_ok=True)
-
-        # Write configuration
-        with open(config_path, 'w') as f:
-            json.dump(existing_config, f, indent=2)
-
-        print("\n✅ Successfully configured Google Workspace MCP!")
-        print(f"📁 Config file: {config_path}")
-
-        print("\n📋 Configuration Summary:")
-        print(f"  • Installation method: {'Development' if options.get('dev_mode') else 'uvx (PyPI)'}")
-        print(f"  • Authentication: {'Environment variables' if env_vars else 'Client secrets file'}")
-        if options.get("single_user"):
-            print("  • Single-user mode: Enabled")
-        if options.get("tools"):
-            print(f"  • Tools: {', '.join(options['tools'])}")
-        else:
-            print("  • Tools: All enabled")
-        if options.get("http_mode"):
-            print("  • Transport: HTTP mode")
-        else:
-            print("  • Transport: stdio (default)")
-
-        print("\n🚀 Next steps:")
-        print("1. Restart Claude Desktop")
-        print("2. The Google Workspace tools will be available in your chats!")
-        print("\n💡 The server will start automatically when Claude Desktop needs it.")
-
-        if options.get("http_mode"):
-            print("\n⚠️  Note: HTTP mode requires additional setup.")
-            print("   You may need to install and configure mcp-remote.")
-            print("   See the README for details.")
-
-    except KeyboardInterrupt:
-        print("\n\nInstallation cancelled by user.")
-        sys.exit(0)
-    except Exception as e:
-        print(f"\n❌ Error: {e}")
-        print("\n📋 Manual installation:")
-        print("1. Open Claude Desktop Settings → Developer → Edit Config")
-        print("2. Add the server configuration shown in the README")
-        sys.exit(1)
-
-
-if __name__ == "__main__":
-    main()

main.py

@@ -4,17 +4,19 @@ import os
 import sys
 from importlib import metadata
 from dotenv import load_dotenv
+
+# Load environment variables from .env file BEFORE any other imports
+dotenv_path = os.path.join(os.path.dirname(os.path.abspath(__file__)), '.env')
+load_dotenv(dotenv_path=dotenv_path)
+
 from core.server import server, set_transport_mode, configure_server_for_http
+from auth.oauth_config import reload_oauth_config
+reload_oauth_config()
 
 # Suppress googleapiclient discovery cache warning
 logging.getLogger('googleapiclient.discovery_cache').setLevel(logging.ERROR)
 from core.utils import check_credentials_directory_permissions
 
-# Load environment variables from .env file, specifying an explicit path
-# This prevents accidentally loading a .env file from a different directory
-dotenv_path = os.path.join(os.path.dirname(os.path.abspath(__file__)), '.env')
-load_dotenv(dotenv_path=dotenv_path)
-
 logging.basicConfig(
     level=logging.INFO,
     format='%(asctime)s - %(name)s - %(levelname)s - %(message)s'
@@ -92,6 +94,7 @@ def main():
     # Active Configuration
     safe_print("⚙️ Active Configuration:")
 
+
     # Redact client secret for security
     client_secret = os.getenv('GOOGLE_OAUTH_CLIENT_SECRET', 'Not Set')
     redacted_secret = f"{client_secret[:4]}...{client_secret[-4:]}" if len(client_secret) > 8 else "Invalid or too short"
@@ -153,7 +156,6 @@ def main():
 
     safe_print("📊 Configuration Summary:")
     safe_print(f"   🔧 Tools Enabled: {len(tools_to_import)}/{len(tool_imports)}")
-    safe_print("   🔑 Auth Method: OAuth 2.0 with PKCE")
     safe_print(f"   📝 Log Level: {logging.getLogger().getEffectiveLevel()}")
     safe_print("")
 
@@ -182,10 +184,10 @@ def main():
         # Configure auth initialization for FastMCP lifecycle events
         if args.transport == 'streamable-http':
             configure_server_for_http()
-            safe_print(f"")
+            safe_print("")
             safe_print(f"🚀 Starting HTTP server on {base_uri}:{port}")
         else:
-            safe_print(f"")
+            safe_print("")
             safe_print("🚀 Starting STDIO server")
             # Start minimal OAuth callback server for stdio mode
             from auth.oauth_callback_server import ensure_oauth_callback_available