fix: use LITELLM_PROXY_BASE_URL for redirect_uri, close popup on unmount, no handleError in poll

- Add _get_callback_base_url() helper that prefers LITELLM_PROXY_BASE_URL
  env var over X-Forwarded-Host-derived URL, avoiding header spoofing in
  the security-sensitive OAuth2 redirect_uri construction.
- OAuth2ConnectButton.tsx: close popup on component unmount so orphaned
  popups don't persist when the user navigates away.
- getMcpOAuth2Status: remove handleError() call before throwing so the
  polling loop's catch block is the single error surface and no unexpected
  UI notifications fire on transient 2-second poll failures.

litellm/proxy/_experimental/mcp_server/openapi_oauth2_endpoints.py

@@ -59,6 +59,22 @@ router = APIRouter(tags=["mcp"])
 # ---------------------------------------------------------------------------
 
 
+def _get_callback_base_url(request: "Request") -> str:
+    """Return the base URL to use for the OAuth2 redirect_uri.
+
+    Prefers a statically-configured base URL (via the LITELLM_PROXY_BASE_URL
+    environment variable) over the request-derived URL to avoid trusting
+    potentially-spoofable X-Forwarded-Host headers in the OAuth2 security
+    context.  Falls back to the request-derived URL when the env var is unset.
+    """
+    import os
+
+    static_base = os.environ.get("LITELLM_PROXY_BASE_URL", "").rstrip("/")
+    if static_base:
+        return static_base
+    return get_request_base_url(request)
+
+
 def _purge_expired_states() -> None:
     now = time.time()
     expired = [k for k, v in _pending_oauth2_states.items() if v["expires_at"] < now]
@@ -206,7 +222,7 @@ async def openapi_oauth2_connect(
         "expires_at": timestamp + _STATE_TTL_SECONDS,
     }
 
-    base_url = get_request_base_url(request)
+    base_url = _get_callback_base_url(request)
     callback_url = f"{base_url}/v1/mcp/oauth2/callback"
 
     # NOTE: PKCE (RFC 7636 / OAuth 2.1) is not implemented here because this is
@@ -316,7 +332,7 @@ async def openapi_oauth2_callback(
             status_code=500,
         )
 
-    base_url = get_request_base_url(request)
+    base_url = _get_callback_base_url(request)
     callback_url = f"{base_url}/v1/mcp/oauth2/callback"
 
     token_request_data = {

ui/litellm-dashboard/src/components/mcp_tools/OAuth2ConnectButton.tsx

@@ -107,10 +107,15 @@ export const OAuth2ConnectButton: React.FC<OAuth2ConnectButtonProps> = ({
     }
   };
 
-  // Clean up on unmount
+  // Clean up on unmount: stop polling and close any open popup so it doesn't
+  // stay open after the user navigates away from the page.
   useEffect(() => {
     return () => {
       stopPolling();
+      if (popupRef.current && !popupRef.current.closed) {
+        popupRef.current.close();
+      }
+      popupRef.current = null;
     };
   }, []);
 

ui/litellm-dashboard/src/components/networking.tsx

@@ -6442,15 +6442,16 @@ export const getMcpOAuth2Status = async (
     });
 
     if (!response.ok) {
-      const errorData = await response.json();
+      // Do NOT call handleError here: this function is used inside a polling
+      // loop that catches and ignores errors.  Calling handleError would cause
+      // UI notifications to fire on every failed poll tick.
+      const errorData = await response.json().catch(() => ({}));
       const errorMessage = deriveErrorMessage(errorData);
-      handleError(errorMessage);
       throw new Error(errorMessage);
     }
 
     return await response.json();
   } catch (error) {
-    console.error("Failed to get MCP OAuth2 status:", error);
     throw error;
   }
 };