During metadata fetching, try with the MCP header, then without, then return undefined if both fail

Author: jerome3o-anthropic

src/client/auth.ts

@@ -163,11 +163,20 @@ export async function discoverOAuthMetadata(
   opts?: { protocolVersion?: string },
 ): Promise<OAuthMetadata | undefined> {
   const url = new URL("/.well-known/oauth-authorization-server", serverUrl);
-  const response = await fetch(url, {
-    headers: {
-      "MCP-Protocol-Version": opts?.protocolVersion ?? LATEST_PROTOCOL_VERSION
+  let response: Response;
+  try {
+    response = await fetch(url, {
+      headers: {
+        "MCP-Protocol-Version": opts?.protocolVersion ?? LATEST_PROTOCOL_VERSION
+      }
+    });
+  } catch {
+    try {
+      response = await fetch(url);
+    } catch {
+      return undefined;
     }
-  });
+  }
 
   if (response.status === 404) {
     return undefined;