diff --git a/extensions/general/mcp-server/index.ts b/extensions/general/mcp-server/index.ts
index f42d2816..542be1e8 100644
--- a/extensions/general/mcp-server/index.ts
+++ b/extensions/general/mcp-server/index.ts
@@ -36,14 +36,18 @@ export const mcpServerExtension: Extension = {
       method: 'GET',
       path: '/mcp',
       skipAuth: true,
+      // This server is stateless and offers no server-initiated SSE stream, so
+      // the Streamable HTTP spec requires 405 Method Not Allowed here. Returning
+      // 401 (as we previously did) makes spec-compliant clients (Claude
+      // connector, Claude Desktop, Cursor) treat the SSE GET as an auth failure
+      // and retry-loop — refresh token → re-open GET → 401 → … — which storms
+      // the endpoint and churns OAuth key rotation. OAuth discovery is
+      // bootstrapped on the POST 401 (WWW-Authenticate), not here.
       handler: async (request: Request) => {
         if (isForbiddenOrigin(request)) return forbiddenOriginResponse()
-        const appUrl = process.env.NEXT_PUBLIC_APP_URL || 'http://localhost:3000'
-        return new Response('Authorization required', {
-          status: 401,
-          headers: {
-            'WWW-Authenticate': `Bearer resource_metadata="${appUrl}/.well-known/oauth-protected-resource"`,
-          },
+        return new Response('Method Not Allowed', {
+          status: 405,
+          headers: { Allow: 'POST, DELETE' },
         })
       },
     },