Cursor/Grok Bot MCP OAuth: vercel.com/authorize returns 404 for mcp.vercel.com client

Summary

Connecting the Vercel Cursor plugin’s MCP connector (https://mcp.vercel.com) from Grok Bot / Cursor fails: the OAuth consent URL loads a 404 Not Found page on vercel.com/authorize while the user is already signed in.

Environment

• Client: Cursor Grok Bot (MCP connector install of the Vercel plugin)
• Plugin: Vercel (Cursor marketplace plugin bundling this repo + MCP)
• Account: signed into Vercel as andy@illumin8.ca
• Date: 2026-08-12

Steps to reproduce

1. Install the Vercel Cursor plugin / MCP connector.
2. Start connector authentication (connect card → OAuth).
3. Browser opens (or is redirected to) a https://vercel.com/authorize?... URL for MCP resource https://mcp.vercel.com/.
4. Page shows Vercel chrome with 404 / Not Found, “You are logged in as …”, and “Sign in as a different user”.
5. Retrying with force_reauth and a fresh connect card still lands on authorize 404.

Example authorize URL shape

(redacted challenge/state values; structure preserved)

https://vercel.com/authorize
  ?response_type=code
  &client_id=cl_eD921KDq5R4BhfW5pRKJ6KHgY7d0JycM
  &code_challenge=…
  &code_challenge_method=S256
  &redirect_uri=http://localhost:8787/callback
  &scope=openid
  &resource=https://mcp.vercel.com/
  &state=…

Expected

Consent screen for Vercel MCP, then redirect to the client callback so the connector becomes connected.

Actual

vercel.com/authorize itself 404s before consent. Connector remains needsAuth. Localhost callback never runs because authorization never completes.

Notes

• Other connectors (Notion, Google Calendar/Drive, GitHub) connected successfully in the same client.
• Switching Vercel accounts / teams was attempted; authorize page still 404’d.
• Workaround: abandoning MCP OAuth and using Vercel CLI + API token instead.
• Happy to provide screenshots or additional client logs if useful.

Ask

Is this a broken/allowlisted OAuth client for Cursor, a Vercel MCP authorize routing bug, or a known account/team gating issue? Guidance on the supported auth path for this plugin’s MCP connector would help.

The payload names no source file or test. Start by reproducing the MCP connector OAuth flow and inspecting the generated vercel.com/authorize URL; done means establishing whether the plugin or Vercel authorization endpoint owns the 404 and documenting the supported authentication path.