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

[andydoucet]

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.