error linking N8N self hosted with Claude

[carlosmurillom]

What happened?

Authorization with the MCP server failed. You can check your credentials and permissions. If this persists, share this reference with support: "ofid_f57af2b2d5405529"

What did you expect to happen?

connect N8N self hosted

Steps to reproduce

when connecting to server it triggers an error. The authorization is stored on the N8N server as successful, but it triggers an eerror on Claude

Authorization with the MCP server failed. You can check your credentials and permissions. If this persists, share this reference with support: "ofid_f57af2b2d5405529"

Area

MCP Connector (adding/managing servers)

MCP Server (if applicable)

self hosted server

Error messages or logs

Authorization with the MCP server failed. You can check your credentials and permissions. If this persists, share this reference with support: "ofid_f57af2b2d5405529"

Additional context

No response

[JosiahParry]

Related #111

[charlesemarsh]

+1

[crondinini-ant]

Thanks for including the reference ID — I was able to pull the full trace for ofid_f57af2b2d5405529.

The OAuth handshake with your n8n server actually completed successfully. Your n8n instance issued us an access token and a refresh token, and we stored them — that's why n8n shows the authorization as successful on its side. The failure happened in the step immediately after: once we have a token, we send a test MCP initialize request to your server to confirm the connection actually works before marking the connector as ready. Your n8n server responded to that request with an HTTP 403 Forbidden, which we surface as "Authorization with the MCP server failed."

So the token is being issued fine, but something between us and your n8n MCP endpoint is rejecting the request with a 403. The most common cause we've seen for exactly this pattern — OAuth succeeds, then the first authenticated POST gets blocked — is Cloudflare's AI Crawl Control (or similar bot protection). If your n8n instance is behind Cloudflare, their edge may be flagging our request as bot traffic and returning the 403 before n8n ever sees it. Issue #49 has the details and confirmation from other users who hit the same thing with Cloudflare Tunnels.

If you're not behind Cloudflare, a few other things worth checking on the n8n side:

• The MCP endpoint path in your connector URL (/mcp-server/http or similar) is the one that actually serves MCP, and it's wired to accept tokens from the OAuth server you configured. In some n8n setups the OAuth provider and the MCP route aren't linked by default.
• If your n8n instance is behind a different reverse proxy or ingress that does its own auth, it may be intercepting the request and returning the 403 before n8n ever sees it.
• The token scope or audience matches what the MCP endpoint expects — n8n's OAuth config sometimes issues tokens with a narrower scope than the MCP handler requires.

[crondinini-ant]

Closing the issue for easier tracking of open issues without a reply, @carlosmurillom please reopen if the issue persists.

[staticgroup]

we are experiancing this issue too