Metabase MCP custom connector — "Authorization with the MCP server failed" (ofid_9eab547b7d0e4d01) — matches issue #208

Preflight Checklist

• [x] I have searched existing issues and this hasn't been reported yet
• [x] This is a single bug report (please file separate reports for different bugs)
• [x] I am using the latest version of Claude Code

What's Wrong?

Hi team,
I'm hitting the same Metabase MCP connector failure tracked in issue #208 and would like to add a data point + request an update on the fix.
Error reference: ofid_9eab547b7d0e4d01
Setup:

Metabase version: 0.60.4.1 (self-hosted)
Connection method: Custom connector URL entered manually in Claude.ai
Where it fails: After clicking Connect, immediately returns the authorization failure banner — never reaches a Metabase consent screen
Claude plan: [fill in — Pro / Team / Enterprise]
Browser: [fill in — e.g. Chrome 131 on Windows 11]

Metabase-side configuration verified:

Site URL correctly set to https://metabasepublicurl (matches public hostname, HTTPS, no trailing slash)
MCP server feature enabled under Admin → Settings
Claude enabled in the Supported MCP clients allowlist
GET Public URL for metabase in a browser returns the expected JSON-RPC response: {"jsonrpc":"2.0","id":null,"error":{"code":-32600,"message":"Missing Mcp-Session-Id header"}} — confirming the endpoint is reachable and speaking the protocol correctly

What Should Happen?

Using claude mcp add --transport http metabase metabasepublicurl, the OAuth flow completes, tools are discovered, and queries against my Metabase databases execute successfully. This rules out Metabase-side config, network reachability, OAuth provider configuration, and TLS as the cause — the only variable is the Claude.ai custom connector vs Claude Code client.
This is the same pattern reported in #208 (and structurally similar to the Salesforce Hosted MCP issues #184 and #280 that Anthropic support has confirmed as an Anthropic-side issue).
Ask: Any ETA on a fix, or a workaround to use the Metabase MCP from Claude.ai web/desktop rather than only from Claude Code?

Error Messages/Logs

ofid_9eab547b7d0e4d01

Steps to Reproduce

Add MCP to Claude Desktop. Works fine in claude code

Claude Model

Not sure / Multiple models

Is this a regression?

No, this never worked

Last Working Version

_No response_

Claude Code Version

2.1.145

Platform

Anthropic API

Operating System

macOS

Terminal/Shell

Terminal.app (macOS)

Additional Information

_No response_