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Claude Code Issues / #56641

[BUG] Hosted MCP endpoints gmail.mcp.claude.com / gcal.mcp.claude.com return HTTP 404 for all clients

Resolved 💬 3 comments Opened May 6, 2026 by tomra-hub Closed May 9, 2026

Bug description

The Anthropic-hosted MCP connectors for Gmail and Google Calendar return HTTP 404 from Google Frontend on every path — base /mcp, OAuth discovery (/.well-known/oauth-authorization-server, /.well-known/oauth-protected-resource), and Dynamic Client Registration (/register). This blocks any first-time OAuth flow, regardless of network or TLS state.

Reproduced from multiple macOS clients both inside and outside a corporate MITM network, so this is the service itself, not a client-side or proxy problem.

Environment

  • Claude Code v2.1.129 (and v2.1.126 earlier)
  • macOS 15
  • Confirmed 2026-05-04 and again 2026-05-06
  • Behavior identical on corp network (monday.com MITM) and clean home network (verified by a colleague off-network)

What fails

Triggering /mcp authenticate gmail (or gcal) fails with:

SDK auth failed: HTTP 404: Invalid OAuth error response: SyntaxError: JSON Parse error: Unrecognized token '<'. Raw body:
<html>...<h2>The requested URL `/register` was not found on this server.</h2>...

This happens after #55760's TLS issue is worked around — the OAuth client reaches the endpoint successfully, but the endpoint returns 404.

Reproduction

$ curl -sI https://gmail.mcp.claude.com/mcp
HTTP/2 404
server: Google Frontend
content-type: text/html; charset=UTF-8

$ curl -sI https://gcal.mcp.claude.com/mcp
HTTP/2 404
server: Google Frontend

$ curl -s -o /dev/null -w "%{http_code}\n" https://gmail.mcp.claude.com/.well-known/oauth-authorization-server
404

$ curl -s -o /dev/null -w "%{http_code}\n" https://gmail.mcp.claude.com/.well-known/oauth-protected-resource
404

$ dig gmail.mcp.claude.com +short
ghs.googlehosted.com.

The Server: Google Frontend header + ghs.googlehosted.com CNAME suggests the service is hosted on Google Cloud App Engine and isn't routing — either a deployment regression, a deprovisioned service, or a DNS/routing mismatch.

What works (for contrast)

  • Other Anthropic endpoints (api.anthropic.com, the control-plane reachable via claude mcp list) return expected responses.
  • Same OAuth client flow works fine against locally-hosted MCP servers.

Impact

Gmail and Google Calendar MCP connectors are effectively unavailable for first-time onboarding. Users who already had tokens from before the regression still work (the refresh path is healthy), so this is a silent outage — visible only to new users.

Affects an estimated several hundred users at monday.com R&D currently trying to onboard gmail/gcal MCP, plus anyone else attempting a fresh install against the hosted connector.

Related

  • #55760 — TLS bootstrap bug; same hosted connectors, different layer. Fixing that one doesn't fix this one.

Asks

  1. Confirm whether the hosted endpoints moved, were deprecated, or are down.
  2. If moved: publish the new URL.
  3. If down: ETA for restoration.
  4. If deprecated: publish the self-hosted migration path.

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