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OAuth issue incorrect for MCP

  • September 20, 2026
  • 0 replies
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heaths
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I appreciate that you tested this the Strava MCP with Claude so I imagine it works, but they aren’t the only agent out there. I’m getting an immediate HTTP 403 with Copilot CLI, and when having it introspect why, it reports:

Root cause: it’s not failing because your  strava-mcp  entry is missing or malformed; Copilot is rejecting Strava’s OAuth metadata as invalid.

Your config is a normal remote MCP entry in  ~/.copilot/mcp-config.json :

"strava-mcp": {
  "type": "http",
  "url": "https://mcp.strava.com/mcp"
}

But the Copilot log shows the auth flow dies here:

 OAuth authentication failed for strava-mcp: MCPOAuthError: Incompatible authorization server: authorization server advertised an issuer that does not match the URL its metadata was discovered from (RFC 8414 §3.3); refusing to connect 

What’s happening is:

1.  strava-mcp  challenges the client with an OAuth protected-resource URL on  www.strava.com .
2. That metadata points to  https://www.strava.com/mcp-issuer  as the authorization server.
3. The authorization-server metadata served from that path reports  "issuer":"https://www.strava.com"  instead of the discovered issuer URL/path.
4. Copilot CLI rejects that mismatch on purpose, so authentication never completes.

Bottom line: this is a server-side OAuth metadata bug/incompatibility in Strava’s MCP endpoint, not a bad local Copilot config. The fix has to be on Strava’s side: their protected-resource / authorization-server metadata needs to advertise a consistent issuer.

 

It would be great if the issue followed the OAuth spec so any agent—even ones people wrote themselves (seems to be the thing these days)—could use it.