OAuth "Client is invalid or unknown" error when connecting via Claude's built-in MCP connector

[IDntKnwWhtImDoin]

Description

When using Claude's built-in "Connect" button to connect PagerDuty as an MCP server,
the OAuth flow fails with a "Bad request – Client is invalid or unknown" error from
app.pagerduty.com.

Steps to Reproduce

1. Open Claude desktop app (Cowork mode)
2. Navigate to MCP connectors and click "Connect" next to PagerDuty
3. Browser is redirected to PagerDuty OAuth authorize endpoint
4. PagerDuty returns: "The request could not be processed. Client is invalid or unknown."

OAuth Request Details

• redirect_uri: https://claude.ai/api/mcp/auth_callback
• resource: https://mcp.pagerduty.com/mcp

Expected Behavior

OAuth flow completes and Claude connects to the native PagerDuty MCP server.

Workaround

Using a PagerDuty API token with direct MCP server config works fine.
The issue is specific to the OAuth path initiated by Claude's connector.

Notes

This may require coordination with Anthropic, as the unrecognized client_id
appears to be on their side. Flagging here so both teams are aware.

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[JaneJeon]

This is rather obtuse, but I managed to get around it by manually creating an 'app' with OAuth tokens (classic, user-scoped) and just copy-pasting the credentials of that app into the OAuth Client ID/Secret fields during the installation so that Claude can connect on behalf of the user (me).

Hope it helps!