CCR: MCP connector OAuth re-authorization returns 'Server Turned Down' on api.anthropic.com/authorize

Bug Description

When a Cloud Code Routine (CCR) requires OAuth re-authorization for an MCP connector (e.g. Fathom), the routine surfaces an OAuth URL in the format:

https://api.anthropic.com/authorize?connector_uuid=...&code_challenge=...&code_challenge_method=S256

Opening this URL in a browser returns a "Server Turned Down" page, making it impossible to re-authorize the connector.

Steps to Reproduce

1. Create a CCR routine that uses an OAuth-based MCP connector (e.g. Fathom at https://api.fathom.ai/mcp)
2. Let the OAuth token expire, or trigger re-authorization by re-connecting the connector via the claude.ai UI
3. Run the CCR routine — it correctly detects that re-auth is needed and surfaces the OAuth URL
4. Open https://api.anthropic.com/authorize?connector_uuid=...&code_challenge=...&code_challenge_method=S256 in a browser
5. See "Server Turned Down" page — authorization cannot complete

Expected Behavior

The OAuth URL should open a valid authorization page allowing the user to re-authorize the MCP connector for use in CCR routines.

Actual Behavior

"Server Turned Down" — the https://api.anthropic.com/authorize endpoint appears to be deprecated or shut down.

Impact

All CCR routines using OAuth-based MCP connectors are permanently broken once the token expires. The permitted_tools mechanism in mcp_connections is not the issue — the underlying token is invalid and the renewal path does not work.

Note: Re-authorizing the connector via the claude.ai UI (Settings → Connectors) also resets permitted_tools to [], requiring an immediate re-patch via the RemoteTrigger API — a separate but related pain point.

Workaround

Strip OAuth-dependent MCP connectors from CCR routines entirely and handle that work locally instead. The CCR then sends a nudge message only.

Environment

• Claude Code CCR (Cloud Code Routines / Remote Triggers)
• Fathom MCP connector (https://api.fathom.ai/mcp)
• connector_uuid in use: 3ac42bf3-04fc-4711-ab36-1ac6de042da5
• Date observed: 2026-05-21
• Platform: macOS (darwin 25.4.0)