For first-party MCP (Model Context Protocol, the system Claude Code uses to talk to external tool servers) servers, Claude Code previously had a fallback that could automatically re-authenticate using a consent-gated callback for any first-party-looking server. Now that fallback only fires when the server's URL is https, first-party, and its path starts with /v1/design/. A separate check for what counts as a matching first-party URL was also widened to include a new /v1/claude/test/ path, but the actual token-fallback behavior still only applies to /v1/design/ URLs.
This narrows automatic authentication so that other first-party MCP servers no longer silently pick up a stored design-related credential; only design servers get that fallback now.
Gate state
No sentence about tengu_mcp_first_party_auto_auth since nothing has been read about it yet.