Enables exposing the supervisor MCP via Tailscale Funnel for claude.ai
custom-connector tests. Auth is opt-in: empty SUPERVISOR_MCP_TOKEN
preserves the existing unauthenticated behavior for tailnet-internal
callers and local dev.
When the token is set, every request must carry
"Authorization: Bearer <token>" or it is rejected with HTTP 401 and a
JSON-RPC -32001 error. Comparison uses crypto/subtle.ConstantTimeCompare;
the token value and the supplied header are never logged.
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
