The dashboard's listen host is the first gate. Default 127.0.0.1. To expose remotely you need 0.0.0.0.
3. Loopback bind + Tailscale Serve = "Invalid Host header" 400. Diagnosed by reading the dashboard code: the middleware's _is_accepted_host only allows loopback aliases when bound to loopback. The browser shows a generic failure; the server-side curl with the wrong Host also fails; but curl -H "Host: 127.0.0.1:9119" succeeds. Lesson: when Tailscale Serve is involved, always check the Host header preservation chain — Serve preserves it, the dashboard's middleware checks it.
The basic auth login page in hermes_cli/dashboard_auth/login_page.py posts to fetch('/auth/password-login', ...) — root-relative. When the dashboard is reachable at a Tailscale-Serve path prefix like /hermes, the form posts to <origin>/auth/password-login (NOT <origin>/hermes/auth/password-login). The browser falls into the generic "Sign-in failed" branch even with correct credentials. Direct IP URLs work because there's no path prefix.
1. "Sign-in failed" with correct credentials. Diagnosed as server-side, not credential-side. The form was posting to the wrong URL because of the Serve path prefix. Server-side curl login worked; browser-side login failed. Lesson: when the browser shows a failure but a parallel curl succeeds, the bug is in the form (or whatever HTML/JS layer is between the user and the API), not in the API itself.
Host: <tailnet-host> header. The loopback bind's middleware rejects it. **These two are architectural…0.0.0.0 + register an auth provider./api/status shows auth_required: True but every login returns 401. Diagnosed as stale config in the running process. `launchc…
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