Behind Cloudflare Zero Trust or Pangolin, cross-origin auth redirects on
/api/* calls surface as CORS errors (error.response === undefined) that
the existing 401 interceptor never catches, leaving the PWA stuck with
network-error toasts instead of re-authenticating.
New connectivity module probes /api/health every 30s using fetch with
cache:no-store and inspects Content-Type to reliably detect whether the
server is reachable vs intercepted by an upstream proxy.
axios interceptor changes:
- On !error.response + navigator.onLine: run probeNow(); if the health
probe also fails (proxy is intercepting all requests), trigger a guarded
window.location.reload() so the edge proxy can intercept the top-level
navigation and run its auth flow (covers CF Access and Pangolin 302 mode)
- On error.response status 401 with text/html body: same reload path,
covering Pangolin header-auth extended compatibility mode which returns
401+HTML instead of a 302 redirect. TREK own 401s are always JSON so
there is no collision with the existing AUTH_REQUIRED branch.
- sessionStorage flag prevents reload loops; cleared on any successful
response so the guard resets after re-auth.
/api/health excluded from SW NetworkFirst cache (vite.config.js regex)
and Cache-Control: no-store added server-side so probes always hit the
network and cannot be served stale from the 24h api-data cache.
LoginPage caches last-known appConfig in localStorage so the SSO button
renders in OIDC+UN/PW dual mode even when the config fetch is intercepted
by the proxy. Auto-redirect to IdP skipped when config comes from cache
to avoid redirect loops while the proxy is challenging.
Fixes discussion #836.
jubnl