Opening Codeman with nothing reachable (phone off the tailnet, VPN down,
server stopped) rendered a normal-looking UI: the service worker serves the
cached app shell, every /api call fails, and the only tell was an 8px red dot
in the header corner. On a phone that reads as "there are no sessions".
Two surfaces, chosen by whether there is anything worth looking at:
- Full-screen overlay while no server state has loaded this page load. It
names the host, lists the three things to check (network, VPN/Tailscale,
server), counts down to the next retry, and offers "Retry now" plus
"Show cached view" to demote itself to the banner.
- Non-blocking banner once state HAS loaded, so a mid-session drop leaves the
terminal scrollback readable.
A 2.5s grace keeps a COM deploy (SSE is back in ~200ms) from flashing the
banner every release; navigator.onLine === false skips the grace, since the
device saying "no network" is never a blip. Retry re-arms the terminal
WebSocket as well as SSE: planWsReconnect can give up outright, and the SSE
backoff caps at 30s, so waiting it out is not always an option.
The decision is pure (computeConnectionLossUi in constants.js, unit-tested in
a node VM like the WS reconnect policy); app.js only writes the DOM.
