Push notifications: agent finished, needs input, terminal bell

[karngyan]

Why

flue's mobile story currently stops at "open the tab and look". The loop people actually want is: agent runs on the desk, phone buzzes when it finishes or blocks on a prompt, one tap lands you in the session.

Every serious competitor with a native or installable client ships this: Cursor (push on finish, needs input, ready for review, plus Live Activities), Claude Code Remote Control ("push when actions required"), Codex Remote (opening a task straight from the notification), Happy Coder (push on permission requests, errors and completion). Amp has no push at all and closes its async loop through Slack DMs, which is widely seen as its weakest point.

Rough scope

• Web Push through the service worker we already ship. No new client surface.
• The relay Worker stores push subscriptions per paired device and forwards pings. The payload stays content free (roughly "a session on studio needs you"), so FCM and Apple's push relay learn nothing. The tap opens the session and the real data flows over the existing end-to-end channel.
• Triggers to start with: terminal bell, agent turn ended, agent waiting on input. Detection of "waiting on input" is its own issue (needs-you queue) and this one can start with bell plus turn-ended.
• Per-session and per-device mute controls.

Notes

• On iOS, web push requires the PWA installed to the home screen. Worth saying loudly in docs.
• VAPID keys can live beside the relay secret. Push stays self hosted, flue.sh remains outside the data path.
• Pairs with the needs-you queue issue: that one is the pull side, this one is the push side.