[Bug] Question/approval cards missing on mobile until page refresh — WebSocket silently suspended, no heartbeat / no visibilitychange reconnect

[nevergow]

Environment

• dsh v0.1.0-rc.5 (developer preview, source build, master @ 47f9438)
• Web UI over HTTPS via reverse proxy, iPhone (iOS 26.5.2) Edge/Safari

Bug

On mobile browsers, interactive cards (agent questions / approvals) sometimes never appear while the page stays open. They only show up after a manual page refresh. Happens intermittently — typically after the phone locks, the tab goes to background, or the network switches (WiFi <-> cellular).

What I traced in source

Server side is correct: when the agent asks a question it is stored in pendingQuestions (api-proxy.ts ~line 1388) and pushed as a question/requested frame over the mux WebSocket. On (re)connect the server replays all pending questions (api-proxy.ts ~line 3436) — which is exactly why a refresh makes the card appear.

Client side is fragile (packages/client/connection/src/web-api-client.ts + packages/client/runtime/src/client/sessions/manager.ts):

• Reconnect is only triggered by the WebSocket close event (handleClose -> enqueue end -> reconnect loop with backoff).
• There is no heartbeat / ping to detect a zombie connection.
• There is no visibilitychange listener to force a reconnect when the tab returns to the foreground.

On mobile, browsers silently suspend WebSockets when the screen locks / the tab is backgrounded / the network changes — often without firing close. The client believes the connection is alive, so every subsequent question/requested frame is lost and no card is rendered. A manual refresh forces a fresh connection, the server replays pending questions, and the card appears.

Expected

• Heartbeat (ping/pong) so a dead connection is detected and reconnected even without a close event.
• visibilitychange (and online/offline) handlers that proactively reconnect when the tab becomes visible again — standard practice for mobile web apps.

Impact

Remote/mobile users miss agent questions entirely (approval prompts, clarification asks), which can stall a session without the user knowing.