No "Stop / interrupt generation" control while the agent is streaming

[aasis21]

Problem

While a turn streams in, the composer (mobile/src/components/Composer.tsx) only exposes a Send button. There is no way to stop/interrupt a running generation or a runaway autopilot loop from the phone.

Why it matters

"Stop generating" is table stakes in every comparable product (ChatGPT shows a red ■ Stop, Claude shows "Stop generating", VS Code Copilot Chat turns Send into a Stop/Send dropdown). For a coding agent companion it is also a safety control — the phone is exactly where you want a kill switch when you can't reach the keyboard.

Suggested fix

• Send a cancel/interrupt control message over the relay and have the extension call the SDK's interrupt path.
• While status === 'live' and a turn is active, render the Send button as a Stop button.

References

• ChatGPT / Claude streaming Stop control.
• VS Code Copilot Chat "Stop and Send": https://code.visualstudio.com/docs/chat/chat-overview

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Filed from a UI research sweep of the Helm mobile app (landing + live demo session) using Playwright + full source review, cross-referenced against Claude, ChatGPT, GitHub Copilot Chat, and Codex/Claude Code UIs.

[aasis21]

Fixed in ef32bc7 (shipped to prod). Added a phone Stop/interrupt: a new control.interrupt message; the extension's applyInterrupt() calls the SDK turn-abort RPC (session.rpc.abort, reason 'remote_command') and posts a stop notice to the phone; the composer swaps Send→Stop while a tool is mid-run (agentBusy). Covered by a new relay test ('relays a control.interrupt to the SDK turn-abort and notifies the phone').

[aasis21]

Follow-up fix shipped in 1cb1c62 (build live on https://usehelm.netlify.app).

Refinement: Stop now tracks the whole in-flight turn, not just running tools.

The initial fix gated the Stop button on a running tool. But abort cancels the
entire turn — so while the agent was streaming text/reasoning (no tool yet),
Stop never appeared even though that phase is fully abortable.

The extension now forwards a turn-level activity signal off the SDK lifecycle:

• assistant.message_start -> activity(busy=true) — turn begins (text/reasoning)
• assistant.idle -> activity(busy=false) — agent loop idle = turn over
• tool.execution_start -> activity(busy=true) — fallback for tool-first turns

The phone derives agentBusy = timeline.busy || <a tool is running>, so Stop is
visible for the full abortable window and clears the moment the turn ends. busy
is transient (reset on reconnect / session start+end). New ACTIVITY
(stream.activity) protocol kind + activity() factory in shared/; covered by
shared factory/routing tests + a relay lifecycle-forwarding test (57 tests green).