draft: Stop button — open-agents-style (instant aiStop + void POST, no isStopping) [alt to #1770]

[sweetmantech]

Draft / alternative to #1770 — not for parallel merge. Same feature (wire the Stop button to cancel the durable workflow run), implemented the open-agents way. Open this side-by-side with #1770 to compare.

What's different vs #1770

#1770 awaits the backend POST /api/chat/{chatId}/stop and deliberately does not call the AI SDK stop() for workflow chats, so it needs an isStopping pending-state threaded through hook → provider → ChatInput to give button feedback while the stream keeps running ~1–2s.

This version matches open-agents (use-session-chat-runtime.ts):

• stop() calls the AI SDK aiStop() immediately for all chats → the stream stops on screen instantly.
• For workflow chats it also void-fires POST /api/chat/{chatId}/stop (best-effort) to cancel the durable run server-side.
• Removes the entire isStopping path — the useMutation, the provider field, and the ChatInput wiring.

Net −20 lines (4 files): simpler, and the Stop button feels instant instead of lagging ~1–2s.

Why this is safe

Reload-consistency was the stated reason #1770 avoided aiStop(). That's already handled server-side by api#590: it persists the assistant message per step and finalizeAbortedAssistantMessage closes open tool-calls + re-persists on abort. So the DB shows the complete, tool-closed turn on reload regardless of local abort.

Trade-off to decide

• feat(chat): wire stop button to POST /api/chat/{chatId}/stop #1770: trailing in-flight chunks render in the current view before the stream stops (no reload needed); costs the isStopping machinery + a ~1–2s visible lag.
• This PR: instant on-screen stop; a couple of trailing chunks may not appear in the current view but are persisted (visible on reload).

If "trailing chunks must show without reload" isn't required, this is the better default.

Tests

• stopChatWorkflow lib test passes; ESLint clean; no isStopping references remain.

🤖 Generated with Claude Code

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Summary by cubic

Make the Stop button instant and cancel workflow runs server-side. We now call aiStop() immediately and fire a best-effort POST /api/chat/{chatId}/stop; removed isStopping and improved cancelled tool UI.

• New Features

  • Stop now calls aiStop() for all chats and asynchronously POSTs /api/chat/{chatId}/stop for workflow chats (fire-and-forget).
  • Added useStopChatWorkflow and stopChatWorkflow; useVercelChat now uses them.

• Bug Fixes

  • Cancelled or denied tool-calls render with a clear badge instead of a spinner.
  • Tests added for stopChatWorkflow (auth header, URL encoding, no-throw behavior).

^{Written for commit f0b3d7a. Summary will update on new commits.}

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Project	Deployment	Actions	Updated (UTC)
chat	Ready	Preview	Jun 8, 2026 5:24pm