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Dave e1fb0e3d19 Story 13: Implement Stop button with backend cancellation

- Add tokio watch channel for cancellation signaling
- Implement cancel_chat command
- Add cancellation checks in streaming loop and before tool execution
- Stop button (■) replaces Send button (↑) during generation
- Preserve partial streaming content when cancelled
- Clean UX: no error messages on cancellation
- Backend properly stops streaming and prevents tool execution

Closes Story 13

2025-12-27 18:32:15 +00:00

2.9 KiB

Raw Blame History

Story 13: Stop Button

User Story

As a User I want a Stop button to cancel the model's response while it's generating So that I can immediately stop long-running or unwanted responses without waiting for completion

The Problem

Current Behavior:

User sends message → Model starts generating
User realizes they don't want the response (wrong question, too long, etc.)
No way to stop it - must wait for completion
Tool calls will execute even if user wants to cancel

Why This Matters:

Long responses waste time
Tool calls have side effects (file writes, searches, shell commands)
User has no control once generation starts
Standard UX pattern in ChatGPT, Claude, etc.

Acceptance Criteria

Stop button (⬛) appears in place of Send button (↑) while model is generating
Clicking Stop immediately cancels the backend request
Tool calls that haven't started yet are NOT executed after cancellation
Streaming stops immediately
Partial response generated before stopping remains visible in chat
Stop button becomes Send button again after cancellation
User can immediately send a new message after stopping
Input field remains enabled during generation

Out of Scope

Escape key shortcut (can add later)
Confirmation dialog (immediate action is better UX)
Undo/redo functionality
New Session flow (that's Story 14)

Implementation Approach

Backend

Add cancel_chat command callable from frontend
Use tokio::select! to race chat execution vs cancellation signal
Check cancellation before executing each tool
Return early when cancelled (not an error - expected behavior)

Frontend

Replace Send button with Stop button when loading is true
On Stop click: call invoke("cancel_chat") and set loading = false
Keep input enabled during generation
Visual: Make Stop button clearly distinct (⬛ or "Stop" text)

Testing Strategy

Test Stop During Streaming:
- Send message requesting long response
- Click Stop while streaming
- Verify streaming stops immediately
- Verify partial response remains visible
- Verify can send new message
Test Stop Before Tool Execution:
- Send message that will use tools
- Click Stop while "thinking" (before tool executes)
- Verify tool does NOT execute (check logs/filesystem)
Test Stop During Tool Execution:
- Send message with multiple tool calls
- Click Stop after first tool executes
- Verify remaining tools do NOT execute

Success Criteria

Before:

User sends message → No way to stop → Must wait for completion → Frustrating UX

After:

User sends message → Stop button appears → User clicks Stop → Generation cancels immediately → Partial response stays → Can send new message

Story 14: New Session Cancellation (same backend mechanism, different trigger)
Story 18: Streaming Responses (Stop must work with streaming)

2.9 KiB Raw Blame History