99 lines
3.6 KiB
Markdown
99 lines
3.6 KiB
Markdown
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# Story 14: New Session Cancellation
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## User Story
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**As a** User
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**I want** the backend to stop processing when I start a new session
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**So that** tools don't silently execute in the background and streaming doesn't leak into my new session
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## The Problem
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**Current Behavior (THE BUG):**
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1. User sends message → Backend starts streaming → About to execute a tool (e.g., `write_file`)
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2. User clicks "New Session" and confirms
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3. Frontend clears messages and UI state
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4. **Backend keeps running** → Tool executes → File gets written → Streaming continues
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5. **Streaming tokens appear in the new session**
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6. User has no idea these side effects occurred in the background
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**Why This Is Critical:**
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- Tool calls have real side effects (file writes, shell commands, searches)
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- These happen silently after user thinks they've started fresh
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- Streaming from old session leaks into new session
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- Can cause confusion, data corruption, or unexpected system state
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- User expects "New Session" to mean a clean slate
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## Acceptance Criteria
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- [ ] Clicking "New Session" and confirming cancels any in-flight backend request
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- [ ] Tool calls that haven't started yet are NOT executed
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- [ ] Streaming from old request does NOT appear in new session
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- [ ] Backend stops processing immediately when cancellation is triggered
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- [ ] New session starts with completely clean state
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- [ ] No silent side effects in background after new session starts
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## Out of Scope
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- Stop button during generation (that's Story 13)
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- Improving the confirmation dialog (already done in Story 20)
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- Rolling back already-executed tools (partial work stays)
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## Implementation Approach
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### Backend
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- Uses same `cancel_chat` command as Story 13
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- Same cancellation mechanism (tokio::select!, watch channel)
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### Frontend
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- Call `invoke("cancel_chat")` BEFORE clearing UI state in `clearSession()`
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- Wait for cancellation to complete before clearing messages
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- Ensure old streaming events don't arrive after clear
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## Testing Strategy
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1. **Test Tool Call Prevention:**
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- Send message that will use tools (e.g., "search all TypeScript files")
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- Click "New Session" while it's thinking
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- Confirm in dialog
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- Verify tool does NOT execute (check logs/filesystem)
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- Verify new session is clean
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2. **Test Streaming Leak Prevention:**
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- Send message requesting long response
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- While streaming, click "New Session" and confirm
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- Verify old streaming stops immediately
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- Verify NO tokens from old request appear in new session
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- Type new message and verify only new response appears
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3. **Test File Write Prevention:**
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- Ask to write a file: "Create test.txt with current timestamp"
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- Click "New Session" before tool executes
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- Check filesystem: test.txt should NOT exist
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- Verify no background file creation happens
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## Success Criteria
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**Before (BROKEN):**
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```
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User: "Search files and write results.txt"
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Backend: Starts streaming...
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User: *clicks New Session, confirms*
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Frontend: Clears UI ✓
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Backend: Still running... executes search... writes file... ✗
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Result: File written silently in background ✗
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Old streaming tokens appear in new session ✗
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```
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**After (FIXED):**
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```
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User: "Search files and write results.txt"
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Backend: Starts streaming...
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User: *clicks New Session, confirms*
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Frontend: Calls cancel_chat, waits, then clears UI ✓
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Backend: Receives cancellation, stops immediately ✓
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Backend: Tools NOT executed ✓
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Result: Clean new session, no background activity ✓
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```
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## Related Stories
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- Story 13: Stop Button (shares same backend cancellation mechanism)
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- Story 20: New Session confirmation dialog (UX for triggering this)
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- Story 18: Streaming Responses (must not leak between sessions)
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