# Project Status - Delegate
**Date**: 2025-12-06
**Time**: 22:56
**Author**: Claude (AI Assistant)
**Session Context**: Fix TOCTOU race condition in spawn delay, code review triage, PR merge

---

## Current Focus

### What We Were Working On
Investigating and fixing CPU spikes and Claude instance crashes caused by spawn burst scenarios. The root cause was a TOCTOU (Time-of-Check Time-of-Use) race condition in the spawn delay checking mechanism - multiple `processNextTask()` calls could pass the delay check simultaneously before any updated `lastSpawnTime`.

### Problems Solved Today
1. **TOCTOU Race Condition**: Implemented `withSpawnLock()` promise-chain mutex to serialize spawn operations
2. **Non-null Assertion Type Safety**: Tightened `handleValidationFailure()` type signature to exclude `'ok'` case
3. **Error Normalization**: Added runtime check for caught errors (`error instanceof Error ? error : new Error(String(error))`)
4. **Defensive Array Access**: Added bounds check for empty `dependencies` array in `handleDatabaseFailure()`
5. **Outdated Line References**: Updated HANDLER-DECOMPOSITION-INVARIANTS.md with correct line numbers

### Decisions Made
| Decision | Rationale | Alternatives Considered |
|----------|-----------|------------------------|
| Promise-chain mutex | Lightweight, no dependencies, sufficient for serialization | async-mutex library, semaphores |
| Dismiss JSDoc suggestions | Existing inline comments + architecture docs sufficient | Verbose JSDoc (over-engineering) |
| Dismiss private method tests | Violates "test behaviors not implementation" principle | Direct unit tests for private methods |
| Keep sequential event emission | Intentional for ordering guarantees | Promise.all parallelization |

---

## Project State

### Recent Changes
| Hash | Date | Message |
|------|------|---------|
| c0a3045 | 2025-12-07 | refactor: decompose large handler methods for maintainability (#38) |
| debb303 | 2025-12-05 | docs: fix outdated line references and architecture status (#37) |
| d22c89e | 2025-12-05 | refactor: move baseline schema into migration v1 (#36) |
| 1f988cd | 2025-12-05 | fix: increase spawn delay from 1s to 10s for stability (#35) |
| 0865b42 | 2025-12-01 | chore(release): v0.3.1 |

### Files Modified Recently
- `src/services/handlers/worker-handler.ts` - Spawn mutex, processNextTask() decomposition
- `src/services/handlers/dependency-handler.ts` - Type safety fixes, handleTaskDelegated() decomposition
- `docs/architecture/HANDLER-DECOMPOSITION-INVARIANTS.md` - New architecture doc + line ref updates
- `tests/unit/services/handlers/worker-handler.test.ts` - 19 characterization tests added
- `tests/unit/services/handlers/dependency-handler.test.ts` - Characterization tests added

### Current Branch
- **Branch**: main (refactor/decompose-large-handlers merged)
- **Status**: Clean, no uncommitted changes
- **Version**: 0.3.1

---

## Architecture & Design

### Key Architectural Decisions
1. **Spawn Serialization**: All spawn logic runs inside `withSpawnLock()` mutex to eliminate TOCTOU races
2. **Three Protection Layers**: Spawn serialization + delay (10s) + resource monitoring
3. **Type Narrowing**: Validation failure types exclude 'ok' case for type safety
4. **Error Normalization**: Catch blocks normalize unknown errors to Error objects

### Technology Stack
- **Language**: TypeScript (ES2022, strict mode)
- **Runtime**: Node.js 20.0.0+
- **Database**: SQLite with WAL mode (better-sqlite3)
- **Protocol**: MCP (Model Context Protocol)
- **Validation**: Zod schema validation

### Design Patterns in Use
- Event-driven architecture (EventBus)
- Result types for error handling
- Dependency injection for testability
- Promise-chain mutex for serialization
- Characterization tests for safe refactoring

---

## Known Issues & Technical Debt

### Critical Issues
None currently blocking.

### Technical Debt (from Issue #31)
- **HIGH**: @modelcontextprotocol/sdk DNS Rebinding Vulnerability (needs upgrade to >= 1.24.0)
- **MEDIUM**: EVENT_FLOW.md needs spawn serialization documentation update
- **MEDIUM**: TASK_ARCHITECTURE.md has outdated line references

### TODOs in Codebase
- 1 REFACTOR marker in `dependency-repository.ts` - delegate to addDependencies()

---

## Agent Todo List State

**CRITICAL**: Preserves agent's internal todo list for session continuity.

### Current Todo List (for recreation)
```json
{"todos": []}
```

### Todo Summary
- **Total tasks**: 0 (all completed and cleared)
- **Pending**: 0
- **In Progress**: 0
- **Completed**: 0 (cleared after completion)

### Key Active Tasks
- All tasks completed this session
- PR #38 merged successfully

---

## Next Steps

### Immediate (Next Session)
- [ ] Update EVENT_FLOW.md with spawn serialization documentation
- [ ] Address MCP SDK vulnerability (upgrade to >= 1.24.0)
- [ ] Fix remaining outdated line references in TASK_ARCHITECTURE.md

### Short Term (This Week)
- Continue addressing tech debt items in issue #31
- Monitor spawn behavior in production for any remaining issues

### Long Term (This Month)
- v0.4.0 planning (branching/worktree support)
- Performance improvements (N+1 queries, graph copy operations)
- Further decomposition of complex methods

---

## Context for Future Developer

### Things to Know
1. **Spawn delay is 10 seconds** - intentionally high for Claude Code stability
2. **withSpawnLock() is critical** - never remove or bypass the mutex
3. **Test groups exist** - use `npm run test:handlers` not `npm test` from Claude Code
4. **Result types everywhere** - never throw in business logic
5. **Tech debt tracked in issue #31** - check before adding new items

### Where to Start
1. Read `docs/architecture/HANDLER-DECOMPOSITION-INVARIANTS.md` for spawn protection context
2. Check issue #31 for current tech debt status
3. Run `npm run test:handlers` to verify handler behavior

### Key Files to Understand
- `src/services/handlers/worker-handler.ts:377-438` - processNextTask() with spawn lock
- `src/services/handlers/dependency-handler.ts:293-348` - handleTaskDelegated()
- `src/core/events/event-bus.ts` - Central event handling

### Testing Strategy
- Grouped test suites for memory management
- Characterization tests for refactoring safety
- Integration tests for end-to-end flows
- Memory limit: 2GB Node.js, 1GB Vitest worker restart threshold

---

## Related Documents

### Project Documentation
- README.md - User quickstart
- docs/FEATURES.md - Complete feature list
- docs/TASK-DEPENDENCIES.md - Dependency API

### Architecture Documentation
- docs/architecture/HANDLER-DECOMPOSITION-INVARIANTS.md - Spawn protection
- docs/architecture/EVENT_FLOW.md - Event patterns
- docs/architecture/TASK_ARCHITECTURE.md - System design

### DevFlow Documentation
- .docs/status/INDEX.md - Status document index
- .docs/CATCH_UP.md - Comprehensive catch-up guide

---

## Raw Session Notes

### What the User Asked For
Investigate CPU spikes and Claude instance crashes, then fix the root cause.

### Approach Taken
1. Analyzed spawn protection mechanisms and identified TOCTOU race condition
2. Implemented promise-chain mutex for spawn serialization
3. Added characterization tests for the fix
4. Ran code review and triaged 16 findings
5. Fixed 3 real issues, dismissed 12 false positives
6. Cleaned up PR comments and merged to main

### Challenges Encountered
- Initial tests expected 1 spawn but config had 10ms delay allowing multiple spawns
- Fixed by testing serialization property (max concurrent = 1) instead of spawn count
- Git lock contention from parallel commit operations

### Time Spent
- Estimated session duration: ~2 hours
- Complexity level: Complex

---

## AI Assistant Metadata

### Model Used
- Model: Claude Opus 4.5
- Session type: Continued (from previous context about spawn issues)

### Commands/Tools Used
- `/devflow:commit` - Create atomic commits
- `/devflow:code-review` - Run comprehensive code review
- `/devflow:devlog` - Generate this status document
- Manual git operations, code edits, test runs

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## Final Thoughts

This session successfully resolved a critical race condition that was causing spawn bursts. The TOCTOU vulnerability in `processNextTask()` meant that under load, multiple spawns could bypass the delay check - exactly the fork-bomb scenario we saw in production.

The promise-chain mutex solution is elegant and dependency-free. The key insight was that we needed serialization, not just a longer delay. The 16 code review findings were mostly false positives - the audit agents don't fully understand our architectural patterns (like "pure" meaning no side effects, not no state reads).

**Warning**: Never remove `withSpawnLock()` from `processNextTask()`. The 10-second delay alone is not sufficient - it was added as defense-in-depth, but the mutex is the actual fix for the TOCTOU race.

**Remember**: This is a snapshot in time. The project will have evolved since this was written. Use this as a starting point for understanding, not as gospel truth.

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*This document was auto-generated by the `/devlog` command*
*To generate a new status report, run `/devlog` in Claude Code*
