# Review by Principal Systems Engineer (Google/Stripe caliber) (Round 1)

## Review Complete

As the **Principal Systems Engineer**, I've completed my holistic review of the parallel implement mode implementation. Here's my assessment:

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**VERDICT: request-changes**

**FINDINGS:**
- **[src/colonyos/orchestrator.py]**: Missing integration with ParallelOrchestrator - the parallel execution code exists but is never invoked from the main pipeline
- **[src/colonyos/parallel_orchestrator.py]**: `merge_worktrees()` lacks asyncio lock as specified in FR-5 (60-second timeout for deadlock prevention)
- **[src/colonyos/parallel_orchestrator.py]**: No budget allocation per FR-7 - per-task budgets not enforced
- **[src/colonyos/parallel_orchestrator.py]**: Conflict resolution agent spawning not implemented (FR-6)
- **[src/colonyos/orchestrator.py]**: `prepare_resume()` not updated to handle failed/blocked parallel tasks (FR-8)
- **[tests/]**: Missing end-to-end integration tests (Task 13.1-13.3)

**SYNTHESIS:**
The implementation delivers solid foundational components - a well-tested DAG parser (26 tests), secure worktree manager with path traversal prevention, proper preflight checks for graceful degradation, and thoughtful UI/stats extensions. All 93 new tests pass. However, **the feature cannot actually be used** because the `ParallelOrchestrator` module is never called from the main `orchestrator.py` pipeline. This is a critical integration gap.

From a distributed systems perspective, I'm particularly concerned about:
1. **Missing merge lock** - Without it, concurrent task completions could produce non-deterministic merge results or race conditions
2. **Missing budget enforcement** - One runaway agent could consume the entire phase budget, starving other tasks
3. **Missing conflict resolver** - When merges fail, there's no automated recovery path

The architecture is sound and debuggable (good logging, clear error paths, task correlation via `artifacts["task_id"]`), but the feature needs the final integration work and the safety mechanisms the PRD explicitly specified. Once integrated and the merge lock is added, this would be a clean, maintainable parallel execution system with proper blast radius containment.
