# Review by Principal Systems Engineer (Google/Stripe caliber) (Round 3)

## Principal Systems Engineer Review — Complete

**Branch**: `colonyos/when_we_implement_a_new_functionality_from_the_tasks_it_should_not_happen_in_par`

### VERDICT: **approve**

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### Key Findings

| # | Severity | Finding |
|---|----------|---------|
| 1 | **MEDIUM** | `_inject_memory_block()` and `_drain_injected_context()` are not called in the sequential per-task path — memory store context is silently missing from per-task agents. Every other implement path in the codebase injects this. Recommend wiring it in as a fast follow-up. |
| 2 | **LOW** | `git diff --name-only` and `git ls-files` return codes aren't checked — in a degraded git state, the safety-net commit silently fails with "no new changes to commit." |
| 3 | **LOW** | "Previously Completed Tasks" context block grows linearly — could consume significant context window for 20+ task chains. |

### What's Good

- **Architecture is right**: Sequential-by-default eliminates the merge conflict problem. Parallel preserved as opt-in. One agent per task with commits between them.
- **DAG failure propagation is correct**: BLOCKED propagation via set membership during topological iteration — simple and correct.
- **Security fixes are solid**: Selective staging via `_is_secret_like_path()`, sanitized commit messages, `timeout=30` on all subprocess calls.
- **Debuggability**: Per-task logging of file changes, blocked reasons, and cost/duration in PhaseResult artifacts. You can reconstruct what happened from logs.
- **No race conditions**: Sequential by design — the whole point.
- **Test coverage**: 27 new tests including security-focused tests for selective staging, plus existing suite passes (253/254, 1 pre-existing flake).

### Recommendation

Approve and merge. Wire `_inject_memory_block` + `_drain_injected_context` into `_run_sequential_implement` as a fast follow-up — it requires threading `memory_store` and `user_injection_provider` into the function signature.

Review artifact saved to `cOS_reviews/reviews/principal_systems_engineer/review_round_3.md`.