# Review by Principal Systems Engineer (Google/Stripe caliber) (Round 4)

## Review Complete — Principal Systems Engineer (Round 4)

**VERDICT: approve**

### Summary

The 529 retry implementation is **production-ready**. Here's what I found across 1,962 lines of diff across 12 files:

**Architecture — Correct:**
- Retry lives inside `run_phase()` at the transport layer, invisible to the orchestrator's heavyweight recovery system. This is the right layer for a 529/503 error.
- Clean extraction of `_run_phase_attempt()` separates streaming logic from retry policy.
- Two-pass fallback design (`[(primary, N), (fallback, N)]`) is elegant and well-bounded.

**All 10 functional requirements implemented** — error detection, retry with backoff, fallback, safety-critical blocking, observability, parallel independence.

**447 tests pass, zero regressions.**

### Findings (none blocking):

| Severity | File | Finding |
|----------|------|---------|
| LOW | `slack.py`, `init.py`, `router.py`, `cli.py` | ~8 `run_phase_sync()` call sites don't explicitly pass `retry_config` — they get sensible defaults (retry-enabled). Correct but implicit. |
| LOW | `agent.py` | `\b529\b` regex matches "line 529 of config.py" as transient — documented false positive, causes a harmless 30s retry delay. |
| INFO | `agent.py` | No circuit breaker for parallel retry storms — acceptable at current concurrency (3-4 agents), needs revisiting at scale. |

**Bottom line:** The design decisions are sound, the safety guards are solid, the tests are comprehensive, and the tech debt is well-documented. Ship it.
