| name | codex-ab |
| description | Run an A/B codex review experiment — holistic codex review vs 3 focused dimension passes (security, ecto, liveview) on the branch diff, classify findings, report a panel-value verdict. Use when the branch is fresh, before any codex review runs. |
| effort | medium |
| argument-hint | [base-branch] |
Codex Panel A/B (contributor instrument — verdict decided)
Answer one question with evidence: do dimension-focused codex passes find
real issues that one holistic codex exec review misses? Runs both on the
same diff, then classifies every focused finding against the holistic pass.
DECIDED 2026-07-10 after 4 runs (2 fresh): panel KILLED. Fresh-only
1 real miss / 1 false positive plus one zero-value run at 4× cost —
real misses did not outnumber FPs. Kept as contributor tooling (NOT
distributed) for one possible retest: a UI-heavy diff with a single
extra liveview-focused pass (2× cost). Scoreboard:
.claude/research/2026-07-03-codex-review-integration.md §7.
Usage
/codex-ab # A/B against main (~5 min, 4 codex runs)
/codex-ab develop # explicit base branch
Iron Laws
- FRESH DIFF ONLY — ask the user to confirm this branch has NOT been
codex-reviewed yet (cloud or
/phx:codex-loop). A drained diff returns
NO FINDINGS everywhere and proves nothing — wasted quota
- Verify every REAL MISS in the code before counting it — a focused
finding only scores if the issue actually exists at that file:line
- Read ONLY the findings
.md files — streams are diverted to .log
files; never cat a log into context (10k+ lines each)
- Exactly 4 codex runs, never re-run dimensions — bounded quota
- Persist the verdict — an unrecorded experiment is wasted quota
Workflow
Step 1: Preflight
Run command -v codex — missing → STOP with install hint. Then:
git status --short dirty → warn (codex flags local dirt as findings)- Ask: "Has codex already reviewed this branch (PR review or codex-loop)?"
If yes → STOP, explain the fresh-diff requirement (Iron Law 1)
Step 2: Run the A/B (background, ~5 min)
bash ${CLAUDE_SKILL_DIR}/scripts/codex-panel-ab.sh {base} \
.claude/reviews/codex-ab-$(date +%Y-%m-%d-%H%M)
Use run_in_background — it runs 1 holistic codex exec review + 3
focused codex exec workers (security / ecto / liveview) in parallel,
all streams redirected. Do other work or wait; never poll.
Step 3: Classify
Read the 4 findings files (holistic.md, security.md, ecto.md,
liveview.md — small). For EACH focused finding:
| Class | Meaning | Test |
|---|
| DUPLICATE | Holistic already found it | Same file + same defect |
| REAL MISS | Genuine issue holistic missed | Read the code at file:line — defect confirmed (Iron Law 2) |
| FALSE POSITIVE | Manufactured, pre-existing, or wrong | Code check fails, or issue exists on base branch too |
Step 4: Verdict
Present:
## Codex Panel A/B — {branch} vs {base}
| dimension | findings | duplicate | real miss | false positive |
Holistic-only findings: {n}
Verdict this run: {REAL MISS count} real miss vs {FP count} false positive
Decision rule: build --codex-panel only if real misses outnumber false
positives across 2-3 fresh branches.
Write the verdict table to .claude/reviews/codex-ab-{date}/VERDICT.md.
Suggest repeating on the next 1–2 fresh branches before deciding.
Integration
fresh branch → /codex-ab (YOU ARE HERE) → verdict logged
├─ real misses win across runs → build /phx:review --codex-panel
└─ duplicates/FPs win → keep holistic /phx:codex-loop, drop panel idea
└─ OUTCOME 2026-07-10: this branch won — panel dropped
References
${CLAUDE_SKILL_DIR}/scripts/codex-panel-ab.sh — the 4-run harness- Related:
/phx:codex-loop (holistic fix loop), /phx:review --codex
