Phx Codex Loop Agent Skill

Codex Loop (fix until clean)

Critic→Refiner loop with the Codex CLI as external critic: review → fix

approved findings → verify → re-review, until codex is clean or rounds run

out. Codex reviews; Claude fixes. Complements /phx-review (Claude panel)

— run either or both before a PR.

Usage

/phx-codex-loop                    # diff vs default branch, interactive
/phx-codex-loop --uncommitted      # staged + unstaged + untracked
/phx-codex-loop --base develop     # explicit base branch
/phx-codex-loop --auto             # auto-approve P0/P1/P2, skip P3
/phx-codex-loop --max-rounds 2     # default 3

Iron Laws

• BOUNDED rounds — never exceed --max-rounds (default 3) — each round

costs codex quota; report remaining findings instead of looping on

• Verify BEFORE re-review — mix compile --warnings-as-errors + tests

must pass before burning a codex round on broken code

• NEVER commit or push — leave git to the user
• Codex findings get Iron Law scrutiny — decline suggestions that

violate an Iron Law, with explanation in the round report

• Skipped findings are reported, never dropped — every finding ends as

fixed, declined (with reason), or deferred-by-user

• Missing CLI stops the skill with an install hint — suggest

/phx-review as the codex-free alternative; never crash

Workflow

Step 1: Preflight

Run command -v codex. If missing: STOP.

Show the install hint (brew install codex or npm i -g @openai/codex,

then codex login; codex doctor to diagnose) and suggest /phx-review.

Then two cheap checks that save review rounds:

• Dirty tree (git status --short, only when using --base): codex

inspects working-tree state too and WILL flag local dirt (stray edits,

dirty submodules) as findings. Surface the dirt and ask: clean/stash

first, or proceed knowing round 1 may spend findings on it.

• Missing rubric: if AGENTS.md has no ## Review guidelines

section, note once that /phx-init installs the Elixir rubric that

steers codex priorities — then proceed (it works without, on defaults).

Step 2: Detect Diff Mode

• Flag passed (--base/--uncommitted) → use as given
• Commits ahead of the default branch → --base {default}
• No commits yet → --uncommitted

Step 3: Round Loop (max --max-rounds, default 3)

• Review — ONE foreground Bash call, explicit timeout: 600000

(large diffs run 10+ min). On timeout with the process alive: ONE

until [ -f {out} ]; do sleep 5; done wait — never poll-spam or

pkill a running review (quota is spent either way). ALWAYS silence

the streams — only the -o file matters (10k+ lines otherwise):

   codex exec review --base {branch} --ephemeral \
     -o /tmp/codex-round-{n}.md > /tmp/codex-round-{n}.log 2>&1

NEVER pass custom instructions with a diff-mode flag — the CLI rejects

the combination; the rubric comes from AGENTS.md ## Review guidelines

(/phx-init). Parse the output file, NOT the exit code (0 even with

findings). Recipes: references/codex-cli.md.

• Clean check — parse the output file; no - [P{n}] bullets means

CLEAN → go to Step 4.

• Triage — emit the findings table

(# | P | file:line | title | proposed action) as **visible

response text BEFORE any AskUserQuestion call** — a table composed

only in thinking never renders. Then ask approve-or-skip per finding

(AskUserQuestion). With --auto: approve P0/P1/P2, skip P3 (list

skipped in the round report).

• Fix — apply approved fixes with user-visible diffs. Check each

against Iron Laws first (Law 4).

• Verify — scoped, before the next round:

   mix format {changed_files} && \
   mix compile --warnings-as-errors && mix test {affected_tests}

If verification fails 3 times, STOP with a BLOCKER report — do not

burn another codex round on broken code.

• Next round (n+1).

Step 4: Final Report

## Codex Loop Report — {CLEAN | MAX ROUNDS REACHED | BLOCKED}
Rounds: {n}/{max} | Fixed: {n} | Declined (Iron Law): {n} | Deferred: {n}
{per-round: findings → outcome}
{remaining findings if not CLEAN}

On CLEAN: suggest /phx-compound for non-obvious fixes, then commit/PR.

On MAX ROUNDS: list remaining findings; offer /phx-plan to convert them

into a follow-up plan.

Integration

implement → /phx-codex-loop (YOU ARE HERE) → clean → commit/PR → /phx-watch-pr --codex
     ↑ or arrive from /phx-review --codex verdict REQUIRES CHANGES

References

• references/codex-cli.md — invocation recipes, parse

patterns, verified gotchas (CLI 0.142.5)