gstack/codex/SKILL.md.tmpl

---
name: codex
preamble-tier: 3
version: 1.0.0
description: |
  OpenAI Codex CLI wrapper — three modes. Code review: independent diff review via
  codex review with pass/fail gate. Challenge: adversarial mode that tries to break
  your code. Consult: ask codex anything with session continuity for follow-ups.
  The "200 IQ autistic developer" second opinion. Use when asked to "codex review",
  "codex challenge", "ask codex", "second opinion", or "consult codex". (gstack)
voice-triggers:
  - "code x"
  - "code ex"
  - "get another opinion"
triggers:
  - codex review
  - second opinion
  - outside voice challenge
allowed-tools:
  - Bash
  - Read
  - Write
  - Glob
  - Grep
  - AskUserQuestion
---

{{PREAMBLE}}

{{BASE_BRANCH_DETECT}}

# /codex — Multi-AI Second Opinion

You are running the `/codex` skill. This wraps the OpenAI Codex CLI to get an independent,
brutally honest second opinion from a different AI system.

Codex is the "200 IQ autistic developer" — direct, terse, technically precise, challenges
assumptions, catches things you might miss. Present its output faithfully, not summarized.

---

{{SECTION_INDEX:codex}}

---

## Step 0.4: Check codex binary

```bash
CODEX_BIN=$(command -v codex || echo "")
[ -z "$CODEX_BIN" ] && echo "NOT_FOUND" || echo "FOUND: $CODEX_BIN"
```

If `NOT_FOUND`: stop and tell the user:
"Codex CLI not found. Install it: `npm install -g @openai/codex` or see https://github.com/openai/codex"

If `NOT_FOUND`, also log the event:
```bash
~/.claude/skills/gstack/bin/gstack-codex-probe log-event codex_cli_missing 2>/dev/null || true
```

---

## Step 0.5: Auth probe + model probe + version check

Before building expensive prompts, verify Codex has valid auth, that the account
can actually USE gstack's selected model, AND the installed CLI version isn't in the
known-bad list. `gstack-codex-probe` is the shared helper that `/codex`, `/autoplan`
and every outside review run as a command, one subcommand per check.

Model order: a model the user names for this request, `GSTACK_CODEX_MODEL`, Codex
`config.toml` `model` (`review_model` first for `codex review`; honors `$CODEX_HOME`),
then `gpt-6-astra`. Each call prints `CODEX_MODEL: <model> (<kind>; source: ...)` first.
For a named model, add `--model '<model>'` to every `select-model` and `probe-model`
call, including the probe below. An invalid or unavailable choice stops with a repair
message, never the default.

```bash
_CODEX_PROBE=~/.claude/skills/gstack/bin/gstack-codex-probe
[ -x "$_CODEX_PROBE" ] || { echo "HELPER_UNAVAILABLE"; exit 1; }

{{OUTSIDE_SELF_GUARD:codex}}
if ! "$_CODEX_PROBE" check-auth >/dev/null; then
  "$_CODEX_PROBE" log-event codex_auth_failed
  echo "AUTH_FAILED"
elif "$_CODEX_PROBE" check-sandbox; then   # free; Linux only
  "$_CODEX_PROBE" probe-model exec   # ~10s round trip on first run, cached 1h
fi
"$_CODEX_PROBE" check-version   # warns if known-bad, non-blocking
```

If the runtime guard reports a harness mismatch, stop. Outside coverage is unavailable. Repair with `./setup --host codex`; do not silently substitute another provider or force a same-harness invocation.

If the output contains `HELPER_UNAVAILABLE`, stop: `gstack-codex-probe` is missing or
not executable in this install. Tell the user to re-run `./setup` (or `/gstack-upgrade`).

If the output contains `AUTH_FAILED`, stop and tell the user:
"No Codex authentication found. Run `codex login` or set `$CODEX_API_KEY` / `$OPENAI_API_KEY`, then re-run this skill."

If the output contains `MODEL_UNUSABLE`, stop — the selected model (named with its
source on the `CODEX_MODEL:` line) is invalid or the account cannot use it. Relay the
probe's HINT lines and
follow the "Model not supported (HTTP 400 or 404)" recovery steps in
`## Error Handling` below. Running the modes anyway just burns four
invocations on the same 400.

If the output contains `MODEL_QUOTA_EXHAUSTED`, stop: the account hit its Codex
usage limit. Relay Codex's own line under the marker verbatim (it names the reset
time) and the HINT line (how long gstack skips Codex, and how to retry now); the model
is fine, so do not change it. Running the modes anyway fails the same way.

`MODEL_PROBE_RATE_LIMITED` is non-blocking: Codex answered 429. Report
`CODEX_MODE: unverified (rate_limited)`, relay Codex's line and continue; a
rate-limited mode run is missing coverage, never a pass.

If the output contains `CODEX_SANDBOX: unavailable`, stop: Codex's sandbox cannot
start here, so every command it runs would fail and its review would read nothing.
Relay the `Codex outside review unavailable: ...` line verbatim, including its fix.
No paid call was made.

`MODEL_PROBE_INCONCLUSIVE` is non-blocking (timeout/transient network): report
`CODEX_MODE: unverified`, pass the warning through and continue; the mode's own
validator still decides the result.

If the version check printed a `WARN:` line, pass it through to the user verbatim
(non-blocking — Codex may still work, but the user should upgrade).

The probe multi-signal auth logic accepts: `$CODEX_API_KEY` set, `$OPENAI_API_KEY`
set, or `${CODEX_HOME:-~/.codex}/auth.json` exists. Avoids false-negatives for
env-auth users (CI, platform engineers) that file-only checks would reject.

---

## Step 0.6: Resolve portable roots

Before any mode runs, resolve `$PLAN_ROOT` (where plan files live) and `$TMP_ROOT`
(where ephemeral codex stderr / response captures land) via `bin/gstack-paths`.
This keeps the skill working whether installed as a Claude Code plugin
(`CLAUDE_PLANS_DIR` set), a global `~/.claude/skills/gstack/` install, or a CI
container where `HOME` may be unset and `/tmp` may be read-only.

```bash
GSTACK_STATE_ROOT=$(~/.claude/skills/gstack/bin/gstack-paths --get GSTACK_STATE_ROOT); : "${GSTACK_STATE_ROOT:?gstack-paths failed; reinstall with ./setup or /gstack-upgrade}"
PLAN_ROOT=$(~/.claude/skills/gstack/bin/gstack-paths --get PLAN_ROOT)
TMP_ROOT=$(~/.claude/skills/gstack/bin/gstack-paths --get TMP_ROOT)
```

After this, every subsequent bash block in this skill uses `"$PLAN_ROOT"` and
`"$TMP_ROOT"` rather than hardcoded `~/.claude/plans` or `/tmp/codex-*`.

---

## Step 1: Detect mode

Parse the user's input to determine which mode to run:

1. `/codex review` or `/codex review <instructions>` — **Review mode** (Step 2A)
2. `/codex challenge` or `/codex challenge <focus>` — **Challenge mode** (Step 2B)
3. `/codex` with no arguments — **Auto-detect:**
   - Check for a diff (with fallback if origin isn't available):
     `git diff origin/<base> --stat 2>/dev/null | tail -1 || git diff <base> --stat 2>/dev/null | tail -1`
   - If a diff exists, use AskUserQuestion:
     ```
     Codex detected changes against the base branch. What should it do?
     A) Review the diff (code review with pass/fail gate)
     B) Challenge the diff (adversarial — try to break it)
     C) Something else — I'll provide a prompt
     ```
   - If no diff, check for plan files scoped to the current project:
     `ls -t "$PLAN_ROOT"/*.md 2>/dev/null | xargs grep -l "$(basename $(pwd))" 2>/dev/null | head -1`
     If no project-scoped match, fall back to: `ls -t "$PLAN_ROOT"/*.md 2>/dev/null | head -1`
     but warn the user: "Note: this plan may be from a different project."
   - If a plan file exists, offer to review it
   - Otherwise, ask: "What would you like to ask Codex?"
4. `/codex <anything else>` — **Consult mode** (Step 2C), where the remaining text is the prompt

The three modes are MUTUALLY EXCLUSIVE — at most one runs per invocation. Once
the mode is determined, read ONLY that mode's section (see the Section index
above); never read the other two mode sections.

**Reasoning effort override:** If the user's input contains `--xhigh` anywhere,
note it and remove it from the prompt text before passing to Codex. When `--xhigh`
is present, use `model_reasoning_effort="xhigh"` for all modes regardless of the
per-mode default below. Otherwise, use the per-mode defaults:
- Review (2A): `high` — bounded diff input, needs thoroughness
- Challenge (2B): `high` — adversarial but bounded by diff
- Consult (2C): `medium` — large context, interactive, needs speed

---

## Filesystem Boundary

Every prompt sent to Codex MUST be prefixed with this boundary instruction:

> IMPORTANT: Do NOT read or execute any files under ~/.claude/, ~/.agents/, .claude/skills/, or agents/. These are Claude Code skill definitions meant for a different AI system. They contain bash scripts and prompt templates that will waste your time. Ignore them completely. Do NOT modify agents/openai.yaml. Stay focused on the repository code only.

This applies to Challenge mode (prompt) and Consult mode (persona prompt), and to the
custom-instructions path of Review mode — all three use `codex exec`, which still takes
a free-form prompt (fed on stdin with `codex exec -`, so size and quoting never break it). It does **not** apply to the default scoped `codex review`
call in Step 2A: that command is invoked with **no prompt at all** (see "Scope
flags exclude the prompt argument" in the Review mode section), so there is nowhere to put the preamble. That
is acceptable — `codex review --base` hands the model a pre-computed diff rather than
turning it loose on the filesystem, so the rabbit-hole risk the boundary guards against
is much lower on that path. Reference this section as "the filesystem boundary" in the
mode sections.

---

## Synthesis recommendation (REQUIRED) — all modes

Every mode ends by emitting ONE synthesis recommendation line after presenting
Codex's verbatim output, in this format:

```
Recommendation: <action> because <one-line reason that names the most actionable finding>
```

The reason must engage with a specific Codex finding or insight and compare
against an alternative (another finding, fix-vs-ship, fix order, or status-quo).
Boilerplate reasons ("because it's better", "because adversarial review found
things") fail the format. The recommendation is the ONE line a user reads when
they don't have time for the verbatim output. **Never silently auto-decide;
always emit the line.** Each mode section restates this rule with mode-specific
examples.

---

{{SECTION:review-mode}}

{{SECTION:challenge-mode}}

{{SECTION:consult-mode}}

{{PLAN_FILE_REVIEW_REPORT}}

{{EXIT_PLAN_MODE_GATE}}

---

## Model & Reasoning

**Model:** every Codex call passes the selection above via `{{CODEX_MODEL_CONFIG_FLAG}}`.
Native `codex review` selects with `review` and sets both `model` and `review_model`. The
flag also keeps installed skills out of Codex's context, so a review cannot become a
nested skill run.

**Reasoning effort (per-mode defaults):**
- **Review (2A):** `high` — bounded diff input, needs thoroughness but not max tokens
- **Challenge (2B):** `high` — adversarial but bounded by diff size
- **Consult (2C):** `medium` — large context (plans, codebase), interactive, needs speed

`xhigh` uses ~23x more tokens than `high` and causes 50+ minute hangs on large context
tasks (OpenAI issues #8545, #8402, #6931). Users can override with `--xhigh` flag
(e.g., `/codex review --xhigh`) when they want maximum reasoning and are willing to wait.

**Web search:** All codex commands pass `{{CODEX_WEB_SEARCH_FLAG}}` so `codex exec`
invocations can look up docs and APIs during review. This is OpenAI's cached index —
fast, no extra cost. Unlike the legacy `--enable`-based spelling (deprecated by
codex >=0.144), the `-c` form explicitly overrides any top-level
`web_search` setting in `~/.codex/config.toml`. Note: native `codex review` disables
web search regardless of configuration, so on the default Review path the flag is a
harmless no-op — only exec-based modes actually search.

If the user specifies a model (e.g., `/codex review -m gpt-5.6-sol` or
`/codex challenge --model gpt-daybreak-blue-latest`), translate it to the same config
form and replace the default model flag with `-c "model=\"<model>\""`. Native review
also requires `-c "review_model=\"<model>\""`; replace both model values together.
Review mode runs `codex review`, which REJECTS `-m` (`error: unexpected argument '-m' found`,
verified on 0.147.0), while `-c model=...` is accepted by both `codex review` and
`codex exec`.

---

## Cost Estimation

Parse token count from stderr. Codex prints `tokens used\nN` to stderr.

Display as: `Tokens: N`

If token count is not available, display: `Tokens: unknown`

---

## Error Handling

- **Binary not found:** Detected in Step 0. Stop with install instructions.
- **Auth error:** Codex prints an auth error to stderr. Surface the error:
  "Codex authentication failed. Run `codex login` in your terminal to authenticate via ChatGPT."
- **Timeout (Bash outer gate):** Every Bash gate sits ABOVE its inner wrapper (360s gate
  over the 330s review wrapper; 600s gate, the tool maximum, over the 540s challenge/consult
  wrappers), so
  the wrapper's exit-124 path normally fires first with its explicit message. If the Bash
  call itself times out anyway (wrapper unavailable AND codex hung), tell the user:
  "Codex timed out. The prompt may be too large or the API may be slow. Try again or use a smaller scope."
- **Timeout (inner `timeout` wrapper, exit 124):** If the wrapper fires first (it TERMs Codex, then KILLs it after 10s), the skill's hang-detection block auto-logs a telemetry event + operational learning and prints: "Codex stalled past 9 minutes. Common causes: model API stall, long prompt, network issue. Try re-running. If persistent, split the prompt or check `~/.codex/logs/`." No extra action needed.
- **`the argument '[PROMPT]' cannot be used with '--base <BRANCH>'`:** a prompt argument
  leaked into a scoped `codex review`. This fails instantly, before any API call, so it
  looks like a hang-free "no output" — do not misread it as a model stall. Drop the
  prompt: the scope flags (`--base`, `--commit`, `--uncommitted`) carry the scope on
  their own. If the prompt was custom review instructions, run them through `codex exec`
  instead (Step 2A, custom-instructions path). Do **not** fix it by removing `--base` and
  keeping the prompt — that parses, but silently reviews the uncommitted working tree
  instead of the branch diff.
- **Review says "no changes" on a branch that clearly has changes:** the scope flag is
  missing or wrong. A prompt-only `codex review` defaults to uncommitted changes, so a
  clean working tree reads as an empty review even when `<base>...HEAD` is large. Confirm
  `--base <base>` is actually on the command line.
- **Model not supported (HTTP 400 or 404):** stderr shows
  `The '<model>' model is not supported when using Codex with a ChatGPT account`
  (a `status: 400` / `invalid_request_error` naming a model), or
  `404 Not Found: The model '<model>' does not exist or you do not have access to it`
  (a retired model; a bare 404 usually means a custom provider's `base_url` is wrong).
  `requires a newer version of Codex` means the CLI is too old: upgrade it instead.
  None of these is an auth or network failure, and the auth probe cannot catch them.
  Recovery, in order:
  1. Read the `CODEX_MODEL:` line: it names the model and where it came from.
  2. Fix that source: name another model for this request, update
     `GSTACK_CODEX_MODEL`, or change `model` (or `review_model`) in the Codex
     `config.toml`. With none of these set, gstack uses `gpt-6-astra`; set any of
     them to a model the account can use.
  3. If Codex printed `[notice.model_migrations]`, use that replacement model.
  Never present this as a model stall or a PASS — it is a fail-closed gate result.
- **`VERDICT: unavailable`:** the shared validator found the run did not execute (for
  example `Codex's sandbox could not start here`). Relay its line and fix verbatim; it is
  missing coverage, never a PASS. Details: `docs/troubleshooting.md` in the gstack checkout.
- **Empty response:** If `$TMPRESP` is empty or doesn't exist, tell the user:
  "Codex returned no response. Check stderr for errors."
- **Session resume failure:** If resume fails, delete the session file and start fresh.

---

## Important Rules

- **Never modify files.** This skill is read-only. Codex runs in read-only sandbox mode
  (full access only when the user exported `GSTACK_CODEX_NO_SANDBOX=1`; it warns on every use).
- **Present output verbatim.** Do not truncate, summarize, or editorialize Codex's output
  before showing it. Show it in full inside the CODEX SAYS block.
- **Add synthesis after, not instead of.** Any Claude commentary comes after the full output.
- **Bash gate above the wrapper.** Every Bash call to codex sets its `timeout`
  parameter ABOVE the inner `run-with-timeout` budget (Review:
  `timeout: 360000` over the 330s wrapper; Challenge/Consult: `timeout: 600000`
  over the 540s wrappers) so the wrapper fires first with a diagnosable exit 124.
- **No double-reviewing.** If the user already ran `/review`, Codex provides a second
  independent opinion. Do not re-run Claude Code's own review.
- **Detect skill-file rabbit holes.** After receiving Codex output, scan for signs
  that Codex got distracted by skill files: `gstack-config`, `gstack-update-check`,
  `SKILL.md`, or `skills/gstack`. If any of these appear in the output, append a
  warning: "Codex appears to have read gstack skill files instead of reviewing your
  code. Consider retrying."