Codex Skill

Codex Agent Skill

Operate Codex CLI as a managed coding agent — from worktree setup through PR merge.

Prerequisites

codex --version  # Verify installed
# Install: npm i -g @openai/codex  or  brew install codex
tmux -V          # tmux required for full workflow

CLI Quick Reference

Execution Modes

Quick Mode — Small Tasks

For trivial fixes, one-file changes, or analysis. Use exec (non-interactive):

# Via OpenClaw exec — use background=true + pty=true, NO hard timeout
# pty=true ensures codex CLI flushes output properly (no buffering issues)
# (hard timeout kills the process; instead we poll and extend)
exec(command="codex exec --full-auto 'fix the typo in README.md'",
     workdir="/path/to/project", background=true, pty=true)

# With high reasoning
exec(command="codex exec -c 'model_reasoning_effort=high' --full-auto 'fix the auth bug'",
     workdir="/path/to/project", background=true, pty=true)

Adaptive Timeout (Poll-and-Extend)

Do NOT use timeout= for codex tasks. Instead, use background execution with periodic polling. This prevents premature kills on long-running tasks:

1. Launch with background=true (no timeout)
2. Poll every ~5 min with process(action="poll", sessionId=<id>, timeout=300000)
3. If process is still running → it's making progress, keep waiting
4. If process exited → check logs, done
5. Safety net: if no new output for 12 hours, ask user before killing

Poll loop (agent behavior, not a script):

  poll_interval = 5 min (300000 ms)
  max_silent_rounds = 144  (= 12 hours with no new output → ask user)

  repeat:
    result = process(action="poll", sessionId=<id>, timeout=300000)
    if result.completed:
      → check exit code, read logs, report result
      → break
    else:
      new_output = process(action="log", sessionId=<id>, limit=20)
      if new_output changed since last check:
        silent_rounds = 0          # still producing output, keep going
      else:
        silent_rounds += 1
      if silent_rounds >= max_silent_rounds:
        → notify user: "Codex has been silent for 12 hours, kill or keep waiting?"
        → wait for user decision

This way tasks that need 5 min or several hours both work without premature kills.

Quick Mode caveats:

• Session output is held in memory only — lost on OpenClaw restart (no disk persistence). For truly critical tasks, prefer Full Mode (tmux + log file).
• In-memory output is capped by PI_BASH_MAX_OUTPUT_CHARS. Very verbose codex tasks may lose early output from process log. Use process log offset:0 limit:50 to check if the beginning is still available; if not, the cap was hit.
• process is scoped per agent — you can only see sessions you started.

Full Mode — Features, Bugfixes, Refactors

For non-trivial tasks, use the full workflow below. This gives you:

• Isolated worktree — no conflicts with other work
• tmux session — mid-task steering without killing the agent
• Task tracking — know what's running at all times
• Quality gates — Definition of Done checklist
• Smart retries — don't waste tokens on repeated failures

Full Workflow: Task → Merged PR

Step 1: Create Worktree

Isolate each task in its own worktree and branch:

TASK_ID="feat-custom-templates"
BRANCH="feat/$TASK_ID"
REPO_ROOT=$(git rev-parse --show-toplevel)
WORKTREE="/tmp/worktrees/$TASK_ID"

git worktree add -b "$BRANCH" "$WORKTREE" origin/main
cd "$WORKTREE"

# Install dependencies (adapt to your stack)
pnpm install   # or: npm install / go mod tidy / pip install -r requirements.txt

Step 2: Launch Agent in tmux

Start Codex in interactive mode (no exec) so you can steer mid-task. Important: Use tmux pipe-pane to log output — do NOT use | tee because it turns stdout into a pipe, which breaks interactive mode (codex detects !isatty(stdout) and may disable interactive features, breaking send-keys steering).

LOG_FILE="/tmp/worktrees/$TASK_ID/codex-output.log"

# 1. Create session (starts a shell — codex not launched yet)
tmux new-session -d -s "$TASK_ID" -c "$WORKTREE"

# 2. Attach logging BEFORE launching codex — prevents losing early output
#    stdbuf -oL = line-buffered writes, so tail -f shows progress in real time
#    (plain cat buffers when writing to a file, causing monitoring lag)
tmux pipe-pane -t "$TASK_ID" -o "stdbuf -oL cat >> $LOG_FILE"

# 3. Launch codex via send-keys — all output captured from the start
#    Exit code is appended to log on completion for reliable status detection
tmux send-keys -t "$TASK_ID" \
  'codex -c "model_reasoning_effort=high" \
   --dangerously-bypass-approvals-and-sandbox \
   '"'"'Your detailed prompt here.

When completely finished:
1. Commit all changes with descriptive messages
2. Push the branch: git push -u origin '"$BRANCH"'
3. Create PR: gh pr create --fill
4. Notify: openclaw system event --text "Done: '"$TASK_ID"'" --mode now'"'"' \
   ; echo "CODEX_EXIT=$?" >> '"$LOG_FILE" Enter

Why this order (session → pipe-pane → send-keys)?

• No race condition — if you pass the command directly to tmux new-session, output produced before pipe-pane attaches is lost from the log file
• Exit code captured — echo "CODEX_EXIT=$?" appends the exit code to the log, so you can distinguish success from crash (otherwise tmux discards it on session close)
• Line-buffered logging — stdbuf -oL ensures tail -f $LOG_FILE works in real time

Why interactive mode (no exec)?

• Allows mid-task steering via tmux send-keys
• Agent can be redirected without killing and restarting
• --dangerously-bypass-approvals-and-sandbox is safe in container/sandbox environments

Step 3: Register Task

Track all active tasks in a JSON registry:

mkdir -p "$REPO_ROOT/.clawd"
TASKS_FILE="$REPO_ROOT/.clawd/active-tasks.json"

# Initialize if not exists
[ -f "$TASKS_FILE" ] || echo '{"tasks":[]}' > "$TASKS_FILE"

# Register
jq --arg id "$TASK_ID" --arg branch "$BRANCH" --arg wt "$WORKTREE" \
  '.tasks += [{
    "id": $id,
    "agent": "codex",
    "branch": $branch,
    "worktree": $wt,
    "tmuxSession": $id,
    "status": "running",
    "startedAt": (now|floor),
    "pr": null,
    "retries": 0,
    "checks": {}
  }]' "$TASKS_FILE" > /tmp/tasks.$$.json && mv /tmp/tasks.$$.json "$TASKS_FILE"

Step 4: Monitor & Steer

# --- Status check ---

# Is the agent still running?
tmux has-session -t "$TASK_ID" 2>/dev/null && echo "running" || echo "done"

# Check exit code (if agent finished — written by the exit-code capture in Step 2)
grep "CODEX_EXIT=" "/tmp/worktrees/$TASK_ID/codex-output.log"

# --- Reading output ---

# Use the LOG FILE, not capture-pane, for long-running tasks.
# tmux capture-pane only holds ~2000 lines of scrollback — earlier output is silently
# dropped. The log file (via pipe-pane) retains everything.

# View recent output (clean — strips ANSI escape codes from colors/spinners)
sed 's/\x1b\[[0-9;]*[a-zA-Z]//g' "/tmp/worktrees/$TASK_ID/codex-output.log" | tail -100

# Follow output in real time (works because of stdbuf -oL in Step 2)
tail -f "/tmp/worktrees/$TASK_ID/codex-output.log"

# Search for errors (strip ANSI first for clean grep results)
sed 's/\x1b\[[0-9;]*[a-zA-Z]//g' "/tmp/worktrees/$TASK_ID/codex-output.log" \
  | grep -i "error\|fail\|panic"

# Quick glance via tmux pane (fine for short tasks, unreliable for long ones)
tmux capture-pane -t "$TASK_ID" -p -S -50

# --- Detecting stuck agents ---

# Check if codex is making file changes (no changes for a long time → may be stuck)
git -C "$WORKTREE" status --short

# Check if the same error appears repeatedly (loop detection)
sed 's/\x1b\[[0-9;]*[a-zA-Z]//g' "/tmp/worktrees/$TASK_ID/codex-output.log" \
  | grep -i "error" | sort | uniq -c | sort -rn | head -5

# --- Mid-task steering (DON'T kill — redirect!) ---

# Agent going the wrong direction?
tmux send-keys -t "$TASK_ID" "Stop. Focus on the API layer first, not the UI." Enter

# Agent missing context?
tmux send-keys -t "$TASK_ID" "The schema is in src/types/template.ts. Use that." Enter

# Agent's context window filling up?
tmux send-keys -t "$TASK_ID" "Focus only on these 3 files: api.ts, handler.ts, types.ts" Enter

# Agent needs test guidance?
tmux send-keys -t "$TASK_ID" "Run 'npm test -- --grep auth' to verify your changes." Enter

Monitoring cadence: Check every 5–10 minutes, not every 30 seconds. Agents need time to work.

Step 5: Definition of Done

A PR is NOT ready for review until all checks pass:

✅ PR created              → gh pr list --head "$BRANCH"
✅ No merge conflicts       → gh pr view $PR_NUM --json mergeable -q '.mergeable'
✅ CI passing               → gh pr checks $PR_NUM
✅ AI code review passed    → at least one cross-model review (see Step 6)
✅ UI screenshots included  → (if applicable) screenshot in PR description

Quick inline check:

PR_NUM=$(gh pr list --head "$BRANCH" --json number -q '.[0].number')
echo "PR: #$PR_NUM"
gh pr checks "$PR_NUM"
gh pr view "$PR_NUM" --json mergeable -q '.mergeable'

Step 6: Multi-Model Code Review

Review with a different model than the one that wrote the code. Different models catch different issues:

DIFF=$(gh pr diff "$PR_NUM")

# Option A: Claude reviews Codex's code (best for security & overengineering checks)
echo "$DIFF" | claude -p \
  --append-system-prompt "You are a senior code reviewer. Be concise, flag only real issues." \
  "Review this PR diff. Focus on: bugs, edge cases, missing error handling,
   race conditions, security issues. Cite file and line numbers.
   Output: list of issues with severity (critical/warning/info)."

# Option B: Different Codex model reviews with analysis focus
echo "$DIFF" | codex exec -s read-only \
  "Review this PR diff for logic errors, performance issues, and missing tests."

Post review results to PR:

gh pr comment "$PR_NUM" --body "## AI Code Review

$REVIEW_OUTPUT"

Update task registry:

jq --arg id "$TASK_ID" \
  '(.tasks[] | select(.id == $id)).checks.codeReviewPassed = true' \
  "$TASKS_FILE" > /tmp/tasks.$$.json && mv /tmp/tasks.$$.json "$TASKS_FILE"

Step 7: Notify

If you included the notify command in the agent prompt (Step 2), the agent self-notifies on completion.

Otherwise, notify after DoD passes:

openclaw system event --text "✅ PR #$PR_NUM ready for review: $TASK_ID — all checks passed" --mode now

Update task status:

jq --arg id "$TASK_ID" --argjson pr "$PR_NUM" \
  '(.tasks[] | select(.id == $id)) |= (.status = "done" | .pr = $pr | .completedAt = (now|floor))' \
  "$TASKS_FILE" > /tmp/tasks.$$.json && mv /tmp/tasks.$$.json "$TASKS_FILE"

Step 8: Cleanup

After PR is merged:

git worktree remove "$WORKTREE" 2>/dev/null
git branch -d "$BRANCH" 2>/dev/null

# Remove from registry
jq --arg id "$TASK_ID" '.tasks = [.tasks[] | select(.id != $id)]' \
  "$TASKS_FILE" > /tmp/tasks.$$.json && mv /tmp/tasks.$$.json "$TASKS_FILE"

Smart Retry Strategy

When an agent fails, analyze the failure and adapt the prompt — don't just re-run blindly.

Max 3 retries. After that, escalate to human.

RETRY=$((RETRY + 1))
if [ "$RETRY" -gt 3 ]; then
  openclaw system event --text "🚨 BLOCKED: $TASK_ID failed after 3 retries — needs human help" --mode now
  jq --arg id "$TASK_ID" '(.tasks[] | select(.id == $id)).status = "blocked"' \
    "$TASKS_FILE" > /tmp/tasks.$$.json && mv /tmp/tasks.$$.json "$TASKS_FILE"
  exit 1
fi

# Capture what went wrong — strip ANSI codes for clean error text
LOG_FILE="/tmp/worktrees/$TASK_ID/codex-output.log"
if [ -f "$LOG_FILE" ]; then
  FAILURE_LOG=$(sed 's/\x1b\[[0-9;]*[a-zA-Z]//g' "$LOG_FILE" | tail -500)
else
  FAILURE_LOG=$(tmux capture-pane -t "$TASK_ID" -p -S -200)
fi
CI_LOG=$(gh pr checks "$PR_NUM" 2>/dev/null || echo "no PR yet")
tmux kill-session -t "$TASK_ID" 2>/dev/null

# Mark retry boundary in log (so retries don't blend together)
echo "=== RETRY $RETRY — $(date -Iseconds) ===" >> "$LOG_FILE"

# Respawn: session first, pipe-pane second, send-keys third (same pattern as Step 2)
tmux new-session -d -s "$TASK_ID" -c "$WORKTREE"
tmux pipe-pane -t "$TASK_ID" -o "stdbuf -oL cat >> $LOG_FILE"
tmux send-keys -t "$TASK_ID" \
  'codex -c "model_reasoning_effort=high" \
   --dangerously-bypass-approvals-and-sandbox \
   '"'"'Previous attempt failed. Error output:
'"$FAILURE_LOG"'

CI status: '"$CI_LOG"'

Fix the issues above and complete the original task.
[...your enriched instructions here...]

When done: commit, push, gh pr create --fill, then run:
openclaw system event --text "Done: '"$TASK_ID"' (retry '"$RETRY"')" --mode now'"'"' \
   ; echo "CODEX_EXIT=$?" >> '"$LOG_FILE" Enter

# Update registry
jq --arg id "$TASK_ID" --argjson r "$RETRY" \
  '(.tasks[] | select(.id == $id)) |= (.retries = $r | .status = "running")' \
  "$TASKS_FILE" > /tmp/tasks.$$.json && mv /tmp/tasks.$$.json "$TASKS_FILE"

Parallel Execution

Run multiple agents simultaneously on different tasks:

# Helper: launch codex in tmux with proper logging (session → pipe-pane → send-keys)
launch_codex() {
  local TASK="$1" WORKDIR="$2" PROMPT="$3"
  local LOG="$WORKDIR/codex-output.log"
  tmux new-session -d -s "$TASK" -c "$WORKDIR"
  tmux pipe-pane -t "$TASK" -o "stdbuf -oL cat >> $LOG"
  tmux send-keys -t "$TASK" \
    "pnpm install && codex --dangerously-bypass-approvals-and-sandbox '$PROMPT'; echo \"CODEX_EXIT=\$?\" >> $LOG" Enter
}

# Task 1: Feature
git worktree add -b feat/auth /tmp/worktrees/feat-auth origin/main
launch_codex feat-auth /tmp/worktrees/feat-auth "Implement JWT auth..."

# Task 2: Bugfix
git worktree add -b fix/payments /tmp/worktrees/fix-payments origin/main
launch_codex fix-payments /tmp/worktrees/fix-payments "Fix payment webhook..."

# Dashboard: check all agents (use log files, not capture-pane, for reliable output)
tmux ls
for s in $(tmux ls -F '#{session_name}' 2>/dev/null); do
  LOG="/tmp/worktrees/$s/codex-output.log"
  echo "=== $s ==="
  if tmux has-session -t "$s" 2>/dev/null; then
    sed 's/\x1b\[[0-9;]*[a-zA-Z]//g' "$LOG" 2>/dev/null | tail -5 || echo "(no log yet)"
  else
    EXIT=$(grep "CODEX_EXIT=" "$LOG" 2>/dev/null | tail -1)
    echo "(exited) ${EXIT:-exit code unknown}"
  fi
done

Codex-Specific Features

Reasoning Effort

Control how much the model "thinks" before acting:

# High — for complex logic, multi-file refactors
codex -c "model_reasoning_effort=high" --full-auto "refactor auth module"

# Medium — balanced (default)
codex exec --full-auto "add input validation"

# Low — for trivial/mechanical changes
codex -c "model_reasoning_effort=low" --full-auto "rename all instances of foo to bar"

Sandbox Modes

JSON Output

# Structured output for programmatic processing
codex exec --full-auto --json "implement and test the feature"

# Save to file
codex exec --full-auto -o results.txt "run analysis"

Resume Session

# Resume last session with a follow-up task
codex exec resume --last "now add tests for the feature you just built"

Best Practices

Prompt Quality

• Include file paths: "The entry point is src/index.ts, config in src/config/"
• Include schemas/types: Paste relevant type definitions into the prompt
• Include test commands: "Verify with: npm test -- --grep auth"
• Include commit convention: "Use conventional commits: feat:, fix:, chore:"
• Include error logs: When retrying, always attach the failure output

Scope Management

• One task per agent — don't ask for "refactor everything"
• Pre-install dependencies before launching the agent
• Be specific — "Add rate limiting to POST /api/users" not "improve the API"
• Use high reasoning effort for complex tasks, low for mechanical ones

When to Interrupt (Ask Human)

• Destructive operations (drop tables, force push main)
• Security decisions (expose credentials, change auth)
• Ambiguous requirements with significant trade-offs
• All other decisions: proceed autonomously