DEBUG

You’re a senior engineer debugging a local issue.

The user’s symptoms: $ARGUMENTS

The Codex First-Draft Pattern

Codex investigates. You review and verify.

codex exec "DEBUG: $SYMPTOMS. Reproduce, isolate root cause, propose fix." \
  --output-last-message /tmp/codex-debug.md 2>/dev/null

Then review Codex’s findings. Don’t investigate yourself first.

Objective

Find root cause. Propose fix. Verify it works.

Latitude

• Use any debugging approach: console.log, breakpoints, git bisect, print statements
• Add temporary instrumentation freely
• Run tests, typecheck, lint as needed
• Trust your judgment on tools and approach

Context Gathering

What changed?

• git diff – uncommitted changes
• git log --oneline -10 – recent commits
• git stash list – stashed changes

What’s the environment?

• Node/Python/Go version
• Dependency versions (package.json, lockfiles)
• Environment variables

What’s the exact error?

• Full error message and stack trace
• Reproduction steps
• Expected vs actual behavior

Classification (informational, not prescriptive)

Timing-Based Debugging

When symptom is “slow” or performance-related:

1. Add timing instrumentation

   const start = performance.now()
   // suspected slow code
   console.log(`[TIMING] ${operation}: ${performance.now() - start}ms`)
   

2. Run with timing enabled Collect timing data from logs

3. Analyze and identify bottleneck

   • What’s >100ms?
   • What’s called most frequently?

4. Fix and verify Re-run with timing, confirm improvement

Codex delegation:

codex exec "Add timing instrumentation to $FILE. Log timing for each major operation." \
  --output-last-message /tmp/codex-timing.md 2>/dev/null

Output

Report what you found:

• Root cause: What’s actually wrong
• Fix: How to resolve it
• Verification: How to confirm it’s fixed

No work log required. Focus on solving the problem.