Ask Codex

Overview

Consult OpenAI Codex (gpt-5.3-codex with very high reasoning) for a second opinion using the CLI. Useful for validating approaches, catching edge cases, and getting fresh perspectives on complex decisions.

When to Use

•Architecture decisions with multiple valid approaches
•Code review before committing complex changes
•Debugging when stuck or unsure of root cause
•Implementation plan review
•Validating assumptions about unfamiliar APIs/libraries

CLI Usage

bash

codex exec -m gpt-5.3-codex "Your question or prompt here"

Default Model: gpt-5.3-codex (very high reasoning capability)

Key Options:

•exec: Run non-interactively (required for scripted use)
•-m, --model <MODEL>: Specify model (default: gpt-5.3-codex)
•-o, --output-last-message <FILE>: Write response to file
•--json: Output as JSONL for parsing

For code review specifically:

bash

codex review

Quick Reference

Scenario	Example Command
Architecture review	`codex exec "Review this approach for [X]. What edge cases am I missing?"`
Code review	`codex review` or `codex exec "Review this code: [snippet]"`
Debugging	`codex exec "I'm seeing [symptom]. I've tried [X]. What else should I check?"`
Implementation plan	`codex exec "Review this plan: [paste plan]. What issues do you see?"`

Best Practices

Provide context:

•Include relevant code snippets
•Explain what you've already considered
•State your constraints clearly

Ask specific questions:

•"What edge cases am I missing?" vs "Is this good?"
•"What would break if X happens?" vs "Any problems?"

Example - Architecture Decision:

bash

codex exec -m gpt-5.3-codex "I'm implementing WebSocket connection limiting in Cloudflare Durable Objects.

Option A: Track connections in a separate Map, sync on hibernation
Option B: Derive connections on-demand from existing connections Map

Which approach handles hibernation wake-up better? What edge cases should I consider?"

Example - Code Review:

bash

codex exec -m gpt-5.3-codex "Review this eviction logic for race conditions:

\`\`\`typescript
const userSockets = this.getUserSockets(userId);
while (userSockets.length > MAX_CONNECTIONS) {
  const oldest = userSockets.shift();
  oldest.close(4001, 'Connection replaced');
}
\`\`\`

The getUserSockets() returns a copy of the array. Is there a race condition?"

Example - Using Built-in Code Review:

bash

# Review current repository changes
codex review

Common Mistakes

Mistake	Fix
Vague questions	Be specific about what you want reviewed
No context	Include code, constraints, what you've tried
Asking yes/no	Ask "what issues" or "what edge cases"
Ignoring response	Evaluate critically, Codex can be wrong too

Integration with Workflow

Use ask-codex at key decision points:

•Before implementing: Validate approach
•After implementing: Review for issues with codex review
•When stuck: Get fresh debugging perspective
•Before committing: Final sanity check on complex changes