How to build a Claude Code and Codex code review workflow: from local changes to PR feedback

Claude Code and Codex are both useful for coding, but they are strongest when they are not doing the same job at the same time. A clean workflow is to let Claude Code implement and iterate, then let Codex review the diff from a fresh angle before the PR is merged.

This article focuses on a closed-loop review flow: local changes, independent review, feedback repair, PR summary, and optional review gate.

Define the Role of Each Tool First

Claude Code is a good primary workbench for editing, refactoring, and following a conversation. Codex is well suited for an independent second pass: it can inspect the patch, challenge assumptions, look for missing tests, and review risky areas.

Do not let both agents edit the same files at the same time. One agent should own implementation; the other should review.

Minimal Usable Flow

The smallest workflow looks like this:

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Claude Code implements the change
  -> tests or local checks run
  -> Codex reviews the diff
  -> Claude Code fixes confirmed issues
  -> Codex reviews again if needed
  -> human writes or approves the PR

This is already useful because the second agent does not share the same conversational bias as the first one.

Calling Codex from Claude Code

If you use a Claude Code plugin or slash command that calls Codex, keep the command narrow:

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/codex:review

For a more adversarial pass:

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/codex:adversarial-review

If you are not using a plugin, you can simply open Codex in the same repository and ask it to review the current diff.

Local Change Review

Before asking for review, make the diff readable:

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git status --short
git diff --stat
git diff

Then ask Codex:

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Review the current uncommitted diff. Focus on correctness, regressions, missing tests, security risks, and behavior changes. Do not rewrite the code; report findings with file and line references when possible.

This prompt keeps Codex in review mode instead of edit mode.

Pre-PR Review

Before opening a PR, Codex can help check whether the change is ready:

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Review this branch before PR. Check whether the change matches the stated goal, whether tests cover the risky paths, and whether the PR description should mention migration, config, compatibility, or rollout risks.

Good review output should include:

real findings first;
missing tests;
behavior or compatibility risks;
open questions;
a concise PR summary.

When to Use Adversarial Review

Use a stronger review when the change touches:

authentication or authorization;
payments or billing;
data migration;
security-sensitive code;
concurrency or background jobs;
shared libraries;
production configuration;
public API behavior.

Do not run adversarial review on every tiny change. It is most useful when the cost of missing a bug is high.

Let Claude Code Handle the Feedback

After Codex reports issues, ask Claude Code to fix only the confirmed items:

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Please address the confirmed Codex review findings. Do not refactor unrelated code. Keep the patch scoped and rerun the relevant checks.

Then run tests and optionally ask Codex for a second pass.

Put the Review Checklist in the Project

Teams should not rely on memory. Put a review checklist in a project file, for example:

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## High-risk areas

- Authentication and authorization
- Input validation
- Data migration
- Background jobs
- External API calls
- Error handling and retries

## Required verification

- Relevant unit tests
- Integration or smoke tests when behavior changes
- Manual check for UI changes
- Rollback or migration notes when needed

## Code review

- Findings first
- File and line references
- No speculative rewrites
- Mention missing tests separately

Claude Code can implement against this checklist, and Codex can review against the same checklist.

Be Careful With Automated Gates

Some workflows let Codex block a stop event or a merge when it finds issues. This can be useful, but it can also create loops, false positives, or excessive usage.

Use automatic gates only for narrow rules at first:

secrets accidentally committed;
missing tests for a touched module;
dangerous shell commands;
migrations without rollback notes;
security-sensitive files changed without review.

For broader reasoning, keep a human in the loop.

A Practical Team Flow

Developer asks Claude Code to implement.
Developer runs tests locally.
Codex reviews the uncommitted diff.
Developer confirms which findings are real.
Claude Code fixes the confirmed findings.
Tests run again.
Codex generates or checks the PR summary.
Human reviewer makes the final decision.

This keeps the workflow tight without turning AI review into an unquestioned authority.

Common Mistakes

Mistake 1: Two Agents Edit at the Same Time

This creates merge noise and makes responsibility unclear. Keep one writer and one reviewer.

Mistake 2: The Review Prompt Is Too Vague

“Review this” is weak. Specify correctness, regressions, tests, security, and file references.

Mistake 3: Reviewing Code but Not Tests

Many bugs are really missing-test problems. Ask Codex to call out uncovered behavior.

Mistake 4: Treating AI Review as Final

Codex can find real issues, but it can also misunderstand intent. Human review still matters.

Mistake 5: Not Saving the Rules

If the checklist is only in chat history, the team will forget it. Put it in the repo.

FAQ

Which tool is better for code review?

Use Claude Code for implementation flow and Codex for an independent review pass. The separation matters more than the label.

Does Codex review automatically change code?

It should not if you ask for read-only review. Keep review and repair as separate steps.

Should every PR use adversarial review?

No. Use it for high-risk changes.

Should a review gate be enabled by default?

Usually no. Start with report-only mode, then gate only narrow and reliable checks.

Where should the checklist live?

In the repository: a review doc, agent instruction file, or project convention file.

How should AI review results go into a PR?

Summarize confirmed findings, fixed items, remaining risks, and tests run. Do not paste raw agent output without review.

Summary

The best Claude Code + Codex workflow is not “two agents racing to edit.” It is a loop: one agent implements, the other reviews, the first fixes confirmed findings, and a human makes the final call. That separation gives you better coverage without losing control of the codebase.