# Get a second-opinion review from a fresh session or another model

> Review the agent's diff in a session that didn't write it, either a fresh Claude Code session or Codex on the PR, and act only on findings that affect correctness.

- **Category:** [Coding](https://stepgleam.com/categories/coding)
- **Difficulty:** Intermediate
- **Time:** ~20 minutes
- **Tools:** Claude Code, Codex
- **Reliability score:** 78/100
- **Steps:** 4
- **Last updated:** 2026-10-26
- **Published:** 2026-10-26

## Tools used

- [Claude Code](https://code.claude.com/docs) — Writes the change; a fresh session or subagent reviews it
- [Codex](https://developers.openai.com/codex) — Optional cross-model review on the GitHub PR

## What you'll get

A review from a reviewer without the author's context, with the correctness issues fixed.

## Who this is for

Developers merging agent-written code.

## Before you start

On r/ClaudeAI, developers who have Claude Code write their code describe two review habits: a second, adversarial session that reads the diff cold, or Codex reviewing the PR. Both rest on the same idea: the reviewer shouldn't be the author.

## Steps

### Step 1: Review in a context that did not write the code

**Tool:** Claude Code

*"Just a second Claude Code session with the diff as context and instructions to be adversarial. Two sessions of the same model catch more than you'd think because the second one doesn't have the sunk-cost bias of having written the code."* Anthropic's guide says the same: *"A fresh context improves code review."*

**Why this works:** The author session is biased toward its own code.

**Prompt:**

```
Review the diff on this branch against PLAN.md. Report only gaps that affect correctness or the stated requirements: missing edge cases, untested paths, changes outside scope. Cite file and line.
```

[Open step 1](https://stepgleam.com/guides/get-a-second-opinion-review-from-a-fresh-session-or-another-model#step-1)

### Step 2: Or ask Codex to review the PR

**Tool:** Codex

Some developers add a different model for the important changes. With the repo connected to Codex, comment `@codex review` on the PR, or turn on automatic reviews in Codex settings; it follows guidance in AGENTS.md. A developer running parallel streams: *"Codex reviewing Opus's work caught things Opus missed on its own."*

**Prompt:**

```
@codex review
```

[Open step 2](https://stepgleam.com/guides/get-a-second-opinion-review-from-a-fresh-session-or-another-model#step-2)

### Step 3: Tell the reviewer what counts as a finding

Anthropic warns: *"A reviewer prompted to find gaps will usually report some, even when the work is sound"*. Tell it to flag only correctness and requirement gaps, and treat the rest as optional.

**Why this works:** Chasing every finding leads to over-engineering.

[Open step 3](https://stepgleam.com/guides/get-a-second-opinion-review-from-a-fresh-session-or-another-model#step-3)

### Step 4: Feed the findings back to the writing session

**Tool:** Claude Code

Paste the review into the session that wrote the code, have it fix the real issues, and re-run the tests. Anthropic's Writer/Reviewer example is exactly this loop.

**Prompt:**

```
Here's the review feedback: <paste>. Fix the correctness issues, skip the style notes, and run the test suite.
```

[Open step 4](https://stepgleam.com/guides/get-a-second-opinion-review-from-a-fresh-session-or-another-model#step-4)

## Pro tips

- Claude Code's bundled /code-review skill reviews the current diff in a fresh subagent.
- Write your review rules in AGENTS.md so Codex follows them.

## Common mistakes

- Asking the session that wrote the code to review it.
- Fixing every nit a reviewer raises.

## FAQ

### Same model or a different one?

One developer argues a fresh context matters more than the model; others add Codex for important changes.

### Does Codex review need setup?

A GitHub repo connected to Codex and code review turned on in its settings.

---

Canonical guide: https://stepgleam.com/guides/get-a-second-opinion-review-from-a-fresh-session-or-another-model
Read this guide as Markdown: https://stepgleam.com/guides/get-a-second-opinion-review-from-a-fresh-session-or-another-model.md