Multi-Model Code Review: Claude, GPT, and Qwen in One Grid

A single model reviewing a diff is a decent reviewer. Three models reviewing the same diff in parallel is a better reviewer, because the three disagree in useful ways. This tutorial shows you how to wire up a multi-model review pane and actually use it.

The payoff isn't just "catch more bugs." It's that the disagreements are educational. When Claude flags a race condition, GPT shrugs, and Qwen flags a naming issue, you learn something about each model's blind spots. That's worth the setup cost.

Why three models instead of one

Models fail differently. Claude over-explores and can be wishy-washy on clear calls. GPT/Codex commits to a position and misses subtle issues. Qwen is literal and misses contextual clues. These aren't flaws so much as personalities.

When you run all three against the same diff, you get three takes. Issues that all three flag are almost always real. Issues only one flags are often real but partial — they're the interesting cases. Issues that none flag are probably fine, modulo the shared blind spots of current-generation models.

For background on the individual strengths, see Claude vs Codex vs Qwen.

The layout

A 3x1 or 2x2 grid works. I use 2x2:

• Pane 1: Claude Code (Opus or Sonnet). Primary reviewer.
• Pane 2: Codex CLI. Secondary reviewer.
• Pane 3: Qwen Code. Tertiary reviewer.
• Pane 4: Shell. Git diff, run tests, take notes.

See the grid layouts docs for preset details. The multi-model code review use case page has the exact SpaceSpider configuration.

The standard prompt

Each pane gets the same prompt, verbatim. Consistency is the whole point — you want to compare like with like.

Review the diff in the attached context. Flag:
- bugs and likely bugs
- concurrency issues
- security issues
- performance regressions
- naming and readability problems
- missing tests

Be specific. Cite line numbers. Do not rewrite the code; review it.

Paste this into each pane. Then paste the diff. Same diff, same prompt, three reviews.

Getting the diff into all three

A few options depending on your workflow:

Option A: paste the diff. Run git diff main...HEAD in the shell pane, select, paste into each agent pane. Fast, but verbose on large diffs.

Option B: point each agent at the branch. Have each pane open in the same worktree and say "review the current diff against main." The agents run the git command themselves. Slower, but more accurate on large diffs.

Option C: save the diff to a file. git diff main...HEAD > /tmp/review.diff, then have each agent read the file. Clean, but requires file access.

I use Option B for review of ongoing work, Option C for formal PR review.

Reading three reviews

This is the skill. Three reviewers will produce three walls of text; you need a system for reading them.

My system:

1. Triage by agreement. Issues flagged by all three go to the top of the PR. They're almost always real.
2. Investigate disagreements. If Claude says "race condition" and the others don't, go look. Claude is usually right on concurrency; sometimes it's wrong and I need to explain why.
3. Ignore the noise. Qwen will occasionally flag style issues that don't matter. Skim past.
4. Write your own summary. Don't paste the reviews. Synthesize.

The synthesis step is where the real work is. You end up with a review that no single model produced, which is the point.

When they disagree productively

Some concrete disagreement patterns I've seen:

Claude flags, others miss: usually subtle correctness issues. Concurrency, ordering, error handling. Claude is the strongest of the three here. Pay attention.

Codex flags, others miss: usually implementation shortcuts. Missing null checks, naive algorithms, unchecked error returns. Codex has a good eye for "you didn't finish this."

Qwen flags, others miss: often style or convention issues. Sometimes real bugs that were hidden in boilerplate the others glossed over.

All three flag the same thing: it's real. Fix it.

None flag it, but you had a nagging feeling: trust your feeling. Models have shared blind spots.

The hardest case: all three approve, you're unsure

This happens. All three reviewers like the diff, and you still have a feeling something's off. Don't ignore the feeling.

What I do: add a fourth prompt to one pane, something like "What edge cases might this miss?" or "What would break this in production?" Edge-case prompting tends to surface issues that the generic review prompt misses.

If the fourth prompt also comes up clean, ship it and move on. Sometimes the feeling is just caffeine.

A worked example

A recent case: I pushed a diff that refactored a queue consumer. Three-model review:

• Claude: "Potential race if two workers pull the same job." It was right.
• Codex: "Missing null check on job.data." Also right, unrelated to Claude's concern.
• Qwen: "Variable j is unclear; consider job." Real but minor.

I fixed the race condition (Claude's catch), added the null check (Codex's catch), and renamed the variable (Qwen's catch). Three separate improvements from three reviewers. A single-model review would have caught at most two of the three — and on a busy day, just one.

Cost of multi-model review

Three reviewers running on the same diff cost roughly three times what one reviewer costs, minus some savings from not having to re-review the re-reviewed version. In practice it's a modest premium on any given PR.

The cost-benefit is clear for PRs that matter. For trivial PRs, one reviewer is fine. Reserve the three-model review for:

• PRs touching core systems.
• PRs with concurrency or state.
• PRs you're about to merge to main.
• Diffs from junior developers or AI agents (yes, reviewing AI diffs with AI is the move).

For the economics, see cutting your AI coding bill in half.

The comparison table

Use all three for high-stakes review. Use Claude + Codex for medium-stakes. Use just Claude for low-stakes but-you-care review. Use Qwen alone for "does this even parse" smoke checks.

Setup in a grid terminal

The point of the grid is that this setup is click-click-go:

1. Create a space in SpaceSpider pointed at the repo.
2. Pick a 2x2 layout.
3. Assign Claude, Codex, Qwen, and shell to the four panes.
4. Save. Next time, one click brings the whole setup back.

For the onboarding details, see getting started. For more parallel-workflow patterns, see the parallel AI coding workflow.

Key takeaways

Multi-model code review is cheap to set up and catches issues single-model review misses. The three-way disagreement is the feature: it surfaces blind spots, forces synthesis, and produces better reviews than any individual model.

Use the same prompt in each pane. Triage by agreement. Investigate disagreements. Synthesize, don't paste. Reserve for PRs that matter. That's the entire technique.

FAQ

Do I need three separate API keys? Yes, one per provider. Anthropic for Claude, OpenAI for Codex, and either the Qwen hosted API or a compatible endpoint for Qwen. All three can run concurrently.

What if two models agree but I still disagree? Trust your judgment. Models are advisors; you're the decider. Write down the reasoning so you remember it next time.

Can I do this with just two models? Yes, Claude + Codex is the minimum useful pairing. Adding Qwen is marginal but worth it for conventions and cost-cheap extra coverage.