Two coding agents reviewing each other's work — the pattern that catches everything

Your coding agent writes clean code. It follows patterns. It adds tests. But it still ships bugs you could have caught in five seconds.

The problem isn't intelligence — it's perspective. One agent writing and reviewing its own code is like proofreading your own email. You know what you meant to write, so you miss what you actually wrote.

The solution is dual-agent code review. Two agents, different roles, reviewing each other's work before anything ships.

Here's the pattern that works:

• Agent A (Builder): Writes the code, focuses on implementation
• Agent B (Reviewer): Reviews the code, focuses on problems
• Both agents see the original requirements
• Neither agent sees the other's internal reasoning

The key is giving them different incentives. Builder gets rewarded for working code. Reviewer gets rewarded for finding issues.

Critical: Don't let them collaborate. Collaboration turns into groupthink. You want tension, not consensus.

The review checklist that actually catches things:

REVIEWER_CHECKLIST = {
  "edge_cases": "What breaks this code?",
  "error_handling": "What happens when this fails?", 
  "performance": "What happens at scale?",
  "security": "What's the attack surface?",
  "maintenance": "What breaks when requirements change?",
  "integration": "What assumptions does this make about other systems?"
}

I run this pattern on every feature now. Builder writes the code, Reviewer tears it apart. If Reviewer finds nothing, I'm suspicious — good code has at least three things worth discussing.

The workflow:

• Builder implements the feature
• Builder writes tests and documentation
• Reviewer gets: requirements + code + tests (no implementation notes)
• Reviewer writes a review report
• If issues found: Builder fixes and resubmits
• If clean: Ship it

Last week, Builder wrote a data processing function. Clean code, good tests, handled the happy path perfectly. Reviewer immediately spotted that it would crash on empty datasets and had no rate limiting for the API calls.

Builder was focused on making it work. Reviewer was focused on making it break. Both perspectives caught what the other missed.

The setup cost is real but worth it: Two agents means double the API calls for code review. But catching bugs in review costs way less than catching them in production.

The pattern works because it mirrors how the best engineering teams actually work — different people, different perspectives, healthy tension about what ships.

Your coding agent is already smart enough to write good code. Give it a sparring partner that's smart enough to find the problems.