PR Guardian

Inspiration

Modern code review tools often struggle with trust. In real-world engineering teams, reviewers are overwhelmed by automated comments that flag unrelated baseline issues, miss subtle logic bugs, or hallucinate problems that don’t exist. This noise slows teams down and erodes confidence in AI-assisted reviews.

PR Guardian was inspired by a simple question: What if an AI code reviewer behaved like a senior engineer — focusing only on what actually changed and backing every claim with reasoning?

What I Learned

Building PR Guardian taught me that the hardest part of applying AI to developer tooling is not generation, but scope control and reliability. I learned how critical it is to constrain model reasoning to the pull request diff itself and to enforce structured outputs so results remain consistent, even for clean PRs. I also gained hands-on experience using Gemini 3 as a reasoning engine, rather than a text generator, which significantly improved determinism and trustworthiness.

How I Built It

PR Guardian is an agentic code review and verification system powered by Gemini 3. The application parses unified git diffs, identifies PR-scoped files, and uses Gemini 3 to reason over those changes with severity-aware classification. The system enforces strict JSON schemas to guarantee consistent output and explicitly separates PR-scoped findings from baseline repository noise. The result is a verification-first review report that can be integrated into CI workflows and delivered directly to both developers and reviewers.

Challenges Faced

One of the biggest challenges was preventing false positives and incomplete outputs. Large language models can easily overgeneralize, so I had to design guardrails that ensure Gemini 3 never attributes baseline issues to a PR and always returns a complete, structured response. Balancing flexibility with determinism was key — and ultimately what made PR Guardian reliable enough to feel like a real engineering tool rather than a demo.

Built With

• gemini3
• html5
• typescript