How We Taught AI Agents to See the Bigger Picture

AI agents writing code for large legacy codebases tend to repeat outdated patterns because they mistake frequency for correctness. The JetBrains TeamCity team tackled this by building CommitAtlas, an internal tool that mines Git history to extract accepted patterns, naming conventions, and migration examples. Before writing code, agents query CommitAtlas for task-specific guidance derived from real, reviewed commits rather than raw codebase frequency. This approach reduced pull request rejections and helped agents produce code that fits the project's evolving standards rather than its historical defaults. The core insight: repository history is implicit documentation, and giving agents access to it bridges the gap between technically correct and genuinely acceptable code.