Boris Cherny

9/ Use a PostToolUse Hook to Auto-Format Code

Source snapshot: 2026-11-09Independent editorial note

When this pattern helps

Treat this as an extension point with an explicit trigger, inputs, permissions, and failure behavior. Start with a narrow workflow, document prerequisites, and verify the action in a disposable project before making it part of a team routine.

把它当作扩展点来设计：明确触发条件、输入、权限和失败处理。先从窄流程开始，写清前置条件，并在临时项目验证后再纳入团队日常。

Use a PostToolUse hook to format Claude's code. Claude usually generates well-formatted code out of the box, and the hook handles the last 10% to avoid formatting errors in CI later.

"PostToolUse": [
  {
    "matcher": "Write|Edit",
    "hooks": [
      {
        "type": "command",
        "command": "bun run format || true"
      }
    ]
  }
]

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