settings.json

{
  "hooks": {
    "PostToolUse": [
      {
        "matcher": "Edit|Write",
        "hooks": [
          {
            "type": "command",
            "command": "FILE=$(cat - | jq -r '.tool_input.file_path') && if echo \"$FILE\" | grep -qE '\\.(tsx|ts|jsx|js)$'; then cd \"$CLAUDE_PROJECT_DIR\" && npx eslint \"$FILE\" 2>&1; fi"
          }
        ]
      }
    ]
  }
}