claude-code - 💡(How to fix) Fix [BUG] Agent hook on PreToolUse fails with "Messages are required for agent hooks" [1 comments, 2 participants]

Error: Messages are required for agent hooks. This is a bug.

TL;DR

The agent hook error is likely due to a missing messages field in the hook configuration, which is required for agent hooks.

Guidance

• Verify that the messages field is present in the hook configuration, as indicated by the error message.
• Check the documentation for the minimum required fields for an agent hook configuration.
• Consider adding a messages field to the hook configuration, even if it's just an empty array, to see if it resolves the issue.
• Review the hook configuration for any other potential issues or missing fields.

Example

{
  "hooks": {
    "PreToolUse": [
      {
        "matcher": "Bash",
        "hooks": [
          {
            "type": "agent",
            "if": "Bash(git commit:*)",
            "timeout": 120,
            "model": "claude-sonnet-4-6",
            "statusMessage": "Checking spec files...",
            "prompt": "Run git diff --cached --name-only and report what files are staged.",
            "messages": []  // Add this field to the configuration
          }
        ]
      }
    ]
  }
}

Notes

The error message explicitly states that messages are required for agent hooks, suggesting that this is the root cause of the issue. However, without further documentation or context, it's unclear what the messages field should contain or how it should be configured.

Recommendation

Apply workaround: Add a messages field to the hook configuration, as shown in the example above, to see if it resolves the issue. This is a minimal change that can help determine if the error is indeed caused by the missing field.