Create Hook

Create Hook

Use when the user wants to add Codex hooks and explains the behavior they want.

Workflow

1. Determine scope.

   • If the user says global, use the personal/home scope.
   • If the user says project, use the repo scope.
   • If scope is missing or unclear, ask: Should this be global or project-scoped?

2. Determine hook type.

   • If the event is missing or unclear, ask which hook they want:
     • SessionStart
     • UserPromptSubmit
     • PreToolUse
     • PostToolUse
     • Stop
   • If the user wants more than one, keep them separate unless they explicitly want shared behavior.

3. Determine behavior.

   • Ask what the hook should do if the intent is not already clear.
   • Prefer the smallest deterministic script that satisfies the request.

4. Write the hook files in the chosen scope.

   • Global: ~/.codex/hooks.json and ~/.codex/hooks/
   • Project: <repo>/.codex/hooks.json and <repo>/.codex/hooks/
   • Keep script paths explicit and relative where practical.

5. Enable the feature flag if the target Codex build still gates hooks.

   • Set [features] codex_hooks = true in the relevant config.toml.

6. Keep the hook output clear.

   • Use statusMessage for a short visible signal.
   • For logging hooks, write to a repo-local or home-local log file.
   • For blocking hooks, return a nonzero exit only when the hook should actually stop the tool.

7. Verify the result.

   • Run a command that should trigger the hook.
   • Confirm the log, output, or blocking behavior matches the requested scope and event.

Practical defaults

• Use PreToolUse for prevention.
• Use PostToolUse for logging, formatting, or test follow-up.
• Use UserPromptSubmit for prompt shaping and injected context.
• Use SessionStart for startup context.
• Use Stop for end-of-turn checks.

Source: am-will/codex-skills → skills/create-hook/SKILL.md