Hooks Implementation - Automating Codex Lifecycle Events

Hooks run custom scripts during the Codex lifecycle. They turn checks that might be skipped in natural-language execution into deterministic automation.

Common events

Codex supports events such as SessionStart, UserPromptSubmit, PreToolUse, PermissionRequest, PostToolUse, SubagentStart, SubagentStop, and Stop.

Event	Example
SessionStart	Inspect environment and repository state
UserPromptSubmit	Detect possible credentials in input
PreToolUse	Check policy before a tool call
PostToolUse	Run a lightweight check after changes
Stop	Run lint, links, or report generation

Configuration Locations

Hooks can live in hooks.json next to an active configuration layer or in [hooks] tables in config.toml. Plugins can also bundle them.

[features]
hooks = true

Properties of a Good Hook

Review project Hooks before trusting a repository. A good Hook is fast, deterministic, narrowly scoped, free of secret logging, and clear about failure output.

This repository could run npm run harness:check after harness changes or link validation after content changes. It must not place approval-gated builds or deployments in an automatic Hook.

Adoption Steps

Start with a notification-only Hook, add read-only validation, then tune failure behavior. Matching Hooks can run concurrently, so avoid dependencies on execution order.

Next, MCP and Plugins integration safely expands external capabilities.

See the references for the external specifications and background sources used on this page.[1][2]

References

1. OpenAI, Codex documentation
2. OpenAI, OpenAI API documentation