Lifecycle context and host hooks
SessionStart sends the resolved limits, enabled style checks, and escape hatches on startup, resume, clear, and compact, and in Claude Code on fork. SubagentStart sends the same rules. Set context.perTurn to true for reminders on UserPromptSubmit. Configuration errors are reported even when reminders are disabled.
Claude reads hooks/hooks.json, with broad if filters for shell commands. Codex reads hooks/codex.json, which uses command hooks without Claude’s if fields. Both hosts send lifecycle records to the existing monitor, and both show a concise: ... status line while a hook runs.
In Claude Code auto mode, a subagent hands its report back through the SubagentHandback tool. A PreToolUse hook on that tool runs the subagent reply check over the report and denies the handback with the findings, so the subagent revises before the parent sees it. SubagentStop skips Claude’s internal agents, such as prompt suggestions, which arrive with an empty agent_type when the session runs without --agent. Claude hook events
Claude Code filters test output after the command ends. A PostToolUse hook on Bash replaces stdout through updatedToolOutput with the filtered text and empties stderr; the saved log holds both. Claude Code sends only passing runs to PostToolUse, so a failed run keeps its full output. The hook returns no permission decision and never changes the command. Claude PostToolUse decision control
Codex keeps the existing test command rewrite by default. Set testFilter.codexPostToolUse to true to try filtering completed results. The post hook preserves failed output, the exit status, and a path to the available raw output. It uses continue: false feedback so nested code-mode promises can resolve. Direct calls, code-mode calls, and completed background polls must pass live host smoke checks before changing the default. Codex PostToolUse contract
Filtering requires a structured response with an exit status. Codex CLI 0.153.2 sends raw text without that status, so the post hook leaves its output unchanged. Text printed by a test is not treated as exit metadata.