# Hook Authoring > Writing hooks for the 8 hook points, execution modes, and decision semantics Use when this capability is needed. - Skill: `tomevault-io/hook-authoring` (Agent Skill, multi-file: 2 files) - Install (CLI): `npx skillmds@latest add tomevault-io/hook-authoring` - Raw SKILL.md: https://api.skillmd.com/api/skills/tomevault-io/hook-authoring/raw - Safety review: pending (external: skill-scanner PASS, skillspector PASS) - Works with: Claude Code, Claude.ai, OpenAI Codex - Category: Coding & Dev Tools - Author: tomevault-io (https://skillmd.com/u/tomevault-io) - Updated: 2026-09-17 - Page: https://skillmd.com/skills/tomevault-io/hook-authoring --- # Hook Authoring ## Hook Points Meerkat provides 8 hook points in the agent lifecycle: 1. **RunStarted** — When the agent run begins 2. **PreLlmRequest** — Before sending to the LLM 3. **PostLlmResponse** — After receiving LLM response 4. **PreToolExecution** — Before executing a tool call 5. **PostToolExecution** — After tool execution completes 6. **TurnBoundary** — At the boundary between turns 7. **RunCompleted** — When the agent run completes successfully 8. **RunFailed** — When the agent run fails ## Execution Modes - **Foreground**: Blocks execution, can modify/deny. Use for policy enforcement. - **Background**: Runs concurrently, fire-and-forget. Use for logging, analytics. - **Observe**: Receives events but cannot block. Use for monitoring. ## Decision Semantics Hooks return one of: - **Allow**: Proceed normally - **Deny**: Block the operation with a reason - **Rewrite**: Modify the operation (e.g., rewrite tool arguments) ## Patch Format For `PreToolExecution`, hooks can rewrite tool arguments using JSON patches. ## Failure Policy - **fail-closed**: Hook failure blocks the operation (safer) - **fail-open**: Hook failure allows the operation (more resilient) --- > Converted and distributed by [TomeVault](https://tomevault.io/claim/lukacf) — claim your Tome and manage your conversions.