Claude Code Hook Architect Reference FAQs

Question 1

What is the primary advantage of using Hooks over Skills in Claude Code?

Accepted Answer

Hooks offer a 100% execution guarantee because they are event-based and do not rely on Claude's judgment, whereas Skills or Agents are triggered based on Claude's decision-making, which has variable reliability.

Question 2

Can Claude Code hooks modify tool inputs before they execute?

Accepted Answer

Yes, specifically during the PreToolUse and PermissionRequest events, a hook can return an 'updatedInput' to modify the command or parameters before they are processed.

Question 3

How is session data passed to a hook script?

Accepted Answer

Session data, including session_id, cwd, and transcript_path, is passed to the hook script via stdin in JSON format. Hooks must read stdin (e.g., using cat or jq) to access this data.

Question 4

Which hook event is best for injecting project-specific context?

Accepted Answer

The UserPromptSubmit event is ideal for context injection because any output to stdout during this event is automatically injected into Claude's prompt context.

Question 5

What does Exit Code 2 signify in the hook system?

Accepted Answer

Exit Code 2 acts as a 'Block' or 'Special Action' signal. Its behavior depends on the event; for example, in PreToolUse it blocks execution, while in the Stop event it forces Claude to continue working.

Claude Code Hook Architect Reference

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Key Features

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Claude Code Hook Architect Reference

About

Key Features

Use Cases