05 — Quiz: hooks

Pick an answer. The quiz checks it and shows the explanation.

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1. Your PreToolUse hook spots rm -rf and exits with code 1. What happens to the call?

a) it's blocked

b) it goes ahead: exit 1 is a non-blocking error

c) you get a permission prompt

d) Claude Code stops the session

b — by default, only exit code 2 (or a JSON deny) blocks. Exit 1 shows an error notice and the call runs.

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2. Your hook prints {"permissionDecision": "deny"} at the top level of its JSON, then exits 0. What happens?

a) the call is blocked

b) the field is ignored, so the normal permission flow continues

c) Claude Code shows a settings error

d) the hook is disabled

b — permissionDecision belongs inside hookSpecificOutput. Fields at the wrong level are silently ignored.

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3. A session runs in bypassPermissions. Your PreToolUse hook denies a command. Does it run?

a) yes: bypass skips every check

b) no: the hook runs before any permission-mode check, so its deny holds

c) only if an allow rule matches

d) you get a prompt instead

b — a hook deny blocks even in bypassPermissions and with --dangerously-skip-permissions.

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4. You want a log line for every successful tool call, without slowing Claude down. Which setup fits?

a) a PreToolUse hook that exits 2

b) a PostToolUse hook with "async": true

c) a deny rule

d) a line in CLAUDE.md

b — PostToolUse runs after a tool succeeds, and async runs it in the background. It observes, it can't block.

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5. You add a hook with matcher mcp__notes to guard every tool of an MCP server named notes. It never fires. Why?

a) hooks can't match MCP tools

b) the server must be restarted

c) a bare server name matches nothing: use mcp__notes__.*

d) MCP tools skip PreToolUse

c — MCP tools are named mcp__<server>__<tool>. Matching a whole server needs the .* part.

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