Claude Code hooks: fixed checks around flexible agent work
Use hooks for deterministic controls, not as a hidden collection of scripts nobody understands.
In short
- Hooks provide deterministic behaviour at named events.
- Validate every input and design useful failures.
- Combine hooks with permissions and review.
On this page
Why hooks exist
A language model chooses from context; a hook runs a fixed program at a specific moment. That makes hooks suitable for formatters, policy checks, notifications and blocks that should not depend on interpretation.
Choose the right moment
First identify the risk: before a tool action, after a change or when work finishes. An early check can prevent damage; a late check can assess the complete outcome.
Make input and outcomes explicit
Treat hook data as untrusted input. Validate paths and values, use predictable exit codes and return a short error with a recovery action. A silent failure is harder to manage than a clear block.
Keep security layered
A hook alone is not full protection: configuration can change and scripts can be flawed. Combine hooks with narrow permissions, sandboxing, repository protection and human approval for high-impact actions.
No. A prompt rule guides model behaviour; a hook executes a program at an event.
Protect performance and privacy
A frequently executed hook should not slow the session. Avoid needless network traffic, never log prompts or secrets and set a short timeout. Measure the slowest paths.
Roll out small and visibly
Start with one check in warning mode, inspect false positives and assign ownership. Block only when the rule is stable and document how a legitimate exception is requested.
{"hooks":{"PreToolUse":[{"matcher":"Bash","hooks":[{"type":"command","command":"./scripts/check-command.sh"}]}]}}
Make Claude Code hooks verifiable
The decision review for Claude Code hooks first focuses on one PreToolUse or PostToolUse check with validated input, explicit exit codes and a short timeout. Define the acceptable user outcome, essential inputs and authorised approver for Claude Code hooks before the trial starts. Keep the first Claude Code hooks trial small enough to separate causes from effects.
Build evidence for Claude Code hooks around one realistic successful route and also simulate an untrusted path, sensitive data in logs and a slow check with recurring false positives. For every Claude Code hooks check, record the expected outcome, visible evidence and recovery action when it fails. The final decision question for Claude Code hooks is: “Is a hook the same as a prompt rule?”
Claude Code hooks: from trial to everyday operation
Assign Claude Code hooks one operational owner, one subject reviewer and a clear fallback route. Treat the Claude Code hooks checklist as separate evidenced steps, so punctuation or phrasing never becomes part of the process logic. Ask the relevant user to complete Claude Code hooks without spoken help and record every point that still needs explanation or manual recovery.
Keep change rights, logging, support and review dates for Claude Code hooks in one operating plan. Repeat the Claude Code hooks trial after a change to source data, configuration, model, integration or user role. Expand Claude Code hooks only when the team can also detect, contain and recover an untrusted path, sensitive data in logs and a slow check with recurring false positives.
Stop the Claude Code hooks rollout while an untrusted path, sensitive data in logs and a slow check with recurring false positives is not reported visibly and recoverable by the assigned owner.
Creagrid / actie
Practical checklist
Tie each hook to one risk.
Validate paths and payloads.
Set timeouts.
Keep sensitive data out of logs.
Test success, failure and exception paths.
FAQ
Frequently asked questions
Is a hook the same as a prompt rule?
No. A prompt rule guides model behaviour; a hook executes a program at an event.
Should every check block work?
No. Start with observation or warnings where possible, then block after reliable validation.
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