Glossary · Phase 10 · Agent harnesses
Fail closed
When a safety check itself breaks, block the action instead of allowing it. Failing open allows it.
Try it now
Prompts ask, and hooks enforce.
Learn it properly
Hooks and skills · Extend a harness at lifecycle events, and load know-how on demand. About 35 minutes.
Other terms from the same lesson
- agent skill: A folder that teaches an agent one kind of task: a SKILL.md with a name, a description and instructions, plus scripts and files.
- lifecycle hook: Code a harness runs at a set moment, such as before or after each tool call. It can block, change or add to what happens.
- progressive disclosure: Loading information in stages: a short summary always, details only when a task needs them.
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