Skills, plugins, subagents, and context isolation
Extensions and subagents scale only when each worker's context, authority, and evidence remain explicit and evaluable.
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The ideas to retain
1. Four primitives, four different questions
There is no universal semantics for skill, plugin, subagent, or hook across products. Start with the function each one performs in a specific implementation.
2. A skill is reusable expertise, not a security boundary
Anthropic Agent Skills provides a current, concrete example. A skill is a directory containing SKILL.md, instructions, and optionally code and reference material. The mechanism uses…
3. Progressive disclosure lowers initial context cost, not activation cost to zero
A skill must be discoverable before it can be selected. That creates two different costs:
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