Decide between Claude Code primitives with one rule: Skill teaches the how, Hook enforces the rule, Subagent isolates the work

Professor Glitch·medium signal

As Claude Code accumulates skills, hooks, and subagents, teams keep misusing them interchangeably; the clean decision rule is that a Skill supplies reusable know-how loaded on demand, a Hook deterministically enforces a policy the model can't be trusted to remember, and a Subagent quarantines a focused task in a clean window returning only a 1–2k-token summary. Internalizing this stops builders from, e.g., writing a 'always run tests' instruction into CLAUDE.md (which the model can ignore) when it belongs in a hook.