Agent instructions that actually change behaviour
My global instruction file for Claude Code has a five-line rule about which model a subagent should run on. It changes how every session spends money, and a short test shows that it does. Most instruction files I read are the opposite: long lists of sensible advice with no visible effect on what the agent actually does. The difference is not clever wording. It is whether each rule sits in a place…
Claude Code's global instruction file can have rules that actually change behavior, as opposed to long lists of advice with no visible impact. These effective rules are placed where they can work, have a trigger, and have been tested. The rules are written as small if-statements, with a trigger, action, and reason.
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