The new rules of context engineering for Claude 5 generation models

Anthropic removed over 80 per cent of Claude Code’s system prompt for the Claude 5 generation with no performance loss, and this post generalises the lessons: rules give way to judgment, worked examples give way to well-designed tool interfaces, everything-upfront gives way to progressive disclosure, and manual memory management gives way to auto-memory. For your own setup: keep CLAUDE.md thin and focused on genuine gotchas, prefer pointing at code (specs, test suites) over describing it, and let skills guide rather than constrain.

Practical vindication of the map-not-manual approach this repo’s AGENTS.md already takes.