Anthropic cut 80% of Claude Code's system prompt for the Claude 5 models and published what should still go in your CLAUDE.md and skills

TL;DR: most hard rules are gone ("never write comments" etc), they rely on the model's judgment now. Examples in tool descriptions constrain the new models more than they help. Instead of front-loading everything into one CLAUDE.md they recommend a tree of files that load when needed. Also there's a