Delete your CLAUDE.md, skills and hooks after a model upgrade, then add back only what breaks

The problem

CLAUDE.md, skills and hooks accumulate rules written to patch older models. They still load every session, costing tokens and boxing in a model that outgrew them.

The hack

Treat your setup as something to ablate, not to grow. After a model upgrade, delete CLAUDE.md, skills and hooks, work normally, and add a rule back only when Claude repeatedly stumbles on the same thing.

Why it works

Anthropic did exactly this to Claude Code itself: they cut roughly 80% of its system prompt for the newest model without losing coding-eval quality. Boris Cherny, who created Claude Code, recommends the same six-month cycle for user setups.

Setup

1. Commit your current setup so you can restore it. 2. Move `CLAUDE.md`, `.claude/skills/` and your hooks aside (keep hooks that enforce safety, like deny rules and destructive-command blocks). 3. Use Claude Code normally on real tasks for a few days. 4. Note every point where it stumbles. Ignore one-offs. 5. Re-add a rule only for mistakes that repeat, and keep the wording as narrow as possible. 6. Run `/claude-api prompt-audit` to flag remaining instructions written for older models and get the fixes as a diff.

Prompt

Re-read this CLAUDE.md line by line. For each line, ask whether you could have worked it out from the codebase yourself. List the lines you would delete.

Additional details

Source

Related

• → Keep CLAUDE.md under 200 lines so rules actually stick
• → Run /doctor to trim duplicate CLAUDE.md and unused MCP cost
• → Audit for instruction collision between CLAUDE.md, skills and your prompt