3 rules that cut your CLAUDE.md's token count by 40%. Based on 800+ hours of Claude Code operation.
Your CLAUDE.md is included in every single API turn. A 100-line CLAUDE.md costs ~2,000 tokens per turn. At 20 turns/session × 5 sessions/day, that's 200,000 tokens/day just for instructions.
Measured update (2026-08-10). The framing above overstates the bill. CLAUDE.md sits in the cached prefix, so those tokens are charged at the cache-read rate, not the full input rate. On my own three-layer, 608-line setup, deleting every duplicated rule works out to roughly $0.24–$1.19 per month.
The 40% below is real, but it is 40% off your CLAUDE.md's token count — not 40% off your bill. Shrinking CLAUDE.md is still worth doing, for clarity and rule-following: shorter, checkable instructions get followed more often. It is just not where the money goes. If your bill is the problem, session transcripts are — see the free Token Audit or SERVICES.md.
Before (wasteful):
# Don't use rm -rf # Don't force push to main # Don't commit .env files # Always run tests before committing # Format code with Prettier
5 lines × ~100 tokens = 500 tokens/turn wasted. Hooks and linters already enforce these.
After (efficient):
# Safety handled by hooks (npx github:yurukusa/cc-safe-setup) # Style handled by ESLint + Prettier
2 lines. Same protection. 300 fewer tokens/turn.
Before:
# When writing tests, use descriptive names # Tests should be independent # Mock external services # Test edge cases # Use beforeEach for setup
After:
# Tests: see tests/user.test.ts for patterns
Claude reads the example file when it needs to. Your CLAUDE.md stays small.
What Claude can't figure out on its own:
# DB: PostgreSQL 15 (docker-compose.yml) # API: /api/v2/ prefix, JWT auth # Deploy: GitHub Actions → AWS ECS # Current sprint: auth refactor (see JIRA-1234)
Project-specific context that saves Claude from asking or guessing.
| CLAUDE.md | Tokens/turn | Cache hit rate | Instruction tokens |
|---|---|---|---|
| 100 lines (typical) | ~2,000 | 89% | Baseline |
| 50 lines (trimmed) | ~1,200 | 92% | -20% |
| 35 lines (optimized) | ~800 | 95% | -40% |
Corrected 2026-08-10. The last column used to read "Monthly cost (Max)", which implied a 40% smaller bill. That was wrong. CLAUDE.md rides in the cached prefix, so on my own three-layer, 608-line setup, removing every duplicated rule came to about $0.24–$1.19 per month. The percentages are real as a reduction in instruction tokens — treat the bill impact as small, and shrink CLAUDE.md for clarity and rule-following instead.
CLAUDE.md Analyzer (free) — Paste your CLAUDE.md and see exactly how many tokens it costs per turn. Nothing leaves your browser.
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