CLAUDE.md Optimization Guide

Write CLAUDE.md files that maximize Claude's adherence and performance.

Core Principle: Less Is More

Long CLAUDE.md = Claude ignores half of it. Critical rules get lost in noise.

For each line ask: "Would removing this cause Claude to make mistakes?"

If no → delete it
If Claude already does it correctly → delete it or convert to hook

What to Include

Essential (High Value)

| Section | Example | |---------|---------| | Project context | "Next.js e-commerce app with Stripe" (1 line) | | Build/test commands | npm run test, pnpm build | | Critical gotchas | "Never modify auth.ts directly" | | Non-obvious conventions | "Use vi for state, not useState" | | Domain terminology | "PO = Purchase Order, not Product Owner" |

Include Only If Non-Standard

Branch naming (if not feature/, fix/)
Commit format (if not conventional commits)
File boundaries (sensitive files to avoid)

Do NOT Include

Things Claude already knows (general coding practices)
Obvious patterns (detectable from existing code)
Lengthy explanations (be terse)
Aspirational rules (only real problems you've hit)

Structure

# Project Name

One-line description.

## Commands
- Test: `npm test`
- Build: `npm run build`
- Lint: `npm run lint`

## Code Style
- [Only non-obvious conventions]

## Architecture
- [Brief, only if complex]

## IMPORTANT
- [Critical warnings - use sparingly]

Formatting Rules

Bullet points over paragraphs
Markdown headings to separate modules (prevents instruction bleed)
Specific over vague: "2-space indent" not "format properly"
IMPORTANT/YOU MUST for critical rules (use sparingly or loses effect)

File Placement

| Location | Scope | |----------|-------| | ~/.claude/CLAUDE.md | All sessions (user prefs) | | ./CLAUDE.md | Project root (share via git) | | ./subdir/CLAUDE.md | Loaded when working in subdir | | .claude/rules/*.md | Auto-loaded as project memory |

Optimization Checklist

Before finalizing:

[ ] Under 50 lines? (ideal target)
[ ] Every line solves a real problem you've encountered?
[ ] No redundancy with other CLAUDE.md locations?
[ ] No instructions Claude follows by default?
[ ] Tested by observing if Claude's behavior changes?

Maintenance

Run /init as starting point, then prune aggressively
Every few weeks: "Review this CLAUDE.md and suggest removals"
When Claude misbehaves: add specific rule
When Claude ignores rules: file too long, prune other content

Anti-Patterns

| Don't | Why | |-------|-----| | 200+ line CLAUDE.md | Gets ignored | | "Write clean code" | Claude knows this | | Duplicate rules across files | Wastes tokens, conflicts | | Theoretical concerns | Only add for real problems | | Long prose explanations | Use bullet points |

Example: Minimal Effective CLAUDE.md

# MyApp

React Native app with Expo. Backend is Supabase.

## Commands
- `pnpm test` - run tests
- `pnpm ios` - run iOS simulator

## Style
- Prefer Zustand over Context
- Use `clsx` for conditional classes

## IMPORTANT
- NEVER commit .env files
- Auth logic lives in src/lib/auth.ts only

~15 lines. Covers what Claude can't infer. Nothing more.