Claude Code: Memory System

Project memory > Personal memory > Session memory
When project CLAUDE.md conflicts with global, project wins.

# Global memory (~/.claude/CLAUDE.md)
"I prefer TypeScript strict mode, functions under 20 lines"

# Project memory (project/CLAUDE.md)
"This project uses JavaScript (not TypeScript), functions up to 50 lines"

# Result: Claude Code generates JavaScript code, functions under 50 lines
# Project memory overrides personal memory

# Claude Code remembers previous conversation within a session

> Create a UserService
[Created]

> Add password reset functionality to it
[Claude Code remembers where UserService is, modifies directly]

> Add email verification too
[Still remembers UserService context]

# After session ends, conversation history is not retained

# Session 1: "I prefer functional programming style"
# Session 2: May generate non-functional code — doesn't remember preference

# Solution: Write preferences into CLAUDE.md

# CLAUDE.md

## Project Conventions (Persistent Memory)
- Use TypeScript strict mode
- API response format: { code, data, message }
- Errors use AppError class
- Test framework: Vitest

## Completed Work (Progress Memory)
- ✅ User authentication module (JWT)
- ✅ Role permission system (RBAC)
- 🔄 Order management module (in progress)
- ❌ Payment integration (not started)

## Technical Decision Records (Decision Memory)
- 2026-08-15: Chose Redis cache over in-memory (need cluster support)
- 2026-08-20: Using Prisma over TypeORM (better type safety)
- 2026-08-25: Amounts use cents integer (avoid floating point errors)

> Remember: Payment module uses Stripe SDK, not direct REST API calls

Claude Code:
  → Updating CLAUDE.md...
  → Added: "Payment integration uses Stripe SDK (not direct REST calls)"

# In later sessions:
> Implement payment refund functionality

Claude Code:
  → [Read from CLAUDE.md] Using Stripe SDK
  → Creating payment.service.ts using Stripe SDK ✅

<!-- ~/.claude/CLAUDE.md -->

## Coding Preferences
- TypeScript strict mode
- Prefer const, avoid let and var
- Functions no longer than 30 lines
- Add JSDoc comments
- Use ES Module

## Testing Preferences
- describe/it style (not test())
- Test naming: should + verb + condition
- Mock external dependencies, not internal modules

## Git Preferences
- Commit format: conventional commits
- Each feature point separate commit

## Dislikes
- ❌ Don't use any type
- ❌ Don't use console.log for debugging
- ❌ Don't ignore TypeScript errors