Claude Code: Coding Plan

# Method 1: /plan command
> /plan Migrate auth from Session to JWT

# Method 2: Include "plan first" in instruction
> Migrate auth from Session to JWT, plan first then execute

# Method 3: Auto-trigger (large tasks)
> Refactor entire project's error handling

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Coding Plan: Session → JWT Auth Migration
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## Goal
Migrate authentication from Session to JWT

## Impact Scope
- Modified files: 12
- New files: 3
- Deleted files: 2
- DB changes: None

## Execution Steps

### Step 1: Create JWT utility module
- New src/auth/jwt.ts
- Implement token generation, verification, refresh
- Write unit tests

### Step 2: Modify auth middleware
- Modify src/middleware/auth.ts
- Change from Session to JWT verification
- Keep interface unchanged

### Step 3: Modify login/register routes
- Modify src/routes/auth.ts
- Return JWT token instead of setting Session

### Step 4: Modify protected routes
- Modify 8 route files
- Adjust auth check method

### Step 5: Clean up Session code
- Delete session config
- Remove express-session dependency

## Risk Assessment
- 🔴 High: Middleware migration may affect all logged-in users
- 🟡 Medium: Token refresh logic needs careful design
- 🟢 Low: Utility module independent, doesn't affect existing code

## Estimate
- Tokens: ~80K
- Time: ~15 min
- Cost: ~$1.60

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Confirm execution? [y/n/modify]
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> Step 5 doesn't need Session deletion, keep compatibility for 2 weeks

Claude Code:
  Updated plan:
  Step 5: Keep Session compatibility
  - Don't delete express-session
  - Add dual auth support (Session + JWT)
  - Clean up Session code after 2 weeks

  Confirm? [y/n/modify] y
  Starting execution...

[Step 1/5] Create JWT utility module
  → Creating src/auth/jwt.ts
  → Running: npm test -- jwt.test.ts
  ✅ Step 1 complete

/checkpoint "jwt-module-complete"

[Step 2/5] Modify auth middleware
  → Modifying src/middleware/auth.ts
  → Running: npm test -- auth.test.ts
  ✅ Step 2 complete

[Step 3/5] Modify login/register routes
  ✅ Step 3 complete

[Step 4/5] Modify protected routes
  → Running: npm test
  ❌ 3 tests failed
  → Root cause: Some routes depend on req.session
  → Fix: Map JWT payload to req.user in middleware
  → Re-running: npm test ✅

> /plan Migrate entire microservice project from JavaScript to TypeScript

Claude Code generates detailed plan:

## Phase 1: Infrastructure (1-2 hours)
  Step 1: Install TypeScript and type definitions
  Step 2: Create tsconfig.json (loose mode first)
  Step 3: Configure build scripts

## Phase 2: Shared Modules (2-3 hours)
  Step 4: Migrate shared/types/ (5 files)
  Step 5: Migrate shared/utils/ (8 files)

## Phase 3: Service Modules (3-4 hours, parallelizable)
  Step 6: Migrate user-service/ (12 files)
  Step 7: Migrate order-service/ (15 files)
  Step 8: Migrate payment-service/ (10 files)

## Phase 4: Strict Mode (1-2 hours)
  Step 9: Enable strict mode
  Step 10: Fix all type errors
  Step 11: Full test verification

Total: Modify 53 files, New 8 files
Estimate: ~200K tokens, ~$4.00

> Execute by Phase, /checkpoint after each Phase

[Phase 1 complete] /checkpoint "ts-infra"
[Phase 2 complete] /checkpoint "shared-modules"
[Phase 3 complete] /checkpoint "services"
[Phase 4 complete] /checkpoint "strict-mode"

✅ All tests passed, migration complete!