<critical_patterns>

CORRECT (Payload v3 pattern):

typescript
1handler: async (req) => {
2  const data = await req.json()
3  return Response.json({ success: true }, { status: 200 })
4}

Alternative using helper:

typescript
1import { addDataAndFileToRequest } from 'payload'
2
3handler: async (req) => {
4  await addDataAndFileToRequest(req)
5  const data = req.data  // now available
6  return Response.json({ success: true })
7}

CORRECT:

typescript
1return Response.json({ message: 'success' }, { status: 200 })
2return Response.json({ message: 'success' })  // defaults to 200

Error responses:

typescript
1return Response.json({ error: 'Not found' }, { status: 404 })
2return Response.json({ error: 'Unauthorized' }, { status: 401 })

CORRECT:

typescript
1const cookieHeader = req.headers.get('cookie')
2const cookies = parseCookies(cookieHeader)
3const token = cookies.token

CORRECT:

typescript
1handler: async (req) => { ... }
2// or with PayloadRequest type
3handler: async (req: PayloadRequest) => { ... }

WRONG:

typescript
1req.payload.logger.info('User created', { userId: 123 })
2req.payload.logger.error('Failed to save:', error)

CORRECT:

typescript
1req.payload.logger.info({ userId: 123 }, 'User created')
2req.payload.logger.error({ error: String(error) }, 'Failed to save')

For simple messages (no object):

typescript
1req.payload.logger.info('Operation completed')  // This is fine

export const myEndpoint: Endpoint = { path: '/my-endpoint', method: 'post', handler: async (req: PayloadRequest) => { try { const data = await req.json()

  // Access payload
  const result = await req.payload.find({
    collection: 'users',
    where: { email: { equals: data.email } }
  })

  req.payload.logger.info({ count: result.totalDocs }, 'Found users')

  return Response.json({
    success: true,
    data: result
  })
} catch (error) {
  req.payload.logger.error({ error: String(error) }, 'Endpoint failed')
  return Response.json({ error: 'Internal error' }, { status: 500 })
}

} }

</pattern>

</critical_patterns>

<common_errors>
| Error | Cause | Fix |
|-------|-------|-----|
| `req.data is undefined` | Using v2 pattern | Use `await req.json()` |
| `req.cookies is undefined` | Using v2 pattern | Parse from `req.headers.get('cookie')` |
| `res.json is not a function` | Handler has wrong signature | Return `Response.json()` |
| `TS2769: No overload matches` on logger | Wrong argument order | Put object first, message second |
| `Type 'string \| string[]' not assignable` | relationTo can be array | Use `Array.isArray(x) ? x[0] : x` |
</common_errors>

<quick_reference>
```typescript
// Request body
const data = await req.json()

// Response
return Response.json({ data }, { status: 200 })

// Logger
req.payload.logger.info({ key: value }, 'Message')
req.payload.logger.error({ error: String(e) }, 'Error message')

// Handler signature
handler: async (req: PayloadRequest) => { ... }

</quick_reference>

<success_criteria>

• All endpoints use await req.json() for body access
• All responses use Response.json()
• All logger calls have object first, message second
• Handler signature is (req) not (req, res)
• TypeScript compiles without errors </success_criteria>