Cannot query field "username" on type "User"

The field doesn’t exist in the GraphQL schema.

Fix 1: Check the schema

# Check what fields are available
type User {
  id: ID!
  name: String!    # ← It's "name", not "username"
  email: String!
}

Fix 2: Fix the query

# ❌ Wrong field name
query {
  user(id: "1") {
    username
  }
}

# ✅ Use the correct field
query {
  user(id: "1") {
    name
  }
}

Fix 3: Use introspection

{
  __type(name: "User") {
    fields {
      name
      type { name }
    }
  }
}

Related: REST vs. GraphQL — Which API Style Should You Use?