- **Tests in Spock (Groovy)**, not JUnit: `src/test/groovy/graphql/`

- **No new dependencies** (firm policy)

- **No wildcard imports**, no inner classes, no `Optional`

- Max 2 indent levels; early returns; extract methods to reduce nesting

- Immutable data classes w/ Builder: `newFoo()` factory, `foo(value)` setters, `transform()` method

- Use `graphql.Assert` not `Objects.requireNonNull`

- Use `@Public`/`@Internal` annotations — never package-private/protected

- `@NullMarked` on all public API classes; `@NullUnmarked` on their Builder classes; use `@Nullable` for nullable params/returns; NullAway enforced via ErrorProne

- Full style guide: `coding-guidelines.md`