> ## Documentation Index
> Fetch the complete documentation index at: https://fastql.vachagan.dev/llms.txt
> Use this file to discover all available pages before exploring further.

# Resolvers

> Implement synchronous and asynchronous field resolution.

Resolvers can be regular or async methods. FastQL inspects their annotations to
build GraphQL arguments and inject framework values.

```python theme={null}
from fastql import Field, Query


@Query
class QueryRoot:
    @Field
    async def user(self, id: str) -> User | None:
        return await repository.find_user(id)
```

At execution time, sibling fields are scheduled concurrently. Resolver exceptions
become GraphQL errors with field paths; unaffected nullable branches continue.

The resolver source is the parent object. Root classes are instantiated for the
operation. Ordinary parameters become GraphQL arguments unless FastQL classifies
them as `Info`, `Context`, or registered dependencies.

Use explicit `Arg` metadata to rename, document, deprecate, or default an argument:

```python theme={null}
@Field
def users(self, limit: int = Arg(default=20, description="Maximum rows.")) -> list[User]:
    return repository.list_users(limit=limit)
```