Strawberry GraphQL @ 0.328.2

Released October 2, 2026 at 8:55 AM GMT+00:00

This release fixes objects cast with strawberry.cast not being resolved when they’re returned in a union.

Resolvers can return objects that aren’t instances of a union’s types, like rows of an ORM, by casting them to the type they represent:

@strawberry.type
class Query:
    @strawberry.field
    def latest_media(self) -> Audio | Video:
        return strawberry.cast(Video, db.media.latest())

Casts to a generic type work too, like strawberry.cast(Edge, row) for an Edge[int] member, also when it’s returned through an interface that Edge implements. When more than one possible type is made from the generic class, like Edge[int] | Edge[str] , the cast is ambiguous and Strawberry raises an error, in unions and interfaces alike.

The cast takes precedence over the types’ is_type_of , and a cast that matches none of the possible types, for example a cast to an interface, is ignored, so the object is resolved as before.

This release was contributed by @patrick91 in https://github.com/strawberry-graphql/strawberry/pull/4653