Client Backend¶

Per-request HTTP header access for reactive rendering. Wire once in your app's middleware; render() reads X-PJX-Mounted and X-PJX-Assets from the active backend. X-PJX-Trigger is client-only — consumed by pjx.js for loading indicators, not by the server render walk.

PyJinHx does not ship middleware — you define a thin wrapper (see FastAPI integration) that calls Registry.request_scope(client_backend=FastAPIClientBackend(request)).

ClientBackend¶

class ClientBackend(ABC):
    def get_header(self, name: str) -> str | None: ...

    @classmethod
    def current(cls) -> ClientBackend | None: ...

    @classmethod
    def scope(cls, backend: ClientBackend | None) -> ContextManager[None]: ...

    @classmethod
    def reset(cls) -> None: ...

    @classmethod
    def resolve_client(cls, explicit: object | None) -> object | None: ...

Abstract base — implement for non-FastAPI frameworks if needed.

Class method	Purpose
`current()`	Return the active backend for this request, or `None`.
`scope(backend)`	Set the request-scoped backend (usually via `Registry.request_scope`).
`reset()`	Clear the backend. Mainly for tests.
`resolve_client(explicit)`	Return `explicit` if set, else `current()`. Used by `_render()` for asset dedup.

FastAPIClientBackend¶

Defined in pyjinhx.integrations.fastapi:

class FastAPIClientBackend(ClientBackend):
    def __init__(self, request: object) -> None: ...

Default implementation for FastAPI and Starlette. Wraps request.headers. setup(app, ...) wires this automatically in middleware.

Auto-resolution in render()¶

When a ClientBackend is active (via setup() middleware or ClientBackend.scope()):

Root renders use it for asset dedup (X-PJX-Assets) and runtime injection gating (X-PJX-Mounted).
Reactive class/instance render() reads the X-PJX-Mounted manifest for OOB swaps.

Mutation routes call Cls.render(*args) with no framework kwargs — pending keys from @mutates drive the OOB walk.

Without a ClientBackend, reactive OOB is skipped even when mutations are pending — only the primary is rendered.

Non-FastAPI frameworks¶

Subclass ClientBackend and implement get_header(). Pass the instance to Registry.request_scope(client_backend=...).