Why not Celery pydantic=True alone?¶

Celery 5.5+ supports @app.task(pydantic=True). That is useful, but it only covers half the story.

What pydantic=True does¶

On the worker, Celery:

Converts kwargs dicts into Pydantic models using your annotations
Dumps return models to dicts via model_dump() for the result backend

What it does not do¶

On the producer (your API, CLI, or script calling .delay()):

You must still serialize models yourself
Passing OrderCreate(...) directly raises ``TypeError: not JSON serializable`

On the client (calling .get()):

You receive a dict, not your return model

Official docs quote¶

From the Celery task documentation:

Argument validation only covers arguments/return values on the task side. You still have serialize arguments yourself when invoking a task with delay() or apply_async().

Community reports¶

celery#9442 - models not serializable on enqueue
dramatiq#660 - JSON encoder fails on models
arq#497 - request for native Pydantic support

What queuebridge adds¶

Stage	Celery alone	With queuebridge
`.delay(model)`	Fails or needs `model_dump()`	Works
Worker receives	Model (with pydantic=True)	Model (with pydantic=True)
`.get()` returns	`dict`	`dict` (use `typed_result` for model)

queuebridge does not replace Celery’s worker validation. It complements it by fixing producer serialization and offering client-side typed results.