BaseUIWorker

BaseUIWorker extends BaseWorker with client visibility. Every job group it dispatches streams its lifecycle to the client as ui-job-group envelopes, so background work appears as a progress card the user can watch and cancel. It involves no LLM. Instantiate one directly and register it on the runner as a dispatcher when a pipeline app wants client-visible background work driven by its own tools:

from pipecat.pipeline.job_context import JobGroupParams
from pipecat.workers.base_ui_worker import BaseUIWorker

ui_jobs = BaseUIWorker("ui-jobs")

async def research(params: FunctionCallParams, query: str):
    job_id = await params.worker_runner.get_worker("ui-jobs").request_job_group(
        "wikipedia", "news",
        params=JobGroupParams(payload={"query": query}, label=f"Research: {query}"),
    )
    await params.result_callback({"status": "started", "job_id": job_id})

Choosing a worker

	Class
Work the client shouldn’t see	`BaseWorker`
Client-visible work, dispatched by the main pipeline’s LLM	`BaseUIWorker`
Client-visible work, plus an LLM that reads and drives the page	`UIWorker`

UIWorker inherits from BaseUIWorker, so it keeps this behavior and adds an LLM with the screen in context. Reach for it when the work depends on what the user is looking at; a BaseUIWorker dispatcher is enough when the main pipeline’s LLM already decides what to run.

What reaches the client

A group dispatched by a BaseUIWorker publishes:

Envelope	When
`group_started`	At dispatch, carrying the group’s workers, `label`, and `cancellable`
`job_update`	As each worker sends an intermediate update
`job_completed`	As each worker responds
`group_completed`	At group teardown — normal completion, cancellation, or timeout

The client’s reserved __cancel_job_group event is translated into a cancellation for any group dispatched with JobGroupParams(cancellable=True). A group dispatched without it is still reported to the client, but the client cannot stop it.

Dispatching

BaseUIWorker uses the same job API as BaseWorker — job_group(), request_job_group(), and create_job_group_and_request_job(). There is no separate UI-specific dispatch method: every group this worker dispatches is client-visible by virtue of the class. Give the group a label. It titles the card the user sees, and without one the card has nothing to name the work:

async with self.job_group(
    "wikipedia", "news", "scholar",
    params=JobGroupParams(
        payload={"query": query},
        label=f"Research: {query}",
        cancellable=True,
    ),
) as jg:
    results = await jg.wait()

Job hooks

The same hooks as BaseWorker — on_job_update, on_job_response, on_job_stream_end, and on_job_completed — with the client forwarding layered on top. Always call super() when overriding, or the client stops receiving the group’s lifecycle.

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Choosing a worker

What reaches the client

Dispatching

Job hooks

​Choosing a worker

​What reaches the client

​Dispatching

​Job hooks

Choosing a worker

What reaches the client

Dispatching

Job hooks