Great question. In Prefect 3.x with a Docker work pool: - If you call a subflow directly (e.g.,

child_flow()

inside

parent_flow()

), the subflow runs in the same process and the same container as the parent. It creates a nested flow run in the UI but does not provision new infrastructure. - If you trigger a child via a deployment (e.g.,

run_deployment("child/deploy-name", ...)

), it creates a separate flow run that is picked up by a worker. With a Docker work pool, that means a new container will be started for the child run. By default it appears as a subflow in the UI (

as_subflow=True

), but it’s still a separate container. Helpful links: - Run deployments from a flow (run_deployment) - Serving flows with Docker workers - Workflow design patterns and subflows If you want everything to stay in one container, call the child flow directly. If you want isolation/parallelism or different infra for children, use

run_deployment

. Happy to share a small example if helpful.