Flow controls

Unfold

Apply a transformation recursively under explicit stopping bounds.

Unfold repeatedly applies one deterministic or semantic Transform to generated values in the same Space. Use it for bounded recursive expansion, not for an ordinary linear pipeline.

expand = SemTransform(
    name="expand-topic",
    input_spaces=("topics",),
    output_space="topics",
    primary_key="topic",
    prompt=(
        "Return the immediate subtopics as children. Return an empty list when "
        "the topic should not be divided further."
    ),
    emits=("children",),
    provider="openai",
    model="gpt-5",
    reasoning_effort="low",
)

Unfold(
    name="expand-topic-tree",
    body=expand,
    emits="list",
    field="children",
    stop=Stop(max_depth=4, max_nodes=500),
)

Parameter	Default	Meaning
`body`	required	A Transform or SemTransform whose input and output Space match.
`emits`	list	Whether each expansion returns a list or one next value.
`field`	children / next	The output field containing generated values.
`stop.sentinel`	none	Optional leaf token that ends one branch.
`stop.max_depth`	10	Maximum recursive depth.
`stop.max_nodes`	unlimited	Maximum generated values across the expansion.

Bound recursive work

Always choose depth and node limits that match the expected output. These limits protect the session from an unexpectedly expansive transformation and make cost expectations reviewable.