Action

Black-box in

Where the parent feeds this chain

Black-box in marks the single point where a parent workflow's data enters this chain when the chain is reused as a Subworkflow, so you can say exactly where work comes in instead of leaving it to be guessed.

How it works

When you save a chain of steps to reuse as a black box, the parent needs to know where its data should enter. Black-box in is that marker: drop it at the start of the chain and wire it into your first real step, and the parent's input flows in right there.

It is optional. Without it, a black box just uses the chain's ordinary input node. You reach for Black-box in when the entry point isn't obvious, or when the chain has more than one possible starting node and you want to name the one the parent should feed.

The marker does no work of its own and costs nothing. It's a label on the seam between the parent flow and the reusable chain, so both read as one continuous story when a job runs.

Black-box in in a workflow

A simple example of where this node sits in a flow.

Black-box in Where the parent feeds this chain Extract PDFs → structured data Analyze Underwriting pass Black-box out Where this chain returns to the parent

What you set up

  • Add it near the start of a chain you intend to reuse as a Subworkflow.
  • Wire it into the first step that should receive the parent's input.
  • Optionally give the port a name so it's clear on the black-box node in the parent.

Common questions

Do I have to use this?

No. Without it a black box uses the chain's normal input node. Use it when you want to name the entry explicitly or the chain has more than one possible start.

Does it cost anything or slow the job down?

No. It does no work — it's a labelled boundary that passes data straight through, billed at zero.