Parallel

system/parallel — Execute a branch once per item and then continue after join.

Where it appears

The Parallel block lives in the Logic & control group of the Workflow Builder.

Field	Type	Required	Default	Description
`items`	text (multi-line, supports references)	Yes	—	The array fanned out across branches — one branch runs per element. Accepts a literal JSON array or a <PreviousStep.field> reference to an upstream array output.
`maxBranches`	text (supports references)	No	—	Hard cap on total branches. Items beyond this index are skipped — useful as a safety net when the input array could be unexpectedly large. Default: 100.
`concurrency`	text (supports references)	No	—	How many branches run at the same time. Subsequent branches start as in-flight branches finish, until all branches complete. Lower this to throttle downstream APIs. Default: 5.
`joinPolicy`	select	No	`allSuccess`	How the join after the branches behaves. All Success only continues past the join if every branch succeeded; Always continues regardless of branch failures. Options: `allSuccess`, `always`.

Inputs are the configurable fields above. The block produces these outputs:

Outputs

Reference an output downstream with <Parallel.field>.

Name	Type	Description
`items`	array	Items iterated over
`branches`	number	Number of branches executed

A minimal configuration for this block:

{
  "type": "system/parallel",
  "config": {
    "items": "<PreviousStep.field>",
    "joinPolicy": "allSuccess"
  }
}

Required field (items) must be set, or the block fails validation before it runs.