The Parallel container runs its blocks for multiple items or instances concurrently. Use it when the work is independent; use Loop when iterations must run in sequence.
Process tasks in batches
Name the container Process Tasks and distribute a task array. The inner API reads <parallel.currentItem>. After every batch finishes, the Function reads <processtasks.results>.
Configuration
| Setting | Behavior |
|---|---|
| Parallel Count | Run a configured number of copies of the contained flow. |
| Parallel Each | Distribute an array or object across instances. |
| Parallel Batch Size | Concurrent branches, from 1 to 20; default 20. |
Counts or collections larger than Parallel Batch Size run in serial batches. Lower Parallel Batch Size for rate-limited APIs. A Wait within each branch spaces that branch's work, but does not impose a global request rate across all branches or runs.
References and outputs
Inside the container:
| Reference | Value |
|---|---|
<parallel.index> | Instance index, starting at 0 |
<parallel.currentItem> | Current item, for collection-based execution |
<parallel.items> | Full collection, for collection-based execution |
Arrays yield their values as currentItem. Objects yield [key, value] pairs, so <parallel.currentItem[0]> is the key and <parallel.currentItem[1]> is its value.
After completion, use the container's normalized name: <processtasks.results>. Generic <parallel.*> references select an enclosing parallel context, not a completed container outside it.
Results retain input/instance order, even when branches finish out of order. Each entry contains that branch's block outputs. For a single API per branch, read a field with <processtasks.results[10][0].data.id>. Indexed paths hydrate oversized entries only when needed.
State and failures
Each branch has its own item, index, and block outputs. Workflow variables are shared across branches; they are not an isolated per-branch store.
Avoid concurrent writes to the same workflow variable. An unhandled branch error fails the run and stops new work from starting, though already-running branches may finish. Connect an error path inside the container when other items should continue.
An empty collection skips the body and returns empty results. Parallel and Loop containers can nest in either direction; use the reference picker to select the intended scope.
Parallel or Loop
| Behavior | Parallel | Loop |
|---|---|---|
| Execution | Concurrent within each batch | Sequential |
| Completion order | Can differ from input order | Iteration order |
| Result order | Input/instance order | Iteration order |
| Use when | Each item can stand alone | Later iterations depend on earlier work |
A Parallel can compare the same prompt across several models or call an API for each record. Bound concurrency and collection size according to provider limits and the workflow's execution budget.