---
title: "Child workflows"
description: "Start a run of another workflow in the same app from a step, and wait for its result."
---

> Documentation Index
> Fetch the complete documentation index at: https://docs.ezghcloud.com/llms.txt
> Use this file to discover all available pages before exploring further.

# Child workflows

`invoke` starts a run of another workflow in the same app as a step, waits for it, and returns
its output. Use it to reuse workflows, and to fan out beyond one run's 1,000 steps.

### TypeScript

```ts
const report = await step.invoke("report", { workflow: buildReport, input: { month: "2026-10" } })
```

`workflow` is a workflow object or its name. A failed child throws `ChildFailed`.
### Go

```go
report, err := workflows.Invoke[Report](ctx, "report", "build-report", ReportInput{Month: "2026-10"})
if errors.Is(err, workflows.ErrChildFailed) { /* … */ }
```
### Python

```python
report = await ctx.step.invoke("report", workflow="build-report", input={"month": "2026-10"})
```

A failed child raises `ChildFailedError`.

- **The child runs in the same app and project.** Its input is JSON, at most 1 MiB.
- **A child starts exactly once:** its run ID is derived from the parent's run ID and the step,
  so a replay of the parent never starts a second child. A child has no run key.
- **A failed child** fails the step with `workflows.child_failed`, whose cause is the child's own
  error. The workflow can catch it.
- **Children nest at most 10 levels deep.** An eleventh level fails the step without retrying.
- **Each child counts as one step** of its parent, toward the 1,000 steps per run.
- **When a parent ends,** whether it completed, failed, was cancelled or timed out, its children
  that are still running are cancelled. Cancelling a parent cancels its children too.
- **Retrying a failed parent** re-examines its children: a child that has since ended delivers its
  outcome, and a failed or cancelled child is retried. See [Retrying runs](/workflows/retrying-runs).

A child is a run like any other, with its own ID, steps and history.

Source: https://docs.ezghcloud.com/workflows/child-workflows/index.mdx