> ## Documentation Index
> Fetch the complete documentation index at: https://wb-21fd5541-typedoc-upgrade.mintlify.site/llms.txt
> Use this file to discover all available pages before exploring further.

# startSubagent

> TypeScript SDK reference

> **startSubagent**(`opts`): [`SubAgent`](../interfaces/subagent)

Defined in: [src/genai/api.ts:137](https://github.com/wandb/weave/blob/8c5f077eb11c42b84000726ff20504abc728d3fb/sdks/node/src/genai/api.ts#L137)

Start a SubAgent span. Same parent-resolution rules as `startTool`.

## Parameters

### opts

[`SubAgentInit`](../interfaces/subagentinit)

## Returns

[`SubAgent`](../interfaces/subagent)

## Examples

```ts twoslash theme={null}
// @noErrors
weave.startSubagent({name: 'critic'});
```

```ts twoslash theme={null}
// @noErrors
weave.startSubagent({
  name: 'critic',
  model: 'gpt-4o',
  systemInstructions: ['Critique the proposed plan.'],
  startTime: new Date('2026-05-29T10:00:00.000Z'),
});
```