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DocumentationFeaturesSub-Workflows

Sub-Workflows

Execute workflows within other workflows using @InjectWorkflow() and .run(). The parent workflow pauses at a wait: true transition until the sub-workflow completes.

Injecting a Sub-Workflow

import { InjectWorkflow, CallbackSchema, QueueResult } from '@loopstack/common';
 
@InjectWorkflow() private subWorkflow: SubWorkflow;

Running a Sub-Workflow

@Initial({ to: 'sub_started' })
async start() {
  const result: QueueResult = await this.subWorkflow.run(
    { prompt: 'Hello' },                    // Args passed to the sub-workflow
    {
      alias: 'subWorkflow',                  // Identifier for this instance
      callback: { transition: 'onSubComplete' },  // Method to call when done
    },
  );
 
  // Track with a link document
  await this.repository.save(LinkDocument, {
    label: 'Running sub-workflow...',
    workflowId: result.workflowId,
  }, { id: `link_${result.workflowId}` });
}

Receiving the Callback

The sub-workflow’s @Final return value is passed as payload.data:

const SubWorkflowCallbackSchema = CallbackSchema.extend({
  data: z.object({ message: z.string() }),
});
 
@Transition({
  from: 'sub_started',
  to: 'sub_done',
  wait: true,
  schema: SubWorkflowCallbackSchema,
})
async onSubComplete(payload: { workflowId: string; data: { message: string } }) {
  // Update the link document
  await this.repository.save(LinkDocument, {
    label: 'Sub-Workflow',
    status: 'success',
    workflowId: payload.workflowId,
  }, { id: `link_${payload.workflowId}` });
 
  // Use the result
  await this.createChatMessage.call({
    role: 'assistant',
    content: `Sub-workflow said: ${payload.data.message}`,
  });
}

Sub-Workflow Output

The sub-workflow defines its output as the return value of its @Final method:

@Workflow({ uiConfig: __dirname + '/sub.ui.yaml' })
export class SubWorkflow extends BaseWorkflow {
  @Initial({ to: 'end' })
  async run(): Promise<{ message: string }> {
    return { message: 'Hi mom!' };
  }
}

Complete Example

@Workflow({ uiConfig: __dirname + '/parent.ui.yaml' })
export class ParentWorkflow extends BaseWorkflow {
  @InjectTool() private createChatMessage: CreateChatMessage;
  @InjectWorkflow() private subWorkflow: SubWorkflow;
 
  @Initial({ to: 'sub_started' })
  async runWorkflow() {
    const result: QueueResult = await this.subWorkflow.run(
      {},
      { alias: 'subWorkflow', callback: { transition: 'subWorkflowCallback' } },
    );
 
    await this.repository.save(
      LinkDocument,
      {
        label: 'Executing Sub-Workflow...',
        workflowId: result.workflowId,
      },
      { id: `link_${result.workflowId}` },
    );
  }
 
  @Final({
    from: 'sub_started',
    wait: true,
    schema: CallbackSchema.extend({ data: z.object({ message: z.string() }) }),
  })
  async subWorkflowCallback(payload: { workflowId: string; data: { message: string } }) {
    await this.repository.save(
      LinkDocument,
      {
        label: 'Sub-Workflow',
        status: 'success',
        workflowId: payload.workflowId,
      },
      { id: `link_${payload.workflowId}` },
    );
 
    await this.createChatMessage.call({
      role: 'assistant',
      content: `Message from sub-workflow: ${payload.data.message}`,
    });
  }
}

Registering Sub-Workflows

Both workflows must be registered in the module:

@Module({
  imports: [LoopCoreModule],
  providers: [ParentWorkflow, SubWorkflow],
  exports: [ParentWorkflow, SubWorkflow],
})
export class MyModule {}

To hide the sub-workflow from the Studio sidebar:

@Workspace({ config: { title: 'My Workspace' } })
export class DefaultWorkspace implements WorkspaceInterface {
  @InjectWorkflow() parentWorkflow: ParentWorkflow;
 
  @InjectWorkflow({ options: { visible: false } })
  subWorkflow: SubWorkflow;
}

Registry References

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