Function start

apps/sim/app/api/mothership/execute/route.ts:242–348

(controller)

      const stream = new ReadableStream<Uint8Array>({
        start(controller) {
          let forwardedAssistantContent = ''
          const send = (event: unknown) => {
            if (!cancelled) {
              controller.enqueue(encodeNdjson(event))
            }
          }

          // Flush response headers promptly and keep long headless runs from
          // looking idle to worker/proxy HTTP stacks.
          send({ type: 'heartbeat', timestamp: new Date().toISOString() })
          heartbeatId = setInterval(() => {
            send({ type: 'heartbeat', timestamp: new Date().toISOString() })
          }, MOTHERSHIP_EXECUTE_HEARTBEAT_INTERVAL_MS)

          void (async () => {
            try {
              const result = await runLifecycle(async (event) => {
                if (
                  event.type === MothershipStreamV1EventType.text &&
                  event.payload.channel === MothershipStreamV1TextChannel.assistant &&
                  event.payload.text
                ) {
                  const text = event.payload.text
                  const content = text.startsWith(forwardedAssistantContent)
                    ? text.slice(forwardedAssistantContent.length)
                    : text
                  if (content) {
                    forwardedAssistantContent += content
                    send({ type: 'chunk', content })
                  }
                }
              })
              allowExplicitAbort = false

              if (lifecycleAbortController.signal.aborted) {
                send({ type: 'error', error: 'Sim execution aborted' })
                return
              }

              if (!result.success) {
                logger.error(
                  messageId
                    ? `Mothership execute failed [messageId:${messageId}]`
                    : 'Mothership execute failed',
                  {
                    requestId,
                    workflowId,
                    executionId,
                    error: result.error,
                    errors: result.errors,
                  }
                )
                send({
                  type: 'error',
                  error: result.error || 'Sim execution failed',
                  content: result.content || '',
                })