Function registerTask

source code/utils/task/framework.ts:79–119

(task: TaskState, setAppState: SetAppState)

 * Register a new task in AppState.
 */
export function registerTask(task: TaskState, setAppState: SetAppState): void {
  let isReplacement = false
  setAppState(prev => {
    const existing = prev.tasks[task.id]
    isReplacement = existing !== undefined
    // Carry forward UI-held state on re-register (resumeAgentBackground
    // replaces the task; user's retain shouldn't reset). startTime keeps
    // the panel sort stable; messages + diskLoaded preserve the viewed
    // transcript across the replace (the user's just-appended prompt lives
    // in messages and isn't on disk yet).
    const merged =
      existing && 'retain' in existing
        ? {
            ...task,
            retain: existing.retain,
            startTime: existing.startTime,
            messages: existing.messages,
            diskLoaded: existing.diskLoaded,
            pendingMessages: existing.pendingMessages,
          }
        : task
    return { ...prev, tasks: { ...prev.tasks, [task.id]: merged } }
  })

  // Replacement (resume) — not a new start. Skip to avoid double-emit.
  if (isReplacement) return

  enqueueSdkEvent({
    type: 'system',
    subtype: 'task_started',
    task_id: task.id,
    tool_use_id: task.toolUseId,
    description: task.description,
    task_type: task.type,
    workflow_name:
      'workflowName' in task
        ? (task.workflowName as string | undefined)
        : undefined,
    prompt: 'prompt' in task ? (task.prompt as string) : undefined,
  })
}

/**
 * Eagerly evict a terminal task from AppState.