Beta Managed Agents Start Event Preview
BetaManagedAgentsStartEventPreview = BetaManagedAgentsAgentMessagePreview or BetaManagedAgentsAgentThinkingPreviewBetaManagedAgentsAgentMessagePreview objecttype: "agent.message"id: stringThe id the buffered agent.message will carry if it is emitted. Matches the event_id on this preview's event_delta events.
BetaManagedAgentsAgentThinkingPreview objecttype: "agent.thinking"id: stringThe id the buffered agent.thinking will carry if it is emitted. Start-only — no event_delta events follow.