Server-to-agent flows (`AgentChat` SDK class + cli-v3 MCP `start_agent_chat`) were building `triggerConfig.basePayload` without the `trigger: "preload"` and `messages: []` fields the agent runtime branches on. Result: the auto-triggered first run had `payload.trigger === undefined`, neither `onPreload` nor `onChatStart` fired, and `onTurnStart`'s DB-write blew up with PrismaClient "No record found" because no Chat row had been created.
Browser-mediated flows already had this right (`chat.createStartSessionAction` in `ai.ts:6951`); the server-side path now mirrors that shape.
- packages/trigger-sdk/src/v3/chat-client.ts — `AgentChat.ensureStarted` adds the two fields to `basePayload`. `chat-client-test`'s `pong` orchestrator now returns the assistant text instead of an empty string.
- packages/cli-v3/src/mcp/tools/agentChat.ts — same fix on `start_agent_chat`'s `createSession` call. Also drops the redundant separate `apiClient.triggerTask(...)` call: `POST /api/v1/sessions` now auto-triggers the first run and returns its runId, so a second trigger from the MCP would have produced a competing run on the same session. Use `session.runId` from the create response. The `preload` input flag becomes a no-op signal (response message wording only) since session-create always triggers a run now.
Verified end-to-end against local:
- `chat-client-test` orchestrator returns `{ text: "pong" }`
- MCP `start_agent_chat` → `send_agent_message` x2 → `close_agent_chat` succeeds, both turns reuse the same runId
Eric Allam
2639259652