chat-start-session-action-typed-client-data.md

@trigger.dev/sdk	patch

Type chat.createStartSessionAction against your chat agent so clientData is typed end-to-end on the first turn:

import { chat } from "@trigger.dev/sdk/ai";
import type { myChat } from "@/trigger/chat";

export const startChatSession = chat.createStartSessionAction<typeof myChat>("my-chat");

// In the browser, threaded from the transport's typed startSession callback:
const transport = useTriggerChatTransport<typeof myChat>({
  task: "my-chat",
  startSession: ({ chatId, clientData }) =>
    startChatSession({ chatId, clientData }),
  // ...
});

ChatStartSessionParams gains a typed clientData field — folded into the first run's payload.metadata so onPreload / onChatStart see the same shape per-turn metadata carries via the transport. The opaque session-level metadata field is unchanged.