AI SDK v6 Protocol

Endpoints

• POST /v1/ai-sdk/agents/:agent_id/runs
• GET /v1/ai-sdk/agents/:agent_id/chats/:chat_id/stream (legacy: /runs/:chat_id/stream)
• GET /v1/ai-sdk/threads/:id/messages

Request Model (POST /runs)

AI SDK v6 HTTP uses id/messages.

• id (required): thread id
• messages (required): UI messages array
• parentThreadId (optional)
• trigger (optional): submit-message or regenerate-message
• messageId (required when trigger=regenerate-message)

Example (normal submit):

{
  "id": "thread-1",
  "runId": "run-1",
  "messages": [
    { "id": "u1", "role": "user", "content": "Summarize latest messages" }
  ]
}

Example (regenerate):

{
  "id": "thread-1",
  "trigger": "regenerate-message",
  "messageId": "m_assistant_1"
}

Legacy shape (sessionId + input) is rejected for HTTP v6 UI transport.

Decision Forwarding

Decision-only submissions are extracted from assistant message parts (for example tool-approval-response).

If there is no user input and decisions are present, server first tries to forward decisions to an active run keyed by:

• protocol: ai_sdk
• agent_id
• thread id (id)
• runId

Success response:

{
  "status": "decision_forwarded",
  "threadId": "thread-1"
}

If no active run is found, request falls back to normal run execution path.

Response Transport

Headers:

• content-type: text/event-stream
• x-vercel-ai-ui-message-stream: v1
• x-tirea-ai-sdk-version: v6

Stream semantics:

• SSE frames contain AI SDK UI stream events (start, text-*, finish, data-*, …)
• server appends data: [DONE] trailer

Tool progress is emitted as data-activity-snapshot (activityType = tool-call-progress).

Resume Stream

GET /v1/ai-sdk/agents/:agent_id/chats/:chat_id/stream (legacy: /runs/:chat_id/stream)

• 204 No Content if no active fanout stream exists for agent_id:chat_id
• 200 SSE stream when active

History Endpoint

GET /v1/ai-sdk/threads/:id/messages

Returns AI SDK-encoded message history for thread hydration/replay.

Validation and Errors

• empty id -> 400 (id cannot be empty)
• no user input and no suspension decisions and not regenerate -> 400
• regenerate without messageId -> 400
• regenerate with empty messageId -> 400
• unknown agent_id -> 404

Error body:

{ "error": "bad request: request must include user input or suspension decisions" }