> ## Documentation Index > Fetch the complete documentation index at: https://docs.recoupable.dev/llms.txt > Use this file to discover all available pages before exploring further. # Stream Chat > Streams an agent loop running as a durable [Vercel Workflow](https://vercel.com/docs/workflow) against the session's sandbox. The agent uses sandbox-only tools (`bash`, `read`, `write`, `grep`, `glob`, `todo`, `task`, `ask_user_question`, `skill`, `fetch`) — no MCP or Composio. Requires a sandbox provisioned via [`POST /api/sandbox`](/api-reference/sandbox/create). **Related endpoints** - [`POST /api/chat/runs`](/api-reference/chat/runs) — the **headless** counterpart: it provisions its own session + sandbox and runs without a streaming client. Use that for tasks/cron/programmatic runs; use this for **interactive, streaming** turns on an existing chat. - [`GET /api/chat/{chatId}/stream`](/api-reference/chat/workflow-stream) — reconnect to an in-progress response. - [`GET /api/chat/runs/{runId}`](/api-reference/chat/runs-status) — check **whether** a headless run finished (status, not content). ## OpenAPI ````yaml POST /api/chat openapi: 3.1.0 info: title: Recoup API - Research description: >- API documentation for the Recoup platform - an AI agent platform for the music industry license: name: MIT version: 1.0.0 servers: - url: https://api.recoupable.dev security: [] paths: /api/chat: post: summary: Stream sandbox-driven chat (Vercel Workflow) description: >- Streams an agent loop running as a durable [Vercel Workflow](https://vercel.com/docs/workflow) against the session's sandbox. The agent uses sandbox-only tools (`bash`, `read`, `write`, `grep`, `glob`, `todo`, `task`, `ask_user_question`, `skill`, `fetch`) — no MCP or Composio. Requires a sandbox provisioned via [`POST /api/sandbox`](/api-reference/sandbox/create). **Related endpoints** - [`POST /api/chat/runs`](/api-reference/chat/runs) — the **headless** counterpart: it provisions its own session + sandbox and runs without a streaming client. Use that for tasks/cron/programmatic runs; use this for **interactive, streaming** turns on an existing chat. - [`GET /api/chat/{chatId}/stream`](/api-reference/chat/workflow-stream) — reconnect to an in-progress response. - [`GET /api/chat/runs/{runId}`](/api-reference/chat/runs-status) — check **whether** a headless run finished (status, not content). requestBody: description: Chat workflow request required: true content: application/json: schema: $ref: '#/components/schemas/ChatWorkflowRequest' responses: '200': description: >- Server-Sent Events stream of UI message parts compatible with the Vercel AI SDK `createUIMessageStreamResponse`. The `x-workflow-run-id` response header carries the durable workflow run ID for resume/stop operations. headers: x-workflow-run-id: description: >- Durable workflow run ID. Persist alongside the chat so a later `GET /api/chat/{chatId}/stream` request can resume this run after a disconnect. schema: type: string content: text/event-stream: schema: type: string description: Server-Sent Events stream containing UI message parts '400': description: >- Bad request — missing required fields, invalid body, or sandbox not initialized for the session. content: application/json: schema: $ref: '#/components/schemas/ChatStreamErrorResponse' '401': description: Missing or invalid API key. content: application/json: schema: $ref: '#/components/schemas/ChatStreamErrorResponse' '403': description: >- The API key's account does not own the referenced `sessionId` or `chatId`. content: application/json: schema: $ref: '#/components/schemas/ChatStreamErrorResponse' '404': description: Session or chat not found. content: application/json: schema: $ref: '#/components/schemas/ChatStreamErrorResponse' '409': description: >- A response is already streaming for this chat. Reconnect to it via `GET /api/chat/{chatId}/stream` instead of POSTing again. content: application/json: schema: $ref: '#/components/schemas/ChatStreamErrorResponse' security: - apiKeyAuth: [] components: schemas: ChatWorkflowRequest: type: object description: >- Request body for the sandbox-driven, Workflow-backed chat endpoint. Requires an existing session, chat, and provisioned sandbox. The Bearer key from the `Authorization` header is forwarded into the sandbox for skill-based callbacks to the Recoup API — no separate access-token field needed. required: - messages - chatId - sessionId properties: messages: type: array items: $ref: '#/components/schemas/UIMessage' description: >- Conversation history as an array of `UIMessage` objects, matching the [Vercel AI SDK](https://sdk.vercel.ai/) `UIMessage` shape. The last entry is typically the new user turn — the agent loop reads the entire array and persists the latest user message before the workflow starts. chatId: type: string format: uuid description: >- UUID of an existing chat under `sessionId`. The chat's `active_stream_id` column is used for compare-and-set race control across concurrent requests. sessionId: type: string format: uuid description: >- UUID of the session that owns both the chat and the sandbox. The session must have a non-null `sandbox_state` — call [POST /api/sandbox](/api-reference/sandbox/create) first if not. context: type: object description: Optional per-prompt context overrides forwarded into the agent loop. properties: contextLimit: type: integer description: >- Upper bound on the number of tokens / messages of conversation history the agent should consider for this prompt. Overrides the model's default for this call only. ChatStreamErrorResponse: type: object required: - status - message properties: status: type: string enum: - error description: Status of the request message: type: string description: Error message describing what went wrong UIMessage: type: object description: >- A message in the chat conversation. See https://ai-sdk.dev/docs/reference/ai-sdk-core/ui-message for details. properties: id: type: string description: Unique identifier for the message role: type: string enum: - user - assistant - system description: The role of the message sender content: type: string description: The text content of the message securitySchemes: apiKeyAuth: type: apiKey in: header name: x-api-key description: Your Recoup API key. [Learn more](/quickstart#api-keys). ````