> ## Documentation Index > Fetch the complete documentation index at: https://docs.langchain.com/llms.txt > Use this file to discover all available pages before exploring further. # Stream a thread run > Start a run on a thread and stream output as server-sent events. The request must use `agent_id`; `assistant_id` is reserved for server-side forwarding and is rejected. ## OpenAPI ````yaml /langsmith/managed-deep-agents-openapi.json post /threads/{threadID}/runs/stream openapi: 3.1.0 info: title: Managed Deep Agents API version: 0.1.0 description: Create, configure, and run Managed Deep Agents. servers: - url: https://api.smith.langchain.com/v1/deepagents security: - apiKeyAuth: [] tags: - name: Agents description: Create and manage Managed Deep Agent resources. - name: Threads description: Create and inspect durable thread state. - name: Runs description: Start runs on Managed Deep Agent threads. - name: MCP servers description: Register MCP servers and store credentials referenced by agent tools. - name: MCP tools description: List tools exposed by registered MCP servers. - name: Auth sessions description: Start and poll OAuth authorization sessions for OAuth MCP servers. paths: /threads/{threadID}/runs/stream: post: tags: - Runs summary: Stream a thread run description: >- Start a run on a thread and stream output as server-sent events. The request must use `agent_id`; `assistant_id` is reserved for server-side forwarding and is rejected. operationId: streamManagedDeepAgentThreadRun parameters: - $ref: '#/components/parameters/ThreadID' requestBody: required: true content: application/json: schema: $ref: '#/components/schemas/StreamRunRequest' examples: basic: summary: Stream updates value: agent_id: 11111111-1111-1111-1111-111111111111 messages: - role: user content: >- Research recent approaches to agent memory and summarize the main tradeoffs. stream_mode: - updates stream_subgraphs: true user_timezone: America/Los_Angeles responses: '200': description: Server-sent event stream. content: text/event-stream: schema: type: string '400': $ref: '#/components/responses/BadRequest' '401': $ref: '#/components/responses/Unauthorized' '403': $ref: '#/components/responses/Forbidden' '404': $ref: '#/components/responses/NotFound' '502': $ref: '#/components/responses/BadGateway' components: parameters: ThreadID: name: threadID in: path required: true description: Thread ID. schema: type: string schemas: StreamRunRequest: type: object required: - agent_id - messages properties: agent_id: type: string format: uuid description: >- Managed Deep Agent ID. The server forwards this upstream as `assistant_id`. messages: type: array minItems: 1 description: Input messages for the run. items: $ref: '#/components/schemas/Message' stream_mode: type: array description: Stream modes to return. items: type: string enum: - values - updates - messages-tuple stream_subgraphs: type: boolean description: Whether to stream subgraph events. user_timezone: type: string description: >- IANA timezone name (for example, `America/Los_Angeles`) for this run. The runtime uses it to inject a localized current-date line into the agent's system prompt, so the agent reasons about dates in the user's local time. Optional. Defaults to the timezone stamped on the agent (or `UTC` if none was set); invalid values fall back to `UTC`. example: America/Los_Angeles additionalProperties: true Message: type: object properties: role: type: string enum: - user - assistant - system - tool content: type: string ErrorResponse: type: object properties: type: type: string code: type: string detail: type: string status: type: integer responses: BadRequest: description: Bad request. content: application/json: schema: $ref: '#/components/schemas/ErrorResponse' examples: missingRequiredField: summary: Required field missing value: type: https://docs.langchain.com/errors/missing_required_field code: missing_required_field detail: 'Set ''name'' to a non-empty string: ''name'' is required' status: 400 invalidRequestBody: summary: Malformed JSON body value: type: https://docs.langchain.com/errors/invalid_request_body code: invalid_request_body detail: >- Provide a valid JSON request body matching the documented schema status: 400 Unauthorized: description: >- Authentication required. The auth layer returns a simple `{"error": "Unauthorized"}` body that does not match the structured `ErrorResponse` shape used by other 4xx responses. content: application/json: schema: type: object properties: error: type: string examples: missingApiKey: summary: No `X-Api-Key` header supplied value: error: Unauthorized Forbidden: description: >- The authenticated identity does not have access to the resource or feature. The auth layer returns a simple `{"error": "Forbidden"}` body that does not match the structured `ErrorResponse` shape used by other 4xx responses. content: application/json: schema: type: object properties: error: type: string examples: invalidApiKey: summary: API key is invalid or lacks workspace access value: error: Forbidden NotFound: description: Resource not found. content: application/json: schema: $ref: '#/components/schemas/ErrorResponse' examples: agentNotFound: summary: Unknown agent ID value: type: https://docs.langchain.com/errors/agent_not_found code: agent_not_found detail: >- Verify the agent ID and that the calling identity has access: agent not found status: 404 BadGateway: description: Upstream agent runtime error. content: application/json: schema: $ref: '#/components/schemas/ErrorResponse' examples: upstreamAuthFailed: summary: >- Upstream runtime rejected the request (e.g. orphaned thread after agent deletion) value: type: https://docs.langchain.com/errors/upstream_auth_failed code: upstream_auth_failed detail: >- Verify that the calling identity is authorized for this organization: upstream agent runtime rejected the request status: 502 securitySchemes: apiKeyAuth: type: apiKey in: header name: X-Api-Key x-default: LANGSMITH_API_KEY ````