> ## Documentation Index > Fetch the complete documentation index at: https://docs.corti.ai/llms.txt > Use this file to discover all available pages before exploring further. # Stream a message (A2A REST) > The `HTTP+JSON` binding of A2A `SendStreamingMessage`. Responds with a `text/event-stream` of `Task`, `statusUpdate`, and `artifactUpdate` events. ## OpenAPI ````yaml /agentic/auto-generated-openapi-v2.yml post /v2/agentic/agents/{agentId}/a2a/message:stream openapi: 3.1.0 info: title: Corti Agent API v2 version: 2.0.0 summary: Manage agents and converse with them over the A2A v1.0 protocol. description: > Version 2 of the Corti Agents REST API. ## What's new in v2 - **Unified `connectors`** — a single, flat, discriminated array replaces the v1 split between `experts`, `mcpServers`, and sub-agents. The envelope is extensible: new connector kinds (`a2a`, `openapi`, `custom`) slot in behind the `type` discriminator without breaking changes. - **Clean CRUD verbs** — `POST` creates, `GET` fetches/lists, `PATCH` performs a *true* partial update, `DELETE` removes. v1's PATCH was effectively a PUT. - **First-class metadata** — `visibility`, `model`, `lifecycle` (now a body field, not a query param), and free-form `labels`. ## A2A v1.0 only The conversational surface speaks **A2A protocol version `1.0` exclusively** (both the `JSONRPC` and `HTTP+JSON` bindings). The deprecated v0.3 binding from v1 is intentionally not carried forward. Per A2A §3.6, clients MUST send the `A2A-Version` header (`Major.Minor`, e.g. `1.0`) on every request to the `/a2a/*` surface, or supply it as the `A2A-Version` query parameter. This surface implements `1.0` only; an absent header is treated as `1.0`. Patch versions MUST NOT be sent. The server echoes the negotiated version in the `A2A-Version` response header. ## Partial updates (PATCH) `PATCH` uses **JSON Merge Patch** semantics (RFC 7386), served under the `application/merge-patch+json` media type: - **Omit a field** → left unchanged. - **`null`** → cleared / reset to its default. - **Arrays** (e.g. `connectors`) → *replaced wholesale*, never merged. To mutate a single connector without replacing the whole array, use the `/connectors` sub-resource endpoints. ## Streaming (Server-Sent Events) The streaming A2A surfaces — `message/stream`, `tasks/subscribe`, and the streaming JSON-RPC methods — respond with `text/event-stream`. The `text/event-stream` media type carries a sequence of Server-Sent Events; the attached schema describes a single event frame. Every event's `data` field is a string carrying a JSON document (`contentMediaType: application/json`); `contentSchema` declares the parsed payload (`StreamResponse` for the `HTTP+JSON` binding, `JSONRPCResponse` for the `JSONRPC` binding). The optional `id` field carries the SSE event id used for resumption via the `Last-Event-ID` request header. contact: name: Corti API Support url: https://corti.ai email: support@corti.ai license: name: Proprietary url: https://corti.ai/terms termsOfService: https://corti.ai/terms servers: - url: https://api.{env}.corti.app description: Corti regional API gateway variables: env: default: eu enum: - eu - us description: Deployment region. security: - bearerAuth: [] tenantHeader: [] tags: - name: Agents description: Create, read, update, and delete agents. - name: Agent Card description: A2A-compliant agent discovery cards. - name: A2A description: Converse with an agent over the A2A v1.0 protocol. - name: Connectors description: Manage the connectors attached to an agent. - name: Usage description: Bucketed invocation history for an agent. - name: Contexts description: Conversational contexts and their tasks. - name: Registry description: Discoverable, pre-built connectors offered by the platform. - name: Artifacts description: Retrieve artifacts produced by tasks. - name: Feedback description: Collect human or automated feedback on tasks and messages. paths: /v2/agentic/agents/{agentId}/a2a/message:stream: parameters: - $ref: '#/components/parameters/AgentId' - $ref: '#/components/parameters/A2AVersionHeader' post: tags: - A2A summary: Stream a message (A2A REST) description: > The `HTTP+JSON` binding of A2A `SendStreamingMessage`. Responds with a `text/event-stream` of `Task`, `statusUpdate`, and `artifactUpdate` events. operationId: A2AStreamMessage requestBody: required: true description: The message to send to the agent. content: application/json: schema: $ref: '#/components/schemas/A2ASendMessageRequest' example: message: messageId: msg.0192f4c8-5f8d-7e61-924d-6fb09b5ead73 role: ROLE_USER parts: - text: What is the ICD-10 code for asthma? responses: '200': description: | An SSE stream of streaming responses. Each event's `data` is a JSON-encoded `StreamResponse` (`Task`, `statusUpdate`, or `artifactUpdate`). headers: A2A-Version: $ref: '#/components/headers/A2AVersion' content: text/event-stream: schema: $ref: '#/components/schemas/A2AStreamEventResponse' example: event: message data: >- {"task":{"id":"task.0192f4c8-4e7c-7d50-b13c-5eaf8a4d9c62","contextId":"ctx.0192f4c8-3d6b-7c4f-a02b-4d9e7f3c8b51","status":{"state":"TASK_STATE_WORKING"}}} '400': $ref: '#/components/responses/A2ABadRequest' '401': $ref: '#/components/responses/A2AUnauthorized' '404': $ref: '#/components/responses/A2ANotFound' components: parameters: AgentId: name: agentId in: path required: true description: Agent identifier (prefixed UUIDv7). schema: $ref: '#/components/schemas/CommonAgentIDValue' A2AVersionHeader: name: A2A-Version in: header required: false description: >- A2A protocol version in `Major.Minor` form (A2A §3.6). Optional; defaults to `1.0` when absent. This surface implements `1.0` only. Patch versions MUST NOT be sent and are not considered during negotiation. schema: type: string pattern: ^\d+\.\d+$ default: '1.0' schemas: A2ASendMessageRequest: type: object description: Request body for sending a message to an agent. required: - message properties: message: $ref: '#/components/schemas/CommonMessage' configuration: $ref: '#/components/schemas/A2ASendMessageConfiguration' metadata: type: object additionalProperties: true description: Free-form request metadata. examples: - requestSource: mobile traceId: trace.abc123 tenant: type: string description: >- Optional. Opaque routing identifier. Must match the `tenant` value from the selected `AgentInterface` in the Agent Card when that field is set. A2AStreamEventResponse: description: An SSE event carrying an A2A `HTTP+JSON` streaming response. allOf: - $ref: '#/components/schemas/A2ASSEEvent' - type: object properties: data: type: string contentMediaType: application/json contentSchema: $ref: '#/components/schemas/A2AStreamResponse' description: 'SSE payload: an A2A HTTP+JSON streaming response.' CommonAgentIDValue: type: string format: agent-id description: >- Agent identifier. Accepts `agt.` or a bare UUIDv7 on input; always returned prefixed. pattern: ^(agt\.)?[0-9a-f]{8}-[0-9a-f]{4}-[0-9a-f]{4}-[0-9a-f]{4}-[0-9a-f]{12}$ examples: - agt.0192f4c8-2c5a-7b3e-9f1a-3c8d6e2b7a40 CommonMessage: type: object description: An A2A message — an ordered list of content parts with a role. required: - role - parts properties: messageId: $ref: '#/components/schemas/CommonMessageIDValue' contextId: $ref: '#/components/schemas/CommonContextIDValue' taskId: $ref: '#/components/schemas/CommonTaskIDValue' role: $ref: '#/components/schemas/CommonRole' parts: type: array items: $ref: '#/components/schemas/CommonPart' description: Ordered content parts of the message. referenceTaskIds: type: array description: >- Task ids this message references (A2A v1.0 `Message.referenceTaskIds`). items: $ref: '#/components/schemas/CommonTaskIDValue' extensions: type: array description: >- URIs of A2A extensions that contributed to this message (A2A v1.0 `Message.extensions`). items: type: string format: uri metadata: type: object additionalProperties: true description: > Free-form A2A metadata. Corti's own first-party keys are prefixed with `$` (à la Mixpanel) to set them apart from caller-supplied keys. A2A defines no message-level timestamp, so Corti carries one as `$timestamp` (RFC 3339 / ISO 8601) — useful for timing *user* messages, which `TaskStatus.timestamp` cannot. examples: - $timestamp: '2026-05-19T12:00:00Z' A2ASendMessageConfiguration: type: object description: Per-request options controlling how a message is processed. required: [] properties: returnImmediately: type: boolean default: false description: >- If `true`, return as soon as the task is submitted, even if processing is still in progress. If `false` (default), wait until the task reaches a terminal (`COMPLETED`, `FAILED`, `CANCELED`, `REJECTED`) or interrupted (`INPUT_REQUIRED`, `AUTH_REQUIRED`) state. historyLength: type: integer minimum: 0 description: Maximum number of prior messages to include as context. acceptedOutputModes: type: array items: type: string description: Output media types the caller accepts. A2ASSEEvent: type: object description: >- A single Server-Sent Event frame (W3C SSE wire format). The server currently writes only `id` and `data` lines; `event` and `retry` are declared for forward compatibility but not sent. required: - data properties: data: type: string contentMediaType: application/json description: SSE payload (JSON-encoded). event: type: string description: Event type. Absent for the default `message` event. id: type: string description: | Opaque event id. Clients echo the most recent value in the `Last-Event-ID` header to resume a dropped stream. retry: type: integer minimum: 0 description: Reconnection time in milliseconds the client should use. A2AErrorResponse: type: object description: | Google-RPC-style error envelope mandated by the A2A `HTTP+JSON` binding. required: - error properties: error: type: object required: - code - status - message properties: code: type: integer description: HTTP status code. status: type: string description: Canonical google.rpc status. examples: - NOT_FOUND message: type: string description: Human-readable error message. details: type: array items: type: object additionalProperties: true description: Additional error details (google.rpc.Status details). description: Google-RPC-style error object with code, status, and message. examples: - error: code: 404 status: NOT_FOUND message: Task not found. details: - '@type': type.googleapis.com/google.rpc.ErrorInfo reason: TASK_NOT_FOUND domain: a2a-protocol.org metadata: taskId: task.0192f4c8-4e7c-7d50-b13c-5eaf8a4d9c62 CommonMessageIDValue: type: string format: message-id description: >- Message identifier. Accepts `msg.` or a bare UUIDv7 on input; always returned prefixed. pattern: ^(msg\.)?[0-9a-f]{8}-[0-9a-f]{4}-[0-9a-f]{4}-[0-9a-f]{4}-[0-9a-f]{12}$ examples: - msg.0192f4c8-5f8d-7e61-924d-6fb09b5ead73 CommonContextIDValue: type: string format: context-id description: >- Context identifier. Accepts `ctx.` or a bare UUIDv7 on input; always returned prefixed. pattern: ^(ctx\.)?[0-9a-f]{8}-[0-9a-f]{4}-[0-9a-f]{4}-[0-9a-f]{4}-[0-9a-f]{12}$ examples: - ctx.0192f4c8-3d6b-7c4f-a02b-4d9e7f3c8b51 CommonTaskIDValue: type: string format: task-id description: >- Task identifier. Accepts `task.` or a bare UUIDv7 on input; always returned prefixed. pattern: ^(task\.)?[0-9a-f]{8}-[0-9a-f]{4}-[0-9a-f]{4}-[0-9a-f]{4}-[0-9a-f]{12}$ examples: - task.0192f4c8-4e7c-7d50-b13c-5eaf8a4d9c62 CommonRole: type: string description: The author of a message. enum: - ROLE_USER - ROLE_AGENT CommonPart: type: object description: A single content part of a message or artifact. required: [] properties: text: type: string description: The string content of the `text` part. data: type: object additionalProperties: true description: >- Arbitrary structured `data` as a JSON value (object, array, string, number, boolean, or null). filename: type: string description: An optional `filename` for the file (e.g., `document.pdf`). mediaType: type: string description: >- The `media_type` (MIME type) of the part content (e.g., `text/plain`, `application/json`, `image/png`). raw: type: string contentEncoding: base64 pattern: ^[A-Za-z0-9+/]*={0,2}$ description: The `raw` byte content of a file. Encoded as a base64 string. url: type: string description: A `url` pointing to the file's content. metadata: type: object additionalProperties: true description: Optional metadata associated with this part. additionalProperties: true headers: A2AVersion: description: >- The A2A protocol `Major.Minor` version the server used to handle the request. schema: type: string examples: - '1.0' responses: A2ABadRequest: description: Malformed A2A request. content: application/json: schema: $ref: '#/components/schemas/A2AErrorResponse' A2AUnauthorized: description: Missing or invalid credentials. content: application/json: schema: $ref: '#/components/schemas/A2AErrorResponse' A2ANotFound: description: The agent, task, or context was not found. content: application/json: schema: $ref: '#/components/schemas/A2AErrorResponse' securitySchemes: bearerAuth: type: http scheme: bearer bearerFormat: JWT description: OAuth 2.0 / OIDC bearer token. tenantHeader: type: apiKey in: header name: Tenant-Name description: The tenant the request operates within. ````