> ## 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. # Subscribe to task events (A2A REST) > Resubscribe to an in-flight task's event stream over SSE. ## OpenAPI ````yaml /agentic/auto-generated-openapi-v2.yml post /v2/agentic/agents/{agentId}/a2a/tasks/{taskId}:subscribe 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/tasks/{taskId}:subscribe: parameters: - $ref: '#/components/parameters/AgentId' - $ref: '#/components/parameters/TaskId' - $ref: '#/components/parameters/A2AVersionHeader' post: tags: - A2A summary: Subscribe to task events (A2A REST) description: Resubscribe to an in-flight task's event stream over SSE. operationId: A2ASubscribeTask responses: '200': description: >- An SSE stream of task events. Each event's `data` is a JSON-encoded `StreamResponse`. The server writes event ids but does not yet read the `Last-Event-ID` request header, so resumption without gaps is not implemented. headers: A2A-Version: $ref: '#/components/headers/A2AVersion' content: text/event-stream: schema: $ref: '#/components/schemas/A2AStreamEventResponse' example: id: task.0192f4c8-4e7c-7d50-b13c-5eaf8a4d9c62 data: >- {"statusUpdate":{"taskId":"task.0192f4c8-4e7c-7d50-b13c-5eaf8a4d9c62","contextId":"ctx.0192f4c8-3d6b-7c4f-a02b-4d9e7f3c8b51","status":{"state":"TASK_STATE_COMPLETED","timestamp":"2026-05-19T12:00:01Z"}}} '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' TaskId: name: taskId in: path required: true description: Task identifier (prefixed UUIDv7). schema: $ref: '#/components/schemas/CommonTaskIDValue' A2AVersionHeader: name: A2A-Version in: header required: false description: >- A2A protocol version in `Major.Minor` form (A2A §3.6). Optional; defaults to `1.0` when absent. This surface implements `1.0` only. Patch versions MUST NOT be sent and are not considered during negotiation. schema: type: string pattern: ^\d+\.\d+$ default: '1.0' headers: A2AVersion: description: >- The A2A protocol `Major.Minor` version the server used to handle the request. schema: type: string examples: - '1.0' schemas: 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 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 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 responses: 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. ````