---
title: "Subscribe to A2A v0.3 task updates"
method: POST
path: "/v2/agents/{agent_key}/v1/tasks/{task_id}:subscribe"
tags: ["A2A Protocol"]
---

# Subscribe to A2A v0.3 task updates

`POST /v2/agents/{agent_key}/v1/tasks/{task_id}:subscribe`

Attaches to a running task and streams subsequent lifecycle updates as Server-Sent Events. If the task is already terminal, streams the final task and closes.

## Path parameters

- `agent_key` string, required — A unique key that identifies an agent.
- `task_id` string, required

## Headers

- `Request-Timeout` integer
- `Request-Timeout-Millis` integer

## Response `200`

A stream of `A2aV03StreamResponse` events.

## Other responses

- `404` — Task not found.

---

[API](https://skmtc.net/vectara/apis/vectara-rest-api-v2.md) · [All operations](https://skmtc.net/vectara/apis/vectara-rest-api-v2/llms.txt) · [OpenAPI document](https://skmtc-service-staging.skmtc.workers.dev/v1/apis/vectara/vectara-rest-api-v2/versions/e85040b266cc/schema)