Streaming

Streaming delivers incremental thinking and typing tokens as the agent processes — letting your application render live feedback before the final response is complete.

What streaming provides

As an agent works through a request, it produces two kinds of incremental output:

Both arrive through the standard "message" event on a task, alongside the final polled messages.

Streaming is automatic

The SDK enables and manages streaming for you. There’s no configuration step. When a task is subscribed to (via addEventListener), the SDK opens a streaming connection if one is available. Token refresh, reconnection, and cleanup are handled internally.

Streaming works across every supported runtime: browsers, Node.js, Deno, Bun, and Cloudflare Workers.

Listen for streaming events

Streaming messages arrive through the same "message" event used for every other message type. Identify them with the isThinking and isTyping type guards:

task.addEventListener("message", ({ detail }) => {
  const { message } = detail;

  if (message.isThinking()) {
    console.log("[thinking]", message.text);
  }

  if (message.isTyping()) {
    process.stdout.write(message.text);
  }
});

Both ThinkingMessage and TypingMessage expose a text property with the incremental content.

Build a live typing indicator

A common pattern is rendering the agent’s response in real time as it’s generated. Accumulate typing tokens into a buffer and render them as they arrive:

let buffer = "";

task.addEventListener("message", ({ detail }) => {
  const { message } = detail;

  if (message.isTyping()) {
    buffer += message.text;
    renderPartialResponse(buffer);
  }

  if (message.isAgent()) {
    // Final response arrived; replace the buffer
    buffer = "";
    renderFinalResponse(message.text);
  }
});

The typing tokens represent the same content that will eventually appear in the final AgentMessage. Once the final message arrives, replace the accumulated buffer with the complete response.

Thinking vs. typing

Thinking and typing are different phases of the agent’s processing.

• Thinking happens while the agent reasons about what to do next, which tools to call, or how to structure its response. You might show this as a “thinking...” indicator, display it in a debug panel, or ignore it entirely.
• Typing happens as the agent generates its actual response text. This is the content that ends up in the final agent message.

task.addEventListener("message", ({ detail }) => {
  const { message } = detail;

  if (message.isThinking()) {
    showThinkingIndicator(message.text);
  }

  if (message.isTyping()) {
    appendToResponse(message.text);
  }
});

Streaming lifecycle

Streaming follows the same lifecycle as task subscriptions:

• Start — when the first event listener is added to a task, the SDK subscribes and opens a streaming connection if available.
• Active — thinking and typing tokens arrive through the "message" event as the agent processes. Connection health and token refresh are managed transparently.
• End — when task.unsubscribe() is called, the streaming connection is closed along with the polling loop.

There’s no separate subscription or connect step for streaming. It’s part of the standard task subscription and follows the same cleanup rules described in Tasks.