Stream Accumulation

Anvia streams deltas while also accumulating the final assistant message, tool calls, usage, and history.

1. Render Deltas Immediately

let text = "";

for await (const event of agent.prompt("Write a reply.").stream()) {
  if (event.type === "text_delta") {
    text += event.delta;
    render(text);
  }
}

Use deltas for live UI updates.

2. Use the Final Event for State

for await (const event of agent.prompt("Write a reply.").stream()) {
  if (event.type === "final") {
    await saveMessages(event.messages);
    await saveUsage(event.usage);
  }
}

Use the final event for durable application state. It contains the completed output and the message history created by the run.

3. Tool Calls Are Accumulated Across Deltas

Providers can stream tool call names and arguments in chunks. Anvia buffers those chunks and emits a normalized tool_call event when the call is complete.

for await (const event of agent.prompt("Add 2 and 5.").stream()) {
  if (event.type === "tool_call") {
    console.log(event.toolCall.function.name);
    console.log(event.toolCall.function.arguments);
  }
}

After tool execution, Anvia emits tool_result and continues the run with the next model turn.

4. Reasoning Deltas Are Preserved

When a provider exposes reasoning deltas, Anvia streams them as reasoning_delta events and includes the accumulated reasoning content in the final assistant message.

for await (const event of agent.prompt("Think through this.").stream()) {
  if (event.type === "reasoning_delta") {
    debugPanel.append(event.delta);
  }
}

Keep user-facing UI focused on text_delta unless your product intentionally exposes reasoning content.