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12 — Streaming

Watch every token, tool call, and agent event in real time.

What this shows

  • wire_event_queue() — wire all agents to a single async queue that emits StreamEvents
  • AnsiRenderer — built-in terminal renderer that prints events with colours as they arrive
  • How strands-compose turns agent lifecycle events into a consumable stream — the same mechanism that powers SSE endpoints, WebSocket feeds, and audit logs

How it works

from strands_compose import load, AnsiRenderer

resolved = load("config.yaml")
queue = resolved.wire_event_queue()

resolved.wire_event_queue() installs an EventPublisher hook on every agent. As the agent runs, the hook converts lifecycle events (tokens, tool calls, completions) into StreamEvent objects and pushes them to the queue. Your consumer loop is simple:

renderer = AnsiRenderer()
while (event := await queue.get()) is not None:
    renderer.render(event)
renderer.flush()

Event types

Type When it fires
agent_start Agent begins processing
token Streaming text chunk
reasoning Streaming reasoning chunk
tool_start Tool call begins
tool_end Tool call finished
complete Agent finished (includes token usage)
node_start / node_stop Swarm / Graph enters/leaves a node
handoff Swarm transfers control

Good to know

This example is async. Streaming requires asyncio — the agent runs via invoke_async so both the agent and the queue consumer share the same event loop.

AnsiRenderer is optional. It's a convenience for terminals. In production you'd consume the queue and convert events to SSE chunks (see OpenAIStreamConverter) or NDJSON (RawStreamConverter).

queue.flush() resets the queue between turns so events from one invocation don't leak into the next.

Prerequisites

  • AWS credentials configured (aws configure or environment variables)
  • Dependencies installed: uv sync

Run

uv run python examples/12_streaming/main.py

Try these prompts

  • Analyse the impact of large language models on software engineering.
  • Research current trends in renewable energy adoption.
  • Examine how remote work has changed urban real-estate markets.

Advanced topic — suppress default callback logging

Strands agents log actions to the console through their default callback_handler. If you want cleaner example output, set the handler to null in agent_kwargs for any agent:

agents:
  my_agent:
    agent_kwargs:
      callback_handler: null # or ~