ADK Runtime and Events

The Runner drives one invocation and streams Event objects back turn by turn until completion

ADK Runtime and Events The Runner drives one invocation and streams Event objects back turn by turn until completion run(new_message) append user event run_async(ctx) generate request content + tool_calls yield Event(content) yield Event(tool_call) apply state_delta stream event yield Event(final) invocation done Invocation Event turn Completion Caller · app code · Sequence participant Caller app code Runner · drives invocation · Sequence participant Runner drives invocation Agent · LlmAgent · Sequence participant Agent LlmAgent Model · LLM · Sequence participant Model LLM Session · SessionService · Sequence participant Session SessionService Legend request return security async trace

One entry point

  • • The Runner owns the invocation, not the agent
  • • User input becomes an InvocationContext
  • • History is appended before the agent runs

Events, not returns

  • • The agent yields a stream of Event objects
  • • Content, tool calls, and state deltas are all Events
  • • The caller observes progress turn by turn

State control

  • • state_delta is applied through the SessionService
  • • Control signals mark turn and invocation boundaries
  • • The stream ends on the final Event

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