AgentSpawnTool

Simple subagent tool for agent-internal use. Much lighter than SessionsTool:

• agent_spawn — spawn a subagent, run task, return result (sync or async)

• agent_send — send follow-up message to a previously spawned subagent

• agent_list — list active subagents

No sessions, no lanes, no run registry, no announce dispatch. Just "create agent, invoke, return result". Uses DefaultAgentManager for agent creation and invocation only.

Async tasks (timeout_seconds=0) are submitted to the TaskRepository scoped by the current session ID from RuntimeContext. This makes task state visible in workspace storage for cross-node retrieval and recovery after compaction.

Streaming

agent_spawn and agent_send return Mono``<String> so that the framework's reactive tool-invocation pipeline (see ToolMethodInvoker) can subscribe them within the parent agent's streaming chain. When a SubagentEventBus is present in the Reactor Context (injected by AgentBase.createEventStream), every child io.agentscope.core.agent.Event is forwarded to the parent sink in real time, giving consumers a flattened event stream across the full call hierarchy. When no bus is present (plain call() mode), execution falls back to the non-streaming invokeAgent path with no overhead.