Subagents

let sub_session = AgentSession::new_subagent(
    "sub-session-id",
    "researcher",
    "Research Helper",
    "Finds information",
    "parent-session-id",  // parent
    "tool_use_123",       // parent tool use ID
)?;

async fn execute(&self, input: &Value, internals: &mut AgentInternals) -> Result<ToolResult> {
    let parent_session = internals.session.session_id().to_string();
    let tool_use_id = internals.context.current_tool_use_id
        .clone()
        .unwrap_or_default();

    // Create subagent session
    let sub_session = AgentSession::new_subagent(
        format!("sub-{}", tool_use_id),
        "researcher",
        "Research Agent",
        "Researches topics",
        &parent_session,
        &tool_use_id,
    )?;

    // Notify parent
    internals.send(OutputChunk::SubAgentSpawned {
        session_id: sub_session.session_id().to_string(),
        agent_type: "researcher".to_string(),
    });

    // Get runtime and spawn
    let runtime = internals.context.get_resource::<AgentRuntime>()
        .ok_or_else(|| anyhow::anyhow!("Runtime not available"))?;

    let config = AgentConfig::new("You are a researcher.");
    let agent = StandardAgent::new(config, self.llm.clone());

    let handle = runtime.spawn(sub_session, |i| agent.run(i)).await;

    // Send task
    handle.send_input("Research this topic").await?;

    // Collect results
    let mut rx = handle.subscribe();
    let mut result = String::new();

    while let Ok(chunk) = rx.recv().await {
        match chunk {
            OutputChunk::TextDelta(text) => result.push_str(&text),
            OutputChunk::Done => break,
            _ => {}
        }
    }

    // Notify completion
    internals.send(OutputChunk::SubAgentComplete {
        session_id: handle.session_id().to_string(),
        result: Some(result.clone()),
    });

    Ok(ToolResult::success(result))
}

match chunk {
    OutputChunk::SubAgentSpawned { session_id, agent_type } => {
        println!("Subagent spawned: {} ({})", session_id, agent_type);
    }

    OutputChunk::SubAgentComplete { session_id, result } => {
        println!("Subagent complete: {}", session_id);
        if let Some(res) = result {
            println!("Result: {}", res);
        }
    }

    _ => {}
}

// Get parent
let parent_id = session.parent_session_id();  // Option<&str>

// Get children
let children = session.child_session_ids();  // &[String]

// Check if subagent
let is_sub = session.is_subagent();

// List only top-level (no subagents)
let top_level = AgentSession::list_top_level()?;

// List all including subagents
let all = AgentSession::list_all()?;

// List with metadata
let with_meta = AgentSession::list_with_metadata(true)?;  // true = top-level only