Struct SubagentBridge 

pub struct SubagentBridge {
    pub parent_events: Arc<EventEmitter>,
    pub parent_tool_call_id: ToolCallId,
}

A handle for bridging sub-turn events (spawned internally by a tool) back into the parent session’s event stream.

Holds the parent session’s EventEmitter and the ToolCallId that initiated this tool invocation. Clone is cheap (internally Arc + small string).

Recursive bridging: each layer only prepends its own id

The full ancestor chain is not stored here — it is accumulated incrementally as events bubble upward through each layer’s bridge. The bridge subscriber (e.g., spawn_agent’s bridge_task) at each layer:

• Receives a leaf event from the sub-turn → wraps it as Subagent{ ancestor_path: [parent_tool_call_id], agent_type: <this layer's profile>, inner: leaf };
• Receives an already Subagent (from a deeper layer, already carrying a partial chain) → prepends parent_tool_call_id to the head of its ancestor_path, leaving inner leaf and deeper agent_type unchanged.

Thus after passing through N layers of bridging, ancestor_path is exactly the complete id chain from the top layer down to the leaf. Each layer only needs to know its own hop — this lets frontend, backend, and arbitrary depths share the same logic.

The recursive depth gate is not here — it is functional and must always apply (including in non-observability / test scenarios), so it lives in the separate ToolContext::subagent_depth field rather than in this optional bridge.

Fields

parent_events: Arc<EventEmitter>

Event bus of the parent session. Wrapped crate::event::AgentEvent::Subagent events are emitted here.

parent_tool_call_id: ToolCallId

The tool call ID that spawned this subagent (the corresponding tool span in the parent trace). The bridge prepends this ID, serving as the mount point of this subagent within the parent trace.

Trait Implementations

impl Clone for SubagentBridge

fn clone(&self) -> SubagentBridge

Returns a duplicate of the value.

fn clone_from(&mut self, source: &Self)

Performs copy-assignment from source.