aether_core/events/
observer.rs

1use crate::events::{AgentEvent, TraceContext};
2use std::sync::Arc;
3
4/// Observer of the agent's event stream. Observers receive the same events
5/// the agent sends on its event channel, synchronously and in order —
6/// including events that channel consumers such as UIs and session
7/// persistence filter out downstream.
8pub trait AgentObserver: Send {
9    fn on_event(&mut self, message: &AgentEvent);
10
11    /// Called with the rendered system prompt for the next chat request
12    fn on_system_prompt(&mut self, _prompt: &str) {}
13
14    /// Trace context to propagate to whatever executes `tool_id`, available once
15    fn tool_trace_context(&self, _tool_id: &str) -> Option<TraceContext> {
16        None
17    }
18}
19
20/// Instrumentation for one inbound MCP request, held by the server handling it.
21pub trait McpRequestInstrumentation: Send {
22    /// Context beneath the request, for application work the request spawns.
23    fn trace_context(&self) -> Option<TraceContext>;
24
25    /// Completes the request. `error` is the public operation error, if any.
26    fn finish(self: Box<Self>, error: Option<&str>);
27}
28
29/// Creates observers isolated to one agent or one inbound MCP request.
30pub trait ObserverFactory: Send + Sync {
31    /// A fresh observer for one agent, continuing the parent trace when supplied.
32    fn agent(&self, agent_name: Option<&str>, parent: Option<&TraceContext>) -> Box<dyn AgentObserver>;
33
34    /// Instrumentation for one inbound `tools/call` request.
35    fn tool_call_request(&self, tool_name: &str, parent: Option<&TraceContext>) -> Box<dyn McpRequestInstrumentation>;
36}
37
38pub type DynObserverFactory = Arc<dyn ObserverFactory>;
aether_core/events/observer.rs

aether_core/events/
observer.rs
