Module telemetry 

TelemetryHook — maps the agent’s lifecycle Event stream onto structured tracing spans and events, so a run becomes observable in any tracing subscriber.

Why tracing and not a hard OpenTelemetry dependency? Because tracing is the idiomatic Rust instrumentation seam: the library emits spans + events, and the binary chooses the exporter. Attach tracing-opentelemetry with an OTLP pipeline and every span below is exported to Jaeger / Tempo / any OTLP backend with zero changes here; attach tracing_subscriber::fmt().json() and you get newline-delimited JSON for log pipelines. One instrumentation, many backends.

Span/event shape (target harness.telemetry):

agent_run (span, fields: source)
  ├─ run.start
  ├─ iter            (iter)
  ├─ model.complete  (input_tokens, output_tokens, cached_input_tokens, tool_calls, stop)
  ├─ tool.call       (tool, ok, duration_ms)
  ├─ sensor          (sensor, signals)
  ├─ compact         (stage)
  ├─ budget.warning  (ratio)
  └─ run.end

Wire it like any hook:

let loop_ = AgentLoop::new(model).with_hook(std::sync::Arc::new(TelemetryHook::new()));

Structs

TelemetryHook

Emits a span per run and a structured event per model call, tool call, sensor, compaction, and budget warning. See the module docs for the OTLP bridge.