OtelTracingMiddleware

Middleware that adds OpenTelemetry tracing to the agent lifecycle.

Produces spans for:

• invoke_agent <name> — wraps the entire reply

• chat <model> — wraps each model API call

• execute_tool <name> — wraps each tool execution

Model-call spans report input/output token usage and the available cache, reasoning, and tool-prompt token breakdowns using GenAI semantic-convention attributes. The tool-prompt breakdown uses an AgentScope-specific attribute because it is not yet defined by the GenAI convention.

Context propagation across Reactor's asynchronous chain (including thread hops via publishOn / subscribeOn) is handled by ContextPropagationOperator The global lift hook is registered once on class load, so child spans see the correct parent regardless of which thread the signal lands on.

When no OTel SDK is configured (only the default no-op provider is active), every hook short-circuits with near-zero overhead.

Usage:

`ReActAgent agent = ReActAgent.builder()
.name("assistant")
.model(model)
.middleware(new OtelTracingMiddleware())
.build();
`