Definition
Trace
A trace is one complete agent run: the user's input, every reasoning step, retrieval, tool call, and the final answer, captured as a single top-level record. It is the unit of AI observability, borrowed from OpenTelemetry's distributed tracing. When a customer gets a wrong answer, you open the trace and walk its spans to find whether retrieval, reasoning, or hallucination failed.
Explained in
Chapter 13: Production AI: Deployment, Monitoring, and Evaluation
The reality of running AI agents. It's nothing like the demo.
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