Part 6 of a series building a support-ticket agent with no framework. Previous: Part 5 (guardrails). Repo: github.com/akash-pal/agent-from-scratch
"Run the eval set" and "is this agent healthy right now" are different questions, and it's easy to only build infrastructure for the first one. Eval sets run offline, on cases you already thought of. Production traffic doesn't ask permission to send you a ticket type you didn't anticipate. Observability is what tells you when that's happening — and it's also, unglamorously, what makes offline evaluation possible in the first place: you can't debug a failing eval case without knowing what the agent actually did, step by step.
The minimum trace payload
Every tool call in this build logs a structured record — src/trace.ts:
export interface TraceStep {
