Module 6 · Traces & observability

Every run your agent has ever made was quietly recorded as a trace — a timeline of every LLM call, tool call, and retrieval. This module teaches you to read those traces: what a span is, its anatomy, how to spot the slowest step on a timeline, where latency and cost actually come from, and how to debug a failing run. By the end you can open any run and explain what happened, in order, and why.

1What is a trace?A trace is the recording of everything that happened during one agent run — a tree of spans, where each span is one unit of work with a start time, an end… 5 min

2The anatomy of a spanA span is one unit of work in a trace — it carries a kind (model call, tool call, retrieval, run wrapper), a duration (start to end), a parent (what it… 7 min

3Reading the timelineA trace timeline encodes four things at once: bar length = duration, indentation = parent/child nesting, colour = span kind, position = order. Once you… 6 min

4Where cost and latency come fromAcross almost every run, both latency (how long) and cost (how much) are driven by the same thing: the LLM calls. Tools and retrieval are fast and free in… 6 min

5Debugging with tracesTraces aren't just for speed and cost — they're your debugger. Most agent failures show up as a specific signature in the trace: an error span the answer… 6 min

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