trace-multi-agent-systemlisted

# Trace a multi-agent system Multi-agent systems fail in ways single calls do not: an agent hands off bad state, a tool loop never terminates, a sub-agent silently fails and the orchestrator carries on. You cannot debug that from the final output. You need the full tree of who called whom. ## Get the structure right Model the run as a nested span tree: - **One root span** per user request or task. - **One span per agent turn** (which agent, its role, its input state). - **Child spans** for each tool call, retrieval, and LLM call inside that turn. - **Handoff spans / events** when one agent passes control or state to another (record what was passed). Most agent frameworks emit this if you turn on their tracing (LangGraph, CrewAI, AutoGen, OpenAI Agents SDK, LlamaIndex) or add OpenTelemetry instrumentation (OpenLLMetry, OpenInference auto-instrument several agent frameworks). Prefer the framework's built-in tracing, then fill gaps with manual spans (see `instrument-llm-observability`). ## What to capture per agent - **Identity + role** (`agent.name`, `agent.role`) so spans are attributable. - **Input state and output** at each handoff (the #1 source of multi-agent bugs is corrupted or lost state between agents). - **Tool calls** with args + results + errors. - **Loop/iteration count** so runaway loops are visible. - **Tokens + latency + cost per agent** (rolled up to the whole run) so you can see which agent is the expensive/slow one. ## Debug the common failures | Sym