# Band + LangSmith / Arize

They observe the model. Band governs the interaction.

## What is LangSmith / Arize?
LangSmith (by LangChain) and Arize are LLM observability and governance platforms. They trace individual LLM calls, track token usage and costs, run evaluations, and help debug prompt performance. They operate at the model layer.

## Where LangSmith / Arize fits

### LLM Call Tracing
Tracing individual LLM calls with token counts, latency metrics, and cost tracking per invocation.

### Prompt Debugging
Debugging and optimizing prompt performance with side-by-side comparisons and regression detection.

### Evaluations
Running offline and online evaluations to measure model accuracy, relevance, and output quality over time.

### Model Monitoring
Continuous monitoring of model performance, drift detection, and alerting on degraded outputs.

## They govern LLM calls.   Band governs agent interactions.
Observability platforms operate at the model layer, tracing individual LLM invocations. Band operates at the agent interaction layer, governing how agents discover, delegate, and collaborate. Different layers, complementary.

## Capability comparison

| Capability | LangSmith / Arize | Band |
| --- | --- | --- |
| Layer | LLM / model | Agent interaction |
| Traces | Individual LLM calls | Delegation chains |
| Multi-agent | No | Core capability |
| Agent registry | No / partial | Yes |
| Crash recovery | No | Yes |
| Loop prevention | No | Yes |
| Cross-framework | Instrumentors | Deep adapters |
| Multi-tenancy | User / team | 3-tier agent-level |

## Bottom Line
Use LangSmith or Arize to observe your models.   Use Band to govern how your agents interact.