Langchain is a publication focusing on programming languages, language design, and compiler development. Readers can explore articles covering topics such as language features, syntax design, and compiler optimization techniques. Additionally, they can learn about programming language theory, language implementation challenges, and practical applications of language design principles.

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Agent observability differs fundamentally from traditional software observability because agents are non-deterministic — you can't predict behavior until runtime. This post explains why debugging agents means debugging reasoning rather than code, introduces three core observability primitives (runs, traces, threads), and shows how these primitives map directly to three levels of agent evaluation: single-step (unit tests for decisions), full-turn (end-to-end trajectory), and multi-turn (context persistence across sessions). Production traces serve triple duty: manual debugging, building offline evaluation datasets from real failures, and powering continuous online evaluation. The key insight is that observability and evaluation are inseparable for agents — traces are the only source of truth for what an agent actually did.

Agent Observability Powers Agent Evaluation

From debugging code to debugging reasoning

Agent observability ≠ software observability

How agent observability powers agent evaluation

What this means for teams building agents