Opik (Comet)

Opik is one of the most comprehensive open-source observability platforms we've seen, especially for agentic workflows. Its ability to trace every step of an agent—from user input to context retrieval to tool calls—sets it apart from simpler LLM monitoring tools. The inclusion of Llama-as-a-judge metrics out of the box saves teams significant setup time. When to pick this: You’re developing complex agentic systems (e.g., multi-step reasoning, tool-using agents) and need deep traceability across dev, test, and prod. You value open-source flexibility and want to avoid lock-in. The Ollie coding assistant is a unique productivity booster for fixing failing traces. When to pass: If you only need basic prompt monitoring without agent tracing, simpler tools like LangFuse or Helicone might be easier to get started with. Opik’s feature set can feel overwhelming for simple chatbots. Also, if your team prefers a fully managed SaaS without self-hosting, the Comet cloud version adds costs beyond the free tier. Comparison to closest alternative: vs. LangSmith (LangChain): Opik is more focused on agentic tracing with built-in test suites and Ollie auto-fix—LangSmith excels in prompt management and LLM chain visibility but lacks Opik’s code-level remediation. vs. Weights & Biases Prompts: W&B is stronger for experiment tracking and model registry; Opik wins in production monitoring and guardrails. Real-world usage caveats: The platform is relatively new, so documentation and community support are still growing. Some advanced features (e.g., prompt optimizer) may require experimentation to tune. Self-hosting requires Kubernetes or Docker knowledge for scale.

Opik by Comet is an open-source AI observability and evaluation platform purpose-built for the agentic era. It logs every step your agent takes—from user interactions and context retrieval to tool calls—and provides automated evaluation workflows to find and fix errors across development, testing, and production. With end-to-end tracing, LLM-as-a-judge metrics, and production monitoring, Opik helps developers and enterprise teams understand what their agents are doing, where they’re failing, and how to fix them. Key features include comprehensive trace and debug capabilities that capture, visualize, and annotate every action your agent takes. Opik offers 30+ evaluation metrics for answer relevance, context precision, task completion, hallucination detection, and more. It supports automated test suites with plain-text assertions that produce clear pass/fail results, eliminating the need for manual eval creation. The platform also includes Ollie, a coding assistant that analyzes traces, suggests fixes, and directly implements them in your codebase with version control and regression testing. Opik’s Agent Playground lets you run your entire agent end-to-end, experimenting with different configurations of models, prompts, and parameters. The Prompt Optimizer offers six advanced prompt optimization algorithms to improve agent performance. For production, Opik provides real-time monitoring, guardrails to block content violations and PII exposure, and token usage/cost tracking. It generates audit logs automatically for governance and compliance. Opik is truly open-source—its core observability and evaluation features are free in the source code available on GitHub (19k stars). You can run it locally or use Comet’s hosted version with a generous free tier (no credit card required). Compared to proprietary alternatives like LangSmith or Weights & Biases Prompts, Opik offers deeper agentic tracing, built-in code fixing via Ollie, and a stronger open-source community.