Opik
Open-source LLM observability and evaluation platform for debugging and monitoring AI agents in production.
Pick Opik if you're shipping LLM agents and want open-source tracing, evals, and guardrails you can self-host or run on Comet's free cloud.
Skip it if you only need lightweight prompt logging or you've already standardized on LangSmith/Langfuse and don't want a migration.
Opik is Comet's open-source observability stack for LLM apps and agents. It captures full traces of every prompt, tool call, and intermediate step, then layers on 30+ LLM-as-a-Judge metrics (hallucination, answer relevance, task completion) plus a test-suite runner with plain-text assertions so you can unit-test agents like code. Production features include real-time monitoring, alerting, guardrails for content and PII, and a coding-agent cost dashboard that audits Claude Code and other model spend across engineering teams.
With ~19k GitHub stars, Opik is the credible open-source alternative to LangSmith and Langfuse, and Comet's pedigree in ML experiment tracking shows in the depth of the evaluation tooling. The core platform is free to self-host; a hosted Cloud tier with a no-credit-card free plan plus paid Enterprise SKUs covers teams that don't want to run infra. It's a strong fit for engineering teams already shipping agents who want to own their telemetry pipeline rather than rent it.
Integrations span the usual ecosystem: OpenAI, Anthropic, LangChain, LlamaIndex, LiteLLM, Haystack, and CrewAI, with SDKs for Python and TypeScript. The newer Ollie assistant takes things further by auto-suggesting and implementing fixes from trace data into your repo. Caveats: the dashboard breadth means a learning curve, and the auto-fix layer is still maturing.
Opik is one of the most credible open-source observability options for LLM apps right now, and Comet's evaluation chops make the metrics layer feel serious rather than checkbox. The free tier and self-host story remove almost every adoption excuse for a team that's already building agents.
— The AI Tool Bible editorial team
Pros
- ✅ Fully open-source with permissive self-hosting
- ✅ 30+ built-in LLM-as-a-Judge evaluation metrics
- ✅ Broad SDK and framework integrations (LangChain, LlamaIndex, LiteLLM, CrewAI)
- ✅ Production guardrails plus PII protection out of the box
- ✅ Free Cloud tier with no credit card required
Cons
- ⚠️ Feature surface area is wide; non-trivial onboarding
- ⚠️ Self-hosting at scale still requires real infra work
- ⚠️ Ollie auto-fix agent is newer and less battle-tested
- ⚠️ Cost dashboard is most useful if you're already on Claude Code
Use cases
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