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Open source LLM observability tools in 2026

Trace prompts, model calls and agent steps, and track cost, latency and output quality of AI applications. This list has 11 LLM observability tools. Of these, 11 are open source, 11 have a free plan and 11 can be self-hosted. Checked by hand on 30 September 2026.

  1. 1

    AgentOps

    Observability for AI agents: records agent sessions with LLM calls, tool use and costs so you can replay and debug runs; SDK and app are open source.

    Free plan Open source (MIT) Self-hosted LLM and AITraces
  2. 2

    Future AGI

    Open source platform to trace, evaluate, simulate and guard LLM and agent apps, including an AI gateway.

    Free plan Open source (Apache-2.0) Self-hosted LLM and AITraces
  3. 3

    Helicone

    Open source LLM proxy and logging: point your provider base URL at it to record every request with cost, latency and user, plus caching and rate limits.

    Free plan Free: 10,000 requests, 1 GB storage, 1 seat Open source (Apache-2.0) Self-hosted maintenance LLM and AI
  4. 4

    Laminar

    Open source observability for AI agents: OpenTelemetry-based tracing, evaluations and analysis of agent runs, self-hostable or cloud.

    Free plan Free: 1 GB data, 7-day retention, 1 seat Open source (Apache-2.0) Self-hosted LLM and AITracesOpenTelemetry
  5. 5

    Langfuse

    Open source LLM engineering platform: traces LLM and agent calls, manages prompts, runs evaluations and tracks cost and latency. Self-host or use the cloud; acquired by ClickHouse in 2026.

    Free plan Free: 50k units/mo, 30 days data access, 2 users Open source (MIT) Self-hosted LLM and AITracesOpenTelemetry
  6. 6

    LangWatch

    Open source LLMOps platform: traces LLM and agent runs, runs evaluations and agent simulations, and helps optimize prompts; cloud or self-managed.

    Free plan Free: 50k events/mo, 14-day data access, 2 users Open source (Apache-2.0) Self-hosted LLM and AITracesOpenTelemetry
  7. 7

    Latitude

    Open source platform to trace, monitor and evaluate AI agents in production, with prompt management; self-host or use the hosted plans.

    Free plan Free: 20K credits/mo, 30-day retention Open source (MIT) Self-hosted LLM and AITraces
  8. 8

    OpenLIT

    Open source, OpenTelemetry-native AI observability: SDK auto-instruments LLMs, vector databases and GPUs, with a self-hosted UI for traces, costs, evals and prompts.

    Free Open source (Apache-2.0) Self-hosted LLM and AITracesOpenTelemetry
  9. 9

    OpenLLMetry

    Open source OpenTelemetry instrumentations for LLM providers, vector databases and agent frameworks, by Traceloop; sends traces to any OTLP backend or the Traceloop platform.

    Free plan Free: Traceloop: 50K spans/mo, 5 seats, 24h retention Open source (Apache-2.0) Self-hosted LLM and AITracesOpenTelemetry
  10. 10

    Opik

    Open source LLM and agent observability from Comet: tracing, test suites, evaluations and a prompt optimizer; self-host the same code as the cloud.

    Free plan Free: 25k spans/mo, 10 members, 60-day retention Open source (Apache-2.0) Self-hosted LLM and AITraces
  11. 11

    PostHog

    Open source product suite with session replay, product analytics, feature flags, error tracking and LLM analytics sharing one event store. Hosted with a monthly free allowance, or self-hosted.

    Free plan Free: 5K session recordings and 1M events per month Open source (MIT) Self-hosted Session replayReal user monitoringErrors

Side by side

Tool Pricing Free plan Open source Self-hosted LLM call tracingAgent and multi-step tracesToken and cost trackingPrompt managementEvaluationsDatasets and experimentsUser feedbackOpenTelemetry supportPlaygroundAlerts
AgentOps Free plan Yes Yes Yes YesYesYes----YesNo-
Future AGI Free plan Yes Yes Yes YesYesYesYesYesYesYesYesYesYes
Helicone Free plan 10,000 requests, 1 GB storage, 1 seat Yes Yes YesYesYesYes-YesYesYesYesYes
Laminar Free plan 1 GB data, 7-day retention, 1 seat Yes Yes YesYesYes-YesYesYesYesYesYes
Langfuse Free plan 50k units/mo, 30 days data access, 2 users Yes Yes YesYesYesYesYesYesYesYesYes-
LangWatch Free plan 50k events/mo, 14-day data access, 2 users Yes Yes YesYesYesYesYesYesYesYesYesYes
Latitude Free plan 20K credits/mo, 30-day retention Yes Yes YesYesYes-YesYesYesYes-Yes
OpenLIT Free Yes Yes Yes YesYesYesYesYes-YesYesYes-
OpenLLMetry Free plan Traceloop: 50K spans/mo, 5 seats, 24h retention Yes Yes YesYesYesYesYesYesYesYesYes-
Opik Free plan 25k spans/mo, 10 members, 60-day retention Yes Yes YesYesYesYesYesYesYesYesYesYes
PostHog Free plan 5K session recordings and 1M events per month Yes Yes YesYesYesYesYesYesYesYesYesYes

Yes: confirmed in the tool's documentation. No: documented as not offered. -: not confirmed. Plans and prices change; check each tool's own site before you decide.

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