Best Langfuse alternatives (open source, 2026)

TL;DR: Langfuse is a strong default for LLM observability. If you want an Apache-2.0, OpenTelemetry-native self-hosted stack with tracing, evaluations, Prompt Hub, agent monitoring, and GPU telemetry in one platform, OpenLIT is a clear alternative. Phoenix, Opik, Helicone, and OpenLLMetry each fit different lanes; see the table below.

Langfuse shows up on most “best LLM observability” lists for a reason: mature prompt and eval UX, solid self-host options, and a large community. That does not mean it is the only good choice. Buyers searching for Langfuse alternatives usually care about license (MIT vs Apache 2.0 vs dual license), OpenTelemetry posture, self-host ops, and whether they need a full platform or just instrumentation.

This guide is an honest roundup, including when staying on Langfuse is the right call. For a feature-by-feature breakdown of OpenLIT vs Langfuse, see OpenLIT vs Langfuse.

Quick comparison

Stay on Langfuse

Langfuse remains a solid pick if your team already likes its annotation workflows, datasets, and prompt/eval UI. It is open source at the core (MIT), self-hostable, and widely documented. If your main gap is OpenTelemetry-native spans, GPU metrics for self-hosted inference, or an Apache-2.0 full platform license, keep reading. Those are the lanes where alternatives differ most.

Best for: Teams happy with Langfuse’s prompt and evaluation UX who do not need a different license or OTel-first architecture.

OpenLIT

OpenLIT is an open-source Agent Harness Engineering platform for LLM tracing, evaluations, prompt management, and cost tracking, built on OpenTelemetry and free to self-host under Apache 2.0.

What that means in practice:

• OTel-native tracing for LLMs and agents via SDKs (Python, JavaScript, Go) or any OTLP source

• LLM evaluation with LLM-as-a-judge, custom evaluators, online (production traces) and offline/programmatic evals (docs)

• Prompt Hub for versioning, publishing, and fetching prompts at runtime (docs)

• AI agent monitoring, Vault for API keys, OpenGround model comparison, and a GPU collector for NVIDIA/AMD/Intel metrics

Unlike instrumentation-only libraries, OpenLIT is the self-hosted platform and the SDK. See the OpenLIT overview and OpenLIT vs Langfuse.

Best for: Apache-2.0 self-host with OTel-native LLM + GPU telemetry; full platform (traces, evals, prompts, agent monitoring).

Arize Phoenix

Arize Phoenix is a popular open-source option for LLM tracing and evaluation, with OpenInference conventions that map well to OpenTelemetry-style GenAI spans. It is strong when you want a dedicated Phoenix UI for traces and evals. License is Elastic License 2.0 (not Apache 2.0), which matters for some redistribution and SaaS policies.

Compare details: OpenLIT vs Arize Phoenix.

Best for: Teams that want Phoenix’s tracing/eval UX and are fine with ELv2.

Comet Opik

Comet Opik is an Apache-2.0 open-source project focused on LLM tracing and evaluation, with self-host options and ties to the broader Comet ML ecosystem. It is a frequent mention on Langfuse-alternative lists when buyers want OSS evals without leaving an open license.

Compare details: OpenLIT vs Comet Opik.

Best for: Open-source tracing and evaluation with Apache 2.0 and Comet ecosystem familiarity.

Helicone

Helicone takes a proxy/gateway approach: route LLM traffic through Helicone to capture logs, costs, and controls such as caching. It is Apache 2.0 and self-hostable, but it is not OpenTelemetry-native. If you cannot accept proxy latency or need non-OpenAI-compatible SDKs instrumented in-process, an SDK/OTel platform is usually a better fit.

Compare details: OpenLIT vs Helicone.

Best for: Gateway-style observability with caching and key/rate controls in front of LLM APIs.

OpenLLMetry / Traceloop

OpenLLMetry is an OpenTelemetry instrumentation library, not a full self-hosted observability product. It auto-instruments LLM frameworks and exports OTLP to backends you choose (including Traceloop’s cloud). That is a different category from Langfuse or OpenLIT.

OpenLIT also speaks OTLP, but ships the platform (UI, evals, Prompt Hub, agents, Vault, GPU) plus its own SDKs. See OpenLIT vs OpenLLMetry.

Best for: Teams that only need instrumentation and already have (or prefer) a separate OTLP backend.

LangSmith (optional)

LangSmith is LangChain’s proprietary observability and evaluation platform. It is excellent if you are deep in LangChain/LangGraph and want first-party tooling. It is not open source, and self-hosting is limited to enterprise plans. Include it in a shortlist only if framework lock-in is acceptable.

Compare details: OpenLIT vs LangSmith.

Best for: LangChain-centric teams who want a managed, proprietary toolchain.

How to choose

1. Need Apache 2.0 + full self-hosted platform + OTel-native LLM/GPU telemetry? Start with OpenLIT.

2. Happy with Langfuse’s prompt/eval UX already? Stay, or read OpenLIT vs Langfuse before switching.

3. Want Phoenix’s eval/trace UX and accept ELv2? Look at Arize Phoenix.

4. Want Apache-2.0 evals with Comet ties? Look at Opik.

5. Need a proxy gateway? Helicone.

6. Only need an instrumentation library? OpenLLMetry, then pick a backend (OpenLIT can be that backend via OTLP).

Related reading

• OpenLIT vs Langfuse

• All OpenLIT comparisons

• Open-source LLM evaluation and prompt management

• OpenLIT docs overview

• Self-host OpenLIT