Langfuse

Good for / not for

What it actually does

Langfuse records what your AI app actually did. Each model call becomes a trace: the prompt that went out, the response that came back, the cost, and the error if there was one. Around that sit prompt management, evaluations, experiments and a playground, so the trip from "this answer was bad" to "here is the version that fixed it" happens in one tool. Instrumentation is OpenTelemetry-based, which is a real integration step rather than a switch you flip. Two things decide whether it fits. The first is hosting: the MIT core carries no usage limits and you can run the whole thing yourself, but the Enterprise Edition is source-available and needs a commercial licence key, and SCIM, audit logging and retention policies sit behind it even when self-hosted. The second is ownership. ClickHouse acquired Langfuse on 16 January 2026, bundled into ClickHouse's $400M Series D at a $15B valuation. The announcement says the project stays open source and self-hostable with an unchanged roadmap; what changed is that the roadmap now sits inside a much larger company. On the hosted side, Hobby is free for 50,000 units a month and Core is $29.

Pricing and free-plan limits

Free tier: 50,000 units a month on the hosted Hobby plan, with 30-day retention and two users, no card. Self-hosting the MIT core has no usage limits.

Three honest limitations

1. ClickHouse acquired Langfuse on 16 January 2026, bundled into ClickHouse's $400M Series D at a $15B valuation. The announcement says the project stays open source and self-hostable with an unchanged roadmap, but ownership now sits inside a much larger company.
2. Enterprise features — SCIM, audit logging, retention policies — need a paid licence key even when you self-host. The MIT core covers tracing, evals, prompts, experiments and the playground; those three are not in it.
3. Long agent traces get hard to parse, and a review reports bulk trace pulls and date-range filtering slowing down at scale.

Alternatives

• E2B — Choose E2B instead if the missing piece is somewhere safe to run the code your model wrote, not a record of what it did.
• Firecrawl — Choose Firecrawl instead if the problem is upstream — getting clean page content into the app in the first place.
• Browser Use — Choose Browser Use instead if the job is an agent operating a website, rather than the trace of what it produced.

Getting started in 5 minutes

1. Start on the hosted Hobby plan: 50,000 units a month, 30-day retention, two users, no card.
2. Instrument one path first. Tracing here is OpenTelemetry-based, so plan for an integration rather than a toggle.
3. Watch the retention window before the unit count. Hobby keeps 30 days, Core 90 days at $29 a month, Pro three years at $199.
4. If you self-host, check your feature list against the licence key: SCIM, audit logging and retention policies need a paid key even on your own hardware.
5. Read the ClickHouse acquisition note before you standardise on it. The project is still open source and self-hostable, but ownership changed on 16 January 2026.

Langfuse questions

What is LLM observability?

A record of what your AI app did, detailed enough to explain a bad answer afterwards: which prompt went out, what came back, what the call cost, and where it broke. Ordinary application logs do not capture that in a usable shape. Langfuse stores each call as a trace you can open, and adds evaluations and prompt management so a bad answer can be traced back to a prompt version.

Is Langfuse free?

The hosted Hobby plan is: 50,000 units a month, 30-day retention, two users, no card. Self-hosting the MIT core has no usage limits at all. The paid hosted tiers are Core at $29 a month for 100,000 units and unlimited users, Pro at $199 with three-year retention, and Enterprise at $2,499.

Who owns Langfuse now?

ClickHouse. The acquisition was announced on 16 January 2026 and bundled into ClickHouse's $400M Series D at a $15B valuation. The announcement says the project stays open source and self-hostable with an unchanged roadmap. That is a stated intention rather than a guarantee, so it belongs in the decision rather than in the footnotes.

Is everything free when I self-host?

No. The MIT core — tracing, evals, prompts, experiments, the playground — carries no usage limits. The Enterprise Edition is source-available and needs a commercial licence key, and SCIM, audit logging and retention policies live inside it even when the software runs on your own servers.

Is the project active?

34,268 GitHub stars and a push on 6 September 2026. Langfuse v4 shipped on 17 August 2026 and a CLI 1.0 rewrite on 21 August 2026. The company went through Y Combinator in the W23 batch.

Sources

• Langfuse pricing (Hobby free at 50,000 units/month, 30-day retention, 2 users; Core $29/month; Pro $199/month; Enterprise $2,499/month)
• ClickHouse announcement of the Langfuse acquisition, 16 January 2026, inside a $400M Series D at a $15B valuation
• Langfuse discussion 10745 (SCIM, audit logging and retention policies need a paid licence key even when self-hosted)
• Langfuse review (long agent traces hard to parse; bulk trace pulls and date-range filtering slow at scale)
• Source code: MIT core; Enterprise Edition source-available