Langfuse is a strong open-source home for LLM tracing, prompt management, and evaluation — self-hostable, which many teams love — while ValidAnytime is the production alarm on the scores those evals emit. Where Langfuse stops is alerting you can lean on: run evals on a schedule and the more often you check, the more they false-alarm. ValidAnytime watches those scores with an anytime-valid guarantee, so a real regression trips one alarm as soon as the evidence is decisive — not a week of noise you learn to mute.
| Capability | ValidAnytime | Langfuse |
|---|---|---|
| Valid under continuous monitoring (unlimited peeking) | YesAnytime-valid by construction — Ville's inequality bounds the false-alarm rate at every look at once. | NoFixed thresholds and fixed-n tests inflate false alarms the more often you check. |
| Fleet-wide false-alarm control (online FDR) | YesA false-discovery budget shared across every stream, not per-alert luck. | NoAlerts are configured per-metric; no global bound on false discoveries. |
| Per-alarm statistical certificate | YesEvery alarm ships a guarantee tag and a theorem reference — you can audit why it fired. | NoAn alert tells you a line was crossed, not what its error guarantee is. |
| Prove it on your own history before committing (backtest gate) | YesReplay your past data: a config only ships if it stays quiet on normal history and fires on a real regression. | PartialYou can chart history, but there is no gate that validates a detector's error behaviour before it goes live. |
| LLM tracing & prompt management | NoWe do not trace calls or manage prompts — we watch the metrics your evals produce. | YesRich tracing, prompt versioning, and playground tooling. |
| Self-hostable, open-source core | NoThe anytime-valid engine runs in the ValidAnytime cloud; the thin API client and the classical-detector library are open-source, the engine is not. | YesOpen-source and self-hostable — a genuine advantage for some teams. |
| Production alerting you can trust continuously | YesAn anytime-valid alarm with a certificate on every fire, plus a fleet-wide false-alarm budget. | PartialEvals, scores, and dashboards exist, but alerting has no valid-under-peeking guarantee. |
We are not trying to be a dashboard, a tracer, or a platform. If you need these, reach for the right tool — often alongside ValidAnytime.
A comparison table is claims; behavior is measurable. The honest drift-detector benchmark replays every detector we ship — including the classical control-chart rules most monitoring stacks alert with — against labeled synthetic breaks, and the detector guides explain each rule, where it wins, and where it lies.
Replay your own history through the backtest gate and see whether — and at which point — ValidAnytime would have caught your regression. Free, in minutes.
Comparison based on public documentation as of July 2026; corrections welcome — email hello@validanytime.com. Source: Langfuse docs