LANGFUSE → STAX

Langfuse is for engineers debugging LLM apps. Stax is for the person who pays the bill.

Langfuse is the strongest open-source LLM tracing platform on the market — 26K GitHub stars, 2,000+ paying customers, just acquired by ClickHouse. It's not going anywhere. It's also not built to track your Cursor seats, Claude Pro accounts, or ChatGPT Team subscriptions, and never will be.

These are different jobs. Langfuse answers "why did this prompt fail?" Stax answers "why is our card statement $4,200 this month?" Most teams need both. The team that only needs the second thing is paying $731+/mo for Langfuse Core at 10M units to get an answer that's $49 flat on Stax.

Verified 2026-05-13 · langfuse.com/pricing · langfuse.com/blog/joining-clickhouse

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Why Stax

Three reasons this is a wedge, not a war.

01 · Different audience

Langfuse talks to engineers. Stax talks to whoever pays.

Langfuse's hero says "production gen AI" and lists traces, observations, evals. Stax's hero says "your entire AI bill, one number." A founder, CFO, or ops lead reads exactly one of those and feels addressed. Most teams need both — they coexist.

02 · Subscription blind spot

Langfuse traces API calls. It can't see Cursor.

Langfuse's docs are explicit: it tracks token cost from the API trace. Cursor seats, Claude Pro, ChatGPT Team, Perplexity Pro — all invisible to it because they're not API calls. For a 10-person team, that's often the bigger number.

03 · Pricing that doesn't compound

Stax is flat. Langfuse compounds.

Langfuse Core is $29/mo + $8 per 100K units past 100K. At 10M units/month — modest team scale — that's ~$731/mo. Pro is ~$901. Stax stays $49 flat regardless of how much spend you're tracking. No counter, no overage math.

FEATURE COMPARISON

Stax vs Langfuse, side by side

Feature Langfuse Stax
What it tracks API traces, spans, evals, prompt versions API spend + subscription tools, in dollars
Subscription tracking (Cursor, Claude Pro, ChatGPT Team) ✗ Tracing-only — confirmed in docs ✓ Built-in for 8 vendors
Pricing Core $29 / Pro $199 / Enterprise $2,499 + $8 per 100K units overage $49/mo flat · $99 Team flat
UX persona LLM engineer / platform team (traces, evals, datasets) Founder / CFO / ops lead (dollars, by month, by team)
Setup SDK instrumentation OR OpenTelemetry ingest — code changes required Paste an API key per provider · or upload a CSV
Email alerts on spend thresholds ~ Available, engineer-targeted ✓ Plain-English, sent to whoever you pick
Open source / self-hostable ✓ MIT license, 26K stars (free if you self-host) ✗ Hosted only
FAQ

Should I use both?

Do I need to choose between Langfuse and Stax?
No. They solve different problems. Langfuse is for engineers debugging "why is this RAG pipeline returning bad answers." Stax is for the founder or CFO answering "what's our AI spend this month, broken down by team and tool." If you have engineers AND someone who pays the bill, you probably want both. Stax exists because the second person was getting nothing.
Can Stax do prompt versioning, evals, or trace inspection?
No, and we won't try. That's Langfuse's job and they're great at it. Stax is built around the bill — costs, subscriptions, alerts, exports. If you need request-level traces and evaluation pipelines, instrument with Langfuse and keep Stax for the budget conversation.
Langfuse is open-source and free if I self-host. Why pay anyone?
If you have time to run a Postgres + ClickHouse stack and keep up with the upgrade path, self-hosted Langfuse is genuinely free. Most small teams don't have that time, which is why Cloud Core is $29/mo and Pro is $199/mo. Stax doesn't have a self-host option — that's a real trade. We're a small SaaS at $49/mo flat; we can't support self-hosters at that price honestly.
Langfuse just got acquired by ClickHouse. Is the product going to change?
The opposite of the Helicone story. ClickHouse is a $15B real-time analytics database — the acquisition makes Langfuse's data layer faster and deeper. Both teams have publicly committed to open source. Langfuse is shipping new dashboards, evals, and experiments features as recently as May 2026. Active development continues.
What about the "billable units" math at scale?
Langfuse counts traces + observations + scores. One RAG pipeline call easily generates 6+ units. That's fine when you're paying $29 for 100K units; it's a real number when you're at 10M units and the bill is $731+/mo. If you're a high-volume team and the cost-per-unit math matters more than tracing depth, Stax stays $49 regardless. If you need the tracing, the cost is part of the deal.
Does Stax integrate with Langfuse?
Not yet. The two tools track different data — Langfuse tracks per-request, Stax tracks per-billing-period — so there's no obvious surface for an integration today. If a team specifically wanted "show me Langfuse trace cost rollups inside Stax", email [email protected] and we'll talk about whether the demand is real.

Use Langfuse for the engineering. Use Stax for the bill.

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