Langfuse vs Helicone vs Opik vs Arize Phoenix
Four open-source tracing tools: only two are truly open, and one has stopped moving. Scores from the RXed AI Periodic Table v1.0 — identical 20-element scale, deterministic overall. How we audit →
At a glance
Scope = elements of the AI stack in the tool’s stated scope (dashed = honestly out of scope, never a penalty). Quality = how well it scores on what it covers. No single number — both axes, always.
The verdict
Opik (Scope 15/20 · Quality 7/10) is the cleanest deal: Apache-2.0, unlimited spans and seats self-hosted, the deepest evaluation (Ev 8.5) and the only guardrails that block personal data before it reaches a user — self-host only, five services to run. Langfuse (Scope 15/20 · Quality 7/10) is the tracing default (Tr 9, Pc 9 with 79 MCP tools), MIT-licensed, four services, ClickHouse-owned since January 2026. Arize Phoenix (Scope 17/20 · Quality 7/10) is one pip install with the best RAG evaluation (Ev 8.5) — but the server is Elastic License 2.0, not open source, and production monitoring is a separate paid product. Helicone (Scope 17/20 · Quality 5/10) entered maintenance mode when Mintlify bought it on 03/03/2026; last release August 2025. Small team, no platform engineer → Phoenix. Regression tests and guardrails → Opik. High volume, European data on your own servers → Langfuse. Already on Helicone → plan the migration.
Where the quality sits
Family mean over covered elements only — a dash means the family is honestly outside that tool’s scope.
| Langfuse Scope 15/20 · Quality 7/10 audited 2026-08-10 | Helicone Scope 17/20 · Quality 5/10 audited 2026-08-15 | Opik (Comet) Scope 15/20 · Quality 7/10 audited 2026-08-14 | Arize Phoenix Scope 17/20 · Quality 7/10 audited 2026-08-15 | |
|---|---|---|---|---|
| Vendor | Langfuse, a ClickHouse, Inc. company | Helicone, Inc., acquired by Mintlify on 03/03/2026 | Comet ML, Inc. | Arize AI, Inc. |
| Origin | DE | US | US | US |
| Pricing | Self-hosted Open Source €0 forever under MIT, unlimited usage and unlimited users, including SSO and organisation RBAC. Cloud: Hobby €0 (50,000 units per month, 30 days of data, 2 users), Core ~€27 per month (from $29: 100,000 units, 90 days, unlimited users, in-app support), Pro ~€183 per month (from $199: 3 years of history, data retention management, SOC 2 and ISO 27001 reports, HIPAA BAA), optional Teams add-on ~€276 per month (from $300: enterprise SSO, fine-grained RBAC, private Slack), Enterprise ~€2,299 per month (from $2,499: audit logs, SCIM, custom rate limits, uptime and support SLA, dedicated support engineer). Overage ~€7.35 per 100,000 units (from $8), falling to ~€5.98 above 50M units. Self-hosted Enterprise is custom and bundled with a ClickHouse Cloud, BYOC or Private plan. | Self-hosted €0 under Apache-2.0, with the caveat that the self-hosted build supports only OpenAI and Anthropic. Cloud: Hobby €0 (10,000 requests/month, 1 GB, 1 seat, 1 organisation, 7-day retention, 10 logs/min, no API access), Pro ~€73/month (from $79: unlimited seats, 1-month retention, 1,000 logs/min, 10 API calls/min, alerts, reports and HQL, plus usage-based overage above 10k requests and 1 GB), Team ~€735/month (from $799: 5 organisations, 3-month retention, 15,000 logs/min, 60 API calls/min, SOC 2 Type II and HIPAA, private Slack), Enterprise quote-only (unlimited organisations, indefinite retention, 30,000 logs/min, SAML SSO, on-prem, custom MSA, bulk cloud discounts). Discounts: 50% off the first year for startups under two years old and $5M funding, $100 credit for open-source projects, free for most students and educators. Euro figures converted from published USD at roughly 0.92. | Open source €0 forever under Apache-2.0, with unlimited spans, unlimited retention, unlimited team members and the full feature set self-hosted, including guardrails. Cloud: Free ~€0 (25,000 spans per month, 60-day retention, up to 10 members), Pro ~€17 per user per month (from $19: 100,000 spans, up to 50 members, 60-day retention, additional spans ~€4.60 per 100,000 and retention extension to 400 days ~€27 per 100,000), Enterprise custom (unlimited spans, custom retention, RBAC at project and organisation level, enterprise SSO over OAuth 2.0, SAML and LDAP, custom hosting). Free Pro plan for verified academics. Euro figures converted from published USD at roughly 0.92. | Self-hosted €0 with no usage caps and no feature gates, under the Elastic License 2.0 (source-available, not OSI open source; the arize-phoenix-otel, -client and -evals subpackages are Apache-2.0). Phoenix Cloud gives two hosted instances free. The separate managed Arize AX platform: AX Free €0 (25,000 spans/month, 1 GB, 15 days), AX Pro ~€46/month (from $50: 50,000 spans, 10 GB, 30 days), AX Enterprise quote-only (custom volumes, self-hosting, SOC 2 Type II, HIPAA, SSO, audit logs). All AX tiers carry unlimited seats and unlimited evals, and let you pick a US, EU or Canada data region. Euro figures converted from published USD at roughly 0.92. |
| Pr Prompts | 9 | 5 | 8 | 8 |
| Em Embeddings | — | — | — | 6 |
| Cx Context | 8 | 6 | 7 | 8 |
| Tr Tracing | 9 | 8 | 9 | 8 |
| Lg LLM | 6 | 7 | 6 | 6 |
| Fc Function calling | 7 | 5 | 7 | 7 |
| Vx Vector store | — | — | — | — |
| Rg RAG | 5 | 3 | 5 | 7 |
| Gr Guardrails | 5 | 7 | 8 | 5 |
| Mm Multimodal | 8 | 4 | 8 | 6 |
| Ag Agents | 6 | 3 | 7 | 8 |
| Ft Fine-tuning | — | 5 | — | — |
| Fw Frameworks & harnesses | 9 | 7 | 8 | 9 |
| Ev Evaluations | 8 | 4 | 9 | 9 |
| Sm Small models | — | 5 | — | — |
| Ma Multi-agent | 6 | 4 | 6 | 6 |
| Sy Synthetic data | 4 | 3 | 7 | 4 |
| Pc Protocols | 9 | 5 | 7 | 9 |
| In Interpretability | — | — | — | 5 |
| Th Thinking models | 6 | 5 | 5 | 6 |
Hover any score for the written reason. Full detail: Langfuse passport → · Helicone passport → · Opik (Comet) passport → · Arize Phoenix passport →