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Braintrust vs Arize AI. Rows marked Differs have different values.

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Braintrust

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Arize AI

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TypeStartupStartup
Categories
In one lineEnterprise-grade evals, data and AI gateway.Observability and evaluation for AI — makers of OSS Phoenix.
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Pros
  • User reportsUsers find it easy to set up datasets and run evals across models; one calls it a game changer for checking prompts, especially for classification.[1][2]
  • Independent testTracing, evals, datasets and prompts in one product, which a six-month hands-on review called the most complete eval toolchain in 2026.[1]
  • Independent testYou can turn any production trace into a golden eval example from the UI, and the free tier includes 1M trace spans and 10K scores a month.[1]
  • User reportsPractitioners use it for model comparisons such as long-context retrieval under production constraints.[1]
  • MetadataPhoenix is free to self-host and very active (about 12k stars, commits on 29 Oct 2026).[1][2]
  • User reportsBuilt on OpenTelemetry and OpenInference, so traces are portable; users praise OpenInference, and a community proxy sends Claude Code spans to Phoenix.[1][2]
  • User reportsPractitioners use Phoenix for LLM-as-judge plus code-based evals and continuous analysis of production traces.[1][2]
  • DocsEvery AX plan, including Free, has unlimited users and evals, and AX Pro costs $50/month.[1]
Cons
  • Independent testClosed source with no self-hosting on standard plans; only Enterprise gets a VPC option.[1][2]
  • Independent testLock-in risk: datasets, eval configs and trace history live in Braintrust, and the review found the export tooling is not prominent.[1]
  • Independent testLLM-as-judge scorers add model costs on top of the platform fee, estimated at $500-2,000/month for 10K evals a day with expensive judges.[1]
  • User reportsPro costs $249/month, and one happy user said the core features are simple enough that they would build them themselves next time.[1][2]
  • MetadataPhoenix uses the Elastic License 2.0, which is source-available rather than OSI open source and restricts offering it as a managed service.[1]
  • DocsAX Free caps you at 25k spans a month with 15-day retention, and Pro raises that only to 50k spans and 30 days.[1]
  • DocsSelf-hosted AX, SSO and audit logs are Enterprise-only.[1]
  • User reportsOne user found Arize's Claude Code tracing setup heavyweight, and others dropped Phoenix after reviewing its site.[1][2]
  • MetadataPhoenix has about 1,000 open GitHub issues.[1]
Best forTeams that want a polished, hosted eval and tracing workflow from day one.Teams that want OpenTelemetry-native LLM tracing and evals they can run themselves with Phoenix, with a hosted option later.
Watch out forPlan how you will export datasets, and budget for LLM-judge costs.AX Free and Pro have low span and retention caps, and ELv2 limits offering Phoenix as a service.
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