GILD verdict
Choose Arize when flagged failures go straight to a person or traces must stay on your servers, and Braintrust when misses cost most.
- The workflow
- an AI team choosing the platform whose eval agent and bill it will live with once agents are in production
- The decisive evidence
- MeasuredOn 100 hand-labelled production traces, Parlance Labs found on Jul 11, 2026 that Braintrust Loop had the highest recall of three platforms and that 91% of Arize Alyx's flags were valid, with three wrong.1
- DocumentedBraintrust Pro lists US$3 per GB and US$1.50 per 1,000 scores past its allowance; Arize's pricing page lists no AX Pro overage rate as of Oct 28, 2026.310
- GILD analysisThe AX bill at volume is unresolved. GILD's calculation from published rates puts 200,000 traces a month with one score each at US$474 on Braintrust Pro, while AX Pro's US$50 base fee leaves 1,950,000 spans unpriced until Arize quotes a rate.
- The tradeoff
- Braintrust's bill also follows published rates. Phoenix costs only the server it runs on, but your team owns its database, sign-in and upgrades. Braintrust runs the control plane for you and self-hosts its data plane only on Enterprise.171013
- What would change the call
- The call moves when a second team publishes a head-to-head on its own traces, or when Arize publishes an AX Pro overage rate that undercuts Braintrust at your span count.
The one head-to-head on record splits the pair by what an eval agent must get right. In Parlance Labs' July 2026 test on 100 hand-labelled traces, Braintrust Loop had the highest recall and Arize Alyx the best precision, with 91% of its flags valid. Arize is the side you can self-host free on Phoenix; Braintrust self-hosts only on Enterprise. Braintrust prints its Pro overage rates and Arize no longer does.
What teams report
Evaluated 3
Parlance Labs
Parlance Labs masked the hand labels on 100 production traces from an apartment-leasing assistant and asked Braintrust Loop, Arize Alyx and LangSmith to find the failures (Jul 11, 2026). Alyx flagged fewer failures than Loop, and 91% of its flags were valid.
“Arize traded recall for precision. Alyx missed more of the human-labeled failures than Loop, but 91 percent of its flags were valid and only three were wrong.”
Antaripa Saha and Hamel Husain, Evaluation practitioners and co-authors, Parlance LabsParlance Labs, , write-up Parlance LabsOn Braintrust
In the same test Braintrust Loop had the highest recall of the three platforms, and the authors found it easy to use from upload to export.
“Braintrust had the highest recall of the three platforms and was easy to use. We could upload our traces, perform the auto-evaluation, and export its findings seamlessly.”
Antaripa Saha and Hamel Husain, Evaluation practitioners and co-authors, Parlance LabsParlance Labs, , write-up Parlance LabsOn Arize
Alyx first read only the first 200 characters of each trace, and later runs hit compaction and timeouts; Arize fixed each problem quickly once Parlance Labs reported it.
“The workflow had rough spots. Alyx initially read only the first 200 characters of each trace, and later runs hit compaction and timeout problems. The Arize team resolved each issue quickly once we reported it.”
Antaripa Saha and Hamel Husain, Evaluation practitioners and co-authors, Parlance LabsParlance Labs, , write-up
Choosing between Arize and Braintrust
Choose Arize if
- Each failure the eval agent flags must be right, because a person acts on it: in Parlance Labs' test, 91% of Alyx's flags were valid and only three were wrong (Jul 11, 2026).
- You want to self-host without an Enterprise contract: Phoenix runs on your own Docker or Kubernetes with no feature gates, about US$48 a month in infrastructure on one VM in GILD's calculation.
- You also monitor classification, ranking, or vision models for drift and performance.
Choose Braintrust if
- The eval agent must miss as little as possible: Braintrust Loop had the highest recall of the three platforms Parlance Labs tested (Jul 11, 2026).
- You want a bill you can compute before the allowance runs out: on Pro, US$3 per GB of processed data and US$1.50 per 1,000 scores, which puts GILD's 200,000-trace workload at US$474 a month.
- You want the data plane in your cloud and operated by the vendor, through BYOC on Enterprise.
Side by side
| Dimension | Arize | Braintrust |
|---|---|---|
| What teams reportThe only named head-to-head GILD found. One 100-trace dataset from one apartment-leasing assistant. | Parlance Labs, Jul 2026: Alyx missed more hand-labelled failures than Loop, but 91% of its flags were valid and three were wrong. Early runs read only the first 200 characters of each trace and hit compaction and timeouts, fixed once reported.1 | Parlance Labs, Jul 2026: Loop had the highest recall of the three platforms and was easy to use, from upload through export. Every platform missed failures that needed business context.1 |
| PlansList prices in US dollars. Both include unlimited users on every plan. | Phoenix free to self-host; AX Free US$0; AX Pro US$50 a month; AX Enterprise custom3 | Starter US$0; Pro US$249 a month; Enterprise custom, invoiced annually10 |
| Included volumePrice your trace shape against each meter. Arize counts spans and gigabytes. Braintrust counts processed gigabytes and scored outputs. | 25,000 spans and 1 GB a month on AX Free; 50,000 spans and 10 GB a month on AX Pro; Phoenix limited only by the infrastructure you run | 1 GB of processed data and 10,000 scores a month on Starter; 5 GB and 50,000 scores on Pro |
| Usage price | Pro includes 50,000 spans and 10 GB a month, and Arize's pricing page lists no overage rate (Oct 28, 2026); Enterprise volume is custom316 | US$4 per GB and US$2.50 per 1,000 scores on Starter; US$3 per GB and US$1.50 per 1,000 scores on Pro10 |
| 200,000 traces a month, 10 usersGILD's calculation from published rates, Oct 28, 2026. Inputs: 200,000 traces a month, 10 spans, 2 model calls and 1 code score per trace, 20 KB per trace, 10 users, 30 days retained, no judge calls. | US$50 AX Pro base fee, plus 1,950,000 spans past the 50,000 included at a rate Arize no longer publishes, so the total needs a quote. Self-hosted Phoenix on one 4-vCPU, 8 GiB VM: about US$48 a month in infrastructure, before operations time.34 | US$474 a month on Pro: US$249, plus US$225 for 150,000 scores past the 50,000 included, at US$1.50 per 1,000. The 4 GB of data stays inside the 5 GB included.1011 |
| Retention | 15 days on AX Free; 30 days on AX Pro, with a self-serve 13-month add-on; custom on Enterprise; Phoenix keeps data until a retention policy you set removes it | 14 days on Starter; 30 days on Pro, extendable to 180 days at US$0.50 per GB a month; up to 365 days on Enterprise |
| Self-hosting | Phoenix free to self-host under the Elastic License 2.0; Arize AX self-hosted on Kubernetes under Enterprise | Enterprise only: a data plane you operate, or BYOC that Braintrust operates in your cloud; Braintrust always runs the control plane |
| Built-in agents | Alyx, and Signal, which files recurring production failures as issues: 10 a month on Free, 25 on Pro, unlimited on Enterprise16 | Loop, Braintrust's agent, on every plan, and Topics, which draws on monthly model credits: US$10 on Starter, US$100 on Pro, then token rates110 |
| SSO and access control | SAML SSO, audit logs, and multiple organizations on Enterprise; 1 space on Free, 1 organization and 2 spaces on Pro | Google sign-in on Starter and Pro; SAML or OIDC SSO, custom roles, and audit logs on Enterprise |
| Compliance | SOC 2 Type II and GDPR from Pro; HIPAA on Enterprise | SOC 2 attestation, a BAA for HIPAA, and a custom DPA on Enterprise; click-through DPA on Pro |
What practitioners report, side by side
Each product's figures come from its own practitioners, for the group you pick.
Overall signal
Teams and leaders rate Braintrust +50, 24 points above Arize at +26. Most of the gap is in praise, with 20 of Braintrust's 34 sources positive against 11 of Arize's 27. Braintrust has 3 negative and Arize 4.
The score counts the authors from teams and leaders that take a side, one vote each with their latest view, and is how far positive votes lead negative ones, per 100 votes, so Braintrust's +50 rests on votes split 19 positive, 10 mixed and 3 negative. Each of Arize's authors wrote one source here, so each source is one vote.
A lead of a fifth of the votes reads positive and a lead of half strong positive, with the same lines below zero. The dots show each source, positive, mixed, negative. Run a pilot on one production app to measure which failures it surfaces and how long tracing them takes.
Footprint on the AI Application Platform stack
They differ on three of 9 layers. Coverage is each product's placement on this stack, as its product page shows it. Core is a job the product owns; Supports and Touches are jobs it helps with. Coverage says nothing about how well a product does them.
| Layer | Arize | Braintrust |
|---|---|---|
| Model | ||
| Model gateway | Touches | Supports |
| Build | ||
| Tool use | Touches | Supports |
| Operate | ||
| Guardrails | Supports | Touches |
The 6 layers where they match
| Layer | Arize | Braintrust |
|---|---|---|
| Model | ||
| Model APIs | Touches | Touches |
| Build | ||
| Orchestration | Touches | Touches |
| Data | ||
| Retrieval | Touches | Touches |
| Evaluate | ||
| Evaluation | Core | Core |
| Operate | ||
| Observability | Core | Core |
| Cloud deployment | Touches | Touches |
What practitioners praise
Among teams and leaders, Free, Simple Self-Hosting and OpenTelemetry & OpenInference reach 5 sources from 3 authors only for Arize, at 6 of 6 and 5 of 6. Braintrust needs a pilot on the same production traffic before you choose on either. Both carry Trace-Level Debugging. It is praised in 10 of the 11 Arize sources that discuss it, against 7 of 8 for Braintrust. Datasets, Experiments & Scorers and Instrumentation & SDK Coverage reach 5 sources from 3 authors only for Braintrust, at 20 of 21 and 3 of 5. Arize needs a pilot on the same production traffic before you choose on either.
| Praised for | Arize | Braintrust |
|---|---|---|
| Trace-Level Debugging | 10 of 11 | 7 of 8 |
| Free, Simple Self-Hosting | 6 of 6 | Not a theme in its sources |
| OpenTelemetry & OpenInference | 5 of 6 | Not a theme in its sources |
| Datasets, Experiments & Scorers | Not a theme in its sources | 20 of 21 |
| Instrumentation & SDK Coverage | Not a theme in its sources | 3 of 5 |
Each count is the sources that praise a theme, or raise it as a concern, out of those that discuss it. A row pairs the two products when both carry a theme under the same or an equivalent name.
A count ending in "so far" has under 5 sources from 3 authors among teams and leaders. "Not a theme in its sources" means GILD found no theme of that name in that product's sources.
What practitioners raise as concerns
Among teams and leaders, SDK & Ingestion Reliability and Build It Yourself reach 5 sources from 3 authors only for Braintrust, at 6 of 6 and 2 of 6. Arize needs a pilot on the same production traffic before you choose on either. Scale & Self-Host Operations reaches 5 sources from 3 authors only for Arize, at 6 of 6. Braintrust needs a pilot on the same production traffic before you choose on it.
| Raised as a concern | Arize | Braintrust |
|---|---|---|
| Scale & Self-Host Operations | 6 of 6 | Not a theme in its sources |
| SDK & Ingestion Reliability | Not a theme in its sources | 6 of 6 |
| Build It Yourself | Not a theme in its sources | 2 of 6 |
16 sources
- Parlance Labs: Auto-evals with Braintrust Loop, Arize Alyx and LangSmith (Jul 11, 2026)
- Hamel Husain: Selecting the right AI evals tool (Oct 1, 2025)
- Arize AX pricing
- Arize AX docs: Pricing and usage
- Arize AX docs: Release notes (13-month retention on Pro, Jul 10, 2026; Signal general availability, Jul 29, 2026)
- Arize AX docs: Signal
- Phoenix docs: License
- Arize AX docs: Self-hosted
- Arize docs: ML models (predictions, drift, and performance)
- Braintrust pricing
- Braintrust docs: Plans and limits
- Braintrust docs: Deployment options
- Braintrust docs: Self-hosting Braintrust
- Braintrust docs: Configure data retention
- Braintrust docs: Security
- Arize: Compare Arize