Braintrust

What is Braintrust?

Braintrust is an AI evaluation and observability platform for tracing, testing and improving LLM applications and agents. It is made by Braintrust Data and combines production tracing with datasets, scorers and experiments in one workspace. The problem it solves is quality control: teams can see what a model actually did, compare prompts and models against a test set, and catch regressions before a change reaches users.

Key features

• Tracing. Every model call, tool call and span can be logged with inputs, outputs, latency and metadata for debugging.
• Evaluations. Teams run experiments against datasets and compare prompts, models and retrieval setups on accuracy, latency and cost.
• Scorers. Built-in and custom scorers include LLM-as-a-judge, heuristic checks and code-based assertions.
• Playgrounds. Prompts can be edited and compared side by side before a change is promoted.
• Production monitoring. Online scores and trace views show how an application performs after deployment.
• Loop agent. A built-in agent can run evaluations, generate test cases and iterate on prompts.
• Access controls. Pro and Enterprise plans add roles, environments and longer data retention, with SSO and HIPAA options on Enterprise.

Who is Braintrust for?

AI engineering teams building chatbots, RAG systems, agents and other LLM products. It suits teams moving from ad hoc prompt testing to a repeatable evaluation process, platform teams that need traces from production, and organisations that need role-based access, retention controls or a business associate agreement. It is also used by product teams that want to compare model providers before committing.

Use cases

• Tracing an agent's tool calls to find where a task fails.
• Comparing two prompts or models on the same evaluation dataset.
• Adding automated quality gates before deploying a prompt change.
• Monitoring production responses for quality and cost regressions.
• Building a regression suite for a RAG assistant.

Pricing

Braintrust has a Starter plan at $0 per month with $10 of model credits, 1 GB of processed data, 10,000 scores and 14-day retention. Pro costs $249 per month with $100 of model credits, 5 GB of processed data, 50,000 scores, 30-day retention, custom charts, environments, RBAC and priority support. Usage beyond the included amounts is billed per GB of processed data and per 1,000 scores. Enterprise pricing is custom and adds longer retention, SSO, a business associate agreement, on-premises or hosted deployment and premium support. See the official Braintrust pricing page.

Getting started

1. Create a Braintrust account and generate an API key.
2. Install the SDK and set BRAINTRUST_API_KEY in your environment.
3. Log a trace around a model call, then open it in the project view.
4. Add a dataset and a scorer to turn the trace into a repeatable evaluation.

pip install braintrust

Alternatives

• LangSmith is a platform for tracing, evaluating and monitoring LLM applications.
• Langfuse is an open source LLM observability and evaluation platform.
• Arize Phoenix is an open source AI observability and evaluation tool.

FAQ

Is Braintrust free?

Yes. The Starter plan costs $0 and includes $10 of model credits, 1 GB of processed data, 10,000 scores and 14-day retention. Pro costs $249 per month.

What is Braintrust used for?

Braintrust is used to trace, evaluate and monitor LLM applications. Teams log model and tool calls, run experiments against datasets, and compare quality, latency and cost.

Braintrust vs LangSmith?

Both provide tracing and evaluation for LLM applications. Braintrust emphasises datasets, scorers and experiments in one workspace, with a Loop agent for automated iteration. LangSmith is closely integrated with the LangChain ecosystem. The better choice depends on your framework and evaluation workflow.

Does Braintrust support agents?

Yes. It traces agent runs, including tool calls and multi-step spans, and can score the final output or intermediate steps.

Can I self-host Braintrust?

Self-hosting is available on Enterprise plans, along with hosted deployment, custom retention and premium support.