Langfuse vs. Braintrust
This guide outlines the key differences between Langfuse and Braintrust to help engineering teams choose the right LLM observability platform.
TL;DR:
- Choose Langfuse if you prioritize an open-source, vendor-neutral platform that allows for full self-hosting, predictable unit-based pricing, and deep integration with OpenTelemetry standards.
- Choose Braintrust if you prefer a proprietary, “batteries-included” SaaS platform that focuses heavily on the evaluation loop, offering an integrated proxy and specialized tools for rapid prompt iteration.
Open Source & Distribution
The most fundamental divergence lies in the distribution model. Langfuse is open-source (MIT), ensuring transparency and no vendor lock-in. Braintrust is a proprietary, closed-source platform where the core engine and database are managed property.
| Feature | Langfuse | Braintrust |
|---|---|---|
| Model | Open Source (MIT License) | Proprietary SaaS (Closed Source Core) |
| GitHub Stars |  | N/A |
| PyPI Downloads |  |  |
| npm Downloads |  |  |
| Docker Pulls |  | N/A |
| Self-Hosting | First-Class Citizen: Full feature parity with Cloud. capable of running offline or in air-gapped environments. | Restricted: Hybrid model only available on Enterprise tiers (Data plane in VPC, Control plane managed). |
Scalability & Performance
Both platforms utilize high-performance analytical databases, but their architectural philosophies differ. Langfuse relies on the open-source power of ClickHouse, while Braintrust relies on a custom-built proprietary engine.
| Feature | Langfuse | Braintrust |
|---|---|---|
| Backend | ClickHouse: Transitions to ClickHouse in v3 for sub-second query performance on billions of events. | Brainstore: Proprietary engine using streaming Rust and object storage. |
Integrations
Langfuse adopts a “standards-first” strategy via OpenTelemetry and async ingestion, whereas Braintrust focuses on their own proprietary proxy layer.
| Feature | Langfuse | Braintrust |
|---|---|---|
| Standard | OpenTelemetry Native SDKs: Interoperable with existing enterprise stacks (Java, Go, Rust via OTLP). | Focuses on wrapOpenAI SDKs and a proprietary AI proxy gateway. |
| Frameworks | 100+ Integrations: Native support for LangChain, LlamaIndex, CrewAI, AutoGen, and more. | Support for many of the popular frameworks and model providers. |
Pricing
Langfuse offers a predictable unit-based model. Braintrust uses a multi-dimensional model charging for data volume, scores, and retention.
| Feature | Langfuse | Braintrust |
|---|---|---|
| Free Tier | Cloud: 50k units/mo. Self-Hosted: Unlimited free usage. | Free: 1M trace spans, 1 GB processed data, 10k scores, 14-day retention. |
| Paid Entry | Core: Starts at $29/mo (includes 100k units). | Pro: Starts at $249/mo (includes 5GB data, 50k scores). |
| Billing Model | Unit-Based: Prices based on simple “billable units” (traces, observations, scores). | Multi-Dimensional: Charges for Processed Data (GB) + Scores + Data Retention. |
| Overage Costs | ~$8.00 per 100k units (decreasing with volume). | $3 per GB processed data; $1.50 per 1k scores. |
Open Platform & Extensibility
Langfuse is built API-first, allowing engineers to easily export data or build custom tools. Braintrust focuses on powerful in-platform querying via SQL.
| Feature | Langfuse | Braintrust |
|---|---|---|
| API Access | Full CRUD: API-first architecture for all traces, prompts, and platform features. | API available, emphasis is on UI workflows. |
| Querying | API’s to query traces, observations, and scores; Public Metrics API for aggregated analytics. | BTQL & SQL: Proprietary query languages for in-platform analysis. |
| Data Portability | CSV/JSON exports; scheduled exports to S3 storage. | JSON/CSV export via UI or SDK. |
Enterprise Security
Both platforms are SOC 2 Type II and HIPAA compliant. Langfuse offers stricter data residency options through full self-hosting.
| Feature | Langfuse | Braintrust |
|---|---|---|
| Certifications | SOC 2 Type II, ISO 27001, GDPR, HIPAA. | SOC 2 Type II, HIPAA. |
| Deployment | Cloud or Self-Hosted: Air-gapped capable | Restricted: Hybrid model only available on Enterprise tiers (Data plane in VPC, Control plane managed). |
| Governance | SSO, RBAC, and Audit Logs available. | SSO, RBAC, and Audit Logs available. |
Feature Highlights
Langfuse:
- Core Observability: Deep tracing with “Queued Trace Ingestion” for high throughput.
- Agent Debugging: Hierarchical traces specifically designed for complex, multi-step agent reasoning.
- Prompt Management: Agnostic prompt management with a Model Context Protocol (MCP) server.
- Custom Evaluators: Flexible “LLM-as-a-Judge” and remote custom evaluators via API.
Braintrust:
- Experimentation: “Evaluation-first” philosophy with side-by-side prompt comparison views.
- The Proxy: Unified gateway with caching and failover for 100+ models.
- Playground: Integrated environment for rapid iteration on “golden datasets” derived from logs.
- Dataset Management: Specialized tools for curating and versioning testing datasets.
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