Braintrust vs Langfuse

When to pick Braintrust

• You never want to think about seats. There is no per-seat charge on any tier, and unlimited users, projects, datasets, playgrounds, and experiments are included even on the free Starter plan — Langfuse Cloud caps Hobby at 2 users.
• Evaluation is the centre of your workflow, not a side feature. Experiments diff scores across versioned datasets, scorers span LLM-as-a-judge, code, and the open-source autoevals library, and the Loop agent generates test cases and proposes better prompts and scorers on its own.
• You are scaling volume rather than headcount. Overage rates get cheaper on Pro — $3 per GB and $1.50 per 1,000 scores against $4 and $2.50 on Starter — so unit economics improve as you grow, and qualifying early-stage startups can get 6-12 months of Pro free.

When to pick Langfuse

• Cost is the constraint. Cloud Core is $29/month against Braintrust Pro at $249, and the MIT core self-hosts for free with no functional gating — a difference of an order of magnitude for a small team.
• You need the data in your own infrastructure. Langfuse deploys via Docker, Kubernetes, AWS, Azure, or GCP under MIT, while Braintrust has no free self-hosted option and its Enterprise BYOC still leaves the control plane managed elsewhere.
• Governance cannot wait for an Enterprise contract. Org-level RBAC and enterprise SSO are in the open-source build, and SOC 2 and ISO 27001 reports arrive at $199/month, where Braintrust reserves SSO, audit logging, and SOC 2 attestation for Enterprise entirely.

Bottom line

Langfuse wins on price, licensing, and how early you can get security controls, which makes it the default for most teams — especially anyone who needs traces to stay inside their own cloud. Braintrust earns its premium in two specific situations: large teams, because nothing is charged per seat at any tier, and eval-heavy work, where experiments, configurable scorers, and the Loop agent are more opinionated than Langfuse’s equivalents. Budget carefully either way, because both bill on volume rather than headline price: Braintrust stacks a flat platform fee on metered processed data, scores, and Topics tokens, and its Pro Topics credit drops from $249 to $100 a month after 1 September 2026; Langfuse Cloud charges $8 per 100k units beyond the included quota, and self-hosting at scale means running Postgres, ClickHouse, and Redis or S3 yourself. Both are developer-facing tools requiring SDK instrumentation, and both cover tracing, evals, prompt management, and datasets in one place.