Evals aren’t enough. Your agents need to be simulated.

Stop scoring what already happened. Start preventing it.

Braintrust scores what your AI already did. LangWatch simulates what your agent will do, before it ever reaches a real user. That is the difference between chasing problems and preventing them.

Join thousands of AI developers shipping reliable agents with LangWatch.

release timeline · v0.4.0
friday 14:22 UTC
scenario suite
judge replay
ship
prod traffic
eval after?
LangWatch
Prevented in sim
tool_failure on refund_lookup, caught at turn-04 of run #1142.
Score-only stack
Logged after the fact
42 failed conversations in the dashboard. 42 already-angry users.
The Braintrust alternative.

How LangWatch compares to Braintrust.

Five things teams care about when picking a quality layer for agents. Each row shows what Braintrust ships today and what LangWatch gives you on day one.

01
Pre-production simulation
Full agent simulation suite

Scenario-based testing with tools, persistent state, a virtual user, and a judge. Catch failures in a sandbox, not in production.

Not available

Braintrust generates eval datasets from existing traces. No pre-production simulation with state, tools, or virtual users.

02
Evaluator library
Eval library +

Strong pre-built evaluators with bring-your-own logic. Run from code or platform UI, online or offline.

Auto-evals

Solid evaluations, but predominantly used by developers. Teams that need to hand it to less technical people tend to come to LangWatch.

03
Source code & deploy
Open source + self-hosted

Audit every component. Self-host with Docker in minutes at zero cost. Zero vendor lock-in at any tier.

Proprietary SaaS

Closed codebase. You cannot inspect what processes your trace data or how it is stored.

04
Who can use it
Engineers + domain experts

Friendly platform UI for domain experts. Powerful APIs and SDKs for engineers. Both edit the same source of truth.

Engineers, mostly

Built for engineers. Human review queues exist but non-technical stakeholders have no real seat at the quality table.

05
Voice agents
Voice-native simulation

Full STT → LLM → TTS pipeline simulation with real audio in and out. Unique in the LLMOps category.

Not available

Text-only platform. Teams building voice AI products have no testing path here.

Three reasons agent teams choose LangWatch.

before prodafter prod
Simulate, don’t guess

Thousands of realistic multi-turn conversations against your full agent stack, before a single user interaction.

helm install langwatch ./langwatch→ 12 pods up. control plane ready.license: Apache-2.0 · cost: $0
Self-host without permission

Apache 2.0 codebase. Helm chart for Kubernetes. No enterprise contract required to run it on your own infrastructure.

engpmlegaldomainqa
A seat for the whole team

Domain experts build scenarios in the UI. PMs review quality. Legal annotates flagged outputs. All without touching code.

Auto-evals showed us scores. Simulations showed us where the agent would actually break. That is the gap we needed to close before launch.
VP Engineering · Healthcare AI platform
94%
regressions caught pre-prod
5 min
time-to-first-eval
any
frameworks supported
$0
cost to start

Stop scoring failures. Start preventing them.

LangWatch is free to start. Connect in minutes, any framework, any model. Agent simulation included on day one.