LangWatch
Verified Oct 16, 2026 ActiveSimulates user scenarios against LLM agents, scores the answers and traces every step in production
Listed on EffectHub ·
Pricing
- Pricing model
- Freemium
Developer is free forever: 50k events a month, 14-day data access, 2 users, 3 scenarios. Growth is priced in euros — EUR 29 per core seat per month with 200k events included, then EUR 5 per additional 100k, 30-day retention — so no USD figure is published. Enterprise is quote-only.
Use tool ↗About LangWatch
LangWatch is a testing and monitoring platform for LLM agents. It runs simulated user scenarios against an agent to surface failures before release, scores responses for quality and accuracy with configurable evaluators, and traces each agent step in production with cost and latency attached. Around that sit prompt versioning, red-teaming, voice-agent testing and governance reporting, which is why it turns up filed under AI security as often as under observability. The core is open source under Apache 2.0, so self-hosting is an option. The cloud Developer tier is free; Growth is billed per core seat in euros with an included event allowance. LangWatch B.V. is based in Amsterdam.
- Platforms
- Web · API
- API
- Yes
- Last verified
- Oct 16, 2026
Verified sources
- Agent simulation, LLM evaluation, observability, prompt management, red-teaming and voice testing; Apache 2.0 open source; LangWatch B.V., Amsterdamlangwatch.ai ↗
- Developer free with 50k events/month and 14-day access; Growth EUR 29 per core seat/month with 200k events then EUR 5 per 100k; Enterprise customlangwatch.ai ↗
Is LangWatch legit?
We don’t label tools safe or unsafe. Below are the records we checked ourselves, each with the date we read it.
- Domain registered
- Sep 17, 2023 (3 years ago)Registry record (RDAP), registrar GoDaddy.com, LLC, looked up Sep 21, 2026
- TLS certificate
- Issued by Google Trust Services, valid until Jan 11, 2027Seen in our own connection to the site on Oct 16, 2026
- Last checked
- Oct 16, 2026The site answered
- Operated by
- LangWatch B.V., NetherlandsOur research, card verified Aug 23, 2026
Pros & cons of LangWatch
The scenario simulation is what sets it apart: instead of only watching production traces, it drives synthetic users at your agent so failures show up before release. Apache 2.0 licensing means you can self-host if the euro seat pricing or data residency bothers you.
Pros
- Agent simulation drives realistic scenarios rather than only recording production
- Evaluators, traces and prompt versioning live in the same product
- Core is open source under Apache 2.0, so self-hosting avoids seat pricing
- Free Developer tier includes 50k events a month rather than a time-limited trial
Cons
- Growth is billed per core seat, so cost scales with team size as well as volume
- Free tier keeps data only 14 days and caps you at 2 users
- Pricing is euro-denominated with no USD equivalent published
- Event overage at EUR 5 per 100k is easy to overlook when agents get chatty
Best for
- Teams shipping conversational agents that need pre-release regression testing
- Engineers who want traces, evals and prompt versions in one tool
- European teams needing EU-hosted or self-hosted LLM observability
Not for
- Solo builders whose needs stop at basic request logging
- Buyers who need USD pricing and a US contracting entity
Watch out: Growth is priced per 'core seat' rather than per user — confirm which of your engineers count as core seats before budgeting.