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LangWatch
What is LangWatch?
Quick Summary / TL;DRLangWatch is an open source LLM engineering platform for testing, evaluating, observing, and improving AI agents and applications in production. It combines simulations, experiments, evaluations, traces, prompt management, cost tracking, and monitoring in one workflow. Its Langy agent can turn a pro
- Simulation based agent testing
- Production traces and observability
- LLM evaluations and guardrails
About
LangWatch is an open source LLM engineering platform for testing, evaluating, observing, and improving AI agents and applications in production. It combines simulations, experiments, evaluations, traces, prompt management, cost tracking, and monitoring in one workflow. Its Langy agent can turn a product requirement into Scenario tests, inspect failures, open pull requests, and validate changes in CI, connecting AI quality work to software development.
Technical founders can use LangWatch to test AI features before release, run multi turn simulations, inspect production traces, measure token and model costs, evaluate conversations, and gate code changes on evaluation results. It supports agent frameworks and OpenTelemetry instrumentation, while the open source platform can be self hosted. This is useful for teams building AI products that need a repeatable quality loop rather than manual prompt testing.
LangWatch differs from a basic observability dashboard by combining monitoring with simulations and evaluations, and from a pure testing library by providing production interfaces for traces, costs, prompts, and analysis. Buyers should account for instrumentation and evaluation design. Cloud pricing combines seats and event usage, while self hosting removes hosted event charges but shifts infrastructure responsibility to the team.
For FutureStack, LangWatch belongs in Developer Tools because its primary buyer intent is making AI systems reliable in development and production. It is relevant to founders shipping AI agents, voice systems, copilots, or other LLM features where quality, cost, and regression risk matter. Buyers should decide between hosted convenience and self hosting and ensure they have enough test cases and telemetry.
Use Cases
Test AI Agents
Run multi turn simulations and evaluations to test agent behavior before and after code changes.
Monitor Production AI
Inspect traces, tokens, costs, latency, and execution paths across live applications.
Gate Releases With Evals
Use evaluation results in CI so regressions are detected before production.
Control LLM Costs
Track model and token costs across providers and workflows.
Key Features
- Simulation based agent testing
- Production traces and observability
- LLM evaluations and guardrails
- Open source self hosting
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Pricing summary
LangWatch has a free Developer plan, Growth at €29 per core seat monthly plus usage, and custom Enterprise pricing.
Pricing & Plans
Developer
Start building and testing agents for free.
Free
- 50k events monthly
- 14 day data access
- Three scenarios
- Three custom evals
Enterprise
Govern AI systems at scale.
Custom
- Self hosted or hybrid
- Custom retention
- SSO and RBAC
- Audit logs and SLAs
Popular
Growth
Ship production agents with shared tooling.
$29/month
- 200k events included
- Unlimited simulations
- Unlimited evaluations
- 30 day retention
Other pricing notes
- Growth includes 200k events before additional usage charges apply.
- Self hosting avoids hosted event charges but requires your infrastructure.
- Enterprise adds governance, support, and deployment controls.
Pricing last checked: August 2026Official pricing page
Pros & Cons
Pros
- Open source Apache 2.0
- Testing and observability together
- Token and cost tracking
- Agent framework support
- Self hosting
Cons
- Requires instrumentation
- Usage scales with events
- Self hosting needs infrastructure
- Advanced governance is Enterprise
- Evaluation quality depends on scenarios
The Best LangWatch Alternatives
The best LangWatch alternatives are Braintrust, Langfuse, and Helicone.
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