Langtail is a low-code platform for building, testing, and monitoring the prompts behind AI applications. Founded in 2023 by Petr Brzek, Tomas Rychlik, and Martin Duris, the team behind the design-handoff tool Avocode, Langtail was built to give both engineers and non-technical teammates a shared workspace for prompt work instead of leaving it scattered across code and spreadsheets.
The platform lets teams run side-by-side comparisons between prompt versions or model providers, attach automated evaluations using natural language rules, pattern matching, or custom code, and log production traffic for debugging after deployment. An AI Firewall layer screens for prompt injection, denial-of-service patterns, and information leakage on top of the core testing tools.
Langtail fits product and engineering teams shipping LLM features who need version control and regression testing for prompts the way they already have it for code. A free plan covers 2 prompts and 1,000 logs a month; the Pro plan starts at $99 a month, Team runs $499 a month, and Enterprise pricing is negotiated separately.
