Test prompts on Mistral Medium 1.0, compare outputs across models, and pick the best balance of speed and quality.
Bring your API keys. Pay once, use forever.
Bring your API keys. Just type and run.
Good trade-off for speed, cost, and quality.
Medium vs other models—side-by-side.
Links, transcripts, export.
We don’t train on your data.
Repeatable runs with real inputs.
LangFast empowers hundreds of people to test and iterate on their prompts faster.
The Mistral Medium 1.0 playground is a focused UI for prompt testing and quick eval-style checks on Mistral Medium 1.0—so you can validate behavior before writing integration code.
Whether Mistral Medium 1.0 is the right choice for your use case: quality vs cost, stability vs speed, and how it behaves on your real prompts and edge cases.
Yes. Bring your API keys. LangFast handles routing.
To keep the playground usable (rate limits + abuse prevention) and to enable saved runs, sharing, and team-friendly history.
Regression tests, rubric scoring, style/format compliance, refusal behavior checks, and “must-pass” prompts that shouldn’t degrade over time.
Yes. Save a prompt set, re-run it after changes, and compare outputs across runs to spot regressions.
Yes. Run the same prompt set side-by-side across providers and choose the best model for your constraints.
Yes—export cURL/JS/JSON so engineers can reproduce exactly, including parameters and prompt content.
Yes. Share links for review, approval, or to align on what “good” looks like before you ship.
LangFast is free to use with some basic features. You need to provide your own API keys to run models and use the app. When you add your API keys, you pay the model provider (e.g., OpenAI) for the credits/tokens you use. LangFast premium features can be unlocked with a one-time purchase.
Usage-based: you add volume when you need it. This is designed for startups and small teams who don’t want enterprise plans.
We stream responses through a lightweight proxy. Actual speed depends on Mistral Medium 1.0 and current load; you can compare latency across models directly.
It varies by model. We show key limits (like context window) next to Mistral Medium 1.0 in the model picker.
Yes. Inject structured inputs (customer data, tickets, policies, product specs) to test prompts against realistic cases.
Yes. Validate JSON/schema compliance, headings, tables, and other formatting requirements as part of your eval prompts.
No. We don’t train on your prompts. Sharing is opt-in, and retention is configurable.
Requests route to model providers. See the Data & Privacy page for region and processing details.
Usually yes, subject to each provider’s terms. We link to terms from the model picker.
LangChain helps you build apps/agents. LangFast helps you decide prompts and models first, without building any pipeline.
Those tools are for tracing, datasets, and eval management in production workflows. LangFast is the quickest way to run prompt tests and comparisons interactively.