LangFast

LangFast

Langfa.st
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About

Braintrust is the enterprise-grade stack for building AI products. From evaluations, to prompt playground, to data management, we take uncertainty and tedium out of incorporating AI into your business. Compare multiple prompts, benchmarks, and respective input/output pairs between runs. Tinker ephemerally, or turn your draft into an experiment to evaluate over a large dataset. Leverage Braintrust in your continuous integration workflow so you can track progress on your main branch, and automatically compare new experiments to what’s live before you ship. Easily capture rated examples from staging & production, evaluate them, and incorporate them into “golden” datasets. Datasets reside in your cloud and are automatically versioned, so you can evolve them without the risk of breaking evaluations that depend on them.

About

LangFast is a lightweight prompt testing platform designed for product teams, prompt engineers, and developers working with LLMs. It offers instant access to a customizable prompt playground—no signup required. Users can build, test, and share prompt templates using Jinja2 syntax with real-time raw outputs directly from the LLM, without any API abstractions. LangFast eliminates the friction of manual testing by letting teams validate prompts, iterate faster, and collaborate more effectively. Built by a team with experience scaling AI SaaS to 15M+ users, LangFast gives you full control over the prompt development process—while keeping costs predictable through a simple pay-as-you-go model.

Platforms Supported

Windows
Mac
Linux
Cloud
On-Premises
iPhone
iPad
Android
Chromebook

Platforms Supported

Windows
Mac
Linux
Cloud
On-Premises
iPhone
iPad
Android
Chromebook

Audience

Organizations in need of a platform to rapidly ship AI without guesswork

Audience

Product teams, software engineers, prompt engineers, AI developers, ML researchers, startup founders, and technical writers working on AI-powered features or language model integrations.

Support

Phone Support
24/7 Live Support
Online

Support

Phone Support
24/7 Live Support
Online

API

Offers API

API

Offers API

Screenshots and Videos

Screenshots and Videos

No images available

Pricing

No information available.
Free Version
Free Trial

Pricing

$60 one time
Free Version
Free Trial

Reviews/Ratings

Overall 0.0 / 5
ease 0.0 / 5
features 0.0 / 5
design 0.0 / 5
support 0.0 / 5

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Reviews/Ratings

Overall 0.0 / 5
ease 0.0 / 5
features 0.0 / 5
design 0.0 / 5
support 0.0 / 5

This software hasn't been reviewed yet. Be the first to provide a review:

Review this Software

Training

Documentation
Webinars
Live Online
In Person

Training

Documentation
Webinars
Live Online
In Person

Company Information

Braintrust
Founded: 2023
United States
www.braintrust.dev/

Company Information

Langfa.st
Founded: 2025
United States
langfa.st/new

Alternatives

Alternatives

Vellum AI

Vellum AI

Vellum

Categories

Categories

Integrations

No info available.

Integrations

No info available.
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