# LangFast — LLM Evaluation Platform for Prompt Testing & Deployment

LangFast (https://langfa.st) is an LLM evaluation platform built for cross-functional product teams to prototype, test, and iterate on LLM prompts 10 times faster. It helps teams ship AI features that don't break in production.

## What LangFast Does

LangFast solves the critical problem of unreliable AI prompts in production. Teams struggle with prompts that break, produce unreliable outputs, broken JSON schemas, hallucinated data, and invisible regressions where every fix breaks something else. LangFast provides a comprehensive platform to test, compare, and version prompts instantly in a shared workspace before deployment.

## Core Features

### 1. Prompt with Experts
- No-code prompt editor allowing subject matter experts to build prompts
- Cross-team collaboration in shared workspaces
- Engineer-free deployments
- Safe testing environment
- Version control for prompts
- Role-based permissions

### 2. Best-in-Class AI Playground
- Dynamic variables for prompt testing
- Structured outputs (JSON schema support)
- Side-by-side comparison of different prompts and models
- Function calling capabilities
- Multimodality support (text, images)
- Full access to all model settings
- No API keys required to get started

### 3. Iterative Evaluation
- Assertions & metrics to validate prompt quality
- Dataset management for systematic testing
- Performance comparison across prompt versions
- Token & cost statistics tracking
- Combines human insight with AI precision
- Thoroughly validates prompts before deployment

## Key Benefits

- Ships stable AI features without production firefighting
- Reduces prompt prototyping hassle
- Eliminates spreadsheet-based prompt management
- Enables non-engineers to build and test prompts
- Catches regressions before they reach production
- Saves time and effort in designing reliable prompts

## Target Audience

Product teams, subject matter experts, AI engineers, and organizations building AI features who need to ensure prompt reliability and quality before production deployment.