# Introduction **three.dev** is a comprehensive AI observability and experimentation platform. Building and iterating with Large Language Models (LLMs) is incredibly powerful, but making changes often feels like a shot in the dark. A minor tweak to a prompt or an upgrade to a new model might perfectly optimize your application, or it could completely derail your user experience. three.dev eliminates this guesswork. The platform empowers you to test the impact of any LLM-related configuration changes quickly, reliably, and rigorously — either offline against historical traffic or live on production sessions — allowing you to move from intuition-based deployments to data-driven engineering. #### Why three.dev? To mitigate the risks of unverified LLM configuration changes, three.dev provides an advanced experimentation framework built around *your* specific definition of success. With three.dev, you can: * **Observe Your Baseline**: Get deep visibility into your current LLM usage so you understand exactly how your AI configuration is performing in production today. * **Iterate Offline Before You Ship**: Replay your historical traffic through a candidate prompt, model, or parameter change. three.dev scores every output with an AI Judge calibrated by domain experts, so you can compare variants without touching production. * **Test with Statistical Rigor**: Confidently prove when one LLM variant outperforms another. three.dev's framework uses Bayesian analysis to ensure your results are reliable. * **Evaluate Holistic Impact**: three.dev reveals the exact impact of your changes across multiple dimensions — including accuracy, cost, and latency — so you can make the best decision for your business. * **Experiment with Total Flexibility**: Whether you are testing a brand-new foundation model, fine-tuning parameters, or just tweaking a system prompt, you can run experiments on absolutely any LLM configuration change you want to make. * **Protect Your Users with Dynamic Routing**: When you roll experiments out to live traffic, three.dev runs them as multi-arm bandits — evaluating multiple variants simultaneously while automatically minimizing traffic to underperforming configurations to protect your users. Stop guessing how your AI behaves. With three.dev, you can observe, experiment, and ship with confidence. Request access at [three.dev](https://three.dev). --- # Agent Instructions: Querying This Documentation If you need additional information that is not directly available in this page, you can query the documentation dynamically by asking a question. Perform an HTTP GET request on the current page URL with the `ask` query parameter: ``` GET https://docs.three.dev/getting-started/readme.md?ask= ``` The question should be specific, self-contained, and written in natural language. The response will contain a direct answer to the question and relevant excerpts and sources from the documentation. Use this mechanism when the answer is not explicitly present in the current page, you need clarification or additional context, or you want to retrieve related documentation sections.