Bez is a project designed to generate web rendering engines directly from specifications and tests. While building a web engine manually requires hundreds of engineers and many years, Bez aims to significantly reduce the cost and effort required for each additional engine once the generation pipeline is established.
Bez: AI-Driven Project Generates Web Rendering Engines from Specifications
The generation process uses a pipeline where models write multiple candidates based on specification text. These candidates are then run within the engine and checked against the three major shipping browsers—Chromium, Firefox, and WebKit—as well as Web Platform Tests (WPT). If the engine produces results that match the major browsers, the code is committed as standard Rust code.
Current development includes hand-written implementations for the DOM, style, box tree, and fragment tree. The project has already successfully generated several CSS 2.1 layout rules through models, which were admitted after passing checks against the three-browser vote. The engine has reportedly passed 227 recipe cases and 11 usable WPT normal-flow pages. The project's roadmap includes addressing open questions regarding the scope of generated code, the extent of WPT reachability without JavaScript, and the boundary of IDL-generated code.
Sources
- Bez: Generating a browser engine from specs and tests （Hacker News Frontpage, 2026-10-01）
- Blog