Biome provides fast error-resilient IDE-ready formatters and linters for JavaScript, TypeScript, JSX, and JSON. It scores 97% compatibility with the Prettier test suite and implements more than 200 linter rules from ESLint, TypeScript ESLint, and others. In this talk I will introduce the unique features of Biome and how I improved the Biome's semantic model to support TypeScript. This will lead us to understand:

• What is a semantic model and how TypeScript types coexist and interact with JavaScript values?
• How to achieve top-notch IDE support using an error-resilient parsers and Concrete Syntax Trees?