TSConfig

TypeScript 4.5 introduced the possibility of substituting the default lib files with custom ones. All built-in library files would first try to be resolved from packages named @typescript/lib-*. For example, you could lock your dom libraries onto a specific version of the @types/web package with the following package.json:

json
{
    "devDependencies": {
       "@typescript/lib-dom": "npm:@types/web@0.0.199"
     }
}

When installed, a package called @typescript/lib-dom should exist, and TypeScript would always look there when searching for lib.dom.d.ts.

The --libReplacement flag allows you to disable this behavior. If you’re not using any @typescript/lib-* packages, you can now disable those package lookups with --libReplacement false. In the future, --libReplacement false may become the default, so if you currently rely on the behavior you should consider explicitly enabling it with --libReplacement true.