We are migrating the Vue Language Features extension from our own TS LSP server to the TS plugin. I found that some features of typescript-language-features cannot be configured. I can only modify typescript-language-features in a very hacky way. Code to add supported language mode:

https://github.com/vuejs/language-tools/pull/3788/files#diff-3c2b2dc57146f5d52dc996ede798d28b5e6163dcd75762900a25803398a099edR187-R207

I think it is feasible to expose a function like addSupportedLanguageMode() through getAPI(), or configure through contributions.

In addition to Vue, Astro, MDX, and Svelte may also be migrated to TS plugin soon, which will be helpful for related extensions.