Hi all, hoping to shed some light on this issue and provide a clear path out of it.

Let's assume the following scenario:

• You have a big tRPC api with many routers, nested ones...etc
• You're using zod as well in the api.

These two alone could be a challenge on the tsserver because of the nature in how they try to provide you with a lot of type-safety and do really smart things to get there, however that also makes it very hard on the TS LSP to calculate the types of things on the fly quickly as you are coding, hence why you see very slow auto-completions, errors being rendered on the editor...etc

Now how do we get around this?

• If you are in a monorepo, you will need to build your tRPC api package and all of the other packages that are used in that api package, you need to generate the .d.ts and .js file combos in something like a dist folder, then export them in the package.json of the package. It is much much faster for the TS LSP to calculate the types of things if it's already built.
• If you are not in a monorepo, it's probably going to be almost impossible to resolve this issue unless you move to a monorepo just because of the nature in that there is no concept of packages, making the whole compilation and using that very hard.

There are also many ways of having TypeScript setup in your monorepo, every single one of them will have this issue apart from actually building your packages before consuming them (built-packages) approach.

I have a reproduction/demo repository here: https://github.com/ixahmedxi/typescript-monorepo-demo

There are 4 branches apart from the main branch that each sets up TypeScript in a monorepo in a different way, the api generates 100 complex tRPC routers on postinstall. The only branch with no TS LSP performance issues is the built-packages branch, this is what you need to fully resolve this issue.