Thanks for the suggestion, Adam!
We’re still figuring out the best way for us to surface the backend logic for node. The good news is that most of the logic lives in App Bridge, and you can use the authenticatedFetch fetch implementation with pretty much any modern JS framework (see more about authenticatedFetch here: https://shopify.dev/tools/app-bridge/authentication#setup).
I did notice that a community member created a helper to validate the session token for node: https://github.com/leighs-hammer/shopify-jwt-auth-verify You could see if that meets your needs.