Some consolation if it can be done: Rewrite the flagship app from the ground-up in a new framework. It's a little easier if most functionality is behind APIs.

Some consolation if it can be done: Rewrite the flagship app from the ground-up in a new framework. It's a little easier if most functionality is behind APIs. The requirements are already concrete: make it look and function the same. Express the common business flows with a novel algebra (types). Make logic errors be type errors [1]. These pull requests may never get merged; the feature branch may age for years; at least you gave it an honest go. [1] When people say, "but most business logic bugs aren't type errors," I just want to show them how to make bugs into type errors. -- Matt Parson, from Thinking in Types (2018) by Sandy Maguire.