This is not only true for the open-source, widely used software, but also for internal software. The existence of companies with big mono repositories to support dynamic rhythm of changes that do not break in unknown parts is a good illustration of how important to have the ability to refactor without the fear.

Even in the pre-LLM era we had a technical ability to do some changes without the fear which we didn't really adopt. For over 20 years we already had tools that implement a number of deterministic refactorings for typed languages. If our change consisted of only a sequence of such deterministic changes – we could automatically generate codebase migration scripts together with the new versions of our libraries. And maybe we could even search for all the usages of our libraries on the GitHub and programmatically produce PRs with all the needed changes.

Today, with all the progress in LLMs it's not hard to imagine that instead (or together with) automated migration scripts we can distribute some automatically generated migration prompts. And for all the opensoruce code, we can actually validate the results of our migrations (by pulling all the code dependent on our library, applying migration prompts, building and running tests) – and everything that is validatable, usually reach very confident levels with LLMs.

It's not hard to imagine even better LLMs in future with the ability to do even more complex refactorings. And this might remove a lot of fear associated with the changes, which in turn will significantly improve the speed of innovation for old projects where a lot of historical decisions are cemented in the public interface.

This is the future of software engineering I would want to see, and I'm curious to hear what are your thoughts about this?

P.S. Migrating from one computer language to another should become a matter of "prompted change" at some point too!