If I update a library function to require a new parameter, then in the same commit, I will also change every application which uses that library to supply the n

If I update a library function to require a new parameter, then in the same commit, I will also change every application which uses that library to supply the new parameter. The promise of the monorepo is "you can pick any random commit from any point in history, and all of those applications and libraries will be compatible with each other". For major changes that are too big to migrate every user in a single commit - create a new API, do development there, migrate users from the old API to the new API, delete the old API. (I wonder if you're coming from a world where library developers and application developers don't have permission to touch each other's code? At FB at least, the library developer would be allowed to create a pull request modifying the application code - though they may need a stamp of approval from the application owner before that pull request is merged into master)