ABI stands for Application Binary Interface. It's basically how compiled code interfaces with each other (e.g. how functions are called and values are returned).
In Swift, this is currently not stable, meaning it changes with each version. The result is that you can't use a library compiled with version X of Swift with version Y of Swift. From version 5 onward the ABI will be compatible between version 5 and versions >5.
In Swift, this is currently not stable, meaning it changes with each version. The result is that you can't use a library compiled with version X of Swift with version Y of Swift. From version 5 onward the ABI will be compatible between version 5 and versions >5.