It's probably borderline due to the opt-in mechanism, but Go did make a technically backwards-incompatible change to how its for loops work in 1.22 [0].

PHP has had breaking changes [1].

Ruby has had breaking changes [2] (at the very least under "Compatibility issues")

Not entirely sure whether this counts, but ECMAScript has had breaking changes [3].

[0]: https://go.dev/blog/loopvar-preview

[1]: https://www.php.net/manual/en/migration80.incompatible.php

[2]: https://www.ruby-lang.org/en/news/2025/12/25/ruby-4-0-0-rele...

[3]: https://tc39.es/ecma262/2025/#sec-additions-and-changes-that...

Yes, most of them.

C# for instance isn't such a "small language", it has grown, but code from older versions, that does not use the newer features will almost always compile and work as before.

breaking changes are for corner cases, e.g. https://github.com/dotnet/roslyn/blob/main/docs/compilers/CS...