A recent example.

Go values not breaking current code much more than adding features.

Rust also values not breaking current code very highly; it only happens for soundness fixes.

"stability" is a tough word; some people use it to mean "doesn't change", and others use it to mean "append-only change."

Yet even Go has several new features not present in version 1.0 and 2.0 roadmap is underway.

Languages are software products, they are evolve to fulfill the market needs or they die.

Adding features? Sure, as long as current code keeps compiling.

Even C removes features from time to time.

ANSI C compilers are not required to still support K&R C, Annex K was compulsory on C99, became optional on C11, gets() was removed, some semantics corrected,....

Every non-toy, non-academic programming language should be non breaking. I know, there is a gray zone and some do not give a sh*. But as a company it is really hard investing into something that is breaking.

That leaves C out then.

Rust evolution breaks less code than C++.