I&#x27;m convinced that the breakage in new C++ compilers is worse than Rust&#x27;s breakage. New C++ compilers and language revisions break more than 4% of code. Likewise with many other languages, such as Ruby. We&#x27;re just very up front about regressions when they do occur.<p>&gt; edit: It&#x27;s not an entirely fair comparison, but for what my ideal stability promise for a programming language would look like, one need not look very far - only as far as Mozilla&#x27;s other programming language.<p>As a matter of fact, JS&#x27;s stability promise is very similar. See my other post for an example in which JS was broken due to, essentially, one of the reasons you cited, and we lived with it. The JS stability promise is not &quot;we will never break any JavaScript in theory with new browser versions&quot;, because that would prevent anyone from, as an extreme example, changing the sorting algorithm for Array.sort. It&#x27;s &quot;we will not break you <i>in practice</i>, except in a carefully delineated set of circumstances.&quot; (Actually, JS&#x27;s stability promise is much weaker than that: its stability in practice is decided by browser consensus and market forces rather than a clear set of rules.)