Kudos to the author for diving in and uncovering the real story here. The Python 3.14 tail-call interpreter is still a nice improvement (any few-percent gain in a language runtime is hard-won), just not a magic 15% free lunch. More importantly, this incident gave us valuable lessons about benchmarking rigor and the importance of testing across environments. It even helped surface a compiler bug that can now be fixed for everyone’s benefit. It’s the kind of deep-dive that makes you double-check the next big performance claim. Perhaps the most thought-provoking question is: how many other “X% faster” results out there are actually due to benchmarking artifacts or unknown regressions? And how can we better guard against these pitfalls in the future?