> Windows on ARM hasn't made it up to Tier 1 yet.

Windows on ARM is irelevant. Surface is Microsoft's offering to keep execs away from Apple. And just like Apple, they are toys. All relevant Windows software is x86(-64).

Not true. Key point: "Cloud savings"

To be clear, tier 2 targets are still expected to be well supported. It just doesn't require CI to pass after every PR (meaning PRs aren't blocked on fixing tier 2 specific issues). However, the target is officially distributed and target maintainers are still expected to fix any blocking issues before a release. If they can't then it's likely the target will be demoted to tier 3.

Windows on ARM couldn't be tier 1 until recently as there weren't Windows ARM github runners. Now that there are I think it likely that it'll be promoted to tier 1.

Does that end up meaning, in practice, that stable releases are never broken, but nightly might be, for a tier 2 target?

More or less, yes. It is guaranteed that tier 2 at least builds so they'll be a nightly available every day though it's possible they might have a serious bug. To be honest though that's always a risk for nightlies even with tier 1 targets. Tests don't catch every potential problem (even if they do catch a lot) which is why there is a beta period before a release.

> Interestingly, Windows on ARM hasn't made it up to Tier 1 yet.

An RFC for that has been submitted recently: https://github.com/rust-lang/rfcs/pull/3817

the problem with Windows on Arm is CI. Qualcomm cancelled their dev kit, so you run graviton/Ampere VMs, but it's pretty difficult to do automated tests on the hardware that all 5 users have.

There are Windows ARM GitHub runners now. I'm honestly not sure the dev kit would have helped, the existing Windows ARM hardware could be had for cheaper - just nobody cared to bother with it.

This is looking to go for it though https://github.com/dpaoliello/rfcs/blob/aarch64tier1/text/38... but we'll see if there is enough interest.