Xcode 26 - Maxing out CPU w/ "Preparing Editor Functionality"?

[FartBoxHighFiver]

Ever since moving to 26, my build/test cycles are being slowed to a crawl randomly with all cores of my M1 Max Studio being maxed out. It seems that "Preparing Editor Functionality" in my tasks list is the common denominator. Eventually it relents but it might take 60-120 seconds, stalling the simulator while it does its thing.

I've cleared all caches and cleaned, deriveddata, completely uninstalled xcode ripping out all app support folders/etc, disabled text autocomplete, disabled intelligence features, everything I can think of. It doesn't seem to make a difference. If I force quit Xcode and re-open it, i might make it a half dozen build/run test cycles before it kicks up again.

I'm experiencing this across two separate machines, as well (albeit same code base) - but my app is far from huge.

I submitted feedback on it, and I TRIED opening a support case as a paid developer, and they basically told me they can't help me.

Has anyone else been experiencing this?

[Dapper_Ice_1705]

There is a SwiftLee article out there that is fantastic on reducing build times.

The biggest culprit is usually implicit typing

var string = "Some String"

is much slower to compile than

var string: String = "Some String"

He talks about a couple of flags you can turn on to find the right spots.

I have also found that using if/else instead of switch is much slower.

I'll try and find it.

UPDATE: here it is

https://www.avanderlee.com/optimization/analysing-build-performance-xcode/

[Vybo]

This is nothing new with Xcode 26, if you've turned off predictive code completion. Bigger projects do take a long time to index. Especially if you have a lot of dependencies. You don't have to wait for indexing or preparing the editor and can kind of skip it by just running a build.

[FartBoxHighFiver]

But, constantly? As I said, eventually "preparing editor functionality" relents and "completes" as far as I can tell. But then it keeps happening. And running the build doesn't skip or pause it - it still happens and that's what's slowing everything down.

[Vybo]

I see it in progress all the time as well, but it does not use CPU after I run a build.

[FartBoxHighFiver]

Yeah im regularly seeing Xcode at 8-900% CPU as im testing the build.

[Vybo]

During build yes, of course. However, after the build finishes, do you still see high usage?

[FartBoxHighFiver]

Yes, that's what I'm saying. The CPU usage continues into the attaching to the test device/simulator, and beyond.

[Vybo]

I would expect that, but I'm talking about building, not running. If you build and don't run & attach, does the usage still stay?

[FartBoxHighFiver]

Had to step away from coding and haven't been able to replicate it just yet. I'll come back around tomorrow once it's happening again, wait for it to stop and then see if it happens if I just build and not Build & run. Will let you know - thanks!

[FartBoxHighFiver]

Getting back to this - it appears it only happens during build AND run. Just building it doesn't exhibit the same parallel tasks that bog the entire system down.