Xcode 26.6 (17F113) -Onone: UIScene.ActivationState enum comparison crashes at runtime (works in Release)

Summary

On Xcode 26.6 (17F113) / Swift 6.2, a Debug build (-Onone) crashes at runtime when comparing UIScene.ActivationState inside a closure passed to Array.first(where:). The exact same code runs fine when built with optimizations (-O / Release). This looks like an -Onone code-generation (miscompile) bug rather than a logic error in the app.

Environment

• Xcode: 26.6 (17F113)
• Toolchain: Swift 6.2 (Apple default toolchain)
• Optimization: SWIFT_OPTIMIZATION_LEVEL = -Onone (Debug scheme)
• Deployment target: [ iOS xx.x ]
• Run destination: [ Device / Simulator — model, OS version ]
• Configuration: also reproduces in a fresh checkout after Clean Build Folder + DerivedData wipe

Steps to Reproduce

1. Add the following to any app and call it early in the launch path (e.g. from an async context / Task during startup):

import UIKit

enum ScreenUtil {
    static var keyScene: UIWindowScene? {
        let scenes = UIApplication.shared.connectedScenes
            .compactMap { $0 as? UIWindowScene }

        // Crashes here in Debug (-Onone) on Xcode 26.6 (17F113)
        return scenes.first { $0.activationState == .foregroundActive } ?? scenes.first
    }
}

2. Build and run with the Debug scheme (-Onone).
3. The app crashes as soon as keyScene is evaluated.

Expected

keyScene returns the foreground-active UIWindowScene (or the first scene),
identically to the optimized build.

Actual

Immediate crash when the closure evaluates $0.activationState == .foregroundActive.
UIScene.ActivationState is an Objective-C-imported (NSInteger-backed) enum, and
the failure appears tied to how its value is handled under -Onone.

The crash surfaces inside Swift concurrency resume plumbing because keyScene
is reached from an async context at launch. Representative frame:

(1) await resume partial function for partial apply forwarder for
    reabstraction thunk helper ... @isolated(any) @callee_guaranteed @async () -> (@out τ_0_0)
...
->  ldr    x0, [x22, #0x8]     ; faults here
    br     x0
    ; preceding: bl swift_task_dealloc

Reproducibility

- Debug (-Onone): crashes 100%
- Release (-O): works correctly

Workaround

Rewriting the closure comparison as an explicit loop avoids the crash:

static var keyScene: UIWindowScene? {
    let scenes = UIApplication.shared.connectedScenes
        .compactMap { $0 as? UIWindowScene }

    for scene in scenes where scene.activationState == .foregroundActive {
        return scene
    }
    return scenes.first
}

Notes

A sysdiagnose / crash log and a minimal sample project are attached via
Feedback Assistant (FB[ number ]). Happy to provide additional details.