I've discovered that this is a bug in Xcode 15 that doesn't correctly handle a symlink from ~/Library/Developer to /Users/Shared/Developer The symlink was never a problem in Xcode 14 and earlier. FB12363725

By the way, I'm maintaining a public list of Safari extension bugs, if anyone is interested in adding theirs here: https://github.com/lapcat/SafariExtensions/issues

By the way, this sounds like a great way to get rejected by App Review: "How you do that depends on how your app is built. With Xcode it’s as simple as enabling a restricted entitlements on your app target." I've gotten rejections in the past for unused entitlements.

Quinn, I just got this warning, but I don't want to use TestFlight for Mac. Is there any way to avoid getting the warning?

This has always worked for me in Safari. Are you using Manifest V2 or V3?

According to Chrome's own documentation, "DOM-based timers, such as window.setTimeout() or window.setInterval(), are not honored in non-persistent background scripts if they trigger when the event page is dormant. Instead, use the alarms API." https://developer.chrome.com/docs/extensions/mv2/background_migration/#timers