I have the same problem. Just updated today to 12.0.1. This was working in Xcode 12. I'm really, really appalled at how low the quality is with Apple's Dev tools these days, what with all the simulator crashes and the broken navigator views. Perhaps Apple should open-source Xcode so that we can fix their bugs for them.

I threw the 12.0.1 (12A7300) AppStore download into the trash, downloaded the 12.0 (12A7209) release from the Developer Downloads area (all 11.21 GB!) and I can see the simulators again. Also, pulling up the Developer Documentation directly from the Window menu does NOT crash the app. From other reports, this was only an issue with the AppStore download of 12.0. Again, I ask what the heck is happening at Apple? The AppStore releases are sufficiently different from the direct downloads that I can't trust them. Build 12A7209 from the AppStore crashed when you brought up the documentation. Build 12A7300 "fixes" the documentation crash, but now removes the simulators. In the release notes, the only thing mentioned was fixing the documentation crash, but I'm assuming there have been 91 builds since 12A7209. It seems like fixedbugs / regressionbugs == Constant.

I'm having the same problem, and it's driving me insane! The iOS 14 simulator is the worst offender, where multiple daemon processes seem to crash when the simulator finishes launch, and then again when the simulator is closed. I reverted to using an iOS 13.5 simulator and, although I do indeed experience less crashes, they are still occur and are similar (they're all SimulatorTrampoline related). It's almost as if there's some common code in the daemons that is not properly checking the existence of source/destination objects before trying to interact and so you get a crash. I've submitted my sysdiagnose and simdiagnose reports, as well as examples in FB8702058, so hopefully Apple is able to figure things out. I can get the following sequence to reliably happen: With no simulator running, start Xcode 12 and load project. Use the iPhone SE 2nd Gen iOS 14 simulator and run the app. Once the simulator starts and completes its startup operations, you’ll get the following crashes: CalendarWidgetExtension, NewsTag, NewsToday2. The app will run. Depending on your app composition, you will probably get more simulator daemon crashes. Terminate the app. Terminate Xcode. Terminate the simulator. After a time (15 seconds?) you’ll get another crash: bulletindistributord. You may get other crashes when the simulator closes, but bulletindistributord is always the last. The simulator instability began for me in the Xcode 11 line, where you'd routinely get maild crashes in the simulators. And this happened across multiple machines, each with different dev environments, so it's not just an isolate case for me. But Xcode 12 is now completely infected by the crashes.

Throw the 12.0.1 (12A7300) AppStore download into the trash, and then download the 12.0 (12A7209) release from the Developer Downloads area (all 11.21 GB!) and you'll see the simulators again. Also, pulling up the Developer Documentation directly from the Window menu shouldn't crash the app; this was only an issue with the AppStore download of 12.0, not the full direct download.

@mcebrian: I'm so glad you confirmed the same behavior I'm experiencing. I've been searching across the internet ever since Xcode 11.5 started these crashes and couldn't find anything. I'm glad it's not just me.

Check out some of the other threads. People have been howling about this one. You can get fewer crashes by downloading one of the older iOS simulators, e.g., 13.5. You'll still get crashes when closing the simulator, but less at startup. However, you'll need Xcode 12.0. Xcode 12.0.1 has a bug where it no longer shows any of the simulators for download.

No one has figured out a good way to fix this yet. Please submit a bug report to Apple, using both macOS and simctl to generate sysdiagnose files: xcrun simctl diagnose sudo sysdiagnose This is a fundamental problem affecting a lot of people, where the simulator daemon processes are crashing right and left, and the only way to get Apple's attention is to submit bug reports. But submit the sysdiagnose files so that they can figure out what's going on. In the interim, you can download the older iOS simulators, e.g., 13.5, and you will get fewer daemon crashes. But you'll need to use the Xcode 12.0 installation because Apple broke the simulator downloads when they released Xcode 12.0.1.

This is what always works for me: Download the desired Xcode*.xip archive file from the Downloads area. Move the Xcode*.xip archive file out of your Downloads folder to another location, e.g., the Desktop. Move the /Applications/Xcode.app file to the trash. Empty trash. Double-click the downloaded Xcode*.xip archive and let it expand into an Xcode.app file. Move the new Xcode.app file to your /Applications folder. Run the new Xcode and, if prompted to install additional components, accept and let it complete. At this point, you should be good to go. The main thing that can cause problems is insufficient free disk space. A fully expanded Xcode.app from a downloaded Xcode*.xip archive can be up to 29 GB (yeah, wow, I know!), so having at least 50 GB free space on the drive holding the Xcode*.xip archive file after download is probably a good rule of thumb. If this still doesn't work, you may need to completely remove Xcode (remove the application and its supporting directories in your ~/Library and /Library directories) and try again.

Xcode 12.1 GM seed is same version as App Store Xcode 12.1 version. Both are versioned as build 12A7403.

@TomE You are absolutely awesome. Thank you. While I really wish Apple would actually prioritize fixing their core bugs instead of relying on the lottery to groom their backlog, this at least lets me get my automated tests running again.

In another related "Simulator crash reports" thread, user @TomE recommends using the CrashReporterPrefs utility to set the crash reporting mode to "Basic." The utility is in the "Utilities" folder of the "Additional Tools for Xcode" item in the Developer Downloads area. Mine was set to "Developer" and after I set it to "Basic" I stopped getting the pop-ups and I can run my automated tests again. While I really wish Apple would actually prioritize fixing their core bugs instead of relying on the lottery to groom their backlog, this at least lets me get back to being productive again.

I have the same problem. Although I had the 11.3 RC installation pending in my System Preferences when it got released last Tuesday, I held off installing it because I needed to finish out my development activities on my current installation for that week. I had planned on installing 11.3 RC over the weekend, but to my dismay when I went to my System Preferences, it had already switched to the 11.4 beta 1 release. I even tried restoring my settings and downloading the developer profile again, but it kept coming up 11.4. I don't want 11.4 yet; I want 11.3 RC so I can release updated apps. So frustrating. I submitted a Feedback but report, but I get the feeling Apple no longer reads those items.

I'm having the same problem. Can't use the Safari inspector because it's broken [again], and can't download the tech preview because it's "coming soon." But why can't Apple post the existing build until they actually get the "coming soon" build posted? So aggravating!

I've also encountered the problem with newly generated AAC files that are of iTunes Plus (256 kbps) quality. They play correctly on my MacBook Pro (Ventura 13.5.2) Music app. They do not play correctly on my iPhone 14 Pro Max (iOS 16.6.1) Music app; they exibit the gap between the songs. However, putting the device into Airplane mode allows the music to play without gaps. So I believe it's a threading priority issue where Apple is communicating back to its servers while I'm playing MY OWN music, and they interrupt the playback to send data. So, first and foremost, they're degrading the user experience in favor of what I suspect to be data mining. Secondly ... it appears they're data mining! I really hope I'm wrong about this, and I wish someone at Apple would at least fess up to the issue. I'm really tempted to start sniffing the Wi-Fi traffic from my phone during playback to see what they're doing. Very aggravating!

Just verified that this still happens on iOS 17 RC.