macOS 27: EXC_BAD_ACCESS in libqcocoa during NSAccessibility queries

Operating System

macOS

Version of Prism Launcher

Prism Launcher 11.1.0 and 11.0.3

Version of Qt

Qt 6.9.3

Description of bug

[!note] I used ChatGPT to help analyze the crash reports and narrow down the issue. I manually verified the findings and reproduced the behavior described above.

Prism Launcher intermittently crashes on macOS 27 while an Accessibility client is active.

In my case, Codex Computer Use is enabled. The macOS crash reports consistently show the crash occurring on the main thread inside Qt's Cocoa platform plugin while AppKit is servicing an Accessibility request:

Thread 0 Crashed:: Dispatch queue: com.apple.main-thread

0   libqcocoa.dylib
1   AppKit       -[NSAccessibilityAttributeAccessorInfo getAttributeValue:forObject:]
2   AppKit       ___NSAccessibilityEntryPointValueForAttribute_block_invoke
3   AppKit       NSAccessibilityPerformEntryPointObject
4   AppKit       _NSAccessibilityEntryPointValueForAttribute
5   AppKit       -[NSObject(NSAccessibilityInternal) _accessibilityValueForAttribute:clientError:]
6   AppKit       CopyAppKitUIElementAttributeValueNoCatch
7   AppKit       CopyMultipleAttributeValues
8   HIServices   _AXXMIGCopyMultipleAttributeValues

The exception is:

Exception Type:    EXC_BAD_ACCESS (SIGSEGV)
Exception Subtype: KERN_INVALID_ADDRESS
Termination Reason: Namespace SIGNAL, Code 11, Segmentation fault: 11

Both 11.0.3 and 11.1.0 crash in the same area of libqcocoa.dylib. The stack also shows that the Add Instance dialog was active at the time of the crash:

QDialog::exec()
MainWindow::addInstance(...)
MainWindow::on_actionAddInstance_triggered()

The crash report additionally contains:

voucherInfos: [{"proximateName":"SkyComputerUseService", ...}]

so this appears to happen while macOS Accessibility is querying Prism's UI. This is intermittent rather than 100% deterministic. Sometimes I can use the launcher normally for a while before it crashes.

Steps to reproduce

1. Use macOS 27.0.
2. Enabled Codex Computer on "Device control and Data access" settings.
3. Launch Prism Launcher.
4. Open the "Add Instance" button.
5. Close the popup.
6. Repeat 4 and 5 for a while.

Other information

I also tested current develop branch with a custom Qt build that has Accessibility disabled, and the problem was fixed. fork

• Qt 6.11.2 with FEATURE_accessibility=OFF

This issue is unique

• I have searched the issue tracker and did not find an issue describing my bug.