Bug 321693 – REGRESSION (iOS 27 beta 5): GPU process crashes with EXC_GUARD and page reloads when a getUserMedia video element is hidden while MP4 playback starts

• Status: RESOLVED
• Resolution: DUPLICATE
• Component: Media

Created attachment 481051 [details]
Self-contained HTML test case: live getUserMedia camera + MediaPipe PoseLandmarker 0.10.32 (GPU delegate), then camera hidden via display:none while a 2.4 MB base64 data-URL MP4 starts playing in the

Starting with iOS 27.0 beta 5 (24A5408d), the WebKit GPU process (com.apple.WebKit.GPU) crashes with EXC_GUARD (GUARD_TYPE_USER, namespc 31, termination namespace WEBKIT) on our production website, causing Safari to reload the entire page. Reproduces 100% of the time on iPhone 17 Pro Max. Not reproducible on iOS 26.x with the same unchanged production build.

HOSTED PAGE WHERE IT IS REPRODUCIBLE: 
https://ancient-aquamarine-hp3qguza.edgeone.dev/

STEPS TO REPRODUCE:

Open a page that displays a live getUserMedia camera stream in a video element, with an active WebGL2 context processing the frames (MediaPipe pose tracking) and a 2D canvas overlay.
Trigger a UI transition in which, within the same frame: the camera video element becomes display:none (the MediaStream stays attached and active, and JS keeps consuming frames), and a separate muted playsinline MP4 video element begins playback. On iOS our MP4 sources are base64 data: URLs.
RESULTS:
The screen goes black and the page reloads. The device crash log shows com.apple.WebKit.GPU dying with EXC_GUARD at that exact moment (ExcUserFault report attached). Nothing is observable from JavaScript: no error, no console output, the page process is simply reloaded.

EXPECTED:
The transition completes: camera presentation is hidden, MP4 playback starts, no process crash.

REGRESSION TIMELINE (same production build throughout):

iOS 26.x: works correctly.
iOS 27 beta 4: no crash, but the live camera video element intermittently painted letterboxed at a stale smaller size despite object-fit: cover (Apple Feedback FB24038326). Same transition, same subsystem.
iOS 27 beta 5: GPU process now crashes at this transition (Apple Feedback FB24312368, with crash logs and sysdiagnose).
NOTES:

The camera screen before the transition works perfectly, including WebGL and canvas rendering, so this is not a WASM/WebGL init issue. The crash correlates with tearing down the MediaStream-backed video presentation while capture continues, concurrent with a new media decode session starting.
Because the crash is native and the frozen Safari UA hides the OS version from web content, sites have no way to detect affected devices or apply a workaround.
Impact: any site that hides or swaps a live camera view while the stream stays active (video chat PiP, camera filters, fitness/AR apps) breaks with a black screen and reload loop. Our production fitness app is fully unusable on beta 5.

[Radar WebKit Bug Importer]

<rdar://problem/184853682>

[Alexey Proskuryakov]

rdar://184827935

Created attachment 481052 [details]
System Diagnostic Data showing the moment error happens (redacted by removing sensitive ids), full version available in the Feedback Report FB24312368

Added system diagnostic log captured at the moment of the bug. Sensitive ids are removed from this report, full log available in Feedback #FB24312368

[Alexey Proskuryakov]

Thank you for the report, this appears to have been addressed very recently.

*** This bug has been marked as a duplicate of bug 321571 ***