Instead of rejecting the extension with a reasonable, polite error, Safari on Tahoe crashes when the manifest.json file is properly formatted for Firefox instead of Chrome.
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Translated Report (Full Report Below)
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Process: Safari [88741]
Path: /Volumes/VOLUME/*/Safari.app/Contents/MacOS/Safari
Identifier: com.apple.Safari
Version: 26.4 (21624.1.16.11.4)
Build Info: Safari-7624001016011004~1
Code Type: X86-64 (Native)
Role: Background
Parent Process: launchd [1]
Coalition: com.apple.Safari [97627]
User ID: 503
Date/Time: 2026-07-19 21:54:12.9042 -0700
Launch Time: 2026-07-18 10:38:48.3440 -0700
Hardware Model: MacBookPro16,2
OS Version: macOS 26.4.1 (25E253)
Release Type: User
Bridge OS Version: 10.4 (23P4242)
Crash Reporter Key: E10AFED8-44D7-B68A-A06B-6237E159410E
Incident Identifier: 0E512E91-4C4E-4D10-9518-6F0757C5E943
Sleep/Wake UUID: 5396E9EB-E238-4D56-BE08-D966DCE12528
Time Awake Since Boot: 580000 seconds
Time Since Wake: 12175 seconds
System Integrity Protection: enabled
Triggered by Thread: 0, Dispatch Queue: com.apple.main-thread
Exception Type: EXC_BAD_ACCESS (SIGSEGV)
Exception Subtype: UNKNOWN_0xD at 0x0000000000000000
Exception Codes: 0x000000000000000d, 0x0000000000000000
Termination Reason: Namespace SIGNAL, Code 11, Segmentation fault: 11
Terminating Process: exc handler [88741]
VM Region Info: 0 is not in any region. Bytes before following region: 4311683072
REGION TYPE START - END [ VSIZE] PRT/MAX SHRMOD REGION DETAIL
UNUSED SPACE AT START
--->
__TEXT 100ff1000-100ff2000 [ 4K] r-x/r-x SM=COW /System/Volumes/Preboot/Cryptexes/App/System/Applications/Safari.app/Contents/MacOS/Safari
Thread 0 Crashed:: Dispatch queue: com.apple.main-thread
0 libunwind.dylib 0x7ff821b974b0 _Unwind_RaiseException + 240
1 libc++abi.dylib 0x7ff811ba5db4 __cxa_throw + 61
2 libobjc.A.dylib 0x7ff8117b8131 objc_exception_throw + 317
3 CoreFoundation 0x7ff811c832b7 -[__NSDictionaryM setObject:forKeyedSubscript:] + 1215
4 SafariSharedUI 0x7ffa19bdc6b5 -[WBSSafariExtensionStateObserver _addNamesForExtension:toMap:] + 205
5 SafariSharedUI 0x7ffa19bdc22d -[WBSSafariExtensionStateObserver _handleExtensionWasAdded:] + 208
6 CoreFoundation 0x7ff811cb1434 __CFNOTIFICATIONCENTER_IS_CALLING_OUT_TO_AN_OBSERVER__ + 137
7 CoreFoundation 0x7ff811d388da ___CFXRegistrationPost_block_invoke + 88
8 CoreFoundation 0x7ff811d3882d _CFXRegistrationPost + 540
9 CoreFoundation 0x7ff811c8131c _CFXNotificationPost + 769
10 Foundation 0x7ff812ed3cd1 -[NSNotificationCenter postNotificationName:object:userInfo:] + 82
11 SafariSharedUI 0x7ffa19b769b8 -[WBSExtensionsController _loadExtensions:skipEqualityCheck:] + 2505
12 SafariSharedUI 0x7ffa19b74ec7 __59-[WBSExtensionsController loadSuitableDiscoveredExtensions]_block_invoke + 62
13 SafariSharedUI 0x7ffa19b74da0 -[WBSExtensionsController loadSuitableDiscoveredExtensions] + 133
14 SafariSharedUI 0x7ffa19c5cdd2 -[WBSWebExtensionsController loadSuitableDiscoveredExtensions] + 46
15 SafariSharedUI 0x7ffa19b7490f -[WBSExtensionsController _beginMatchingExtensionsWithAttributesCompletedWithMatchingExtensions:] + 537
16 SafariSharedUI 0x7ffa19b7460f -[WBSExtensionsController _extensionDiscoveryHasNewResults:] + 331
17 libdispatch.dylib 0x7ff811a47616 _dispatch_call_block_and_release + 12
18 libdispatch.dylib 0x7ff811a5d8b2 _dispatch_client_callout + 6
19 libdispatch.dylib 0x7ff811a78679 _dispatch_main_queue_drain.cold.6 + 842
20 libdispatch.dylib 0x7ff811a53dc4 _dispatch_main_queue_drain + 107
21 libdispatch.dylib 0x7ff811a53d4b _dispatch_main_queue_callback_4CF + 31
22 CoreFoundation 0x7ff811cf66b3 __CFRUNLOOP_IS_SERVICING_THE_MAIN_DISPATCH_QUEUE__ + 9
23 CoreFoundation 0x7ff811cbb15c __CFRunLoopRun + 2382
24 CoreFoundation 0x7ff811d828b7 _CFRunLoopRunSpecificWithOptions + 496
25 HIToolbox 0x7ff81e9f1b8b RunCurrentEventLoopInMode + 283
26 HIToolbox 0x7ff81e9f4c4d ReceiveNextEventCommon + 599
27 HIToolbox 0x7ff81eb7d0ba _BlockUntilNextEventMatchingListInMode + 37
28 AppKit 0x7ff816236d34 _DPSBlockUntilNextEventMatchingListInMode + 172
29 AppKit 0x7ff815b2c9d5 _DPSNextEvent + 800
30 AppKit 0x7ff8167dab53 -[NSApplication(NSEventRouting) _nextEventMatchingEventMask:untilDate:inMode:dequeue:] + 1265
31 AppKit 0x7ff8167da629 -[NSApplication(NSEventRouting) nextEventMatchingMask:untilDate:inMode:dequeue:] + 67
32 Safari 0x7ff927853839 -[BrowserApplication nextEventMatchingMask:untilDate:inMode:dequeue:] + 214
33 AppKit 0x7ff815b1d868 -[NSApplication run] + 472
34 AppKit 0x7ff815af34cd NSApplicationMain + 800
35 Safari 0x7ff92783fac1 SafariMain + 529
36 dyld 0x7ff81182abb8 start + 3240
Thread 1:: com.apple.NSEventThread
0 libsystem_kernel.dylib 0x7ff811bbcb4e mach_msg2_trap + 10
1 libsystem_kernel.dylib 0x7ff811bcaf49 mach_msg2_internal + 83
2 libsystem_kernel.dylib 0x7ff811bc3b64 mach_msg_overwrite + 586
3 libsystem_kernel.dylib 0x7ff811bbce54 mach_msg + 19
4 CoreFoundation 0x7ff811cbc2bf __CFRunLoopServiceMachPort + 145
5 CoreFoundation 0x7ff811cbad58 __CFRunLoopRun + 1354
6 CoreFoundation 0x7ff811d828b7 _CFRunLoopRunSpecificWithOptions + 496
7 AppKit 0x7ff815c7e6a0 _NSEventThread + 158
8 libsystem_pthread.dylib 0x7ff811c00d49 _pthread_start + 115
9 libsystem_pthread.dylib 0x7ff811bfc82f thread_start + 15
...