This crash is seemingly random, I can usually reproduce it by pressing Super+Space, and launching an app - then restarting the Assistant, and typing some random characters - it seems to be completely random.

106.877 Assistant(64:64): Started Thread "Background Thread"(65)
107.647 Assistant(64:65): Built cache in 763 ms
107.655 Assistant(64:64): ASSERTION FAILED: false
././AK/Function.h:208
107.655 [#0 Assistant(64:64)]: Terminating Assistant(64) due to signal 6
107.655 [#0 Finalizer Task(5:5)]: Backtrace:
0x00000000deadc0de  Kernel::Processor::switch_context(Kernel::Thread*&, Kernel::Thread*&) + 0x383
107.655 [#0 Finalizer Task(5:5)]: Backtrace:
0x00000000deadc0de  Kernel::Processor::switch_context(Kernel::Thread*&, Kernel::Thread*&) + 0x383
107.655 [#0 Finalizer Task(5:5)]: Generating coredump for pid: 64
107.663 CrashDaemon(34:34): New coredump file: /tmp/coredump/Assistant_64_1679253479
107.862 CrashReporter(66:66): Started Thread "Background Thread"(67)
108.810 CrashReporter(66:67): Generating backtrace took 949 ms
108.810 CrashReporter(66:67): --- Backtrace for thread #0 (TID 64) ---
108.810 CrashReporter(66:67): 0x000000105223202b: [/usr/lib/libsystem.so] syscall2 +0xb (syscall.cpp:25 => syscall.cpp:24)
108.810 CrashReporter(66:67): 0x0000000c7689448d: [/usr/lib/libc.so] abort +0x26 (stdlib.cpp:386)
108.810 CrashReporter(66:67): 0x0000000c7689a855: [/usr/lib/libc.so] __assertion_failed +0x85 (assert.cpp:34)
108.814 CrashReporter(66:67): 0x0000001b83f9142f: [/bin/Assistant] AK::Function<void ()>::CallableWrapper<Threading::BackgroundAction<AK::Optional<AK::Vector<AK::NonnullRefPtr<Assistant::Result>, 0ul> > >::BackgroundAction(AK::Function<AK::ErrorOr<AK::Optional<AK::Vector<AK::NonnullRefPtr<Assistant::Result>, 0ul> >, AK::Error> (Threading::BackgroundAction<AK::Optional<AK::Vector<AK::NonnullRefPtr<Assistant::Result>, 0ul> > >&)>, AK::Function<AK::ErrorOr<void, AK::Error> (AK::Optional<AK::Vector<AK::NonnullRefPtr<Assistant::Result>, 0ul> >)>, AK::Optional<AK::Function<void (AK::Error)> >)::{lambda()#2}::operator()() const::{lambda()#2}>::call() +0x3f (Function.h:208 => Function.h:104)
108.814 CrashReporter(66:67): 0x0000000dcbcfe678: [/usr/lib/libcore.so.serenity] Core::EventLoop::pump(Core::EventLoop::WaitMode) [clone .localalias] +0x488 (Function.h:111)
108.814 CrashReporter(66:67): 0x0000000dcbcfebb9: [/usr/lib/libcore.so.serenity] Core::EventLoop::exec() +0x99 (EventLoop.cpp:451)
108.818 CrashReporter(66:67): 0x0000001b83f94bb9: [/bin/Assistant] serenity_main(Main::Arguments) +0xc09 (main.cpp:285)
108.818 CrashReporter(66:67): 0x0000001b83f84b5a: [/bin/Assistant] main +0x14a (Main.cpp:43)
108.818 CrashReporter(66:67): 0x0000001b83f84ce8: [/bin/Assistant] _entry +0x48 (crt0.cpp:48)
109.064 CrashReporter(66:67): Generating backtrace took 227 ms
109.064 CrashReporter(66:67): --- Backtrace for thread #1 (TID 65) ---
109.064 CrashReporter(66:67): 0x0000001052232043: [/usr/lib/libsystem.so] syscall3 +0x13 (syscall.cpp:30 => syscall.cpp:29)
109.064 CrashReporter(66:67): 0x0000000c768cbbab: [/usr/lib/libc.so] madvise +0x1b (syscall.h:40 => mman.cpp:77)
109.068 CrashReporter(66:67): 0x0000000c7689f53d: [/usr/lib/libc.so] malloc_impl +0x57d (malloc.cpp:337)
109.068 CrashReporter(66:67): 0x0000000c7689f9ac: [/usr/lib/libc.so] malloc +0x3c (malloc.cpp:543)
109.068 CrashReporter(66:67): 0x0000001b83f8fe00: [/bin/Assistant] AK::Vector<AK::NonnullRefPtr<Assistant::Result>, 0ul>::try_ensure_capacity(unsigned long) +0x40 (kmalloc.h:47 => Vector.h:649)
109.068 CrashReporter(66:67): 0x0000001b83f88e48: [/bin/Assistant] AK::Optional<AK::Vector<AK::NonnullRefPtr<Assistant::Result>, 0ul> > Assistant::FileProvider::query(AK::DeprecatedString const&, AK::Function<void (AK::Vector<AK::NonnullRefPtr<Assistant::Result>, 0ul>)>)::{lambda(auto:1&)#1}::operator()<Threading::BackgroundAction<AK::Optional<AK::Vector<AK::NonnullRefPtr<Assistant::Result>, 0ul> > > >(Threading::BackgroundAction<AK::Optional<AK::Vector<AK::NonnullRefPtr<Assistant::Result>, 0ul> > >&) const +0x1d8 (Vector.h:641 => Vector.h:560 => Vector.h:262 => Providers.cpp:147)
109.072 CrashReporter(66:67): 0x0000001b83f900b8: [/bin/Assistant] Threading::BackgroundAction<AK::Optional<AK::Vector<AK::NonnullRefPtr<Assistant::Result>, 0ul> > >::BackgroundAction(AK::Function<AK::ErrorOr<AK::Optional<AK::Vector<AK::NonnullRefPtr<Assistant::Result>, 0ul> >, AK::Error> (Threading::BackgroundAction<AK::Optional<AK::Vector<AK::NonnullRefPtr<Assistant::Result>, 0ul> > >&)>, AK::Function<AK::ErrorOr<void, AK::Error> (AK::Optional<AK::Vector<AK::NonnullRefPtr<Assistant::Result>, 0ul> >)>, AK::Optional<AK::Function<void (AK::Error)> >)::{lambda()#2}::operator()() const +0x98 (Function.h:173 => Function.h:111)
109.072 CrashReporter(66:67): 0x0000001cd302caaa: [/usr/lib/libthreading.so.serenity] background_thread_func() +0x58a (Function.h:111)
109.072 CrashReporter(66:67): 0x0000001cd302d77c: [/usr/lib/libthreading.so.serenity] Threading::Thread::start()::{lambda(void*)#1}::_FUN(void*) +0x6c (Function.h:111)
109.076 CrashReporter(66:67): 0x0000000c768a9fbb: [/usr/lib/libc.so] pthread_create_helper +0x2b (pthread.cpp:73)

Crash is related to:

It smells like a race condition to me, but I'm unfamiliar with how Assistant works.