Timestamp counter heap always returns zero

Hi, I am trying to use a timestamp counter heap, but it always seems to report timestamp zero. Consider this example program:

#include <Metal/Metal.h>
#include <assert.h>

int main(int argc, char *argv[]) {
    auto device = MTLCreateSystemDefaultDevice();
    assert(device);

    auto descriptor = [MTL4CounterHeapDescriptor new];
    [descriptor setType:MTL4CounterHeapTypeTimestamp];
    [descriptor setCount:1];
    auto heap = [device newCounterHeapWithDescriptor:descriptor error:nullptr];
    assert(heap);

    [heap invalidateCounterRange:NSMakeRange(0, 1)];

    auto command_buffer = [device newCommandBuffer];
    assert(command_buffer);

    auto allocator = [device newCommandAllocator];
    assert(allocator);

    [command_buffer beginCommandBufferWithAllocator:allocator];

    auto encoder = [command_buffer computeCommandEncoder];
    assert(encoder);

    [encoder writeTimestampWithGranularity:MTL4TimestampGranularityPrecise intoHeap:heap atIndex:0];
    [encoder endEncoding];

    [command_buffer endCommandBuffer];

    auto queue = [device newMTL4CommandQueue];
    assert(queue);

    auto event = [device newSharedEvent];
    assert(event);

    [queue commit:&command_buffer count:1];
    [queue signalEvent:event value:1];

    [event waitUntilSignaledValue:1 timeoutMS:UINT64_MAX];

    auto data = [heap resolveCounterRange:NSMakeRange(0, 1)];
    printf("size %lu: %llu\n", data.length, *(uint64_t*)data.bytes);

    return 0;
}

Trying to compile and run:

% clang++ -g -O0 -o test test.mm -framework Metal -framework Foundation && MTL_DEBUG_LAYER=1 ./test
2026-06-23 14:44:48.006 test[26472:1588857] Metal API Validation Enabled
size 8: 0

I would have expected to receive

size 8: [some random non-zero number]

that number being a GPU timestamp of when the command was executed, but I always get zero. Does anybody have an idea of what I am doing wrong?