diff --git a/src/dawn/native/vulkan/TextureVk.cpp b/src/dawn/native/vulkan/TextureVk.cpp
index a2ae53cc41..7943082943 100644
--- a/src/dawn/native/vulkan/TextureVk.cpp
+++ b/src/dawn/native/vulkan/TextureVk.cpp
@@ -32,6 +32,7 @@
 
 #include "dawn/common/Assert.h"
 #include "dawn/common/DynamicLib.h"
+#include "dawn/common/Log.h"
 #include "dawn/common/Math.h"
 #include "dawn/native/ChainUtils.h"
 #include "dawn/native/DynamicUploader.h"
@@ -713,6 +714,21 @@ VkImageLayout VulkanImageLayout(const Format& format, wgpu::TextureUsage usage)
         } else if (IsSubset(kDepthWritableStencilReadOnlyAttachment, usage)) {
             return VK_IMAGE_LAYOUT_DEPTH_ATTACHMENT_STENCIL_READ_ONLY_OPTIMAL;
         } else {
+            // POC instrumentation: this branch unconditionally returns a
+            // depth/stencil layout. If we get here for a *color* format, the
+            // multi-bit usage was not one of the expected depth/stencil
+            // combinations (e.g. TextureBinding | kReadOnlyStorageTexture).
+            // In release builds the DAWN_ASSERT below is just
+            // __builtin_assume(), so log + hard-CHECK to make it observable.
+            if (!format.HasDepthOrStencil()) {
+                dawn::ErrorLog()
+                    << "POC-HIT VulkanImageLayout: returning "
+                       "VK_IMAGE_LAYOUT_DEPTH_STENCIL_READ_ONLY_OPTIMAL for "
+                       "color format, usage=0x"
+                    << std::hex
+                    << static_cast<uint64_t>(usage);
+            }
+            DAWN_CHECK(format.HasDepthOrStencil());
             DAWN_ASSERT(
                 IsSubset(usage, kReadOnlyRenderAttachment | wgpu::TextureUsage::TextureBinding));
             return VK_IMAGE_LAYOUT_DEPTH_STENCIL_READ_ONLY_OPTIMAL;