diff --git a/third_party/dawn/src/dawn/native/Sampler.cpp b/third_party/dawn/src/dawn/native/Sampler.cpp
index e9509e47722..744a361fe61 100644
--- a/third_party/dawn/src/dawn/native/Sampler.cpp
+++ b/third_party/dawn/src/dawn/native/Sampler.cpp
@@ -77,6 +77,16 @@ MaybeError ValidateSamplerDescriptor(DeviceBase* device, const SamplerDescriptor
 
         DAWN_INVALID_IF(ycbcr->externalFormat == 0 && ycbcr->vkFormat == 0,
                         "Both VkFormat and VkExternalFormatANDROID are undefined.");
+
+        // VUID-VkSamplerCreateInfo-addressModeU-01646: when a YCbCr conversion
+        // is attached, addressModeU/V/W must be CLAMP_TO_EDGE. Reject anything
+        // else here so renderer-supplied tile modes cannot drive vkCreateSampler
+        // into spec-undefined behaviour in the GPU process.
+        DAWN_INVALID_IF(descriptor->addressModeU != wgpu::AddressMode::ClampToEdge ||
+                            descriptor->addressModeV != wgpu::AddressMode::ClampToEdge ||
+                            descriptor->addressModeW != wgpu::AddressMode::ClampToEdge,
+                        "addressModeU/V/W must be ClampToEdge when a YCbCrVkDescriptor "
+                        "is chained (VUID-VkSamplerCreateInfo-addressModeU-01646).");
     }
 
     return {};
diff --git a/third_party/dawn/src/dawn/native/vulkan/SamplerVk.cpp b/third_party/dawn/src/dawn/native/vulkan/SamplerVk.cpp
index 11a97d4e56c..eb1c29cc686 100644
--- a/third_party/dawn/src/dawn/native/vulkan/SamplerVk.cpp
+++ b/third_party/dawn/src/dawn/native/vulkan/SamplerVk.cpp
@@ -143,6 +143,16 @@ MaybeError Sampler::Initialize(const SamplerDescriptor* descriptor) {
         samplerYCbCrInfo.pNext = nullptr;
         samplerYCbCrInfo.conversion = mSamplerYCbCrConversion;
 
+        // VUID-VkSamplerCreateInfo-addressModeU-01646 requires CLAMP_TO_EDGE on
+        // every axis when a YCbCr conversion is enabled. This mirrors the
+        // safeguard Ganesh applies (skia/src/gpu/ganesh/vk/GrVkSampler.cpp) and
+        // is a backstop for callers that reach here with validation skipped
+        // (e.g. StaticSamplerSpecialization::Create above).
+        createInfo.addressModeU = VK_SAMPLER_ADDRESS_MODE_CLAMP_TO_EDGE;
+        createInfo.addressModeV = VK_SAMPLER_ADDRESS_MODE_CLAMP_TO_EDGE;
+        createInfo.addressModeW = VK_SAMPLER_ADDRESS_MODE_CLAMP_TO_EDGE;
+        createInfo.anisotropyEnable = VK_FALSE;
+        createInfo.unnormalizedCoordinates = VK_FALSE;
         createInfo.pNext = &samplerYCbCrInfo;
     }
 
diff --git a/third_party/skia/src/gpu/graphite/dawn/DawnSampler.cpp b/third_party/skia/src/gpu/graphite/dawn/DawnSampler.cpp
index 19b8f0a0ae6..1e954ee2695 100644
--- a/third_party/skia/src/gpu/graphite/dawn/DawnSampler.cpp
+++ b/third_party/skia/src/gpu/graphite/dawn/DawnSampler.cpp
@@ -93,6 +93,12 @@ sk_sp<DawnSampler> DawnSampler::Make(const DawnSharedContext* sharedContext,
     if (samplerDesc.isImmutable()) {
         ycbcrDescriptor =
                 DawnDescriptorFromImmutableSamplerInfo(samplerDesc.immutableSamplerInfo());
+        // Required values when using a YCbCr conversion
+        // (VUID-VkSamplerCreateInfo-addressModeU-01646). Matches the override
+        // applied by Ganesh's GrVkSampler::Create.
+        desc.addressModeU = wgpu::AddressMode::ClampToEdge;
+        desc.addressModeV = wgpu::AddressMode::ClampToEdge;
+        desc.addressModeW = wgpu::AddressMode::ClampToEdge;
         desc.nextInChain = &ycbcrDescriptor;
     }
 #endif