diff --git a/src/libANGLE/renderer/vulkan/ContextVk.cpp b/src/libANGLE/renderer/vulkan/ContextVk.cpp
index 5adcdf29eb..464e1cc051 100644
--- a/src/libANGLE/renderer/vulkan/ContextVk.cpp
+++ b/src/libANGLE/renderer/vulkan/ContextVk.cpp
@@ -2764,6 +2764,33 @@ angle::Result ContextVk::handleDirtyGraphicsIndexBuffer(DirtyBits::Iterator *dir
     vk::BufferHelper *elementArrayBuffer = mCurrentIndexBuffer;
     ASSERT(elementArrayBuffer != nullptr);
 
+    // ---- POC instrumentation: detect stale offset on converted index buffer ----
+    {
+        const VkDeviceSize bufSize     = elementArrayBuffer->getSize();
+        const VkDeviceSize offset      = mCurrentIndexBufferOffset;
+        const VkDeviceSize suballocOff = elementArrayBuffer->getOffset();
+        if (offset > bufSize)
+        {
+            const VkDeviceSize underflow = bufSize - offset;  // wraps on VkDeviceSize/uint64
+            fprintf(
+                stderr,
+                "[ANGLE-POC] *** BUG *** handleDirtyGraphicsIndexBuffer: "
+                "mCurrentIndexBufferOffset=%llu > mCurrentIndexBuffer->getSize()=%llu "
+                "(suballoc offset=%llu, supportsMaintenance5=%d, supportsIndexTypeUint8=%d)\n"
+                "[ANGLE-POC]   -> maintenance5 path: vkCmdBindIndexBuffer2KHR size = "
+                "roundDownPow2(size-offset,..) = roundDownPow2(%llu,..) ~= 2^64 "
+                "(VUID-vkCmdBindIndexBuffer2-size-08767)\n"
+                "[ANGLE-POC]   -> non-maintenance5 path: vkCmdBindIndexBuffer offset = %llu "
+                "into pool VkBuffer (VUID-vkCmdBindIndexBuffer-offset-08782 / OOB index read)\n",
+                (unsigned long long)offset, (unsigned long long)bufSize,
+                (unsigned long long)suballocOff,
+                (int)getFeatures().supportsMaintenance5.enabled,
+                (int)getFeatures().supportsIndexTypeUint8.enabled,
+                (unsigned long long)underflow, (unsigned long long)(suballocOff + offset));
+        }
+    }
+    // ---- end POC instrumentation ----
+
     if (getFeatures().supportsMaintenance5.enabled)
     {
         // The bound size is from the start offset to the end of the element buffer, and should be