diff --git a/src/libANGLE/Framebuffer.cpp b/src/libANGLE/Framebuffer.cpp
index 0672c1298a..e23c49f520 100644
--- a/src/libANGLE/Framebuffer.cpp
+++ b/src/libANGLE/Framebuffer.cpp
@@ -2519,11 +2519,46 @@ angle::Result Framebuffer::ensureClearAttachmentsInitialized(const Context *cont
     // but are explicitly masked out here for clarity.
     const DrawBufferMask colorAttachmentsNeedingInit(mState.mResourceNeedsInit.bits() &
                                                      DrawBufferMask().set().bits());
-    if (partialClearNeedsInit(context, colorAttachmentsNeedingInit, depth, stencil))
+    const bool partialNeedsInit =
+        partialClearNeedsInit(context, colorAttachmentsNeedingInit, depth, stencil);
+    if (partialNeedsInit)
     {
         ANGLE_TRY(ensureDrawAttachmentsInitialized(context));
     }
 
+    // ---- POC DETECTION HOOK (not part of upstream) ------------------------------
+    // This is a logic bug (CWE-908), not memory corruption, so ASAN will not catch
+    // it directly. This hook converts the bypass into a deterministic crash so the
+    // exploit path is observable regardless of whether the underlying GPU driver
+    // happens to zero freshly allocated VRAM.
+    //
+    // It fires when ALL of the following hold:
+    //   * The application is clearing the stencil buffer (stencil == true).
+    //   * The stencil attachment is currently uninitialized (resource-needs-init
+    //     bit is set).
+    //   * partialClearNeedsInit() returned false, so robust-resource-init will be
+    //     SKIPPED and the attachment is about to be marked Initialized below.
+    //   * The stencil writemask does NOT cover all 8 bits, so the upcoming masked
+    //     clear will leave some bits containing whatever was previously in VRAM.
+    if (stencil && !partialNeedsInit &&
+        mState.mResourceNeedsInit.test(DIRTY_BIT_STENCIL_ATTACHMENT) &&
+        ((depthStencil.stencilWritemask & 0xFF) != 0xFF ||
+         (depthStencil.stencilBackWritemask & 0xFF) != 0xFF))
+    {
+        FATAL() << "POC: robust-resource-init BYPASS reached. "
+                << "stencilWritemask=0x" << std::hex
+                << (depthStencil.stencilWritemask & 0xFF)
+                << " stencilBackWritemask=0x"
+                << (depthStencil.stencilBackWritemask & 0xFF)
+                << " stencilValueMask=0x" << (depthStencil.stencilMask & 0xFF)
+                << " stencilBackValueMask=0x"
+                << (depthStencil.stencilBackMask & 0xFF)
+                << " -- partialClearNeedsInit() returned false; uninitialized "
+                   "stencil bits 4-7 are about to be marked Initialized and "
+                   "exposed to web content.";
+    }
+    // ----------------------------------------------------------------------------
+
     // If the impl encounters an error during a a full (non-partial) clear, the attachments will
     // still be marked initialized. This simplifies design, allowing this method to be called before
     // the clear.