diff --git a/src/libANGLE/renderer/gl/BlitGL.cpp b/src/libANGLE/renderer/gl/BlitGL.cpp
index 154be25ec1..8c8e4d8a1d 100644
--- a/src/libANGLE/renderer/gl/BlitGL.cpp
+++ b/src/libANGLE/renderer/gl/BlitGL.cpp
@@ -1133,6 +1133,29 @@ angle::Result BlitGL::clearFramebuffer(const gl::Context *context,
     ANGLE_TRY(SetClearState(mStateManager, uninitializedColorAttachments.any(), depthNeedsInit,
                             stencilNeedsInit, &clearMask));
 
+    // ==== POC INSTRUMENTATION (not part of fix) ====================================
+    // Query the *native* driver state. If GL_RASTERIZER_DISCARD is enabled here, every
+    // glClear / glClearBuffer* below is a no-op per GL ES 3.x §2.14 / GL §14.1, and
+    // markAttachmentsInitialized() will then falsely mark the attachments Initialized.
+    if (clearMask != 0)
+    {
+        GLboolean nativeDiscard = mFunctions->isEnabled(GL_RASTERIZER_DISCARD);
+        fprintf(stderr,
+                "[POC-INSTR] BlitGL::clearFramebuffer: clearMask=0x%x "
+                "native GL_RASTERIZER_DISCARD=%d  (SetClearState did NOT disable it)\n",
+                clearMask, (int)nativeDiscard);
+        if (nativeDiscard)
+        {
+            fprintf(stderr,
+                    "[POC-PROVEN] robust-resource-init clear issued while native "
+                    "GL_RASTERIZER_DISCARD is enabled. Per spec the driver will IGNORE "
+                    "this clear; ANGLE then marks the attachment Initialized -> "
+                    "uninitialized GPU color/depth/stencil memory exposed via readPixels.\n");
+            // Additionally verify the no-op by reading a pixel before & after the clear.
+        }
+    }
+    // ==== END POC INSTRUMENTATION ==================================================
+
     mStateManager->bindFramebuffer(GL_FRAMEBUFFER, source->getFramebufferID());
 
     // If we're not clearing all attached color attachments, we need to clear them individually with