diff --git a/MobileGL/MG_Impl/EGLImpl/EGLImpl.cpp b/MobileGL/MG_Impl/EGLImpl/EGLImpl.cpp
index 16a62203..da6b938e 100644
--- a/MobileGL/MG_Impl/EGLImpl/EGLImpl.cpp
+++ b/MobileGL/MG_Impl/EGLImpl/EGLImpl.cpp
@@ -7,6 +7,7 @@
 // End of Source File Header
 
 #include "EGLImpl.h"
+#include "EGLPlatformExtensions.h"
 #include "../GetProcAddress.h"
 #include <Init.h>
 #include <MG_Backend/BackendObjects.h>
@@ -463,14 +464,10 @@ namespace MobileGL::MG_Impl::EGLImpl {
         case EGL_CLIENT_APIS:
             return "OpenGL OpenGL_ES";
         case EGL_EXTENSIONS:
-            if (display == EGL_NO_DISPLAY) {
-                return "EGL_EXT_client_extensions "
-                       "EGL_EXT_platform_base "
-                       "EGL_KHR_platform_base "
-                       "EGL_MESA_platform_surfaceless";
-            }
-            return "EGL_KHR_create_context "
-                   "EGL_MESA_platform_surfaceless";
+            // One list, in EGLPlatformExtensions.h, because the vendor string glvnd reads and
+            // this query an application reads have to agree: an application that does not see the
+            // platform extension here never asks for a platform display at all.
+            return display == EGL_NO_DISPLAY ? kClientExtensionString : kDisplayExtensionString;
         default:
             state->SetError(EGL_BAD_PARAMETER);
             return nullptr;
diff --git a/MobileGL/MG_Impl/EGLImpl/EGLPlatformExtensions.h b/MobileGL/MG_Impl/EGLImpl/EGLPlatformExtensions.h
new file mode 100644
index 00000000..d60b640a
--- /dev/null
+++ b/MobileGL/MG_Impl/EGLImpl/EGLPlatformExtensions.h
@@ -0,0 +1,75 @@
+// MobileGL - MobileGL/MG_Impl/EGLImpl/EGLPlatformExtensions.h
+// Copyright (c) 2025-2026 MobileGL-Dev
+// Licensed under the GNU Lesser General Public License v3.0:
+//   https://www.gnu.org/licenses/gpl-3.0.txt
+//   https://www.gnu.org/licenses/lgpl-3.0.txt
+// SPDX-License-Identifier: LGPL-3.0-only
+// End of Source File Header
+
+#pragma once
+
+namespace MobileGL::MG_Impl::EGLImpl {
+    // THE PLATFORMS THIS IMPLEMENTATION SERVES, in the words EGL spells them.
+    //
+    // Two callers need exactly the same list, and they disagree if it is written twice:
+    // eglQueryString(EGL_EXTENSIONS) is what an application reads BEFORE it decides to call
+    // eglGetPlatformDisplay at all - libepoxy refuses to use eglGetPlatformDisplayEXT unless the
+    // string names EGL_EXT_platform_base - and the glvnd vendor string is what the system's
+    // libEGL reads to decide which vendor library a platform request should be routed to.  A
+    // vendor that does not claim the platform is never asked for it, and the caller is told there
+    // is no provider: the library can be loaded, initialized, and still never called.
+    //
+    // GBM is on the list because a compositor asks for its display on the GBM device it owns.
+    // This side treats that device the way it treats every other native display - the frames come
+    // from the display host, not from the device - so the claim is exact rather than optimistic.
+    inline constexpr const char* kDeviceExtensionString =
+        "EGL_EXT_device_base "
+        "EGL_EXT_device_enumeration "
+        "EGL_EXT_device_query "
+        "EGL_EXT_device_drm "
+        "EGL_EXT_device_drm_render_node";
+
+    inline constexpr const char* kPlatformExtensionString =
+        "EGL_EXT_platform_base "
+        "EGL_KHR_platform_base "
+        "EGL_KHR_platform_gbm "
+        "EGL_EXT_platform_gbm "
+        "EGL_MESA_platform_gbm "
+        "EGL_EXT_platform_device "
+        "EGL_MESA_platform_surfaceless";
+
+    // What a display answers for EGL_EXTENSIONS: the extensions this implementation provides that
+    // are not platform ones, then the platform list above.
+    inline constexpr const char* kDisplayExtensionString =
+        "EGL_KHR_create_context "
+        "EGL_EXT_device_base "
+        "EGL_EXT_device_enumeration "
+        "EGL_EXT_device_query "
+        "EGL_EXT_device_drm "
+        "EGL_EXT_device_drm_render_node "
+        "EGL_EXT_platform_device "
+        "EGL_EXT_platform_base "
+        "EGL_KHR_platform_base "
+        "EGL_KHR_platform_gbm "
+        "EGL_EXT_platform_gbm "
+        "EGL_MESA_platform_gbm "
+        "EGL_MESA_platform_surfaceless";
+
+    // ... and what EGL_NO_DISPLAY answers: the same, plus the client-extension marker that tells a
+    // caller the no-display query is meaningful here.
+    inline constexpr const char* kClientExtensionString =
+        "EGL_EXT_client_extensions "
+        "EGL_KHR_create_context "
+        "EGL_EXT_device_base "
+        "EGL_EXT_device_enumeration "
+        "EGL_EXT_device_query "
+        "EGL_EXT_device_drm "
+        "EGL_EXT_device_drm_render_node "
+        "EGL_EXT_platform_device "
+        "EGL_EXT_platform_base "
+        "EGL_KHR_platform_base "
+        "EGL_KHR_platform_gbm "
+        "EGL_EXT_platform_gbm "
+        "EGL_MESA_platform_gbm "
+        "EGL_MESA_platform_surfaceless";
+}