diff --git a/settings/shell.nix b/settings/shell.nix
index b62b1b2..4c576c9 100644
--- a/settings/shell.nix
+++ b/settings/shell.nix
@@ -165,7 +165,9 @@ in
       # abort the function before the emptiness check below. -L is required —
       # /sys/class/drm/cardN is a symlink, so a plain find never descends into
       # it and silently reports no GPUs at all.
-      set -l cards (find -L /sys/class/drm -maxdepth 3 -name gpu_busy_percent 2>/dev/null | sort)
+      # cardN only — renderDN is the same physical device under a second name
+      # and would otherwise be reported twice.
+      set -l cards (find -L /sys/class/drm -maxdepth 3 -name gpu_busy_percent 2>/dev/null | grep -E '/card[0-9]+/' | sort)
       if test (count $cards) -eq 0
         echo "no gpu_busy_percent found (amdgpu/i915 only — nvidia doesn't expose it)"
         return 1