diff --git a/nix/templates/weston-vnc.nix b/nix/templates/weston-vnc.nix
index 5dc5336..7cd6068 100644
--- a/nix/templates/weston-vnc.nix
+++ b/nix/templates/weston-vnc.nix
@@ -128,8 +128,15 @@
           #
           # --disable-transport-layer-security prevents the VeNCrypt TLS
           # wrapper; plain auth types (incl. type 30) are advertised directly.
+          # [core] idle-time=0 disables weston's idle timeout (default
+          # 300s). Without it the VNC desktop fades to black after 5 min
+          # idle and desktop-shell shows its click-to-unlock lock screen
+          # — useless for an agent desktop viewed over /screen (issue
+          # #180). idle-time=0 → the idle timer is updated with a 0ms
+          # delay, which wl_event_source_timer_update treats as "disarm",
+          # so the compositor never goes idle and never locks.
           WESTON_INI=$(${pkgs.coreutils}/bin/mktemp /tmp/weston-XXXXXX.ini)
-          ${pkgs.coreutils}/bin/printf '[vnc]\nauth-method=none\n' > "$WESTON_INI"
+          ${pkgs.coreutils}/bin/printf '[core]\nidle-time=0\n\n[vnc]\nauth-method=none\n' > "$WESTON_INI"
 
           exec ${pkgs.weston}/bin/weston \
             --config="$WESTON_INI" \