yarn: disable steamos-update

system/system-yarn.nix

@@ -75,6 +75,71 @@
       "steam-run"
     ];
 
+  # Override jovian-stubs to disable steamos-update kernel check
+  # This prevents Steam from requesting reboots for "system updates"
+  # Steam client updates will still work normally
+  nixpkgs.overlays = [
+    (final: prev: {
+      jovian-stubs = prev.stdenv.mkDerivation {
+        name = "jovian-stubs-no-update";
+        dontUnpack = true;
+        installPhase = ''
+          mkdir -p $out/bin
+
+          # steamos-update: always report "no update available" (exit 7)
+          # This disables the kernel mismatch check that triggers reboot prompts
+          cat > $out/bin/steamos-update << 'STUB'
+          #!/bin/sh
+          >&2 echo "[JOVIAN] $0: stub called with: $* (system updates disabled)"
+          exit 7
+          STUB
+
+          # steamos-reboot: reboot the system
+          cat > $out/bin/steamos-reboot << 'STUB'
+          #!/bin/sh
+          >&2 echo "[JOVIAN] $0: stub called with: $*"
+          systemctl reboot
+          STUB
+
+          # steamos-select-branch: no-op stub
+          cat > $out/bin/steamos-select-branch << 'STUB'
+          #!/bin/sh
+          >&2 echo "[JOVIAN] $0: stub called with: $*"
+          exit 0
+          STUB
+
+          # steamos-factory-reset-config: no-op stub
+          cat > $out/bin/steamos-factory-reset-config << 'STUB'
+          #!/bin/sh
+          >&2 echo "[JOVIAN] $0: stub called with: $*"
+          exit 0
+          STUB
+
+          # steamos-firmware-update: no-op stub
+          cat > $out/bin/steamos-firmware-update << 'STUB'
+          #!/bin/sh
+          >&2 echo "[JOVIAN] $0: stub called with: $*"
+          exit 0
+          STUB
+
+          # pkexec: pass through to real pkexec
+          cat > $out/bin/pkexec << 'STUB'
+          #!/bin/sh
+          exec /run/wrappers/bin/pkexec "$@"
+          STUB
+
+          # sudo: pass through to doas
+          cat > $out/bin/sudo << 'STUB'
+          #!/bin/sh
+          exec /run/wrappers/bin/doas "$@"
+          STUB
+
+          chmod 755 $out/bin/*
+        '';
+      };
+    })
+  ];
+
   jovian = {
     devices.steamdeck.enable = false;
     steam = {