diff --git a/docs/MIGRATION.md b/docs/MIGRATION.md
index b3ceb35..5d68162 100644
--- a/docs/MIGRATION.md
+++ b/docs/MIGRATION.md
@@ -210,7 +210,7 @@ and it's whichever has higher Nix priority. Fix these explicitly:
 | Graphics | `hardware.graphics.enable = true` (was `hardware.opengl`) | Probably already enabled — fine |
 | User groups | needs `video render networkmanager` | Add to your `users.users.<user>.extraGroups` |
 | `/etc/os-release` | `ID=nomarchy`, `NAME=Nomarchy` | A few third-party scripts grep `ID=nixos` — adjust them or rely on `ID_LIKE` (TBD) |
-| autoLogin | `enable = true; user = "nomarchy";` (mkDefault) | Override with `services.displayManager.autoLogin.user = "<your user>"` or disable |
+| autoLogin | `enable = false; user = "nomarchy";` (mkDefault) | Off by default — opt in with `services.displayManager.autoLogin = { enable = true; user = "<your user>"; };` if you want it |
 
 Impermanence is **off** unless you set `nomarchy.system.impermanence.enable = true`,
 and it requires a BTRFS layout with a `root-blank` snapshot. Don't enable it
diff --git a/themes/engine/sddm.nix b/themes/engine/sddm.nix
index 6e0e851..eb57ce7 100644
--- a/themes/engine/sddm.nix
+++ b/themes/engine/sddm.nix
@@ -27,8 +27,12 @@ in
 
   services.displayManager.defaultSession = lib.mkDefault "hyprland-uwsm";
 
+  # autoLogin defaults off so hand-migrated configs (no installer-written
+  # username) don't try to log in as a nonexistent "nomarchy" user. The
+  # installer-generated system.nix sets both `enable = true;` and
+  # `user = "$USERNAME";` at normal priority, overriding these defaults.
   services.displayManager.autoLogin = {
-    enable = lib.mkDefault true;
+    enable = lib.mkDefault false;
     user = lib.mkDefault "nomarchy";
   };