diff --git a/AGENTS.md b/AGENTS.md
new file mode 100644
index 00000000..8aa9e002
--- /dev/null
+++ b/AGENTS.md
@@ -0,0 +1,9 @@
+Use idiomatic nix.
+
+Before making changes, read the appropriate entries of the following manuals:
+- man configuration.nix
+- man home-configuration.nix
+
+Do not read the entire manual at once, instead search only for what you need.
+
+After editing nix configurations, always run  `nix flake check nixos/` to check for errors.
diff --git a/nixos/configuration.nix b/nixos/configuration.nix
index 76b0c3c4..c15a3b5c 100644
--- a/nixos/configuration.nix
+++ b/nixos/configuration.nix
@@ -76,6 +76,7 @@
   };
 
   home-manager = {
+    backupFileExtension = "~";
     extraSpecialArgs = { inherit inputs; };
     users = {
       "trude" = import ./home.nix;
diff --git a/nixos/home.nix b/nixos/home.nix
index 74830cda..1342b25f 100644
--- a/nixos/home.nix
+++ b/nixos/home.nix
@@ -79,7 +79,7 @@
 
   home.sessionVariables = {
     EDITOR = "gnome-text-editor";
-    SSH_AUTH_SOCK = "$XDG_RUNTIME_DIR/ssh-agent";
+    SSH_AUTH_SOCK = "$XDG_RUNTIME_DIR/gcr/.ssh";
   };
 
   programs.git = {
@@ -107,7 +107,7 @@
       };
     };
   };
-
+  
   programs.bash = {
     enable = true;
     shellAliases = {