diff --git a/Makefile b/Makefile
index a36f2f5..46aa8be 100644
--- a/Makefile
+++ b/Makefile
@@ -37,6 +37,7 @@ update:
 	$(MAKE) gc
 
 # Nettoyage Nix (générations > 14 jours + garbage collect)
+# Même politique que nix.gc.automatic dans nixos/configuration.nix.
 gc:
 	@echo "=== Générations utilisateur ==="
 	nix-env --list-generations
@@ -51,7 +52,7 @@ gc:
 	sudo nix-env --delete-generations 14d --profile /nix/var/nix/profiles/system
 	@echo ""
 	@echo "=== Garbage collection ==="
-	sudo nix-collect-garbage
+	sudo nix-collect-garbage --delete-older-than 14d
 	@echo ""
 	@echo "=== Espace disque /nix/store ==="
 	du -sh /nix/store
diff --git a/nixos/configuration.nix b/nixos/configuration.nix
index 5d50be2..3a1ab34 100644
--- a/nixos/configuration.nix
+++ b/nixos/configuration.nix
@@ -206,15 +206,19 @@
   networking.firewall.allowedUDPPorts = [ 9003 ];
   # Or disable the firewall altogether.
   # networking.firewall.enable = false;
-  # https://github.com/nix-community/nix-direnv/
-  nix.extraOptions = ''
-    keep-outputs = true
-    keep-derivations = true
-  '';
   nix.settings.extra-experimental-features = [
     "nix-command"
     "flakes"
   ];
+  nix.settings.auto-optimise-store = true;
+
+  # Les environnements direnv sont protégés par leurs propres gcroots
+  # (nix-direnv "_nix_add_gcroot"), inutile de garder outputs/derivations.
+  nix.gc = {
+    automatic = true;
+    dates = "weekly";
+    options = "--delete-older-than 14d";
+  };
 
   # Cache binaire de https://github.com/lukasl-dev/pi.nix (cf. programs/pi.nix)
   nix.settings.extra-substituters = [ "https://pi.cachix.org" ];