diff --git a/configs/nixos/AGENTS.md b/configs/nixos/AGENTS.md
index 198aa9b..30c58f5 100644
--- a/configs/nixos/AGENTS.md
+++ b/configs/nixos/AGENTS.md
@@ -40,6 +40,8 @@
 
 ## Gotchas
 
+- `configs/nixos/registry/stable-uid.nix` receives library functions through `lib`.
+  Qualify its library calls with `lib.`.
 - Guest modules are host-agnostic wiring, while host files own deployment-specific service configuration such as served volumes and host paths.
   For example, `guests/copyparty.nix` should expose options and translate them into guest mounts/service settings, while `hosts/pikachu/default.nix` chooses `/inbox`, `/media`, and their backing paths.
   Guest addresses and routes are host-level configuration because a guest module can be used on multiple hosts.
diff --git a/configs/nixos/registry/stable-uid.nix b/configs/nixos/registry/stable-uid.nix
index c67a6d8..9849533 100644
--- a/configs/nixos/registry/stable-uid.nix
+++ b/configs/nixos/registry/stable-uid.nix
@@ -2,12 +2,12 @@
 let
   duplicateUids =
     entries:
-    filterAttrs (_uid: serviceNames: builtins.length serviceNames > 1) (serviceNamesByUid entries);
+    lib.filterAttrs (_uid: serviceNames: builtins.length serviceNames > 1) (serviceNamesByUid entries);
 
   serviceNamesByUid =
     entries:
-    mapAttrs (_uid: uidEntries: unique (map (entry: entry.entry) uidEntries)) (
-      groupBy (entry: toString entry.value) entries
+    lib.mapAttrs (_uid: uidEntries: lib.unique (map (entry: entry.entry) uidEntries)) (
+      lib.groupBy (entry: toString entry.value) entries
     );
 
 in