diff --git a/nix/modules/hive-c0re.nix b/nix/modules/hive-c0re.nix
index d13df487..0a8ef205 100644
--- a/nix/modules/hive-c0re.nix
+++ b/nix/modules/hive-c0re.nix
@@ -544,6 +544,15 @@ in
     systemd.services.hive-c0re = {
       description = "hyperhive coordinator daemon";
       wantedBy = [ "multi-user.target" ];
+      # Socket unit must start before the service so hive-c0re receives the
+      # pre-bound fd via LISTEN_FDS (socket activation). Without this
+      # dependency, nixos-rebuild switch activates hive-c0re.socket while
+      # hive-c0re.service is already running (started by multi-user.target),
+      # and systemd refuses with "Socket service already active". Adding
+      # requires+after causes systemd to stop the service, start the socket,
+      # then restart the service -- clean transition on every config apply.
+      requires = [ "hive-c0re.socket" ];
+      after = [ "hive-c0re.socket" ];
       path = [
         pkgs.git
         "/run/current-system/sw"