diff --git a/nix/modules/hive-c0re.nix b/nix/modules/hive-c0re.nix
index b98f9b58..dbe4c3c4 100644
--- a/nix/modules/hive-c0re.nix
+++ b/nix/modules/hive-c0re.nix
@@ -745,9 +745,30 @@ in
         User = "root";
         PrivateTmp = true;
         ProtectHome = true;
-        # hive-priv needs to write to /etc/nixos-containers/ and
-        # /run/systemd/system/ — "strict" would block both.
-        ProtectSystem = "false";
+        # Harden the file system view: strict makes the entire hierarchy
+        # read-only by default; ReadWritePaths carves out exactly the
+        # paths hive-priv must write to at runtime.
+        #
+        # Why each entry is needed:
+        #   /etc/nixos-containers  — writes <container>.conf (bind mounts,
+        #                            network isolation, nspawn flags)
+        #   /run/hive              — fallback socket bind if LISTEN_FDS is
+        #                            absent (normal path: socket-activated)
+        #   /run/hive-agent        — chown/chmod per-agent socket directories
+        #   /run/systemd           — container@ unit drop-ins (resource limits)
+        #                            + machinectl / systemd-machined state
+        #   /var/lib/nixos-containers — container rootfs written by nixos-container
+        #   /nix                   — nix store + profile updates during
+        #                            container create/update
+        ProtectSystem = "strict";
+        ReadWritePaths = [
+          "/etc/nixos-containers"
+          "/run/hive"
+          "/run/hive-agent"
+          "/run/systemd"
+          "/var/lib/nixos-containers"
+          "/nix"
+        ];
         # Writable HOME for nix's caches (see environment.HOME above).
         StateDirectory = "hive-priv";
         # nix (run here as root for `nixos-container update --flake