diff --git a/nix/modules/hive-c0re.nix b/nix/modules/hive-c0re.nix
index dbe4c3c4..4e5cb42c 100644
--- a/nix/modules/hive-c0re.nix
+++ b/nix/modules/hive-c0re.nix
@@ -771,6 +771,15 @@ in
         ];
         # Writable HOME for nix's caches (see environment.HOME above).
         StateDirectory = "hive-priv";
+        # With ProtectSystem=strict the root filesystem is read-only inside
+        # hive-priv. When `nixos-container create/update` invokes nix, nix
+        # creates a temporary result symlink in its working directory. Without
+        # an explicit WorkingDirectory the cwd is / (inherited from systemd),
+        # which is read-only under strict, causing:
+        #   error: creating symlink "/.tmp.tmp-..." -> ...: Read-only file system
+        # Point the working directory at the writable StateDirectory so nix
+        # drops its temp symlink there instead.
+        WorkingDirectory = "/var/lib/hive-priv";
         # nix (run here as root for `nixos-container update --flake
         # /var/lib/hyperhive/meta#<agent>`) fetches the hive-core-owned
         # meta/applied repos; libgit2 refuses them without safe.directory.