diff --git a/nix/modules/hive-c0re.nix b/nix/modules/hive-c0re.nix
index 9ff67e4c..be2a4574 100644
--- a/nix/modules/hive-c0re.nix
+++ b/nix/modules/hive-c0re.nix
@@ -346,6 +346,12 @@ in
         "/run/current-system/sw"
       ];
       environment = {
+        # nix (the prebuild `nix build`, flake-check, and meta eval) writes
+        # its fetcher/eval cache under $HOME/.cache. As a system user
+        # hive-core has no home, so HOME defaults to the unwritable
+        # /var/empty and Lix fails to initialise its cache. Point HOME at
+        # the writable StateDirectory.
+        HOME = "/var/lib/hyperhive";
         HYPERHIVE_GIT = "${pkgs.git}/bin/git";
         # Path to the dashboard static dist. The hive-c0re axum router
         # serves this via `tower_http::ServeDir` for any path it doesn't
@@ -423,15 +429,26 @@ in
       };
       serviceConfig = {
         ExecStart = "${cfg.package}/bin/hive-c0re --socket /run/hyperhive/host.sock serve --hyperhive-flake ${cfg.hyperhiveFlake} --nixpkgs-flake ${cfg.nixpkgsFlake} --nixpkgs-unstable-flake ${cfg.nixpkgsUnstableFlake} --dashboard-port ${toString cfg.dashboardPort} --operator-pronouns ${lib.escapeShellArg cfg.operatorPronouns} --context-window-tokens ${lib.escapeShellArg (builtins.toJSON cfg.contextWindowTokens)}";
-        # One-time migration: chown existing state tree to the service
-        # user after upgrading from a root-run install. The `+` prefix
-        # runs this step as root even though User = hive-core; the `-`
-        # prefix tolerates failure (e.g. an empty tree) without blocking
-        # startup. coreutils ships `chown` but no `sh`, so invoke chown
-        # directly rather than through a shell. systemd's StateDirectory
-        # chowns the top-level dir at every start, but pre-existing files
-        # inside may still be root-owned.
-        ExecStartPre = "+-${pkgs.coreutils}/bin/chown -R hive-core:hive-core /var/lib/hyperhive";
+        # Migrate hive-c0re's *own* state to the service user after an
+        # upgrade from a root-run install (systemd's StateDirectory only
+        # chowns the top-level dir, not pre-existing files inside it). The
+        # `+` prefix runs as root despite User = hive-core; `-` tolerates
+        # failure. coreutils ships `chown` but no `sh`, so invoke the
+        # binaries directly rather than through a shell.
+        #
+        # CRITICAL: exclude the per-agent `agents/` subtree. Its contents
+        # (each agent's `claude/` OAuth creds, `state/`, `harness/`,
+        # `config/`) are owned by the per-agent / manager users, and each
+        # container's `hive-agent-user-migrate` activation script chowns
+        # them back to that user on boot. Blanket-chowning them to hive-core
+        # makes every agent's `~/.claude` unreadable — logging them all out
+        # with no way to log back in. So chown everything *except* agents/,
+        # plus the `agents/` dir node itself (not its contents) so c0re can
+        # still create new per-agent subdirs.
+        ExecStartPre = [
+          "+-${pkgs.findutils}/bin/find /var/lib/hyperhive -mindepth 1 -maxdepth 1 -not -name agents -exec ${pkgs.coreutils}/bin/chown -R hive-core:hive-core {} +"
+          "+-${pkgs.coreutils}/bin/chown hive-core:hive-core /var/lib/hyperhive/agents"
+        ];
         Restart = "on-failure";
         RestartSec = 2;
         User = "hive-core";
@@ -521,6 +538,14 @@ in
         pkgs.util-linux # umount (nsenter is hardcoded in the script)
         pkgs.e2fsprogs # chattr
       ];
+      environment = {
+        # `nixos-container update/create` runs `nix`, which writes its
+        # fetcher/eval cache under $HOME/.cache. With ProtectHome and no
+        # explicit HOME this lands on the unwritable /var/empty and Lix
+        # errors out. Point HOME at the StateDirectory below (persistent,
+        # so the cache survives across rebuilds).
+        HOME = "/var/lib/hive-priv";
+      };
       serviceConfig = {
         ExecStart = "${cfg.package}/bin/hive-priv";
         Type = "simple";
@@ -530,6 +555,8 @@ in
         # hive-priv needs to write to /etc/nixos-containers/ and
         # /run/systemd/system/ — "strict" would block both.
         ProtectSystem = "false";
+        # Writable HOME for nix's caches (see environment.HOME above).
+        StateDirectory = "hive-priv";
       };
     };
   };