diff --git a/nix/templates/agent-base.nix b/nix/templates/agent-base.nix
index 17262a7..4683023 100644
--- a/nix/templates/agent-base.nix
+++ b/nix/templates/agent-base.nix
@@ -7,9 +7,12 @@
   environment.systemPackages = with pkgs; [
     hyperhive
     claude-code
+    bashInteractive
     git
     coreutils-full
   ];
+  # claude's Bash tool refuses to run without a POSIX shell + $SHELL set.
+  environment.variables.SHELL = "${pkgs.bashInteractive}/bin/bash";
 
   systemd.services.hive-ag3nt = {
     description = "hive-ag3nt harness";
@@ -18,7 +21,12 @@
     # The harness shells out to `claude` (turn loop + login flow). systemd
     # units get a minimal PATH by default, so we have to put claude-code on
     # it explicitly even though it's in environment.systemPackages above.
-    path = [ pkgs.claude-code ];
+    # bash is on PATH so claude's Bash tool can spawn `$SHELL`.
+    path = [
+      pkgs.claude-code
+      pkgs.bashInteractive
+    ];
+    environment.SHELL = "${pkgs.bashInteractive}/bin/bash";
     serviceConfig = {
       ExecStart = "${pkgs.hyperhive}/bin/hive-ag3nt serve";
       Restart = "on-failure";
diff --git a/nix/templates/manager.nix b/nix/templates/manager.nix
index 13ad191..0859e0b 100644
--- a/nix/templates/manager.nix
+++ b/nix/templates/manager.nix
@@ -7,9 +7,12 @@
   environment.systemPackages = with pkgs; [
     hyperhive
     claude-code
+    bashInteractive
     git
     coreutils-full
   ];
+  # claude's Bash tool refuses to run without a POSIX shell + $SHELL set.
+  environment.variables.SHELL = "${pkgs.bashInteractive}/bin/bash";
 
   environment.etc."gitconfig".text = ''
     [user]
@@ -27,9 +30,13 @@
       HIVE_PORT = "8000";
       HIVE_LABEL = "hm1nd";
     };
-    # See note in agent-base.nix — `claude` has to be on the service PATH
-    # explicitly for the harness to shell out to it.
-    path = [ pkgs.claude-code ];
+    # See note in agent-base.nix — `claude` and a POSIX shell have to be on
+    # the service PATH explicitly for the harness + claude's Bash tool.
+    path = [
+      pkgs.claude-code
+      pkgs.bashInteractive
+    ];
+    environment.SHELL = "${pkgs.bashInteractive}/bin/bash";
     serviceConfig = {
       ExecStart = "${pkgs.hyperhive}/bin/hive-m1nd serve";
       Restart = "on-failure";