{ pkgs, lib, config, ... }:
{
  # Shared scaffolding for any hyperhive harness container — both
  # sub-agents (`agent-base.nix`) and the manager (`manager.nix`) extend
  # this. The systemd service that actually runs the harness binary
  # differs per role and lives in the child module.

  options.hyperhive.extraMcpServers = lib.mkOption {
    type = lib.types.attrsOf (lib.types.submodule {
      options = {
        command = lib.mkOption {
          type = lib.types.str;
          description = "Absolute path to the MCP server binary. Use `\${pkgs.foo}/bin/foo` or `/run/current-system/sw/bin/foo`.";
        };
        args = lib.mkOption {
          type = lib.types.listOf lib.types.str;
          default = [ ];
          description = "Args passed to the MCP server binary.";
        };
        env = lib.mkOption {
          type = lib.types.attrsOf lib.types.str;
          default = { };
          description = "Environment variables for the MCP server child process.";
        };
        allowedTools = lib.mkOption {
          type = lib.types.listOf lib.types.str;
          default = [ "*" ];
          example = [ "send_message" "join_room" ];
          description = ''
            Tool names this MCP server is auto-approved to call via
            `--allowedTools`. Single entry `"*"` (the default) means
            "every tool from this server" — convenient but trusting.
            Tighten to a specific list when you only want a subset.
            Names are bare (e.g. `send_message`); the harness prepends
            `mcp__<server-key>__` at build time.
          '';
        };
      };
    });
    default = { };
    example = lib.literalExpression ''
      {
        matrix = {
          command = "/run/current-system/sw/bin/mcp-matrix";
          args = [ "--config" "/state/matrix.toml" ];
          env.MATRIX_HOMESERVER = "https://matrix.example.org";
          allowedTools = [ "send_message" "join_room" ];
        };
      }
    '';
    description = ''
      Extra MCP servers claude sees alongside the hyperhive tool surface.
      Keys are the server names (claude addresses tools as
      `mcp__<key>__<tool>`). Rendered to `/etc/hyperhive/extra-mcp.json`
      at activation time; the harness reads that file at boot and merges
      it into `--mcp-config` + `--allowedTools`. Take effect on the
      agent's next harness restart (no operator approval needed beyond
      whatever brought the new agent.nix into deployed/*).
    '';
  };

  config = {
    environment.etc."hyperhive/extra-mcp.json".text =
      builtins.toJSON config.hyperhive.extraMcpServers;

    boot.isNspawnContainer = true;

    # `claude-code` is unfree. Each per-agent container's nixosConfiguration
    # evaluates its own `nixpkgs` instance, so the operator's host-level
    # `nixpkgs.config.allowUnfreePredicate` does not propagate into here —
    # we have to allow it inside the container's config as well.
    nixpkgs.config.allowUnfreePredicate = pkg: builtins.elem (pkgs.lib.getName pkg) [ "claude-code" ];

    environment.systemPackages = with pkgs; [
      hyperhive
      claude-code
      bashInteractive
      coreutils-full
      # procps for pkill — used by the web UI's /api/cancel to SIGINT the
      # in-flight claude turn.
      procps
    ];

    # Git is needed by claude's Bash tool (for the agent <-> manager config
    # request flow) and by hive-c0re's own setup_applied / setup_proposed.
    # The per-agent `applied/<name>/flake.nix` overrides `user.name` and
    # `user.email` with the agent's identity — values here are `mkDefault`
    # so the per-agent override wins without needing `mkForce`.
    programs.git = {
      enable = true;
      config = {
        user = {
          name = lib.mkDefault "hyperhive";
          email = lib.mkDefault "hyperhive@local";
        };
        init.defaultBranch = lib.mkDefault "main";
      };
    };

    # claude's Bash tool refuses to run without a POSIX shell + $SHELL set.
    environment.variables.SHELL = "${pkgs.bashInteractive}/bin/bash";

    system.stateVersion = "25.11";
  };
}