{
  config,
  lib,
  pkgs,
  ...
}:
let
  cfg = config.claude;
  settingsFile = (pkgs.formats.json { }).generate "claude-settings.json" cfg.settings;
  mcpConfigFile = (pkgs.formats.json { }).generate "claude-mcp.json" {
    mcpServers = cfg.mcpServers;
  };
  hasMcp = cfg.mcpServers != { };
in
{
  options.claude = {
    enable = lib.mkEnableOption "Claude Code";
    package = lib.mkOption {
      type = lib.types.package;
      description = "The Claude Code package; must provide bin/claude.";
    };
    settings = lib.mkOption {
      type = (pkgs.formats.json { }).type;
      default = { };
      description = "Settings layered over the account's settings.json via --settings.";
    };
    plugins = lib.mkOption {
      type = lib.types.listOf lib.types.path;
      default = [ ];
      description = "Plugin directories, loaded with --plugin-dir. Nothing is installed into the account.";
    };
    mcpServers = lib.mkOption {
      type = (pkgs.formats.json { }).type;
      default = { };
      description = "MCP servers (the mcpServers object of an MCP JSON file), loaded with --mcp-config. Credentials stay in the account.";
    };
  };

  config.build.agents.claude = lib.mkIf cfg.enable {
    exe = lib.getExe' cfg.package "claude";
    stateEnvVar = "CLAUDE_CONFIG_DIR";
    instructionsFile = "CLAUDE.md";
    # Managed links: path relative to the state dir -> store path.
    files = { };
    # --mcp-config is variadic and would swallow the user's arguments if it came
    # last, so it goes first and --settings always follows it.
    flags =
      lib.optionals hasMcp [
        "--mcp-config"
        "${mcpConfigFile}"
      ]
      ++ lib.optionals (cfg.settings != { } || hasMcp) [
        "--settings"
        "${settingsFile}"
      ]
      ++ lib.concatMap (p: [
        "--plugin-dir"
        "${p}"
      ]) cfg.plugins;
  };
}