opencode: init (#7320)

modules/programs/opencode.nix

@@ -0,0 +1,53 @@
+{
+  lib,
+  pkgs,
+  config,
+  ...
+}:
+let
+  inherit (lib)
+    literalExpression
+    mkEnableOption
+    mkIf
+    mkOption
+    mkPackageOption
+    ;
+
+  cfg = config.programs.opencode;
+
+  jsonFormat = pkgs.formats.json { };
+in
+{
+  meta.maintainers = with lib.hm.maintainers; [ delafthi ];
+
+  options.programs.opencode = {
+    enable = mkEnableOption "opencode";
+
+    package = mkPackageOption pkgs "opencode" { nullable = true; };
+
+    settings = mkOption {
+      inherit (jsonFormat) type;
+      default = { };
+      example = literalExpression ''
+        {
+          theme = "opencode";
+          model = "anthropic/claude-sonnet-4-20250514";
+          autoshare = false;
+          autoupdate = true;
+        }
+      '';
+      description = ''
+        Configuration written to {file}`$XDG_CONFIG_HOME/opencode/config.json`.
+        See <https://opencode.ai/docs/config/> for the documentation.
+      '';
+    };
+  };
+
+  config = mkIf cfg.enable {
+    home.packages = mkIf (cfg.package != null) [ cfg.package ];
+
+    xdg.configFile."opencode/config.json" = mkIf (cfg.settings != { }) {
+      source = jsonFormat.generate "config.json" cfg.settings;
+    };
+  };
+}