Default interactive CLI to menu

AGENTS.md

@@ -46,6 +46,8 @@ Guidance for coding agents working in this repo.
 - Be careful with duplicate instance names across Windows and local roots. Use
   the menu or pass `--instances-root` explicitly when targeting one install, and
   keep install/bootstrap state separate per target root.
+- After completing repo changes, suggest a concise commit message in the final
+  response unless the user already asked you to commit.
 
 ## Validation
 

README.md

@@ -66,9 +66,12 @@ backups, and installed file records for different game trees.
 For normal use, run the Textual menu from the repo root:
 
 ```sh
-PYTHONPATH=src python -m plugin_helper menu
+PYTHONPATH=src python -m plugin_helper
 ```
 
+That is equivalent to `PYTHONPATH=src python -m plugin_helper menu` when run
+from an interactive terminal.
+
 The menu reads `plugin-helper.local.toml` when present, shows each discovered
 Beat Saber install with its resolved state directory, and lets you toggle
 managed plugins with arrow keys and Space. In the plugin table, use `d` to

src/plugin_helper/cli.py

@@ -70,7 +70,7 @@ def _add_common(parser: argparse.ArgumentParser, *, suppress_default: bool = Fal
 def build_parser() -> argparse.ArgumentParser:
     parser = argparse.ArgumentParser(prog="plugin-helper")
     _add_common(parser)
-    subcommands = parser.add_subparsers(dest="command", required=True)
+    subcommands = parser.add_subparsers(dest="command")
 
     subcommands.add_parser(
         "instances",
@@ -309,6 +309,13 @@ def run(argv: list[str] | None = None) -> int:
     args = parser.parse_args(argv)
 
     try:
+        if args.command is None:
+            if sys.stdin.isatty() and sys.stdout.isatty():
+                args.command = "menu"
+            else:
+                parser.print_help()
+                return 2
+
         explicit_instances_root = getattr(args, "instances_root", None) is not None
         explicit_state_dir = getattr(args, "state_dir", None) is not None
         runtime = resolve_runtime_config(

tests/test_plugin_helper.py

@@ -4,6 +4,7 @@ import json
 import tempfile
 import unittest
 import os
+from io import StringIO
 from pathlib import Path
 from unittest.mock import patch
 from zipfile import ZipFile
@@ -180,6 +181,26 @@ state_dir = ".state"
             self.assertEqual(runtime.state_root, root / "explicit-state")
             self.assertEqual(runtime.selected_profile.id, "linux")
 
+    def test_no_args_prints_help_when_not_interactive(self) -> None:
+        output = StringIO()
+        with patch("sys.stdin.isatty", return_value=False), patch("sys.stdout", output):
+            status = run([])
+
+        self.assertEqual(status, 2)
+        self.assertIn("usage: plugin-helper", output.getvalue())
+        self.assertIn("menu", output.getvalue())
+
+    def test_no_command_defaults_to_menu_when_interactive(self) -> None:
+        with (
+            patch("sys.stdin.isatty", return_value=True),
+            patch("sys.stdout.isatty", return_value=True),
+            patch("plugin_helper.cli._run_menu", return_value=0) as run_menu,
+        ):
+            status = run(["--profile", "linux"])
+
+        self.assertEqual(status, 0)
+        run_menu.assert_called_once()
+
     def test_run_ipa_timeout_returns_control(self) -> None:
         with tempfile.TemporaryDirectory() as tmp:
             result = _run_ipa(