running without arguments prints the help

chromy/cli.py

@@ -25,7 +25,8 @@ app = typer.Typer(
         "- By default, Chromy uses Chroma's default persistent location behavior.\n"
         f"- Set {CHROMA_FOLDER_ENV_VAR} to a parent directory to override it.\n"
         f"- Chromy stores data in <{CHROMA_FOLDER_ENV_VAR}>/chroma."
-    )
+    ),
+    invoke_without_command=True,
 )
 
 ExitCodeHandler = Callable[[], int]
@@ -46,6 +47,15 @@ def _fail(message: str) -> None:
     raise typer.Exit(1)
 
 
+@app.callback()
+def main(ctx: typer.Context) -> None:
+    """Run the CLI and show help when no command is provided."""
+    if ctx.invoked_subcommand is None:
+        print("[bold red]Error[/]: Missing command.")
+        typer.echo(ctx.get_help())
+        raise typer.Exit(1)
+
+
 # ------------------------------------------------------------------------------
 # LIST COLLECTIONS
 # ------------------------------------------------------------------------------

tests/test_cli.py

@@ -252,6 +252,14 @@ class CliTests(unittest.TestCase):
         self.assertNotEqual(result.exit_code, 0)
         self.assertIn("Missing option", result.output)
 
+    def test_cli_without_arguments_prints_error_and_help(self) -> None:
+        result = _invoke([])
+
+        self.assertEqual(result.exit_code, 1)
+        self.assertIn("Error: Missing command.", result.stdout)
+        self.assertIn("Usage:", result.stdout)
+        self.assertIn("Commands", result.stdout)
+
     def test_cli_help_documents_chroma_folder_env_var(self) -> None:
         result = _invoke(["--help"])