fix: nightly hardening - CLI config shape validation

promptlens/cli.py

@@ -102,6 +102,13 @@ def run(
         with open(config, "r") as f:
             config_data = yaml.safe_load(f)
 
+        if config_data is None:
+            console.print("[red]Invalid configuration: configuration file is empty[/red]")
+            sys.exit(1)
+        if not isinstance(config_data, dict):
+            console.print("[red]Invalid configuration: top-level YAML must be a mapping/object[/red]")
+            sys.exit(1)
+
         # Override with CLI options
         if golden_set:
             config_data["golden_set"] = golden_set

tests/test_cli_config_validation.py

@@ -0,0 +1,27 @@
+from pathlib import Path
+
+from click.testing import CliRunner
+
+from promptlens.cli import cli
+
+
+def test_run_rejects_empty_config_file(tmp_path: Path) -> None:
+    config = tmp_path / "empty.yaml"
+    config.write_text("", encoding="utf-8")
+
+    runner = CliRunner()
+    result = runner.invoke(cli, ["run", str(config), "--dry-run"])
+
+    assert result.exit_code == 1
+    assert "configuration file is empty" in result.output
+
+
+def test_run_rejects_non_mapping_top_level_config(tmp_path: Path) -> None:
+    config = tmp_path / "list.yaml"
+    config.write_text("- a\n- b\n", encoding="utf-8")
+
+    runner = CliRunner()
+    result = runner.invoke(cli, ["run", str(config), "--dry-run"])
+
+    assert result.exit_code == 1
+    assert "top-level YAML must be a mapping/object" in result.output