Stabilize application config support

internal/adapter/cli/run_test.go

@@ -322,6 +322,22 @@ func TestParseRunArgsMissingExplicitConfigReturnsError(t *testing.T) {
 	}
 }
 
+func TestParseRunArgsInvalidExplicitConfigReturnsError(t *testing.T) {
+	configPath := writeAppConfigFile(t, "api_key: secret\n")
+
+	_, err := parseRunArgs([]string{
+		"--config", configPath,
+		"--prompt", "p",
+		"--input", "a=b",
+	})
+	if err == nil {
+		t.Fatal("expected invalid explicit config error")
+	}
+	if !strings.Contains(err.Error(), "application config error") {
+		t.Fatalf("expected application config context, got %v", err)
+	}
+}
+
 func TestResolveAppSettingsMissingImplicitConfigDoesNotError(t *testing.T) {
 	fs := flag.NewFlagSet("test", flag.ContinueOnError)
 	settings, err := resolveAppSettings(fs, filepath.Join(t.TempDir(), "missing.yml"), appconfig.CLIOverrides{})