diff --git a/internal/cli/helpers.go b/internal/cli/helpers.go
index 38997f1..39b2196 100644
--- a/internal/cli/helpers.go
+++ b/internal/cli/helpers.go
@@ -5,7 +5,6 @@ import (
 	"errors"
 	"fmt"
 	"io"
-	"os"
 	"strings"
 
 	service "github.com/devr-tools/codeguard/pkg/codeguard"
@@ -54,7 +53,7 @@ func loadScanConfigWithFallback(path string, profile string, targetPath string,
 	if err == nil {
 		return applyProfileOverride(cfg, profile)
 	}
-	if !defaultConfigRequested || strings.TrimSpace(targetPath) == "" || !errors.Is(err, os.ErrNotExist) {
+	if !defaultConfigRequested || strings.TrimSpace(targetPath) == "" || !errors.Is(err, service.ErrConfigNotFound) {
 		return service.Config{}, err
 	}
 
diff --git a/internal/codeguard/config/io.go b/internal/codeguard/config/io.go
index 7afe0ee..ec3a96a 100644
--- a/internal/codeguard/config/io.go
+++ b/internal/codeguard/config/io.go
@@ -17,6 +17,9 @@ import (
 const maxConfigFileBytes = 32 << 20
 
 var (
+	// ErrConfigNotFound identifies a missing top-level configuration file. It is
+	// distinct from missing artifacts referenced by an existing configuration.
+	ErrConfigNotFound    = errors.New("config file not found")
 	defaultConfigNames   = []string{"codeguard.yaml", "codeguard.yml", "codeguard.json"}
 	directoryConfigNames = []string{"codeguard.yaml", "codeguard.yml", "codeguard.json", "config.yaml", "config.yml", "config.json"}
 	defaultConfigDirs    = []string{".", ".codeguard"}
@@ -30,6 +33,9 @@ func LoadFile(path string) (core.Config, error) {
 
 	f, err := os.Open(resolvedPath) //nolint:gosec // operator-supplied config path; read is size-capped by LimitReader below
 	if err != nil {
+		if errors.Is(err, os.ErrNotExist) {
+			return core.Config{}, fmt.Errorf("%w: %w", ErrConfigNotFound, err)
+		}
 		return core.Config{}, err
 	}
 	defer func() { _ = f.Close() }()
diff --git a/pkg/codeguard/sdk_config.go b/pkg/codeguard/sdk_config.go
index 8bc0c33..e925f05 100644
--- a/pkg/codeguard/sdk_config.go
+++ b/pkg/codeguard/sdk_config.go
@@ -2,6 +2,9 @@ package codeguard
 
 import "github.com/devr-tools/codeguard/internal/codeguard/config"
 
+// ErrConfigNotFound identifies a missing top-level configuration file.
+var ErrConfigNotFound = config.ErrConfigNotFound
+
 // ExampleConfig returns CodeGuard's complete, ready-to-edit starter
 // configuration. It is intended for callers creating a new configuration,
 // rather than as a way to normalize a partial Config.
diff --git a/tests/cli/scan_test.go b/tests/cli/scan_test.go
index 3d6255e..9362bbe 100644
--- a/tests/cli/scan_test.go
+++ b/tests/cli/scan_test.go
@@ -235,6 +235,34 @@ func TestRunScanFolderWithExplicitMissingConfigStillFails(t *testing.T) {
 	}
 }
 
+func TestRunScanFolderWithMissingDesignRulesDoesNotFallBack(t *testing.T) {
+	cwd, err := os.Getwd()
+	if err != nil {
+		t.Fatalf("getwd: %v", err)
+	}
+	dir := t.TempDir()
+	if err := os.Chdir(dir); err != nil {
+		t.Fatalf("chdir tempdir: %v", err)
+	}
+	t.Cleanup(func() { _ = os.Chdir(cwd) })
+
+	writeScanTestFile(t, filepath.Join(dir, "codeguard.yml"), `
+name: repository-policy
+checks:
+  design_rules_file: .codeguard/missing-design-rules.yml
+`)
+	writeScanTestFile(t, filepath.Join(dir, "sub", "main.go"), "package main\n")
+
+	var stdout, stderr bytes.Buffer
+	code := cli.Run([]string{"scan", "-folder", "sub"}, strings.NewReader(""), &stdout, &stderr)
+	if code != 1 {
+		t.Fatalf("expected exit 1, got %d; stdout = %s", code, stdout.String())
+	}
+	if !strings.Contains(stderr.String(), "checks.design_rules_file") {
+		t.Fatalf("expected missing design rules error, got %s", stderr.String())
+	}
+}
+
 func writeScanTestFile(t *testing.T, path string, content string) {
 	t.Helper()
 	if err := os.MkdirAll(filepath.Dir(path), 0o755); err != nil {