diff --git a/internal/source/errors.go b/internal/source/errors.go
index d99e3b4..bdc262c 100644
--- a/internal/source/errors.go
+++ b/internal/source/errors.go
@@ -31,7 +31,9 @@ func (e *SourceError) Unwrap() error {
 	return e.Err
 }
 
-func errorKind(err error) ErrorKind {
+// KindOf returns the source error category contained in err.
+// It returns ErrorKindUnknown when err has no SourceError in its chain.
+func KindOf(err error) ErrorKind {
 	var sourceErr *SourceError
 	if errors.As(err, &sourceErr) {
 		return sourceErr.Kind
diff --git a/internal/source/errors_test.go b/internal/source/errors_test.go
index bb6178f..a025178 100644
--- a/internal/source/errors_test.go
+++ b/internal/source/errors_test.go
@@ -6,12 +6,12 @@ import (
 	"testing"
 )
 
-func TestErrorKindThroughWrapping(t *testing.T) {
+func TestKindOfThroughWrapping(t *testing.T) {
 	base := errors.New("producer disappeared")
 	wrapped := wrapError("read video", ErrorKindUnavailable, base)
 	outer := fmt.Errorf("worker failed: %w", wrapped)
 
-	if got := errorKind(outer); got != ErrorKindUnavailable {
+	if got := KindOf(outer); got != ErrorKindUnavailable {
 		t.Fatalf("errorKind() = %v, want %v", got, ErrorKindUnavailable)
 	}
 	if !errors.Is(outer, base) {
@@ -22,8 +22,8 @@ func TestErrorKindThroughWrapping(t *testing.T) {
 	}
 }
 
-func TestErrorKindUnknown(t *testing.T) {
-	if got := errorKind(errors.New("ordinary error")); got != ErrorKindUnknown {
+func TestKindOfUnknown(t *testing.T) {
+	if got := KindOf(errors.New("ordinary error")); got != ErrorKindUnknown {
 		t.Fatalf("errorKind() = %v, want %v", got, ErrorKindUnknown)
 	}
 }