Preserve owning categories in public errors

errors_internal_test.go

@@ -80,3 +80,12 @@ func TestMapPublicErrorDoesNotTreatRequestEncodingAsTransport(t *testing.T) {
 		t.Fatalf("request encoding category = %v", err)
 	}
 }
+
+func TestMapPublicErrorRetainsOwnerWithSpecializedCapacity(t *testing.T) {
+	internal := &usecase.CapacityError{BackendID: "limited"}
+	err := mapPublicError(&usecase.OperationError{Category: usecase.ErrLLMGenerate, Cause: internal})
+	var capacity *CapacityError
+	if !errors.Is(err, ErrLLMGenerate) || !errors.As(err, &capacity) || capacity.BackendID != "limited" || !errors.Is(err, ErrCapacityExceeded) {
+		t.Fatalf("mapped owned capacity = %v", err)
+	}
+}