1 files changed, 33 insertions, 0 deletions
diff --git a/internal/admin/api_entity_path_test.go b/internal/admin/api_entity_path_test.go
index 7abf65f..27ecbe8 100644
--- a/internal/admin/api_entity_path_test.go
+++ b/internal/admin/api_entity_path_test.go
@@ -8,6 +8,7 @@ import (
 	"strings"
 	"testing"
 
+	"thehouseoficarus/internal/behavior"
 	"thehouseoficarus/internal/config"
 	"thehouseoficarus/internal/player"
 )
@@ -60,3 +61,35 @@ func TestEntityAPICannotEscapeData(t *testing.T) {
 		t.Fatal("entity API escaped the data directory")
 	}
 }
+
+// TestEntityRenameRejectsDuplicateIDInOtherDirectory: entity IDs are global
+// across the type's subdirectory tree (the runtime path indexes resolve by
+// filename anywhere under data/<subdir>), so renaming into an ID that
+// exists in a DIFFERENT directory must be rejected instead of creating a
+// duplicate ID shadowed by whichever file the index finds first.
+func TestEntityRenameRejectsDuplicateIDInOtherDirectory(t *testing.T) {
+	dir := t.TempDir()
+	for _, sub := range []string{"items/a", "items/b"} {
+		if err := os.MkdirAll(filepath.Join(dir, sub), 0o755); err != nil {
+			t.Fatal(err)
+		}
+	}
+	if err := os.WriteFile(filepath.Join(dir, "items/a/old.yaml"), []byte("name: Original\n"), 0o644); err != nil {
+		t.Fatal(err)
+	}
+	if err := os.WriteFile(filepath.Join(dir, "items/b/taken.yaml"), []byte("name: Existing\n"), 0o644); err != nil {
+		t.Fatal(err)
+	}
+
+	if _, _, _, err := renameEntityFile(dir, "items", "old", "taken"); err == nil {
+		t.Fatal("rename accepted an ID that already exists in another directory")
+	}
+	if dups := behavior.CheckDuplicateIDs(filepath.Join(dir, "items")); len(dups) != 0 {
+		t.Fatalf("rename produced duplicate IDs: %+v", dups)
+	}
+
+	// Renaming within the same directory to a free name still works.
+	if _, _, _, err := renameEntityFile(dir, "items", "old", "moved"); err != nil {
+		t.Fatalf("ordinary rename rejected: %v", err)
+	}
+}