diff --git a/CLAUDE.md b/CLAUDE.md
index 747e34e..d228123 100644
--- a/CLAUDE.md
+++ b/CLAUDE.md
@@ -57,6 +57,29 @@ if (UPS_Editor_SceneLoader::IsInEditorMode())
     // editor-only behaviour
 }
 ```
+
+### Known PIE-only AI quirk — use Standalone for AI testing
+
+When the editor's "Play" button calls `UGameplayStatics::OpenLevel(BaseLevel)` from a PIE
+session, the BaseLevel's `RecastNavMesh` actor ends up pending-kill at registration time
+(UE logs `RegistrationFailed_DataPendingKill` ×2 and silently spawns an empty
+`AbstractNavData-Default` as fallback). All `FindPathAsync` / `ProjectPointToNavigation`
+queries return empty after that — pathfinding looks broken with no error.
+
+This is **PIE-specific**:
+- Standalone Game (Window → Standalone) — works correctly
+- Packaged builds — work correctly
+- PIE direct on BaseLevel (no editor map / OpenLevel involved) — works correctly
+- PIE on editor map → click Play (OpenLevel transition inside PIE) — broken
+
+Multiple workaround attempts have all failed (cascading re-registrations through
+`RegisterNavData` / `OnInitializeActors` / `AddNavigationSystemToWorld` / `Build` /
+`SpawnMissingNavigationData`; transition map; duplicated sublevel suffixed `_default`).
+The cause is internal to PIE's OpenLevel handling and cannot be fixed from the plugin
+side without engine modifications.
+
+**Workflow:** for AI iteration, run **Standalone Game** instead of PIE. It exercises the
+exact same code path as packaged builds.
 or gate on `bIsCurrentlyLoading` to skip BP init during JSON restore.
 
 ## UI Modes — IMPORTANT for widget changes