diff --git a/src/routes/+layout.ts b/src/routes/+layout.ts
index d948a83e..908951b4 100644
--- a/src/routes/+layout.ts
+++ b/src/routes/+layout.ts
@@ -182,7 +182,8 @@ export async function load({ fetch, params, parent, route, url }) {
                         check_event_device_loop_period: (existing_dev as any).check_event_device_loop_period || incoming_dev.check_event_device_loop_period,
                         check_event_location_loop_period: (existing_dev as any).check_event_location_loop_period || incoming_dev.check_event_location_loop_period,
                         check_event_session_loop_period: (existing_dev as any).check_event_session_loop_period || incoming_dev.check_event_session_loop_period,
-                        hash_prefix_length: (existing_dev as any).hash_prefix_length || incoming_dev.hash_prefix_length
+                        // Use API value if present; default to 2 (never preserve from localStorage — stale values cause orphaned cache dirs)
+                        hash_prefix_length: incoming_dev.hash_prefix_length || 2
                     };
 
                     // Map specific operational paths