diff --git a/src/lib/supabase.ts b/src/lib/supabase.ts
index 9e24ec2..d10ef56 100644
--- a/src/lib/supabase.ts
+++ b/src/lib/supabase.ts
@@ -1,4 +1,5 @@
 import { refreshSession, getStoredSession } from './auth';
+import { COLUMNS } from '../types';
 
 const SUPABASE_URL = 'https://hwithddwaapyhnfwcesj.supabase.co';
 const SUPABASE_ANON_KEY = 'sb_publishable_fGXkh0bSrAOqSk2jWKAzSg_NJD9YPCv';
@@ -323,6 +324,17 @@ export async function getHistoryDataForMerge(): Promise<Record<string, ExcelRow>
       for (const idx of changedIndices) {
         target[idx] = entry.new_data?.[idx];
       }
+
+      // CPNP values were saved through multiple code paths over time.
+      // Preserve the latest non-empty value even when a given history row
+      // does not surface it as a changed index.
+      const latestCpnp =
+        entry.new_data?.[COLUMNS.CPNP_NO] ??
+        entry.old_data?.[COLUMNS.CPNP_NO];
+
+      if (latestCpnp !== undefined && latestCpnp !== null && latestCpnp !== '') {
+        target[COLUMNS.CPNP_NO] = latestCpnp;
+      }
     }
 
     return result;