diff --git a/app/javascript/dashboard/helper/CacheHelper/DataManager.js b/app/javascript/dashboard/helper/CacheHelper/DataManager.js
index 909301e70..22be6cbde 100644
--- a/app/javascript/dashboard/helper/CacheHelper/DataManager.js
+++ b/app/javascript/dashboard/helper/CacheHelper/DataManager.js
@@ -13,7 +13,17 @@ export class DataManager {
     if (this.db) return this.db;
     const dbName = `cw-store-${this.accountId}`;
     this.db = await openDB(dbName, DATA_VERSION, {
-      upgrade(db) {
+      upgrade(db, oldVersion, _newVersion, tx) {
+        // Flush data carried over from a previous schema version so a
+        // DATA_VERSION bump acts as a global cache reset. oldVersion === 0 on
+        // first install, so fresh devices skip this. Clearing before creating
+        // means we only ever clear stores that pre-existed this upgrade.
+        if (oldVersion > 0) {
+          [...db.objectStoreNames].forEach(name =>
+            tx.objectStore(name).clear()
+          );
+        }
+
         if (!db.objectStoreNames.contains('cache-keys')) {
           db.createObjectStore('cache-keys');
         }
diff --git a/app/javascript/dashboard/helper/CacheHelper/version.js b/app/javascript/dashboard/helper/CacheHelper/version.js
index 8cd958863..bdf5b04c3 100644
--- a/app/javascript/dashboard/helper/CacheHelper/version.js
+++ b/app/javascript/dashboard/helper/CacheHelper/version.js
@@ -1,9 +1,9 @@
-// Bump DATA_VERSION whenever a new object store is added to the IDB schema
-// (the `upgrade()` callback in DataManager only runs when the stored DB
-// version is less than the requested version). The upgrade body itself is
-// idempotent — it conditionally creates each store via
-// `objectStoreNames.contains(name)` — so a single bump is enough to add any
-// number of new stores without losing existing data.
+// Bump DATA_VERSION to (a) add new object stores to the IDB schema or (b)
+// flush bad/stale cache globally. The `upgrade()` callback in DataManager runs
+// only when the stored DB version is less than the requested version; on any
+// such bump it clears every existing store (a full cache reset) and then
+// idempotently creates any missing stores. So bump this whenever a cached
+// model's serializer shape changes, or to force all clients to refetch.
 //
 // Wednesday, 21 May 2026 — bumped to add canned_response + account_user stores
 export const DATA_VERSION = '1747785600';