diff --git a/src/app/op-log/sync-providers/file-based/file-based-sync-adapter.service.ts b/src/app/op-log/sync-providers/file-based/file-based-sync-adapter.service.ts
index c061caabc3..66088a9fc8 100644
--- a/src/app/op-log/sync-providers/file-based/file-based-sync-adapter.service.ts
+++ b/src/app/op-log/sync-providers/file-based/file-based-sync-adapter.service.ts
@@ -802,14 +802,14 @@ export class FileBasedSyncAdapterService {
       `FileBasedSyncAdapter: Downloaded ${limitedOps.length} ops (new/total: ${filteredOps.length}/${latestSeq})`,
     );
 
-    // Mark downloaded ops as processed (unless it's a force-from-zero request,
-    // where the caller is expected to process and then call setLastServerSeq)
-    if (!isForceFromZero) {
-      for (const serverOp of limitedOps) {
-        this._markOpProcessed(providerKey, serverOp.op.id);
-      }
-      this._persistState();
+    // Mark downloaded ops as processed for piggyback tracking.
+    // This must happen for ALL downloads, including force-from-zero (fresh client).
+    // Without marking, the upload piggyback mechanism (_collectPiggybackedOps) will
+    // return these same ops during the next upload, causing entity duplication.
+    for (const serverOp of limitedOps) {
+      this._markOpProcessed(providerKey, serverOp.op.id);
     }
+    this._persistState();
 
     // NOTE: Archives are NOT written to IndexedDB here. They are included in the
     // snapshotState response and written to IndexedDB during hydrateFromRemoteSync()
diff --git a/src/app/op-log/sync/operation-log-sync.service.ts b/src/app/op-log/sync/operation-log-sync.service.ts
index a661e23cd2..f1fe260118 100644
--- a/src/app/op-log/sync/operation-log-sync.service.ts
+++ b/src/app/op-log/sync/operation-log-sync.service.ts
@@ -447,6 +447,19 @@ export class OperationLogSyncService {
         false, // Don't create SYNC_IMPORT for file-based bootstrap
       );
 
+      // CRITICAL FIX: Write recentOps to IndexedDB after snapshot hydration.
+      // File-based providers return ALL recentOps on every download, relying on
+      // getAppliedOpIds() (from IndexedDB) to filter already-applied ops.
+      // Without writing these ops, they bypass the filter on the next sync cycle
+      // and get applied again, duplicating entities.
+      if (result.newOps.length > 0) {
+        await this.opLogStore.appendBatch(result.newOps, 'remote');
+        OpLog.normal(
+          `OperationLogSyncService: Wrote ${result.newOps.length} snapshot ops to IndexedDB ` +
+            '(prevents duplication on next sync cycle).',
+        );
+      }
+
       // Persist lastServerSeq after hydration
       if (result.latestServerSeq !== undefined) {
         await syncProvider.setLastServerSeq(result.latestServerSeq);
@@ -734,6 +747,17 @@ export class OperationLogSyncService {
         false, // Don't create SYNC_IMPORT
       );
 
+      // CRITICAL FIX: Write recentOps to IndexedDB after snapshot hydration.
+      // Same rationale as downloadRemoteOps: file-based providers return ALL
+      // recentOps on every download and rely on getAppliedOpIds() to filter them.
+      if (result.newOps.length > 0) {
+        await this.opLogStore.appendBatch(result.newOps, 'remote');
+        OpLog.normal(
+          `OperationLogSyncService: Wrote ${result.newOps.length} snapshot ops to IndexedDB ` +
+            'after force-download hydration.',
+        );
+      }
+
       // Update lastServerSeq after hydration
       if (result.latestServerSeq !== undefined) {
         await syncProvider.setLastServerSeq(result.latestServerSeq);