diff --git a/modules/EcommerceFinance/Services/BusinessMirrorSynchronizer.php b/modules/EcommerceFinance/Services/BusinessMirrorSynchronizer.php
index 6d36af0b..258bb831 100644
--- a/modules/EcommerceFinance/Services/BusinessMirrorSynchronizer.php
+++ b/modules/EcommerceFinance/Services/BusinessMirrorSynchronizer.php
@@ -50,7 +50,10 @@ class BusinessMirrorSynchronizer
         );
         $cursor = is_array($state['cursor'] ?? null) ? $state['cursor'] : null;
         $highWatermark = is_array($state['high_watermark'] ?? null) ? $state['high_watermark'] : [];
-        $batchSize = min(max($batchSize ?? (int) config('upstream_mirrors.table_sync.batch_size', 500), 1), 2000);
+        // Routine runs keep the configured 500-row default. A larger explicit
+        // batch is reserved for supervised first syncs so wide SQL Server views
+        // need fewer repeated keyset scans without creating unbounded PHP arrays.
+        $batchSize = min(max($batchSize ?? (int) config('upstream_mirrors.table_sync.batch_size', 500), 1), 5000);
         $maxBatches = max($maxBatches ?? (int) config('upstream_mirrors.table_sync.max_batches_per_run', 2), 0);
         $batches = 0;
         $rows = (int) ($state['last_upserted_rows'] ?? 0);
diff --git a/tests/Unit/EcommerceFinance/BusinessMirrorSynchronizerTest.php b/tests/Unit/EcommerceFinance/BusinessMirrorSynchronizerTest.php
index 93c65ee1..bcc8e7de 100644
--- a/tests/Unit/EcommerceFinance/BusinessMirrorSynchronizerTest.php
+++ b/tests/Unit/EcommerceFinance/BusinessMirrorSynchronizerTest.php
@@ -146,6 +146,17 @@ class BusinessMirrorSynchronizerTest extends TestCase
         $this->assertSame([], $this->query->calls);
     }
 
+    public function test_supervised_full_sync_caps_explicit_batch_size_at_five_thousand(): void
+    {
+        $this->query->batches = [[
+            ['Id' => 1, 'updateTime' => '2026-08-14 10:00:00', 'displayName' => '一号', 'businessDate' => '2026-08-14'],
+        ]];
+
+        $this->synchronizer->sync('test.dbo.records', true, 50000, 1);
+
+        $this->assertStringContainsString('SELECT TOP (5000)', $this->query->calls[0]['sql']);
+    }
+
     public function test_full_sync_sanitizes_invalid_utf8_text_without_changing_valid_text(): void
     {
         $this->query->batches = [[