diff --git a/lightrag/kg/qdrant_impl.py b/lightrag/kg/qdrant_impl.py
index 23ec660e..0c2324d5 100644
--- a/lightrag/kg/qdrant_impl.py
+++ b/lightrag/kg/qdrant_impl.py
@@ -261,8 +261,37 @@ class QdrantVectorDBStorage(BaseVectorStorage):
                 return
 
             # Case 3: Only legacy exists - migrate data from legacy collection to new collection
+            # Check if legacy collection has workspace_id index to determine migration strategy
+            legacy_info = client.get_collection(legacy_collection)
+            has_workspace_index = WORKSPACE_ID_FIELD in (
+                legacy_info.payload_schema or {}
+            )
+
+            # Build workspace filter if legacy collection has workspace support
+            # This prevents cross-workspace data leakage during migration
+            legacy_scroll_filter = None
+            if has_workspace_index:
+                legacy_scroll_filter = models.Filter(
+                    should=[
+                        workspace_filter_condition(workspace),
+                        models.IsNullCondition(
+                            is_null=models.PayloadField(key=WORKSPACE_ID_FIELD)
+                        ),
+                    ]
+                )
+                # Recount with workspace filter for accurate migration tracking
+                legacy_count = client.count(
+                    collection_name=legacy_collection,
+                    count_filter=legacy_scroll_filter,
+                    exact=True,
+                ).count
+                logger.info(
+                    f"Qdrant: Legacy collection has workspace support, "
+                    f"filtering to {legacy_count} records for workspace '{workspace}'"
+                )
+
             logger.info(
-                f"Qdrant: Found legacy collection '{legacy_collection}' with {legacy_count} records."
+                f"Qdrant: Found legacy collection '{legacy_collection}' with {legacy_count} records to migrate."
             )
             logger.info(
                 f"Qdrant: Migrating data from legacy collection '{legacy_collection}' to new collection '{collection_name}'"
@@ -275,9 +304,10 @@ class QdrantVectorDBStorage(BaseVectorStorage):
                 batch_size = 500
 
                 while True:
-                    # Scroll through legacy data
+                    # Scroll through legacy data with optional workspace filter
                     result = client.scroll(
                         collection_name=legacy_collection,
+                        scroll_filter=legacy_scroll_filter,
                         limit=batch_size,
                         offset=offset,
                         with_vectors=True,
@@ -291,15 +321,15 @@ class QdrantVectorDBStorage(BaseVectorStorage):
                     # Transform points for new collection
                     new_points = []
                     for point in points:
-                        # Add workspace_id to payload
+                        # Set workspace_id in payload
                         new_payload = dict(point.payload or {})
-                        new_payload[WORKSPACE_ID_FIELD] = workspace or DEFAULT_WORKSPACE
+                        new_payload[WORKSPACE_ID_FIELD] = workspace
 
                         # Create new point with workspace-prefixed ID
                         original_id = new_payload.get(ID_FIELD)
                         if original_id:
                             new_point_id = compute_mdhash_id_for_qdrant(
-                                original_id, prefix=workspace or DEFAULT_WORKSPACE
+                                original_id, prefix=workspace
                             )
                         else:
                             # Fallback: use original point ID