diff --git a/klausur-service/backend/ocr_pipeline_sessions.py b/klausur-service/backend/ocr_pipeline_sessions.py
index cd747b8..22e00d2 100644
--- a/klausur-service/backend/ocr_pipeline_sessions.py
+++ b/klausur-service/backend/ocr_pipeline_sessions.py
@@ -222,7 +222,12 @@ async def _create_multi_page_sessions(
             f"(page {page_idx + 1}/{page_count}) from {filename} ({w}x{h})"
         )
 
+    # Include session_id pointing to first page for backwards compatibility
+    # (frontends that expect a single session_id will navigate to page 1)
+    first_session_id = pages[0]["session_id"] if pages else None
+
     return {
+        "session_id": first_session_id,
         "document_group_id": document_group_id,
         "filename": filename,
         "name": base_name,