diff --git a/app/api/routes/device_ws.py b/app/api/routes/device_ws.py
index 6b6510c..709eb90 100644
--- a/app/api/routes/device_ws.py
+++ b/app/api/routes/device_ws.py
@@ -598,9 +598,9 @@ async def _handle_index_session_start(
     frame: dict,
 ) -> None:
     """Register a new folder index session.  No response sent — client is declaring intent."""
-    session_id: str = frame.get("sessionId") or frame.get("session_id", "")
+    session_id: str = frame.get("sessionId") or frame.get("session_id") or ""
     project_id: str | None = frame.get("projectId") or frame.get("project_id")
-    total: int = int(frame.get("totalFiles", 0))
+    total: int = int(frame.get("totalFiles") or frame.get("total_files") or 0)
 
     if not session_id:
         logger.warning("device_ws: index_session_start missing sessionId user=%s", user_id)
@@ -624,7 +624,7 @@ async def _handle_index_session_cancel(
     frame: dict,
 ) -> None:
     """Mark a session as cancelled and emit index_session_done(cancelled)."""
-    session_id: str = frame.get("sessionId") or frame.get("session_id", "")
+    session_id: str = frame.get("sessionId") or frame.get("session_id") or ""
     session = _index_sessions.get(session_id)
     if session:
         session["cancelled"] = True
@@ -654,7 +654,7 @@ async def _handle_index_file_batch(
     from app.billing.tier_manager import tier_manager  # noqa: PLC0415
     from app.billing.quota import add_token_usage  # noqa: PLC0415
 
-    session_id: str = frame.get("sessionId") or frame.get("session_id", "")
+    session_id: str = frame.get("sessionId") or frame.get("session_id") or ""
     files: list[dict] = frame.get("files", [])
 
     session = _index_sessions.get(session_id)
@@ -670,11 +670,12 @@ async def _handle_index_file_batch(
             if session.get("cancelled"):
                 return
 
-            rel_path: str = file_info.get("relPath", "")
-            kind: str = file_info.get("kind", "text")
-            content: str = file_info.get("content", "")
-            ext: str = file_info.get("ext", "")
-            mime: str = file_info.get("mime", "application/octet-stream")
+            # Electron's toSnakeCase converts payload keys, so accept both forms.
+            rel_path: str = file_info.get("relPath") or file_info.get("rel_path") or ""
+            kind: str = file_info.get("kind") or "text"
+            content: str = file_info.get("content") or ""
+            ext: str = file_info.get("ext") or ""
+            mime: str = file_info.get("mime") or "application/octet-stream"
             name: str = rel_path.split("/")[-1] or rel_path
 
             try: