diff --git a/rag_evaluation.py b/rag_evaluation.py
index 50b5826..bcb868e 100644
--- a/rag_evaluation.py
+++ b/rag_evaluation.py
@@ -549,6 +549,14 @@ def update_batch_stats(store: dict[str, Any], batch_meta: dict[str, Any]) -> Non
     store.setdefault("meta", {})["updated_at"] = now_iso()
 
 
+def atomic_write_json(path: Path, payload: dict[str, Any]) -> None:
+    """Atomically write JSON to avoid partial/corrupted files on interruption."""
+    path.parent.mkdir(parents=True, exist_ok=True)
+    tmp_path = path.with_suffix(path.suffix + ".tmp")
+    tmp_path.write_text(json.dumps(payload, ensure_ascii=False, indent=2), encoding="utf-8")
+    tmp_path.replace(path)
+
+
 def compute_batch_summary(results: list[DocumentEvaluation]) -> dict[str, Any]:
     wins = {"LangChain": 0, "LlamaIndex": 0, "Tie": 0}
     scores_lc: list[float] = []
@@ -660,9 +668,7 @@ def run_evaluation(doc_from: int, doc_to: int, mode: str) -> None:
         batch_results.append(doc_result)
 
         # Save incremental progress after each file/step
-        OUTPUT_JSON.write_text(
-            json.dumps(store, ensure_ascii=False, indent=2), encoding="utf-8"
-        )
+        atomic_write_json(OUTPUT_JSON, store)
         print("  -> step saved")
 
     summary = compute_batch_summary(batch_results)
@@ -674,9 +680,7 @@ def run_evaluation(doc_from: int, doc_to: int, mode: str) -> None:
         "mode": mode,
     }
     update_batch_stats(store, batch_meta)
-    OUTPUT_JSON.write_text(
-        json.dumps(store, ensure_ascii=False, indent=2), encoding="utf-8"
-    )
+    atomic_write_json(OUTPUT_JSON, store)
 
     print("\nBatch complete.")
     print(json.dumps(summary, ensure_ascii=False, indent=2))