diff --git a/src/toolsgen/core/parallel.py b/src/toolsgen/core/parallel.py
index 269537b..3ad6017 100644
--- a/src/toolsgen/core/parallel.py
+++ b/src/toolsgen/core/parallel.py
@@ -133,6 +133,7 @@ def generate_records_parallel(
 
     results_by_index: Dict[int, Record] = {}
     failed = 0
+    next_id_to_write = 0
 
     ctx = mp.get_context("spawn")
     with ProcessPoolExecutor(
@@ -156,6 +157,13 @@ def generate_records_parallel(
                     if sample_result.record:
                         record = Record.model_validate(sample_result.record)
                         results_by_index[sample_result.sample_index] = record
+
+                        while next_id_to_write in results_by_index:
+                            rec = results_by_index[next_id_to_write]
+                            rec.id = f"record_{next_id_to_write:06d}"
+                            append_record_jsonl(rec, jsonl_path)
+                            del results_by_index[next_id_to_write]
+                            next_id_to_write += 1
                     else:
                         tqdm.write(
                             "Warning: Failed to generate sample "
@@ -170,8 +178,4 @@ def generate_records_parallel(
                     pbar.update(1)
 
     all_records = [results_by_index[i] for i in sorted(results_by_index.keys())]
-    for idx, record in enumerate(all_records):
-        record.id = f"record_{idx:06d}"
-        append_record_jsonl(record, jsonl_path)
-
     return all_records, failed