fix: reuse shared atomic session log helper

utils.py

@@ -9,17 +9,25 @@ from typing import Any, Union
 import yaml
 
 
-def atomic_json_write(path: Union[str, Path], data: Any, *, indent: int = 2) -> None:
+def atomic_json_write(
+    path: Union[str, Path],
+    data: Any,
+    *,
+    indent: int = 2,
+    **dump_kwargs: Any,
+) -> None:
     """Write JSON data to a file atomically.
 
     Uses temp file + fsync + os.replace to ensure the target file is never
-    left in a partially-written state.  If the process crashes mid-write,
+    left in a partially-written state. If the process crashes mid-write,
     the previous version of the file remains intact.
 
     Args:
         path: Target file path (will be created or overwritten).
         data: JSON-serializable data to write.
         indent: JSON indentation (default 2).
+        **dump_kwargs: Additional keyword args forwarded to json.dump(), such
+            as default=str for non-native types.
     """
     path = Path(path)
     path.parent.mkdir(parents=True, exist_ok=True)
@@ -31,7 +39,13 @@ def atomic_json_write(path: Union[str, Path], data: Any, *, indent: int = 2) ->
     )
     try:
         with os.fdopen(fd, "w", encoding="utf-8") as f:
-            json.dump(data, f, indent=indent, ensure_ascii=False)
+            json.dump(
+                data,
+                f,
+                indent=indent,
+                ensure_ascii=False,
+                **dump_kwargs,
+            )
             f.flush()
             os.fsync(f.fileno())
         os.replace(tmp_path, path)