fix(accounting): preserve dates in serialized payloads

litellm/accounting/snapshot.py

@@ -1,4 +1,5 @@
 from collections.abc import Callable, Mapping, Sequence
+from datetime import datetime
 from typing import TYPE_CHECKING, Final
 
 from pydantic import TypeAdapter
@@ -112,6 +113,10 @@ def build_accounting_payload(
         )
     )
     return {
-        **{key: value for key, value in payload.items() if key in _ACCOUNTING_FIELDS},
+        **{
+            key: value.isoformat() if isinstance(value, datetime) else value
+            for key, value in payload.items()
+            if key in _ACCOUNTING_FIELDS
+        },
         "metadata": {key: value for key, value in metadata.items() if key in ACCOUNTING_METADATA_FIELDS},
     }

tests/unit/accounting/test_projection.py

@@ -69,6 +69,7 @@ async def test_daily_projection_matches_legacy_writer(status: str, origin: str |
     restored: Final = _FIELDS.validate_json(json.dumps(accounting, default=str))
     stored_daily: Final = next(item for item in project(restored) if item.table == "LiteLLM_DailyUserSpend")
     assert dict(stored_daily.increments) == {name: legacy[name] for name, _ in stored_daily.increments}
+    assert stored_daily.key == projected.key
     assert not {"messages", "response", "proxy_server_request", "requester_ip_address"}.intersection(accounting)