From e7950b348dbda9d9b280ea5eed8c32c3a275efd2 Mon Sep 17 00:00:00 2001
From: Milan <milan@berri.ai>
Date: Fri, 1 May 2026 01:54:37 +0300
Subject: [PATCH] fix(proxy): do not reset member budget window on implicit
 duration

In-place updates only write budget_duration / budget_reset_at when
budget_duration was explicit in /team/member_update. Passing the team's
inherited default duration with explicit=False was recalculating
budget_reset_at and wiping mid-cycle spend (Greptile P1, PR #26779).

Add regression test test_upsert_in_place_omitted_duration_does_not_touch_duration_fields.

Made-with: Cursor
---
 .../management_endpoints/common_utils.py      | 32 ++++++++++---------
 .../test_upsert_budget_membership.py          | 31 ++++++++++++++++++
 2 files changed, 48 insertions(+), 15 deletions(-)

diff --git a/litellm/proxy/management_endpoints/common_utils.py b/litellm/proxy/management_endpoints/common_utils.py
index 3d6bebaf909..eb37dd1e5af 100644
--- a/litellm/proxy/management_endpoints/common_utils.py
+++ b/litellm/proxy/management_endpoints/common_utils.py
@@ -388,25 +388,28 @@ def _non_none_budget_limit_fields(
     return out
 
 
-def _apply_budget_duration_to_update_dict(
+def _apply_explicit_budget_duration_to_update_dict(
     update_data: Dict[str, Any],
     budget_duration: Optional[str],
-    budget_duration_explicit: bool,
 ) -> None:
-    if budget_duration_explicit:
-        if budget_duration is not None:
-            update_data["budget_duration"] = budget_duration
-            update_data["budget_reset_at"] = get_budget_reset_time(
-                budget_duration=budget_duration
-            )
-        else:
-            update_data["budget_duration"] = None
-            update_data["budget_reset_at"] = None
-    elif budget_duration is not None:
+    """
+    Persist ``budget_duration`` / ``budget_reset_at`` only when the caller
+    explicitly included ``budget_duration`` in the request (see
+    ``budget_duration_explicit`` at the /team/member_update layer).
+
+    When duration is omitted, inherited team defaults are still passed into
+    ``_upsert_budget_and_membership`` for *create* / clone paths, but in-place
+    updates must not rewrite ``budget_reset_at`` or the member's cycle is reset
+    mid-period (Greptile / PR #26779).
+    """
+    if budget_duration is not None:
         update_data["budget_duration"] = budget_duration
         update_data["budget_reset_at"] = get_budget_reset_time(
             budget_duration=budget_duration
         )
+    else:
+        update_data["budget_duration"] = None
+        update_data["budget_reset_at"] = None
 
 
 async def _update_existing_member_budget_in_place(
@@ -427,9 +430,8 @@ async def _update_existing_member_budget_in_place(
             max_budget, tpm_limit, rpm_limit, allowed_models
         ),
     }
-    _apply_budget_duration_to_update_dict(
-        update_data, budget_duration, budget_duration_explicit
-    )
+    if budget_duration_explicit:
+        _apply_explicit_budget_duration_to_update_dict(update_data, budget_duration)
     await tx.litellm_budgettable.update(
         where={"budget_id": existing_budget_id},
         data=update_data,
diff --git a/tests/test_litellm/proxy/common_utils/test_upsert_budget_membership.py b/tests/test_litellm/proxy/common_utils/test_upsert_budget_membership.py
index bfe63eef797..11effe69fe2 100644
--- a/tests/test_litellm/proxy/common_utils/test_upsert_budget_membership.py
+++ b/tests/test_litellm/proxy/common_utils/test_upsert_budget_membership.py
@@ -95,6 +95,37 @@ async def test_upsert_with_existing_budget_id_creates_new(mock_tx, fake_user):
     mock_tx.litellm_teammembership.update.assert_not_called()
 
 
+@pytest.mark.asyncio
+async def test_upsert_in_place_omitted_duration_does_not_touch_duration_fields(
+    mock_tx,
+    fake_user,
+):
+    """
+    When budget_duration was omitted from the API (explicit=False), an in-place
+    update must not write budget_duration / budget_reset_at even if the caller
+    passes a resolved team-default duration string (Greptile P1, PR #26779).
+    """
+    await _upsert_budget_and_membership(
+        mock_tx,
+        team_id="team-no-dur-touch",
+        user_id="user-no-dur-touch",
+        max_budget=10.0,
+        existing_budget_id="priv-budget-1",
+        user_api_key_dict=fake_user,
+        team_default_budget_id="team-default-xyz",
+        budget_duration="30d",
+        budget_duration_explicit=False,
+    )
+
+    mock_tx.litellm_budgettable.update.assert_awaited_once_with(
+        where={"budget_id": "priv-budget-1"},
+        data={
+            "max_budget": 10.0,
+            "updated_by": fake_user.user_id,
+        },
+    )
+
+
 # TEST: create new budget and link membership
 @pytest.mark.asyncio
 async def test_upsert_create_and_link(mock_tx, fake_user):