Fix date overflow/division by zero in proxy utils

litellm/proxy/utils.py

@@ -7,7 +7,7 @@
 import threading
 import time
 import traceback
-from datetime import datetime, timedelta
+from datetime import date, datetime, timedelta
 from email.mime.multipart import MIMEMultipart
 from email.mime.text import MIMEText
 from typing import (
@@ -3891,22 +3891,23 @@ def _raise_failed_update_spend_exception(
     raise e
 
 
+def _get_month_end_date(today: date) -> date:
+    if today.month == 12:
+        return date(today.year + 1, 1, 1) - timedelta(days=1)
+    return date(today.year, today.month + 1, 1) - timedelta(days=1)
+
+
 def _is_projected_spend_over_limit(
     current_spend: float, soft_budget_limit: Optional[float]
 ):
-    from datetime import date
-
     if soft_budget_limit is None:
         # If there's no limit, we can't exceed it.
         return False
 
     today = date.today()
 
     # Finding the first day of the next month, then subtracting one day to get the end of the current month.
-    if today.month == 12:  # December edge case
-        end_month = date(today.year + 1, 1, 1) - timedelta(days=1)
-    else:
-        end_month = date(today.year, today.month + 1, 1) - timedelta(days=1)
+    end_month = _get_month_end_date(today)
 
     remaining_days = (end_month - today).days
 
@@ -3928,25 +3929,30 @@ def _is_projected_spend_over_limit(
 def _get_projected_spend_over_limit(
     current_spend: float, soft_budget_limit: Optional[float]
 ) -> Optional[tuple]:
-    import datetime
-
     if soft_budget_limit is None:
         return None
 
-    today = datetime.date.today()
-    end_month = datetime.date(today.year, today.month + 1, 1) - datetime.timedelta(
-        days=1
-    )
+    today = date.today()
+    end_month = _get_month_end_date(today)
     remaining_days = (end_month - today).days
 
-    daily_spend = current_spend / (
-        today.day - 1
-    )  # assuming the current spend till today (not including today)
-    projected_spend = daily_spend * remaining_days
+    # assuming the current spend till today (not including today)
+    if today.day == 1:
+        daily_spend = current_spend
+    else:
+        daily_spend = current_spend / (today.day - 1)
+    projected_spend = current_spend + (daily_spend * remaining_days)
 
     if projected_spend > soft_budget_limit:
-        approx_days = soft_budget_limit / daily_spend
-        limit_exceed_date = today + datetime.timedelta(days=approx_days)
+        if daily_spend <= 0:
+            limit_exceed_date = today
+        else:
+            remaining_budget = soft_budget_limit - current_spend
+            if remaining_budget <= 0:
+                limit_exceed_date = today
+            else:
+                approx_days = remaining_budget / daily_spend
+                limit_exceed_date = today + timedelta(days=approx_days)
 
         # return the projected spend and the date it will exceeded
         return projected_spend, limit_exceed_date

tests/test_litellm/proxy/test_proxy_utils.py

@@ -1,3 +1,4 @@
+import datetime as real_datetime
 import json
 import os
 import sys
@@ -132,3 +133,48 @@ def test_join_paths_nested_path():
     """Test path joining with nested paths"""
     result = join_paths(base_path="http://0.0.0.0:4000/v1", route="chat/completions")
     assert result == "http://0.0.0.0:4000/v1/chat/completions"
+
+
+def _patch_today(monkeypatch, year, month, day):
+    class PatchedDate(real_datetime.date):
+        @classmethod
+        def today(cls):
+            return real_datetime.date(year, month, day)
+
+    monkeypatch.setattr("litellm.proxy.utils.date", PatchedDate)
+
+
+def test_get_projected_spend_over_limit_day_one(monkeypatch):
+    from litellm.proxy.utils import _get_projected_spend_over_limit
+
+    _patch_today(monkeypatch, 2026, 1, 1)
+    result = _get_projected_spend_over_limit(100.0, 1.0)
+
+    assert result is not None
+    projected_spend, projected_exceeded_date = result
+    assert projected_spend == 3100.0
+    assert projected_exceeded_date == real_datetime.date(2026, 1, 1)
+
+
+def test_get_projected_spend_over_limit_december(monkeypatch):
+    from litellm.proxy.utils import _get_projected_spend_over_limit
+
+    _patch_today(monkeypatch, 2026, 12, 15)
+    result = _get_projected_spend_over_limit(100.0, 1.0)
+
+    assert result is not None
+    projected_spend, projected_exceeded_date = result
+    assert projected_spend == pytest.approx(214.28571428571428)
+    assert projected_exceeded_date == real_datetime.date(2026, 12, 15)
+
+
+def test_get_projected_spend_over_limit_includes_current_spend(monkeypatch):
+    from litellm.proxy.utils import _get_projected_spend_over_limit
+
+    _patch_today(monkeypatch, 2026, 4, 11)
+    result = _get_projected_spend_over_limit(100.0, 200.0)
+
+    assert result is not None
+    projected_spend, projected_exceeded_date = result
+    assert projected_spend == 290.0
+    assert projected_exceeded_date == real_datetime.date(2026, 4, 21)