fix(proxy): anchor the tool spend clamp floor to UTC midnight

With end_date omitted the floor was end-anchored to now including its
time-of-day, so an explicit start_date exactly 30 days back parsed as
midnight, compared below the floor, and was invisibly clamped to a
mid-day instant: up to a day of spend disappeared while the response
start_date still printed the full calendar date. Anchoring the floor to
today's UTC midnight makes every comparison in the window derivation
date-pure.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

litellm/proxy/management_endpoints/tool_management_endpoints.py

@@ -232,7 +232,11 @@ async def get_tool_spend(
 
     now = datetime.now(timezone.utc)
     end_day = _parse_day_start(end_date)
-    window_floor = (end_day or now) - timedelta(days=TOOL_SPEND_MAX_WINDOW_DAYS)
+    # Anchor the floor to a midnight so the clamp compares dates with dates:
+    # parsed start_dates are midnight-aligned, and a floor carrying now's
+    # time-of-day would invisibly truncate an explicit start_date to mid-day.
+    today = now.replace(hour=0, minute=0, second=0, microsecond=0)
+    window_floor = (end_day or today) - timedelta(days=TOOL_SPEND_MAX_WINDOW_DAYS)
     start_dt = _parse_day_start(start_date) or window_floor
     if start_dt < window_floor:
         start_dt = window_floor

tests/test_litellm/proxy/management_endpoints/test_tool_management_endpoints.py

@@ -9,7 +9,7 @@ imports these inside function bodies to avoid circular imports.
 
 import os
 import sys
-from datetime import datetime, timezone
+from datetime import datetime, timedelta, timezone
 from typing import Optional
 from unittest.mock import AsyncMock, MagicMock, patch
 
@@ -232,6 +232,31 @@ class TestToolManagementEndpoints:
             assert call.args[1] == datetime(2026, 6, 25, tzinfo=timezone.utc).isoformat()
         assert resp.json()["start_date"] == "2026-06-25"
 
+    def test_tool_spend_start_honored_when_end_date_omitted(self):
+        # Regression: with end_date omitted the floor anchors to today's UTC
+        # midnight, not now's time-of-day, so an explicit start_date exactly 30
+        # days back is served from midnight rather than truncated to mid-day.
+        prisma = MagicMock()
+        prisma.db.query_raw = AsyncMock(return_value=[])
+        floor_day = datetime.now(timezone.utc).replace(hour=0, minute=0, second=0, microsecond=0) - timedelta(days=30)
+        with patch("litellm.proxy.proxy_server.prisma_client", prisma):
+            resp = self.client.get(f"/v1/tool/spend?start_date={floor_day.strftime('%Y-%m-%d')}")
+        assert resp.status_code == 200
+        for call in prisma.db.query_raw.await_args_list:
+            assert call.args[1] == floor_day.isoformat()
+        assert resp.json()["start_date"] == floor_day.strftime("%Y-%m-%d")
+
+    def test_tool_spend_clamp_without_end_date_lands_on_midnight(self):
+        prisma = MagicMock()
+        prisma.db.query_raw = AsyncMock(return_value=[])
+        floor_day = datetime.now(timezone.utc).replace(hour=0, minute=0, second=0, microsecond=0) - timedelta(days=30)
+        with patch("litellm.proxy.proxy_server.prisma_client", prisma):
+            resp = self.client.get("/v1/tool/spend?start_date=2020-01-01")
+        assert resp.status_code == 200
+        for call in prisma.db.query_raw.await_args_list:
+            assert call.args[1] == floor_day.isoformat()
+        assert resp.json()["start_date"] == floor_day.strftime("%Y-%m-%d")
+
     def test_tool_spend_total_query_bounds_outer_spendlogs_scan(self):
         prisma = MagicMock()
         prisma.db.query_raw = AsyncMock(return_value=[])