diff --git a/tests/test_incumbent_routing.py b/tests/test_incumbent_routing.py
index 8057368..bf03738 100644
--- a/tests/test_incumbent_routing.py
+++ b/tests/test_incumbent_routing.py
@@ -12,6 +12,7 @@ The database tests use the same offline temp-DB pattern as
 
 import sqlite3
 import tempfile
+from datetime import datetime, timezone
 from pathlib import Path
 
 import pytest
@@ -469,16 +470,21 @@ def _seed_measured_cache_rate(conn, provider, model_id,
 
     objective.incumbent_rate_min_observations defaults to 25, so we seed
     enough rows to clear the floor.
+
+    Rows are stamped "now", not a fixed date: _measured_cache_rates only reads
+    rows inside objective.cache_rate_window_hours (168), so a literal date
+    ages out of the window and the incumbent silently falls back to the
+    assumed rate. That is how this fixture started failing on 2026-09-20.
     """
+    observed_at = datetime.now(timezone.utc).isoformat()
     for _ in range(observations):
         conn.execute(
             """INSERT INTO energy_observations (
                 model_id, provider, task_category,
                 prompt_tokens, completion_tokens, cached_prompt_tokens,
                 cached_tokens_source, observed_at
-            ) VALUES (?, ?, 'general', ?, 500, ?, 'reported',
-                      '2026-09-13T00:00:00+00:00')""",
-            (model_id, provider, prompt_tokens, cached_tokens),
+            ) VALUES (?, ?, 'general', ?, 500, ?, 'reported', ?)""",
+            (model_id, provider, prompt_tokens, cached_tokens, observed_at),
         )
     conn.commit()