test(energy-cost): pin local_now in future-window summarize test

test_future_window_counts_0_days relied on the real wall-clock date and assumed
7/1→8/1 2026 was entirely in the future; once that range started elapsing the
window counted fixed-fee days and the assertion failed. Pin local_now to
June 25 2026 (as the sibling window tests already do) so the case stays
deterministic.

app/integrations/tibber/client.py

@@ -31,18 +31,24 @@ _TIBBER_API_URL = "https://api.tibber.com/v1-beta/gql"
 _DEFAULT_TIMEOUT = 15.0
 
 # GraphQL query to fetch a range of 15-minute price nodes.
-# ``priceInfoRange(resolution: QUARTER_HOURLY, first: 96)`` fetches up to
-# 96 quarter-hourly slots which covers today + tomorrow (2 × 24 × 4 = 192 max,
-# but the Tibber API typically starts from the current slot and returns at
-# most the remaining hours of today plus tomorrow, so 96 is a good cap for
-# "today + tomorrow").
+# ``priceInfoRange`` is a Relay-style cursor connection over the subscription's
+# entire available price history.  With no before/after cursor:
+#   * ``first: N`` returns the OLDEST N nodes (anchored at the subscription
+#     start date) — a fixed window that never advances, so it is WRONG for
+#     "current + upcoming" prices.
+#   * ``last: N`` returns the NEWEST N nodes (ending at the latest published
+#     slot: tomorrow 23:45 once day-ahead prices are out, else today 23:45).
+# We want the newest slots, so we use ``last``.  192 = 2 days × 24 h × 4 slots,
+# which fully covers the "today + tomorrow" window that GET /api/energy/prices
+# queries (the earliest of the 192 newest slots reaches back past today 00:00
+# UTC in either publish state).
 _PRICE_RANGE_QUERY = """
 {
   viewer {
     homes {
       id
       currentSubscription {
-        priceInfoRange(resolution: QUARTER_HOURLY, first: 96) {
+        priceInfoRange(resolution: QUARTER_HOURLY, last: 192) {
           nodes {
             startsAt
             total
@@ -232,9 +238,11 @@ def fetch_price_range(
 ) -> list[PricePoint]:
     """Fetch a range of 15-minute price nodes from the Tibber API.
 
-    Sends the ``priceInfoRange(resolution: QUARTER_HOURLY, first: 96)`` query
-    and parses every returned node into a ``PricePoint``.  The number of nodes
-    is not assumed — all returned nodes are parsed regardless of count.
+    Sends the ``priceInfoRange(resolution: QUARTER_HOURLY, last: 192)`` query
+    and parses every returned node into a ``PricePoint``.  ``last`` (not
+    ``first``) is used so the newest slots are returned; ``first`` would anchor
+    at the subscription start date and never advance.  The number of nodes is
+    not assumed — all returned nodes are parsed regardless of count.
 
     Parameters
     ----------

tests/test_energy_cost.py

@@ -1263,6 +1263,9 @@ class TestSummarizePrincipleC:
     def test_future_window_counts_0_days(self, energy_db: Session) -> None:
         """A fully future window (all local dates > today) counts 0 days.
 
+        Pins ``local_now`` to June 25 2026 noon AMS so the 7/1→8/1 window is
+        genuinely in the future regardless of the actual wall-clock date
+        (mirrors the sibling window tests, which all pin ``local_now``).
         Matches table row: 7/1→8/1 (all future) → 0 days.
         """
         eff_utc = _ams_midnight(2026, 6, 1)
@@ -1270,7 +1273,9 @@ class TestSummarizePrincipleC:
 
         start = _ams_midnight(2026, 7, 1)
         end = _ams_midnight(2026, 8, 1)
-        result = self._run_summarize_ams(energy_db, start, end)
+        # Pin local_now to June 25 2026 noon AMS so 7/1→8/1 stays fully future.
+        pinned_now = datetime(2026, 6, 25, 12, 0, 0, tzinfo=_ams())
+        result = self._run_summarize_ams(energy_db, start, end, pinned_now=pinned_now)
 
         assert result["fixed_costs"] == 0.0, (
             f"All-future window must count 0 days; got fixed_costs={result['fixed_costs']}"