fix: align OHLCV fetch window with limit so chart seeds past 30 bars

Co-authored-by: Cursor <cursoragent@cursor.com>

tests/test_hub_kline_store.py

@@ -7,6 +7,8 @@ import unittest
 from pathlib import Path
 
 from hub_kline_store import (
+    HUB_KLINE_REMOTE_FETCH_CAP,
+    _since_ms_for_span,
     clear_series_bars,
     init_db,
     load_bars_before,
@@ -391,6 +393,55 @@ class TestHubKlineStore(unittest.TestCase):
         self.assertGreater(int(out.get("fetched") or 0), 0)
         self.assertGreaterEqual(len(out.get("candles") or []), 19)
 
+    def test_since_span_matches_fetch_limit_not_need(self):
+        period = TIMEFRAME_MS["15m"]
+        now_ms = 1_800_000_000_000
+        fetch_limit = HUB_KLINE_REMOTE_FETCH_CAP
+        since = _since_ms_for_span(
+            now_ms=now_ms,
+            period_ms=period,
+            span_bars=fetch_limit,
+            cutoff_ms=0,
+        )
+        self.assertEqual(since, now_ms - period * fetch_limit)
+        wrong_since = now_ms - period * chart_initial_limit("15m")
+        self.assertGreater(since, wrong_since)
+
+    def test_thin_series_tail_refresh_fetches_full_window(self):
+        init_db(self.db)
+        period = TIMEFRAME_MS["15m"]
+        now = int(time.time() * 1000)
+        last_closed = last_closed_bar_open_ms("15m", now)
+        bars = [
+            {
+                "open_time_ms": last_closed - period * (150 - i),
+                "open": 100000,
+                "high": 100100,
+                "low": 99900,
+                "close": 100050,
+                "volume": 1,
+            }
+            for i in range(150)
+        ]
+        fetch_calls: list[dict] = []
+
+        def remote_fetch(**kwargs):
+            fetch_calls.append(dict(kwargs))
+            return {"ok": True, "bars": bars, "price_tick": 0.01}
+
+        out = resolve_chart_bars(
+            "binance",
+            "BTC/USDT",
+            "15m",
+            remote_fetch,
+            db_path=self.db,
+            tail_refresh=True,
+        )
+        self.assertTrue(out.get("ok"))
+        self.assertGreaterEqual(len(out.get("candles") or []), 100)
+        self.assertGreater(int(out.get("fetched") or 0), 0)
+        self.assertTrue(any(int(c.get("limit") or 0) > 30 for c in fetch_calls))
+
     def test_resolve_before_ms_exhausted(self):
         init_db(self.db)