Prefer open direction from ATM vs spot (below=Call/short, above=Put/long).

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

backend/tests/test_p1_p2_rules.py

@@ -28,6 +28,31 @@ def test_signal_equal() -> None:
     assert decide(10.0, 10.0) is None
 
 
+def test_signal_strike_below_spot_call_short() -> None:
+    # 现价 1859、ATM 1850：即使 Put 卖一更高，也走 Call+空
+    s = decide(10.0, 20.0, strike=1850, mark_px=1859)
+    assert s is not None
+    assert s.option_side == "call"
+    assert s.perp_side == "short"
+    assert s.bias == "strike_below_spot"
+
+
+def test_signal_strike_above_spot_put_long() -> None:
+    # 现价 1859、ATM 1875：即使 Call 卖一更高，也走 Put+多
+    s = decide(20.0, 10.0, strike=1875, mark_px=1859)
+    assert s is not None
+    assert s.option_side == "put"
+    assert s.perp_side == "long"
+    assert s.bias == "strike_above_spot"
+
+
+def test_signal_strike_flat_falls_back_to_ask() -> None:
+    s = decide(20.0, 15.0, strike=1860, mark_px=1860)
+    assert s is not None
+    assert s.bias == "call_ask_gt_put"
+    assert s.option_side == "call"
+
+
 def test_exit_fixed_and_premium_multiple() -> None:
     fixed = check_exits(
         net_pnl=15.0,