Cap options budget-full sizing at min(balance, trade budget) with UI hint.

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

lib/options/options_register.py

@@ -163,13 +163,18 @@ def _require_options_ex(cfg: dict[str, Any]):
 
 
 def _budget_full_usdc(cfg: dict[str, Any], ex: Any) -> tuple[float | None, str]:
-    """交易账户 USDC 可用余额(由 calc_order_size 再乘 budget_buffer 留余量)."""
+    """打满可用额度 = min(交易户可用 USDC, 单笔预算);calc_order_size 再乘 budget_buffer."""
     from lib.exchange.okx_options_lib import fetch_options_trading_usdc
+    from lib.options.options_pricing_lib import resolve_budget_full_usdc
 
     raw = fetch_options_trading_usdc(ex)
     if raw is None or float(raw) <= 0:
         return None, "交易账户 USDC 可用余额不足"
-    return float(raw), ""
+    trading = float(raw)
+    cap = _env_float("OKX_OPTIONS_TRADE_BUDGET_USDC", float(cfg.get("trade_budget") or 10.0))
+    if cap <= 0:
+        return None, "单笔预算无效(OKX_OPTIONS_TRADE_BUDGET_USDC)"
+    return resolve_budget_full_usdc(trading, float(cap)), ""
 
 
 def _open_premium_paid(cfg: dict[str, Any], inst_id: str) -> float | None: