diff --git a/src/core/order-coordinator.ts b/src/core/order-coordinator.ts
index aa8b37e..9b0ddbd 100644
--- a/src/core/order-coordinator.ts
+++ b/src/core/order-coordinator.ts
@@ -253,8 +253,7 @@ export async function placeStopLossOrder(
     quantity,
     triggerType: "STOP_LOSS",
   };
-  // 部分交易所（例如 Paradex）要求 STOP_MARKET 同时提供 price 字段
-  params.price = params.stopPrice;
+  // Avoid forcing price for STOP_MARKET globally; keep this exchange-specific in gateways
   await deduplicateOrders(adapter, symbol, openOrders, locks, timers, pendings, type, side, log);
   lockOperating(locks, timers, pendings, type, log);
   try {
@@ -296,7 +295,9 @@ export async function placeTrailingStopOrder(
     symbol,
     side,
     type,
-    quantity: roundQtyDownToStep(quantity, qtyStep),
+    // Do not round down trailing-stop quantity to avoid underflowing small positions to zero;
+    // let the exchange adapter handle precise quantization.
+    quantity,
     reduceOnly: "true",
     activationPrice: roundDownToTick(activationPrice, priceTick),
     callbackRate,
diff --git a/src/exchanges/aster/client.ts b/src/exchanges/aster/client.ts
index 71d3204..b4c172b 100644
--- a/src/exchanges/aster/client.ts
+++ b/src/exchanges/aster/client.ts
@@ -778,7 +778,28 @@ export class AsterRestClient {
   }
 
   async createOrder(params: CreateOrderParams): Promise<AsterOrder> {
-    const payload: Record<string, unknown> = { ...params };
+    // Sanitize and normalize params for Aster futures API. Paradex-specific flags
+    // like reduceOnly/closePosition on STOP/TRAILING should not leak here.
+    const payload: Record<string, unknown> = {};
+    payload.symbol = String(params.symbol).toUpperCase();
+    payload.side = params.side;
+    payload.type = params.type;
+    if (params.timeInForce !== undefined) payload.timeInForce = params.timeInForce;
+    if (params.price !== undefined) payload.price = params.price;
+    if (params.stopPrice !== undefined) payload.stopPrice = params.stopPrice;
+    if (params.activationPrice !== undefined) payload.activationPrice = params.activationPrice;
+    if (params.callbackRate !== undefined) payload.callbackRate = params.callbackRate;
+    if (params.quantity !== undefined) payload.quantity = Math.abs(params.quantity);
+
+    // Aster rejects reduceOnly/closePosition for certain order types (e.g. STOP/TRAILING).
+    // Keep the behavior exchange-specific by stripping them here for Aster.
+    const type = String(params.type).toUpperCase();
+    const isStopOrTrailing = type === "STOP_MARKET" || type === "TRAILING_STOP_MARKET";
+    if (!isStopOrTrailing) {
+      if (params.reduceOnly !== undefined) payload.reduceOnly = params.reduceOnly;
+      if (params.closePosition !== undefined) payload.closePosition = params.closePosition;
+    }
+
     const response = await this.signedRequest<any>({ path: "/fapi/v1/order", method: "POST", params: payload });
     return toOrderFromRest(response);
   }