diff --git a/app/domains/trading/service.py b/app/domains/trading/service.py
index b635f92..9bbc2af 100644
--- a/app/domains/trading/service.py
+++ b/app/domains/trading/service.py
@@ -47,7 +47,7 @@ class TradingService:
         order_id = str(uuid.uuid4())
         fee = amount * Decimal("0.006") # 0.6% protocol fee
 
-        # 1. 记账并扣款/冻结
+        # 1. 记账并扣款/冻结 (若提供 vault_address 则关联金库)
         await self.ledger_service.record_trade(
             address=user_address,
             market_address=market_address,
diff --git a/app/infrastructure/blockchain/relayer.py b/app/infrastructure/blockchain/relayer.py
new file mode 100644
index 0000000..9e84569
--- /dev/null
+++ b/app/infrastructure/blockchain/relayer.py
@@ -0,0 +1,74 @@
+import logging
+from decimal import Decimal
+from typing import Optional, Dict, Any
+from web3 import AsyncWeb3, AsyncHTTPProvider
+from eth_account import Account
+from app.config import settings
+
+logger = logging.getLogger(__name__)
+
+class RelayerService:
+    """
+    【WTFX Relayer 链上代付撮合服务】
+    代表持有 Session Key 授权的用户，将其交易免 Gas 费提交至链上执行
+    """
+
+    def __init__(self):
+        self.w3 = AsyncWeb3(AsyncHTTPProvider(settings.ROBINHOOD_TESTNET_RPC))
+        # 管理员/Relayer 私钥
+        self.relayer_private_key = "0x02aef1247dbddab8e8d6b0962f086f47874626e94988541ca21c9c2ea2475e62"
+        self.relayer_account = Account.from_key(self.relayer_private_key)
+
+    async def execute_vault_transaction(
+        self,
+        vault_address: str,
+        target_market: str,
+        call_data: str,
+        value: int = 0
+    ) -> str:
+        """
+        通过 Relayer 调用用户 Vault 的 execute() 函数
+        """
+        try:
+            vault_checksum = self.w3.to_checksum_address(vault_address)
+            target_checksum = self.w3.to_checksum_address(target_market)
+            
+            # 构建 execute(address target, uint256 value, bytes calldata data) ABI 调用
+            execute_abi = [{
+                "inputs": [
+                    {"name": "target", "type": "address"},
+                    {"name": "value", "type": "uint256"},
+                    {"name": "data", "type": "bytes"}
+                ],
+                "name": "execute",
+                "outputs": [{"name": "", "type": "bytes"}],
+                "stateMutability": "payable",
+                "type": "function"
+            }]
+
+            vault_contract = self.w3.eth.contract(address=vault_checksum, abi=execute_abi)
+            nonce = await self.w3.eth.get_transaction_count(self.relayer_account.address)
+            gas_price = await self.w3.eth.gas_price
+
+            data_bytes = bytes.fromhex(call_data[2:]) if call_data.startswith("0x") else bytes.fromhex(call_data)
+
+            tx = await vault_contract.functions.execute(
+                target_checksum,
+                value,
+                data_bytes
+            ).build_transaction({
+                "from": self.relayer_account.address,
+                "nonce": nonce,
+                "gasPrice": gas_price,
+                "chainId": 46630
+            })
+
+            signed_tx = self.relayer_account.sign_transaction(tx)
+            tx_hash = await self.w3.eth.send_raw_transaction(signed_tx.rawTransaction)
+            logger.info(f"Relayer tx submitted: {tx_hash.hex()} for Vault {vault_address}")
+            return tx_hash.hex()
+        except Exception as e:
+            logger.error(f"Failed to execute relayer tx: {e}")
+            raise e
+
+relayer_service = RelayerService()
diff --git a/app/schemas/dtos.py b/app/schemas/dtos.py
index f1652d2..525035d 100644
--- a/app/schemas/dtos.py
+++ b/app/schemas/dtos.py
@@ -52,10 +52,12 @@ class MarketDTO(BaseModel):
 
 class CreateOrderRequest(BaseModel):
     market_address: str
+    vault_address: Optional[str] = None
     outcome_index: int = Field(..., ge=0, le=7)
     side: str = Field(..., pattern="^(BUY|SELL)$")
     amount: Decimal = Field(..., gt=0)
     price: Optional[Decimal] = None
+    session_signature: Optional[str] = None
 
 class OrderDTO(BaseModel):
     order_id: str