diff --git a/.gas-snapshot b/.gas-snapshot
index 7a9ed51a..da42540a 100644
--- a/.gas-snapshot
+++ b/.gas-snapshot
@@ -32,7 +32,7 @@ DeploymentTest:test_deploy_susd_proxy_zero_address() (gas: 42915)
 Deposit:test_depositEth() (gas: 55221)
 Deposit:test_depositEth_Account_Doesnt_Exist() (gas: 34292)
 Deposit:test_depositEth_event() (gas: 56837)
-Deposit:test_depositEth_fuzz(uint256,uint128) (runs: 256, μ: 36432, ~: 34844)
+Deposit:test_depositEth_fuzz(uint256,uint128) (runs: 256, μ: 36624, ~: 34844)
 DepositCollateral:test_depositCollateral() (gas: 258418)
 DepositCollateral:test_depositCollateral_availableMargin() (gas: 265986)
 DepositCollateral:test_depositCollateral_collateralAmount() (gas: 258994)
@@ -49,10 +49,8 @@ Execute:test_execute_order_committed() (gas: 430886)
 Fee:test_fee_exceeds_account_credit() (gas: 67971)
 Fee:test_fee_exceeds_maxExecutorFee() (gas: 67506)
 Fee:test_fee_imposed() (gas: 469073)
-MathLibTest:test_abs128() (gas: 448)
+MathLibTest:test_abs128() (gas: 425)
 MathLibTest:test_abs256() (gas: 480)
-MathLibTest:test_castU128() (gas: 350)
-MathLibTest:test_castU128_overflow() (gas: 3509)
 MathLibTest:test_fuzz_abs128(int128) (runs: 256, μ: 577, ~: 603)
 MathLibTest:test_fuzz_abs256(int256) (runs: 256, μ: 472, ~: 458)
 MathLibTest:test_isSameSign() (gas: 999)
diff --git a/lcov.info b/lcov.info
index d1afcd9b..f52b2671 100644
--- a/lcov.info
+++ b/lcov.info
@@ -1,44 +1,44 @@
 TN:
 SF:script/Deploy.s.sol
-FN:43,DeployBase_Synthetix.run
-FNDA:0,DeployBase_Synthetix.run
-DA:44,0
-DA:45,0
-DA:47,0
-DA:54,0
+FN:24,Setup.deploySystem
+FNDA:5,Setup.deploySystem
+DA:30,5
 FN:62,DeployBaseGoerli_Synthetix.run
 FNDA:0,DeployBaseGoerli_Synthetix.run
 DA:63,0
 DA:64,0
 DA:66,0
 DA:73,0
-FN:122,DeployOptimism_Synthetix.run
-FNDA:0,DeployOptimism_Synthetix.run
-DA:123,0
-DA:124,0
-DA:126,0
-DA:133,0
+FN:43,DeployBase_Synthetix.run
+FNDA:0,DeployBase_Synthetix.run
+DA:44,0
+DA:45,0
+DA:47,0
+DA:54,0
+FN:141,DeployOptimismGoerli_Synthetix.run
+FNDA:0,DeployOptimismGoerli_Synthetix.run
+DA:142,0
+DA:143,0
+DA:145,0
+DA:152,0
 FN:103,DeployBaseGoerli_Andromeda.run
 FNDA:0,DeployBaseGoerli_Andromeda.run
 DA:104,0
 DA:105,0
 DA:107,0
 DA:114,0
-FN:24,Setup.deploySystem
-FNDA:5,Setup.deploySystem
-DA:30,5
 FN:84,DeployBaseGoerli_KwentaFork.run
 FNDA:0,DeployBaseGoerli_KwentaFork.run
 DA:85,0
 DA:86,0
 DA:88,0
 DA:95,0
-FN:141,DeployOptimismGoerli_Synthetix.run
-FNDA:0,DeployOptimismGoerli_Synthetix.run
-DA:142,0
-DA:143,0
-DA:145,0
-DA:152,0
+FN:122,DeployOptimism_Synthetix.run
+FNDA:0,DeployOptimism_Synthetix.run
+DA:123,0
+DA:124,0
+DA:126,0
+DA:133,0
 FNF:7
 FNH:1
 LF:25
@@ -62,11 +62,11 @@ DA:149,284
 FN:159,Engine.depositEth
 FNDA:523,Engine.depositEth
 DA:162,523
-BRDA:162,0,0,236
-BRDA:162,0,1,287
-DA:163,236
-DA:166,287
-DA:168,287
+BRDA:162,0,0,232
+BRDA:162,0,1,291
+DA:163,232
+DA:166,291
+DA:168,291
 FN:172,Engine.withdrawEth
 FNDA:261,Engine.withdrawEth
 DA:176,261
@@ -295,24 +295,17 @@ DA:23,0
 FN:30,MathLib.abs256
 FNDA:0,MathLib.abs256
 DA:44,0
-FN:52,MathLib.castU128
-FNDA:0,MathLib.castU128
-DA:53,0
-BRDA:53,0,0,-
-BRDA:53,0,1,-
-DA:54,0
-DA:56,0
-FN:64,MathLib.isSameSign
+FN:53,MathLib.isSameSign
 FNDA:0,MathLib.isSameSign
-DA:65,0
-BRDA:65,1,0,-
-BRDA:65,1,1,-
-DA:66,0
-FNF:4
+DA:54,0
+BRDA:54,0,0,-
+BRDA:54,0,1,-
+DA:55,0
+FNF:3
 FNH:0
-LF:7
+LF:4
 LH:0
-BRF:4
+BRF:2
 BRH:0
 end_of_record
 TN:
@@ -518,11 +511,6 @@ FNDA:0,BootstrapOptimism.init
 DA:108,0
 DA:115,0
 DA:122,0
-FN:134,BootstrapOptimismGoerli.init
-FNDA:0,BootstrapOptimismGoerli.init
-DA:138,0
-DA:145,0
-DA:152,0
 FN:38,Bootstrap.initializeOptimismGoerli
 FNDA:0,Bootstrap.initializeOptimismGoerli
 DA:39,0
@@ -559,6 +547,11 @@ DA:91,0
 DA:92,0
 DA:97,0
 DA:99,0
+FN:134,BootstrapOptimismGoerli.init
+FNDA:0,BootstrapOptimismGoerli.init
+DA:138,0
+DA:145,0
+DA:152,0
 FNF:4
 FNH:0
 LF:38
@@ -656,11 +649,11 @@ DA:10,256
 DA:11,256
 BRDA:11,0,0,256
 BRDA:11,0,1,-
+FN:5,EIP7412Mock.fulfillOracleQuery
+FNDA:256,EIP7412Mock.fulfillOracleQuery
 FN:16,EIP7412MockRevert.fulfillOracleQuery
 FNDA:256,EIP7412MockRevert.fulfillOracleQuery
 DA:17,256
-FN:5,EIP7412Mock.fulfillOracleQuery
-FNDA:256,EIP7412Mock.fulfillOracleQuery
 FNF:3
 FNH:3
 LF:3
diff --git a/src/Engine.sol b/src/Engine.sol
index 599f8816..cac67535 100644
--- a/src/Engine.sol
+++ b/src/Engine.sol
@@ -263,7 +263,7 @@ contract Engine is IEngine, EIP712, EIP7412 {
     {
         // shift _nonce to the right by 8 bits and cast to uint248
         /// @dev wordPos == 0 if 0 <= _nonce <= 255, 1 if 256 <= _nonce <= 511, etc.
-        wordPos = uint248(_nonce >> 8);
+        wordPos = _nonce >> 8;
 
         // cast the last 8 bits of _nonce to uint8
         /// @dev 0 <= bitPos <= 255
@@ -391,7 +391,7 @@ contract Engine is IEngine, EIP712, EIP7412 {
         override
         returns (IPerpsMarketProxy.Data memory retOrder, uint256 fees)
     {
-        /// @dev only the account owner can withdraw collateral
+        /// @dev the account owner or the delegate may commit async orders
         if (_isAccountOwnerOrDelegate(_accountId, msg.sender)) {
             (retOrder, fees) = _commitOrder({
                 _perpsMarketId: _perpsMarketId,
@@ -497,7 +497,7 @@ contract Engine is IEngine, EIP712, EIP7412 {
             }
         }
 
-        /// @dev execute the order
+        /// @dev commit async order
         (retOrder, synthetixFees) = _commitOrder({
             _perpsMarketId: _co.orderDetails.marketId,
             _accountId: _co.orderDetails.accountId,
diff --git a/src/interfaces/IEngine.sol b/src/interfaces/IEngine.sol
index 98608098..b2fed3e4 100644
--- a/src/interfaces/IEngine.sol
+++ b/src/interfaces/IEngine.sol
@@ -36,7 +36,7 @@ interface IEngine {
         OrderDetails orderDetails;
         // address of the signer of the order
         address signer;
-        // an incrementing value indexed per order
+        // a means to prevent replay attacks and identify the order
         uint256 nonce;
         // option to require all extra conditions to be verified on-chain
         bool requireVerified;
diff --git a/src/libraries/MathLib.sol b/src/libraries/MathLib.sol
index fb634509..3a67ee2b 100644
--- a/src/libraries/MathLib.sol
+++ b/src/libraries/MathLib.sol
@@ -45,17 +45,6 @@ library MathLib {
         }
     }
 
-    /// @notice cast uint256 to uint128
-    /// @dev asserts that input is not greater than uint128 max
-    /// @param x unsigned 256-bit number
-    /// @return downcasted uint128 from uint256
-    function castU128(uint256 x) internal pure returns (uint128) {
-        if (x > type(uint128).max) {
-            revert OverflowU128();
-        }
-        return uint128(x);
-    }
-
     /// @notice determines if input numbers have the same sign
     /// @dev asserts that both numbers are not zero
     /// @param x signed number
diff --git a/test/MathLib.t.sol b/test/MathLib.t.sol
index 92cec7b8..14e2f8cc 100644
--- a/test/MathLib.t.sol
+++ b/test/MathLib.t.sol
@@ -78,21 +78,6 @@ contract MathLibTest is Test {
         }
     }
 
-    function test_castU128() public {
-        uint256 x = 1 ether;
-        uint128 z = x.castU128();
-        assertEq(z, 1 ether);
-    }
-
-    function test_castU128_overflow() public {
-        uint256 x = type(uint128).max;
-        x++;
-
-        vm.expectRevert(abi.encodeWithSelector(MathLib.OverflowU128.selector));
-
-        x.castU128();
-    }
-
     function test_isSameSign() public {
         int128 x = -1;
         int128 y = -1;