diff --git a/src/TheCompact.sol b/src/TheCompact.sol
index 361c582..9d33709 100644
--- a/src/TheCompact.sol
+++ b/src/TheCompact.sol
@@ -795,13 +795,15 @@ contract TheCompact is ITheCompact, ERC6909, Extsload {
 
         unchecked {
             uint256 totalIds = transfer.transfers.length;
+            uint256 id;
             for (uint256 i = 0; i < totalIds; ++i) {
                 SplitByIdComponent calldata component = transfer.transfers[i];
+                id = component.id;
                 SplitComponent[] calldata portions = component.portions;
                 uint256 totalPortions = portions.length;
                 for (uint256 j = 0; j < totalPortions; ++j) {
                     SplitComponent calldata portion = portions[j];
-                    operation(msg.sender, portion.claimant, component.id, portion.amount);
+                    operation(msg.sender, portion.claimant, id, portion.amount);
                 }
             }
         }
@@ -902,7 +904,7 @@ contract TheCompact is ITheCompact, ERC6909, Extsload {
             sponsorSignature.offset := add(0x20, sponsorSignaturePtr)
             sponsorSignature.length := calldataload(sponsorSignaturePtr)
 
-            sponsor := calldataload(add(calldataPointer, 0x40)) // TODO: sanitize
+            sponsor := shr(96, shl(96, calldataload(add(calldataPointer, 0x40))))
             nonce := calldataload(add(calldataPointer, 0x60))
             expires := calldataload(add(calldataPointer, 0x80))
         }
@@ -969,7 +971,7 @@ contract TheCompact is ITheCompact, ERC6909, Extsload {
             let calldataPointerWithOffset := add(calldataPointer, offsetToId)
             id := calldataload(calldataPointerWithOffset)
             allocatedAmount := calldataload(add(calldataPointerWithOffset, 0x20))
-            claimant := calldataload(add(calldataPointerWithOffset, 0x40)) // TODO: sanitize
+            claimant := shr(96, shl(96, calldataload(add(calldataPointerWithOffset, 0x40))))
             amount := calldataload(add(calldataPointerWithOffset, 0x60))
         }
 
diff --git a/src/lib/HashLib.sol b/src/lib/HashLib.sol
index 88857f2..bc82821 100644
--- a/src/lib/HashLib.sol
+++ b/src/lib/HashLib.sol
@@ -98,7 +98,6 @@ import { Scope } from "../types/Scope.sol";
 import { FunctionCastLib } from "./FunctionCastLib.sol";
 import { EfficiencyLib } from "./EfficiencyLib.sol";
 
-// TODO: make calldata versions of these where useful
 library HashLib {
     using EfficiencyLib for bool;
     using FunctionCastLib for function(BatchTransfer calldata, bytes32) internal view returns (bytes32);
@@ -135,13 +134,29 @@ library HashLib {
     }
 
     function toMessageHash(SplitTransfer calldata transfer) internal view returns (bytes32 messageHash) {
-        // TODO: optimize this part (but remember to watch out for an amount overflow)
         uint256 amount = 0;
-        for (uint256 i = 0; i < transfer.recipients.length; ++i) {
-            amount += transfer.recipients[i].amount;
+        uint256 currentAmount;
+
+        SplitComponent[] calldata recipients = transfer.recipients;
+        uint256 totalRecipients = recipients.length;
+        uint256 errorBuffer;
+
+        unchecked {
+            for (uint256 i = 0; i < totalRecipients; ++i) {
+                currentAmount = recipients[i].amount;
+                amount += currentAmount;
+                errorBuffer |= (amount < currentAmount).asUint256();
+            }
         }
 
         assembly ("memory-safe") {
+            if errorBuffer {
+                // Revert Panic(0x11) (arithmetic overflow)
+                mstore(0, 0x4e487b71)
+                mstore(0x20, 0x11)
+                revert(0x1c, 0x24)
+            }
+
             let m := mload(0x40) // Grab the free memory pointer; memory will be left dirtied.
 
             mstore(m, COMPACT_TYPEHASH)
@@ -274,7 +289,6 @@ library HashLib {
     }
 
     function toMessageHash(SplitBatchTransfer calldata transfer) internal view returns (bytes32 messageHash) {
-        // TODO: make this more efficient especially once using calldata
         SplitByIdComponent[] calldata transfers = transfer.transfers;
         uint256 totalIds = transfers.length;
 
@@ -913,7 +927,7 @@ library HashLib {
             let additionalChainsData := add(0x20, additionalChainsPtr)
             let chainIndex := shl(5, calldataload(add(claimWithAdditionalOffset, 0xc0)))
 
-            // TODO: rather than using extraOffset, consider breaking into two distinct
+            // NOTE: rather than using extraOffset, consider breaking into two distinct
             // loops or potentially even two calldatacopy operations based on chainIndex
             let extraOffset := 0
             for { let i := 0 } lt(i, additionalChainsLength) { i := add(i, 0x20) } {