feat: do not move funds with call kind

contracts/contracts/gateway/GatewayMessengerFacet.sol

@@ -25,15 +25,16 @@ contract GatewayMessengerFacet is GatewayActorModifiers {
     using CrossMsgHelper for IpcEnvelope;
 
     /**
-     * @dev Sends a general-purpose cross-message from the local subnet to the destination subnet.
-     * Any value in msg.value will be forwarded in the call.
-     *
-     * IMPORTANT: Only smart contracts are allowed to trigger these cross-net messages. User wallets can send funds
-     * from their address to the destination subnet and then run the transaction in the destination normally.
-     *
-     * @param envelope - the original envelope, which will be validated, stamped and committed during the send.
-     * @return committed envelope.
-     */
+    * @dev Sends a general-purpose cross-message from the local subnet to the destination subnet.
+    * IMPORTANT: Native tokens via msg.value are treated as a contribution toward gas costs associated with message propagation.
+    * There is no strict enforcement of the exact gas cost, and any msg.value provided will be accepted.
+    *
+    * IMPORTANT: Only smart contracts are allowed to trigger these cross-net messages. User wallets can send funds
+    * from their address to the destination subnet and then run the transaction in the destination normally.
+    *
+    * @param envelope - the original envelope, which will be validated, stamped, and committed during the send.
+    * @return committed envelope.
+    */
     function sendContractXnetMessage(
         IpcEnvelope memory envelope
     ) external payable returns (IpcEnvelope memory committed) {
@@ -46,10 +47,6 @@ contract GatewayMessengerFacet is GatewayActorModifiers {
             revert InvalidXnetMessage(InvalidXnetMessageReason.Sender);
         }
 
-        if (envelope.value != msg.value) {
-            revert InvalidXnetMessage(InvalidXnetMessageReason.Value);
-        }
-
         if (envelope.kind != IpcMsgKind.Call) {
             revert InvalidXnetMessage(InvalidXnetMessageReason.Kind);
         }
@@ -61,7 +58,7 @@ contract GatewayMessengerFacet is GatewayActorModifiers {
             kind: IpcMsgKind.Call,
             from: IPCAddress({subnetId: s.networkName, rawAddress: FvmAddressHelper.from(msg.sender)}),
             to: envelope.to,
-            value: msg.value,
+            value: envelope.value,
             message: envelope.message,
             nonce: 0 // nonce will be updated by LibGateway.commitCrossMessage
         });

contracts/contracts/gateway/router/CheckpointingFacet.sol

@@ -14,7 +14,7 @@ import {NotRegisteredSubnet, SubnetNotActive, SubnetNotFound, InvalidSubnet, Che
 import {BatchNotCreated, InvalidBatchEpoch, BatchAlreadyExists, NotEnoughSubnetCircSupply, InvalidCheckpointEpoch} from "../../errors/IPCErrors.sol";
 
 import {CrossMsgHelper} from "../../lib/CrossMsgHelper.sol";
-import {IpcEnvelope, SubnetID} from "../../structs/CrossNet.sol";
+import {IpcEnvelope, SubnetID, IpcMsgKind} from "../../structs/CrossNet.sol";
 import {SubnetIDHelper} from "../../lib/SubnetIDHelper.sol";
 
 contract CheckpointingFacet is GatewayActorModifiers {
@@ -127,7 +127,9 @@ contract CheckpointingFacet is GatewayActorModifiers {
         uint256 crossMsgLength = msgs.length;
 
         for (uint256 i; i < crossMsgLength; ) {
-            totalValue += msgs[i].value;
+            if (msgs[i].kind == IpcMsgKind.Transfer) {
+                totalValue += msgs[i].value;
+            }
             unchecked {
                 ++i;
             }
@@ -138,7 +140,7 @@ contract CheckpointingFacet is GatewayActorModifiers {
         if (subnet.circSupply < totalAmount) {
             revert NotEnoughSubnetCircSupply();
         }
-
+    
         subnet.circSupply -= totalAmount;
 
         // execute cross-messages

contracts/contracts/lib/LibGateway.sol

@@ -250,7 +250,9 @@ library LibGateway {
 
         crossMessage.nonce = topDownNonce;
         subnet.topDownNonce = topDownNonce + 1;
-        subnet.circSupply += crossMessage.value;
+        if (crossMessage.kind == IpcMsgKind.Transfer) {
+            subnet.circSupply += crossMessage.value;
+        }
 
         emit NewTopDownMessage({subnet: subnet.id.getAddress(), message: crossMessage, id: crossMessage.toDeterministicHash()});
     }

contracts/contracts/structs/CrossNet.sol

@@ -73,10 +73,15 @@ struct IpcEnvelope {
     /// @dev outgoing nonce for the envelope.
     /// This nonce is set by the gateway when committing the message for propagation
     uint64 nonce;
-    /// @dev value being sent in the message.
-    /// If we want receipts to return value, and all messages to be able
-    /// to handle different supply sources we can expose the value
-    /// as a common field.
+    /// @dev Value being sent in the message.
+    /// For `Call` and `Result` kinds, the `value` field is synthetic and does not represent an actual token or native currency transfer.
+    /// Instead, it serves as metadata or an abstract representation of value to be interpreted by the target contract or receipt handler.
+    /// 
+    /// For example, in a `Call` message, `value` might represent the intended payment amount for a service in a cross-network dApp, 
+    /// allowing the receiving contract to process it as part of its logic, regardless of the actual token transfer mechanics.
+    /// Similarly, in a `Result` message, `value` might represent the outcome of a transaction, such as the total tokens minted or refunded.
+    /// 
+    /// For `Transfer` messages, `value` represents the actual amount of native tokens being transferred across networks.
     uint256 value;
     /// @dev abi.encoded message
     bytes message;

contracts/test/integration/GatewayDiamond.t.sol

@@ -538,28 +538,6 @@ contract GatewayActorDiamondTest is Test, IntegrationTestBase, SubnetWithNativeT
         gatewayDiamond.manager().kill();
     }
 
-    function testGatewayDiamond_SendCrossMessage_Fails_NoFunds() public {
-        address caller = address(new MockIpcContract());
-        vm.startPrank(caller);
-        vm.deal(caller, DEFAULT_COLLATERAL_AMOUNT + DEFAULT_CROSS_MSG_FEE + 2);
-        registerSubnet(DEFAULT_COLLATERAL_AMOUNT, caller);
-
-        SubnetID memory destinationSubnet = gatewayDiamond.getter().getNetworkName().createSubnetId(caller);
-
-        vm.expectRevert(abi.encodeWithSelector(InvalidXnetMessage.selector, InvalidXnetMessageReason.Value));
-        gatewayDiamond.messenger().sendContractXnetMessage{value: DEFAULT_CROSS_MSG_FEE}(
-            TestUtils.newXnetCallMsg(
-                IPCAddress({
-                    subnetId: SubnetID({root: ROOTNET_CHAINID, route: new address[](0)}),
-                    rawAddress: FvmAddressHelper.from(caller)
-                }),
-                IPCAddress({subnetId: destinationSubnet, rawAddress: FvmAddressHelper.from(caller)}),
-                1,
-                0
-            )
-        );
-    }
-
     function testGatewayDiamond_SendCrossMessage_Fails_Fuzz(uint256 fee) public {
         vm.assume(fee < DEFAULT_CROSS_MSG_FEE);
 
@@ -878,27 +856,6 @@ contract GatewayActorDiamondTest is Test, IntegrationTestBase, SubnetWithNativeT
         );
     }
 
-    function testGatewayDiamond_SendCrossMessage_Fails_Failes_InvalidCrossMsgValue() public {
-        address caller = address(new MockIpcContract());
-        vm.startPrank(caller);
-        vm.deal(caller, DEFAULT_COLLATERAL_AMOUNT + DEFAULT_CROSS_MSG_FEE + 2);
-        registerSubnet(DEFAULT_COLLATERAL_AMOUNT, caller);
-        SubnetID memory destinationSubnet = gatewayDiamond.getter().getNetworkName().createSubnetId(caller);
-
-        vm.expectRevert(abi.encodeWithSelector(InvalidXnetMessage.selector, InvalidXnetMessageReason.Value));
-        gatewayDiamond.messenger().sendContractXnetMessage{value: DEFAULT_CROSS_MSG_FEE}(
-            TestUtils.newXnetCallMsg(
-                IPCAddress({
-                    subnetId: SubnetID({root: ROOTNET_CHAINID, route: new address[](0)}),
-                    rawAddress: FvmAddressHelper.from(caller)
-                }),
-                IPCAddress({subnetId: destinationSubnet, rawAddress: FvmAddressHelper.from(caller)}),
-                5,
-                0
-            )
-        );
-    }
-
     // TODO: this is no longer possible because EOA cannot be subnet
     // function testGatewayDiamond_SendCrossMessage_Fails_EoACaller() public {
     //     address caller = vm.addr(100);
@@ -1215,7 +1172,8 @@ contract GatewayActorDiamondTest is Test, IntegrationTestBase, SubnetWithNativeT
         gatewayDiamond.checkpointer().commitCheckpoint(checkpoint);
 
         (, subnetInfo) = gatewayDiamond.getter().getSubnet(subnetId);
-        require(subnetInfo.circSupply == DEFAULT_COLLATERAL_AMOUNT - 10 * amount, "unexpected circulating supply");
+        // cross net messages with Call kind does not affect the circulating supply
+        require(subnetInfo.circSupply == DEFAULT_COLLATERAL_AMOUNT, "unexpected circulating supply");
     }
 
     function testGatewayDiamond_listIncompleteCheckpoints() public {