diff --git a/packages/contracts-communication/configs/global/ExecutionService.testnet.json b/packages/contracts-communication/configs/global/ExecutionService.testnet.json
index d4293802bc..459ecaca64 100644
--- a/packages/contracts-communication/configs/global/ExecutionService.testnet.json
+++ b/packages/contracts-communication/configs/global/ExecutionService.testnet.json
@@ -1,4 +1,4 @@
 {
   "executorEOA": "0xD0D45E468ADF3aCB8A98391ff47267783220ba6F",
-  "gasOracleName": "GasOracleMock"
+  "gasOracleName": "SynapseGasOracleMock"
 }
diff --git a/packages/contracts-communication/configs/global/SynapseModule.testnet.json b/packages/contracts-communication/configs/global/SynapseModule.testnet.json
index 0ad395d094..e78630c1d7 100644
--- a/packages/contracts-communication/configs/global/SynapseModule.testnet.json
+++ b/packages/contracts-communication/configs/global/SynapseModule.testnet.json
@@ -1,7 +1,7 @@
 {
   "claimFeeBPS": 10,
   "feeCollector": "0xD0D45E468ADF3aCB8A98391ff47267783220ba6F",
-  "gasOracleName": "GasOracleMock",
+  "gasOracleName": "SynapseGasOracleMock",
   "threshold": 6,
   "verifiers": [
     "0x0E399F695d72033d598aC2911B8A5e9986d6cbaD",
diff --git a/packages/contracts-communication/contracts/events/SynapseModuleEvents.sol b/packages/contracts-communication/contracts/events/SynapseModuleEvents.sol
index 5defbe3fba..84569f0968 100644
--- a/packages/contracts-communication/contracts/events/SynapseModuleEvents.sol
+++ b/packages/contracts-communication/contracts/events/SynapseModuleEvents.sol
@@ -12,4 +12,7 @@ abstract contract SynapseModuleEvents {
 
     event ClaimFeeFractionChanged(uint256 claimFeeFraction);
     event FeesClaimed(address feeCollector, uint256 collectedFees, address claimer, uint256 claimerFee);
+
+    event GasDataSent(uint256 dstChainId, bytes data);
+    event GasDataReceived(uint256 srcChainId, bytes data);
 }
diff --git a/packages/contracts-communication/contracts/interfaces/ISynapseGasOracle.sol b/packages/contracts-communication/contracts/interfaces/ISynapseGasOracle.sol
new file mode 100644
index 0000000000..18bf67b758
--- /dev/null
+++ b/packages/contracts-communication/contracts/interfaces/ISynapseGasOracle.sol
@@ -0,0 +1,15 @@
+// SPDX-License-Identifier: MIT
+pragma solidity ^0.8.0;
+
+import {IGasOracle} from "./IGasOracle.sol";
+
+interface ISynapseGasOracle is IGasOracle {
+    /// @notice Allows Synapse Module to pass the gas data from a remote chain to the Gas Oracle.
+    /// @dev Could only be called by Synapse Module.
+    /// @param srcChainId        The chain id of the remote chain.
+    /// @param data              The gas data from the remote chain.
+    function receiveRemoteGasData(uint256 srcChainId, bytes calldata data) external;
+
+    /// @notice Gets the gas data for the local chain.
+    function getLocalGasData() external view returns (bytes memory);
+}
diff --git a/packages/contracts-communication/contracts/interfaces/ISynapseModule.sol b/packages/contracts-communication/contracts/interfaces/ISynapseModule.sol
index 02ba033590..dc74af53a1 100644
--- a/packages/contracts-communication/contracts/interfaces/ISynapseModule.sol
+++ b/packages/contracts-communication/contracts/interfaces/ISynapseModule.sol
@@ -7,6 +7,7 @@ interface ISynapseModule is IInterchainModule {
     error SynapseModule__ClaimFeeFractionExceedsMax(uint256 claimFeeFraction);
     error SynapseModule__FeeCollectorNotSet();
     error SynapseModule__GasOracleNotContract(address gasOracle);
+    error SynapseModule__GasOracleNotSet();
     error SynapseModule__NoFeesToClaim();
 
     // ═══════════════════════════════════════════════ PERMISSIONED ════════════════════════════════════════════════════
diff --git a/packages/contracts-communication/contracts/libs/ModuleEntry.sol b/packages/contracts-communication/contracts/libs/ModuleEntry.sol
new file mode 100644
index 0000000000..25c079f54a
--- /dev/null
+++ b/packages/contracts-communication/contracts/libs/ModuleEntry.sol
@@ -0,0 +1,32 @@
+// SPDX-License-Identifier: MIT
+pragma solidity ^0.8.0;
+
+import {InterchainEntry} from "./InterchainEntry.sol";
+
+library ModuleEntryLib {
+    /// @notice Encodes the InterchainEntry and the auxiliary module data into a single bytes array
+    /// @param entry       The InterchainEntry to encode
+    /// @param moduleData  The auxiliary module data to encode
+    function encodeModuleEntry(
+        InterchainEntry memory entry,
+        bytes memory moduleData
+    )
+        internal
+        pure
+        returns (bytes memory)
+    {
+        return abi.encode(entry, moduleData);
+    }
+
+    /// @notice Decodes the bytes array into the InterchainEntry and the auxiliary module data
+    /// @param encodedModuleEntry  The bytes array to decode
+    /// @return entry              The decoded InterchainEntry
+    /// @return moduleData         The decoded auxiliary module data
+    function decodeModuleEntry(bytes memory encodedModuleEntry)
+        internal
+        pure
+        returns (InterchainEntry memory entry, bytes memory moduleData)
+    {
+        return abi.decode(encodedModuleEntry, (InterchainEntry, bytes));
+    }
+}
diff --git a/packages/contracts-communication/contracts/modules/InterchainModule.sol b/packages/contracts-communication/contracts/modules/InterchainModule.sol
index bf93677d9e..52ba5c3232 100644
--- a/packages/contracts-communication/contracts/modules/InterchainModule.sol
+++ b/packages/contracts-communication/contracts/modules/InterchainModule.sol
@@ -5,7 +5,7 @@ import {InterchainModuleEvents} from "../events/InterchainModuleEvents.sol";
 import {IInterchainDB} from "../interfaces/IInterchainDB.sol";
 import {IInterchainModule} from "../interfaces/IInterchainModule.sol";
 
-import {InterchainEntry} from "../libs/InterchainEntry.sol";
+import {InterchainEntry, ModuleEntryLib} from "../libs/ModuleEntry.sol";
 
 import {MessageHashUtils} from "@openzeppelin/contracts/utils/cryptography/MessageHashUtils.sol";
 
@@ -32,7 +32,8 @@ abstract contract InterchainModule is InterchainModuleEvents, IInterchainModule
         if (msg.value < requiredFee) {
             revert InterchainModule__InsufficientFee({actual: msg.value, required: requiredFee});
         }
-        bytes memory encodedEntry = abi.encode(entry);
+        bytes memory moduleData = _fillModuleData(destChainId, entry.dbNonce);
+        bytes memory encodedEntry = ModuleEntryLib.encodeModuleEntry(entry, moduleData);
         bytes32 ethSignedEntryHash = MessageHashUtils.toEthSignedMessageHash(keccak256(encodedEntry));
         _requestVerification(destChainId, encodedEntry);
         emit VerificationRequested(destChainId, encodedEntry, ethSignedEntryHash);
@@ -46,20 +47,27 @@ abstract contract InterchainModule is InterchainModuleEvents, IInterchainModule
     /// @dev Should be called once the Module has verified the entry and needs to signal this
     /// to the InterchainDB.
     function _verifyEntry(bytes memory encodedEntry) internal {
-        InterchainEntry memory entry = abi.decode(encodedEntry, (InterchainEntry));
+        (InterchainEntry memory entry, bytes memory moduleData) = ModuleEntryLib.decodeModuleEntry(encodedEntry);
         if (entry.srcChainId == block.chainid) {
             revert InterchainModule__SameChainId();
         }
         IInterchainDB(INTERCHAIN_DB).verifyEntry(entry);
+        _receiveModuleData(entry.srcChainId, entry.dbNonce, moduleData);
         emit EntryVerified(
             entry.srcChainId, encodedEntry, MessageHashUtils.toEthSignedMessageHash(keccak256(encodedEntry))
         );
     }
 
+    // solhint-disable no-empty-blocks
     /// @dev Internal logic to request the verification of an entry on the destination chain.
-    // solhint-disable-next-line no-empty-blocks
     function _requestVerification(uint256 destChainId, bytes memory encodedEntry) internal virtual {}
 
+    /// @dev Internal logic to fill the module data for the specified destination chain.
+    function _fillModuleData(uint256 destChainId, uint256 dbNonce) internal virtual returns (bytes memory) {}
+
+    /// @dev Internal logic to handle the auxiliary module data relayed from the remote chain.
+    function _receiveModuleData(uint256 srcChainId, uint256 dbNonce, bytes memory moduleData) internal virtual {}
+
     /// @dev Internal logic to get the module fee for verifying an entry on the specified destination chain.
     function _getModuleFee(uint256 destChainId) internal view virtual returns (uint256);
 }
diff --git a/packages/contracts-communication/contracts/modules/SynapseModule.sol b/packages/contracts-communication/contracts/modules/SynapseModule.sol
index b71c75fe01..ca0c5f4e71 100644
--- a/packages/contracts-communication/contracts/modules/SynapseModule.sol
+++ b/packages/contracts-communication/contracts/modules/SynapseModule.sol
@@ -4,7 +4,7 @@ pragma solidity 0.8.20;
 import {InterchainModule} from "./InterchainModule.sol";
 
 import {SynapseModuleEvents} from "../events/SynapseModuleEvents.sol";
-import {IGasOracle} from "../interfaces/IGasOracle.sol";
+import {ISynapseGasOracle} from "../interfaces/ISynapseGasOracle.sol";
 import {ISynapseModule} from "../interfaces/ISynapseModule.sol";
 
 import {ThresholdECDSA} from "../libs/ThresholdECDSA.sol";
@@ -26,6 +26,10 @@ contract SynapseModule is InterchainModule, Ownable, SynapseModuleEvents, ISynap
     uint256 internal _claimFeeFraction;
     /// @dev Gas limit for the verifyEntry function on the remote chain.
     mapping(uint256 chainId => uint256 gasLimit) internal _verifyGasLimit;
+    /// @dev Hash of the last gas data sent to the remote chain.
+    mapping(uint256 chainId => bytes32 gasDataHash) internal _lastGasDataHash;
+    /// @dev Nonce of the last gas data received from the remote chain.
+    mapping(uint256 chainId => uint256 gasDataNonce) internal _lastGasDataNonce;
 
     /// @inheritdoc ISynapseModule
     address public feeCollector;
@@ -173,6 +177,45 @@ contract SynapseModule is InterchainModule, Ownable, SynapseModuleEvents, ISynap
         emit VerifierRemoved(verifier);
     }
 
+    /// @dev Internal logic to fill the module data for the specified destination chain.
+    function _fillModuleData(
+        uint256 destChainId,
+        uint256 dbNonce
+    )
+        internal
+        override
+        returns (bytes memory moduleData)
+    {
+        moduleData = _getSynapseGasOracle().getLocalGasData();
+        // Exit early if data is empty
+        if (moduleData.length == 0) {
+            return moduleData;
+        }
+        bytes32 dataHash = keccak256(moduleData);
+        // Don't send the same data twice
+        if (dataHash == _lastGasDataHash[destChainId]) {
+            moduleData = "";
+        } else {
+            _lastGasDataHash[destChainId] = dataHash;
+            emit GasDataSent(destChainId, moduleData);
+        }
+    }
+
+    /// @dev Internal logic to handle the auxiliary module data relayed from the remote chain.
+    function _receiveModuleData(uint256 srcChainId, uint256 dbNonce, bytes memory moduleData) internal override {
+        // Exit early if data is empty
+        if (moduleData.length == 0) {
+            return;
+        }
+        // Don't process outdated data
+        uint256 lastNonce = _lastGasDataNonce[srcChainId];
+        if (lastNonce == 0 || lastNonce < dbNonce) {
+            _lastGasDataNonce[srcChainId] = dbNonce;
+            _getSynapseGasOracle().receiveRemoteGasData(srcChainId, moduleData);
+            emit GasDataReceived(srcChainId, moduleData);
+        }
+    }
+
     // ══════════════════════════════════════════════ INTERNAL VIEWS ═══════════════════════════════════════════════════
 
     /// @dev Internal logic to get the module fee for verifying an entry on the specified destination chain.
@@ -183,10 +226,18 @@ contract SynapseModule is InterchainModule, Ownable, SynapseModuleEvents, ISynap
         // entry is 32 (length) + 32*4 (fields) = 160
         // signatures: 32 (length) + 65*threshold (padded up to be a multiple of 32 bytes)
         // Total formula is: 4 + 32 (entry offset) + 32 (signatures offset) + 160 + 32
-        return IGasOracle(gasOracle).estimateTxCostInLocalUnits({
+        return _getSynapseGasOracle().estimateTxCostInLocalUnits({
             remoteChainId: destChainId,
             gasLimit: getVerifyGasLimit(destChainId),
             calldataSize: 292 + 64 * getThreshold()
         });
     }
+
+    /// @dev Internal logic to get the Synapse Gas Oracle. Reverts if the gas oracle is not set.
+    function _getSynapseGasOracle() internal view returns (ISynapseGasOracle synapseGasOracle) {
+        synapseGasOracle = ISynapseGasOracle(gasOracle);
+        if (address(synapseGasOracle) == address(0)) {
+            revert SynapseModule__GasOracleNotSet();
+        }
+    }
 }
diff --git a/packages/contracts-communication/script/MessagingBase.s.sol b/packages/contracts-communication/script/MessagingBase.s.sol
deleted file mode 100644
index 4db5ced040..0000000000
--- a/packages/contracts-communication/script/MessagingBase.s.sol
+++ /dev/null
@@ -1,103 +0,0 @@
-// SPDX-License-Identifier: MIT
-pragma solidity ^0.8.20;
-
-import {Script} from "forge-std/Script.sol";
-
-import {InterchainDB} from "../contracts/InterchainDB.sol";
-
-import {InterchainClientV1} from "../contracts/InterchainClientV1.sol";
-
-import {SynapseModule} from "../contracts/modules/SynapseModule.sol";
-
-import {InterchainApp} from "../contracts/InterchainApp.sol";
-
-import {GasOracleMock} from "../test/mocks/GasOracleMock.sol";
-
-import {ExecutionFeesMock} from "../test/mocks/ExecutionFeesMock.sol";
-
-contract MessagingBase is Script {
-    InterchainDB public icDB;
-    InterchainClientV1 public icClient;
-    SynapseModule public synapseModule;
-    GasOracleMock public gasOracleMock;
-    InterchainApp public icApp;
-    ExecutionFeesMock public executionFees;
-
-    function run() external {
-        vm.startBroadcast();
-        icDB = new InterchainDB();
-        // icClient deployment & config
-        icClient = new InterchainClientV1(address(icDB), msg.sender);
-
-        synapseModule = new SynapseModule(address(icDB), msg.sender);
-        gasOracleMock = new GasOracleMock();
-        executionFees = new ExecutionFeesMock();
-        synapseModule.setGasOracle(address(gasOracleMock));
-        icClient.setExecutionFees(address(executionFees));
-        icApp = new InterchainApp(address(icClient), new address[](0), new address[](0));
-
-        vm.stopBroadcast();
-    }
-
-    function newApp() external {
-        vm.startBroadcast();
-        icApp = new InterchainApp(0x007f3EC4A8E6DbaA84E50d0901F48966D83B7300, new address[](0), new address[](0));
-        vm.stopBroadcast();
-    }
-
-    function newAppSepolia() public {
-        vm.startBroadcast();
-        icApp = new InterchainApp(0xFd8A9eDf272e54614426a4c5849851D26A57C644, new address[](0), new address[](0));
-        vm.stopBroadcast();
-    }
-
-    function newAppConfigOP() external {
-        vm.startBroadcast();
-        icApp = InterchainApp(0x4a1f8D1378b614a59D0BB62EeeD811aaC1d22EC0);
-        uint64[] memory chainIDs = new uint64[](1);
-        chainIDs[0] = 11_155_111;
-        address[] memory linkedIApps = new address[](1);
-        linkedIApps[0] = 0x4a1f8D1378b614a59D0BB62EeeD811aaC1d22EC0;
-        address[] memory _sendingModules = new address[](1);
-        _sendingModules[0] = 0x48ADb7308f59d98657e779681aE6037902901918;
-        address[] memory _receivingModules = new address[](1);
-        _receivingModules[0] = 0x48ADb7308f59d98657e779681aE6037902901918;
-        uint256 _requiredResponses = 1;
-        uint64 _optimisticTimePeriod = 1;
-        icApp.setAppConfig(
-            chainIDs,
-            linkedIApps,
-            _sendingModules,
-            _receivingModules,
-            address(0),
-            _requiredResponses,
-            _optimisticTimePeriod
-        );
-        vm.stopBroadcast();
-    }
-
-    function newAppConfigSepolia() external {
-        vm.startBroadcast();
-        icApp = InterchainApp(0x4a1f8D1378b614a59D0BB62EeeD811aaC1d22EC0);
-        uint64[] memory chainIDs = new uint64[](1);
-        chainIDs[0] = 11_155_111;
-        address[] memory linkedIApps = new address[](1);
-        linkedIApps[0] = 0x4a1f8D1378b614a59D0BB62EeeD811aaC1d22EC0;
-        address[] memory _sendingModules = new address[](1);
-        _sendingModules[0] = 0x135189D37b0a734e4A339F0e9fd3219521729e7A;
-        address[] memory _receivingModules = new address[](1);
-        _receivingModules[0] = 0x135189D37b0a734e4A339F0e9fd3219521729e7A;
-        uint256 _requiredResponses = 1;
-        uint64 _optimisticTimePeriod = 1;
-        icApp.setAppConfig(
-            chainIDs,
-            linkedIApps,
-            _sendingModules,
-            _receivingModules,
-            address(0),
-            _requiredResponses,
-            _optimisticTimePeriod
-        );
-        vm.stopBroadcast();
-    }
-}
diff --git a/packages/contracts-communication/script/testnet-deploy.sh b/packages/contracts-communication/script/testnet-deploy.sh
index e6c4f38977..52857450ac 100755
--- a/packages/contracts-communication/script/testnet-deploy.sh
+++ b/packages/contracts-communication/script/testnet-deploy.sh
@@ -21,4 +21,4 @@ yarn fsr script/deploy/DeploySynapseModule.s.sol "$chainName" "$walletName" "$@"
 yarn fsr-str script/deploy/DeployWithMsgSender.s.sol "$chainName" "$walletName" "ExecutionFees" "$@"
 yarn fsr-str script/deploy/DeployWithMsgSender.s.sol "$chainName" "$walletName" "ExecutionService" "$@"
 
-yarn fsr-str script/deploy/DeployNoArgs.s.sol "$chainName" "$walletName" "GasOracleMock" "$@"
+yarn fsr-str script/deploy/DeployNoArgs.s.sol "$chainName" "$walletName" "SynapseGasOracleMock" "$@"
diff --git a/packages/contracts-communication/test/ExecutionService.t.sol b/packages/contracts-communication/test/ExecutionService.t.sol
index ad2d19d1f7..e37bd168ed 100644
--- a/packages/contracts-communication/test/ExecutionService.t.sol
+++ b/packages/contracts-communication/test/ExecutionService.t.sol
@@ -3,18 +3,18 @@ pragma solidity 0.8.20;
 
 import {ExecutionService, ExecutionServiceEvents, IExecutionService} from "../contracts/ExecutionService.sol";
 import {Test} from "forge-std/Test.sol";
-import {GasOracleMock} from "./mocks/GasOracleMock.sol";
+import {SynapseGasOracleMock} from "./mocks/SynapseGasOracleMock.sol";
 
 contract ExecutionServiceTest is ExecutionServiceEvents, Test {
     ExecutionService public executionService;
-    GasOracleMock public gasOracle;
+    SynapseGasOracleMock public gasOracle;
 
     address icClient = address(0x123);
     address executorEOA = address(0x456);
     address owner = makeAddr("Owner");
 
     function setUp() public {
-        gasOracle = new GasOracleMock();
+        gasOracle = new SynapseGasOracleMock();
         executionService = new ExecutionService(address(this));
         executionService.setInterchainClient(icClient);
         executionService.setExecutorEOA(executorEOA);
diff --git a/packages/contracts-communication/test/harnesses/ModuleEntryLibHarness.sol b/packages/contracts-communication/test/harnesses/ModuleEntryLibHarness.sol
new file mode 100644
index 0000000000..b890c8c12f
--- /dev/null
+++ b/packages/contracts-communication/test/harnesses/ModuleEntryLibHarness.sol
@@ -0,0 +1,25 @@
+// SPDX-License-Identifier: MIT
+pragma solidity 0.8.20;
+
+import {InterchainEntry, ModuleEntryLib} from "../../contracts/libs/ModuleEntry.sol";
+
+contract ModuleEntryLibHarness {
+    function encodeModuleEntry(
+        InterchainEntry memory entry,
+        bytes memory moduleData
+    )
+        external
+        pure
+        returns (bytes memory)
+    {
+        return ModuleEntryLib.encodeModuleEntry(entry, moduleData);
+    }
+
+    function decodeModuleEntry(bytes memory encodedModuleEntry)
+        external
+        pure
+        returns (InterchainEntry memory, bytes memory)
+    {
+        return ModuleEntryLib.decodeModuleEntry(encodedModuleEntry);
+    }
+}
diff --git a/packages/contracts-communication/test/libs/ModuleEntryLib.t.sol b/packages/contracts-communication/test/libs/ModuleEntryLib.t.sol
new file mode 100644
index 0000000000..0879d94a68
--- /dev/null
+++ b/packages/contracts-communication/test/libs/ModuleEntryLib.t.sol
@@ -0,0 +1,29 @@
+// SPDX-License-Identifier: MIT
+pragma solidity 0.8.20;
+
+import {InterchainEntry, ModuleEntryLibHarness} from "../harnesses/ModuleEntryLibHarness.sol";
+
+import {Test} from "forge-std/Test.sol";
+
+// solhint-disable func-name-mixedcase
+contract ModuleEntryLibTest is Test {
+    ModuleEntryLibHarness public libHarness;
+
+    function setUp() public {
+        libHarness = new ModuleEntryLibHarness();
+    }
+
+    function assertEq(InterchainEntry memory actual, InterchainEntry memory expected) public {
+        assertEq(actual.srcChainId, expected.srcChainId, "!srcChainId");
+        assertEq(actual.dbNonce, expected.dbNonce, "!dbNonce");
+        assertEq(actual.srcWriter, expected.srcWriter, "!srcWriter");
+        assertEq(actual.dataHash, expected.dataHash, "!dataHash");
+    }
+
+    function test_roundTrip(InterchainEntry memory entry, bytes memory moduleData) public {
+        bytes memory encoded = libHarness.encodeModuleEntry(entry, moduleData);
+        (InterchainEntry memory decodedEntry, bytes memory decodedModuleData) = libHarness.decodeModuleEntry(encoded);
+        assertEq(decodedEntry, entry);
+        assertEq(decodedModuleData, moduleData);
+    }
+}
diff --git a/packages/contracts-communication/test/mocks/GasOracleMock.sol b/packages/contracts-communication/test/mocks/SynapseGasOracleMock.sol
similarity index 69%
rename from packages/contracts-communication/test/mocks/GasOracleMock.sol
rename to packages/contracts-communication/test/mocks/SynapseGasOracleMock.sol
index ef38762239..f730440d58 100644
--- a/packages/contracts-communication/test/mocks/GasOracleMock.sol
+++ b/packages/contracts-communication/test/mocks/SynapseGasOracleMock.sol
@@ -1,9 +1,13 @@
 // SPDX-License-Identifier: MIT
 pragma solidity 0.8.20;
 
-import {IGasOracle} from "../../contracts/interfaces/IGasOracle.sol";
+import {ISynapseGasOracle} from "../../contracts/interfaces/ISynapseGasOracle.sol";
+
+contract SynapseGasOracleMock is ISynapseGasOracle {
+    function receiveRemoteGasData(uint256 srcChainId, bytes calldata data) external {}
+
+    function getLocalGasData() external view returns (bytes memory) {}
 
-contract GasOracleMock is IGasOracle {
     function convertRemoteValueToLocalUnits(
         uint256 remoteChainId,
         uint256 value
diff --git a/packages/contracts-communication/test/modules/SynapseModule.Destination.t.sol b/packages/contracts-communication/test/modules/SynapseModule.Destination.t.sol
index 85c1700490..71a0eb93c8 100644
--- a/packages/contracts-communication/test/modules/SynapseModule.Destination.t.sol
+++ b/packages/contracts-communication/test/modules/SynapseModule.Destination.t.sol
@@ -8,7 +8,7 @@ import {InterchainEntry} from "../../contracts/libs/InterchainEntry.sol";
 import {ThresholdECDSALib} from "../../contracts/libs/ThresholdECDSA.sol";
 import {SynapseModule} from "../../contracts/modules/SynapseModule.sol";
 
-import {GasOracleMock} from "../mocks/GasOracleMock.sol";
+import {SynapseGasOracleMock} from "../mocks/SynapseGasOracleMock.sol";
 import {InterchainDBMock, IInterchainDB} from "../mocks/InterchainDBMock.sol";
 
 import {Test} from "forge-std/Test.sol";
@@ -17,7 +17,7 @@ import {Test} from "forge-std/Test.sol";
 // solhint-disable ordering
 contract SynapseModuleDestinationTest is Test, InterchainModuleEvents, SynapseModuleEvents {
     SynapseModule public module;
-    GasOracleMock public gasOracle;
+    SynapseGasOracleMock public gasOracle;
     InterchainDBMock public interchainDB;
 
     address public feeCollector = makeAddr("FeeCollector");
@@ -32,6 +32,7 @@ contract SynapseModuleDestinationTest is Test, InterchainModuleEvents, SynapseMo
         srcWriter: bytes32(uint256(3)),
         dataHash: bytes32(uint256(4))
     });
+    bytes public mockModuleData = "";
 
     uint256 public constant PK_0 = 1000;
     uint256 public constant PK_1 = 2000;
@@ -49,7 +50,7 @@ contract SynapseModuleDestinationTest is Test, InterchainModuleEvents, SynapseMo
         vm.chainId(DST_CHAIN_ID);
         interchainDB = new InterchainDBMock();
         module = new SynapseModule(address(interchainDB), owner);
-        gasOracle = new GasOracleMock();
+        gasOracle = new SynapseGasOracleMock();
         vm.startPrank(owner);
         module.setGasOracle(address(gasOracle));
         module.setFeeCollector(feeCollector);
@@ -88,10 +89,10 @@ contract SynapseModuleDestinationTest is Test, InterchainModuleEvents, SynapseMo
 
     function encodeAndHashEntry(InterchainEntry memory entry)
         internal
-        pure
+        view
         returns (bytes memory encodedEntry, bytes32 ethSignedHash)
     {
-        encodedEntry = abi.encode(entry);
+        encodedEntry = abi.encode(entry, mockModuleData);
         ethSignedHash = keccak256(abi.encodePacked("\x19Ethereum Signed Message:\n32", keccak256(encodedEntry)));
     }
 
@@ -100,7 +101,7 @@ contract SynapseModuleDestinationTest is Test, InterchainModuleEvents, SynapseMo
         uint256[] memory pks
     )
         internal
-        pure
+        view
         returns (bytes memory signatures)
     {
         (, bytes32 ethSignedHash) = encodeAndHashEntry(entry);
@@ -112,7 +113,7 @@ contract SynapseModuleDestinationTest is Test, InterchainModuleEvents, SynapseMo
     }
 
     function verifyEntry(InterchainEntry memory entry, bytes memory signatures) internal {
-        module.verifyEntry(abi.encode(entry), signatures);
+        module.verifyEntry(abi.encode(entry, mockModuleData), signatures);
     }
 
     // ═══════════════════════════════════════════════ TEST HELPERS ════════════════════════════════════════════════════
diff --git a/packages/contracts-communication/test/modules/SynapseModule.Management.t.sol b/packages/contracts-communication/test/modules/SynapseModule.Management.t.sol
index 7ab125ccdf..ede5c5fd3e 100644
--- a/packages/contracts-communication/test/modules/SynapseModule.Management.t.sol
+++ b/packages/contracts-communication/test/modules/SynapseModule.Management.t.sol
@@ -5,7 +5,7 @@ import {SynapseModuleEvents} from "../../contracts/events/SynapseModuleEvents.so
 import {SynapseModule, ISynapseModule} from "../../contracts/modules/SynapseModule.sol";
 import {ThresholdECDSALib} from "../../contracts/libs/ThresholdECDSA.sol";
 
-import {GasOracleMock} from "../mocks/GasOracleMock.sol";
+import {SynapseGasOracleMock} from "../mocks/SynapseGasOracleMock.sol";
 
 import {Ownable} from "@openzeppelin/contracts/access/Ownable.sol";
 
@@ -15,7 +15,7 @@ import {Test} from "forge-std/Test.sol";
 // solhint-disable ordering
 contract SynapseModuleManagementTest is Test, SynapseModuleEvents {
     SynapseModule public module;
-    GasOracleMock public gasOracle;
+    SynapseGasOracleMock public gasOracle;
 
     address public interchainDB = makeAddr("InterchainDB");
     address public owner = makeAddr("Owner");
@@ -29,7 +29,7 @@ contract SynapseModuleManagementTest is Test, SynapseModuleEvents {
 
     function setUp() public {
         module = new SynapseModule(interchainDB, owner);
-        gasOracle = new GasOracleMock();
+        gasOracle = new SynapseGasOracleMock();
         allVerifiers.push(VERIFIER_1);
         allVerifiers.push(VERIFIER_2);
         allVerifiers.push(VERIFIER_3);
diff --git a/packages/contracts-communication/test/modules/SynapseModule.Source.t.sol b/packages/contracts-communication/test/modules/SynapseModule.Source.t.sol
index 23a4ae7070..119474b537 100644
--- a/packages/contracts-communication/test/modules/SynapseModule.Source.t.sol
+++ b/packages/contracts-communication/test/modules/SynapseModule.Source.t.sol
@@ -7,7 +7,7 @@ import {IInterchainModule} from "../../contracts/interfaces/IInterchainModule.so
 import {InterchainEntry} from "../../contracts/libs/InterchainEntry.sol";
 import {SynapseModule, ISynapseModule} from "../../contracts/modules/SynapseModule.sol";
 
-import {GasOracleMock} from "../mocks/GasOracleMock.sol";
+import {SynapseGasOracleMock} from "../mocks/SynapseGasOracleMock.sol";
 
 import {Test} from "forge-std/Test.sol";
 
@@ -15,7 +15,7 @@ import {Test} from "forge-std/Test.sol";
 // solhint-disable ordering
 contract SynapseModuleSourceTest is Test, InterchainModuleEvents, SynapseModuleEvents {
     SynapseModule public module;
-    GasOracleMock public gasOracle;
+    SynapseGasOracleMock public gasOracle;
 
     address public interchainDB = makeAddr("InterchainDB");
     address public feeCollector = makeAddr("FeeCollector");
@@ -35,11 +35,12 @@ contract SynapseModuleSourceTest is Test, InterchainModuleEvents, SynapseModuleE
         srcWriter: bytes32(uint256(3)),
         dataHash: bytes32(uint256(4))
     });
+    bytes public mockModuleData = "";
 
     function setUp() public {
         vm.chainId(SRC_CHAIN_ID);
         module = new SynapseModule(interchainDB, owner);
-        gasOracle = new GasOracleMock();
+        gasOracle = new SynapseGasOracleMock();
         vm.startPrank(owner);
         module.setGasOracle(address(gasOracle));
         module.setFeeCollector(feeCollector);
@@ -50,7 +51,7 @@ contract SynapseModuleSourceTest is Test, InterchainModuleEvents, SynapseModuleE
         // Mock: gasOracle.estimateTxCostInLocalUnits(DST_CHAIN_ID, *, *) to return FEE
         vm.mockCall(
             address(gasOracle),
-            abi.encodeWithSelector(GasOracleMock.estimateTxCostInLocalUnits.selector, DST_CHAIN_ID),
+            abi.encodeWithSelector(SynapseGasOracleMock.estimateTxCostInLocalUnits.selector, DST_CHAIN_ID),
             abi.encode(FEE)
         );
     }
@@ -63,10 +64,10 @@ contract SynapseModuleSourceTest is Test, InterchainModuleEvents, SynapseModuleE
 
     function encodeAndHashEntry(InterchainEntry memory entry)
         internal
-        pure
+        view
         returns (bytes memory encodedEntry, bytes32 ethSignedHash)
     {
-        encodedEntry = abi.encode(entry);
+        encodedEntry = abi.encode(entry, mockModuleData);
         ethSignedHash = keccak256(abi.encodePacked("\x19Ethereum Signed Message:\n32", keccak256(encodedEntry)));
     }