Document DelegateCall requirement for proposeTransactionsWithSignature to prevent signature validation errors

README.md

@@ -58,6 +58,22 @@ The second step is to take the value for the returned `bytes` and provide them w
 safe.proposeTransactionWithSignature(weth, abi.encodeCall(IWETH.withdraw, (0)), sender, signature);
 ```
 
+#### Batch transactions
+
+```solidity
+safe.proposeTransactions(targets, datas, sender, "m/44'/60'/0'/0/0");
+```
+
+For pre-computed signatures with hardware wallets:
+
+```solidity
+(address to, bytes memory data) = safe.getProposeTransactionsTargetAndData(targets, datas);
+bytes memory signature = safe.sign(to, data, Enum.Operation.DelegateCall, sender, "m/44'/60'/0'/0/0");
+safe.proposeTransactionsWithSignature(targets, datas, sender, signature);
+```
+
+**⚠️ Important**: Batch transactions require `Enum.Operation.DelegateCall` (not `Call`). Using `Call` causes signature validation errors.
+
 ### Requirements
 
 - Foundry with FFI enabled:

src/Safe.sol

@@ -282,13 +282,21 @@ library Safe {
     }
 
     /// @notice Propose multiple transactions with a precomputed signature
-    /// @dev    This can be used to propose transactions signed with a hardware wallet in a two-step process
+    /// @dev    This can be used to propose transactions signed with a hardware wallet in a two-step process.
+    ///         The signature must be created with Enum.Operation.DelegateCall, as batch transactions use
+    ///         DelegateCall to preserve msg.sender across sub-calls.
+    ///
+    ///         WARNING: Using Enum.Operation.Call instead of DelegateCall will cause the Safe API to reject
+    ///         your transaction with an error about an incorrect signer address. The signature will be invalid
+    ///         because it was signed with the wrong operation type.
     ///
     /// @param  self        The Safe client
     /// @param  targets     The list of target addresses for the transactions
     /// @param  datas       The list of data payloads for the transactions
     /// @param  sender      The address of the account that is proposing the transactions
-    /// @param  signature   The precomputed signature for the batch of transactions, e.g. using {sign}
+    /// @param  signature   The precomputed signature for the batch of transactions. MUST be signed with
+    ///                     Enum.Operation.DelegateCall (use {sign} with DelegateCall operation).
+    ///                     Signing with Call instead of DelegateCall will result in signature validation failure.
     /// @return txHash      The hash of the proposed Safe transaction
     function proposeTransactionsWithSignature(
         Client storage self,

test/Safe.t.sol

@@ -5,6 +5,7 @@ import {Test, console} from "forge-std/Test.sol";
 import {Safe} from "../src/Safe.sol";
 import {strings} from "solidity-stringutils/strings.sol";
 import {IWETH} from "./interfaces/IWETH.sol";
+import {Enum} from "safe-smart-account/common/Enum.sol";
 
 contract SafeTest is Test {
     using Safe for *;
@@ -39,4 +40,28 @@ contract SafeTest is Test {
         bytes memory data = safe.getExecTransactionData(weth, abi.encodeCall(IWETH.withdraw, (0)), foundrySigner1, "");
         console.logBytes(data);
     }
+
+    function test_Safe_proposeTransactionsWithSignature() public {
+        address weth = 0x4200000000000000000000000000000000000006;
+
+        // Create batch of transactions
+        address[] memory targets = new address[](2);
+        bytes[] memory datas = new bytes[](2);
+
+        targets[0] = weth;
+        datas[0] = abi.encodeCall(IWETH.withdraw, (0));
+
+        targets[1] = weth;
+        datas[1] = abi.encodeCall(IWETH.withdraw, (1));
+
+        // Get the target and data for signing
+        (address to, bytes memory data) = safe.getProposeTransactionsTargetAndData(targets, datas);
+
+        // Sign with DelegateCall operation (required for batch transactions)
+        vm.rememberKey(uint256(foundrySigner1PrivateKey));
+        bytes memory signature = safe.sign(to, data, Enum.Operation.DelegateCall, foundrySigner1, "");
+
+        // Propose transactions with the signature
+        safe.proposeTransactionsWithSignature(targets, datas, foundrySigner1, signature);
+    }
 }