fix SSP

src/SequencerSetPublisher.sol

@@ -25,7 +25,8 @@ contract SequencerSetPublisher is
     using ECDSA for bytes32;
     using MessageHashUtils for bytes32;
 
-    mapping(uint256 height => SequencerSetUpdateWitness) public sequencerSetUpdateWitnesses;
+    mapping(uint256 height => SequencerSetUpdateWitness[]) private _sequencerSetUpdateWitnesses;
+    mapping(uint256 height => mapping(bytes32 pubkeyHash => bool)) private _hasWitness;
 
     function initialize(
         address initialOwner
@@ -40,11 +41,18 @@ contract SequencerSetPublisher is
     ) external override {
         BtcUtils.verifyBtcSignature(witness.sigHash, witness.btcPubkey, witness.btcSig);
 
-        // Avoid double commit
-        if (sequencerSetUpdateWitnesses[goatHeight].sigHash != bytes32(0)) {
+        bytes32 pubkeyHash = keccak256(witness.btcPubkey);
+        if (_hasWitness[goatHeight][pubkeyHash]) {
             revert DoubleCommit();
         }
 
-        sequencerSetUpdateWitnesses[goatHeight] = witness;
+        _hasWitness[goatHeight][pubkeyHash] = true;
+        _sequencerSetUpdateWitnesses[goatHeight].push(witness);
+    }
+
+    function getSequencerSetUpdateWitnesses(
+        uint256 goatHeight
+    ) external view override returns (SequencerSetUpdateWitness[] memory) {
+        return _sequencerSetUpdateWitnesses[goatHeight];
     }
 }

src/interfaces/ISequencerSetPublisher.sol

@@ -19,4 +19,8 @@ interface ISequencerSetPublisher {
         uint256 goatHeight,
         SequencerSetUpdateWitness calldata witness
     ) external;
+
+    function getSequencerSetUpdateWitnesses(
+        uint256 goatHeight
+    ) external view returns (SequencerSetUpdateWitness[] memory);
 }

test/SequencerSetPublisher.t.sol

@@ -255,4 +255,44 @@ contract SequencerSetPublisherTest is Test {
             keccak256("set5")
         );
     }
+
+    function testMultipleWitnesses() public {
+        uint256 height = 100;
+        bytes32 sigHash = keccak256("commit_multi");
+
+        // Witness 1 (pk=11)
+        run_sequencer_update_test(
+            batch, // contains 11
+            batch,
+            height,
+            sigHash,
+            bytes32(0),
+            bytes32(0)
+        );
+
+        // Witness 2 (pk=21)
+        run_sequencer_update_test(
+            batch1, // contains 21
+            batch1,
+            height,
+            sigHash,
+            bytes32(0),
+            bytes32(0)
+        );
+
+        // Check if we have 2 witnesses
+        ISequencerSetPublisher.SequencerSetUpdateWitness[] memory witnesses = sspublisher.getSequencerSetUpdateWitnesses(height);
+        assertEq(witnesses.length, 2);
+
+        // Try adding Witness 1 again (should fail)
+        vm.expectRevert(ISequencerSetPublisher.DoubleCommit.selector);
+        run_sequencer_update_test(
+            batch,
+            batch,
+            height,
+            sigHash,
+            bytes32(0),
+            bytes32(0)
+        );
+    }
 }