diff --git a/circuits/cpp/src/aztec3/circuits/abis/rollup/root/root_rollup_inputs.hpp b/circuits/cpp/src/aztec3/circuits/abis/rollup/root/root_rollup_inputs.hpp
index 672c49fa708..e16d8b738e1 100644
--- a/circuits/cpp/src/aztec3/circuits/abis/rollup/root/root_rollup_inputs.hpp
+++ b/circuits/cpp/src/aztec3/circuits/abis/rollup/root/root_rollup_inputs.hpp
@@ -27,6 +27,14 @@ template <typename NCT> struct RootRollupInputs {
     std::array<fr, PRIVATE_DATA_TREE_ROOTS_TREE_HEIGHT> new_historic_private_data_tree_root_sibling_path;
     std::array<fr, CONTRACT_TREE_ROOTS_TREE_HEIGHT> new_historic_contract_tree_root_sibling_path;
 
+    // inputs required to process l1 to l2 messages
+    std::array<fr, NUMBER_OF_L1_L2_MESSAGES_PER_ROLLUP> l1_to_l2_messages;
+    std::array<fr, L1_TO_L2_MSG_SUBTREE_INCLUSION_CHECK_DEPTH> new_l1_to_l2_message_tree_root_sibling_path;
+    std::array<fr, L1_TO_L2_MSG_TREE_ROOTS_TREE_HEIGHT> new_historic_l1_to_l2_message_roots_tree_sibling_path;
+
+    AppendOnlyTreeSnapshot<NCT> start_l1_to_l2_message_tree_snapshot;
+    AppendOnlyTreeSnapshot<NCT> start_historic_tree_l1_to_l2_message_tree_roots_snapshot;
+
     bool operator==(RootRollupInputs<NCT> const&) const = default;
 };
 
@@ -37,6 +45,11 @@ template <typename NCT> void read(uint8_t const*& it, RootRollupInputs<NCT>& obj
     read(it, obj.previous_rollup_data);
     read(it, obj.new_historic_private_data_tree_root_sibling_path);
     read(it, obj.new_historic_contract_tree_root_sibling_path);
+    read(it, obj.l1_to_l2_messages);
+    read(it, obj.new_l1_to_l2_message_tree_root_sibling_path);
+    read(it, obj.new_historic_l1_to_l2_message_roots_tree_sibling_path);
+    read(it, obj.start_l1_to_l2_message_tree_snapshot);
+    read(it, obj.start_historic_tree_l1_to_l2_message_tree_roots_snapshot);
 };
 
 template <typename NCT> void write(std::vector<uint8_t>& buf, RootRollupInputs<NCT> const& obj)
@@ -46,6 +59,11 @@ template <typename NCT> void write(std::vector<uint8_t>& buf, RootRollupInputs<N
     write(buf, obj.previous_rollup_data);
     write(buf, obj.new_historic_private_data_tree_root_sibling_path);
     write(buf, obj.new_historic_contract_tree_root_sibling_path);
+    write(buf, obj.l1_to_l2_messages);
+    write(buf, obj.new_l1_to_l2_message_tree_root_sibling_path);
+    write(buf, obj.new_historic_l1_to_l2_message_roots_tree_sibling_path);
+    write(buf, obj.start_l1_to_l2_message_tree_snapshot);
+    write(buf, obj.start_historic_tree_l1_to_l2_message_tree_roots_snapshot);
 };
 
 template <typename NCT> std::ostream& operator<<(std::ostream& os, RootRollupInputs<NCT> const& obj)
@@ -53,7 +71,15 @@ template <typename NCT> std::ostream& operator<<(std::ostream& os, RootRollupInp
     return os << "previous_rollup_data: " << obj.previous_rollup_data << "\n"
               << "new_historic_private_data_tree_roots: " << obj.new_historic_private_data_tree_root_sibling_path
               << "\n"
-              << "new_historic_contract_tree_roots: " << obj.new_historic_contract_tree_root_sibling_path << "\n";
+              << "new_historic_contract_tree_roots: " << obj.new_historic_contract_tree_root_sibling_path << "\n"
+              << "new_l1_to_l2_messages: " << obj.l1_to_l2_messages << "\n"
+              << "new_l1_to_l2_message_tree_root_sibling_path: " << obj.new_l1_to_l2_message_tree_root_sibling_path
+              << "\n"
+              << "new_historic_l1_to_l2_message_roots_tree_sibling_path: "
+              << obj.new_historic_l1_to_l2_message_roots_tree_sibling_path << "\n"
+              << "start_l1_to_l2_message_tree_snapshot: " << obj.start_l1_to_l2_message_tree_snapshot << "\n"
+              << "start_historic_tree_l1_to_l2_message_tree_roots_snapshot: "
+              << obj.start_historic_tree_l1_to_l2_message_tree_roots_snapshot << "\n";
 }
 
 }  // namespace aztec3::circuits::abis
\ No newline at end of file
diff --git a/circuits/cpp/src/aztec3/circuits/abis/rollup/root/root_rollup_public_inputs.hpp b/circuits/cpp/src/aztec3/circuits/abis/rollup/root/root_rollup_public_inputs.hpp
index a2d1b560b1f..5aca0ad21a1 100644
--- a/circuits/cpp/src/aztec3/circuits/abis/rollup/root/root_rollup_public_inputs.hpp
+++ b/circuits/cpp/src/aztec3/circuits/abis/rollup/root/root_rollup_public_inputs.hpp
@@ -15,6 +15,7 @@ namespace aztec3::circuits::abis {
 using aztec3::utils::types::CircuitTypes;
 using aztec3::utils::types::NativeTypes;
 
+
 template <typename NCT> struct RootRollupPublicInputs {
     using fr = typename NCT::fr;
     using AggregationObject = typename NCT::AggregationObject;
@@ -40,7 +41,14 @@ template <typename NCT> struct RootRollupPublicInputs {
     AppendOnlyTreeSnapshot<NCT> start_tree_of_historic_contract_tree_roots_snapshot;
     AppendOnlyTreeSnapshot<NCT> end_tree_of_historic_contract_tree_roots_snapshot;
 
+    AppendOnlyTreeSnapshot<NCT> start_l1_to_l2_messages_tree_snapshot;
+    AppendOnlyTreeSnapshot<NCT> end_l1_to_l2_messages_tree_snapshot;
+
+    AppendOnlyTreeSnapshot<NCT> start_tree_of_historic_l1_to_l2_messages_tree_roots_snapshot;
+    AppendOnlyTreeSnapshot<NCT> end_tree_of_historic_l1_to_l2_messages_tree_roots_snapshot;
+
     std::array<fr, 2> calldata_hash;
+    std::array<fr, 2> l1_to_l2_messages_hash;
 
     bool operator==(RootRollupPublicInputs<NCT> const&) const = default;
 
@@ -53,11 +61,15 @@ template <typename NCT> struct RootRollupPublicInputs {
         write(buf, start_contract_tree_snapshot);
         write(buf, start_tree_of_historic_private_data_tree_roots_snapshot);
         write(buf, start_tree_of_historic_contract_tree_roots_snapshot);
+        write(buf, start_l1_to_l2_messages_tree_snapshot);
+        write(buf, start_tree_of_historic_l1_to_l2_messages_tree_roots_snapshot);
         write(buf, end_private_data_tree_snapshot);
         write(buf, end_nullifier_tree_snapshot);
         write(buf, end_contract_tree_snapshot);
         write(buf, end_tree_of_historic_private_data_tree_roots_snapshot);
         write(buf, end_tree_of_historic_contract_tree_roots_snapshot);
+        write(buf, end_l1_to_l2_messages_tree_snapshot);
+        write(buf, end_tree_of_historic_l1_to_l2_messages_tree_roots_snapshot);
 
         // Stitching calldata hash together
         auto high_buffer = calldata_hash[0].to_buffer();
@@ -70,6 +82,17 @@ template <typename NCT> struct RootRollupPublicInputs {
             buf.push_back(low_buffer[16 + i]);
         }
 
+        // Stitch l1_to_l2_messages_hash
+        auto high_buffer_m = l1_to_l2_messages_hash[0].to_buffer();
+        auto low_buffer_m = l1_to_l2_messages_hash[1].to_buffer();
+
+        for (uint8_t i = 0; i < 16; i++) {
+            buf.push_back(high_buffer_m[16 + i]);
+        }
+        for (uint8_t i = 0; i < 16; i++) {
+            buf.push_back(low_buffer_m[16 + i]);
+        }
+
         return sha256::sha256_to_field(buf);
     }
 };
@@ -91,7 +114,12 @@ template <typename NCT> void read(uint8_t const*& it, RootRollupPublicInputs<NCT
     read(it, obj.end_tree_of_historic_private_data_tree_roots_snapshot);
     read(it, obj.start_tree_of_historic_contract_tree_roots_snapshot);
     read(it, obj.end_tree_of_historic_contract_tree_roots_snapshot);
+    read(it, obj.start_l1_to_l2_messages_tree_snapshot);
+    read(it, obj.end_l1_to_l2_messages_tree_snapshot);
+    read(it, obj.start_tree_of_historic_l1_to_l2_messages_tree_roots_snapshot);
+    read(it, obj.end_tree_of_historic_l1_to_l2_messages_tree_roots_snapshot);
     read(it, obj.calldata_hash);
+    read(it, obj.l1_to_l2_messages_hash);
 };
 
 template <typename NCT> void write(std::vector<uint8_t>& buf, RootRollupPublicInputs<NCT> const& obj)
@@ -111,7 +139,12 @@ template <typename NCT> void write(std::vector<uint8_t>& buf, RootRollupPublicIn
     write(buf, obj.end_tree_of_historic_private_data_tree_roots_snapshot);
     write(buf, obj.start_tree_of_historic_contract_tree_roots_snapshot);
     write(buf, obj.end_tree_of_historic_contract_tree_roots_snapshot);
+    write(buf, obj.start_l1_to_l2_messages_tree_snapshot);
+    write(buf, obj.end_l1_to_l2_messages_tree_snapshot);
+    write(buf, obj.start_tree_of_historic_l1_to_l2_messages_tree_roots_snapshot);
+    write(buf, obj.end_tree_of_historic_l1_to_l2_messages_tree_roots_snapshot);
     write(buf, obj.calldata_hash);
+    write(buf, obj.l1_to_l2_messages_hash);
 };
 
 template <typename NCT> std::ostream& operator<<(std::ostream& os, RootRollupPublicInputs<NCT> const& obj)
@@ -133,7 +166,15 @@ template <typename NCT> std::ostream& operator<<(std::ostream& os, RootRollupPub
               << obj.start_tree_of_historic_contract_tree_roots_snapshot << "\n"
               << "end_tree_of_historic_contract_tree_roots_snapshot: "
               << obj.end_tree_of_historic_contract_tree_roots_snapshot << "\n"
-              << "calldata_hash: " << obj.calldata_hash << "\n";
+              << "start_l1_to_l2_messages_tree_snapshot: " << obj.start_l1_to_l2_messages_tree_snapshot << "\n"
+              << "end_l1_tol2_messages_tree_snapshot: " << obj.end_l1_to_l2_messages_tree_snapshot << "\n"
+              << "start_tree_of_historic_l1_to_l2_messages_tree_roots_snapshot: "
+              << obj.start_tree_of_historic_l1_to_l2_messages_tree_roots_snapshot << "\n"
+              << "end_tree_of_historic_l1_tol2_messages_tree_roots_snapshot: "
+              << obj.end_tree_of_historic_l1_to_l2_messages_tree_roots_snapshot << "\n"
+              << "calldata_hash: " << obj.calldata_hash << "\n"
+              << "l1_to_l2_messages_hash: " << obj.l1_to_l2_messages_hash << "\n";
+    ;
 };
 
 }  // namespace aztec3::circuits::abis
\ No newline at end of file
diff --git a/circuits/cpp/src/aztec3/circuits/rollup/base/native_base_rollup_circuit.cpp b/circuits/cpp/src/aztec3/circuits/rollup/base/native_base_rollup_circuit.cpp
index 6cf0e961217..926f16779b8 100644
--- a/circuits/cpp/src/aztec3/circuits/rollup/base/native_base_rollup_circuit.cpp
+++ b/circuits/cpp/src/aztec3/circuits/rollup/base/native_base_rollup_circuit.cpp
@@ -400,7 +400,7 @@ AppendOnlySnapshot check_nullifier_tree_non_membership_and_insert_to_tree(DummyC
     }
 
     // Check that the new subtree is to be inserted at the next location, and is empty currently
-    const auto empty_nullifier_subtree_root = calculate_empty_tree_root(NULLIFIER_SUBTREE_DEPTH);
+    const auto empty_nullifier_subtree_root = components::calculate_empty_tree_root(NULLIFIER_SUBTREE_DEPTH);
     auto leafIndexNullifierSubtreeDepth =
         baseRollupInputs.start_nullifier_tree_snapshot.next_available_leaf_index >> NULLIFIER_SUBTREE_DEPTH;
     check_membership<NT>(composer,
@@ -541,7 +541,7 @@ BaseOrMergeRollupPublicInputs base_rollup_circuit(DummyComposer& composer, BaseR
     NT::fr const commitments_tree_subroot = calculate_commitments_subtree(composer, baseRollupInputs);
 
     // Insert commitment subtrees:
-    const auto empty_commitments_subtree_root = calculate_empty_tree_root(PRIVATE_DATA_SUBTREE_DEPTH);
+    const auto empty_commitments_subtree_root = components::calculate_empty_tree_root(PRIVATE_DATA_SUBTREE_DEPTH);
     auto end_private_data_tree_snapshot =
         components::insert_subtree_to_snapshot_tree(composer,
                                                     baseRollupInputs.start_private_data_tree_snapshot,
@@ -552,7 +552,7 @@ BaseOrMergeRollupPublicInputs base_rollup_circuit(DummyComposer& composer, BaseR
                                                     "empty commitment subtree membership check");
 
     // Insert contract subtrees:
-    const auto empty_contracts_subtree_root = calculate_empty_tree_root(CONTRACT_SUBTREE_DEPTH);
+    const auto empty_contracts_subtree_root = components::calculate_empty_tree_root(CONTRACT_SUBTREE_DEPTH);
     auto end_contract_tree_snapshot =
         components::insert_subtree_to_snapshot_tree(composer,
                                                     baseRollupInputs.start_contract_tree_snapshot,
diff --git a/circuits/cpp/src/aztec3/circuits/rollup/components/components.cpp b/circuits/cpp/src/aztec3/circuits/rollup/components/components.cpp
index 8f776438660..48d2b3d84c4 100644
--- a/circuits/cpp/src/aztec3/circuits/rollup/components/components.cpp
+++ b/circuits/cpp/src/aztec3/circuits/rollup/components/components.cpp
@@ -8,6 +8,7 @@
 #include "barretenberg/crypto/sha256/sha256.hpp"
 #include "barretenberg/ecc/curves/bn254/fr.hpp"
 #include "barretenberg/stdlib/hash/pedersen/pedersen.hpp"
+#include "barretenberg/stdlib/merkle_tree/memory_tree.hpp"
 
 #include <algorithm>
 #include <array>
@@ -18,6 +19,18 @@
 
 namespace aztec3::circuits::rollup::components {
 
+/**
+ * @brief Get the root of an empty tree of a given depth
+ *
+ * @param depth
+ * @return NT::fr
+ */
+NT::fr calculate_empty_tree_root(const size_t depth)
+{
+    stdlib::merkle_tree::MemoryTree const empty_tree = stdlib::merkle_tree::MemoryTree(depth);
+    return empty_tree.root();
+}
+
 /**
  * @brief Create an aggregation object for the proofs that are provided
  *          - We add points P0 for each of our proofs
diff --git a/circuits/cpp/src/aztec3/circuits/rollup/components/components.hpp b/circuits/cpp/src/aztec3/circuits/rollup/components/components.hpp
index f6df9f8a8a7..42074456b1e 100644
--- a/circuits/cpp/src/aztec3/circuits/rollup/components/components.hpp
+++ b/circuits/cpp/src/aztec3/circuits/rollup/components/components.hpp
@@ -8,6 +8,7 @@ using aztec3::circuits::check_membership;
 using aztec3::circuits::root_from_sibling_path;
 
 namespace aztec3::circuits::rollup::components {
+NT::fr calculate_empty_tree_root(size_t depth);
 std::array<fr, 2> compute_calldata_hash(std::array<abis::PreviousRollupData<NT>, 2> previous_rollup_data);
 void assert_prev_rollups_follow_on_from_each_other(DummyComposer& composer,
                                                    BaseOrMergeRollupPublicInputs const& left,
diff --git a/circuits/cpp/src/aztec3/circuits/rollup/root/.test.cpp b/circuits/cpp/src/aztec3/circuits/rollup/root/.test.cpp
index ed2dfa6ce73..ecef5951bea 100644
--- a/circuits/cpp/src/aztec3/circuits/rollup/root/.test.cpp
+++ b/circuits/cpp/src/aztec3/circuits/rollup/root/.test.cpp
@@ -54,7 +54,9 @@ using aztec3::circuits::abis::PreviousKernelData;
 
 
 // using aztec3::circuits::mock::mock_circuit;
+using aztec3::circuits::rollup::test_utils::utils::compare_field_hash_to_expected;
 using aztec3::circuits::rollup::test_utils::utils::get_empty_kernel;
+using aztec3::circuits::rollup::test_utils::utils::get_empty_l1_to_l2_messages;
 using aztec3::circuits::rollup::test_utils::utils::get_root_rollup_inputs;
 using aztec3::circuits::rollup::test_utils::utils::set_kernel_commitments;
 // using aztec3::circuits::mock::mock_kernel_inputs;
@@ -71,7 +73,7 @@ using aztec3::circuits::rollup::native_root_rollup::RootRollupPublicInputs;
 
 using aztec3::circuits::abis::NewContractData;
 
-using MemoryTree = proof_system::plonk::stdlib::merkle_tree::MemoryTree;
+using MemoryTree = stdlib::merkle_tree::MemoryTree;
 using KernelData = aztec3::circuits::abis::PreviousKernelData<NT>;
 }  // namespace
 
@@ -139,8 +141,11 @@ class root_rollup_tests : public ::testing::Test {
     }
 };
 
-TEST_F(root_rollup_tests, native_calldata_hash_empty_blocks)
+TEST_F(root_rollup_tests, native_check_block_hashes_empty_blocks)
 {
+    MemoryTree const data_tree = MemoryTree(PRIVATE_DATA_TREE_HEIGHT);
+
+    // calculate calldata hash
     std::vector<uint8_t> const zero_bytes_vec(704, 0);
     auto call_data_hash_inner = sha256::sha256(zero_bytes_vec);
 
@@ -152,31 +157,33 @@ TEST_F(root_rollup_tests, native_calldata_hash_empty_blocks)
 
     std::vector<uint8_t> const calldata_hash_input_bytes_vec(hash_input.begin(), hash_input.end());
 
-    auto hash = sha256::sha256(calldata_hash_input_bytes_vec);
+    auto calldata_hash = sha256::sha256(calldata_hash_input_bytes_vec);
+
+    // get messages
+    std::array<fr, NUMBER_OF_L1_L2_MESSAGES_PER_ROLLUP> const l1_to_l2_messages = get_empty_l1_to_l2_messages();
+
+    // hash messages
+    std::vector<uint8_t> const messages_hash_input_bytes_vec(NUMBER_OF_L1_L2_MESSAGES_PER_ROLLUP * 32, 0);
+    auto messages_hash = sha256::sha256(messages_hash_input_bytes_vec);
 
     utils::DummyComposer composer = utils::DummyComposer();
     std::array<KernelData, 4> const kernels = {
         get_empty_kernel(), get_empty_kernel(), get_empty_kernel(), get_empty_kernel()
     };
-    RootRollupInputs inputs = get_root_rollup_inputs(composer, kernels);
+
+    RootRollupInputs inputs = get_root_rollup_inputs(composer, kernels, l1_to_l2_messages);
     RootRollupPublicInputs outputs =
         aztec3::circuits::rollup::native_root_rollup::root_rollup_circuit(composer, inputs);
 
-    std::array<fr, 2> calldata_hash_fr = outputs.calldata_hash;
-    auto high_buffer = calldata_hash_fr[0].to_buffer();
-    auto low_buffer = calldata_hash_fr[1].to_buffer();
+    // check calldata hash
+    ASSERT_TRUE(compare_field_hash_to_expected(outputs.calldata_hash, calldata_hash));
+    // Check messages hash
+    ASSERT_TRUE(compare_field_hash_to_expected(outputs.l1_to_l2_messages_hash, messages_hash));
 
-    std::array<uint8_t, 32> calldata_hash;
-    for (uint8_t i = 0; i < 16; ++i) {
-        calldata_hash[i] = high_buffer[16 + i];
-        calldata_hash[16 + i] = low_buffer[16 + i];
-    }
-
-    ASSERT_EQ(hash, calldata_hash);
     EXPECT_FALSE(composer.failed());
 
     // Expected hash of public inputs for an empty L2 block. Also used in the contract tests.
-    fr const expected_hash = uint256_t("0013b2202a3e48b039cda7eef0976060d86e610d77fc9bb8cd5b0f1b561df48c");
+    fr const expected_hash = uint256_t("11840efc30e9fcbdd0aae30da2a5b441132420b4f0cc4ffd6bdc41888845f775");
     ASSERT_EQ(outputs.hash(), expected_hash);
 
     run_cbind(inputs, outputs, true);
@@ -190,14 +197,18 @@ TEST_F(root_rollup_tests, native_root_missing_nullifier_logic)
     MemoryTree contract_tree = MemoryTree(CONTRACT_TREE_HEIGHT);
     MemoryTree historic_data_tree = MemoryTree(PRIVATE_DATA_TREE_ROOTS_TREE_HEIGHT);
     MemoryTree historic_contract_tree = MemoryTree(CONTRACT_TREE_ROOTS_TREE_HEIGHT);
+    MemoryTree l1_to_l2_messages_tree = MemoryTree(L1_TO_L2_MSG_TREE_HEIGHT);
+    MemoryTree historic_l1_to_l2_tree = MemoryTree(L1_TO_L2_MSG_TREE_ROOTS_TREE_HEIGHT);
 
     // Historic trees are initialised with an empty root at position 0.
     historic_data_tree.update_element(0, data_tree.root());
     historic_contract_tree.update_element(0, contract_tree.root());
+    historic_l1_to_l2_tree.update_element(0, l1_to_l2_messages_tree.root());
 
     std::array<KernelData, 4> kernels = {
         get_empty_kernel(), get_empty_kernel(), get_empty_kernel(), get_empty_kernel()
     };
+    std::array<fr, NUMBER_OF_L1_L2_MESSAGES_PER_ROLLUP> l1_to_l2_messages = get_empty_l1_to_l2_messages();
 
     // Create commitments
     for (uint8_t kernel_j = 0; kernel_j < 4; kernel_j++) {
@@ -230,24 +241,41 @@ TEST_F(root_rollup_tests, native_root_missing_nullifier_logic)
     contract_tree.update_element(2, contract_leaf);
     kernels[2].public_inputs.end.new_contracts[0] = new_contract;
 
-    // The start historic data snapshot
+    // l1 to l2 messages snapshot
+    AppendOnlyTreeSnapshot<NT> const start_l1_to_l2_messages_tree_snapshot = { .root = l1_to_l2_messages_tree.root(),
+                                                                               .next_available_leaf_index = 0 };
+
+    // The start historic data snapshots
     AppendOnlyTreeSnapshot<NT> const start_historic_data_tree_snapshot = { .root = historic_data_tree.root(),
                                                                            .next_available_leaf_index = 1 };
     AppendOnlyTreeSnapshot<NT> const start_historic_contract_tree_snapshot = { .root = historic_contract_tree.root(),
                                                                                .next_available_leaf_index = 1 };
+    AppendOnlyTreeSnapshot<NT> const start_historic_l1_to_l2_tree_snapshot = { .root = historic_l1_to_l2_tree.root(),
+                                                                               .next_available_leaf_index = 1 };
+
+    // Create 16 empty l1 to l2 messages, and update the l1_to_l2 messages tree
+    for (size_t i = 0; i < l1_to_l2_messages.size(); i++) {
+        l1_to_l2_messages_tree.update_element(i, l1_to_l2_messages[i]);
+    }
 
     // Insert the newest data root into the historic tree
     historic_data_tree.update_element(1, data_tree.root());
     historic_contract_tree.update_element(1, contract_tree.root());
+    historic_l1_to_l2_tree.update_element(1, l1_to_l2_messages_tree.root());
 
     // Compute the end snapshot
     AppendOnlyTreeSnapshot<NT> const end_historic_data_tree_snapshot = { .root = historic_data_tree.root(),
                                                                          .next_available_leaf_index = 2 };
     AppendOnlyTreeSnapshot<NT> const end_historic_contract_tree_snapshot = { .root = historic_contract_tree.root(),
                                                                              .next_available_leaf_index = 2 };
+    AppendOnlyTreeSnapshot<NT> const end_historic_l1_to_l2_tree_snapshot = { .root = historic_l1_to_l2_tree.root(),
+                                                                             .next_available_leaf_index = 2 };
+    AppendOnlyTreeSnapshot<NT> const end_l1_to_l2_messages_tree_snapshot = { .root = l1_to_l2_messages_tree.root(),
+                                                                             .next_available_leaf_index =
+                                                                                 NUMBER_OF_L1_L2_MESSAGES_PER_ROLLUP };
 
-    RootRollupInputs rootRollupInputs = get_root_rollup_inputs(composer, kernels);
-    RootRollupPublicInputs const outputs =
+    RootRollupInputs rootRollupInputs = get_root_rollup_inputs(composer, kernels, l1_to_l2_messages);
+    RootRollupPublicInputs outputs =
         aztec3::circuits::rollup::native_root_rollup::root_rollup_circuit(composer, rootRollupInputs);
 
     // Check private data trees
@@ -286,7 +314,18 @@ TEST_F(root_rollup_tests, native_root_missing_nullifier_logic)
     ASSERT_EQ(outputs.start_tree_of_historic_contract_tree_roots_snapshot, start_historic_contract_tree_snapshot);
     ASSERT_EQ(outputs.end_tree_of_historic_contract_tree_roots_snapshot, end_historic_contract_tree_snapshot);
 
+    // Check historic l1 to l2 messages trees
+    ASSERT_EQ(outputs.start_tree_of_historic_l1_to_l2_messages_tree_roots_snapshot,
+              start_historic_l1_to_l2_tree_snapshot);
+    ASSERT_EQ(outputs.end_tree_of_historic_l1_to_l2_messages_tree_roots_snapshot, end_historic_l1_to_l2_tree_snapshot);
+
+    // Check l1 to l2 messages trees
+    ASSERT_EQ(outputs.start_l1_to_l2_messages_tree_snapshot, start_l1_to_l2_messages_tree_snapshot);
+    ASSERT_EQ(outputs.end_l1_to_l2_messages_tree_snapshot, end_l1_to_l2_messages_tree_snapshot);
+
     EXPECT_FALSE(composer.failed());
+
+    run_cbind(rootRollupInputs, outputs, true);
 }
 
 }  // namespace aztec3::circuits::rollup::root::native_root_rollup_circuit
\ No newline at end of file
diff --git a/circuits/cpp/src/aztec3/circuits/rollup/root/init.hpp b/circuits/cpp/src/aztec3/circuits/rollup/root/init.hpp
index 2a15f32de12..efb914db422 100644
--- a/circuits/cpp/src/aztec3/circuits/rollup/root/init.hpp
+++ b/circuits/cpp/src/aztec3/circuits/rollup/root/init.hpp
@@ -6,12 +6,12 @@
 #include "aztec3/circuits/abis/rollup/root/root_rollup_inputs.hpp"
 #include "aztec3/circuits/abis/rollup/root/root_rollup_public_inputs.hpp"
 #include "aztec3/utils/dummy_composer.hpp"
-#include <aztec3/circuits/abis/private_circuit_public_inputs.hpp>
 #include <aztec3/circuits/recursion/aggregator.hpp>
 #include <aztec3/utils/types/circuit_types.hpp>
 #include <aztec3/utils/types/convert.hpp>
 #include <aztec3/utils/types/native_types.hpp>
 
+#include "barretenberg/stdlib/merkle_tree/memory_tree.hpp"
 #include <barretenberg/crypto/sha256/sha256.hpp>
 
 namespace aztec3::circuits::rollup::native_root_rollup {
@@ -26,4 +26,6 @@ using RootRollupPublicInputs = abis::RootRollupPublicInputs<NT>;
 
 using Aggregator = aztec3::circuits::recursion::Aggregator;
 
-}  // namespace aztec3::circuits::rollup::native_root_rollup
\ No newline at end of file
+using MerkleTree = stdlib::merkle_tree::MemoryTree;
+
+}  // namespace aztec3::circuits::rollup::native_root_rollup
diff --git a/circuits/cpp/src/aztec3/circuits/rollup/root/native_root_rollup_circuit.cpp b/circuits/cpp/src/aztec3/circuits/rollup/root/native_root_rollup_circuit.cpp
index 64e0bd981f3..536f805f70a 100644
--- a/circuits/cpp/src/aztec3/circuits/rollup/root/native_root_rollup_circuit.cpp
+++ b/circuits/cpp/src/aztec3/circuits/rollup/root/native_root_rollup_circuit.cpp
@@ -28,6 +28,55 @@ namespace aztec3::circuits::rollup::native_root_rollup {
 
 // Access Native types through NT namespace
 
+/**
+ * @brief Calculates the messages subtree from the leaves array
+ * @param leaves
+ * @return root
+ */
+NT::fr calculate_subtree(std::array<NT::fr, NUMBER_OF_L1_L2_MESSAGES_PER_ROLLUP> leaves)
+{
+    MerkleTree merkle_tree = MerkleTree(L1_TO_L2_MSG_SUBTREE_DEPTH);
+
+    for (size_t i = 0; i < NUMBER_OF_L1_L2_MESSAGES_PER_ROLLUP; i++) {
+        merkle_tree.update_element(i, leaves[i]);
+    }
+    return merkle_tree.root();
+}
+
+/**
+ * @brief Computes the messages hash from the leaves array
+ * @param leaves
+ * @param return - hash split into two field elements
+ */
+std::array<NT::fr, 2> compute_messages_hash(std::array<NT::fr, NUMBER_OF_L1_L2_MESSAGES_PER_ROLLUP> leaves)
+{
+    // convert vector of field elements into uint_8
+    std::array<uint8_t, 32 * NUMBER_OF_L1_L2_MESSAGES_PER_ROLLUP> messages_hash_input_bytes;
+    for (size_t i = 0; i < NUMBER_OF_L1_L2_MESSAGES_PER_ROLLUP; i++) {
+        auto bytes = leaves[i].to_buffer();
+        for (size_t j = 0; j < 32; j++) {
+            messages_hash_input_bytes[i * 32 + j] = bytes[j];
+        }
+    }
+
+    std::vector<uint8_t> const messages_hash_input_bytes_vec(messages_hash_input_bytes.begin(),
+                                                             messages_hash_input_bytes.end());
+    auto h = sha256::sha256(messages_hash_input_bytes_vec);
+
+    std::array<uint8_t, 32> buf_1;
+    std::array<uint8_t, 32> buf_2;
+    for (uint8_t i = 0; i < 16; i++) {
+        buf_1[i] = 0;
+        buf_1[16 + i] = h[i];
+        buf_2[i] = 0;
+        buf_2[16 + i] = h[i + 16];
+    }
+    auto high = fr::serialize_from_buffer(buf_1.data());
+    auto low = fr::serialize_from_buffer(buf_2.data());
+
+    return { high, low };
+}
+
 RootRollupPublicInputs root_rollup_circuit(DummyComposer& composer, RootRollupInputs const& rootRollupInputs)
 {
     // TODO: Verify the previous rollup proofs
@@ -63,6 +112,31 @@ RootRollupPublicInputs root_rollup_circuit(DummyComposer& composer, RootRollupIn
                                                     0,
                                                     "historic contract tree roots insertion");
 
+    // Check correct l1 to l2 tree given
+    // Compute subtree inserting l1 to l2 messages
+    auto l1_to_l2_subtree_root = calculate_subtree(rootRollupInputs.l1_to_l2_messages);
+
+    // // Insert subtree into the l1 to l2 data tree
+    const auto empty_l1_to_l2_subtree_root = components::calculate_empty_tree_root(L1_TO_L2_MSG_SUBTREE_DEPTH);
+    auto new_l1_to_l2_messages_tree_snapshot =
+        components::insert_subtree_to_snapshot_tree(composer,
+                                                    rootRollupInputs.start_l1_to_l2_message_tree_snapshot,
+                                                    rootRollupInputs.new_l1_to_l2_message_tree_root_sibling_path,
+                                                    empty_l1_to_l2_subtree_root,
+                                                    l1_to_l2_subtree_root,
+                                                    L1_TO_L2_MSG_SUBTREE_INCLUSION_CHECK_DEPTH,
+                                                    "l1 to l2 message tree insertion");
+
+    // Update the historic l1 to l2 data tree
+    auto end_l1_to_l2_data_roots_tree_snapshot = components::insert_subtree_to_snapshot_tree(
+        composer,
+        rootRollupInputs.start_historic_tree_l1_to_l2_message_tree_roots_snapshot,
+        rootRollupInputs.new_historic_l1_to_l2_message_roots_tree_sibling_path,
+        fr::zero(),
+        new_l1_to_l2_messages_tree_snapshot.root,
+        0,
+        "historic l1 to l2 message tree roots insertion");
+
     RootRollupPublicInputs public_inputs = {
         .end_aggregation_object = aggregation_object,
         .start_private_data_tree_snapshot = left.start_private_data_tree_snapshot,
@@ -79,7 +153,13 @@ RootRollupPublicInputs root_rollup_circuit(DummyComposer& composer, RootRollupIn
         .start_tree_of_historic_contract_tree_roots_snapshot =
             left.constants.start_tree_of_historic_contract_tree_roots_snapshot,
         .end_tree_of_historic_contract_tree_roots_snapshot = end_tree_of_historic_contract_tree_roots_snapshot,
+        .start_l1_to_l2_messages_tree_snapshot = rootRollupInputs.start_l1_to_l2_message_tree_snapshot,
+        .end_l1_to_l2_messages_tree_snapshot = new_l1_to_l2_messages_tree_snapshot,
+        .start_tree_of_historic_l1_to_l2_messages_tree_roots_snapshot =
+            rootRollupInputs.start_historic_tree_l1_to_l2_message_tree_roots_snapshot,
+        .end_tree_of_historic_l1_to_l2_messages_tree_roots_snapshot = end_l1_to_l2_data_roots_tree_snapshot,
         .calldata_hash = components::compute_calldata_hash(rootRollupInputs.previous_rollup_data),
+        .l1_to_l2_messages_hash = compute_messages_hash(rootRollupInputs.l1_to_l2_messages)
     };
 
     return public_inputs;
diff --git a/circuits/cpp/src/aztec3/circuits/rollup/test_utils/utils.cpp b/circuits/cpp/src/aztec3/circuits/rollup/test_utils/utils.cpp
index ac3aa2ece62..714f8eca986 100644
--- a/circuits/cpp/src/aztec3/circuits/rollup/test_utils/utils.cpp
+++ b/circuits/cpp/src/aztec3/circuits/rollup/test_utils/utils.cpp
@@ -56,6 +56,12 @@ KernelData get_empty_kernel()
     return dummy_previous_kernel();
 }
 
+std::array<fr, NUMBER_OF_L1_L2_MESSAGES_PER_ROLLUP> get_empty_l1_to_l2_messages()
+{
+    std::array<fr, NUMBER_OF_L1_L2_MESSAGES_PER_ROLLUP> l1_to_l2_messages = { 0 };
+    return l1_to_l2_messages;
+}
+
 void set_kernel_nullifiers(KernelData& kernel_data, std::array<fr, KERNEL_NEW_NULLIFIERS_LENGTH> new_nullifiers)
 {
     for (size_t i = 0; i < KERNEL_NEW_NULLIFIERS_LENGTH; i++) {
@@ -298,7 +304,9 @@ MergeRollupInputs get_merge_rollup_inputs(utils::DummyComposer& composer, std::a
     return inputs;
 }
 
-RootRollupInputs get_root_rollup_inputs(utils::DummyComposer& composer, std::array<KernelData, 4> kernel_data)
+RootRollupInputs get_root_rollup_inputs(utils::DummyComposer& composer,
+                                        std::array<KernelData, 4> kernel_data,
+                                        std::array<fr, NUMBER_OF_L1_L2_MESSAGES_PER_ROLLUP> l1_to_l2_messages)
 {
     MerkleTree historic_private_data_tree = MerkleTree(PRIVATE_DATA_TREE_ROOTS_TREE_HEIGHT);
     MerkleTree historic_contract_tree = MerkleTree(CONTRACT_TREE_ROOTS_TREE_HEIGHT);
@@ -306,21 +314,42 @@ RootRollupInputs get_root_rollup_inputs(utils::DummyComposer& composer, std::arr
 
     MerkleTree const private_data_tree = MerkleTree(PRIVATE_DATA_TREE_HEIGHT);
     MerkleTree const contract_tree = MerkleTree(CONTRACT_TREE_HEIGHT);
+    MerkleTree l1_to_l2_msg_tree = MerkleTree(L1_TO_L2_MSG_TREE_HEIGHT);
 
     // Historic trees are initialised with an empty root at position 0.
     historic_private_data_tree.update_element(0, private_data_tree.root());
     historic_contract_tree.update_element(0, contract_tree.root());
-    historic_l1_to_l2_msg_tree.update_element(0, MerkleTree(L1_TO_L2_MSG_TREE_HEIGHT).root());
+    historic_l1_to_l2_msg_tree.update_element(0, l1_to_l2_msg_tree.root());
 
     auto historic_data_sibling_path =
         get_sibling_path<PRIVATE_DATA_TREE_ROOTS_TREE_HEIGHT>(historic_private_data_tree, 1, 0);
     auto historic_contract_sibling_path =
         get_sibling_path<CONTRACT_TREE_ROOTS_TREE_HEIGHT>(historic_contract_tree, 1, 0);
+    auto historic_l1_to_l2_msg_sibling_path =
+        get_sibling_path<L1_TO_L2_MSG_TREE_ROOTS_TREE_HEIGHT>(historic_l1_to_l2_msg_tree, 1, 0);
+    auto l1_to_l2_tree_sibling_path = get_sibling_path<L1_TO_L2_MSG_SUBTREE_INCLUSION_CHECK_DEPTH>(
+        l1_to_l2_msg_tree, 0, L1_TO_L2_MSG_SUBTREE_INCLUSION_CHECK_DEPTH);
+
+    // l1_to_l2_message tree snapshots
+    AppendOnlyTreeSnapshot const start_l1_to_l2_msg_tree_snapshot = {
+        .root = l1_to_l2_msg_tree.root(),
+        .next_available_leaf_index = 0,
+    };
+    AppendOnlyTreeSnapshot const start_historic_tree_l1_to_l2_message_tree_roots_snapshot = {
+        .root = historic_l1_to_l2_msg_tree.root(),
+        .next_available_leaf_index = 1,
+    };
 
     RootRollupInputs rootRollupInputs = {
         .previous_rollup_data = get_previous_rollup_data(composer, std::move(kernel_data)),
         .new_historic_private_data_tree_root_sibling_path = historic_data_sibling_path,
         .new_historic_contract_tree_root_sibling_path = historic_contract_sibling_path,
+        .l1_to_l2_messages = l1_to_l2_messages,
+        .new_l1_to_l2_message_tree_root_sibling_path = l1_to_l2_tree_sibling_path,
+        .new_historic_l1_to_l2_message_roots_tree_sibling_path = historic_l1_to_l2_msg_sibling_path,
+        .start_l1_to_l2_message_tree_snapshot = start_l1_to_l2_msg_tree_snapshot,
+        .start_historic_tree_l1_to_l2_message_tree_roots_snapshot =
+            start_historic_tree_l1_to_l2_message_tree_roots_snapshot,
     };
     return rootRollupInputs;
 }
@@ -472,4 +501,27 @@ nullifier_tree_testing_values generate_nullifier_tree_testing_values_explicit(
     return std::make_tuple(rollupInputs, nullifier_tree_start_snapshot, nullifier_tree_end_snapshot);
 }
 
-}  // namespace aztec3::circuits::rollup::test_utils::utils
\ No newline at end of file
+/**
+ * @brief Compares a hash calculated within a circuit (made up of two field elements) against
+ *        one generated natively, (32 bytes) and checks if they match
+ *
+ * @param field_hash
+ * @param expected_hash
+ * @return true
+ * @return false
+ */
+bool compare_field_hash_to_expected(std::array<fr, 2> field_hash, std::array<uint8_t, 32> expected_hash)
+{
+    auto high_buffer = field_hash[0].to_buffer();
+    auto low_buffer = field_hash[1].to_buffer();
+
+    std::array<uint8_t, 32> field_expanded_hash;
+    for (uint8_t i = 0; i < 16; ++i) {
+        field_expanded_hash[i] = high_buffer[16 + i];
+        field_expanded_hash[16 + i] = low_buffer[16 + i];
+    }
+
+    return expected_hash == field_expanded_hash;
+}
+
+}  // namespace aztec3::circuits::rollup::test_utils::utils
diff --git a/circuits/cpp/src/aztec3/circuits/rollup/test_utils/utils.hpp b/circuits/cpp/src/aztec3/circuits/rollup/test_utils/utils.hpp
index 525bf17192e..dd2a7b8c3f9 100644
--- a/circuits/cpp/src/aztec3/circuits/rollup/test_utils/utils.hpp
+++ b/circuits/cpp/src/aztec3/circuits/rollup/test_utils/utils.hpp
@@ -3,6 +3,7 @@
 #include "nullifier_tree_testing_harness.hpp"
 
 #include "aztec3/circuits/abis/public_data_transition.hpp"
+#include "aztec3/constants.hpp"
 
 #include "barretenberg/numeric/uint256/uint256.hpp"
 
@@ -88,6 +89,8 @@ nullifier_tree_testing_values generate_nullifier_tree_testing_values(BaseRollupI
                                                                      size_t starting_insertion_value,
                                                                      size_t spacing);
 
+std::array<fr, NUMBER_OF_L1_L2_MESSAGES_PER_ROLLUP> get_empty_l1_to_l2_messages();
+
 nullifier_tree_testing_values generate_nullifier_tree_testing_values(
     BaseRollupInputs inputs, std::array<fr, KERNEL_NEW_NULLIFIERS_LENGTH * 2> new_nullifiers, size_t spacing);
 
@@ -95,7 +98,9 @@ NullifierMemoryTreeTestingHarness get_initial_nullifier_tree(const std::vector<f
 
 KernelData get_empty_kernel();
 
-RootRollupInputs get_root_rollup_inputs(utils::DummyComposer& composer, std::array<KernelData, 4> kernel_data);
+RootRollupInputs get_root_rollup_inputs(utils::DummyComposer& composer,
+                                        std::array<KernelData, 4> kernel_data,
+                                        std::array<fr, NUMBER_OF_L1_L2_MESSAGES_PER_ROLLUP> l1_to_l2_messages);
 
 void set_kernel_commitments(KernelData& kernel_data, std::array<fr, KERNEL_NEW_COMMITMENTS_LENGTH> new_commitments);
 
@@ -120,4 +125,6 @@ inline abis::PublicDataRead<NT> make_public_read(fr leaf_index, fr value)
     };
 }
 
-}  // namespace aztec3::circuits::rollup::test_utils::utils
\ No newline at end of file
+bool compare_field_hash_to_expected(std::array<fr, 2> field_hash, std::array<uint8_t, 32> expected_hash);
+
+}  // namespace aztec3::circuits::rollup::test_utils::utils
diff --git a/circuits/cpp/src/aztec3/constants.hpp b/circuits/cpp/src/aztec3/constants.hpp
index edcc1460dc1..3bf6ed53269 100644
--- a/circuits/cpp/src/aztec3/constants.hpp
+++ b/circuits/cpp/src/aztec3/constants.hpp
@@ -43,6 +43,11 @@ constexpr size_t PRIVATE_DATA_SUBTREE_INCLUSION_CHECK_DEPTH = PRIVATE_DATA_TREE_
 constexpr size_t NULLIFIER_SUBTREE_DEPTH = 3;
 constexpr size_t NULLIFIER_SUBTREE_INCLUSION_CHECK_DEPTH = NULLIFIER_TREE_HEIGHT - NULLIFIER_SUBTREE_DEPTH;
 
+// NUMBER_OF_L1_L2_MESSAGES_PER_ROLLUP must equal 2^L1_TO_L2_MSG_SUBTREE_DEPTH for subtree insertions.
+constexpr size_t L1_TO_L2_MSG_SUBTREE_DEPTH = 4;
+constexpr size_t NUMBER_OF_L1_L2_MESSAGES_PER_ROLLUP = 16;
+constexpr size_t L1_TO_L2_MSG_SUBTREE_INCLUSION_CHECK_DEPTH = L1_TO_L2_MSG_TREE_HEIGHT - L1_TO_L2_MSG_SUBTREE_DEPTH;
+
 constexpr size_t PRIVATE_DATA_TREE_ROOTS_TREE_HEIGHT = 8;
 constexpr size_t CONTRACT_TREE_ROOTS_TREE_HEIGHT = 8;
 constexpr size_t L1_TO_L2_MSG_TREE_ROOTS_TREE_HEIGHT = 8;
@@ -50,6 +55,7 @@ constexpr size_t ROLLUP_VK_TREE_HEIGHT = 8;  // TODO: update
 
 constexpr size_t FUNCTION_SELECTOR_NUM_BYTES = 4;  // must be <= 31
 
+
 // Enumerate the hash_indices which are used for pedersen hashing
 // Start from 1 to avoid the default generators.
 enum GeneratorIndex {
diff --git a/l1-contracts/src/core/Decoder.sol b/l1-contracts/src/core/Decoder.sol
index 950cab912da..99947884153 100644
--- a/l1-contracts/src/core/Decoder.sol
+++ b/l1-contracts/src/core/Decoder.sol
@@ -27,34 +27,45 @@ pragma solidity >=0.8.18;
  *  | 0x94                     | 0x20       | startTreeOfHistoricContractTreeRootsSnapshot.root
  *  | 0xb4                     | 0x04       | startTreeOfHistoricContractTreeRootsSnapshot.nextAvailableLeafIndex
  *  | 0xb8                     | 0x20       | startPublicDataTreeRoot
- *  | 0xd8                     | 0x20       | endPrivateDataTreeSnapshot.root
- *  | 0xf8                     | 0x04       | endPrivateDataTreeSnapshot.nextAvailableLeafIndex
- *  | 0xfc                     | 0x20       | endNullifierTreeSnapshot.root
- *  | 0x11c                    | 0x04       | endNullifierTreeSnapshot.nextAvailableLeafIndex
- *  | 0x120                    | 0x20       | endContractTreeSnapshot.root
- *  | 0x140                    | 0x04       | endContractTreeSnapshot.nextAvailableLeafIndex
- *  | 0x144                    | 0x20       | endTreeOfHistoricPrivateDataTreeRootsSnapshot.root
- *  | 0x164                    | 0x04       | endTreeOfHistoricPrivateDataTreeRootsSnapshot.nextAvailableLeafIndex
- *  | 0x168                    | 0x20       | endTreeOfHistoricContractTreeRootsSnapshot.root
- *  | 0x188                    | 0x04       | endTreeOfHistoricContractTreeRootsSnapshot.nextAvailableLeafIndex
- *  | 0x18c                    | 0x20       | endPublicDataTreeRoot
- *  | 0x1ac                    | 0x04       | len(newCommitments) denoted a
- *  | 0x1b0                    | a          | newCommitments (each element 32 bytes)
- *  | 0x1b0 + a                | 0x04       | len(newNullifiers) denoted b
- *  | 0x1b4 + a                | b          | newNullifiers (each element 32 bytes)
- *  | 0x1b4 + a + b            | 0x04       | len(newPublicDataWrites) denoted c
- *  | 0x1b8 + a + b            | c          | newPublicDataWrites (each element 64 bytes)
- *  | 0x1b8 + a + b + c        | 0x04       | len(newContracts) denoted d
- *  | 0x1bc + a + b + c        | v          | newContracts (each element 32 bytes)
- *  | 0x1bc + a + b + c + d    | v          | newContractData (each element 52 bytes)
+ *  | 0xd8                     | 0x20       | startL1ToL2MessagesTreeSnapshot.root
+ *  | 0xf8                     | 0x04       | startL1ToL2MessagesTreeSnapshot.nextAvailableLeafIndex
+ *  | 0xfc                     | 0x20       | startTreeOfHistoricL1ToL2MessagesTreeRootsSnapshot.root
+ *  | 0x11c                    | 0x04       | startTreeOfHistoricL1ToL2MessagesTreeRootsSnapshot.nextAvailableLeafIndex
+ *  | 0x120                    | 0x20       | endPrivateDataTreeSnapshot.root
+ *  | 0x140                    | 0x04       | endPrivateDataTreeSnapshot.nextAvailableLeafIndex
+ *  | 0x144                    | 0x20       | endNullifierTreeSnapshot.root
+ *  | 0x164                    | 0x04       | endNullifierTreeSnapshot.nextAvailableLeafIndex
+ *  | 0x168                    | 0x20       | endContractTreeSnapshot.root
+ *  | 0x188                    | 0x04       | endContractTreeSnapshot.nextAvailableLeafIndex
+ *  | 0x18c                    | 0x20       | endTreeOfHistoricPrivateDataTreeRootsSnapshot.root
+ *  | 0x1ac                    | 0x04       | endTreeOfHistoricPrivateDataTreeRootsSnapshot.nextAvailableLeafIndex
+ *  | 0x1b0                    | 0x20       | endTreeOfHistoricContractTreeRootsSnapshot.root
+ *  | 0x1d0                    | 0x04       | endTreeOfHistoricContractTreeRootsSnapshot.nextAvailableLeafIndex
+ *  | 0x1d4                    | 0x20       | endPublicDataTreeRoot
+ *  | 0x1f4                    | 0x20       | endL1ToL2MessagesTreeSnapshot.root
+ *  | 0x214                    | 0x04       | endL1ToL2MessagesTreeSnapshot.nextAvailableLeafIndex
+ *  | 0x218                    | 0x20       | endTreeOfHistoricL1ToL2MessagesTreeRootsSnapshot.root
+ *  | 0x238                    | 0x04       | endTreeOfHistoricL1ToL2MessagesTreeRootsSnapshot.nextAvailableLeafIndex
+ *  | 0x23c                    | 0x04       | len(newCommitments) denoted x
+ *  | 0x240                    | x          | newCommits
+ *  | 0x240 + x                | 0x04       | len(newNullifiers) denoted y
+ *  | 0x244 + x                | y          | newNullifiers
+ *  | 0x244 + a + b            | 0x04       | len(newPublicDataWrites) denoted c
+ *  | 0x248 + a + b            | c          | newPublicDataWrites (each element 64 bytes)
+ *  | 0x248 + a + b + c        | 0x04       | len(newContracts) denoted d
+ *  | 0x24c + a + b + c        | d          | newContracts (each element 32 bytes)
+ *  | 0x24c + a + b + c + d    | d          | newContractData (each element 52 bytes)
+ *  | 0x24c + a + b + c + d    | 0x04       | len(l1ToL2Messages) denoted e
+ *  | 0x250 + a + b + c + d + e| e          | l1ToL2Messages
  *  |---                       |---         | ---
- * TODO: a,b,c,d are number of elements and not bytes, need to be multiplied by the length of the elements.
+ * TODO: a,b,c,d,e are number of elements and not bytes, need to be multiplied by the length of the elements.
  */
 contract Decoder {
   uint256 internal constant COMMITMENTS_PER_KERNEL = 4;
   uint256 internal constant NULLIFIERS_PER_KERNEL = 4;
   uint256 internal constant PUBLIC_DATA_WRITES_PER_KERNEL = 4;
   uint256 internal constant CONTRACTS_PER_KERNEL = 1;
+  uint256 internal constant L1_TO_L2_MESSAGES_PER_ROLLUP = 16;
 
   // Prime field order
   uint256 internal constant P =
@@ -82,26 +93,31 @@ contract Decoder {
     // Note, for startStateHash to match the storage, the l2 block number must be new - 1.
     // Only jumping 1 block at a time.
     startStateHash = _computeStateHash(l2BlockNumber - 1, 0x4, _l2Block);
-    endStateHash = _computeStateHash(l2BlockNumber, 0xd8, _l2Block);
+    endStateHash = _computeStateHash(l2BlockNumber, 0x120, _l2Block);
     publicInputHash = _computePublicInputsHash(_l2Block);
   }
 
   /**
    * Computes a hash of the public inputs from the calldata
    * @param _l2Block - The L2 block calldata.
-   * @return sha256(header[0x4: 0x1ac], diffRoot)
+   * @return sha256(header[0x4: 0x23c], diffRoot, l1Tol2MessagesHash)
    */
   function _computePublicInputsHash(bytes calldata _l2Block) internal pure returns (bytes32) {
-    // header size - block number size + one value for the diffRoot
-    uint256 size = 0x1ac - 0x04 + 0x20;
+    // header size - block number size + one value for the diffRoot + one value for l1ToL2MessagesHash
+    uint256 size = 0x23c - 0x04 + 0x20 + 0x20;
+
+    // Compute the public inputs hash
     bytes memory temp = new bytes(size);
     assembly {
       calldatacopy(add(temp, 0x20), add(_l2Block.offset, 0x04), size)
     }
 
-    bytes32 diffRoot = _computeDiffRoot(_l2Block);
+    // Diff root
+    (bytes32 diffRoot, bytes32 l1ToL2messagesHash) = _computeDiffRootAndMessagesHash(_l2Block);
     assembly {
-      mstore(add(temp, add(0x20, sub(0x1ac, 0x04))), diffRoot)
+      let endOfTreesData := sub(0x23c, 0x04)
+      mstore(add(temp, add(0x20, endOfTreesData)), diffRoot)
+      mstore(add(temp, add(0x40, endOfTreesData)), l1ToL2messagesHash)
     }
 
     return bytes32(uint256(sha256(temp)) % P);
@@ -130,7 +146,7 @@ contract Decoder {
     pure
     returns (bytes32)
   {
-    bytes memory temp = new bytes(0xd8);
+    bytes memory temp = new bytes(0x120);
 
     assembly {
       mstore8(add(temp, 0x20), shr(24, _l2BlockNumber))
@@ -140,30 +156,45 @@ contract Decoder {
     }
     assembly {
       // Copy header elements (not including block number) for start or end (size 0xd4)
-      calldatacopy(add(temp, 0x24), add(_l2Block.offset, _offset), 0xd4)
+      calldatacopy(add(temp, 0x24), add(_l2Block.offset, _offset), 0x11c)
     }
 
     return sha256(temp);
   }
 
-  struct Vars {
+  struct ArrayLengths {
     uint256 commitmentCount;
     uint256 nullifierCount;
     uint256 dataWritesCount;
     uint256 contractCount;
+    uint256 l1Tol2MessagesCount;
+  }
+
+  struct ArrayOffsets {
+    uint256 commitmentOffset;
+    uint256 nullifierOffset;
+    uint256 publicDataOffset;
+    uint256 contractOffset;
+    uint256 contractDataOffset;
+    uint256 l1ToL2MessagesOffset;
   }
 
   /**
    * @notice Creates a "diff" tree and compute its root
    * @param _l2Block - The L2 block calldata.
-   * @return The root of the "diff" tree
    */
-  function _computeDiffRoot(bytes calldata _l2Block) internal pure returns (bytes32) {
+  function _computeDiffRootAndMessagesHash(bytes calldata _l2Block)
+    internal
+    pure
+    returns (bytes32, bytes32)
+  {
     // Find the lengths of the different inputs
-    Vars memory vars;
+    // TOOD: Naming / getting the messages root within this function is a bit weird
+    ArrayLengths memory lengths;
+    ArrayOffsets memory offsets;
     {
       assembly {
-        let offset := add(_l2Block.offset, 0x1ac)
+        let offset := add(_l2Block.offset, 0x23c)
         let commitmentCount := and(shr(224, calldataload(offset)), 0xffffffff)
         offset := add(add(offset, 0x4), mul(commitmentCount, 0x20))
         let nullifierCount := and(shr(224, calldataload(offset)), 0xffffffff)
@@ -171,110 +202,140 @@ contract Decoder {
         let dataWritesCount := and(shr(224, calldataload(offset)), 0xffffffff)
         offset := add(add(offset, 0x4), mul(nullifierCount, 0x40))
         let contractCount := and(shr(224, calldataload(offset)), 0xffffffff)
+        offset := add(add(offset, 0x4), mul(contractCount, 0x54))
+        let l1Tol2MessagesCount := and(shr(224, calldataload(offset)), 0xffffffff)
 
-        // Store it in vars
-        mstore(vars, commitmentCount)
-        mstore(add(vars, 0x20), nullifierCount)
-        mstore(add(vars, 0x40), dataWritesCount)
-        mstore(add(vars, 0x60), contractCount)
+        // Store it in lengths
+        mstore(lengths, commitmentCount)
+        mstore(add(lengths, 0x20), nullifierCount)
+        mstore(add(lengths, 0x40), dataWritesCount)
+        mstore(add(lengths, 0x60), contractCount)
+        mstore(add(lengths, 0x80), l1Tol2MessagesCount) // currently included to allow optimisation where empty messages are not included in calldata
       }
     }
 
     bytes32[] memory baseLeafs = new bytes32[](
-            vars.commitmentCount / (COMMITMENTS_PER_KERNEL * 2)
+            lengths.commitmentCount / (COMMITMENTS_PER_KERNEL * 2)
         );
 
     // Data starts after header. Look at L2 Block Data specification at the top of this file.
-    uint256 srcCommitmentOffset = 0x1b0;
-    uint256 srcNullifierOffset = srcCommitmentOffset + 0x4 + vars.commitmentCount * 0x20;
-    uint256 srcDataOffset = srcNullifierOffset + 0x4 + vars.nullifierCount * 0x20;
-    uint256 srcContractOffset = srcDataOffset + 0x4 + vars.dataWritesCount * 0x40;
-    uint256 srcContractDataOffset = srcContractOffset + vars.contractCount * 0x20;
-
-    for (uint256 i = 0; i < baseLeafs.length; i++) {
-      /**
-       * Compute the leaf to insert.
-       * Leaf_i = (
-       *    newCommitmentsKernel1,
-       *    newCommitmentsKernel2,
-       *    newNullifiersKernel1,
-       *    newNullifiersKernel2,
-       *    newPublicDataWritesKernel1,
-       *    newPublicDataWritesKernel2,
-       *    newContractLeafKernel1,
-       *    newContractLeafKernel2,
-       *    newContractDataKernel1.aztecAddress,
-       *    newContractDataKernel1.ethAddress (padded to 32 bytes)
-       *    newContractDataKernel2.aztecAddress,
-       *    newContractDataKernel2.ethAddress (padded to 32 bytes)
-       * );
-       * Note that we always read data, the l2Block (atm) must therefore include dummy or zero-notes for
-       * Zero values.
-       */
-      // Create the leaf to contain commitments (8 * 0x20) + nullifiers (8 * 0x20)
-      // + new public data writes (8 * 0x40) + contract deployments (2 * 0x60)
-      bytes memory baseLeaf = new bytes(0x4c0);
+    {
+      offsets.commitmentOffset = 0x240;
+      offsets.nullifierOffset = offsets.commitmentOffset + 0x4 + lengths.commitmentCount * 0x20;
+      offsets.publicDataOffset = offsets.nullifierOffset + 0x4 + lengths.nullifierCount * 0x20;
+      offsets.contractOffset = offsets.publicDataOffset + 0x4 + lengths.dataWritesCount * 0x40;
+      offsets.contractDataOffset = offsets.contractOffset + lengths.contractCount * 0x20;
+      offsets.l1ToL2MessagesOffset = offsets.contractDataOffset + lengths.contractCount * 0x54;
 
-      assembly {
-        let dstOffset := 0x20
-        // Adding new commitments
-        calldatacopy(
-          add(baseLeaf, dstOffset), add(_l2Block.offset, srcCommitmentOffset), mul(0x08, 0x20)
-        )
-        dstOffset := add(dstOffset, mul(0x08, 0x20))
+      for (uint256 i = 0; i < baseLeafs.length; i++) {
+        /**
+         * Compute the leaf to insert.
+         * Leaf_i = (
+         *    newCommitmentsKernel1,
+         *    newCommitmentsKernel2,
+         *    newNullifiersKernel1,
+         *    newNullifiersKernel2,
+         *    newPublicDataWritesKernel1,
+         *    newPublicDataWritesKernel2,
+         *    newContractLeafKernel1,
+         *    newContractLeafKernel2,
+         *    newContractDataKernel1.aztecAddress,
+         *    newContractDataKernel1.ethAddress (padded to 32 bytes)
+         *    newContractDataKernel2.aztecAddress,
+         *    newContractDataKernel2.ethAddress (padded to 32 bytes)
+         * );
+         * Note that we always read data, the l2Block (atm) must therefore include dummy or zero-notes for
+         * Zero values.
+         */
+        // Create the leaf to contain commitments (8 * 0x20) + nullifiers (8 * 0x20)
+        // + new public data writes (8 * 0x40) + contract deployments (2 * 0x60)
+        bytes memory baseLeaf = new bytes(0x4c0);
 
-        // Adding new nullifiers
-        calldatacopy(
-          add(baseLeaf, dstOffset), add(_l2Block.offset, srcNullifierOffset), mul(0x08, 0x20)
-        )
-        dstOffset := add(dstOffset, mul(0x08, 0x20))
+        assembly {
+          let dstOffset := 0x20
+          // Adding new commitments
+          calldatacopy(
+            add(baseLeaf, dstOffset), add(_l2Block.offset, mload(offsets)), mul(0x08, 0x20)
+          )
+          dstOffset := add(dstOffset, mul(0x08, 0x20))
 
-        // Adding new public data writes
-        calldatacopy(add(baseLeaf, dstOffset), add(_l2Block.offset, srcDataOffset), mul(0x08, 0x40))
-        dstOffset := add(dstOffset, mul(0x08, 0x40))
+          // Adding new nullifiers
+          calldatacopy(
+            add(baseLeaf, dstOffset),
+            add(_l2Block.offset, mload(add(offsets, 0x20))),
+            mul(0x08, 0x20)
+          )
+          dstOffset := add(dstOffset, mul(0x08, 0x20))
 
-        // Adding Contract Leafs
-        calldatacopy(
-          add(baseLeaf, dstOffset), add(_l2Block.offset, srcContractOffset), mul(2, 0x20)
-        )
-        dstOffset := add(dstOffset, mul(2, 0x20))
+          // Adding new public data writes
+          calldatacopy(
+            add(baseLeaf, dstOffset),
+            add(_l2Block.offset, mload(add(offsets, 0x40))),
+            mul(0x08, 0x40)
+          )
+          dstOffset := add(dstOffset, mul(0x08, 0x40))
 
-        // Kernel1.contract.aztecAddress
-        calldatacopy(add(baseLeaf, dstOffset), add(_l2Block.offset, srcContractDataOffset), 0x20)
-        dstOffset := add(dstOffset, 0x20)
+          // Adding Contract Leafs
+          calldatacopy(
+            add(baseLeaf, dstOffset), add(_l2Block.offset, mload(add(offsets, 0x60))), mul(2, 0x20)
+          )
+          dstOffset := add(dstOffset, mul(2, 0x20))
 
-        // Kernel1.contract.ethAddress padded to 32 bytes
-        // Add 12 (0xc) bytes of padding to the ethAddress
-        dstOffset := add(dstOffset, 0xc)
-        calldatacopy(
-          add(baseLeaf, dstOffset), add(_l2Block.offset, add(srcContractDataOffset, 0x20)), 0x14
-        )
-        dstOffset := add(dstOffset, 0x20)
+          // Kernel1.contract.aztecAddress
+          let contractDataOffset := mload(add(offsets, 0x80))
+          calldatacopy(add(baseLeaf, dstOffset), add(_l2Block.offset, contractDataOffset), 0x20)
+          dstOffset := add(dstOffset, 0x20)
 
-        // Kernel2.contract.aztecAddress
-        calldatacopy(
-          add(baseLeaf, dstOffset), add(_l2Block.offset, add(srcContractDataOffset, 0x34)), 0x20
-        )
-        dstOffset := add(dstOffset, 0x20)
+          // Kernel1.contract.ethAddress padded to 32 bytes
+          // Add 12 (0xc) bytes of padding to the ethAddress
+          dstOffset := add(dstOffset, 0xc)
+          calldatacopy(
+            add(baseLeaf, dstOffset), add(_l2Block.offset, add(contractDataOffset, 0x20)), 0x14
+          )
+          dstOffset := add(dstOffset, 0x20)
+
+          // Kernel2.contract.aztecAddress
+          calldatacopy(
+            add(baseLeaf, dstOffset), add(_l2Block.offset, add(contractDataOffset, 0x34)), 0x20
+          )
+          dstOffset := add(dstOffset, 0x20)
+
+          // Kernel2.contract.ethAddress padded to 32 bytes
+          // Add 12 (0xc) bytes of padding to the ethAddress
+          dstOffset := add(dstOffset, 0xc)
+          calldatacopy(
+            add(baseLeaf, dstOffset), add(_l2Block.offset, add(contractDataOffset, 0x54)), 0x14
+          )
+        }
+
+        offsets.commitmentOffset += 2 * COMMITMENTS_PER_KERNEL * 0x20;
+        offsets.nullifierOffset += 2 * NULLIFIERS_PER_KERNEL * 0x20;
+        offsets.publicDataOffset += 2 * PUBLIC_DATA_WRITES_PER_KERNEL * 0x40;
+        offsets.contractOffset += 2 * 0x20;
+        offsets.contractDataOffset += 2 * 0x34;
 
-        // Kernel2.contract.ethAddress padded to 32 bytes
-        // Add 12 (0xc) bytes of padding to the ethAddress
-        dstOffset := add(dstOffset, 0xc)
+        baseLeafs[i] = sha256(baseLeaf);
+      }
+    }
+
+    bytes32 diffRoot = _computeRoot(baseLeafs);
+
+    bytes32 messagesHash;
+    {
+      uint256 messagesHashPreimageSize = 0x20 * L1_TO_L2_MESSAGES_PER_ROLLUP;
+      bytes memory messagesHashPreimage = new bytes(messagesHashPreimageSize);
+      assembly {
         calldatacopy(
-          add(baseLeaf, dstOffset), add(_l2Block.offset, add(srcContractDataOffset, 0x54)), 0x14
+          add(messagesHashPreimage, 0x20),
+          add(mload(add(offsets, 0xa0)), 20),
+          messagesHashPreimageSize
         )
       }
 
-      srcCommitmentOffset += 2 * COMMITMENTS_PER_KERNEL * 0x20;
-      srcNullifierOffset += 2 * NULLIFIERS_PER_KERNEL * 0x20;
-      srcDataOffset += 2 * PUBLIC_DATA_WRITES_PER_KERNEL * 0x40;
-      srcContractOffset += 2 * 0x20;
-      srcContractDataOffset += 2 * 0x34;
-
-      baseLeafs[i] = sha256(baseLeaf);
+      messagesHash = sha256(messagesHashPreimage);
     }
 
-    return _computeRoot(baseLeafs);
+    return (diffRoot, messagesHash);
   }
 
   /**
diff --git a/l1-contracts/test/Decoder.t.sol b/l1-contracts/test/Decoder.t.sol
index 19f3d8994dc..8e2c1f666d5 100644
--- a/l1-contracts/test/Decoder.t.sol
+++ b/l1-contracts/test/Decoder.t.sol
@@ -13,15 +13,15 @@ contract DecoderTest is Test {
   DecoderHelper internal helper;
 
   bytes block_1 =
-    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+    hex"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   bytes block_2 =
-    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+    hex"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
   bytes block_empty_1 =
-    hex"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+    hex"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
   bytes block_empty_2 =
-    hex"000000020668938c4a4167faa2b5031e427d74d6e38638d2eef68834b70480c5a93f8e15000000102d39729fd006096882acfbd350c91fd61883578b4fe35b63cdce3c1993a497ea000000182f8dc86ba80d8fcf491fb7a255f4163e4f9601d022ba0be35f13297531073fd800000004238b20b7bc1d5190f8e928eb2aa2094412588f9cad6c7862f69c09a9b246d6ed0000000225d4ca531bca7d097a93bc47d7aa2c4dbcc8d0d5ecf4138849104e363eb52c03000000022b72136df9bc7dc9cbfe6b84ec743e8e1d73dd93aecfa79f18afb86be977d3eb0668938c4a4167faa2b5031e427d74d6e38638d2eef68834b70480c5a93f8e15000000202d39729fd006096882acfbd350c91fd61883578b4fe35b63cdce3c1993a497ea000000282f8dc86ba80d8fcf491fb7a255f4163e4f9601d022ba0be35f13297531073fd800000008236394e84a01824e286653b542a923474253251e86c118f02978d5714538236c000000030aaa66ea64a4b9493d7237d092f8276e31eb3f8b14ae5c5e0a91fa5627745a83000000032b72136df9bc7dc9cbfe6b84ec743e8e1d73dd93aecfa79f18afb86be977d3eb000000100000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000100000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000100000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000004000000000000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+    hex"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
   function setUp() public {
     rollup = new Rollup();
@@ -30,13 +30,20 @@ contract DecoderTest is Test {
 
   function testEmptyBlocks() public {
     {
-      bytes32 diffRoot = helper.computeDiffRoot(block_empty_1);
+      (bytes32 diffRoot, bytes32 l1ToL2MessagesHash) =
+        helper.computeDiffRootAndMessagesHash(block_empty_2);
       assertEq(
-        0x84036b397b37b2dab7c2d95581275797c8d06b432f3826ada23cca6d87d49b84,
         diffRoot,
+        0x84036b397b37b2dab7c2d95581275797c8d06b432f3826ada23cca6d87d49b84,
         "Invalid diff root"
       );
 
+      assertEq(
+        l1ToL2MessagesHash,
+        0x076a27c79e5ace2a3d47f9dd2e83e4ff6ea8872b3c2218f66c92b89b55f36560,
+        "Invalid messages hash"
+      );
+
       (
         uint256 l2BlockNumber,
         bytes32 startStateHash,
@@ -47,17 +54,17 @@ contract DecoderTest is Test {
       assertEq(l2BlockNumber, 1, "Invalid block number");
       assertEq(
         startStateHash,
-        0xc3c559a71e6e4e6120dc290ac2aefe6739be32216168d5c98899a86f1566d930,
+        0x2d5d49acd86a4ce5d71f632bd8c39d61d12c7be4ad4ab1f17e134e55aa4e29c2,
         "Invalid start state hash"
       );
       assertEq(
         endStateHash,
-        0x448312391a3205ecaf22d804a780c19890d6425c621e9a731c342f9903a5e71f,
+        0x3dff2c815f7e5f5b8b3a2397347cc928001c73e5442d6dad5af61c3329b4fc8c,
         "Invalid end state hash"
       );
       assertEq(
         publicInputsHash,
-        0x2e8af2457a0c7cef1b1d47efa0583f1e0840910ab1a802bff812bbc5e62b7321,
+        0x23f698e487c4e1b7383889f8864bc19591773d136c364c01d980bd13d0786ba1,
         "Invalid public input hash"
       );
 
@@ -67,13 +74,20 @@ contract DecoderTest is Test {
     }
 
     {
-      bytes32 diffRoot = helper.computeDiffRoot(block_empty_2);
+      (bytes32 diffRoot, bytes32 l1ToL2MessagesHash) =
+        helper.computeDiffRootAndMessagesHash(block_empty_2);
       assertEq(
-        0x84036b397b37b2dab7c2d95581275797c8d06b432f3826ada23cca6d87d49b84,
         diffRoot,
+        0x84036b397b37b2dab7c2d95581275797c8d06b432f3826ada23cca6d87d49b84,
         "Invalid diff root"
       );
 
+      assertEq(
+        l1ToL2MessagesHash,
+        0x076a27c79e5ace2a3d47f9dd2e83e4ff6ea8872b3c2218f66c92b89b55f36560,
+        "Invalid messages hash"
+      );
+
       (
         uint256 l2BlockNumber,
         bytes32 startStateHash,
@@ -84,17 +98,17 @@ contract DecoderTest is Test {
       assertEq(l2BlockNumber, 2, "Invalid block number");
       assertEq(
         startStateHash,
-        0x448312391a3205ecaf22d804a780c19890d6425c621e9a731c342f9903a5e71f,
+        0x3dff2c815f7e5f5b8b3a2397347cc928001c73e5442d6dad5af61c3329b4fc8c,
         "Invalid start state hash"
       );
       assertEq(
         endStateHash,
-        0x2fb8f70b8011dfa8111055c18a0068294d795c2c82701f18b5bf93b3156fe83f,
+        0x906b283a0f25f74711aa8e1cdaea18a6e80bebe9ce9118315a0f31433feaffe3,
         "Invalid end state hash"
       );
       assertEq(
         publicInputsHash,
-        0x0b0c644c9a7106d293ca833a1cb332a576de6971951c2167408545dd7e31a7bb,
+        0x0f6cd26577a7c4edf15eb3785315d9f8dbcbc8a3ffc0dba7e04be4e37b09228f,
         "Invalid public input hash"
       );
 
@@ -106,13 +120,20 @@ contract DecoderTest is Test {
 
   function testNonEmptyBlocks() public {
     {
-      bytes32 diffRoot = helper.computeDiffRoot(block_1);
+      (bytes32 diffRoot, bytes32 l1ToL2MessagesHash) =
+        helper.computeDiffRootAndMessagesHash(block_1);
       assertEq(
-        0x05ab40c0ddda5b1846c6283c0a99ea7da9ebb3ea46f33225e72e0d0333bf251f,
         diffRoot,
+        0x05ab40c0ddda5b1846c6283c0a99ea7da9ebb3ea46f33225e72e0d0333bf251f,
         "Invalid diff root block 1"
       );
 
+      assertEq(
+        l1ToL2MessagesHash,
+        0x076a27c79e5ace2a3d47f9dd2e83e4ff6ea8872b3c2218f66c92b89b55f36560,
+        "Invalid messages hash"
+      );
+
       (
         uint256 l2BlockNumber,
         bytes32 startStateHash,
@@ -123,17 +144,17 @@ contract DecoderTest is Test {
       assertEq(l2BlockNumber, 1, "Invalid block number");
       assertEq(
         startStateHash,
-        0xc3c559a71e6e4e6120dc290ac2aefe6739be32216168d5c98899a86f1566d930,
+        0x2d5d49acd86a4ce5d71f632bd8c39d61d12c7be4ad4ab1f17e134e55aa4e29c2,
         "Invalid start state hash block 1"
       );
       assertEq(
         endStateHash,
-        0x45faded932e3a828a426370bd7275120c3f4ed27117a6c98c9c762e8b8cec9f6,
+        0x8a6161ff9185b2354adadb2a6fbd0a8279d2b7558e617f46cfbd42af3073729c,
         "Invalid end state hash block 1"
       );
       assertEq(
         publicInputsHash,
-        0x28b90cb81b273c3ee583750e79bca15e9b01fe01a7eacacf462ee866cefb904a,
+        0x04b30d90646ca894b0f04cafb6bd76cc7db900dc8cb0a8904b21ff2a6cd4f23e,
         "Invalid public input hash block 1"
       );
 
@@ -143,13 +164,20 @@ contract DecoderTest is Test {
     }
 
     {
-      bytes32 diffRoot = helper.computeDiffRoot(block_2);
+      (bytes32 diffRoot, bytes32 l1ToL2MessagesHash) =
+        helper.computeDiffRootAndMessagesHash(block_2);
       assertEq(
-        0x04a10b2ce6eb66a3ae547efacc53760ec64fb86c901f9cadb36c104cc532cb99,
         diffRoot,
+        0x04a10b2ce6eb66a3ae547efacc53760ec64fb86c901f9cadb36c104cc532cb99,
         "Invalid diff root block 2"
       );
 
+      assertEq(
+        l1ToL2MessagesHash,
+        0x076a27c79e5ace2a3d47f9dd2e83e4ff6ea8872b3c2218f66c92b89b55f36560,
+        "Invalid l1 to l2 messages hash block 2"
+      );
+
       (
         uint256 l2BlockNumber,
         bytes32 startStateHash,
@@ -160,17 +188,17 @@ contract DecoderTest is Test {
       assertEq(l2BlockNumber, 2, "Invalid block number");
       assertEq(
         startStateHash,
-        0x45faded932e3a828a426370bd7275120c3f4ed27117a6c98c9c762e8b8cec9f6,
+        0x8a6161ff9185b2354adadb2a6fbd0a8279d2b7558e617f46cfbd42af3073729c,
         "Invalid start state hash block 2"
       );
       assertEq(
         endStateHash,
-        0x0b04cfd8792e17a123c3c5c82bd2593e8da745d05296d4e1058708e11489909a,
+        0xd2055c0813616d7073f6bcc905a755ed525e5541b3e5e1b286fd583729c74ea7,
         "Invalid end state hash block 2"
       );
       assertEq(
         publicInputsHash,
-        0x04f8878ba2e56773029c2b246d41f04963cc8b2654bc35a66b72ff79a7a756ec,
+        0x22d088d033eac3347d80581f49057fe24d366cdfdaa644ad4a286d4f8280842b,
         "Invalid public input hash block 2"
       );
 
diff --git a/l1-contracts/test/DecoderHelper.sol b/l1-contracts/test/DecoderHelper.sol
index 90a32fd24bb..4bf7de3225c 100644
--- a/l1-contracts/test/DecoderHelper.sol
+++ b/l1-contracts/test/DecoderHelper.sol
@@ -13,7 +13,12 @@ contract DecoderHelper is Decoder {
     return _decode(_l2Block);
   }
 
-  function computeDiffRoot(bytes calldata _l2Block) external pure returns (bytes32) {
-    return _computeDiffRoot(_l2Block);
+  function computeDiffRootAndMessagesHash(bytes calldata _l2Block)
+    external
+    pure
+    returns (bytes32, bytes32)
+  {
+    (bytes32 diffRoot, bytes32 l1ToL2MessagesHash) = _computeDiffRootAndMessagesHash(_l2Block);
+    return (diffRoot, l1ToL2MessagesHash);
   }
 }
diff --git a/yarn-project/circuits.js/src/structs/constants.ts b/yarn-project/circuits.js/src/structs/constants.ts
index a4ba827ca06..8c06c37b2bb 100644
--- a/yarn-project/circuits.js/src/structs/constants.ts
+++ b/yarn-project/circuits.js/src/structs/constants.ts
@@ -29,9 +29,14 @@ export const CONTRACT_TREE_HEIGHT = 4;
 export const PRIVATE_DATA_TREE_HEIGHT = 8;
 export const PUBLIC_DATA_TREE_HEIGHT = 254;
 export const NULLIFIER_TREE_HEIGHT = 8;
+export const L1_TO_L2_MESSAGES_TREE_HEIGHT = 8;
+export const L1_TO_L2_MESSAGES_ROOTS_TREE_HEIGHT = 8;
+export const L1_TO_L2_MESSAGES_SUBTREE_INSERTION_HEIGHT = 4;
 
 export const PRIVATE_DATA_TREE_ROOTS_TREE_HEIGHT = 8;
 export const CONTRACT_TREE_ROOTS_TREE_HEIGHT = 8;
 export const ROLLUP_VK_TREE_HEIGHT = 8;
 
 export const FUNCTION_SELECTOR_NUM_BYTES = 4;
+
+export const NUMBER_OF_L1_L2_MESSAGES_PER_ROLLUP = 16;
diff --git a/yarn-project/circuits.js/src/structs/rollup/__snapshots__/root_rollup.test.ts.snap b/yarn-project/circuits.js/src/structs/rollup/__snapshots__/root_rollup.test.ts.snap
index 72ef4bfa0d7..5eeab7ec5d2 100644
--- a/yarn-project/circuits.js/src/structs/rollup/__snapshots__/root_rollup.test.ts.snap
+++ b/yarn-project/circuits.js/src/structs/rollup/__snapshots__/root_rollup.test.ts.snap
@@ -160,6 +160,15 @@ sibling_path: [ 0x1120 0x1121 0x1122 0x1123 0x1124 0x1125 0x1126 0x1127 ]
  ]
 new_historic_private_data_tree_roots: [ 0x2000 0x2001 0x2002 0x2003 0x2004 0x2005 0x2006 0x2007 ]
 new_historic_contract_tree_roots: [ 0x2100 0x2101 0x2102 0x2103 0x2104 0x2105 0x2106 0x2107 ]
+new_l1_to_l2_messages: [ 0x2100 0x2101 0x2102 0x2103 0x2104 0x2105 0x2106 0x2107 0x2108 0x2109 0x210a 0x210b 0x210c 0x210d 0x210e 0x210f ]
+new_l1_to_l2_message_tree_root_sibling_path: [ 0x2100 0x2101 0x2102 0x2103 ]
+new_historic_l1_to_l2_message_roots_tree_sibling_path: [ 0x2100 0x2101 0x2102 0x2103 0x2104 0x2105 0x2106 0x2107 ]
+start_l1_to_l2_message_tree_snapshot: root: 0x2200
+next_available_leaf_index: 8704
+
+start_historic_tree_l1_to_l2_message_tree_roots_snapshot: root: 0x2300
+next_available_leaf_index: 8960
+
 "
 `;
 
@@ -207,6 +216,19 @@ next_available_leaf_index: 2816
 end_tree_of_historic_contract_tree_roots_snapshot: root: 0xc00
 next_available_leaf_index: 3072
 
+start_l1_to_l2_messages_tree_snapshot: root: 0xd00
+next_available_leaf_index: 3328
+
+end_l1_tol2_messages_tree_snapshot: root: 0xe00
+next_available_leaf_index: 3584
+
+start_tree_of_historic_l1_to_l2_messages_tree_roots_snapshot: root: 0xf00
+next_available_leaf_index: 3840
+
+end_tree_of_historic_l1_tol2_messages_tree_roots_snapshot: root: 0x1000
+next_available_leaf_index: 4096
+
 calldata_hash: [ 0x1 0x2 ]
+l1_to_l2_messages_hash: [ 0x3 0x4 ]
 "
 `;
diff --git a/yarn-project/circuits.js/src/structs/rollup/root_rollup.ts b/yarn-project/circuits.js/src/structs/rollup/root_rollup.ts
index 055883a218c..0ae40fcb492 100644
--- a/yarn-project/circuits.js/src/structs/rollup/root_rollup.ts
+++ b/yarn-project/circuits.js/src/structs/rollup/root_rollup.ts
@@ -2,7 +2,13 @@ import { BufferReader, Fr } from '@aztec/foundation';
 import { assertLength, FieldsOf } from '../../utils/jsUtils.js';
 import { serializeToBuffer } from '../../utils/serialize.js';
 import { AppendOnlyTreeSnapshot } from './append_only_tree_snapshot.js';
-import { CONTRACT_TREE_ROOTS_TREE_HEIGHT, PRIVATE_DATA_TREE_ROOTS_TREE_HEIGHT } from '../constants.js';
+import {
+  CONTRACT_TREE_ROOTS_TREE_HEIGHT,
+  L1_TO_L2_MESSAGES_ROOTS_TREE_HEIGHT,
+  L1_TO_L2_MESSAGES_SUBTREE_INSERTION_HEIGHT,
+  NUMBER_OF_L1_L2_MESSAGES_PER_ROLLUP,
+  PRIVATE_DATA_TREE_ROOTS_TREE_HEIGHT,
+} from '../constants.js';
 import { PreviousRollupData } from './previous_rollup_data.js';
 import { AggregationObject } from '../aggregation_object.js';
 
@@ -12,17 +18,21 @@ export class RootRollupInputs {
 
     public newHistoricPrivateDataTreeRootSiblingPath: Fr[],
     public newHistoricContractDataTreeRootSiblingPath: Fr[],
+    public newL1ToL2Messages: Fr[],
+    public newL1ToL2MessageTreeRootSiblingPath: Fr[],
+    public newHistoricL1ToL2MessageTreeRootSiblingPath: Fr[],
+    public startL1ToL2MessageTreeSnapshot: AppendOnlyTreeSnapshot,
+    public startHistoricTreeL1ToL2MessageTreeRootsSnapshot: AppendOnlyTreeSnapshot,
   ) {
     assertLength(this, 'newHistoricPrivateDataTreeRootSiblingPath', PRIVATE_DATA_TREE_ROOTS_TREE_HEIGHT);
     assertLength(this, 'newHistoricContractDataTreeRootSiblingPath', CONTRACT_TREE_ROOTS_TREE_HEIGHT);
+    assertLength(this, 'newL1ToL2MessageTreeRootSiblingPath', L1_TO_L2_MESSAGES_SUBTREE_INSERTION_HEIGHT);
+    assertLength(this, 'newHistoricL1ToL2MessageTreeRootSiblingPath', L1_TO_L2_MESSAGES_ROOTS_TREE_HEIGHT);
+    assertLength(this, 'newL1ToL2Messages', NUMBER_OF_L1_L2_MESSAGES_PER_ROLLUP);
   }
 
   toBuffer() {
-    return serializeToBuffer(
-      this.previousRollupData,
-      this.newHistoricPrivateDataTreeRootSiblingPath,
-      this.newHistoricContractDataTreeRootSiblingPath,
-    );
+    return serializeToBuffer(...RootRollupInputs.getFields(this));
   }
 
   static from(fields: FieldsOf<RootRollupInputs>): RootRollupInputs {
@@ -34,6 +44,11 @@ export class RootRollupInputs {
       fields.previousRollupData,
       fields.newHistoricPrivateDataTreeRootSiblingPath,
       fields.newHistoricContractDataTreeRootSiblingPath,
+      fields.newL1ToL2Messages,
+      fields.newL1ToL2MessageTreeRootSiblingPath,
+      fields.newHistoricL1ToL2MessageTreeRootSiblingPath,
+      fields.startL1ToL2MessageTreeSnapshot,
+      fields.startHistoricTreeL1ToL2MessageTreeRootsSnapshot,
     ] as const;
   }
 }
@@ -63,7 +78,14 @@ export class RootRollupPublicInputs {
     public startTreeOfHistoricContractTreeRootsSnapshot: AppendOnlyTreeSnapshot,
     public endTreeOfHistoricContractTreeRootsSnapshot: AppendOnlyTreeSnapshot,
 
+    public startL1ToL2MessageTreeSnapshot: AppendOnlyTreeSnapshot,
+    public endL1ToL2MessageTreeSnapshot: AppendOnlyTreeSnapshot,
+
+    public startTreeOfHistoricL1ToL2MessageTreeRootsSnapshot: AppendOnlyTreeSnapshot,
+    public endTreeOfHistoricL1ToL2MessageTreeRootsSnapshot: AppendOnlyTreeSnapshot,
+
     public calldataHash: [Fr, Fr],
+    public l1ToL2MessagesHash: [Fr, Fr],
   ) {}
 
   static getFields(fields: FieldsOf<RootRollupPublicInputs>) {
@@ -81,7 +103,12 @@ export class RootRollupPublicInputs {
       fields.endTreeOfHistoricPrivateDataTreeRootsSnapshot,
       fields.startTreeOfHistoricContractTreeRootsSnapshot,
       fields.endTreeOfHistoricContractTreeRootsSnapshot,
+      fields.startL1ToL2MessageTreeSnapshot,
+      fields.endL1ToL2MessageTreeSnapshot,
+      fields.startTreeOfHistoricL1ToL2MessageTreeRootsSnapshot,
+      fields.endTreeOfHistoricL1ToL2MessageTreeRootsSnapshot,
       fields.calldataHash,
+      fields.l1ToL2MessagesHash,
     ] as const;
   }
 
@@ -109,6 +136,11 @@ export class RootRollupPublicInputs {
       reader.readObject(AppendOnlyTreeSnapshot),
       reader.readObject(AppendOnlyTreeSnapshot),
       reader.readObject(AppendOnlyTreeSnapshot),
+      reader.readObject(AppendOnlyTreeSnapshot),
+      reader.readObject(AppendOnlyTreeSnapshot),
+      reader.readObject(AppendOnlyTreeSnapshot),
+      reader.readObject(AppendOnlyTreeSnapshot),
+      [reader.readFr(), reader.readFr()],
       [reader.readFr(), reader.readFr()],
     );
   }
diff --git a/yarn-project/circuits.js/src/tests/factories.ts b/yarn-project/circuits.js/src/tests/factories.ts
index 8052374eff6..3e40c575ed7 100644
--- a/yarn-project/circuits.js/src/tests/factories.ts
+++ b/yarn-project/circuits.js/src/tests/factories.ts
@@ -45,10 +45,13 @@ import {
   KERNEL_OPTIONALLY_REVEALED_DATA_LENGTH,
   KERNEL_PRIVATE_CALL_STACK_LENGTH,
   KERNEL_PUBLIC_CALL_STACK_LENGTH,
+  L1_TO_L2_MESSAGES_ROOTS_TREE_HEIGHT,
+  L1_TO_L2_MESSAGES_SUBTREE_INSERTION_HEIGHT,
   NEW_L2_TO_L1_MSGS_LENGTH,
   NEW_COMMITMENTS_LENGTH,
   NEW_NULLIFIERS_LENGTH,
   NULLIFIER_TREE_HEIGHT,
+  NUMBER_OF_L1_L2_MESSAGES_PER_ROLLUP,
   PRIVATE_CALL_STACK_LENGTH,
   PRIVATE_DATA_TREE_HEIGHT,
   PRIVATE_DATA_TREE_ROOTS_TREE_HEIGHT,
@@ -430,6 +433,11 @@ export function makeRootRollupInputs(seed = 0) {
     [makePreviousBaseRollupData(seed), makePreviousBaseRollupData(seed + 0x1000)],
     range(PRIVATE_DATA_TREE_ROOTS_TREE_HEIGHT, 0x2000).map(fr),
     range(CONTRACT_TREE_ROOTS_TREE_HEIGHT, 0x2100).map(fr),
+    range(NUMBER_OF_L1_L2_MESSAGES_PER_ROLLUP, 0x2100).map(fr),
+    range(L1_TO_L2_MESSAGES_SUBTREE_INSERTION_HEIGHT, 0x2100).map(fr),
+    range(L1_TO_L2_MESSAGES_ROOTS_TREE_HEIGHT, 0x2100).map(fr),
+    makeAppendOnlyTreeSnapshot(seed + 0x2200),
+    makeAppendOnlyTreeSnapshot(seed + 0x2300),
   );
 }
 
@@ -448,7 +456,12 @@ export function makeRootRollupPublicInputs(seed = 0) {
     endTreeOfHistoricPrivateDataTreeRootsSnapshot: makeAppendOnlyTreeSnapshot((seed += 0x100)),
     startTreeOfHistoricContractTreeRootsSnapshot: makeAppendOnlyTreeSnapshot((seed += 0x100)),
     endTreeOfHistoricContractTreeRootsSnapshot: makeAppendOnlyTreeSnapshot((seed += 0x100)),
+    startL1ToL2MessageTreeSnapshot: makeAppendOnlyTreeSnapshot((seed += 0x100)),
+    endL1ToL2MessageTreeSnapshot: makeAppendOnlyTreeSnapshot((seed += 0x100)),
+    startTreeOfHistoricL1ToL2MessageTreeRootsSnapshot: makeAppendOnlyTreeSnapshot((seed += 0x100)),
+    endTreeOfHistoricL1ToL2MessageTreeRootsSnapshot: makeAppendOnlyTreeSnapshot((seed += 0x100)),
     calldataHash: [new Fr(1n), new Fr(2n)],
+    l1ToL2MessagesHash: [new Fr(3n), new Fr(4n)],
   });
 }
 
diff --git a/yarn-project/l1-contracts/src/ethereumjs-contracts/DecoderHelper.ts b/yarn-project/l1-contracts/src/ethereumjs-contracts/DecoderHelper.ts
index c942acf16ad..b9880043b92 100644
--- a/yarn-project/l1-contracts/src/ethereumjs-contracts/DecoderHelper.ts
+++ b/yarn-project/l1-contracts/src/ethereumjs-contracts/DecoderHelper.ts
@@ -10,7 +10,7 @@ interface DecoderHelperEventLogs {}
 interface DecoderHelperTxEventLogs {}
 export interface DecoderHelperTransactionReceipt extends ContractTxReceipt<DecoderHelperTxEventLogs> {}
 interface DecoderHelperMethods {
-  computeDiffRoot(_l2Block: Bytes.Bytes): TxCall<Bytes.Bytes32>;
+  computeDiffRootAndMessagesHash(_l2Block: Bytes.Bytes): TxCall<{ 0: Bytes.Bytes32; 1: Bytes.Bytes32 }>;
   decode(_l2Block: Bytes.Bytes): TxCall<{
     0: bigint;
     1: Bytes.Bytes32;
@@ -29,7 +29,7 @@ export class DecoderHelper extends Contract<DecoderHelperDefinition> {
   }
   deploy(): TxSend<DecoderHelperTransactionReceipt> {
     return super.deployBytecode(
-      '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+      '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     ) as any;
   }
 }
diff --git a/yarn-project/l1-contracts/src/ethereumjs-contracts/DecoderHelperAbi.ts b/yarn-project/l1-contracts/src/ethereumjs-contracts/DecoderHelperAbi.ts
index bc6ba0393e6..fb2cbe3e729 100644
--- a/yarn-project/l1-contracts/src/ethereumjs-contracts/DecoderHelperAbi.ts
+++ b/yarn-project/l1-contracts/src/ethereumjs-contracts/DecoderHelperAbi.ts
@@ -8,15 +8,20 @@ export default new ContractAbi([
         type: 'bytes',
       },
     ],
-    name: 'computeDiffRoot',
+    name: 'computeDiffRootAndMessagesHash',
     outputs: [
       {
         internalType: 'bytes32',
         name: '',
         type: 'bytes32',
       },
+      {
+        internalType: 'bytes32',
+        name: '',
+        type: 'bytes32',
+      },
     ],
-    stateMutability: 'pure',
+    stateMutability: 'view',
     type: 'function',
   },
   {
@@ -50,7 +55,7 @@ export default new ContractAbi([
         type: 'bytes32',
       },
     ],
-    stateMutability: 'pure',
+    stateMutability: 'view',
     type: 'function',
   },
 ]);
diff --git a/yarn-project/l1-contracts/src/ethereumjs-contracts/Rollup.ts b/yarn-project/l1-contracts/src/ethereumjs-contracts/Rollup.ts
index 5277921c129..6a6fa590afb 100644
--- a/yarn-project/l1-contracts/src/ethereumjs-contracts/Rollup.ts
+++ b/yarn-project/l1-contracts/src/ethereumjs-contracts/Rollup.ts
@@ -35,7 +35,7 @@ export class Rollup extends Contract<RollupDefinition> {
   }
   deploy(): TxSend<RollupTransactionReceipt> {
     return super.deployBytecode(
-      '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',
+      '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     ) as any;
   }
 }
diff --git a/yarn-project/l1-contracts/src/viem-contracts/DecoderHelper.ts b/yarn-project/l1-contracts/src/viem-contracts/DecoderHelper.ts
index fddfb2ee271..7bd614dc0d6 100644
--- a/yarn-project/l1-contracts/src/viem-contracts/DecoderHelper.ts
+++ b/yarn-project/l1-contracts/src/viem-contracts/DecoderHelper.ts
@@ -10,15 +10,20 @@ export const DecoderHelperAbi = [
         type: 'bytes',
       },
     ],
-    name: 'computeDiffRoot',
+    name: 'computeDiffRootAndMessagesHash',
     outputs: [
       {
         internalType: 'bytes32',
         name: '',
         type: 'bytes32',
       },
+      {
+        internalType: 'bytes32',
+        name: '',
+        type: 'bytes32',
+      },
     ],
-    stateMutability: 'pure',
+    stateMutability: 'view',
     type: 'function',
   },
   {
@@ -52,7 +57,7 @@ export const DecoderHelperAbi = [
         type: 'bytes32',
       },
     ],
-    stateMutability: 'pure',
+    stateMutability: 'view',
     type: 'function',
   },
 ] as const;
@@ -60,4 +65,4 @@ export const DecoderHelperAbi = [
  * DecoderHelper Bytecode for viem.
  */
 export const DecoderHelperBytecode =
-  '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+  '0x608060405234801561001057600080fd5b50610bbd806100206000396000f3fe608060405234801561001057600080fd5b50600436106100365760003560e01c8063bdfd97c01461003b578063e5c5e9a314610068575b600080fd5b61004e610049366004610900565b61009b565b604080519283526020830191909152015b60405180910390f35b61007b610076366004610900565b6100b8565b60408051948552602085019390935291830152606082015260800161005f565b6000806000806100ab86866100d8565b9097909650945050505050565b6000806000806100c886866105b6565b9299919850965090945092505050565b60008061010d6040518060a0016040528060008152602001600081526020016000815260200160008152602001600081525090565b6101466040518060c001604052806000815260200160008152602001600081526020016000815260200160008152602001600081525090565b61023c86013560e090811c80845260209081028801610240810135831c85830181905291820201610244810135831c60408681019190915290910201610248810135821c606085018190526054020161024c0135901c608083015260006101af60046002610988565b83516101bb91906109b5565b67ffffffffffffffff8111156101d3576101d36109c9565b6040519080825280602002602001820160405280156101fc578160200160208202803683370190505b5061024083528351909150610212906020610988565b825161021f9060046109df565b61022991906109df565b6020808401919091528381015161023f91610988565b602083015161024f9060046109df565b61025991906109df565b6040808401919091528381015161026f91610988565b604083015161027f9060046109df565b61028991906109df565b6060808401919091528301516102a0906020610988565b82606001516102af91906109df565b608083015260608301516102c4906054610988565b82608001516102d391906109df565b60a083015260005b81518110156104df57604080516104c08082526104e0820190925260009160208201818036833701905050905060208060080285518b018284013760208501516101008281019290918c01908401820137604085015161010082810192610200928d019190850101376060850151610200828101926040928d0191908501013760206002028101905060808501516020818c0183850137602c808301926014918d840160200191860101376020820191506020603482018c0183850137602c808301926014918d84016054019186010137506103bb905060046002610988565b6103c6906020610988565b845185906103d59083906109df565b9052506103e460046002610988565b6103ef906020610988565b8460200181815161040091906109df565b90525061040f60046002610988565b61041a906040610988565b8460400181815161042b91906109df565b905250606084018051604091906104439083906109df565b9052506080840180516068919061045b9083906109df565b90525060405160029061046f9083906109f2565b602060405180830381855afa15801561048c573d6000803e3d6000fd5b5050506040513d601f19601f820116820180604052508101906104af9190610a21565b8383815181106104c1576104c1610a3a565b602090810291909101015250806104d781610a50565b9150506102db565b5060006104eb826105fd565b90506000806104fc60106020610988565b905060008167ffffffffffffffff811115610519576105196109c9565b6040519080825280601f01601f191660200182016040528015610543576020820181803683370190505b50905081601460a088015101602083013760028160405161056491906109f2565b602060405180830381855afa158015610581573d6000803e3d6000fd5b5050506040513d601f19601f820116820180604052508101906105a49190610a21565b939b939a509298505050505050505050565b813560e01c600080806105d66105cd600186610a69565b60048888610775565b92506105e6846101208888610775565b91506105f28686610822565b905092959194509250565b6000805b825161060e826002610b60565b1015610626578061061e81610a50565b915050610601565b6000610633826002610b60565b905080845260005b828110156107505760005b8281101561073d57600286828151811061066257610662610a3a565b60200260200101518783600161067891906109df565b8151811061068857610688610a3a565b60200260200101516040516020016106aa929190918252602082015260400190565b60408051601f19818403018152908290526106c4916109f2565b602060405180830381855afa1580156106e1573d6000803e3d6000fd5b5050506040513d601f19601f820116820180604052508101906107049190610a21565b866107106002846109b5565b8151811061072057610720610a3a565b60209081029190910101526107366002826109df565b9050610646565b508061074881610a50565b91505061063b565b508360008151811061076457610764610a3a565b602002602001015192505050919050565b6040805161012080825261014082019092526000918291906020820181803683370190505090508560181c60208201538560101c60218201538560081c602282015385602382015361011c85850160248301376002816040516107d891906109f2565b602060405180830381855afa1580156107f5573d6000803e3d6000fd5b5050506040513d601f19601f820116820180604052508101906108189190610a21565b9695505050505050565b604080516102788082526102a08201909252600091908290826020820181803683370190505090508160048601602083013760008061086187876100d8565b6102588501829052610278850181905260405191935091507f30644e72e131a029b85045b68181585d2833e84879b9709143e1f593f0000001906002906108a99086906109f2565b602060405180830381855afa1580156108c6573d6000803e3d6000fd5b5050506040513d601f19601f820116820180604052508101906108e99190610a21565b6108f39190610b73565b9450505050505b92915050565b6000806020838503121561091357600080fd5b823567ffffffffffffffff8082111561092b57600080fd5b818501915085601f83011261093f57600080fd5b81358181111561094e57600080fd5b86602082850101111561096057600080fd5b60209290920196919550909350505050565b634e487b7160e01b600052601160045260246000fd5b80820281158282048414176108fa576108fa610972565b634e4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diff --git a/yarn-project/l1-contracts/src/viem-contracts/Rollup.ts b/yarn-project/l1-contracts/src/viem-contracts/Rollup.ts
index 843bfd9b2a7..04e882b4f8c 100644
--- a/yarn-project/l1-contracts/src/viem-contracts/Rollup.ts
+++ b/yarn-project/l1-contracts/src/viem-contracts/Rollup.ts
@@ -90,4 +90,4 @@ export const RollupAbi = [
  * Rollup Bytecode for viem.
  */
 export const RollupBytecode =
-  '0x60a060405234801561001057600080fd5b5060405161001d9061004b565b604051809103906000f080158015610039573d6000803e3d6000fd5b506001600160a01b0316608052610058565b61019d80610d5483390190565b608051610cdb61007960003960008181604b015261016b0152610cdb6000f3fe608060405234801561001057600080fd5b50600436106100415760003560e01c806308c84e70146100465780631ab9c6031461008a5780637c39d130146100a1575b600080fd5b61006d7f000000000000000000000000000000000000000000000000000000000000000081565b6040516001600160a01b0390911681526020015b60405180910390f35b61009360005481565b604051908152602001610081565b6100b46100af36600461091e565b6100b6565b005b6000806000806100c68686610237565b60005493975091955093509150158015906100e357508260005414155b1561011357600054604051632d2ef59f60e11b815260048101919091526024810184905260440160405180910390fd5b604080516001808252818301909252600091602080830190803683370190505090508181600081518110610149576101496109f9565b6020908102919091010152604051633a94343960e21b81526001600160a01b037f0000000000000000000000000000000000000000000000000000000000000000169063ea50d0e4906101a2908b908590600401610a33565b602060405180830381865afa1580156101bf573d6000803e3d6000fd5b505050506040513d601f19601f820116820180604052508101906101e39190610aad565b610200576040516309bde33960e01b815260040160405180910390fd5b600083815560405186917f655779015b9b95c7fd18f01ea4619ab4c31289bbe134ba85c5b20bcdeb1dabf391a25050505050505050565b813560e01c6000808061025761024e600186610aec565b6004888861027d565b92506102668460d8888861027d565b91506102728686610328565b905092959194509250565b6040805160d880825261010082019092526000918291906020820181803683370190505090508560181c60208201538560101c60218201538560081c602282015385602382015360d485850160248301376002816040516102de9190610aff565b602060405180830381855afa1580156102fb573d6000803e3d6000fd5b5050506040513d601f19601f8201168201806040525081019061031e9190610b1b565b9695505050505050565b604080516101c880825261020082019092526000919082908260208201818036833701905050905081600486016020830137600061036686866103fc565b90508060046101ac036020018301527f30644e72e131a029b85045b68181585d2833e84879b9709143e1f593f00000016002836040516103a69190610aff565b602060405180830381855afa1580156103c3573d6000803e3d6000fd5b5050506040513d601f19601f820116820180604052508101906103e69190610b1b565b6103f09190610b4a565b93505050505b92915050565b60006104296040518060800160405280600081526020016000815260200160008152602001600081525090565b6101ac84013560e090811c808352602090810286016101b0810135831c848301819052918202016101b4810135831c604085810191909152909102016101b80135901c6060820152600061047f60046002610b5e565b825161048b9190610b75565b67ffffffffffffffff8111156104a3576104a36108bf565b6040519080825280602002602001820160405280156104cc578160200160208202803683370190505b5082519091506101b0906000906104e4906020610b5e565b6104ef836004610b89565b6104f99190610b89565b905060008460200151602061050e9190610b5e565b610519836004610b89565b6105239190610b89565b90506000856040015160406105389190610b5e565b610543836004610b89565b61054d9190610b89565b90506000866060015160206105629190610b5e565b61056c9083610b89565b905060005b865181101561072f57604080516104c08082526104e0820190925260009160208201818036833701905050905060206101008d890182840137610100818101918e890190840182013761010081810191610200918f89019185010137610200818101916040918f880191850101376020600202810190506020848e0182840137602c808201916014918f870160200191850101376020810190506020603485018e0182840137602c808201916014918f870160540191850101375061063860046002610b5e565b610643906020610b5e565b61064d9088610b89565b965061065b60046002610b5e565b610666906020610b5e565b6106709087610b89565b955061067e60046002610b5e565b610689906040610b5e565b6106939086610b89565b94506106a0604085610b89565b93506106ad606884610b89565b92506002816040516106bf9190610aff565b602060405180830381855afa1580156106dc573d6000803e3d6000fd5b5050506040513d601f19601f820116820180604052508101906106ff9190610b1b565b888381518110610711576107116109f9565b6020908102919091010152508061072781610b9c565b915050610571565b5061073986610747565b9a9950505050505050505050565b6000805b8251610758826002610c99565b1015610770578061076881610b9c565b91505061074b565b600061077d826002610c99565b905080845260005b8281101561089a5760005b828110156108875760028682815181106107ac576107ac6109f9565b6020026020010151878360016107c29190610b89565b815181106107d2576107d26109f9565b60200260200101516040516020016107f4929190918252602082015260400190565b60408051601f198184030181529082905261080e91610aff565b602060405180830381855afa15801561082b573d6000803e3d6000fd5b5050506040513d601f19601f8201168201806040525081019061084e9190610b1b565b8661085a600284610b75565b8151811061086a5761086a6109f9565b6020908102919091010152610880600282610b89565b9050610790565b508061089281610b9c565b915050610785565b50836000815181106108ae576108ae6109f9565b602002602001015192505050919050565b634e487b7160e01b600052604160045260246000fd5b60008083601f8401126108e757600080fd5b50813567ffffffffffffffff8111156108ff57600080fd5b60208301915083602082850101111561091757600080fd5b9250929050565b60008060006040848603121561093357600080fd5b833567ffffffffffffffff8082111561094b5760008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diff --git a/yarn-project/sequencer-client/src/block_builder/circuit_block_builder.test.ts b/yarn-project/sequencer-client/src/block_builder/circuit_block_builder.test.ts
index b310b04bc90..a490101e430 100644
--- a/yarn-project/sequencer-client/src/block_builder/circuit_block_builder.test.ts
+++ b/yarn-project/sequencer-client/src/block_builder/circuit_block_builder.test.ts
@@ -6,6 +6,7 @@ import {
   KernelCircuitPublicInputs,
   PublicDataRead,
   PublicDataTransition,
+  NUMBER_OF_L1_L2_MESSAGES_PER_ROLLUP,
   RootRollupPublicInputs,
   UInt8Vector,
 } from '@aztec/circuits.js';
@@ -55,6 +56,7 @@ describe('sequencer/circuit_block_builder', () => {
   let baseRollupOutputLeft: BaseOrMergeRollupPublicInputs;
   let baseRollupOutputRight: BaseOrMergeRollupPublicInputs;
   let rootRollupOutput: RootRollupPublicInputs;
+  let mockL1ToL2Messages: Fr[];
 
   let wasm: CircuitsWasm;
 
@@ -73,6 +75,9 @@ describe('sequencer/circuit_block_builder', () => {
     prover = mock<RollupProver>();
     builder = new CircuitBlockBuilder(builderDb, vks, simulator, prover);
 
+    // Create mock l1 to L2 messages
+    mockL1ToL2Messages = new Array(NUMBER_OF_L1_L2_MESSAGES_PER_ROLLUP).fill(new Fr(0n));
+
     // Create mock outputs for simualator
     baseRollupOutputLeft = makeBaseRollupPublicInputs();
     baseRollupOutputRight = makeBaseRollupPublicInputs();
@@ -107,54 +112,71 @@ describe('sequencer/circuit_block_builder', () => {
     }
   };
 
+  const updateL1ToL2MessagesTree = async (l1ToL2Messages: Fr[]) => {
+    const asBuffer = l1ToL2Messages.map(m => m.toBuffer());
+    await expectsDb.appendLeaves(MerkleTreeId.L1_TO_L2_MESSAGES_TREE, asBuffer);
+  };
+
   const getTreeSnapshot = async (tree: MerkleTreeId) => {
     const treeInfo = await expectsDb.getTreeInfo(tree);
     return new AppendOnlyTreeSnapshot(Fr.fromBuffer(treeInfo.root), Number(treeInfo.size));
   };
 
+  const buildMockSimulatorInputs = async () => {
+    const kernelOutput = makeKernelPublicInputs();
+    kernelOutput.constants.historicTreeRoots = await getCombinedHistoricTreeRoots(expectsDb);
+    const tx = await makeProcessedTx(Tx.createPrivate(kernelOutput, emptyProof, makeEmptyUnverifiedData()));
+
+    const txsLeft = [tx, await makeEmptyProcessedTx()];
+    const txsRight = [await makeEmptyProcessedTx(), await makeEmptyProcessedTx()];
+
+    // Calculate what would be the tree roots after the txs from the first base rollup land and update mock circuit output
+    await updateExpectedTreesFromTxs(txsLeft);
+    baseRollupOutputLeft.endContractTreeSnapshot = await getTreeSnapshot(MerkleTreeId.CONTRACT_TREE);
+    baseRollupOutputLeft.endNullifierTreeSnapshot = await getTreeSnapshot(MerkleTreeId.NULLIFIER_TREE);
+    baseRollupOutputLeft.endPrivateDataTreeSnapshot = await getTreeSnapshot(MerkleTreeId.PRIVATE_DATA_TREE);
+    baseRollupOutputLeft.endPublicDataTreeRoot = (await getTreeSnapshot(MerkleTreeId.PUBLIC_DATA_TREE)).root;
+
+    // Same for the two txs on the right
+    await updateExpectedTreesFromTxs(txsRight);
+    baseRollupOutputRight.endContractTreeSnapshot = await getTreeSnapshot(MerkleTreeId.CONTRACT_TREE);
+    baseRollupOutputRight.endNullifierTreeSnapshot = await getTreeSnapshot(MerkleTreeId.NULLIFIER_TREE);
+    baseRollupOutputRight.endPrivateDataTreeSnapshot = await getTreeSnapshot(MerkleTreeId.PRIVATE_DATA_TREE);
+    baseRollupOutputRight.endPublicDataTreeRoot = (await getTreeSnapshot(MerkleTreeId.PUBLIC_DATA_TREE)).root;
+
+    // Update l1 to l2 data tree
+    // And update the root trees now to create proper output to the root rollup circuit
+    await updateL1ToL2MessagesTree(mockL1ToL2Messages);
+    await expectsDb.updateHistoricRootsTrees();
+    rootRollupOutput.endContractTreeSnapshot = await getTreeSnapshot(MerkleTreeId.CONTRACT_TREE);
+    rootRollupOutput.endNullifierTreeSnapshot = await getTreeSnapshot(MerkleTreeId.NULLIFIER_TREE);
+    rootRollupOutput.endPrivateDataTreeSnapshot = await getTreeSnapshot(MerkleTreeId.PRIVATE_DATA_TREE);
+    rootRollupOutput.endPublicDataTreeRoot = (await getTreeSnapshot(MerkleTreeId.PUBLIC_DATA_TREE)).root;
+    rootRollupOutput.endTreeOfHistoricContractTreeRootsSnapshot = await getTreeSnapshot(
+      MerkleTreeId.CONTRACT_TREE_ROOTS_TREE,
+    );
+    rootRollupOutput.endTreeOfHistoricPrivateDataTreeRootsSnapshot = await getTreeSnapshot(
+      MerkleTreeId.PRIVATE_DATA_TREE_ROOTS_TREE,
+    );
+    rootRollupOutput.endL1ToL2MessageTreeSnapshot = await getTreeSnapshot(MerkleTreeId.L1_TO_L2_MESSAGES_TREE);
+    rootRollupOutput.endTreeOfHistoricL1ToL2MessageTreeRootsSnapshot = await getTreeSnapshot(
+      MerkleTreeId.L1_TO_L2_MESSAGES_ROOTS_TREE,
+    );
+
+    return [...txsLeft, ...txsRight];
+  };
+
   describe('mock simulator', () => {
-    it('builds an L2 block using mock simulator', async () => {
+    beforeEach(() => {
       // Create instance to test
       builder = new CircuitBlockBuilder(builderDb, vks, simulator, prover);
-
+    });
+    it('builds an L2 block using mock simulator', async () => {
       // Assemble a fake transaction
-      const kernelOutput = makeKernelPublicInputs();
-      kernelOutput.constants.historicTreeRoots = await getCombinedHistoricTreeRoots(expectsDb);
-      const tx = await makeProcessedTx(Tx.createPrivate(kernelOutput, emptyProof, makeEmptyUnverifiedData()));
-
-      const txsLeft = [tx, await makeEmptyProcessedTx()];
-      const txsRight = [await makeEmptyProcessedTx(), await makeEmptyProcessedTx()];
-
-      // Calculate what would be the tree roots after the txs from the first base rollup land and update mock circuit output
-      await updateExpectedTreesFromTxs(txsLeft);
-      baseRollupOutputLeft.endContractTreeSnapshot = await getTreeSnapshot(MerkleTreeId.CONTRACT_TREE);
-      baseRollupOutputLeft.endNullifierTreeSnapshot = await getTreeSnapshot(MerkleTreeId.NULLIFIER_TREE);
-      baseRollupOutputLeft.endPrivateDataTreeSnapshot = await getTreeSnapshot(MerkleTreeId.PRIVATE_DATA_TREE);
-      baseRollupOutputLeft.endPublicDataTreeRoot = (await getTreeSnapshot(MerkleTreeId.PUBLIC_DATA_TREE)).root;
-
-      // Same for the two txs on the right
-      await updateExpectedTreesFromTxs(txsRight);
-      baseRollupOutputRight.endContractTreeSnapshot = await getTreeSnapshot(MerkleTreeId.CONTRACT_TREE);
-      baseRollupOutputRight.endNullifierTreeSnapshot = await getTreeSnapshot(MerkleTreeId.NULLIFIER_TREE);
-      baseRollupOutputRight.endPrivateDataTreeSnapshot = await getTreeSnapshot(MerkleTreeId.PRIVATE_DATA_TREE);
-      baseRollupOutputRight.endPublicDataTreeRoot = (await getTreeSnapshot(MerkleTreeId.PUBLIC_DATA_TREE)).root;
-
-      // And update the root trees now to create proper output to the root rollup circuit
-      await expectsDb.updateRootsTrees();
-      rootRollupOutput.endContractTreeSnapshot = await getTreeSnapshot(MerkleTreeId.CONTRACT_TREE);
-      rootRollupOutput.endNullifierTreeSnapshot = await getTreeSnapshot(MerkleTreeId.NULLIFIER_TREE);
-      rootRollupOutput.endPrivateDataTreeSnapshot = await getTreeSnapshot(MerkleTreeId.PRIVATE_DATA_TREE);
-      rootRollupOutput.endPublicDataTreeRoot = (await getTreeSnapshot(MerkleTreeId.PUBLIC_DATA_TREE)).root;
-      rootRollupOutput.endTreeOfHistoricContractTreeRootsSnapshot = await getTreeSnapshot(
-        MerkleTreeId.CONTRACT_TREE_ROOTS_TREE,
-      );
-      rootRollupOutput.endTreeOfHistoricPrivateDataTreeRootsSnapshot = await getTreeSnapshot(
-        MerkleTreeId.PRIVATE_DATA_TREE_ROOTS_TREE,
-      );
+      const txs = await buildMockSimulatorInputs();
 
       // Actually build a block!
-      const txs = [tx, await makeEmptyProcessedTx(), await makeEmptyProcessedTx(), await makeEmptyProcessedTx()];
-      const [l2Block, proof] = await builder.buildL2Block(blockNumber, txs);
+      const [l2Block, proof] = await builder.buildL2Block(blockNumber, txs, mockL1ToL2Messages);
 
       expect(l2Block.number).toEqual(blockNumber);
       expect(proof).toEqual(emptyProof);
@@ -170,14 +192,20 @@ describe('sequencer/circuit_block_builder', () => {
       const leaves = nullifiers.map(i => toBufferBE(BigInt(i), 32));
       await expectsDb.appendLeaves(MerkleTreeId.NULLIFIER_TREE, leaves);
 
-      builder = new CircuitBlockBuilder(builderDb, vks, simulator, prover);
-
       await builder.performBaseRollupBatchInsertionProofs(leaves);
 
       const expected = await expectsDb.getTreeInfo(MerkleTreeId.NULLIFIER_TREE);
       const actual = await builderDb.getTreeInfo(MerkleTreeId.NULLIFIER_TREE);
       expect(actual).toEqual(expected);
     });
+
+    it('Rejects if too many l1 to l2 messages are provided', async () => {
+      // Assemble a fake transaction
+      const txs = await buildMockSimulatorInputs();
+      const l1ToL2Messages = new Array(100).fill(new Fr(0n));
+
+      await expect(builder.buildL2Block(blockNumber, txs, l1ToL2Messages)).rejects.toThrow();
+    });
   });
 
   describe('circuits simulator', () => {
@@ -218,7 +246,7 @@ describe('sequencer/circuit_block_builder', () => {
           ...(await Promise.all(times(totalCount - deployCount, makeEmptyProcessedTx))),
         ];
 
-        const [l2Block] = await builder.buildL2Block(blockNumber, txs);
+        const [l2Block] = await builder.buildL2Block(blockNumber, txs, mockL1ToL2Messages);
         expect(l2Block.number).toEqual(blockNumber);
 
         await updateExpectedTreesFromTxs(txs);
@@ -243,7 +271,7 @@ describe('sequencer/circuit_block_builder', () => {
         makeEmptyProcessedTx(),
       ]);
 
-      const [l2Block] = await builder.buildL2Block(blockNumber, txs);
+      const [l2Block] = await builder.buildL2Block(blockNumber, txs, mockL1ToL2Messages);
       expect(l2Block.number).toEqual(blockNumber);
       expect(l2Block.newPublicDataWrites[0]).toEqual(new PublicDataWrite(fr(2), fr(12)));
       await updateExpectedTreesFromTxs(txs);
@@ -274,8 +302,11 @@ describe('sequencer/circuit_block_builder', () => {
       );
       const txs = [tx, await makeEmptyProcessedTx(), await makeEmptyProcessedTx(), await makeEmptyProcessedTx()];
 
-      const [l2Block] = await builder.buildL2Block(blockNumber, txs);
+      const [l2Block] = await builder.buildL2Block(blockNumber, txs, mockL1ToL2Messages);
       expect(l2Block.number).toEqual(blockNumber);
     }, 10000);
   });
+
+  // describe("Input guard tests", () => {
+  // })
 });
diff --git a/yarn-project/sequencer-client/src/block_builder/circuit_block_builder.ts b/yarn-project/sequencer-client/src/block_builder/circuit_block_builder.ts
index c9e946b223c..0ea40b71d95 100644
--- a/yarn-project/sequencer-client/src/block_builder/circuit_block_builder.ts
+++ b/yarn-project/sequencer-client/src/block_builder/circuit_block_builder.ts
@@ -5,9 +5,11 @@ import {
   CONTRACT_TREE_ROOTS_TREE_HEIGHT,
   CircuitsWasm,
   ConstantBaseRollupData,
+  L1_TO_L2_MESSAGES_SUBTREE_INSERTION_HEIGHT,
   MembershipWitness,
   MergeRollupInputs,
   NULLIFIER_TREE_HEIGHT,
+  NUMBER_OF_L1_L2_MESSAGES_PER_ROLLUP,
   NullifierLeafPreimage,
   PRIVATE_DATA_TREE_ROOTS_TREE_HEIGHT,
   PUBLIC_DATA_TREE_HEIGHT,
@@ -36,6 +38,7 @@ import { RollupSimulator } from '../simulator/index.js';
 import { ProcessedTx } from '../sequencer/processed_tx.js';
 import { BlockBuilder } from './index.js';
 import { toFriendlyJSON } from '@aztec/circuits.js/utils';
+import { AllowedTreeNames, OutputWithTreeSnapshot } from './types.js';
 
 const frToBigInt = (fr: Fr) => toBigIntBE(fr.toBuffer());
 const bigintToFr = (num: bigint) => new Fr(num);
@@ -83,7 +86,11 @@ export class CircuitBlockBuilder implements BlockBuilder {
     protected debug = createDebugLogger('aztec:sequencer'),
   ) {}
 
-  public async buildL2Block(blockNumber: number, txs: ProcessedTx[]): Promise<[L2Block, UInt8Vector]> {
+  public async buildL2Block(
+    blockNumber: number,
+    txs: ProcessedTx[],
+    newL1ToL2Messages: Fr[],
+  ): Promise<[L2Block, UInt8Vector]> {
     const [
       startPrivateDataTreeSnapshot,
       startNullifierTreeSnapshot,
@@ -91,6 +98,8 @@ export class CircuitBlockBuilder implements BlockBuilder {
       startPublicDataTreeSnapshot,
       startTreeOfHistoricPrivateDataTreeRootsSnapshot,
       startTreeOfHistoricContractTreeRootsSnapshot,
+      startL1ToL2MessageTreeSnapshot,
+      startTreeOfHistoricL1ToL2MessageTreeRootsSnapshot,
     ] = await Promise.all(
       [
         MerkleTreeId.PRIVATE_DATA_TREE,
@@ -99,6 +108,8 @@ export class CircuitBlockBuilder implements BlockBuilder {
         MerkleTreeId.PUBLIC_DATA_TREE,
         MerkleTreeId.PRIVATE_DATA_TREE_ROOTS_TREE,
         MerkleTreeId.CONTRACT_TREE_ROOTS_TREE,
+        MerkleTreeId.L1_TO_L2_MESSAGES_TREE,
+        MerkleTreeId.L1_TO_L2_MESSAGES_ROOTS_TREE,
       ].map(tree => this.getTreeSnapshot(tree)),
     );
 
@@ -106,7 +117,7 @@ export class CircuitBlockBuilder implements BlockBuilder {
     this.validateTxs(txs);
 
     // We fill the tx batch with empty txs, we process only one tx at a time for now
-    const [circuitsOutput, proof] = await this.runCircuits(txs);
+    const [circuitsOutput, proof] = await this.runCircuits(txs, newL1ToL2Messages);
 
     const {
       endPrivateDataTreeSnapshot,
@@ -115,6 +126,8 @@ export class CircuitBlockBuilder implements BlockBuilder {
       endPublicDataTreeRoot,
       endTreeOfHistoricPrivateDataTreeRootsSnapshot,
       endTreeOfHistoricContractTreeRootsSnapshot,
+      endL1ToL2MessageTreeSnapshot,
+      endTreeOfHistoricL1ToL2MessageTreeRootsSnapshot,
     } = circuitsOutput;
 
     // Collect all new nullifiers, commitments, and contracts from all txs in this block
@@ -143,11 +156,16 @@ export class CircuitBlockBuilder implements BlockBuilder {
       endTreeOfHistoricPrivateDataTreeRootsSnapshot,
       startTreeOfHistoricContractTreeRootsSnapshot,
       endTreeOfHistoricContractTreeRootsSnapshot,
+      startL1ToL2MessageTreeSnapshot,
+      endL1ToL2MessageTreeSnapshot,
+      startTreeOfHistoricL1ToL2MessageTreeRootsSnapshot,
+      endTreeOfHistoricL1ToL2MessageTreeRootsSnapshot,
       newCommitments,
       newNullifiers,
       newContracts,
       newContractData,
       newPublicDataWrites,
+      newL1ToL2Messages,
     });
 
     return [l2Block, proof];
@@ -168,13 +186,20 @@ export class CircuitBlockBuilder implements BlockBuilder {
     return new AppendOnlyTreeSnapshot(Fr.fromBuffer(treeInfo.root), Number(treeInfo.size));
   }
 
-  protected async runCircuits(txs: ProcessedTx[]): Promise<[RootRollupPublicInputs, Proof]> {
+  protected async runCircuits(txs: ProcessedTx[], newL1ToL2Messages: Fr[]): Promise<[RootRollupPublicInputs, Proof]> {
     // Check that the length of the array of txs is a power of two
     // See https://graphics.stanford.edu/~seander/bithacks.html#DetermineIfPowerOf2
     if (txs.length < 4 || (txs.length & (txs.length - 1)) !== 0) {
       throw new Error(`Length of txs for the block should be a power of two and at least four (got ${txs.length})`);
     }
 
+    // Check that the number of new L1 to L2 messages is the same as the max
+    if (newL1ToL2Messages.length !== NUMBER_OF_L1_L2_MESSAGES_PER_ROLLUP) {
+      throw new Error(
+        `Length of the l1 to l2 messages per block should be a constant ${NUMBER_OF_L1_L2_MESSAGES_PER_ROLLUP} (got ${newL1ToL2Messages.length})`,
+      );
+    }
+
     // Run the base rollup circuits for the txs
     const baseRollupOutputs: [BaseOrMergeRollupPublicInputs, Proof][] = [];
     for (const pair of chunk(txs, 2)) {
@@ -196,7 +221,7 @@ export class CircuitBlockBuilder implements BlockBuilder {
 
     // Run the root rollup with the last two merge rollups (or base, if no merge layers)
     const [mergeOutputLeft, mergeOutputRight] = mergeRollupInputs;
-    return this.rootRollupCircuit(mergeOutputLeft, mergeOutputRight);
+    return this.rootRollupCircuit(mergeOutputLeft, mergeOutputRight, newL1ToL2Messages);
   }
 
   protected async baseRollupCircuit(
@@ -241,18 +266,26 @@ export class CircuitBlockBuilder implements BlockBuilder {
   protected async rootRollupCircuit(
     left: [BaseOrMergeRollupPublicInputs, Proof],
     right: [BaseOrMergeRollupPublicInputs, Proof],
+    newL1ToL2Messages: Fr[],
   ): Promise<[RootRollupPublicInputs, Proof]> {
     this.debug(`Running root rollup circuit`);
-    const rootInput = await this.getRootRollupInput(...left, ...right);
+    const rootInput = await this.getRootRollupInput(...left, ...right, newL1ToL2Messages);
+
+    // Update the local trees to include the new l1 to l2 messages
+    await this.db.appendLeaves(
+      MerkleTreeId.L1_TO_L2_MESSAGES_TREE,
+      newL1ToL2Messages.map(m => m.toBuffer()),
+    );
 
     // Simulate and get proof for the root circuit
     const rootOutput = await this.simulator.rootRollupCircuit(rootInput);
+
     const rootProof = await this.prover.getRootRollupProof(rootInput, rootOutput);
 
     // Update the root trees with the latest data and contract tree roots,
     // and validate them against the output of the root circuit simulation
     this.debug(`Updating and validating root trees`);
-    await this.db.updateRootsTrees();
+    await this.db.updateHistoricRootsTrees();
     await this.validateRootOutput(rootOutput);
 
     return [rootOutput, rootProof];
@@ -261,9 +294,9 @@ export class CircuitBlockBuilder implements BlockBuilder {
   // Validate that the new roots we calculated from manual insertions match the outputs of the simulation
   protected async validateTrees(rollupOutput: BaseOrMergeRollupPublicInputs | RootRollupPublicInputs) {
     await Promise.all([
-      this.validateTreeSnapshot(rollupOutput, MerkleTreeId.CONTRACT_TREE, 'Contract'),
-      this.validateTreeSnapshot(rollupOutput, MerkleTreeId.PRIVATE_DATA_TREE, 'PrivateData'),
-      this.validateTreeSnapshot(rollupOutput, MerkleTreeId.NULLIFIER_TREE, 'Nullifier'),
+      this.validateTree(rollupOutput, MerkleTreeId.CONTRACT_TREE, 'Contract'),
+      this.validateTree(rollupOutput, MerkleTreeId.PRIVATE_DATA_TREE, 'PrivateData'),
+      this.validateTree(rollupOutput, MerkleTreeId.NULLIFIER_TREE, 'Nullifier'),
       this.validatePublicDataTreeRoot(rollupOutput),
     ]);
   }
@@ -274,6 +307,8 @@ export class CircuitBlockBuilder implements BlockBuilder {
       this.validateTrees(rootOutput),
       this.validateRootTree(rootOutput, MerkleTreeId.CONTRACT_TREE_ROOTS_TREE, 'Contract'),
       this.validateRootTree(rootOutput, MerkleTreeId.PRIVATE_DATA_TREE_ROOTS_TREE, 'PrivateData'),
+      this.validateRootTree(rootOutput, MerkleTreeId.L1_TO_L2_MESSAGES_ROOTS_TREE, 'L1ToL2Message'),
+      this.validateTree(rootOutput, MerkleTreeId.L1_TO_L2_MESSAGES_TREE, 'L1ToL2Message'),
     ]);
   }
 
@@ -281,7 +316,7 @@ export class CircuitBlockBuilder implements BlockBuilder {
   protected async validateRootTree(
     rootOutput: RootRollupPublicInputs,
     treeId: MerkleTreeId,
-    name: 'Contract' | 'PrivateData',
+    name: 'Contract' | 'PrivateData' | 'L1ToL2Message',
   ) {
     const localTree = await this.getTreeSnapshot(treeId);
     const simulatedTree = rootOutput[`endTreeOfHistoric${name}TreeRootsSnapshot`];
@@ -304,13 +339,17 @@ export class CircuitBlockBuilder implements BlockBuilder {
   }
 
   // Helper for validating a non-roots tree against a circuit simulation output
-  protected async validateTreeSnapshot(
-    output: BaseOrMergeRollupPublicInputs | RootRollupPublicInputs,
+  protected async validateTree<T extends BaseOrMergeRollupPublicInputs | RootRollupPublicInputs>(
+    output: T,
     treeId: MerkleTreeId,
-    name: 'PrivateData' | 'Contract' | 'Nullifier',
+    name: AllowedTreeNames<T>,
   ) {
+    if ('endL1ToL2MessageTreeSnapshot' in output && !(output instanceof RootRollupPublicInputs)) {
+      throw new Error(`The name 'L1ToL2Message' can only be used when output is of type RootRollupPublicInputs`);
+    }
+
     const localTree = await this.getTreeSnapshot(treeId);
-    const simulatedTree = output[`end${name}TreeSnapshot`];
+    const simulatedTree = (output as OutputWithTreeSnapshot<T>)[`end${name}TreeSnapshot`];
     this.validateSimulatedTree(localTree, simulatedTree, name);
   }
 
@@ -318,7 +357,7 @@ export class CircuitBlockBuilder implements BlockBuilder {
   protected validateSimulatedTree(
     localTree: AppendOnlyTreeSnapshot,
     simulatedTree: AppendOnlyTreeSnapshot,
-    name: 'PrivateData' | 'Contract' | 'Nullifier',
+    name: 'PrivateData' | 'Contract' | 'Nullifier' | 'L1ToL2Message',
     label?: string,
   ) {
     if (!simulatedTree.root.toBuffer().equals(localTree.root.toBuffer())) {
@@ -339,6 +378,7 @@ export class CircuitBlockBuilder implements BlockBuilder {
     rollupProofLeft: Proof,
     rollupOutputRight: BaseOrMergeRollupPublicInputs,
     rollupProofRight: Proof,
+    newL1ToL2Messages: Fr[],
   ) {
     const vk = this.getVerificationKey(rollupOutputLeft.rollupType);
     const previousRollupData: RootRollupInputs['previousRollupData'] = [
@@ -360,11 +400,29 @@ export class CircuitBlockBuilder implements BlockBuilder {
     const newHistoricPrivateDataTreeRootSiblingPath = await getRootTreeSiblingPath(
       MerkleTreeId.PRIVATE_DATA_TREE_ROOTS_TREE,
     );
+    const newHistoricL1ToL2MessageTreeRootSiblingPath = await getRootTreeSiblingPath(
+      MerkleTreeId.L1_TO_L2_MESSAGES_ROOTS_TREE,
+    );
+    const newL1ToL2MessageTreeRootSiblingPath = await this.getSubtreeSiblingPath(
+      MerkleTreeId.L1_TO_L2_MESSAGES_TREE,
+      L1_TO_L2_MESSAGES_SUBTREE_INSERTION_HEIGHT,
+    );
+
+    // Get tree snapshots
+    const startL1ToL2MessageTreeSnapshot = await this.getTreeSnapshot(MerkleTreeId.L1_TO_L2_MESSAGES_TREE);
+    const startHistoricTreeL1ToL2MessageTreeRootsSnapshot = await this.getTreeSnapshot(
+      MerkleTreeId.L1_TO_L2_MESSAGES_ROOTS_TREE,
+    );
 
     return RootRollupInputs.from({
       previousRollupData,
       newHistoricContractDataTreeRootSiblingPath,
       newHistoricPrivateDataTreeRootSiblingPath,
+      newL1ToL2Messages,
+      newHistoricL1ToL2MessageTreeRootSiblingPath,
+      newL1ToL2MessageTreeRootSiblingPath,
+      startL1ToL2MessageTreeSnapshot,
+      startHistoricTreeL1ToL2MessageTreeRootsSnapshot,
     });
   }
 
diff --git a/yarn-project/sequencer-client/src/block_builder/index.ts b/yarn-project/sequencer-client/src/block_builder/index.ts
index 8859a405a7a..72a930476e6 100644
--- a/yarn-project/sequencer-client/src/block_builder/index.ts
+++ b/yarn-project/sequencer-client/src/block_builder/index.ts
@@ -1,7 +1,8 @@
 import { L2Block } from '@aztec/types';
 import { Proof } from '../prover/index.js';
 import { ProcessedTx } from '../sequencer/processed_tx.js';
+import { Fr } from '@aztec/foundation';
 
 export interface BlockBuilder {
-  buildL2Block(blockNumber: number, txs: ProcessedTx[]): Promise<[L2Block, Proof]>;
+  buildL2Block(blockNumber: number, txs: ProcessedTx[], newL1ToL2Messages: Fr[]): Promise<[L2Block, Proof]>;
 }
diff --git a/yarn-project/sequencer-client/src/block_builder/standalone_block_builder.ts b/yarn-project/sequencer-client/src/block_builder/standalone_block_builder.ts
index f103d029a3e..b60455977d9 100644
--- a/yarn-project/sequencer-client/src/block_builder/standalone_block_builder.ts
+++ b/yarn-project/sequencer-client/src/block_builder/standalone_block_builder.ts
@@ -31,7 +31,7 @@ export class StandaloneBlockBuilder implements BlockBuilder {
 
   constructor(private db: MerkleTreeOperations, private log = createDebugLogger('aztec:block_builder')) {}
 
-  async buildL2Block(blockNumber: number, txs: ProcessedTx[]): Promise<[L2Block, Proof]> {
+  async buildL2Block(blockNumber: number, txs: ProcessedTx[], newL1ToL2Messages: Fr[]): Promise<[L2Block, Proof]> {
     const startPrivateDataTreeSnapshot = await this.getTreeSnapshot(MerkleTreeId.PRIVATE_DATA_TREE);
     const startNullifierTreeSnapshot = await this.getTreeSnapshot(MerkleTreeId.NULLIFIER_TREE);
     const startContractTreeSnapshot = await this.getTreeSnapshot(MerkleTreeId.CONTRACT_TREE);
@@ -42,10 +42,15 @@ export class StandaloneBlockBuilder implements BlockBuilder {
     const startTreeOfHistoricContractTreeRootsSnapshot = await this.getTreeSnapshot(
       MerkleTreeId.CONTRACT_TREE_ROOTS_TREE,
     );
+    const startL1ToL2MessageTreeSnapshot = await this.getTreeSnapshot(MerkleTreeId.L1_TO_L2_MESSAGES_TREE);
+    const startTreeOfHistoricL1ToL2MessageTreeRootsSnapshot = await this.getTreeSnapshot(
+      MerkleTreeId.L1_TO_L2_MESSAGES_ROOTS_TREE,
+    );
 
     for (const tx of txs) {
       await this.updateTrees(tx);
     }
+    await this.updateL1ToL2MessagesTree(newL1ToL2Messages);
 
     await this.updateRootTrees();
 
@@ -59,6 +64,10 @@ export class StandaloneBlockBuilder implements BlockBuilder {
     const endTreeOfHistoricContractTreeRootsSnapshot = await this.getTreeSnapshot(
       MerkleTreeId.CONTRACT_TREE_ROOTS_TREE,
     );
+    const endL1ToL2MessageTreeSnapshot = await this.getTreeSnapshot(MerkleTreeId.L1_TO_L2_MESSAGES_TREE);
+    const endTreeOfHistoricL1ToL2MessageTreeRootsSnapshot = await this.getTreeSnapshot(
+      MerkleTreeId.L1_TO_L2_MESSAGES_ROOTS_TREE,
+    );
 
     const l2Block = L2Block.fromFields({
       number: blockNumber,
@@ -74,6 +83,10 @@ export class StandaloneBlockBuilder implements BlockBuilder {
       endTreeOfHistoricPrivateDataTreeRootsSnapshot,
       startTreeOfHistoricContractTreeRootsSnapshot,
       endTreeOfHistoricContractTreeRootsSnapshot,
+      startL1ToL2MessageTreeSnapshot,
+      endL1ToL2MessageTreeSnapshot,
+      startTreeOfHistoricL1ToL2MessageTreeRootsSnapshot,
+      endTreeOfHistoricL1ToL2MessageTreeRootsSnapshot,
       newCommitments: this.dataTreeLeaves.map(b => Fr.fromBuffer(b)),
       newNullifiers: this.nullifierTreeLeaves.map(b => Fr.fromBuffer(b)),
       newContracts: this.contractTreeLeaves.map(b => Fr.fromBuffer(b)),
@@ -81,6 +94,7 @@ export class StandaloneBlockBuilder implements BlockBuilder {
       newPublicDataWrites: txs.flatMap(tx =>
         tx.data.end.stateTransitions.map(t => new PublicDataWrite(t.leafIndex, t.newValue)),
       ),
+      newL1ToL2Messages,
     });
     return [l2Block, makeEmptyProof()];
   }
@@ -98,21 +112,22 @@ export class StandaloneBlockBuilder implements BlockBuilder {
       computeContractLeaf(wasm, x).toBuffer(),
     );
 
-    for (let i = 0; i < KERNEL_NEW_COMMITMENTS_LENGTH; i++) {
-      await this.db.appendLeaves(MerkleTreeId.PRIVATE_DATA_TREE, [dataTreeLeaves[i]]);
-    }
-    for (let i = 0; i < KERNEL_NEW_NULLIFIERS_LENGTH; i++) {
-      await this.db.appendLeaves(MerkleTreeId.NULLIFIER_TREE, [nullifierTreeLeaves[i]]);
-    }
-    for (let i = 0; i < KERNEL_NEW_CONTRACTS_LENGTH; i++) {
-      await this.db.appendLeaves(MerkleTreeId.CONTRACT_TREE, [contractTreeLeaves[i]]);
-    }
+    await this.db.appendLeaves(MerkleTreeId.PRIVATE_DATA_TREE, dataTreeLeaves);
+    await this.db.appendLeaves(MerkleTreeId.NULLIFIER_TREE, nullifierTreeLeaves);
+    await this.db.appendLeaves(MerkleTreeId.CONTRACT_TREE, contractTreeLeaves);
+  }
+
+  private async updateL1ToL2MessagesTree(l1ToL2Messages: Fr[]) {
+    const leaves = l1ToL2Messages.map((x: Fr) => x.toBuffer());
+    await this.db.appendLeaves(MerkleTreeId.L1_TO_L2_MESSAGES_TREE, leaves);
   }
 
   private async updateRootTrees() {
     const newDataTreeInfo = await this.getTreeSnapshot(MerkleTreeId.PRIVATE_DATA_TREE);
     const newContractsTreeInfo = await this.getTreeSnapshot(MerkleTreeId.CONTRACT_TREE);
+    const newL1ToL2MessagesTreeInfo = await this.getTreeSnapshot(MerkleTreeId.L1_TO_L2_MESSAGES_TREE);
     await this.db.appendLeaves(MerkleTreeId.CONTRACT_TREE_ROOTS_TREE, [newContractsTreeInfo.root.toBuffer()]);
     await this.db.appendLeaves(MerkleTreeId.PRIVATE_DATA_TREE_ROOTS_TREE, [newDataTreeInfo.root.toBuffer()]);
+    await this.db.appendLeaves(MerkleTreeId.L1_TO_L2_MESSAGES_ROOTS_TREE, [newL1ToL2MessagesTreeInfo.root.toBuffer()]);
   }
 }
diff --git a/yarn-project/sequencer-client/src/block_builder/types.ts b/yarn-project/sequencer-client/src/block_builder/types.ts
new file mode 100644
index 00000000000..d3fc4845051
--- /dev/null
+++ b/yarn-project/sequencer-client/src/block_builder/types.ts
@@ -0,0 +1,16 @@
+import { AppendOnlyTreeSnapshot, BaseOrMergeRollupPublicInputs, RootRollupPublicInputs } from '@aztec/circuits.js';
+
+/**
+ * Type to assert that only the correct trees are checked when validating rollup tree outputs
+ */
+export type AllowedTreeNames<T extends BaseOrMergeRollupPublicInputs | RootRollupPublicInputs> =
+  T extends RootRollupPublicInputs
+    ? 'PrivateData' | 'Contract' | 'Nullifier' | 'L1ToL2Message'
+    : 'PrivateData' | 'Contract' | 'Nullifier';
+
+/**
+ * Type to assert the correct object field is indexed when validating rollup tree outputs
+ */
+export type OutputWithTreeSnapshot<T extends BaseOrMergeRollupPublicInputs | RootRollupPublicInputs> = {
+  [K in `end${AllowedTreeNames<T>}TreeSnapshot`]: AppendOnlyTreeSnapshot;
+};
diff --git a/yarn-project/sequencer-client/src/sequencer/sequencer.test.ts b/yarn-project/sequencer-client/src/sequencer/sequencer.test.ts
index f55205937c9..e39d672b744 100644
--- a/yarn-project/sequencer-client/src/sequencer/sequencer.test.ts
+++ b/yarn-project/sequencer-client/src/sequencer/sequencer.test.ts
@@ -1,4 +1,4 @@
-import { CombinedHistoricTreeRoots, makeEmptyProof } from '@aztec/circuits.js';
+import { CombinedHistoricTreeRoots, Fr, NUMBER_OF_L1_L2_MESSAGES_PER_ROLLUP, makeEmptyProof } from '@aztec/circuits.js';
 import { P2P, P2PClientState } from '@aztec/p2p';
 import { L2Block, PrivateTx, Tx, UnverifiedData } from '@aztec/types';
 import { MerkleTreeId, MerkleTreeOperations, WorldStateRunningState, WorldStateSynchroniser } from '@aztec/world-state';
@@ -65,6 +65,7 @@ describe('sequencer', () => {
     expect(blockBuilder.buildL2Block).toHaveBeenCalledWith(
       lastBlockNumber + 1,
       expectedTxHashes.map(hash => expect.objectContaining({ hash })),
+      Array(NUMBER_OF_L1_L2_MESSAGES_PER_ROLLUP).fill(new Fr(0n)),
     );
     expect(publisher.processL2Block).toHaveBeenCalledWith(block);
     expect(publisher.processUnverifiedData).toHaveBeenCalledWith(lastBlockNumber + 1, expectedUnverifiedData);
@@ -101,6 +102,7 @@ describe('sequencer', () => {
     expect(blockBuilder.buildL2Block).toHaveBeenCalledWith(
       lastBlockNumber + 1,
       expectedTxHashes.map(hash => expect.objectContaining({ hash })),
+      Array(NUMBER_OF_L1_L2_MESSAGES_PER_ROLLUP).fill(new Fr(0n)),
     );
     expect(publisher.processL2Block).toHaveBeenCalledWith(block);
     expect(publisher.processUnverifiedData).toHaveBeenCalledWith(lastBlockNumber + 1, expectedUnverifiedData);
diff --git a/yarn-project/sequencer-client/src/sequencer/sequencer.ts b/yarn-project/sequencer-client/src/sequencer/sequencer.ts
index e7cd3442422..04d17edd3c9 100644
--- a/yarn-project/sequencer-client/src/sequencer/sequencer.ts
+++ b/yarn-project/sequencer-client/src/sequencer/sequencer.ts
@@ -1,4 +1,4 @@
-import { RunningPromise, createDebugLogger } from '@aztec/foundation';
+import { Fr, RunningPromise, createDebugLogger } from '@aztec/foundation';
 import { P2P } from '@aztec/p2p';
 import { ContractData, ContractPublicData, PrivateTx, PublicTx, Tx, UnverifiedData, isPrivateTx } from '@aztec/types';
 import { MerkleTreeId, WorldStateStatus, WorldStateSynchroniser } from '@aztec/world-state';
@@ -9,6 +9,7 @@ import { ceilPowerOfTwo } from '../utils.js';
 import { SequencerConfig } from './config.js';
 import { ProcessedTx } from './processed_tx.js';
 import { PublicProcessor } from './public_processor.js';
+import { NUMBER_OF_L1_L2_MESSAGES_PER_ROLLUP } from '@aztec/circuits.js';
 
 /**
  * Sequencer client
@@ -111,9 +112,14 @@ export class Sequencer {
         await this.p2pClient.deleteTxs(await Tx.getHashes(failedTxs));
       }
 
+      // Get l1 to l2 messages from the contract
+      this.log('Requesting L1 to L2 messages from contract');
+      const l1ToL2Messages = this.takeL1ToL2MessagesFromContract();
+      this.log('Successfully retrieved L1 to L2 messages from contract');
+
       // Build the new block by running the rollup circuits
       this.log(`Assembling block with txs ${processedTxs.map(tx => tx.hash).join(', ')}`);
-      const block = await this.buildBlock(processedTxs);
+      const block = await this.buildBlock(processedTxs, l1ToL2Messages);
       this.log(`Assembled block ${block.number}`);
 
       // Publishes new block to the network and awaits the tx to be mined
@@ -209,7 +215,7 @@ export class Sequencer {
     );
   }
 
-  protected async buildBlock(txs: ProcessedTx[]) {
+  protected async buildBlock(txs: ProcessedTx[], newL1ToL2Messages: Fr[]) {
     // Pad the txs array with empty txs to be a power of two, at least 4
     const txsTargetSize = Math.max(ceilPowerOfTwo(txs.length), 4);
     const emptyTxCount = txsTargetSize - txs.length;
@@ -218,10 +224,19 @@ export class Sequencer {
       ...txs,
       ...(await Promise.all(times(emptyTxCount, () => this.publicProcessor.makeEmptyProcessedTx()))),
     ];
-    const [block] = await this.blockBuilder.buildL2Block(this.lastBlockNumber + 1, allTxs);
+    const [block] = await this.blockBuilder.buildL2Block(this.lastBlockNumber + 1, allTxs, newL1ToL2Messages);
     return block;
   }
 
+  // TODO: this is a stubbed method
+  /**
+   * Checks on chain messages inbox and selects messages to inlcude within the
+   * next rollup block
+   */
+  protected takeL1ToL2MessagesFromContract(): Fr[] {
+    return new Array(NUMBER_OF_L1_L2_MESSAGES_PER_ROLLUP).fill(new Fr(0n));
+  }
+
   /**
    * Returns true if one of the transaction nullifiers exist.
    * Nullifiers prevent double spends in a private context.
diff --git a/yarn-project/sequencer-client/src/test/l2-block-publisher.test.ts b/yarn-project/sequencer-client/src/test/l2-block-publisher.test.ts
index d5d56d81816..774b2650ce6 100644
--- a/yarn-project/sequencer-client/src/test/l2-block-publisher.test.ts
+++ b/yarn-project/sequencer-client/src/test/l2-block-publisher.test.ts
@@ -3,6 +3,7 @@ import {
   BaseOrMergeRollupPublicInputs,
   CircuitsWasm,
   Fr,
+  NUMBER_OF_L1_L2_MESSAGES_PER_ROLLUP,
   RootRollupPublicInputs,
   UInt8Vector,
 } from '@aztec/circuits.js';
@@ -68,8 +69,8 @@ describe.skip('L1Publisher integration', () => {
     const simulator = await WasmRollupCircuitSimulator.new();
     const prover = new EmptyRollupProver();
     builder = new CircuitBlockBuilder(builderDb, vks, simulator, prover);
-    await expectsDb.updateRootsTrees();
-    await builderDb.updateRootsTrees();
+    await expectsDb.updateHistoricRootsTrees();
+    await builderDb.updateHistoricRootsTrees();
 
     baseRollupOutputLeft = makeBaseRollupPublicInputs();
     baseRollupOutputRight = makeBaseRollupPublicInputs();
@@ -97,6 +98,8 @@ describe.skip('L1Publisher integration', () => {
   };
 
   it('Build 2 blocks of 4 txs building on each other', async () => {
+    const newL1ToL2Messages = new Array(NUMBER_OF_L1_L2_MESSAGES_PER_ROLLUP).fill(new Fr(0n));
+
     const stateInRollup_ = await rollup.methods.rollupStateHash().call();
     expect(hexStringToBuffer(stateInRollup_.toString())).toEqual(Buffer.alloc(32, 0));
 
@@ -105,7 +108,7 @@ describe.skip('L1Publisher integration', () => {
         Tx.createPrivate(makeKernelPublicInputs(1 + i), emptyProof, makeEmptyUnverifiedData()),
       );
 
-      const txsLeft = [tx, await makeEmptyProcessedTx()];
+      const txsLeft = [await makeEmptyProcessedTx(), await makeEmptyProcessedTx()];
       const txsRight = [await makeEmptyProcessedTx(), await makeEmptyProcessedTx()];
 
       // Set tree roots to proper values in the tx
@@ -124,7 +127,7 @@ describe.skip('L1Publisher integration', () => {
       baseRollupOutputRight.endPrivateDataTreeSnapshot = await getTreeSnapshot(MerkleTreeId.PRIVATE_DATA_TREE);
 
       // And update the root trees now to create proper output to the root rollup circuit
-      await expectsDb.updateRootsTrees();
+      await expectsDb.updateHistoricRootsTrees();
       rootRollupOutput.endContractTreeSnapshot = await getTreeSnapshot(MerkleTreeId.CONTRACT_TREE);
       rootRollupOutput.endNullifierTreeSnapshot = await getTreeSnapshot(MerkleTreeId.NULLIFIER_TREE);
       rootRollupOutput.endPrivateDataTreeSnapshot = await getTreeSnapshot(MerkleTreeId.PRIVATE_DATA_TREE);
@@ -137,8 +140,7 @@ describe.skip('L1Publisher integration', () => {
 
       // Actually build a block!
       const txs = [tx, await makeEmptyProcessedTx(), await makeEmptyProcessedTx(), await makeEmptyProcessedTx()];
-      // Here we die.
-      const [block] = await builder.buildL2Block(1 + i, txs);
+      const [block] = await builder.buildL2Block(1 + i, txs, newL1ToL2Messages);
 
       // Now we can use the block we built!
       const blockNumber = await ethRpc.blockNumber();
@@ -151,7 +153,7 @@ describe.skip('L1Publisher integration', () => {
       const expectedData = rollup.methods.process(l2Proof, block.encode()).encodeABI();
       expect(ethTx.input).toEqual(expectedData);
 
-      const decodedCalldataHash = await decoderHelper.methods.computeDiffRoot(block.encode()).call();
+      const decodedHashes = await decoderHelper.methods.computeDiffRootAndMessagesHash(block.encode()).call();
       const decodedRes = await decoderHelper.methods.decode(block.encode()).call();
       const stateInRollup = await rollup.methods.rollupStateHash().call();
 
@@ -161,7 +163,8 @@ describe.skip('L1Publisher integration', () => {
       expect(block.getEndStateHash()).toEqual(hexStringToBuffer(decodedRes[2].toString()));
       expect(block.getEndStateHash()).toEqual(hexStringToBuffer(stateInRollup.toString()));
       expect(block.getPublicInputsHash().toBuffer()).toEqual(hexStringToBuffer(decodedRes[3].toString()));
-      expect(block.getCalldataHash()).toEqual(hexStringToBuffer(decodedCalldataHash.toString()));
+      expect(block.getCalldataHash()).toEqual(hexStringToBuffer(decodedHashes[0].toString()));
+      expect(block.getL1ToL2MessagesHash()).toEqual(hexStringToBuffer(decodedHashes[1].toString()));
     }
   }, 60_000);
 
diff --git a/yarn-project/types/src/l2_block.ts b/yarn-project/types/src/l2_block.ts
index 17e97e6e572..9cb32f3936e 100644
--- a/yarn-project/types/src/l2_block.ts
+++ b/yarn-project/types/src/l2_block.ts
@@ -4,6 +4,7 @@ import {
   KERNEL_NEW_CONTRACTS_LENGTH,
   KERNEL_NEW_NULLIFIERS_LENGTH,
   STATE_TRANSITIONS_LENGTH,
+  NUMBER_OF_L1_L2_MESSAGES_PER_ROLLUP,
 } from '@aztec/circuits.js';
 import { makeAppendOnlyTreeSnapshot } from '@aztec/circuits.js/factories';
 import { BufferReader, serializeToBuffer } from '@aztec/circuits.js/utils';
@@ -28,17 +29,22 @@ export class L2Block {
    * @param startTreeOfHistoricPrivateDataTreeRootsSnapshot - The tree snapshot of the historic private data tree roots at the start of the rollup.
    * @param startTreeOfHistoricContractTreeRootsSnapshot - The tree snapshot of the historic contract tree roots at the start of the rollup.
    * @param startPublicDataTreeRoot - The tree root of the public data tree at the start of the rollup.
+   * @param startL1ToL2MessageTreeSnapshot - The tree snapshot of the L2 message tree at the start of the rollup.
+   * @param startTreeOfHistoricL1ToL2MessageTreeRootsSnapshot - The tree snapshot of the historic L2 message tree roots at the start of the rollup.
    * @param endPrivateDataTreeSnapshot - The tree snapshot of the private data tree at the end of the rollup.
    * @param endNullifierTreeSnapshot - The tree snapshot of the nullifier tree at the end of the rollup.
    * @param endContractTreeSnapshot - The tree snapshot of the contract tree at the end of the rollup.
    * @param endTreeOfHistoricPrivateDataTreeRootsSnapshot - The tree snapshot of the historic private data tree roots at the end of the rollup.
    * @param endTreeOfHistoricContractTreeRootsSnapshot - The tree snapshot of the historic contract tree roots at the end of the rollup.
    * @param endPublicDataTreeRoot - The tree root of the public data tree at the end of the rollup.
+   * @param endL1ToL2MessageTreeSnapshot - The tree snapshot of the L2 message tree at the end of the rollup.
+   * @param endTreeOfHistoricL1ToL2MessageTreeRootsSnapshot - The tree snapshot of the historic L2 message tree roots at the end of the rollup.
    * @param newCommitments - The commitments to be inserted into the private data tree.
    * @param newNullifiers - The nullifiers to be inserted into the nullifier tree.
    * @param newPublicDataWrites - The public data writes to be inserted into the public data tree.
    * @param newContracts - The contracts leafs to be inserted into the contract tree.
    * @param newContractData - The aztec_address and eth_address for the deployed contract and its portal contract.
+   * @param newL1ToL2Messages - The L1 to L2 messages to be inserted into the L2 toL2 message tree.
    */
   constructor(
     public number: number,
@@ -48,17 +54,22 @@ export class L2Block {
     public startTreeOfHistoricPrivateDataTreeRootsSnapshot: AppendOnlyTreeSnapshot,
     public startTreeOfHistoricContractTreeRootsSnapshot: AppendOnlyTreeSnapshot,
     public startPublicDataTreeRoot: Fr,
+    public startL1ToL2MessageTreeSnapshot: AppendOnlyTreeSnapshot,
+    public startTreeOfHistoricL1ToL2MessageTreeRootsSnapshot: AppendOnlyTreeSnapshot,
     public endPrivateDataTreeSnapshot: AppendOnlyTreeSnapshot,
     public endNullifierTreeSnapshot: AppendOnlyTreeSnapshot,
     public endContractTreeSnapshot: AppendOnlyTreeSnapshot,
     public endTreeOfHistoricPrivateDataTreeRootsSnapshot: AppendOnlyTreeSnapshot,
     public endTreeOfHistoricContractTreeRootsSnapshot: AppendOnlyTreeSnapshot,
     public endPublicDataTreeRoot: Fr,
+    public endL1ToL2MessageTreeSnapshot: AppendOnlyTreeSnapshot,
+    public endTreeOfHistoricL1ToL2MessageTreeRootsSnapshot: AppendOnlyTreeSnapshot,
     public newCommitments: Fr[],
     public newNullifiers: Fr[],
     public newPublicDataWrites: PublicDataWrite[],
     public newContracts: Fr[],
     public newContractData: ContractData[],
+    public newL1ToL2Messages: Fr[] = [],
   ) {}
 
   static random(l2BlockNum: number, txsPerBlock = 4) {
@@ -67,6 +78,7 @@ export class L2Block {
     const newContracts = times(KERNEL_NEW_CONTRACTS_LENGTH * txsPerBlock, Fr.random);
     const newContractData = times(KERNEL_NEW_CONTRACTS_LENGTH * txsPerBlock, ContractData.random);
     const newPublicDataWrites = times(STATE_TRANSITIONS_LENGTH * txsPerBlock, PublicDataWrite.random);
+    const newL1ToL2Messages = times(NUMBER_OF_L1_L2_MESSAGES_PER_ROLLUP, Fr.random);
 
     return L2Block.fromFields({
       number: l2BlockNum,
@@ -74,12 +86,16 @@ export class L2Block {
       startNullifierTreeSnapshot: makeAppendOnlyTreeSnapshot(0),
       startContractTreeSnapshot: makeAppendOnlyTreeSnapshot(0),
       startPublicDataTreeRoot: Fr.random(),
+      startL1ToL2MessageTreeSnapshot: makeAppendOnlyTreeSnapshot(0),
+      startTreeOfHistoricL1ToL2MessageTreeRootsSnapshot: makeAppendOnlyTreeSnapshot(0),
       startTreeOfHistoricPrivateDataTreeRootsSnapshot: makeAppendOnlyTreeSnapshot(0),
       startTreeOfHistoricContractTreeRootsSnapshot: makeAppendOnlyTreeSnapshot(0),
       endPrivateDataTreeSnapshot: makeAppendOnlyTreeSnapshot(newCommitments.length),
       endNullifierTreeSnapshot: makeAppendOnlyTreeSnapshot(newNullifiers.length),
       endContractTreeSnapshot: makeAppendOnlyTreeSnapshot(newContracts.length),
       endPublicDataTreeRoot: Fr.random(),
+      endL1ToL2MessageTreeSnapshot: makeAppendOnlyTreeSnapshot(1),
+      endTreeOfHistoricL1ToL2MessageTreeRootsSnapshot: makeAppendOnlyTreeSnapshot(1),
       endTreeOfHistoricPrivateDataTreeRootsSnapshot: makeAppendOnlyTreeSnapshot(1),
       endTreeOfHistoricContractTreeRootsSnapshot: makeAppendOnlyTreeSnapshot(1),
       newCommitments,
@@ -87,6 +103,7 @@ export class L2Block {
       newContracts,
       newContractData,
       newPublicDataWrites,
+      newL1ToL2Messages,
     });
   }
 
@@ -103,17 +120,22 @@ export class L2Block {
     startTreeOfHistoricPrivateDataTreeRootsSnapshot: AppendOnlyTreeSnapshot;
     startTreeOfHistoricContractTreeRootsSnapshot: AppendOnlyTreeSnapshot;
     startPublicDataTreeRoot: Fr;
+    startL1ToL2MessageTreeSnapshot: AppendOnlyTreeSnapshot;
+    startTreeOfHistoricL1ToL2MessageTreeRootsSnapshot: AppendOnlyTreeSnapshot;
     endPrivateDataTreeSnapshot: AppendOnlyTreeSnapshot;
     endNullifierTreeSnapshot: AppendOnlyTreeSnapshot;
     endContractTreeSnapshot: AppendOnlyTreeSnapshot;
     endTreeOfHistoricPrivateDataTreeRootsSnapshot: AppendOnlyTreeSnapshot;
     endTreeOfHistoricContractTreeRootsSnapshot: AppendOnlyTreeSnapshot;
     endPublicDataTreeRoot: Fr;
+    endL1ToL2MessageTreeSnapshot: AppendOnlyTreeSnapshot;
+    endTreeOfHistoricL1ToL2MessageTreeRootsSnapshot: AppendOnlyTreeSnapshot;
     newCommitments: Fr[];
     newNullifiers: Fr[];
     newPublicDataWrites: PublicDataWrite[];
     newContracts: Fr[];
     newContractData: ContractData[];
+    newL1ToL2Messages: Fr[];
   }) {
     return new this(
       fields.number,
@@ -123,17 +145,22 @@ export class L2Block {
       fields.startTreeOfHistoricPrivateDataTreeRootsSnapshot,
       fields.startTreeOfHistoricContractTreeRootsSnapshot,
       fields.startPublicDataTreeRoot,
+      fields.startL1ToL2MessageTreeSnapshot,
+      fields.startTreeOfHistoricL1ToL2MessageTreeRootsSnapshot,
       fields.endPrivateDataTreeSnapshot,
       fields.endNullifierTreeSnapshot,
       fields.endContractTreeSnapshot,
       fields.endTreeOfHistoricPrivateDataTreeRootsSnapshot,
       fields.endTreeOfHistoricContractTreeRootsSnapshot,
       fields.endPublicDataTreeRoot,
+      fields.endL1ToL2MessageTreeSnapshot,
+      fields.endTreeOfHistoricL1ToL2MessageTreeRootsSnapshot,
       fields.newCommitments,
       fields.newNullifiers,
       fields.newPublicDataWrites,
       fields.newContracts,
       fields.newContractData,
+      fields.newL1ToL2Messages,
     );
   }
 
@@ -150,12 +177,16 @@ export class L2Block {
       this.startTreeOfHistoricPrivateDataTreeRootsSnapshot,
       this.startTreeOfHistoricContractTreeRootsSnapshot,
       this.startPublicDataTreeRoot,
+      this.startL1ToL2MessageTreeSnapshot,
+      this.startTreeOfHistoricL1ToL2MessageTreeRootsSnapshot,
       this.endPrivateDataTreeSnapshot,
       this.endNullifierTreeSnapshot,
       this.endContractTreeSnapshot,
       this.endTreeOfHistoricPrivateDataTreeRootsSnapshot,
       this.endTreeOfHistoricContractTreeRootsSnapshot,
       this.endPublicDataTreeRoot,
+      this.endL1ToL2MessageTreeSnapshot,
+      this.endTreeOfHistoricL1ToL2MessageTreeRootsSnapshot,
       this.newCommitments.length,
       this.newCommitments,
       this.newNullifiers.length,
@@ -165,6 +196,8 @@ export class L2Block {
       this.newContracts.length,
       this.newContracts,
       this.newContractData,
+      this.newL1ToL2Messages.length,
+      this.newL1ToL2Messages,
     );
   }
 
@@ -190,17 +223,23 @@ export class L2Block {
     const startTreeOfHistoricPrivateDataTreeRootsSnapshot = reader.readObject(AppendOnlyTreeSnapshot);
     const startTreeOfHistoricContractTreeRootsSnapshot = reader.readObject(AppendOnlyTreeSnapshot);
     const startPublicDataTreeRoot = reader.readObject(Fr);
+    const startL1ToL2MessageTreeSnapshot = reader.readObject(AppendOnlyTreeSnapshot);
+    const startTreeOfHistoricL1ToL2MessageTreeRootsSnapshot = reader.readObject(AppendOnlyTreeSnapshot);
     const endPrivateDataTreeSnapshot = reader.readObject(AppendOnlyTreeSnapshot);
     const endNullifierTreeSnapshot = reader.readObject(AppendOnlyTreeSnapshot);
     const endContractTreeSnapshot = reader.readObject(AppendOnlyTreeSnapshot);
     const endTreeOfHistoricPrivateDataTreeRootsSnapshot = reader.readObject(AppendOnlyTreeSnapshot);
     const endTreeOfHistoricContractTreeRootsSnapshot = reader.readObject(AppendOnlyTreeSnapshot);
     const endPublicDataTreeRoot = reader.readObject(Fr);
+    const endL1ToL2MessageTreeSnapshot = reader.readObject(AppendOnlyTreeSnapshot);
+    const endTreeOfHistoricL1ToL2MessageTreeRootsSnapshot = reader.readObject(AppendOnlyTreeSnapshot);
     const newCommitments = reader.readVector(Fr);
     const newNullifiers = reader.readVector(Fr);
     const newPublicDataWrites = reader.readVector(PublicDataWrite);
     const newContracts = reader.readVector(Fr);
     const newContractData = reader.readArray(newContracts.length, ContractData);
+    // TODO(sean): could an optimisation of this be that it is encoded such that zeros are assumed
+    const newL1ToL2Messages = reader.readVector(Fr);
 
     return L2Block.fromFields({
       number,
@@ -210,17 +249,22 @@ export class L2Block {
       startTreeOfHistoricPrivateDataTreeRootsSnapshot,
       startTreeOfHistoricContractTreeRootsSnapshot,
       startPublicDataTreeRoot,
+      startL1ToL2MessageTreeSnapshot,
+      startTreeOfHistoricL1ToL2MessageTreeRootsSnapshot,
       endPrivateDataTreeSnapshot,
       endNullifierTreeSnapshot,
       endContractTreeSnapshot,
       endTreeOfHistoricPrivateDataTreeRootsSnapshot,
       endTreeOfHistoricContractTreeRootsSnapshot,
       endPublicDataTreeRoot,
+      endL1ToL2MessageTreeSnapshot,
+      endTreeOfHistoricL1ToL2MessageTreeRootsSnapshot,
       newCommitments,
       newNullifiers,
       newPublicDataWrites,
       newContracts,
       newContractData,
+      newL1ToL2Messages,
     });
   }
 
@@ -237,14 +281,20 @@ export class L2Block {
       this.startTreeOfHistoricPrivateDataTreeRootsSnapshot,
       this.startTreeOfHistoricContractTreeRootsSnapshot,
       this.startPublicDataTreeRoot,
+      this.startL1ToL2MessageTreeSnapshot,
+      this.startTreeOfHistoricL1ToL2MessageTreeRootsSnapshot,
       this.endPrivateDataTreeSnapshot,
       this.endNullifierTreeSnapshot,
       this.endContractTreeSnapshot,
       this.endTreeOfHistoricPrivateDataTreeRootsSnapshot,
       this.endTreeOfHistoricContractTreeRootsSnapshot,
       this.endPublicDataTreeRoot,
+      this.endL1ToL2MessageTreeSnapshot,
+      this.endTreeOfHistoricL1ToL2MessageTreeRootsSnapshot,
       this.getCalldataHash(),
+      this.getL1ToL2MessagesHash(),
     );
+
     const temp = toBigIntBE(sha256(buf));
     // Prime order of BN254 curve
     const p = BigInt('21888242871839275222246405745257275088548364400416034343698204186575808495617');
@@ -264,6 +314,8 @@ export class L2Block {
       this.startTreeOfHistoricPrivateDataTreeRootsSnapshot,
       this.startTreeOfHistoricContractTreeRootsSnapshot,
       this.startPublicDataTreeRoot,
+      this.startL1ToL2MessageTreeSnapshot,
+      this.startTreeOfHistoricL1ToL2MessageTreeRootsSnapshot,
     );
     return sha256(inputValue);
   }
@@ -281,6 +333,8 @@ export class L2Block {
       this.endTreeOfHistoricPrivateDataTreeRootsSnapshot,
       this.endTreeOfHistoricContractTreeRootsSnapshot,
       this.endPublicDataTreeRoot,
+      this.endL1ToL2MessageTreeSnapshot,
+      this.endTreeOfHistoricL1ToL2MessageTreeRootsSnapshot,
     );
     return sha256(inputValue);
   }
@@ -349,6 +403,17 @@ export class L2Block {
     return computeRoot(leafs);
   }
 
+  /**
+   * Compute the hash of all of this blocks l1 to l2 messages,
+   * The hash is also calculated within the contract when the block is submitted
+   * @returns
+   */
+  getL1ToL2MessagesHash() {
+    // Create a long buffer of all of the l1 to l2 messages
+    const l1ToL2Messages = Buffer.concat(this.newL1ToL2Messages.map(message => message.toBuffer()));
+    return sha256(l1ToL2Messages);
+  }
+
   /**
    * Get the ith transaction in an L2 block.
    * @param txIndex - The index of the tx in the block.
@@ -415,6 +480,10 @@ export class L2Block {
         this.startTreeOfHistoricContractTreeRootsSnapshot,
       )}`,
       `startPublicDataTreeRoot: ${this.startPublicDataTreeRoot.toString()}`,
+      `startL1ToL2MessageTreeSnapshot: ${inspectTreeSnapshot(this.startL1ToL2MessageTreeSnapshot)}`,
+      `startTreeOfHistoricL1ToL2MessageTreeRootsSnapshot: ${inspectTreeSnapshot(
+        this.startTreeOfHistoricL1ToL2MessageTreeRootsSnapshot,
+      )}`,
       `endPrivateDataTreeSnapshot: ${inspectTreeSnapshot(this.endPrivateDataTreeSnapshot)}`,
       `endNullifierTreeSnapshot: ${inspectTreeSnapshot(this.endNullifierTreeSnapshot)}`,
       `endContractTreeSnapshot: ${inspectTreeSnapshot(this.endContractTreeSnapshot)}`,
@@ -426,12 +495,17 @@ export class L2Block {
         this.endTreeOfHistoricContractTreeRootsSnapshot,
       )}`,
       `endPublicDataTreeRoot: ${this.endPublicDataTreeRoot.toString()}`,
+      `endL1ToL2MessageTreeSnapshot: ${inspectTreeSnapshot(this.endL1ToL2MessageTreeSnapshot)}`,
+      `endTreeOfHistoricL1ToL2MessageTreeRootsSnapshot: ${inspectTreeSnapshot(
+        this.endTreeOfHistoricL1ToL2MessageTreeRootsSnapshot,
+      )}`,
       `newCommitments: ${inspectFrArray(this.newCommitments)}`,
       `newNullifiers: ${inspectFrArray(this.newNullifiers)}`,
       `newPublicDataWrite: ${inspectPublicDataWriteArray(this.newPublicDataWrites)}`,
       `newContracts: ${inspectFrArray(this.newContracts)}`,
       `newContractData: ${inspectContractDataArray(this.newContractData)}`,
       `newPublicDataWrite: ${inspectPublicDataWriteArray(this.newPublicDataWrites)}`,
+      `newL1ToL2Messages: ${inspectFrArray(this.newL1ToL2Messages)}`,
     ].join('\n');
   }
 }
diff --git a/yarn-project/world-state/src/merkle-tree/merkle_tree_operations_facade.ts b/yarn-project/world-state/src/merkle-tree/merkle_tree_operations_facade.ts
index 918caefae71..047743daa50 100644
--- a/yarn-project/world-state/src/merkle-tree/merkle_tree_operations_facade.ts
+++ b/yarn-project/world-state/src/merkle-tree/merkle_tree_operations_facade.ts
@@ -107,7 +107,7 @@ export class MerkleTreeOperationsFacade implements MerkleTreeOperations {
    * the current roots of the corresponding trees (CONTRACT_TREE, PRIVATE_DATA_TREE).
    * @returns Empty promise.
    */
-  public updateRootsTrees(): Promise<void> {
-    return this.trees.updateRootsTrees(this.includeUncommitted);
+  public updateHistoricRootsTrees(): Promise<void> {
+    return this.trees.updateHistoricRootsTrees(this.includeUncommitted);
   }
 }
diff --git a/yarn-project/world-state/src/synchroniser/server_world_state_synchroniser.test.ts b/yarn-project/world-state/src/synchroniser/server_world_state_synchroniser.test.ts
index bf67b8c8677..19fa68cf645 100644
--- a/yarn-project/world-state/src/synchroniser/server_world_state_synchroniser.test.ts
+++ b/yarn-project/world-state/src/synchroniser/server_world_state_synchroniser.test.ts
@@ -1,5 +1,5 @@
 import { BarretenbergWasm } from '@aztec/barretenberg.js/wasm';
-import { AppendOnlyTreeSnapshot } from '@aztec/circuits.js';
+import { AppendOnlyTreeSnapshot, NUMBER_OF_L1_L2_MESSAGES_PER_ROLLUP } from '@aztec/circuits.js';
 import { fr } from '@aztec/circuits.js/factories';
 import { Fr, sleep } from '@aztec/foundation';
 import { INITIAL_LEAF, Pedersen, SiblingPath } from '@aztec/merkle-tree';
@@ -33,6 +33,10 @@ const getMockContractData = () => {
   return ContractData.random();
 };
 
+const getMockL1ToL2MessagesData = () => {
+  return new Array(NUMBER_OF_L1_L2_MESSAGES_PER_ROLLUP).map(() => Fr.random());
+};
+
 const getMockBlock = (blockNumber: number, newContractsCommitments?: Buffer[]) => {
   const block = L2Block.fromFields({
     number: blockNumber,
@@ -42,17 +46,22 @@ const getMockBlock = (blockNumber: number, newContractsCommitments?: Buffer[]) =
     startTreeOfHistoricPrivateDataTreeRootsSnapshot: getMockTreeSnapshot(),
     startTreeOfHistoricContractTreeRootsSnapshot: getMockTreeSnapshot(),
     startPublicDataTreeRoot: Fr.random(),
+    startL1ToL2MessageTreeSnapshot: getMockTreeSnapshot(),
+    startTreeOfHistoricL1ToL2MessageTreeRootsSnapshot: getMockTreeSnapshot(),
     endPrivateDataTreeSnapshot: getMockTreeSnapshot(),
     endNullifierTreeSnapshot: getMockTreeSnapshot(),
     endContractTreeSnapshot: getMockTreeSnapshot(),
     endTreeOfHistoricPrivateDataTreeRootsSnapshot: getMockTreeSnapshot(),
     endTreeOfHistoricContractTreeRootsSnapshot: getMockTreeSnapshot(),
     endPublicDataTreeRoot: Fr.random(),
+    endL1ToL2MessageTreeSnapshot: getMockTreeSnapshot(),
+    endTreeOfHistoricL1ToL2MessageTreeRootsSnapshot: getMockTreeSnapshot(),
     newCommitments: [Fr.random()],
     newNullifiers: [Fr.random()],
     newContracts: newContractsCommitments?.map(x => Fr.fromBuffer(x)) ?? [Fr.random()],
     newContractData: [getMockContractData()],
     newPublicDataWrites: [PublicDataWrite.random()],
+    newL1ToL2Messages: getMockL1ToL2MessagesData(),
   });
   return block;
 };
@@ -81,7 +90,7 @@ describe('server_world_state_synchroniser', () => {
         SiblingPath.ZERO(32, INITIAL_LEAF, pedersen);
       }; //Promise.resolve();
     }),
-    updateRootsTrees: jest.fn().mockImplementation(() => Promise.resolve()),
+    updateHistoricRootsTrees: jest.fn().mockImplementation(() => Promise.resolve()),
     commit: jest.fn().mockImplementation(() => Promise.resolve()),
     rollback: jest.fn().mockImplementation(() => Promise.resolve()),
   } as any;
@@ -231,7 +240,7 @@ describe('server_world_state_synchroniser', () => {
 
   it('updates the contract tree', async () => {
     merkleTreeDb.appendLeaves.mockReset();
-    merkleTreeDb.updateRootsTrees.mockReset();
+    merkleTreeDb.updateHistoricRootsTrees.mockReset();
     const server = createSynchroniser(merkleTreeDb, rollupSource);
     const totalBlocks = LATEST_BLOCK_NUMBER + 1;
     nextBlocks = Array(totalBlocks)
@@ -242,7 +251,7 @@ describe('server_world_state_synchroniser', () => {
     // there are 3 data trees updated
     expect(merkleTreeDb.appendLeaves).toHaveBeenCalledTimes(totalBlocks * 3);
     // and 2 root trees
-    expect(merkleTreeDb.updateRootsTrees).toHaveBeenCalledTimes(totalBlocks);
+    expect(merkleTreeDb.updateHistoricRootsTrees).toHaveBeenCalledTimes(totalBlocks);
     // there should be a call to append to the contract tree for each block
     for (let i = 0; i < totalBlocks; i++) {
       expect(
diff --git a/yarn-project/world-state/src/synchroniser/server_world_state_synchroniser.ts b/yarn-project/world-state/src/synchroniser/server_world_state_synchroniser.ts
index 570f1c08459..05018273f43 100644
--- a/yarn-project/world-state/src/synchroniser/server_world_state_synchroniser.ts
+++ b/yarn-project/world-state/src/synchroniser/server_world_state_synchroniser.ts
@@ -167,7 +167,7 @@ export class ServerWorldStateSynchroniser implements WorldStateSynchroniser {
         await this.merkleTreeDb.updateLeaf(MerkleTreeId.PUBLIC_DATA_TREE, newValue.toBuffer(), leafIndex.value);
       }
 
-      await this.merkleTreeDb.updateRootsTrees(true);
+      await this.merkleTreeDb.updateHistoricRootsTrees(true);
       await this.merkleTreeDb.commit();
     }
     this.currentL2BlockNum = l2Block.number;
diff --git a/yarn-project/world-state/src/world-state-db/index.ts b/yarn-project/world-state/src/world-state-db/index.ts
index 469b6a219a3..36944827a88 100644
--- a/yarn-project/world-state/src/world-state-db/index.ts
+++ b/yarn-project/world-state/src/world-state-db/index.ts
@@ -13,6 +13,8 @@ export enum MerkleTreeId {
   PRIVATE_DATA_TREE = 3,
   PRIVATE_DATA_TREE_ROOTS_TREE = 4,
   PUBLIC_DATA_TREE = 5,
+  L1_TO_L2_MESSAGES_TREE = 6,
+  L1_TO_L2_MESSAGES_ROOTS_TREE = 7,
 }
 
 /**
@@ -152,7 +154,7 @@ export interface MerkleTreeOperations {
    * Inserts into the roots trees (CONTRACT_TREE_ROOTS_TREE, PRIVATE_DATA_TREE_ROOTS_TREE)
    * the current roots of the corresponding trees (CONTRACT_TREE, PRIVATE_DATA_TREE).
    */
-  updateRootsTrees(): Promise<void>;
+  updateHistoricRootsTrees(): Promise<void>;
 }
 
 /**
diff --git a/yarn-project/world-state/src/world-state-db/merkle_trees.ts b/yarn-project/world-state/src/world-state-db/merkle_trees.ts
index d79f60da7b5..036ed0c5df9 100644
--- a/yarn-project/world-state/src/world-state-db/merkle_trees.ts
+++ b/yarn-project/world-state/src/world-state-db/merkle_trees.ts
@@ -2,6 +2,8 @@ import { PrimitivesWasm } from '@aztec/barretenberg.js/wasm';
 import {
   CONTRACT_TREE_HEIGHT,
   CONTRACT_TREE_ROOTS_TREE_HEIGHT,
+  L1_TO_L2_MESSAGES_ROOTS_TREE_HEIGHT,
+  L1_TO_L2_MESSAGES_TREE_HEIGHT,
   NULLIFIER_TREE_HEIGHT,
   PRIVATE_DATA_TREE_HEIGHT,
   PRIVATE_DATA_TREE_ROOTS_TREE_HEIGHT,
@@ -92,7 +94,20 @@ export class MerkleTrees implements MerkleTreeDb {
       `${MerkleTreeId[MerkleTreeId.PUBLIC_DATA_TREE]}`,
       PUBLIC_DATA_TREE_HEIGHT,
     );
-
+    const l1Tol2MessagesTree: AppendOnlyTree = await newTree(
+      StandardTree,
+      this.db,
+      hasher,
+      `${MerkleTreeId[MerkleTreeId.L1_TO_L2_MESSAGES_TREE]}`,
+      L1_TO_L2_MESSAGES_TREE_HEIGHT,
+    );
+    const l1Tol2MessagesRootsTree: AppendOnlyTree = await newTree(
+      StandardTree,
+      this.db,
+      hasher,
+      `${MerkleTreeId[MerkleTreeId.L1_TO_L2_MESSAGES_ROOTS_TREE]}`,
+      L1_TO_L2_MESSAGES_ROOTS_TREE_HEIGHT,
+    );
     this.trees = [
       contractTree,
       contractTreeRootsTree,
@@ -100,11 +115,13 @@ export class MerkleTrees implements MerkleTreeDb {
       privateDataTree,
       privateDataTreeRootsTree,
       publicDataTree,
+      l1Tol2MessagesTree,
+      l1Tol2MessagesRootsTree,
     ];
 
     this.jobQueue.start();
 
-    await this.updateRootsTrees(true);
+    await this.updateHistoricRootsTrees(true);
   }
 
   /**
@@ -147,10 +164,11 @@ export class MerkleTrees implements MerkleTreeDb {
    * the current roots of the corresponding trees (CONTRACT_TREE, PRIVATE_DATA_TREE).
    * @param includeUncommitted - Indicates whether to include uncommitted data.
    */
-  public async updateRootsTrees(includeUncommitted: boolean) {
+  public async updateHistoricRootsTrees(includeUncommitted: boolean) {
     for (const [newTree, rootTree] of [
       [MerkleTreeId.PRIVATE_DATA_TREE, MerkleTreeId.PRIVATE_DATA_TREE_ROOTS_TREE],
       [MerkleTreeId.CONTRACT_TREE, MerkleTreeId.CONTRACT_TREE_ROOTS_TREE],
+      [MerkleTreeId.L1_TO_L2_MESSAGES_TREE, MerkleTreeId.L1_TO_L2_MESSAGES_ROOTS_TREE],
     ] as const) {
       const newTreeInfo = await this.getTreeInfo(newTree, includeUncommitted);
       await this.appendLeaves(rootTree, [newTreeInfo.root]);