diff --git a/artifacts/program_methods/amm.bin b/artifacts/program_methods/amm.bin
index 1c7fb30c..f71d77d0 100644
Binary files a/artifacts/program_methods/amm.bin and b/artifacts/program_methods/amm.bin differ
diff --git a/artifacts/program_methods/associated_token_account.bin b/artifacts/program_methods/associated_token_account.bin
index 4e6695c4..71e8e943 100644
Binary files a/artifacts/program_methods/associated_token_account.bin and b/artifacts/program_methods/associated_token_account.bin differ
diff --git a/artifacts/program_methods/authenticated_transfer.bin b/artifacts/program_methods/authenticated_transfer.bin
index dcd1b434..aa64dac0 100644
Binary files a/artifacts/program_methods/authenticated_transfer.bin and b/artifacts/program_methods/authenticated_transfer.bin differ
diff --git a/artifacts/program_methods/clock.bin b/artifacts/program_methods/clock.bin
index 677c569d..60556fdc 100644
Binary files a/artifacts/program_methods/clock.bin and b/artifacts/program_methods/clock.bin differ
diff --git a/artifacts/program_methods/pinata.bin b/artifacts/program_methods/pinata.bin
index 6fccf4d6..c3d70477 100644
Binary files a/artifacts/program_methods/pinata.bin and b/artifacts/program_methods/pinata.bin differ
diff --git a/artifacts/program_methods/pinata_token.bin b/artifacts/program_methods/pinata_token.bin
index b6d97937..22dbc5e8 100644
Binary files a/artifacts/program_methods/pinata_token.bin and b/artifacts/program_methods/pinata_token.bin differ
diff --git a/artifacts/program_methods/privacy_preserving_circuit.bin b/artifacts/program_methods/privacy_preserving_circuit.bin
index e846c2f9..b2c09b79 100644
Binary files a/artifacts/program_methods/privacy_preserving_circuit.bin and b/artifacts/program_methods/privacy_preserving_circuit.bin differ
diff --git a/artifacts/program_methods/token.bin b/artifacts/program_methods/token.bin
index d445f5bf..e24d7a1f 100644
Binary files a/artifacts/program_methods/token.bin and b/artifacts/program_methods/token.bin differ
diff --git a/artifacts/test_program_methods/burner.bin b/artifacts/test_program_methods/burner.bin
index b4b961c4..a740bdb8 100644
Binary files a/artifacts/test_program_methods/burner.bin and b/artifacts/test_program_methods/burner.bin differ
diff --git a/artifacts/test_program_methods/chain_caller.bin b/artifacts/test_program_methods/chain_caller.bin
index b4a2eef2..112ca113 100644
Binary files a/artifacts/test_program_methods/chain_caller.bin and b/artifacts/test_program_methods/chain_caller.bin differ
diff --git a/artifacts/test_program_methods/changer_claimer.bin b/artifacts/test_program_methods/changer_claimer.bin
index fb94bf44..a130510b 100644
Binary files a/artifacts/test_program_methods/changer_claimer.bin and b/artifacts/test_program_methods/changer_claimer.bin differ
diff --git a/artifacts/test_program_methods/claimer.bin b/artifacts/test_program_methods/claimer.bin
index 00bc3bc0..41a5cb3b 100644
Binary files a/artifacts/test_program_methods/claimer.bin and b/artifacts/test_program_methods/claimer.bin differ
diff --git a/artifacts/test_program_methods/clock_chain_caller.bin b/artifacts/test_program_methods/clock_chain_caller.bin
index acb95f85..57cbb38d 100644
Binary files a/artifacts/test_program_methods/clock_chain_caller.bin and b/artifacts/test_program_methods/clock_chain_caller.bin differ
diff --git a/artifacts/test_program_methods/data_changer.bin b/artifacts/test_program_methods/data_changer.bin
index 73fe01a7..3dddebe1 100644
Binary files a/artifacts/test_program_methods/data_changer.bin and b/artifacts/test_program_methods/data_changer.bin differ
diff --git a/artifacts/test_program_methods/extra_output.bin b/artifacts/test_program_methods/extra_output.bin
index 792c1225..1d682ec3 100644
Binary files a/artifacts/test_program_methods/extra_output.bin and b/artifacts/test_program_methods/extra_output.bin differ
diff --git a/artifacts/test_program_methods/malicious_authorization_changer.bin b/artifacts/test_program_methods/malicious_authorization_changer.bin
index e8bfb1ac..c68496ab 100644
Binary files a/artifacts/test_program_methods/malicious_authorization_changer.bin and b/artifacts/test_program_methods/malicious_authorization_changer.bin differ
diff --git a/artifacts/test_program_methods/minter.bin b/artifacts/test_program_methods/minter.bin
index f0d9674e..ffd29461 100644
Binary files a/artifacts/test_program_methods/minter.bin and b/artifacts/test_program_methods/minter.bin differ
diff --git a/artifacts/test_program_methods/missing_output.bin b/artifacts/test_program_methods/missing_output.bin
index 8cd04a44..a2bbecd8 100644
Binary files a/artifacts/test_program_methods/missing_output.bin and b/artifacts/test_program_methods/missing_output.bin differ
diff --git a/artifacts/test_program_methods/modified_transfer.bin b/artifacts/test_program_methods/modified_transfer.bin
index 64c53aa2..b44b1233 100644
Binary files a/artifacts/test_program_methods/modified_transfer.bin and b/artifacts/test_program_methods/modified_transfer.bin differ
diff --git a/artifacts/test_program_methods/nonce_changer.bin b/artifacts/test_program_methods/nonce_changer.bin
index 6a2b96b0..e006fc75 100644
Binary files a/artifacts/test_program_methods/nonce_changer.bin and b/artifacts/test_program_methods/nonce_changer.bin differ
diff --git a/artifacts/test_program_methods/noop.bin b/artifacts/test_program_methods/noop.bin
index d6e3e89e..da811f60 100644
Binary files a/artifacts/test_program_methods/noop.bin and b/artifacts/test_program_methods/noop.bin differ
diff --git a/artifacts/test_program_methods/program_owner_changer.bin b/artifacts/test_program_methods/program_owner_changer.bin
index 6c5bcf06..3963873e 100644
Binary files a/artifacts/test_program_methods/program_owner_changer.bin and b/artifacts/test_program_methods/program_owner_changer.bin differ
diff --git a/artifacts/test_program_methods/simple_balance_transfer.bin b/artifacts/test_program_methods/simple_balance_transfer.bin
index 2813e34e..08db47f0 100644
Binary files a/artifacts/test_program_methods/simple_balance_transfer.bin and b/artifacts/test_program_methods/simple_balance_transfer.bin differ
diff --git a/artifacts/test_program_methods/validity_window.bin b/artifacts/test_program_methods/validity_window.bin
index 0ee7dfeb..ceb5ae74 100644
Binary files a/artifacts/test_program_methods/validity_window.bin and b/artifacts/test_program_methods/validity_window.bin differ
diff --git a/artifacts/test_program_methods/validity_window_chain_caller.bin b/artifacts/test_program_methods/validity_window_chain_caller.bin
index f574f82b..a7661f03 100644
Binary files a/artifacts/test_program_methods/validity_window_chain_caller.bin and b/artifacts/test_program_methods/validity_window_chain_caller.bin differ
diff --git a/common/src/transaction.rs b/common/src/transaction.rs
index 8dbd6365..c6153271 100644
--- a/common/src/transaction.rs
+++ b/common/src/transaction.rs
@@ -1,6 +1,6 @@
 use borsh::{BorshDeserialize, BorshSerialize};
 use log::warn;
-use nssa::{AccountId, V03State};
+use nssa::{AccountId, V03State, ValidatedStateDiff};
 use nssa_core::{BlockId, Timestamp};
 use serde::{Deserialize, Serialize};
 
@@ -83,21 +83,53 @@ impl NSSATransaction {
         }
     }
 
+    /// Validates the transaction against the current state and returns the resulting diff
+    /// without applying it. Rejects transactions that modify clock system accounts.
+    pub fn validate_on_state(
+        &self,
+        state: &V03State,
+        block_id: BlockId,
+        timestamp: Timestamp,
+    ) -> Result<ValidatedStateDiff, nssa::error::NssaError> {
+        let diff = match self {
+            Self::Public(tx) => {
+                ValidatedStateDiff::from_public_transaction(tx, state, block_id, timestamp)
+            }
+            Self::PrivacyPreserving(tx) => ValidatedStateDiff::from_privacy_preserving_transaction(
+                tx, state, block_id, timestamp,
+            ),
+            Self::ProgramDeployment(tx) => {
+                ValidatedStateDiff::from_program_deployment_transaction(tx, state)
+            }
+        }?;
+
+        let public_diff = diff.public_diff();
+        let touches_clock = nssa::CLOCK_PROGRAM_ACCOUNT_IDS.iter().any(|id| {
+            public_diff
+                .get(id)
+                .is_some_and(|post| *post != state.get_account_by_id(*id))
+        });
+        if touches_clock {
+            return Err(nssa::error::NssaError::InvalidInput(
+                "Transaction modifies system clock accounts".into(),
+            ));
+        }
+
+        Ok(diff)
+    }
+
+    /// Validates the transaction against the current state, rejects modifications to clock
+    /// system accounts, and applies the resulting diff to the state.
     pub fn execute_check_on_state(
         self,
         state: &mut V03State,
         block_id: BlockId,
         timestamp: Timestamp,
     ) -> Result<Self, nssa::error::NssaError> {
-        match &self {
-            Self::Public(tx) => state.transition_from_public_transaction(tx, block_id, timestamp),
-            Self::PrivacyPreserving(tx) => {
-                state.transition_from_privacy_preserving_transaction(tx, block_id, timestamp)
-            }
-            Self::ProgramDeployment(tx) => state.transition_from_program_deployment_transaction(tx),
-        }
-        .inspect_err(|err| warn!("Error at transition {err:#?}"))?;
-
+        let diff = self
+            .validate_on_state(state, block_id, timestamp)
+            .inspect_err(|err| warn!("Error at transition {err:#?}"))?;
+        state.apply_state_diff(diff);
         Ok(self)
     }
 }
diff --git a/indexer/core/src/block_store.rs b/indexer/core/src/block_store.rs
index bd1992f7..73636790 100644
--- a/indexer/core/src/block_store.rs
+++ b/indexer/core/src/block_store.rs
@@ -122,7 +122,18 @@ impl IndexerStore {
         {
             let mut state_guard = self.current_state.write().await;
 
-            for transaction in &block.body.transactions {
+            let (clock_tx, user_txs) = block
+                .body
+                .transactions
+                .split_last()
+                .ok_or_else(|| anyhow::anyhow!("Block has no transactions"))?;
+
+            anyhow::ensure!(
+                *clock_tx == NSSATransaction::clock_invocation(block.header.timestamp),
+                "Last transaction in block must be the clock invocation for the block timestamp"
+            );
+
+            for transaction in user_txs {
                 transaction
                     .clone()
                     .transaction_stateless_check()?
@@ -132,6 +143,16 @@ impl IndexerStore {
                         block.header.timestamp,
                     )?;
             }
+
+            // Apply the clock invocation directly (it is expected to modify clock accounts).
+            let NSSATransaction::Public(clock_public_tx) = clock_tx else {
+                anyhow::bail!("Clock invocation must be a public transaction");
+            };
+            state_guard.transition_from_public_transaction(
+                clock_public_tx,
+                block.header.block_id,
+                block.header.timestamp,
+            )?;
         }
 
         // ToDo: Currently we are fetching only finalized blocks
diff --git a/programs/clock/core/Cargo.toml b/programs/clock/core/Cargo.toml
new file mode 100644
index 00000000..28acdb48
--- /dev/null
+++ b/programs/clock/core/Cargo.toml
@@ -0,0 +1,11 @@
+[package]
+name = "clock_core"
+version = "0.1.0"
+edition = "2024"
+license = { workspace = true }
+
+[lints]
+workspace = true
+
+[dependencies]
+nssa_core.workspace = true
diff --git a/programs/clock/core/src/lib.rs b/programs/clock/core/src/lib.rs
new file mode 100644
index 00000000..33a08c50
--- /dev/null
+++ b/programs/clock/core/src/lib.rs
@@ -0,0 +1,49 @@
+//! Core data structures and constants for the Clock Program.
+
+use nssa_core::{Timestamp, account::AccountId};
+
+/// The instruction type for the Clock Program. The sequencer passes the current block timestamp.
+pub type Instruction = Timestamp;
+
+pub const CLOCK_01_PROGRAM_ACCOUNT_ID: AccountId =
+    AccountId::new(*b"/LEZ/ClockProgramAccount/0000001");
+
+pub const CLOCK_10_PROGRAM_ACCOUNT_ID: AccountId =
+    AccountId::new(*b"/LEZ/ClockProgramAccount/0000010");
+
+pub const CLOCK_50_PROGRAM_ACCOUNT_ID: AccountId =
+    AccountId::new(*b"/LEZ/ClockProgramAccount/0000050");
+
+/// All clock program account ID int the order expected by the clock program
+pub const CLOCK_PROGRAM_ACCOUNT_IDS: [AccountId; 3] = [
+    CLOCK_01_PROGRAM_ACCOUNT_ID,
+    CLOCK_10_PROGRAM_ACCOUNT_ID,
+    CLOCK_50_PROGRAM_ACCOUNT_ID,
+];
+
+/// The data stored in a clock account: `[block_id: u64 LE | timestamp: u64 LE]`.
+#[derive(Debug, Clone, Copy, PartialEq, Eq)]
+pub struct ClockAccountData {
+    pub block_id: u64,
+    pub timestamp: Timestamp,
+}
+
+impl ClockAccountData {
+    #[must_use]
+    pub fn to_bytes(self) -> [u8; 16] {
+        let mut data = [0_u8; 16];
+        data[..8].copy_from_slice(&self.block_id.to_le_bytes());
+        data[8..].copy_from_slice(&self.timestamp.to_le_bytes());
+        data
+    }
+
+    #[must_use]
+    pub fn from_bytes(bytes: &[u8; 16]) -> Self {
+        let block_id = u64::from_le_bytes(bytes[..8].try_into().unwrap());
+        let timestamp = u64::from_le_bytes(bytes[8..].try_into().unwrap());
+        Self {
+            block_id,
+            timestamp,
+        }
+    }
+}
diff --git a/sequencer/core/src/lib.rs b/sequencer/core/src/lib.rs
index be4906ee..9d4c71c8 100644
--- a/sequencer/core/src/lib.rs
+++ b/sequencer/core/src/lib.rs
@@ -15,8 +15,7 @@ use logos_blockchain_key_management_system_service::keys::{ED25519_SECRET_KEY_SI
 use mempool::{MemPool, MemPoolHandle};
 #[cfg(feature = "mock")]
 pub use mock::SequencerCoreWithMockClients;
-use nssa::{V03State, ValidatedStateDiff};
-use nssa_core::{BlockId, Timestamp};
+use nssa::V03State;
 pub use storage::error::DbError;
 use testnet_initial_state::initial_state;
 
@@ -164,28 +163,6 @@ impl<BC: BlockSettlementClientTrait, IC: IndexerClientTrait> SequencerCore<BC, I
         (sequencer_core, mempool_handle)
     }
 
-    fn execute_check_transaction_on_state(
-        &mut self,
-        tx: NSSATransaction,
-        block_id: BlockId,
-        timestamp: Timestamp,
-    ) -> Result<NSSATransaction, nssa::error::NssaError> {
-        match &tx {
-            NSSATransaction::Public(tx) => self
-                .state
-                .transition_from_public_transaction(tx, block_id, timestamp),
-            NSSATransaction::PrivacyPreserving(tx) => self
-                .state
-                .transition_from_privacy_preserving_transaction(tx, block_id, timestamp),
-            NSSATransaction::ProgramDeployment(tx) => self
-                .state
-                .transition_from_program_deployment_transaction(tx),
-        }
-        .inspect_err(|err| warn!("Error at transition {err:#?}"))?;
-
-        Ok(tx)
-    }
-
     pub async fn produce_new_block(&mut self) -> Result<u64> {
         let (tx, _msg_id) = self
             .produce_new_block_with_mempool_transactions()
@@ -204,30 +181,6 @@ impl<BC: BlockSettlementClientTrait, IC: IndexerClientTrait> SequencerCore<BC, I
         Ok(self.chain_height)
     }
 
-    fn validate_transaction_and_produce_state_diff(
-        &self,
-        transaction: &NSSATransaction,
-        block_id: BlockId,
-        timestamp: Timestamp,
-    ) -> Result<ValidatedStateDiff, nssa::error::NssaError> {
-        match transaction {
-            NSSATransaction::Public(tx) => {
-                ValidatedStateDiff::from_public_transaction(tx, &self.state, block_id, timestamp)
-            }
-            NSSATransaction::PrivacyPreserving(tx) => {
-                ValidatedStateDiff::from_privacy_preserving_transaction(
-                    tx,
-                    &self.state,
-                    block_id,
-                    timestamp,
-                )
-            }
-            NSSATransaction::ProgramDeployment(tx) => {
-                ValidatedStateDiff::from_program_deployment_transaction(tx, &self.state)
-            }
-        }
-    }
-
     /// Produces new block from transactions in mempool and packs it into a `SignedMantleTx`.
     pub fn produce_new_block_with_mempool_transactions(
         &mut self,
@@ -249,33 +202,15 @@ impl<BC: BlockSettlementClientTrait, IC: IndexerClientTrait> SequencerCore<BC, I
         let new_block_timestamp = u64::try_from(chrono::Utc::now().timestamp_millis())
             .expect("Timestamp must be positive");
 
-        // Note: the clock accounts are only modified by the clock program, which is invoked
-        // exclusively by the sequencer as the mandatory last transaction in each block. All user
-        // transactions are processed before that invocation, so this snapshot is always current
-        // and constant for all transactions in the block
-        let clock_accounts_pre =
-            nssa::CLOCK_PROGRAM_ACCOUNT_IDS.map(|id| (id, self.state.get_account_by_id(id)));
-
         while let Some(tx) = self.mempool.pop() {
             let tx_hash = tx.hash();
 
-            let validated_diff = match self.validate_transaction_and_produce_state_diff(
-                &tx,
+            let validated_diff = match tx.validate_on_state(
+                &self.state,
                 new_block_height,
                 new_block_timestamp,
             ) {
-                Ok(diff) => {
-                    let touches_system = clock_accounts_pre.iter().any(|(id, pre)| {
-                        diff.public_diff().get(id).is_some_and(|post| post != pre)
-                    });
-                    if touches_system {
-                        warn!(
-                            "Dropping transaction from mempool: user transactions may not modify the system clock account"
-                        );
-                        continue;
-                    }
-                    diff
-                }
+                Ok(diff) => diff,
                 Err(err) => {
                     error!(
                         "Transaction with hash {tx_hash} failed execution check with error: {err:#?}, skipping it",
@@ -319,13 +254,17 @@ impl<BC: BlockSettlementClientTrait, IC: IndexerClientTrait> SequencerCore<BC, I
         }
 
         // Append the Block Context Program invocation as the mandatory last transaction.
-        let clock_nssa_tx = self
-            .execute_check_transaction_on_state(
-                NSSATransaction::clock_invocation(new_block_timestamp),
+        let clock_nssa_tx = NSSATransaction::clock_invocation(new_block_timestamp);
+        self.state
+            .transition_from_public_transaction(
+                match &clock_nssa_tx {
+                    NSSATransaction::Public(tx) => tx,
+                    _ => unreachable!("clock_invocation always returns Public"),
+                },
                 new_block_height,
                 new_block_timestamp,
             )
-            .context("Clock transaction failed \u{2014} aborting block production")?;
+            .context("Clock transaction failed. Aborting block production.")?;
         valid_transactions.push(clock_nssa_tx);
 
         let hashable_data = HashableBlockData {
@@ -454,8 +393,6 @@ mod tests {
     use common::{test_utils::sequencer_sign_key_for_testing, transaction::NSSATransaction};
     use logos_blockchain_core::mantle::ops::channel::ChannelId;
     use mempool::MemPoolHandle;
-    
-    
     use testnet_initial_state::{initial_accounts, initial_pub_accounts_private_keys};
 
     use crate::{
@@ -582,7 +519,7 @@ mod tests {
         let tx = tx.transaction_stateless_check().unwrap();
 
         // Signature is not from sender. Execution fails
-        let result = sequencer.execute_check_transaction_on_state(tx, 0, 0);
+        let result = tx.execute_check_on_state(&mut sequencer.state, 0, 0);
 
         assert!(matches!(
             result,
@@ -608,7 +545,9 @@ mod tests {
         // Passed pre-check
         assert!(result.is_ok());
 
-        let result = sequencer.execute_check_transaction_on_state(result.unwrap(), 0, 0);
+        let result = result
+            .unwrap()
+            .execute_check_on_state(&mut sequencer.state, 0, 0);
         let is_failed_at_balance_mismatch = matches!(
             result.err().unwrap(),
             nssa::error::NssaError::ProgramExecutionFailed(_)
@@ -630,8 +569,7 @@ mod tests {
             acc1, 0, acc2, 100, &sign_key1,
         );
 
-        sequencer
-            .execute_check_transaction_on_state(tx, 0, 0)
+        tx.execute_check_on_state(&mut sequencer.state, 0, 0)
             .unwrap();
 
         let bal_from = sequencer.state.get_account_by_id(acc1).balance;