diff --git a/integration_tests/tests/cross_zone_state_machine.rs b/integration_tests/tests/cross_zone_state_machine.rs
index 30725c680..c3ca941ab 100644
--- a/integration_tests/tests/cross_zone_state_machine.rs
+++ b/integration_tests/tests/cross_zone_state_machine.rs
@@ -590,7 +590,7 @@ fn a_second_emit_at_the_same_slot_is_rejected() {
     let first = lock_tx(&holder_key, holder_id, zone_b, ordinal, 0);
     let diff = ValidatedStateDiff::from_public_transaction(&first, &state, 1, 0)
         .expect("the first lock executes");
-    state.apply_state_diff(diff);
+    drop(state.apply_state_diff(diff));
 
     // Same slot, fresh nonce, so the only thing that can reject it is the slot
     // already holding a record. Matched on the guest's own message rather than
@@ -646,7 +646,7 @@ fn two_emitters_share_an_ordinal_without_colliding() {
     let lock = lock_tx(&holder_key, holder_id, zone_b, ordinal, 0);
     let diff = ValidatedStateDiff::from_public_transaction(&lock, &state, 1, 0)
         .expect("the lock executes");
-    state.apply_state_diff(diff);
+    drop(state.apply_state_diff(diff));
 
     let send = send_tx(
         vec![sender_config_account_id(sender_id), send_slot],
@@ -936,7 +936,7 @@ fn the_bridge_pins_are_written_once_and_replayable() {
         0,
     )
     .expect("the first init claims the config PDA");
-    state.apply_state_diff(diff);
+    drop(state.apply_state_diff(diff));
     assert_eq!(
         bridge_lock_core::read_config(&state.get_account_by_id(config_id).data.into_inner()),
         Some((outbox_id, wrapped_token_id)),
@@ -1042,7 +1042,7 @@ fn the_outbox_pin_is_written_once_and_replayable() {
     let first = init(outbox_id);
     let diff = ValidatedStateDiff::from_public_transaction(&first, &state, 1, 0)
         .expect("the first init claims the config PDA");
-    state.apply_state_diff(diff);
+    drop(state.apply_state_diff(diff));
     assert_eq!(
         read_outbox(&state.get_account_by_id(config_id).data.into_inner()),
         Some(outbox_id),
@@ -1180,7 +1180,7 @@ fn the_token_authority_path_holds() {
         0,
     )
     .expect("the configured authority changes sources");
-    state.apply_state_diff(diff);
+    drop(state.apply_state_diff(diff));
     let cfg = wrapped_token_core::WrappedTokenConfig::from_bytes(
         &state.get_account_by_id(config_id).data.into_inner(),
     )
@@ -1200,7 +1200,7 @@ fn the_token_authority_path_holds() {
         0,
     )
     .expect("the authority acts again");
-    state.apply_state_diff(second);
+    drop(state.apply_state_diff(second));
     let updated_cfg = wrapped_token_core::WrappedTokenConfig::from_bytes(
         &state.get_account_by_id(config_id).data.into_inner(),
     )
@@ -1220,7 +1220,7 @@ fn the_token_authority_path_holds() {
     let renounced =
         ValidatedStateDiff::from_public_transaction(&renounce(authority, &key, 2), &state, 3, 0)
             .expect("the authority renounces itself");
-    state.apply_state_diff(renounced);
+    drop(state.apply_state_diff(renounced));
     let renounced_cfg = wrapped_token_core::WrappedTokenConfig::from_bytes(
         &state.get_account_by_id(config_id).data.into_inner(),
     )
@@ -1431,7 +1431,7 @@ fn the_receiver_authority_path_holds() {
     let diff =
         ValidatedStateDiff::from_public_transaction(&update(authority, &key, 0), &state, 1, 0)
             .expect("the configured authority changes sources");
-    state.apply_state_diff(diff);
+    drop(state.apply_state_diff(diff));
     let cfg = ping_core::ReceiverConfig::from_bytes(
         &state.get_account_by_id(config_id).data.into_inner(),
     )
@@ -1442,7 +1442,7 @@ fn the_receiver_authority_path_holds() {
     let renounce_diff =
         ValidatedStateDiff::from_public_transaction(&renounce(authority, &key, 1), &state, 2, 0)
             .expect("the authority renounces itself");
-    state.apply_state_diff(renounce_diff);
+    drop(state.apply_state_diff(renounce_diff));
     let renounced_cfg = ping_core::ReceiverConfig::from_bytes(
         &state.get_account_by_id(config_id).data.into_inner(),
     )
@@ -1555,7 +1555,7 @@ fn the_governance_path_holds() {
         0,
     )
     .expect("the governance path changes sources");
-    state.apply_state_diff(first);
+    drop(state.apply_state_diff(first));
 
     let cfg = wrapped_token_core::WrappedTokenConfig::from_bytes(
         &state.get_account_by_id(config_id).data.into_inner(),
@@ -1570,7 +1570,7 @@ fn the_governance_path_holds() {
 
     let second = ValidatedStateDiff::from_public_transaction(&update(vec![]), &state, 2, 0)
         .expect("the governance path acts again");
-    state.apply_state_diff(second);
+    drop(state.apply_state_diff(second));
     let cleared_cfg = wrapped_token_core::WrappedTokenConfig::from_bytes(
         &state.get_account_by_id(config_id).data.into_inner(),
     )
@@ -1583,7 +1583,7 @@ fn the_governance_path_holds() {
 
     let renounced = ValidatedStateDiff::from_public_transaction(&renounce(), &state, 3, 0)
         .expect("the governance path renounces");
-    state.apply_state_diff(renounced);
+    drop(state.apply_state_diff(renounced));
     let renounced_cfg = wrapped_token_core::WrappedTokenConfig::from_bytes(
         &state.get_account_by_id(config_id).data.into_inner(),
     )
@@ -1723,7 +1723,7 @@ fn the_receiver_governance_path_holds() {
 
     let diff = ValidatedStateDiff::from_public_transaction(&tx, &state, 1, 0)
         .expect("the receiver governance path changes sources");
-    state.apply_state_diff(diff);
+    drop(state.apply_state_diff(diff));
     let cfg = ping_core::ReceiverConfig::from_bytes(
         &state.get_account_by_id(config_id).data.into_inner(),
     )
@@ -1767,7 +1767,7 @@ fn a_shared_authority_survives_the_first_claim() {
     );
     let first = ValidatedStateDiff::from_public_transaction(&token_update, &state, 1, 0)
         .expect("the token claims the shared authority");
-    state.apply_state_diff(first);
+    drop(state.apply_state_diff(first));
     assert_eq!(
         state.get_account_by_id(authority).program_owner,
         wrapped_token_id.into(),
@@ -1786,7 +1786,7 @@ fn a_shared_authority_survives_the_first_claim() {
     );
     let second = ValidatedStateDiff::from_public_transaction(&receiver_update, &state, 2, 0)
         .expect("the other target still acts on the token-owned authority");
-    state.apply_state_diff(second);
+    drop(state.apply_state_diff(second));
     let receiver_cfg = ping_core::ReceiverConfig::from_bytes(
         &state
             .get_account_by_id(receiver_config_id)
@@ -1814,7 +1814,7 @@ fn a_shared_authority_survives_the_first_claim() {
     );
     let third = ValidatedStateDiff::from_public_transaction(&receiver_renounce, &state, 3, 0)
         .expect("the other target renounces on the token-owned authority");
-    state.apply_state_diff(third);
+    drop(state.apply_state_diff(third));
     let renounced_cfg = ping_core::ReceiverConfig::from_bytes(
         &state
             .get_account_by_id(receiver_config_id)
diff --git a/lee/state_machine/core/src/program/mod.rs b/lee/state_machine/core/src/program/mod.rs
index 1ff881bef..36ab94276 100644
--- a/lee/state_machine/core/src/program/mod.rs
+++ b/lee/state_machine/core/src/program/mod.rs
@@ -468,6 +468,14 @@ impl<T> From<std::ops::RangeFull> for ValidityWindow<T> {
 #[error("Invalid window")]
 pub struct InvalidWindow;
 
+#[derive(Serialize, Deserialize, Clone, BorshSerialize, BorshDeserialize)]
+#[cfg_attr(any(feature = "host", test), derive(Debug, PartialEq, Eq))]
+pub struct ProgramEvent {
+    pub selector: [u8; 8],
+    /// The arbitrary event-data emitted in the program output.
+    pub data: Vec<u8>,
+}
+
 #[derive(Serialize, Deserialize, Clone)]
 #[cfg_attr(any(feature = "host", test), derive(Debug, PartialEq, Eq))]
 #[must_use = "ProgramOutput does nothing unless written"]
@@ -491,7 +499,7 @@ pub struct ProgramOutput {
     pub timestamp_validity_window: TimestampValidityWindow,
     /// A vector of event data. Dropped for private transaction for function
     /// privacy.
-    pub events: Vec<Vec<u8>>,
+    pub events: Vec<ProgramEvent>,
 }
 
 impl ProgramOutput {
@@ -524,7 +532,7 @@ impl ProgramOutput {
         self
     }
 
-    pub fn with_events(mut self, events: Vec<Vec<u8>>) -> Self {
+    pub fn with_events(mut self, events: Vec<ProgramEvent>) -> Self {
         self.events = events;
         self
     }
@@ -582,11 +590,10 @@ impl ProgramOutput {
 /// A struct holding an event-output of a program.
 #[cfg(feature = "host")]
 #[derive(Debug, Clone, PartialEq, Eq, BorshSerialize, BorshDeserialize)]
-pub struct Event {
+pub struct TransactionEvent {
     /// Which program emitted the event.
     pub program_id: ProgramId,
-    /// The arbitrary event-data emitted in the program output.
-    pub data: Vec<u8>,
+    pub event: ProgramEvent,
 }
 
 /// Representation of a number as `lo + hi * 2^128`.
diff --git a/lee/state_machine/src/state/mod.rs b/lee/state_machine/src/state/mod.rs
index 58beecc55..082c8da2a 100644
--- a/lee/state_machine/src/state/mod.rs
+++ b/lee/state_machine/src/state/mod.rs
@@ -5,7 +5,7 @@ use lee_core::{
     BlockId, Commitment, CommitmentSetDigest, DUMMY_COMMITMENT, MembershipProof, Nullifier,
     Timestamp,
     account::{Account, AccountId, Data},
-    program::{Event, PROGRAM_STORAGE_OWNER, ProgramId},
+    program::{PROGRAM_STORAGE_OWNER, ProgramId, TransactionEvent},
 };
 
 use crate::{
@@ -204,7 +204,8 @@ impl V03State {
         self.public_state.insert(account_id, account);
     }
 
-    pub fn apply_state_diff(&mut self, diff: ValidatedStateDiff) -> Vec<Event> {
+    #[must_use]
+    pub fn apply_state_diff(&mut self, diff: ValidatedStateDiff) -> Vec<TransactionEvent> {
         let StateDiff {
             signer_account_ids,
             public_diff,
@@ -238,7 +239,7 @@ impl V03State {
         tx: &PublicTransaction,
         block_id: BlockId,
         timestamp: Timestamp,
-    ) -> Result<Vec<Event>, LeeError> {
+    ) -> Result<Vec<TransactionEvent>, LeeError> {
         let diff = ValidatedStateDiff::from_public_transaction(tx, self, block_id, timestamp)?;
         Ok(self.apply_state_diff(diff))
     }
@@ -251,7 +252,7 @@ impl V03State {
     ) -> Result<(), LeeError> {
         let diff =
             ValidatedStateDiff::from_privacy_preserving_transaction(tx, self, block_id, timestamp)?;
-        self.apply_state_diff(diff);
+        drop(self.apply_state_diff(diff));
         Ok(())
     }
 
@@ -260,7 +261,7 @@ impl V03State {
         tx: &ProgramDeploymentTransaction,
     ) -> Result<(), LeeError> {
         let diff = ValidatedStateDiff::from_program_deployment_transaction(tx, self)?;
-        self.apply_state_diff(diff);
+        drop(self.apply_state_diff(diff));
         Ok(())
     }
 
diff --git a/lee/state_machine/src/state/tests/events.rs b/lee/state_machine/src/state/tests/events.rs
index e82d0ced0..8674738f8 100644
--- a/lee/state_machine/src/state/tests/events.rs
+++ b/lee/state_machine/src/state/tests/events.rs
@@ -12,8 +12,18 @@ fn program_transaction<T: serde::Serialize>(
     PublicTransaction::new(message, witness_set)
 }
 
-fn payloads(events: &[lee_core::program::Event]) -> Vec<Vec<u8>> {
-    events.iter().map(|event| event.data.clone()).collect()
+fn payloads(events: &[TransactionEvent]) -> Vec<Vec<u8>> {
+    events
+        .iter()
+        .map(|event| event.event.data.clone())
+        .collect()
+}
+
+fn emitted(n: u8) -> ProgramEvent {
+    ProgramEvent {
+        selector: [n; 8],
+        data: vec![n; 4],
+    }
 }
 
 #[test]
@@ -26,7 +36,7 @@ fn emitted_events_are_returned_in_order_and_attributed_to_the_emitter() {
         emitter_id,
         account_id,
         EmitterInstruction {
-            events: vec![vec![0; 4], vec![1; 4]],
+            events: vec![emitted(0), emitted(1)],
             chain: vec![],
         },
     );
@@ -34,6 +44,13 @@ fn emitted_events_are_returned_in_order_and_attributed_to_the_emitter() {
     let events = state.transition_from_public_transaction(&tx, 1, 0).unwrap();
 
     assert_eq!(payloads(&events), vec![vec![0; 4], vec![1; 4]]);
+    assert_eq!(
+        events
+            .iter()
+            .map(|event| event.event.selector)
+            .collect::<Vec<_>>(),
+        vec![[0; 8], [1; 8]]
+    );
     assert!(events.iter().all(|event| event.program_id == emitter_id));
 }
 
@@ -44,7 +61,7 @@ fn parent_events_precede_chained_callee_events() {
     let emitter_id = crate::test_methods::event_emitter().id();
 
     let callee_instruction_data = Program::serialize_instruction(EmitterInstruction {
-        events: vec![vec![1; 4], vec![2; 4]],
+        events: vec![emitted(1), emitted(2)],
         chain: vec![],
     })
     .unwrap();
@@ -53,7 +70,7 @@ fn parent_events_precede_chained_callee_events() {
         emitter_id,
         account_id,
         EmitterInstruction {
-            events: vec![vec![0; 4]],
+            events: vec![emitted(0)],
             chain: vec![(emitter_id, callee_instruction_data)],
         },
     );
@@ -74,17 +91,17 @@ fn chained_events_follow_depth_first_pre_order() {
     let emitter_id = crate::test_methods::event_emitter().id();
 
     let grandchild = Program::serialize_instruction(EmitterInstruction {
-        events: vec![vec![2; 4]],
+        events: vec![emitted(2)],
         chain: vec![],
     })
     .unwrap();
     let first_callee = Program::serialize_instruction(EmitterInstruction {
-        events: vec![vec![1; 4]],
+        events: vec![emitted(1)],
         chain: vec![(emitter_id, grandchild)],
     })
     .unwrap();
     let second_callee = Program::serialize_instruction(EmitterInstruction {
-        events: vec![vec![3; 4]],
+        events: vec![emitted(3)],
         chain: vec![],
     })
     .unwrap();
@@ -93,7 +110,7 @@ fn chained_events_follow_depth_first_pre_order() {
         emitter_id,
         account_id,
         EmitterInstruction {
-            events: vec![vec![0; 4]],
+            events: vec![emitted(0)],
             chain: vec![(emitter_id, first_callee), (emitter_id, second_callee)],
         },
     );
@@ -139,7 +156,7 @@ fn chained_callee_events_are_attributed_to_the_callee_not_the_caller() {
     // three sibling chained calls, so the only emitting program is neither the top-level
     // program nor its caller.
     let callback_instruction_data = Program::serialize_instruction(EmitterInstruction {
-        events: vec![vec![0; 4]],
+        events: vec![emitted(0)],
         chain: vec![],
     })
     .unwrap();
diff --git a/lee/state_machine/src/state/tests/mod.rs b/lee/state_machine/src/state/tests/mod.rs
index fb99474b6..9f4929219 100644
--- a/lee/state_machine/src/state/tests/mod.rs
+++ b/lee/state_machine/src/state/tests/mod.rs
@@ -14,7 +14,8 @@ use lee_core::{
     encryption::ViewingPublicKey,
     program::{
         BlockValidityWindow, ExecutionValidationError, InstructionData, MAX_NUMBER_CHAINED_CALLS,
-        PdaSeed, ProgramId, TimestampValidityWindow, WrappedBalanceSum,
+        PdaSeed, ProgramEvent, ProgramId, TimestampValidityWindow, TransactionEvent,
+        WrappedBalanceSum,
     },
 };
 
@@ -183,7 +184,7 @@ enum FlashSwapInstruction {
 
 #[derive(serde::Serialize, serde::Deserialize)]
 struct EmitterInstruction {
-    events: Vec<Vec<u8>>,
+    events: Vec<ProgramEvent>,
     chain: Vec<(ProgramId, InstructionData)>,
 }
 
diff --git a/lee/state_machine/src/validated_state_diff/mod.rs b/lee/state_machine/src/validated_state_diff/mod.rs
index aaafa6622..2582cc3d4 100644
--- a/lee/state_machine/src/validated_state_diff/mod.rs
+++ b/lee/state_machine/src/validated_state_diff/mod.rs
@@ -8,7 +8,7 @@ use lee_core::{
     BlockId, Commitment, Nullifier, PrivacyPreservingCircuitOutput, PublicAction, Timestamp,
     account::{Account, AccountId, AccountWithMetadata},
     program::{
-        CallerData, ChainedCall, Claim, DEFAULT_PROGRAM_OWNER, Event,
+        CallerData, ChainedCall, Claim, DEFAULT_PROGRAM_OWNER, TransactionEvent,
         compute_public_authorized_pdas, validate_execution,
     },
 };
@@ -32,7 +32,7 @@ pub struct StateDiff {
     pub new_commitments: Vec<Commitment>,
     pub new_nullifiers: Vec<Nullifier>,
     pub program: Option<Program>,
-    pub events: Vec<Event>,
+    pub events: Vec<TransactionEvent>,
 }
 
 /// The validated output of executing or verifying a transaction, ready to be applied to the state.
@@ -90,7 +90,7 @@ impl ValidatedStateDiff {
             .collect();
 
         let mut state_diff: HashMap<AccountId, Account> = HashMap::new();
-        let mut events: Vec<Event> = Vec::new();
+        let mut events: Vec<TransactionEvent> = Vec::new();
 
         let initial_call = ChainedCall {
             program_id: message.program_id,
@@ -264,10 +264,15 @@ impl ValidatedStateDiff {
 
             // Write all the output event data into a proper event struct,
             // marking its emitter program.
-            events.extend(program_output.events.into_iter().map(|data| Event {
-                program_id: chained_call.program_id,
-                data,
-            }));
+            events.extend(
+                program_output
+                    .events
+                    .into_iter()
+                    .map(|event| TransactionEvent {
+                        program_id: chained_call.program_id,
+                        event,
+                    }),
+            );
 
             // Source from `program_output.pre_states`, not `chained_call.pre_states`:
             // the loop above already gates program_output's `is_authorized` via the
diff --git a/lee/state_machine/test_methods/guest/src/bin/event_emitter.rs b/lee/state_machine/test_methods/guest/src/bin/event_emitter.rs
index 199fc9dc8..6191bc8e3 100644
--- a/lee/state_machine/test_methods/guest/src/bin/event_emitter.rs
+++ b/lee/state_machine/test_methods/guest/src/bin/event_emitter.rs
@@ -1,12 +1,12 @@
 use lee_core::program::{
-    AccountPostState, ChainedCall, InstructionData, ProgramId, ProgramInput, ProgramOutput,
-    read_lee_inputs,
+    AccountPostState, ChainedCall, InstructionData, ProgramEvent, ProgramId, ProgramInput,
+    ProgramOutput, read_lee_inputs,
 };
 use serde::{Deserialize, Serialize};
 
 #[derive(Serialize, Deserialize)]
 pub struct EmitterInstruction {
-    pub events: Vec<Vec<u8>>,
+    pub events: Vec<ProgramEvent>,
     pub chain: Vec<(ProgramId, InstructionData)>,
 }
 
diff --git a/lez/common/src/transaction.rs b/lez/common/src/transaction.rs
index 9970bf7d7..5ac9f5c93 100644
--- a/lez/common/src/transaction.rs
+++ b/lez/common/src/transaction.rs
@@ -133,7 +133,7 @@ impl LeeTransaction {
         let diff = self
             .validate_on_state(state, block_id, timestamp)
             .inspect_err(|err| warn!("Error at transition {err:#?}"))?;
-        state.apply_state_diff(diff);
+        drop(state.apply_state_diff(diff));
         Ok(self)
     }
 
@@ -151,7 +151,7 @@ impl LeeTransaction {
         let diff = self
             .compute_state_diff(state, block_id, timestamp)
             .inspect_err(|err| warn!("Error at transition {err:#?}"))?;
-        state.apply_state_diff(diff);
+        drop(state.apply_state_diff(diff));
         Ok(self)
     }
 
diff --git a/lez/sequencer/core/src/lib.rs b/lez/sequencer/core/src/lib.rs
index 7b7b7db85..0f9316508 100644
--- a/lez/sequencer/core/src/lib.rs
+++ b/lez/sequencer/core/src/lib.rs
@@ -922,7 +922,7 @@ impl<BP: BlockPublisherTrait, S: StorageActorTrait> SequencerCore<BP, S> {
                     withdrawals.push(withdraw_data);
                 }
 
-                state.apply_state_diff(validated_diff);
+                drop(state.apply_state_diff(validated_diff));
             }
             TransactionOrigin::Sequencer => {
                 let LeeTransaction::Public(public_tx) = tx else {