Relax requirements that a checkpoint state must be epoch aligned post-gloas

beacon_node/beacon_chain/src/beacon_fork_choice_store.rs

@@ -172,8 +172,9 @@ where
         let mut anchor_state = anchor.beacon_state;
         let mut anchor_block_header = anchor_state.latest_block_header().clone();
 
-        // The anchor state MUST be on an epoch boundary (it should be advanced by the caller).
-        if !anchor_state
+        // Pre-gloas the anchor state MUST be on an epoch boundary (it should be advanced by the caller).
+        // Post-gloas this requirement is relaxed.
+        if !anchor_state.fork_name_unchecked().gloas_enabled() && !anchor_state
             .slot()
             .as_u64()
             .is_multiple_of(E::slots_per_epoch())

beacon_node/beacon_chain/src/builder.rs

@@ -42,6 +42,7 @@ use store::{Error as StoreError, HotColdDB, ItemStore, KeyValueStoreOp};
 use task_executor::{ShutdownReason, TaskExecutor};
 use tracing::{debug, error, info, warn};
 use tree_hash::TreeHash;
+use types::StatePayloadStatus;
 use types::data::CustodyIndex;
 use types::{
     BeaconBlock, BeaconState, BlobSidecarList, ChainSpec, ColumnIndex, DataColumnSidecarList,
@@ -433,9 +434,15 @@ where
             .clone()
             .ok_or("weak_subjectivity_state requires a store")?;
 
-        // Ensure the state is advanced to an epoch boundary.
+        // Pre-gloas ensure the state is advanced to an epoch boundary.
+        // Post-gloas checkpoint states are always pending (post-block) and cannot
+        // be advanced across epoch boundaries without first checking for a payload
+        // envelope.
         let slots_per_epoch = E::slots_per_epoch();
-        if weak_subj_state.slot() % slots_per_epoch != 0 {
+
+        if !weak_subj_state.fork_name_unchecked().gloas_enabled()
+            && weak_subj_state.slot() % slots_per_epoch != 0
+        {
             debug!(
                 state_slot = %weak_subj_state.slot(),
                 block_slot = %weak_subj_block.slot(),
@@ -568,7 +575,7 @@ where
         // Write the state, block and blobs non-atomically, it doesn't matter if they're forgotten
         // about on a crash restart.
         store
-            .update_finalized_state(
+            .set_initial_finalized_state(
                 weak_subj_state_root,
                 weak_subj_block_root,
                 weak_subj_state.clone(),
@@ -617,7 +624,15 @@ where
                 .map_err(|e| format!("Failed to initialize data column info: {:?}", e))?,
         );
 
-        // TODO(gloas): add check that checkpoint state is Pending
+        if weak_subj_state.fork_name_unchecked().gloas_enabled()
+            && weak_subj_state.payload_status() != StatePayloadStatus::Pending
+        {
+            return Err(format!(
+                "Checkpoint sync state must be Pending (post-block) for Gloas, got {:?}",
+                weak_subj_state.payload_status()
+            ));
+        }
+
         let snapshot = BeaconSnapshot {
             beacon_block_root: weak_subj_block_root,
             execution_envelope: None,

beacon_node/store/src/errors.rs

@@ -101,6 +101,7 @@ pub enum Error {
         from_state_slot: Slot,
         target_slot: Slot,
     },
+    FinalizedStateAlreadySet,
 }
 
 pub trait HandleUnavailable<T> {

beacon_node/store/src/hot_cold_store.rs

@@ -474,6 +474,25 @@ impl<E: EthSpec, Hot: ItemStore<E>, Cold: ItemStore<E>> HotColdDB<E, Hot, Cold>
         }
     }
 
+    /// See [`StateCache::set_initial_finalized_state`](crate::state_cache::StateCache::set_initial_finalized_state).  
+    pub fn set_initial_finalized_state(
+        &self,
+        state_root: Hash256,
+        block_root: Hash256,
+        state: BeaconState<E>,
+    ) -> Result<(), Error> {
+        let start_slot = self.get_anchor_info().anchor_slot;
+        let pre_finalized_slots_to_retain = self
+            .hierarchy
+            .closest_layer_points(state.slot(), start_slot);
+        self.state_cache.lock().set_initial_finalized_state(
+            state_root,
+            block_root,
+            state,
+            &pre_finalized_slots_to_retain,
+        )
+    }
+
     pub fn update_finalized_state(
         &self,
         state_root: Hash256,

beacon_node/store/src/state_cache.rs

@@ -124,6 +124,36 @@ impl<E: EthSpec> StateCache<E> {
         roots
     }
 
+    /// Used by checkpoint sync to initialize the finalized state in the state cache.
+    ///
+    /// Post-gloas the checkpoint state may not be epoch-aligned, e.g when the epoch boundary
+    /// slot is skipped. We relax the epoch-alignment requirement for the initial state only.
+    /// Runtime finalization updates should use [`update_finalized_state`](Self::update_finalized_state),
+    /// which enforces alignment.  
+    pub fn set_initial_finalized_state(
+        &mut self,
+        state_root: Hash256,
+        block_root: Hash256,
+        state: BeaconState<E>,
+        pre_finalized_slots_to_retain: &[Slot],
+    ) -> Result<(), Error> {
+        if self.finalized_state.is_some() {
+            return Err(Error::FinalizedStateAlreadySet);
+        }
+
+        if !state.fork_name_unchecked().gloas_enabled() && state.slot() % E::slots_per_epoch() != 0
+        {
+            return Err(Error::FinalizedStateUnaligned);
+        }
+
+        self.update_finalized_state_inner(
+            state_root,
+            block_root,
+            state,
+            pre_finalized_slots_to_retain,
+        )
+    }
+
     pub fn update_finalized_state(
         &mut self,
         state_root: Hash256,
@@ -135,6 +165,21 @@ impl<E: EthSpec> StateCache<E> {
             return Err(Error::FinalizedStateUnaligned);
         }
 
+        self.update_finalized_state_inner(
+            state_root,
+            block_root,
+            state,
+            pre_finalized_slots_to_retain,
+        )
+    }
+
+    fn update_finalized_state_inner(
+        &mut self,
+        state_root: Hash256,
+        block_root: Hash256,
+        state: BeaconState<E>,
+        pre_finalized_slots_to_retain: &[Slot],
+    ) -> Result<(), Error> {
         if self
             .finalized_state
             .as_ref()