fix: tighten genesis block fallback to match empty body root only

fix: restore genesis_block bid population for ef-tests and add fallback for external genesis for kurtosis

beacon_node/beacon_chain/src/builder.rs

@@ -46,8 +46,8 @@ use tracing::{debug, error, info, warn};
 use tree_hash::TreeHash;
 use types::data::CustodyIndex;
 use types::{
-    BeaconState, BlobSidecarList, ChainSpec, ColumnIndex, DataColumnSidecarList, Epoch, EthSpec,
-    Hash256, SignedBeaconBlock, Slot,
+    BeaconBlock, BeaconState, BlobSidecarList, ChainSpec, ColumnIndex, DataColumnSidecarList,
+    Epoch, EthSpec, Hash256, SignedBeaconBlock, Slot,
 };
 
 /// An empty struct used to "witness" all the `BeaconChainTypes` traits. It has no user-facing
@@ -1177,9 +1177,21 @@ fn make_genesis_block<E: EthSpec>(
     genesis_state: &mut BeaconState<E>,
     spec: &ChainSpec,
 ) -> Result<SignedBeaconBlock<E>, String> {
+    // For Gloas, genesis_block() populates the bid in the block body. However, if
+    // the genesis state was produced by an external tool (e.g. ethereum-genesis-generator),
+    // its latest_block_header.body_root may correspond to an empty block. In that case,
+    // use an empty block so the stored block root matches what fork choice derives from
+    // the state's latest_block_header.
     let mut block = genesis_block(genesis_state, spec)
         .map_err(|e| format!("Error building genesis block: {:?}", e))?;
 
+    let state_body_root = genesis_state.latest_block_header().body_root;
+    if state_body_root != block.body_root()
+        && state_body_root == BeaconBlock::<E>::empty(spec).body_root()
+    {
+        block = BeaconBlock::empty(spec);
+    }
+
     *block.state_root_mut() = genesis_state
         .update_tree_hash_cache()
         .map_err(|e| format!("Error hashing genesis state: {:?}", e))?;

consensus/fork_choice/src/fork_choice.rs

@@ -416,11 +416,24 @@ where
 
         let (execution_status, execution_payload_parent_hash, execution_payload_block_hash) =
             if let Ok(signed_bid) = anchor_block.message().body().signed_execution_payload_bid() {
-                // Gloas: execution status is irrelevant post-Gloas; payload validation
-                // is decoupled from beacon blocks.
+                // At Gloas genesis the block bid is empty (all zeros) per spec, but the
+                // state holds the EL genesis hash in `latest_block_hash`. Use it so the
+                // first forkchoice update sends a valid head to the EL.
+                let parent_hash = if anchor_block.slot() == spec.genesis_slot
+                    && anchor_state.slot() == spec.genesis_slot
+                    && signed_bid.message.parent_block_hash.into_root().is_zero()
+                    && signed_bid.message.block_hash.into_root().is_zero()
+                {
+                    *anchor_state
+                        .latest_block_hash()
+                        .map_err(Error::BeaconStateError)?
+                } else {
+                    signed_bid.message.parent_block_hash
+                };
+
                 (
                     ExecutionStatus::irrelevant(),
-                    Some(signed_bid.message.parent_block_hash),
+                    Some(parent_hash),
                     Some(signed_bid.message.block_hash),
                 )
             } else if let Ok(execution_payload) = anchor_block.message().execution_payload() {