Modify notify_forkchoice_updated

fork_choice/safe-block.md

@@ -26,12 +26,16 @@ def get_safe_execution_block_hash(store: Store) -> Hash32:
     safe_block_root = retrieve_fast_confirmed_root()
     safe_block = store.blocks[safe_block_root]
 
-    # Return Hash32() if no payload is yet justified
+    if compute_epoch_at_slot(safe_block.slot) >= GLOAS_FORK_EPOCH:
+        safe_block_bid = safe_block.body.signed_execution_payload_bid.message
+        return safe_block_bid.parent_block_hash
     if compute_epoch_at_slot(safe_block.slot) >= BELLATRIX_FORK_EPOCH:
         return safe_block.body.execution_payload.block_hash
     else:
+        # Return Hash32() if no safe block is yet available
         return Hash32()
 ```
 
 *Note*: This helper uses beacon block container extended in
-[Bellatrix](../specs/bellatrix/beacon-chain.md).
+[Bellatrix](../specs/bellatrix/beacon-chain.md) and
+[Gloas](../specs/gloas/beacon-chain.md).

specs/gloas/fork-choice.md

@@ -7,6 +7,9 @@
 - [Introduction](#introduction)
 - [Types](#types)
 - [Constants](#constants)
+- [Protocols](#protocols)
+  - [`ExecutionEngine`](#executionengine)
+    - [Modified `notify_forkchoice_updated`](#modified-notify_forkchoice_updated)
 - [Helpers](#helpers)
   - [New `ForkChoiceNode`](#new-forkchoicenode)
   - [Modified `PayloadAttributes`](#modified-payloadattributes)
@@ -75,6 +78,42 @@ This is the modification of the fork-choice accompanying the Gloas upgrade.
 | `PTC_TIMELINESS_INDEX`               | `1`                     |
 | `NUM_BLOCK_TIMELINESS_DEADLINES`     | `2`                     |
 
+## Protocols
+
+### `ExecutionEngine`
+
+*Note*: The `notify_forkchoice_updated` function is modified in the
+`ExecutionEngine` protocol at the Gloas upgrade.
+
+#### Modified `notify_forkchoice_updated`
+
+The only modification is the computation of the `finalized_block_hash` and
+`safe_block_hash` that Consensus layer client passes to the call of this
+function.
+
+Starting with Gloas `finalized_block_hash` value **MUST** be computed as the
+following. Let:
+
+- `finalized_block = store.blocks[store.finalized_checkpoint.root]`
+- `finalized_block_bid = finalized_block.body.signed_execution_payload_bid.message`
+
+Then `finalized_block_hash = finalized_block_bid.parent_block_hash`.
+
+*Note:* The post-Gloas `safe_block_hash` computation is handled by extending
+[`get_safe_execution_block_hash(store: Store)`](../../fork_choice/safe-block.md#get_safe_execution_block_hash).
+
+```python
+def notify_forkchoice_updated(
+    self: ExecutionEngine,
+    head_block_hash: Hash32,
+    # [Modified in Gloas:EIP7732]
+    safe_block_hash: Hash32,
+    # [Modified in Gloas:EIP7732]
+    finalized_block_hash: Hash32,
+    payload_attributes: Optional[PayloadAttributes],
+) -> Optional[PayloadId]: ...
+```
+
 ## Helpers
 
 ### New `ForkChoiceNode`