changes

consensus/proto_array/src/fork_choice_test_definition.rs

@@ -91,6 +91,7 @@ pub enum Operation {
     AssertHeadPayloadStatus {
         head_root: Hash256,
         expected_status: PayloadStatus,
+        current_slot: Slot,
     },
     SetPayloadTiebreak {
         block_root: Hash256,
@@ -456,9 +457,13 @@ impl ForkChoiceTestDefinition {
                 Operation::AssertHeadPayloadStatus {
                     head_root,
                     expected_status,
+                    current_slot,
                 } => {
                     let actual = fork_choice
-                        .head_payload_status::<MainnetEthSpec>(&head_root)
+                        .head_payload_status::<MainnetEthSpec>(
+                            &head_root,
+                            current_slot,
+                        )
                         .unwrap_or_else(|| {
                             panic!(
                                 "AssertHeadPayloadStatus: head root not found at op index {}",

consensus/proto_array/src/fork_choice_test_definition/gloas_payload.rs

@@ -145,6 +145,7 @@ pub fn get_gloas_payload_probe_test_definition() -> ForkChoiceTestDefinition {
     ops.push(Operation::AssertHeadPayloadStatus {
         head_root: get_root(1),
         expected_status: PayloadStatus::Empty,
+        current_slot: Slot::new(0),
     });
 
     // Flip validator 0 to Empty; both bits now clear.
@@ -170,6 +171,7 @@ pub fn get_gloas_payload_probe_test_definition() -> ForkChoiceTestDefinition {
     ops.push(Operation::AssertHeadPayloadStatus {
         head_root: get_root(1),
         expected_status: PayloadStatus::Empty,
+        current_slot: Slot::new(0),
     });
 
     // Same-slot attestation to a new head candidate should be Pending (no payload bucket change).
@@ -204,6 +206,7 @@ pub fn get_gloas_payload_probe_test_definition() -> ForkChoiceTestDefinition {
     ops.push(Operation::AssertHeadPayloadStatus {
         head_root: get_root(5),
         expected_status: PayloadStatus::Empty,
+        current_slot: Slot::new(0),
     });
 
     ForkChoiceTestDefinition {

consensus/proto_array/src/proto_array.rs

@@ -1448,8 +1448,8 @@ fn child_matches_parent_payload_preference(
         && parent_v29.empty_payload_weight > parent_v29.full_payload_weight
     {
         false
-    } else {
-        // Equal weights (or current-slot parent): tiebreaker per spec.
+    } else if use_tiebreaker_only {
+        // Previous slot: should_extend_payload = is_payload_timely && is_payload_data_available.
         is_payload_timely(
             &parent_v29.payload_timeliness_votes,
             ptc_size,
@@ -1459,6 +1459,10 @@ fn child_matches_parent_payload_preference(
             ptc_size,
             parent_v29.payload_received,
         )
+    } else {
+        // Not previous slot: should_extend_payload = true.
+        // Full wins the tiebreaker (1 > 0) when the payload has been received.
+        parent_v29.payload_received
     };
     if prefers_full {
         child_v29.parent_payload_status == PayloadStatus::Full

consensus/proto_array/src/proto_array_fork_choice.rs

@@ -991,29 +991,43 @@ impl ProtoArrayForkChoice {
             .map(|node| node.weight())
     }
 
-    /// Returns the payload status of the head node based on accumulated weights.
+    /// Returns the payload status of the head node based on accumulated weights and tiebreaker.
     ///
     /// Returns `Full` if `full_payload_weight > empty_payload_weight`.
     /// Returns `Empty` if `empty_payload_weight > full_payload_weight`.
-    /// On ties, consult the node's runtime `payload_tiebreak`: prefer `Full` only when timely and
-    /// data is available, otherwise `Empty`.
-    /// Returns `Empty` otherwise. Returns `None` for V17 nodes.
-    pub fn head_payload_status<E: EthSpec>(&self, head_root: &Hash256) -> Option<PayloadStatus> {
+    /// On ties:
+    ///   - Previous slot (`slot + 1 == current_slot`): prefer Full only when timely and
+    ///     data available (per `should_extend_payload`).
+    ///   - Otherwise: prefer Full when payload has been received.
+    /// Returns `None` for V17 nodes.
+    pub fn head_payload_status<E: EthSpec>(
+        &self,
+        head_root: &Hash256,
+        current_slot: Slot,
+    ) -> Option<PayloadStatus> {
         let node = self.get_proto_node(head_root)?;
         let v29 = node.as_v29().ok()?;
         if v29.full_payload_weight > v29.empty_payload_weight {
             Some(PayloadStatus::Full)
         } else if v29.empty_payload_weight > v29.full_payload_weight {
             Some(PayloadStatus::Empty)
-        } else if is_payload_timely(
-            &v29.payload_timeliness_votes,
-            E::ptc_size(),
-            v29.payload_received,
-        ) && is_payload_data_available(
-            &v29.payload_data_availability_votes,
-            E::ptc_size(),
-            v29.payload_received,
-        ) {
+        } else if node.slot() + 1 == current_slot {
+            // Previous slot: should_extend_payload = is_payload_timely && is_payload_data_available
+            if is_payload_timely(
+                &v29.payload_timeliness_votes,
+                E::ptc_size(),
+                v29.payload_received,
+            ) && is_payload_data_available(
+                &v29.payload_data_availability_votes,
+                E::ptc_size(),
+                v29.payload_received,
+            ) {
+                Some(PayloadStatus::Full)
+            } else {
+                Some(PayloadStatus::Empty)
+            }
+        } else if v29.payload_received {
+            // Not previous slot: Full wins tiebreaker (1 > 0) when payload received.
             Some(PayloadStatus::Full)
         } else {
             Some(PayloadStatus::Empty)