Defer block import

beacon/validator/src/main/java/tech/pegasys/teku/validator/coordinator/ValidatorApiHandler.java

@@ -797,6 +797,10 @@ public SafeFuture<Optional<List<ValidatorLivenessAtEpoch>>> getValidatorsLivenes
         validatorIndices, epoch, chainDataProvider.getCurrentEpoch());
   }
 
+  public boolean isBlockInProductionAtSlot(final UInt64 slot) {
+    return blockProductionPreparationContextBySlotCache.containsKey(slot);
+  }
+
   private Optional<SubmitDataError> fromInternalValidationResult(
       final InternalValidationResult internalValidationResult, final int resultIndex) {
     if (!internalValidationResult.isReject()) {

ethereum/statetransition/src/main/java/tech/pegasys/teku/statetransition/block/BlockInProductionProvider.java

@@ -0,0 +1,21 @@
+/*
+ * Copyright Consensys Software Inc., 2025
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except in compliance with
+ * the License. You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software distributed under the License is distributed on
+ * an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the License for the
+ * specific language governing permissions and limitations under the License.
+ */
+
+package tech.pegasys.teku.statetransition.block;
+
+import tech.pegasys.teku.infrastructure.unsigned.UInt64;
+
+@FunctionalInterface
+public interface BlockInProductionProvider {
+  boolean isBlockInProductionAtSlot(UInt64 slot);
+}

ethereum/statetransition/src/main/java/tech/pegasys/teku/statetransition/block/BlockManager.java

@@ -13,14 +13,17 @@
 
 package tech.pegasys.teku.statetransition.block;
 
+import java.time.Duration;
 import java.util.List;
 import java.util.Map;
 import java.util.Optional;
 import java.util.concurrent.RejectedExecutionException;
+import java.util.function.Supplier;
 import org.apache.logging.log4j.LogManager;
 import org.apache.logging.log4j.Logger;
 import org.apache.tuweni.bytes.Bytes32;
 import tech.pegasys.teku.ethereum.events.SlotEventsChannel;
+import tech.pegasys.teku.infrastructure.async.AsyncRunner;
 import tech.pegasys.teku.infrastructure.async.SafeFuture;
 import tech.pegasys.teku.infrastructure.exceptions.ExceptionUtil;
 import tech.pegasys.teku.infrastructure.logging.EventLogger;
@@ -64,6 +67,9 @@ public class BlockManager extends Service
   private final Subscribers<PreImportBlockListener> preImportBlockSubscribers =
       Subscribers.create(true);
 
+  private final AsyncRunner asyncRunner;
+
+  private final BlockInProductionProvider blockInProductionProvider;
   private final Optional<BlockImportMetrics> blockImportMetrics;
 
   public BlockManager(
@@ -76,6 +82,8 @@ public BlockManager(
       final BlockValidator blockValidator,
       final TimeProvider timeProvider,
       final EventLogger eventLogger,
+      final BlockInProductionProvider blockInProductionProvider,
+      final AsyncRunner asyncRunner,
       final Optional<BlockImportMetrics> blockImportMetrics) {
     this.recentChainData = recentChainData;
     this.blockImporter = blockImporter;
@@ -86,6 +94,8 @@ public BlockManager(
     this.blockValidator = blockValidator;
     this.timeProvider = timeProvider;
     this.eventLogger = eventLogger;
+    this.blockInProductionProvider = blockInProductionProvider;
+    this.asyncRunner = asyncRunner;
     this.blockImportMetrics = blockImportMetrics;
   }
 
@@ -214,9 +224,30 @@ private SafeFuture<BlockImportResult> doImportBlock(
         .or(() -> handleKnownBlock(block))
         .orElseGet(
             () ->
-                handleBlockImport(block, blockImportPerformance, blockBroadcastValidator, origin)
-                    .thenPeek(
-                        result -> lateBlockImportCheck(blockImportPerformance, block, result)));
+                deferIfBlockInProduction(
+                    block.getSlot(),
+                    () ->
+                        handleBlockImport(
+                                block, blockImportPerformance, blockBroadcastValidator, origin)
+                            .thenPeek(
+                                result ->
+                                    lateBlockImportCheck(blockImportPerformance, block, result))));
+  }
+
+  private SafeFuture<BlockImportResult> deferIfBlockInProduction(
+      final UInt64 blockSlot, final Supplier<SafeFuture<BlockImportResult>> blockImport) {
+    final boolean blockFromThePastWhileBlockIsInProduction =
+        recentChainData
+            .getCurrentSlot()
+            .map(
+                currentSlot ->
+                    blockSlot.isLessThan(currentSlot)
+                        && blockInProductionProvider.isBlockInProductionAtSlot(currentSlot))
+            .orElse(false);
+    if (!blockFromThePastWhileBlockIsInProduction) {
+      return blockImport.get();
+    }
+    return asyncRunner.runAfterDelay(blockImport::get, Duration.ofSeconds(2));
   }
 
   private Optional<BlockImportResult> propagateInvalidity(final SignedBeaconBlock block) {

services/beaconchain/src/main/java/tech/pegasys/teku/services/beaconchain/BeaconChainController.java

@@ -1825,6 +1825,8 @@ public void initBlockManager() {
             blockValidator,
             timeProvider,
             EVENT_LOG,
+            slot -> validatorApiHandler.isBlockInProductionAtSlot(slot),
+            beaconAsyncRunner,
             importMetrics);
     if (spec.isMilestoneSupported(SpecMilestone.BELLATRIX)) {
       final FailedExecutionPool failedExecutionPool =