diff --git a/src/Nethermind/Nethermind.Consensus/EngineApiVersions.cs b/src/Nethermind/Nethermind.Consensus/EngineApiVersions.cs
index d3c7cde9be7d..9d8285ccdec2 100644
--- a/src/Nethermind/Nethermind.Consensus/EngineApiVersions.cs
+++ b/src/Nethermind/Nethermind.Consensus/EngineApiVersions.cs
@@ -3,12 +3,41 @@
 
 namespace Nethermind.Consensus;
 
+/// <summary>
+/// Engine API method version constants, grouped by method.
+/// Use the nested classes (<see cref="Fcu"/>, <see cref="NewPayload"/>, <see cref="GetPayload"/>)
+/// to select the appropriate version when calling Execution Engine API methods.
+/// </summary>
 public static class EngineApiVersions
 {
-    public const int Paris = 1;
-    public const int Shanghai = 2;
-    public const int Cancun = 3;
-    public const int Prague = 4;
-    public const int Osaka = 5;
-    public const int Amsterdam = 6;
+    /// <summary>forkchoiceUpdated method versions.</summary>
+    /// <remarks>Multiple forks may share the same version (e.g. Cancun/Prague/Osaka all use V3).</remarks>
+    public static class Fcu
+    {
+        public const int V1 = 1; // Paris
+        public const int V2 = 2; // Shanghai
+        public const int V3 = 3; // Cancun/Prague/Osaka
+        public const int V4 = 4; // Amsterdam
+    }
+
+    /// <summary>engine_newPayload method versions.</summary>
+    public static class NewPayload
+    {
+        public const int V1 = 1; // Paris
+        public const int V2 = 2; // Shanghai
+        public const int V3 = 3; // Cancun
+        public const int V4 = 4; // Prague/Osaka
+        public const int V5 = 5; // Amsterdam
+    }
+
+    /// <summary>engine_getPayload method versions.</summary>
+    public static class GetPayload
+    {
+        public const int V1 = 1; // Paris
+        public const int V2 = 2; // Shanghai
+        public const int V3 = 3; // Cancun
+        public const int V4 = 4; // Prague
+        public const int V5 = 5; // Osaka
+        public const int V6 = 6; // Amsterdam
+    }
 }
diff --git a/src/Nethermind/Nethermind.Consensus/Producers/PayloadAttributes.cs b/src/Nethermind/Nethermind.Consensus/Producers/PayloadAttributes.cs
index 2d9a72fb65c1..9e80c7316e38 100644
--- a/src/Nethermind/Nethermind.Consensus/Producers/PayloadAttributes.cs
+++ b/src/Nethermind/Nethermind.Consensus/Producers/PayloadAttributes.cs
@@ -18,9 +18,9 @@ public class PayloadAttributes
 {
     public ulong Timestamp { get; set; }
 
-    public Hash256 PrevRandao { get; set; }
+    public Hash256? PrevRandao { get; set; }
 
-    public Address SuggestedFeeRecipient { get; set; }
+    public Address? SuggestedFeeRecipient { get; set; }
 
     public Withdrawal[]? Withdrawals { get; set; }
 
@@ -34,7 +34,7 @@ public class PayloadAttributes
 
     public string ToString(string indentation)
     {
-        var sb = new StringBuilder($"{indentation}{nameof(PayloadAttributes)} {{")
+        StringBuilder sb = new StringBuilder($"{indentation}{nameof(PayloadAttributes)} {{")
             .Append($"{nameof(Timestamp)}: {Timestamp}, ")
             .Append($"{nameof(PrevRandao)}: {PrevRandao}, ")
             .Append($"{nameof(SuggestedFeeRecipient)}: {SuggestedFeeRecipient}");
@@ -97,10 +97,10 @@ protected virtual int WritePayloadIdMembers(BlockHeader parentHeader, Span<byte>
         BinaryPrimitives.WriteUInt64BigEndian(inputSpan.Slice(position, sizeof(ulong)), Timestamp);
         position += sizeof(ulong);
 
-        PrevRandao.Bytes.CopyTo(inputSpan.Slice(position, Keccak.Size));
+        (PrevRandao ?? Keccak.Zero).Bytes.CopyTo(inputSpan.Slice(position, Keccak.Size));
         position += Keccak.Size;
 
-        SuggestedFeeRecipient.Bytes.CopyTo(inputSpan.Slice(position, Address.Size));
+        (SuggestedFeeRecipient ?? Address.Zero).Bytes.CopyTo(inputSpan.Slice(position, Address.Size));
         position += Address.Size;
 
         if (Withdrawals is not null)
@@ -127,34 +127,48 @@ protected virtual int WritePayloadIdMembers(BlockHeader parentHeader, Span<byte>
         return position;
     }
 
+    /// <summary>
+    /// Whether this FCU version supports the given fork (identified by its payload attributes version).
+    /// General rule: FCU version must match the payload attributes version.
+    /// </summary>
+    private static bool IsSupportedFcuForkCombination(int fcuVersion, int payloadVersion) =>
+        (fcuVersion, payloadVersion) switch
+        {
+            // Exception: FCUv2 also accepts Paris (V1) attributes for backward compatibility.
+            (EngineApiVersions.Fcu.V2, PayloadAttributesVersions.V1) => true,
+            _ => fcuVersion == payloadVersion
+        };
+
+    /// <summary>
+    /// Validates that the payload attributes version is consistent with the FCU version and the fork indicated by the timestamp.
+    /// </summary>
+    /// <returns>
+    /// <see cref="PayloadAttributesValidationResult.UnsupportedFork"/> — FCU version doesn't support this fork (post-Paris only);
+    /// <see cref="PayloadAttributesValidationResult.InvalidPayloadAttributes"/> — attributes structure doesn't match the fork;
+    /// <see cref="PayloadAttributesValidationResult.Success"/> — valid combination.
+    /// </returns>
     private static PayloadAttributesValidationResult ValidateVersion(
-        int apiVersion,
+        int fcuVersion,
         int actualVersion,
         int timestampVersion,
         string methodName,
         [NotNullWhen(false)] out string? error)
     {
-        // version calculated from parameters should match api version
-        if (actualVersion != apiVersion)
+        // This FCU version doesn't support this fork at all (e.g. V3 attrs sent to FCUv2).
+        if (!IsSupportedFcuForkCombination(fcuVersion, actualVersion))
         {
-            // except of Shanghai api handling Paris fork
-            if (apiVersion == EngineApiVersions.Shanghai && timestampVersion == PayloadAttributesVersions.Paris ||
-                apiVersion == EngineApiVersions.Amsterdam && timestampVersion == PayloadAttributesVersions.Amsterdam)
-            {
-
-                error = null;
-                return PayloadAttributesValidationResult.Success;
-            }
-
-            error = $"{methodName}{apiVersion} expected";
-            return actualVersion <= EngineApiVersions.Paris ? PayloadAttributesValidationResult.InvalidParams : PayloadAttributesValidationResult.InvalidPayloadAttributes;
+            error = $"{methodName}{fcuVersion} expected";
+            return PayloadAttributesValidationResult.InvalidPayloadAttributes;
         }
 
-        // timestamp should correspond to proper api version
-        if (timestampVersion != apiVersion)
+        // Attributes structure doesn't match what the fork expects (e.g. V3 attrs sent to when FCUv3 not yet activated in spec).
+        if (actualVersion != timestampVersion)
         {
             error = $"{methodName}{timestampVersion} expected";
-            return timestampVersion <= EngineApiVersions.Paris ? PayloadAttributesValidationResult.InvalidParams : PayloadAttributesValidationResult.UnsupportedFork;
+            // FCU also doesn't support this fork → UnsupportedFork (post-Paris only)
+            return fcuVersion != timestampVersion && timestampVersion >= PayloadAttributesVersions.V2
+                ? PayloadAttributesValidationResult.UnsupportedFork
+                : PayloadAttributesValidationResult.InvalidPayloadAttributes;
         }
 
         error = null;
@@ -163,44 +177,71 @@ private static PayloadAttributesValidationResult ValidateVersion(
 
     public virtual PayloadAttributesValidationResult Validate(
         ISpecProvider specProvider,
-        int apiVersion,
-        [NotNullWhen(false)] out string? error) =>
-        ValidateVersion(
-            apiVersion: apiVersion,
-            actualVersion: this.GetVersion(),
-            timestampVersion: specProvider.GetSpec(ForkActivation.TimestampOnly(Timestamp))
-                .ExpectedPayloadAttributesVersion(),
+        int fcuVersion,
+        [NotNullWhen(false)] out string? error)
+    {
+        int actualVersion = this.GetVersion();
+        PayloadAttributesValidationResult result = ValidateVersion(
+            fcuVersion,
+            actualVersion,
+            timestampVersion: specProvider.GetSpec(ForkActivation.TimestampOnly(Timestamp)).ExpectedPayloadAttributesVersion(),
             "PayloadAttributesV",
             out error);
+
+        if (result == PayloadAttributesValidationResult.Success)
+        {
+            error = ValidateFields(actualVersion);
+            result = error is null
+                ? PayloadAttributesValidationResult.Success
+                : PayloadAttributesValidationResult.InvalidPayloadAttributes;
+        }
+
+        return result;
+    }
+
+    private string? ValidateFields(int actualVersion)
+    {
+        if (Timestamp == 0) return $"{nameof(Timestamp)} must be provided";
+        if (PrevRandao is null) return $"{nameof(PrevRandao)} must be provided";
+        if (SuggestedFeeRecipient is null) return $"{nameof(SuggestedFeeRecipient)} must be provided";
+
+        return actualVersion switch
+        {
+            >= PayloadAttributesVersions.V2 when Withdrawals is null => $"{nameof(Withdrawals)} must be provided",
+            >= PayloadAttributesVersions.V3 when ParentBeaconBlockRoot is null => $"{nameof(ParentBeaconBlockRoot)} must be provided",
+            >= PayloadAttributesVersions.V4 when SlotNumber is null => $"{nameof(SlotNumber)} must be provided",
+            _ => null
+        };
+    }
 }
 
-public enum PayloadAttributesValidationResult : byte { Success, InvalidParams, InvalidPayloadAttributes, UnsupportedFork };
+public enum PayloadAttributesValidationResult : byte { Success, InvalidPayloadAttributes, UnsupportedFork };
 
 public static class PayloadAttributesExtensions
 {
     public static int GetVersion(this PayloadAttributes executionPayload) =>
         executionPayload switch
         {
-            { SlotNumber: not null } => PayloadAttributesVersions.Amsterdam,
-            { ParentBeaconBlockRoot: not null, Withdrawals: not null } => PayloadAttributesVersions.Cancun,
-            { Withdrawals: not null } => PayloadAttributesVersions.Shanghai,
-            _ => PayloadAttributesVersions.Paris
+            { SlotNumber: not null } => PayloadAttributesVersions.V4,
+            { ParentBeaconBlockRoot: not null } => PayloadAttributesVersions.V3,
+            { Withdrawals: not null } => PayloadAttributesVersions.V2,
+            _ => PayloadAttributesVersions.V1
         };
 
     public static int ExpectedPayloadAttributesVersion(this IReleaseSpec spec) =>
         spec switch
         {
-            { IsEip7843Enabled: true } => PayloadAttributesVersions.Amsterdam,
-            { IsEip4844Enabled: true } => PayloadAttributesVersions.Cancun,
-            { WithdrawalsEnabled: true } => PayloadAttributesVersions.Shanghai,
-            _ => PayloadAttributesVersions.Paris
+            { IsEip7843Enabled: true } => PayloadAttributesVersions.V4,
+            { IsEip4844Enabled: true } => PayloadAttributesVersions.V3,
+            { WithdrawalsEnabled: true } => PayloadAttributesVersions.V2,
+            _ => PayloadAttributesVersions.V1
         };
 }
 
 public static class PayloadAttributesVersions
 {
-    public const int Paris = 1;
-    public const int Shanghai = 2;
-    public const int Cancun = 3;
-    public const int Amsterdam = 4;
+    public const int V1 = 1; // Paris
+    public const int V2 = 2; // Shanghai
+    public const int V3 = 3; // Cancun/Prague/Osaka
+    public const int V4 = 4; // Amsterdam
 }
diff --git a/src/Nethermind/Nethermind.Merge.Plugin.Test/EngineModuleTests.V1.cs b/src/Nethermind/Nethermind.Merge.Plugin.Test/EngineModuleTests.V1.cs
index 82e7a65ccef6..a24b08055eb4 100644
--- a/src/Nethermind/Nethermind.Merge.Plugin.Test/EngineModuleTests.V1.cs
+++ b/src/Nethermind/Nethermind.Merge.Plugin.Test/EngineModuleTests.V1.cs
@@ -1643,7 +1643,7 @@ private async Task<ExecutionPayload> BuildAndGetPayloadResult(MergeTestBlockchai
         Hash256 parentHead = chain.BlockTree.Head!.ParentHash!;
 
         return await BuildAndGetPayloadResult(rpc, chain, startingHead, parentHead, startingHead,
-            payloadAttributes.Timestamp, payloadAttributes.PrevRandao!, payloadAttributes.SuggestedFeeRecipient);
+            payloadAttributes.Timestamp, payloadAttributes.PrevRandao!, payloadAttributes.SuggestedFeeRecipient!);
     }
 
     private async Task<ExecutionPayload> BuildAndGetPayloadResult(MergeTestBlockchain chain,
@@ -1676,4 +1676,64 @@ private void AssertExecutionStatusNotChangedV1(IBlockFinder blockFinder, Hash256
         Assert.That(blockFinder.FinalizedHash, Is.Not.EqualTo(finalizedBlockHash));
         Assert.That(blockFinder.SafeHash, Is.Not.EqualTo(confirmedBlockHash));
     }
+
+    public static IEnumerable<TestCaseData> ForkchoiceUpdatedFieldValidationTestCases
+    {
+        get
+        {
+            static PayloadAttributes Attrs(
+                Withdrawal[]? withdrawals = null,
+                Hash256? parentBeaconBlockRoot = null,
+                ulong? slotNumber = null,
+                Action<PayloadAttributes>? mutate = null)
+            {
+                PayloadAttributes attrs = new()
+                {
+                    Timestamp = 1,
+                    PrevRandao = Keccak.Zero,
+                    SuggestedFeeRecipient = Address.Zero,
+                    Withdrawals = withdrawals,
+                    ParentBeaconBlockRoot = parentBeaconBlockRoot,
+                    SlotNumber = slotNumber,
+                };
+                mutate?.Invoke(attrs);
+                return attrs;
+            }
+
+            static TestCaseData InvalidFieldCase(IReleaseSpec spec, string method, PayloadAttributes attrs, string testName) =>
+                new(spec, method, attrs)
+                {
+                    TestName = testName,
+                    ExpectedResult = MergeErrorCodes.InvalidPayloadAttributes,
+                };
+
+            yield return InvalidFieldCase(Paris.Instance, nameof(IEngineRpcModule.engine_forkchoiceUpdatedV1), Attrs(mutate: a => a.Timestamp = 0), "FCUv1 Timestamp zero");
+            yield return InvalidFieldCase(Paris.Instance, nameof(IEngineRpcModule.engine_forkchoiceUpdatedV1), Attrs(mutate: a => a.PrevRandao = null), "FCUv1 PrevRandao null");
+            yield return InvalidFieldCase(Paris.Instance, nameof(IEngineRpcModule.engine_forkchoiceUpdatedV1), Attrs(mutate: a => a.SuggestedFeeRecipient = null), "FCUv1 SuggestedFeeRecipient null");
+
+            yield return InvalidFieldCase(Cancun.Instance, nameof(IEngineRpcModule.engine_forkchoiceUpdatedV3), Attrs(parentBeaconBlockRoot: Keccak.Zero), "FCUv3 Withdrawals null");
+            yield return InvalidFieldCase(Amsterdam.Instance, nameof(IEngineRpcModule.engine_forkchoiceUpdatedV4), Attrs(parentBeaconBlockRoot: Keccak.Zero, slotNumber: 1), "FCUv4 Withdrawals null");
+            yield return InvalidFieldCase(Amsterdam.Instance, nameof(IEngineRpcModule.engine_forkchoiceUpdatedV4), Attrs(withdrawals: [], slotNumber: 1), "FCUv4 ParentBeaconBlockRoot null");
+        }
+    }
+
+    [TestCaseSource(nameof(ForkchoiceUpdatedFieldValidationTestCases))]
+    public async Task<int> ForkchoiceUpdated_should_validate_payload_attributes_fields(
+        IReleaseSpec releaseSpec, string method, PayloadAttributes payloadAttributes)
+    {
+        using MergeTestBlockchain chain = await CreateBlockchain(releaseSpec: releaseSpec);
+        IEngineRpcModule rpcModule = chain.EngineRpcModule;
+        ForkchoiceStateV1 fcuState = new(chain.BlockTree.HeadHash, chain.BlockTree.HeadHash, chain.BlockTree.HeadHash);
+
+        // Set a valid timestamp relative to the chain head if test case left it non-zero
+        if (payloadAttributes.Timestamp != 0)
+            payloadAttributes.Timestamp = chain.BlockTree.Head!.Timestamp + 1;
+
+        string response = await RpcTest.TestSerializedRequest(rpcModule, method,
+            chain.JsonSerializer.Serialize(fcuState),
+            chain.JsonSerializer.Serialize(payloadAttributes));
+        JsonRpcErrorResponse errorResponse = chain.JsonSerializer.Deserialize<JsonRpcErrorResponse>(response);
+
+        return errorResponse.Error?.Code ?? ErrorCodes.None;
+    }
 }
diff --git a/src/Nethermind/Nethermind.Merge.Plugin.Test/EngineModuleTests.V2.cs b/src/Nethermind/Nethermind.Merge.Plugin.Test/EngineModuleTests.V2.cs
index e7901f566b62..8293f9e6a034 100644
--- a/src/Nethermind/Nethermind.Merge.Plugin.Test/EngineModuleTests.V2.cs
+++ b/src/Nethermind/Nethermind.Merge.Plugin.Test/EngineModuleTests.V2.cs
@@ -52,10 +52,7 @@ public virtual async Task Should_process_block_as_expected_V2(string latestValid
             safeBlockHash = startingHead.ToString(),
             finalizedBlockHash = Keccak.Zero.ToString()
         };
-        Withdrawal[] withdrawals = new[]
-        {
-            new Withdrawal { Index = 1, AmountInGwei = 3, Address = TestItem.AddressB, ValidatorIndex = 2 }
-        };
+        Withdrawal[] withdrawals = [new() { Index = 1, AmountInGwei = 3, Address = TestItem.AddressB, ValidatorIndex = 2 }];
         var payloadAttrs = new
         {
             timestamp = timestamp.ToHexString(true),
@@ -63,13 +60,10 @@ public virtual async Task Should_process_block_as_expected_V2(string latestValid
             suggestedFeeRecipient = feeRecipient.ToString(),
             withdrawals
         };
-        string?[] @params = new string?[]
-        {
-            chain.JsonSerializer.Serialize(fcuState), chain.JsonSerializer.Serialize(payloadAttrs)
-        };
+        string?[] @params = [chain.JsonSerializer.Serialize(fcuState), chain.JsonSerializer.Serialize(payloadAttrs)];
         string expectedPayloadId = payloadId;
 
-        string response = await RpcTest.TestSerializedRequest(rpc, "engine_forkchoiceUpdatedV2", @params!);
+        string response = await RpcTest.TestSerializedRequest(rpc, "engine_forkchoiceUpdatedV2", @params);
         JsonRpcSuccessResponse? successResponse = chain.JsonSerializer.Deserialize<JsonRpcSuccessResponse>(response);
 
         successResponse.Should().NotBeNull();
@@ -236,7 +230,7 @@ int ErrorCode
 
         errorResponse.Should().NotBeNull();
         errorResponse!.Error.Should().NotBeNull();
-        errorResponse!.Error!.Code.Should().Be(input.ErrorCode);
+        errorResponse!.Error!.Code.Should().Be(MergeErrorCodes.InvalidPayloadAttributes);
         errorResponse!.Error!.Message.Should().Be(string.Format(input.ErrorMessage, "PayloadAttributes"));
     }
 
@@ -336,10 +330,7 @@ public virtual async Task
         chain.AddTransactions(txs);
 
         ExecutionPayload executionPayload2 = await BuildAndSendNewBlockV2(rpc, chain, true, withdrawals);
-        Hash256[] blockHashes = new Hash256[]
-        {
-            executionPayload1.BlockHash, TestItem.KeccakA, executionPayload2.BlockHash
-        };
+        Hash256[] blockHashes = [executionPayload1.BlockHash, TestItem.KeccakA, executionPayload2.BlockHash];
         IEnumerable<ExecutionPayloadBodyV1Result?> payloadBodies =
             rpc.engine_getPayloadBodiesByHashV1(blockHashes).Data;
         ExecutionPayloadBodyV1Result?[] expected = {
@@ -432,8 +423,8 @@ public virtual async Task getPayloadBodiesByRangeV1_should_return_canonical(With
         IEngineRpcModule rpc = chain.EngineRpcModule;
         ExecutionPayload executionPayload1 = await SendNewBlockV2(rpc, chain, withdrawals);
 
-        await rpc.engine_forkchoiceUpdatedV2(new ForkchoiceStateV1(executionPayload1.BlockHash!,
-            executionPayload1.BlockHash!, executionPayload1.BlockHash!));
+        await rpc.engine_forkchoiceUpdatedV2(new ForkchoiceStateV1(executionPayload1.BlockHash,
+            executionPayload1.BlockHash!, executionPayload1.BlockHash));
 
         Block head = chain.BlockTree.Head!;
 
@@ -487,9 +478,9 @@ await rpc.engine_forkchoiceUpdatedV2(
             IEnumerable<ExecutionPayloadBodyV1Result?> payloadBodies =
                 rpc.engine_getPayloadBodiesByRangeV1(1, 3).Result.Data;
             ExecutionPayloadBodyV1Result[] expected =
-            {
+            [
                 new(Array.Empty<Transaction>(), withdrawals), new(Array.Empty<Transaction>(), withdrawals)
-            };
+            ];
 
             payloadBodies.Should().BeEquivalentTo(expected, static o => o.WithStrictOrdering());
         }
@@ -617,9 +608,9 @@ int ErrorCode
         JsonRpcErrorResponse? errorResponse = chain.JsonSerializer.Deserialize<JsonRpcErrorResponse>(response);
 
         errorResponse.Should().NotBeNull();
-        errorResponse!.Error.Should().NotBeNull();
-        errorResponse!.Error!.Code.Should().Be(input.ErrorCode);
-        errorResponse!.Error!.Message.Should().Be(string.Format(input.ErrorMessage, "ExecutionPayload"));
+        errorResponse.Error.Should().NotBeNull();
+        errorResponse.Error!.Code.Should().Be(input.ErrorCode);
+        errorResponse.Error!.Message.Should().Be(string.Format(input.ErrorMessage, "ExecutionPayload"));
     }
 
     protected static IEnumerable<(
@@ -764,8 +755,8 @@ public void Should_print_payload_attributes_as_expected()
     [TestCaseSource(nameof(PayloadIdTestCases))]
     public void Should_compute_payload_id_with_withdrawals((Withdrawal[]? Withdrawals, string PayloadId) input)
     {
-        var blockHeader = Build.A.BlockHeader.TestObject;
-        var payloadAttributes = new PayloadAttributes
+        BlockHeader blockHeader = Build.A.BlockHeader.TestObject;
+        PayloadAttributes payloadAttributes = new()
         {
             PrevRandao = Keccak.Zero,
             SuggestedFeeRecipient = Address.Zero,
@@ -773,7 +764,7 @@ public void Should_compute_payload_id_with_withdrawals((Withdrawal[]? Withdrawal
             Withdrawals = input.Withdrawals
         };
 
-        var payloadId = payloadAttributes.GetPayloadId(blockHeader);
+        string payloadId = payloadAttributes.GetPayloadId(blockHeader);
 
         payloadId.Should().Be(input.PayloadId);
     }
@@ -793,29 +784,24 @@ private static async Task<GetPayloadV2Result> BuildAndGetPayloadResultV2(
         Withdrawal[][] Withdrawals, // withdrawals per payload
         (Address, UInt256)[] expectedAccountIncrease)> WithdrawalsTestCases()
     {
-        yield return (new[] { Array.Empty<Withdrawal>() }, Array.Empty<(Address, UInt256)>());
-        yield return (new[] { new[] { TestItem.WithdrawalA_1Eth, TestItem.WithdrawalB_2Eth } },
-            new[] { (TestItem.AddressA, 1.Ether), (TestItem.AddressB, 2.Ether) });
-        yield return (new[] { new[] { TestItem.WithdrawalA_1Eth, TestItem.WithdrawalA_1Eth } },
-            new[] { (TestItem.AddressA, 2.Ether), (TestItem.AddressB, 0.Ether) });
-        yield return (
-            new[]
-            {
-                new[] { TestItem.WithdrawalA_1Eth, TestItem.WithdrawalA_1Eth }, new[] { TestItem.WithdrawalA_1Eth }
-            }, new[] { (TestItem.AddressA, 3.Ether), (TestItem.AddressB, 0.Ether) });
-        yield return (new[]
-            {
-                new[] { TestItem.WithdrawalA_1Eth, TestItem.WithdrawalA_1Eth }, // 1st payload
-                new[] { TestItem.WithdrawalA_1Eth }, // 2nd payload
+        yield return ([Array.Empty<Withdrawal>()], Array.Empty<(Address, UInt256)>());
+        yield return ([[TestItem.WithdrawalA_1Eth, TestItem.WithdrawalB_2Eth]],
+            [(TestItem.AddressA, 1.Ether), (TestItem.AddressB, 2.Ether)]);
+        yield return ([[TestItem.WithdrawalA_1Eth, TestItem.WithdrawalA_1Eth]],
+            [(TestItem.AddressA, 2.Ether), (TestItem.AddressB, 0.Ether)]);
+        yield return ([[TestItem.WithdrawalA_1Eth, TestItem.WithdrawalA_1Eth], [TestItem.WithdrawalA_1Eth]],
+            [(TestItem.AddressA, 3.Ether), (TestItem.AddressB, 0.Ether)]);
+        yield return ([
+                [TestItem.WithdrawalA_1Eth, TestItem.WithdrawalA_1Eth], // 1st payload
+                [TestItem.WithdrawalA_1Eth], // 2nd payload
                 [], // 3rd payload
-                new[] { TestItem.WithdrawalA_1Eth, TestItem.WithdrawalC_3Eth }, // 4th payload
-                new[] { TestItem.WithdrawalB_2Eth, TestItem.WithdrawalF_6Eth }, // 5th payload
-            },
-            new[]
-            {
+                [TestItem.WithdrawalA_1Eth, TestItem.WithdrawalC_3Eth], // 4th payload
+                [TestItem.WithdrawalB_2Eth, TestItem.WithdrawalF_6Eth] // 5th payload
+            ],
+            [
                 (TestItem.AddressA, 4.Ether), (TestItem.AddressB, 2.Ether), (TestItem.AddressC, 3.Ether),
                 (TestItem.AddressF, 6.Ether)
-            });
+            ]);
     }
 
     protected static IEnumerable<IList<Withdrawal>> GetPayloadWithdrawalsTestCases()
@@ -842,8 +828,8 @@ private async Task<ExecutionPayload> BuildAndGetPayloadResultV2(
             ? chain.WaitForImprovedBlock()
             : Task.CompletedTask;
 
-        ForkchoiceStateV1 forkchoiceState = new ForkchoiceStateV1(headBlockHash, finalizedBlockHash, safeBlockHash);
-        PayloadAttributes payloadAttributes = new PayloadAttributes
+        ForkchoiceStateV1 forkchoiceState = new(headBlockHash, finalizedBlockHash, safeBlockHash);
+        PayloadAttributes payloadAttributes = new()
         {
             Timestamp = timestamp,
             PrevRandao = random,
@@ -911,17 +897,17 @@ bool isValid
         ExecutionPayloadBodyV1Result result = new ExecutionPayloadBodyV1Result(Array.Empty<Transaction>(), null);
 
         yield return (
-            new Func<CallInfo, Block?>(i => null),
+            _ => null,
             new ExecutionPayloadBodyV1Result?[] { null, null, null, null, null }
         );
 
         yield return (
-            new Func<CallInfo, Block?>(i => i.ArgAt<long>(0) % 2 == 0 ? block : null),
+            i => i.ArgAt<long>(0) % 2 == 0 ? block : null,
             new[] { null, result, null, result, null }
         );
 
         yield return (
-            new Func<CallInfo, Block?>(i => block),
+            _ => block,
             Enumerable.Repeat(result, 5)
         );
     }
@@ -933,6 +919,6 @@ string payloadId
     {
         yield return (null, "0xe3b6f7433feedc38");
         yield return (Array.Empty<Withdrawal>(), "0xf74921b673b2e08e");
-        yield return (new[] { Build.A.Withdrawal.TestObject }, "0xe0d0b996245ec3a6");
+        yield return ([Build.A.Withdrawal.TestObject], "0xe0d0b996245ec3a6");
     }
 }
diff --git a/src/Nethermind/Nethermind.Merge.Plugin/BlockProduction/Boost/BoostBlockImprovementContext.cs b/src/Nethermind/Nethermind.Merge.Plugin/BlockProduction/Boost/BoostBlockImprovementContext.cs
index 8b0b0c17a3d4..efda516a9a19 100644
--- a/src/Nethermind/Nethermind.Merge.Plugin/BlockProduction/Boost/BoostBlockImprovementContext.cs
+++ b/src/Nethermind/Nethermind.Merge.Plugin/BlockProduction/Boost/BoostBlockImprovementContext.cs
@@ -52,14 +52,15 @@ public BoostBlockImprovementContext(Block currentBestBlock,
     {
 
         payloadAttributes = await _boostRelay.GetPayloadAttributes(payloadAttributes, cancellationToken);
-        _stateReader.TryGetAccount(parentHeader, payloadAttributes.SuggestedFeeRecipient, out AccountStruct account);
+        Address feeRecipient = payloadAttributes.SuggestedFeeRecipient!;
+        _stateReader.TryGetAccount(parentHeader, feeRecipient, out AccountStruct account);
         UInt256 balanceBefore = account.Balance;
         Block? block = await blockProducer.BuildBlock(parentHeader, _feesTracer, payloadAttributes, IBlockProducer.Flags.None, cancellationToken);
         if (block is not null)
         {
             CurrentBestBlock = block;
             BlockFees = _feesTracer.Fees;
-            _stateReader.TryGetAccount(parentHeader, payloadAttributes.SuggestedFeeRecipient, out account);
+            _stateReader.TryGetAccount(parentHeader, feeRecipient, out account);
             await _boostRelay.SendPayload(new BoostExecutionPayloadV1 { Block = ExecutionPayload.Create(block), Profit = account.Balance - balanceBefore }, cancellationToken);
         }
 
diff --git a/src/Nethermind/Nethermind.Merge.Plugin/EngineRpcModule.Amsterdam.cs b/src/Nethermind/Nethermind.Merge.Plugin/EngineRpcModule.Amsterdam.cs
index 596152acb695..c6888d93786e 100644
--- a/src/Nethermind/Nethermind.Merge.Plugin/EngineRpcModule.Amsterdam.cs
+++ b/src/Nethermind/Nethermind.Merge.Plugin/EngineRpcModule.Amsterdam.cs
@@ -22,10 +22,10 @@ public partial class EngineRpcModule : IEngineRpcModule
         => _getPayloadHandlerV6.HandleAsync(payloadId);
 
     public Task<ResultWrapper<PayloadStatusV1>> engine_newPayloadV5(ExecutionPayloadV4 executionPayload, byte[]?[] blobVersionedHashes, Hash256? parentBeaconBlockRoot, byte[][]? executionRequests)
-        => NewPayload(new ExecutionPayloadParams<ExecutionPayloadV4>(executionPayload, blobVersionedHashes, parentBeaconBlockRoot, executionRequests), EngineApiVersions.Amsterdam);
+        => NewPayload(new ExecutionPayloadParams<ExecutionPayloadV4>(executionPayload, blobVersionedHashes, parentBeaconBlockRoot, executionRequests), EngineApiVersions.NewPayload.V5);
 
     public Task<ResultWrapper<ForkchoiceUpdatedV1Result>> engine_forkchoiceUpdatedV4(ForkchoiceStateV1 forkchoiceState, PayloadAttributes? payloadAttributes = null)
-        => ForkchoiceUpdated(forkchoiceState, payloadAttributes, EngineApiVersions.Amsterdam);
+        => ForkchoiceUpdated(forkchoiceState, payloadAttributes, EngineApiVersions.Fcu.V4);
 
     public Task<ResultWrapper<IEnumerable<ExecutionPayloadBodyV2Result?>>> engine_getPayloadBodiesByHashV2(IReadOnlyList<Hash256> blockHashes)
         => _executionGetPayloadBodiesByHashV2Handler.Handle(blockHashes);
diff --git a/src/Nethermind/Nethermind.Merge.Plugin/EngineRpcModule.Cancun.cs b/src/Nethermind/Nethermind.Merge.Plugin/EngineRpcModule.Cancun.cs
index b0744d25363d..042ca510fe81 100644
--- a/src/Nethermind/Nethermind.Merge.Plugin/EngineRpcModule.Cancun.cs
+++ b/src/Nethermind/Nethermind.Merge.Plugin/EngineRpcModule.Cancun.cs
@@ -18,10 +18,10 @@ public partial class EngineRpcModule : IEngineRpcModule
     private readonly IAsyncHandler<byte[][], IEnumerable<BlobAndProofV1?>> _getBlobsHandler;
 
     public Task<ResultWrapper<ForkchoiceUpdatedV1Result>> engine_forkchoiceUpdatedV3(ForkchoiceStateV1 forkchoiceState, PayloadAttributes? payloadAttributes = null)
-        => ForkchoiceUpdated(forkchoiceState, payloadAttributes, EngineApiVersions.Cancun);
+        => ForkchoiceUpdated(forkchoiceState, payloadAttributes, EngineApiVersions.Fcu.V3);
 
     public Task<ResultWrapper<PayloadStatusV1>> engine_newPayloadV3(ExecutionPayloadV3 executionPayload, byte[]?[] blobVersionedHashes, Hash256? parentBeaconBlockRoot) =>
-        NewPayload(new ExecutionPayloadParams<ExecutionPayloadV3>(executionPayload, blobVersionedHashes, parentBeaconBlockRoot), EngineApiVersions.Cancun);
+        NewPayload(new ExecutionPayloadParams<ExecutionPayloadV3>(executionPayload, blobVersionedHashes, parentBeaconBlockRoot), EngineApiVersions.NewPayload.V3);
 
     public Task<ResultWrapper<GetPayloadV3Result?>> engine_getPayloadV3(byte[] payloadId) =>
         _getPayloadHandlerV3.HandleAsync(payloadId);
diff --git a/src/Nethermind/Nethermind.Merge.Plugin/EngineRpcModule.Paris.cs b/src/Nethermind/Nethermind.Merge.Plugin/EngineRpcModule.Paris.cs
index c3bcea2649c5..3d6c1e7789d2 100644
--- a/src/Nethermind/Nethermind.Merge.Plugin/EngineRpcModule.Paris.cs
+++ b/src/Nethermind/Nethermind.Merge.Plugin/EngineRpcModule.Paris.cs
@@ -33,13 +33,13 @@ public ResultWrapper<TransitionConfigurationV1> engine_exchangeTransitionConfigu
         TransitionConfigurationV1 beaconTransitionConfiguration) => _transitionConfigurationHandler.Handle(beaconTransitionConfiguration);
 
     public Task<ResultWrapper<ForkchoiceUpdatedV1Result>> engine_forkchoiceUpdatedV1(ForkchoiceStateV1 forkchoiceState, PayloadAttributes? payloadAttributes = null)
-        => ForkchoiceUpdated(forkchoiceState, payloadAttributes, EngineApiVersions.Paris);
+        => ForkchoiceUpdated(forkchoiceState, payloadAttributes, EngineApiVersions.Fcu.V1);
 
     public Task<ResultWrapper<ExecutionPayload?>> engine_getPayloadV1(byte[] payloadId) =>
         _getPayloadHandlerV1.HandleAsync(payloadId);
 
     public Task<ResultWrapper<PayloadStatusV1>> engine_newPayloadV1(ExecutionPayload executionPayload)
-        => NewPayload(executionPayload, EngineApiVersions.Paris);
+        => NewPayload(executionPayload, EngineApiVersions.NewPayload.V1);
 
     protected async Task<ResultWrapper<ForkchoiceUpdatedV1Result>> ForkchoiceUpdated(ForkchoiceStateV1 forkchoiceState, PayloadAttributes? payloadAttributes, int version)
     {
@@ -73,7 +73,7 @@ protected async Task<ResultWrapper<PayloadStatusV1>> NewPayload(IExecutionPayloa
         if (!executionPayload.ValidateFork(_specProvider))
         {
             if (_logger.IsWarn) _logger.Warn($"The payload is not supported by the current fork");
-            return ResultWrapper<PayloadStatusV1>.Fail(MergeErrorMessages.UnsupportedFork, version < EngineApiVersions.Shanghai ? ErrorCodes.InvalidParams : MergeErrorCodes.UnsupportedFork);
+            return ResultWrapper<PayloadStatusV1>.Fail(MergeErrorMessages.UnsupportedFork, version < EngineApiVersions.NewPayload.V2 ? ErrorCodes.InvalidParams : MergeErrorCodes.UnsupportedFork);
         }
 
         IReleaseSpec releaseSpec = _specProvider.GetSpec(executionPayload.BlockNumber, executionPayload.Timestamp);
diff --git a/src/Nethermind/Nethermind.Merge.Plugin/EngineRpcModule.Prague.cs b/src/Nethermind/Nethermind.Merge.Plugin/EngineRpcModule.Prague.cs
index c72cccbb3ab1..800abf14ca01 100644
--- a/src/Nethermind/Nethermind.Merge.Plugin/EngineRpcModule.Prague.cs
+++ b/src/Nethermind/Nethermind.Merge.Plugin/EngineRpcModule.Prague.cs
@@ -19,7 +19,7 @@ public partial class EngineRpcModule : IEngineRpcModule
     /// <see href="https://eips.ethereum.org/EIPS/eip-7685">EIP-7685</see>.
     /// </summary>
     public Task<ResultWrapper<PayloadStatusV1>> engine_newPayloadV4(ExecutionPayloadV3 executionPayload, byte[]?[] blobVersionedHashes, Hash256? parentBeaconBlockRoot, byte[][]? executionRequests)
-        => NewPayload(new ExecutionPayloadParams<ExecutionPayloadV3>(executionPayload, blobVersionedHashes, parentBeaconBlockRoot, executionRequests), EngineApiVersions.Prague);
+        => NewPayload(new ExecutionPayloadParams<ExecutionPayloadV3>(executionPayload, blobVersionedHashes, parentBeaconBlockRoot, executionRequests), EngineApiVersions.NewPayload.V4);
 
     public Task<ResultWrapper<GetPayloadV4Result?>> engine_getPayloadV4(byte[] payloadId)
         => _getPayloadHandlerV4.HandleAsync(payloadId);
diff --git a/src/Nethermind/Nethermind.Merge.Plugin/EngineRpcModule.Shanghai.cs b/src/Nethermind/Nethermind.Merge.Plugin/EngineRpcModule.Shanghai.cs
index 0b435dc1172b..2625b2243e9b 100644
--- a/src/Nethermind/Nethermind.Merge.Plugin/EngineRpcModule.Shanghai.cs
+++ b/src/Nethermind/Nethermind.Merge.Plugin/EngineRpcModule.Shanghai.cs
@@ -19,7 +19,7 @@ public partial class EngineRpcModule : IEngineRpcModule
     private readonly IAsyncHandler<byte[], GetPayloadV2Result?> _getPayloadHandlerV2;
 
     public Task<ResultWrapper<ForkchoiceUpdatedV1Result>> engine_forkchoiceUpdatedV2(ForkchoiceStateV1 forkchoiceState, PayloadAttributes? payloadAttributes = null)
-        => ForkchoiceUpdated(forkchoiceState, payloadAttributes, EngineApiVersions.Shanghai);
+        => ForkchoiceUpdated(forkchoiceState, payloadAttributes, EngineApiVersions.Fcu.V2);
 
     public Task<ResultWrapper<GetPayloadV2Result?>> engine_getPayloadV2(byte[] payloadId)
         => _getPayloadHandlerV2.HandleAsync(payloadId);
@@ -31,5 +31,5 @@ public Task<ResultWrapper<ForkchoiceUpdatedV1Result>> engine_forkchoiceUpdatedV2
         => _executionGetPayloadBodiesByRangeV1Handler.Handle(start, count);
 
     public Task<ResultWrapper<PayloadStatusV1>> engine_newPayloadV2(ExecutionPayload executionPayload)
-        => NewPayload(executionPayload, EngineApiVersions.Shanghai);
+        => NewPayload(executionPayload, EngineApiVersions.NewPayload.V2);
 }
diff --git a/src/Nethermind/Nethermind.Merge.Plugin/Handlers/ForkchoiceUpdatedHandler.cs b/src/Nethermind/Nethermind.Merge.Plugin/Handlers/ForkchoiceUpdatedHandler.cs
index 1cd7ce507b99..aba6ba96d1f1 100644
--- a/src/Nethermind/Nethermind.Merge.Plugin/Handlers/ForkchoiceUpdatedHandler.cs
+++ b/src/Nethermind/Nethermind.Merge.Plugin/Handlers/ForkchoiceUpdatedHandler.cs
@@ -338,8 +338,6 @@ private ResultWrapper<ForkchoiceUpdatedV1Result> StartBuildingPayload(Block newH
         string? error = null;
         return payloadAttributes?.Validate(_specProvider, version, out error) switch
         {
-            PayloadAttributesValidationResult.InvalidParams =>
-                ResultWrapper<ForkchoiceUpdatedV1Result>.Fail(error!, ErrorCodes.InvalidParams),
             PayloadAttributesValidationResult.InvalidPayloadAttributes =>
                 ResultWrapper<ForkchoiceUpdatedV1Result>.Fail(error!, MergeErrorCodes.InvalidPayloadAttributes),
             PayloadAttributesValidationResult.UnsupportedFork =>
diff --git a/src/Nethermind/Nethermind.Merge.Plugin/Handlers/GetPayloadV1Handler.cs b/src/Nethermind/Nethermind.Merge.Plugin/Handlers/GetPayloadV1Handler.cs
index 4c2a3ad5719e..8b169cf72b40 100644
--- a/src/Nethermind/Nethermind.Merge.Plugin/Handlers/GetPayloadV1Handler.cs
+++ b/src/Nethermind/Nethermind.Merge.Plugin/Handlers/GetPayloadV1Handler.cs
@@ -1,6 +1,7 @@
 // SPDX-FileCopyrightText: 2022 Demerzel Solutions Limited
 // SPDX-License-Identifier: LGPL-3.0-only
 
+using Nethermind.Consensus;
 using Nethermind.Consensus.Producers;
 using Nethermind.Core.Specs;
 using Nethermind.Logging;
@@ -25,7 +26,7 @@ namespace Nethermind.Merge.Plugin.Handlers;
 /// Execution client may stop the building process with the corresponding payload_id value after serving this call.
 /// </remarks>
 public class GetPayloadV1Handler(IPayloadPreparationService payloadPreparationService, ISpecProvider specProvider, ILogManager logManager)
-    : GetPayloadHandlerBase<ExecutionPayload>(1, payloadPreparationService, specProvider, logManager)
+    : GetPayloadHandlerBase<ExecutionPayload>(EngineApiVersions.GetPayload.V1, payloadPreparationService, specProvider, logManager)
 {
     protected override ExecutionPayload GetPayloadResultFromBlock(IBlockProductionContext context) =>
         ExecutionPayload.Create(context.CurrentBestBlock!);
diff --git a/src/Nethermind/Nethermind.Merge.Plugin/Handlers/GetPayloadV2Handler.cs b/src/Nethermind/Nethermind.Merge.Plugin/Handlers/GetPayloadV2Handler.cs
index 49eaad78a0d1..739d39e56ef4 100644
--- a/src/Nethermind/Nethermind.Merge.Plugin/Handlers/GetPayloadV2Handler.cs
+++ b/src/Nethermind/Nethermind.Merge.Plugin/Handlers/GetPayloadV2Handler.cs
@@ -1,6 +1,7 @@
 // SPDX-FileCopyrightText: 2022 Demerzel Solutions Limited
 // SPDX-License-Identifier: LGPL-3.0-only
 
+using Nethermind.Consensus;
 using Nethermind.Consensus.Producers;
 using Nethermind.Core.Specs;
 using Nethermind.Logging;
@@ -17,7 +18,7 @@ public class GetPayloadV2Handler(
     IPayloadPreparationService payloadPreparationService,
     ISpecProvider specProvider,
     ILogManager logManager)
-    : GetPayloadHandlerBase<GetPayloadV2Result>(2, payloadPreparationService, specProvider, logManager)
+    : GetPayloadHandlerBase<GetPayloadV2Result>(EngineApiVersions.GetPayload.V2, payloadPreparationService, specProvider, logManager)
 {
     protected override GetPayloadV2Result GetPayloadResultFromBlock(IBlockProductionContext context) =>
         new(context.CurrentBestBlock!, context.BlockFees);
diff --git a/src/Nethermind/Nethermind.Merge.Plugin/Handlers/GetPayloadV3Handler.cs b/src/Nethermind/Nethermind.Merge.Plugin/Handlers/GetPayloadV3Handler.cs
index 8c1eed935237..9146a7dbeec1 100644
--- a/src/Nethermind/Nethermind.Merge.Plugin/Handlers/GetPayloadV3Handler.cs
+++ b/src/Nethermind/Nethermind.Merge.Plugin/Handlers/GetPayloadV3Handler.cs
@@ -1,6 +1,7 @@
 // SPDX-FileCopyrightText: 2025 Demerzel Solutions Limited
 // SPDX-License-Identifier: LGPL-3.0-only
 
+using Nethermind.Consensus;
 using Nethermind.Consensus.Producers;
 using Nethermind.Core.Specs;
 using Nethermind.Logging;
@@ -19,7 +20,7 @@ public class GetPayloadV3Handler(
     ISpecProvider specProvider,
     ILogManager logManager,
     ICensorshipDetector? censorshipDetector = null)
-    : GetPayloadHandlerBase<GetPayloadV3Result>(3, payloadPreparationService, specProvider, logManager, censorshipDetector)
+    : GetPayloadHandlerBase<GetPayloadV3Result>(EngineApiVersions.GetPayload.V3, payloadPreparationService, specProvider, logManager, censorshipDetector)
 {
     protected override GetPayloadV3Result GetPayloadResultFromBlock(IBlockProductionContext context)
     {
diff --git a/src/Nethermind/Nethermind.Merge.Plugin/Handlers/GetPayloadV4Handler.cs b/src/Nethermind/Nethermind.Merge.Plugin/Handlers/GetPayloadV4Handler.cs
index 93bb06d48365..7bc639ab3f1e 100644
--- a/src/Nethermind/Nethermind.Merge.Plugin/Handlers/GetPayloadV4Handler.cs
+++ b/src/Nethermind/Nethermind.Merge.Plugin/Handlers/GetPayloadV4Handler.cs
@@ -1,6 +1,7 @@
 // SPDX-FileCopyrightText: 2025 Demerzel Solutions Limited
 // SPDX-License-Identifier: LGPL-3.0-only
 
+using Nethermind.Consensus;
 using Nethermind.Core.Specs;
 using Nethermind.Logging;
 using Nethermind.Merge.Plugin.BlockProduction;
@@ -19,7 +20,7 @@ public class GetPayloadV4Handler(
     ISpecProvider specProvider,
     ILogManager logManager,
     ICensorshipDetector? censorshipDetector = null)
-    : GetPayloadHandlerBase<GetPayloadV4Result>(4, payloadPreparationService, specProvider, logManager, censorshipDetector)
+    : GetPayloadHandlerBase<GetPayloadV4Result>(EngineApiVersions.GetPayload.V4, payloadPreparationService, specProvider, logManager, censorshipDetector)
 {
     protected override GetPayloadV4Result GetPayloadResultFromBlock(IBlockProductionContext context)
     {
diff --git a/src/Nethermind/Nethermind.Merge.Plugin/Handlers/GetPayloadV5Handler.cs b/src/Nethermind/Nethermind.Merge.Plugin/Handlers/GetPayloadV5Handler.cs
index 656de8ccb6f5..7abb35cce5c6 100644
--- a/src/Nethermind/Nethermind.Merge.Plugin/Handlers/GetPayloadV5Handler.cs
+++ b/src/Nethermind/Nethermind.Merge.Plugin/Handlers/GetPayloadV5Handler.cs
@@ -1,6 +1,7 @@
 // SPDX-FileCopyrightText: 2025 Demerzel Solutions Limited
 // SPDX-License-Identifier: LGPL-3.0-only
 
+using Nethermind.Consensus;
 using Nethermind.Core.Specs;
 using Nethermind.Logging;
 using Nethermind.Merge.Plugin.BlockProduction;
@@ -19,7 +20,7 @@ public class GetPayloadV5Handler(
     ISpecProvider specProvider,
     ILogManager logManager,
     ICensorshipDetector? censorshipDetector = null)
-    : GetPayloadHandlerBase<GetPayloadV5Result>(5, payloadPreparationService, specProvider, logManager, censorshipDetector)
+    : GetPayloadHandlerBase<GetPayloadV5Result>(EngineApiVersions.GetPayload.V5, payloadPreparationService, specProvider, logManager, censorshipDetector)
 {
     protected override GetPayloadV5Result GetPayloadResultFromBlock(IBlockProductionContext context)
     {
diff --git a/src/Nethermind/Nethermind.Merge.Plugin/Handlers/GetPayloadV6Handler.cs b/src/Nethermind/Nethermind.Merge.Plugin/Handlers/GetPayloadV6Handler.cs
index 9c5080d54e42..97d75fe6dbab 100644
--- a/src/Nethermind/Nethermind.Merge.Plugin/Handlers/GetPayloadV6Handler.cs
+++ b/src/Nethermind/Nethermind.Merge.Plugin/Handlers/GetPayloadV6Handler.cs
@@ -1,6 +1,7 @@
 // SPDX-FileCopyrightText: 2026 Demerzel Solutions Limited
 // SPDX-License-Identifier: LGPL-3.0-only
 
+using Nethermind.Consensus;
 using Nethermind.Core.Specs;
 using Nethermind.Logging;
 using Nethermind.Merge.Plugin.BlockProduction;
@@ -19,7 +20,7 @@ public class GetPayloadV6Handler(
     ISpecProvider specProvider,
     ILogManager logManager,
     ICensorshipDetector? censorshipDetector = null)
-    : GetPayloadHandlerBase<GetPayloadV6Result>(6, payloadPreparationService, specProvider, logManager, censorshipDetector)
+    : GetPayloadHandlerBase<GetPayloadV6Result>(EngineApiVersions.GetPayload.V6, payloadPreparationService, specProvider, logManager, censorshipDetector)
 {
     protected override GetPayloadV6Result GetPayloadResultFromBlock(IBlockProductionContext context)
     {
diff --git a/src/Nethermind/Nethermind.Optimism.Test/OptimismPayloadAttributesTests.cs b/src/Nethermind/Nethermind.Optimism.Test/OptimismPayloadAttributesTests.cs
index d977fc69de39..4292e0aaf0c0 100644
--- a/src/Nethermind/Nethermind.Optimism.Test/OptimismPayloadAttributesTests.cs
+++ b/src/Nethermind/Nethermind.Optimism.Test/OptimismPayloadAttributesTests.cs
@@ -81,7 +81,7 @@ public void Validate_EIP1559Params(
         ISpecProvider spec = Spec.BuildFor(fork.Timestamp);
 
         Assert.That(
-            payloadAttributes.Validate(spec, EngineApiVersions.Cancun, out var error),
+            payloadAttributes.Validate(spec, EngineApiVersions.Fcu.V3, out var error),
             testCase.isValid.On(fork.Timestamp)
                 ? Is.EqualTo(PayloadAttributesValidationResult.Success)
                 : Is.EqualTo(PayloadAttributesValidationResult.InvalidPayloadAttributes),
diff --git a/src/Nethermind/Nethermind.Optimism/Rpc/OptimismPayloadAttributes.cs b/src/Nethermind/Nethermind.Optimism/Rpc/OptimismPayloadAttributes.cs
index 9d504265c987..bb646350e25e 100644
--- a/src/Nethermind/Nethermind.Optimism/Rpc/OptimismPayloadAttributes.cs
+++ b/src/Nethermind/Nethermind.Optimism/Rpc/OptimismPayloadAttributes.cs
@@ -105,7 +105,7 @@ protected override int WritePayloadIdMembers(BlockHeader parentHeader, Span<byte
         return offset;
     }
 
-    public override PayloadAttributesValidationResult Validate(ISpecProvider specProvider, int apiVersion,
+    public override PayloadAttributesValidationResult Validate(ISpecProvider specProvider, int fcuVersion,
         [NotNullWhen(false)] out string? error)
     {
         if (GasLimit == 0)
@@ -150,7 +150,7 @@ public override PayloadAttributesValidationResult Validate(ISpecProvider specPro
             error = $"Error decoding transactions: {e}";
             return PayloadAttributesValidationResult.InvalidPayloadAttributes;
         }
-        return base.Validate(specProvider, apiVersion, out error);
+        return base.Validate(specProvider, fcuVersion, out error);
     }
 
     public override string ToString()
diff --git a/src/Nethermind/Nethermind.Taiko/TaikoPayloadAttributes.cs b/src/Nethermind/Nethermind.Taiko/TaikoPayloadAttributes.cs
index 671e09b59f10..77b57515ffdf 100644
--- a/src/Nethermind/Nethermind.Taiko/TaikoPayloadAttributes.cs
+++ b/src/Nethermind/Nethermind.Taiko/TaikoPayloadAttributes.cs
@@ -19,7 +19,7 @@ public class TaikoPayloadAttributes : PayloadAttributes
         return BlockMetadata!.GasLimit;
     }
 
-    public override PayloadAttributesValidationResult Validate(ISpecProvider specProvider, int apiVersion,
+    public override PayloadAttributesValidationResult Validate(ISpecProvider specProvider, int fcuVersion,
         [NotNullWhen(false)] out string? error)
     {
         if (L1Origin is null)
@@ -55,7 +55,7 @@ public override PayloadAttributesValidationResult Validate(ISpecProvider specPro
             return PayloadAttributesValidationResult.InvalidPayloadAttributes;
         }
 
-        return base.Validate(specProvider, apiVersion, out error);
+        return base.Validate(specProvider, fcuVersion, out error);
     }
 
 }