fix(engine-api): add engine_appendBatchSignature RPC for sync nodes

README.md

@@ -200,6 +200,7 @@ Morph provides a custom L2 Engine API (different from the standard Ethereum Engi
 | `engine_newL2Block` | Import a new L2 block via `newPayload` + `forkchoiceUpdated` and advance the canonical head |
 | `engine_newSafeL2Block` | Rebuild and import a safe L2 block from derivation inputs |
 | `engine_setBlockTags` | Update safe/finalized block tags without importing a block |
+| `engine_appendBatchSignature` | Accept a BLS batch signature from the consensus layer (no-op for sync nodes) |
 
 ## Contributing
 

crates/engine-api/src/api.rs

@@ -6,7 +6,9 @@
 
 use crate::EngineApiResult;
 use alloy_primitives::B256;
-use morph_payload_types::{AssembleL2BlockParams, ExecutableL2Data, GenericResponse, SafeL2Data};
+use morph_payload_types::{
+    AssembleL2BlockParams, BatchSignature, ExecutableL2Data, GenericResponse, SafeL2Data,
+};
 use morph_primitives::MorphHeader;
 
 /// Morph L2 Engine API trait.
@@ -107,4 +109,16 @@ pub trait MorphL2EngineApi: Send + Sync {
         safe_block_hash: B256,
         finalized_block_hash: B256,
     ) -> EngineApiResult<()>;
+
+    /// Append a BLS batch signature for a given batch hash.
+    ///
+    /// Called by the consensus layer when collecting validator signatures for
+    /// L1 batch submission. For non-sequencer sync nodes, this is a no-op.
+    async fn append_batch_signature(
+        &self,
+        _batch_hash: B256,
+        _signature: BatchSignature,
+    ) -> EngineApiResult<()> {
+        Ok(())
+    }
 }

crates/engine-api/src/rpc.rs

@@ -6,7 +6,9 @@
 use crate::{EngineApiResult, api::MorphL2EngineApi};
 use alloy_primitives::B256;
 use jsonrpsee::{RpcModule, core::RpcResult, proc_macros::rpc};
-use morph_payload_types::{AssembleL2BlockParams, ExecutableL2Data, GenericResponse, SafeL2Data};
+use morph_payload_types::{
+    AssembleL2BlockParams, BatchSignature, ExecutableL2Data, GenericResponse, SafeL2Data,
+};
 use morph_primitives::MorphHeader;
 use reth_rpc_api::IntoEngineApiRpcModule;
 use std::sync::Arc;
@@ -61,6 +63,22 @@ pub trait MorphL2EngineRpc {
         safe_block_hash: B256,
         finalized_block_hash: B256,
     ) -> RpcResult<()>;
+
+    /// Append a BLS batch signature for a given batch hash.
+    ///
+    /// Called by the consensus layer when collecting validator signatures for
+    /// L1 batch submission. Non-sequencer sync nodes accept this call but do
+    /// not persist the signature.
+    ///
+    /// # JSON-RPC Method
+    ///
+    /// `engine_appendBatchSignature`
+    #[method(name = "appendBatchSignature")]
+    async fn append_batch_signature(
+        &self,
+        batch_hash: B256,
+        signature: BatchSignature,
+    ) -> RpcResult<()>;
 }
 
 /// Implementation of the L2 Engine RPC API.
@@ -164,6 +182,25 @@ where
                 e.into()
             })
     }
+
+    async fn append_batch_signature(
+        &self,
+        batch_hash: B256,
+        _signature: BatchSignature,
+    ) -> RpcResult<()> {
+        tracing::debug!(
+            target: "morph::engine",
+            %batch_hash,
+            "RPC appendBatchSignature called (no-op for sync node)"
+        );
+        self.inner
+            .append_batch_signature(batch_hash, _signature)
+            .await
+            .map_err(|e| {
+                tracing::error!(target: "morph::engine", error = %e, "failed to append batch signature");
+                e.into()
+            })
+    }
 }
 
 /// Converts an `EngineApiResult` into a `RpcResult`.

crates/payload/types/src/lib.rs

@@ -35,7 +35,7 @@ use reth_ethereum_primitives as _;
 pub use attributes::{MorphPayloadAttributes, MorphPayloadBuilderAttributes};
 pub use built::MorphBuiltPayload;
 pub use executable_l2_data::ExecutableL2Data;
-pub use params::{AssembleL2BlockParams, GenericResponse};
+pub use params::{AssembleL2BlockParams, BatchSignature, GenericResponse};
 pub use safe_l2_data::SafeL2Data;
 
 // =============================================================================

crates/payload/types/src/params.rs

@@ -1,6 +1,6 @@
 //! Request/response types for L2 Engine API methods.
 
-use alloy_primitives::Bytes;
+use alloy_primitives::{Address, Bytes};
 
 /// Parameters for engine_assembleL2Block.
 ///
@@ -70,6 +70,22 @@ impl GenericResponse {
     }
 }
 
+/// BLS batch signature from a sequencer validator.
+///
+/// This is sent by the consensus layer via `engine_appendBatchSignature`
+/// when collecting validator signatures for L1 batch submission.
+/// For non-sequencer nodes this is accepted but not persisted.
+#[derive(Debug, Clone, Default, PartialEq, Eq, serde::Serialize, serde::Deserialize)]
+#[serde(rename_all = "camelCase")]
+pub struct BatchSignature {
+    /// Validator address that produced the signature.
+    pub signer: Address,
+    /// BLS public key of the signer.
+    pub signer_pub_key: Bytes,
+    /// BLS signature over the batch hash.
+    pub signature: Bytes,
+}
+
 impl From<bool> for GenericResponse {
     fn from(success: bool) -> Self {
         Self { success }