sigp · romeoscript · Feb 13, 2026 · Feb 13, 2026 · Feb 16, 2026 · Feb 19, 2026
diff --git a/beacon_node/http_api/src/beacon/states.rs b/beacon_node/http_api/src/beacon/states.rs
@@ -3,17 +3,20 @@ use crate::task_spawner::{Priority, TaskSpawner};
 use crate::utils::ResponseFilter;
 use crate::validator::pubkey_to_validator_index;
 use crate::version::{
-    ResponseIncludesVersion, add_consensus_version_header,
+    ResponseIncludesVersion, add_consensus_version_header, add_ssz_content_type_header,
     execution_optimistic_finalized_beacon_response,
 };
 use beacon_chain::{BeaconChain, BeaconChainError, BeaconChainTypes, WhenSlotSkipped};
 use eth2::types::{
     ValidatorBalancesRequestBody, ValidatorId, ValidatorIdentitiesRequestBody,
     ValidatorsRequestBody,
 };
+use ssz::Encode;
 use std::sync::Arc;
 use types::{AttestationShufflingId, BeaconStateError, CommitteeCache, EthSpec, RelativeEpoch};
 use warp::filters::BoxedFilter;
+use warp::http::Response;
+use warp::hyper::Body;
 use warp::{Filter, Reply};
 use warp_utils::query::multi_key_query;
 
@@ -68,6 +71,67 @@ pub fn get_beacon_state_pending_consolidations<T: BeaconChainTypes>(
         .boxed()
 }
 
+// GET beacon/states/{state_id}/proposer_lookahead
+pub fn get_beacon_state_proposer_lookahead<T: BeaconChainTypes>(
+    beacon_states_path: BeaconStatesPath<T>,
+) -> ResponseFilter {
+    beacon_states_path
+        .clone()
+        .and(warp::path("proposer_lookahead"))
+        .and(warp::path::end())
+        .and(warp::header::optional::<eth2::types::Accept>("accept"))
+        .then(
+            |state_id: StateId,
+             task_spawner: TaskSpawner<T::EthSpec>,
+             chain: Arc<BeaconChain<T>>,
+             accept_header: Option<eth2::types::Accept>| {
+                task_spawner.blocking_response_task(Priority::P1, move || {
+                    let (data, execution_optimistic, finalized, fork_name) = state_id
+                        .map_state_and_execution_optimistic_and_finalized(
+                            &chain,
+                            |state, execution_optimistic, finalized| {
+                                let Ok(lookahead) = state.proposer_lookahead() else {
+                                    return Err(warp_utils::reject::custom_bad_request(
+                                        "Proposer lookahead is not available for pre-Fulu states"
+                                            .to_string(),
+                                    ));
+                                };
+
+                                Ok((
+                                    lookahead.to_vec(),
+                                    execution_optimistic,
+                                    finalized,
+                                    state.fork_name_unchecked(),
+                                ))
+                            },
+                        )?;
+
+                    match accept_header {
+                        Some(eth2::types::Accept::Ssz) => Response::builder()
+                            .status(200)
+                            .body(data.as_ssz_bytes().into())
+                            .map(|res: Response<Body>| add_ssz_content_type_header(res))
+                            .map_err(|e| {
+                                warp_utils::reject::custom_server_error(format!(
+                                    "failed to create response: {}",
+                                    e
+                                ))
+                            }),
+                        _ => execution_optimistic_finalized_beacon_response(
+                            ResponseIncludesVersion::Yes(fork_name),
+                            execution_optimistic,
+                            finalized,
+                            data,
+                        )
+                        .map(|res| warp::reply::json(&res).into_response()),
+                    }
+                    .map(|resp| add_consensus_version_header(resp, fork_name))
+                })
+            },
+        )
+        .boxed()
+}
+
 // GET beacon/states/{state_id}/pending_partial_withdrawals
 pub fn get_beacon_state_pending_partial_withdrawals<T: BeaconChainTypes>(
     beacon_states_path: BeaconStatesPath<T>,

diff --git a/beacon_node/http_api/src/lib.rs b/beacon_node/http_api/src/lib.rs
@@ -649,6 +649,10 @@ pub fn serve<T: BeaconChainTypes>(
     let get_beacon_state_pending_consolidations =
         states::get_beacon_state_pending_consolidations(beacon_states_path.clone());
 
+    // GET beacon/states/{state_id}/proposer_lookahead
+    let get_beacon_state_proposer_lookahead =
+        states::get_beacon_state_proposer_lookahead(beacon_states_path.clone());
+
     // GET beacon/headers
     //
     // Note: this endpoint only returns information about blocks in the canonical chain. Given that
@@ -3333,6 +3337,7 @@ pub fn serve<T: BeaconChainTypes>(
                 .uor(get_beacon_state_pending_deposits)
                 .uor(get_beacon_state_pending_partial_withdrawals)
                 .uor(get_beacon_state_pending_consolidations)
+                .uor(get_beacon_state_proposer_lookahead)
                 .uor(get_beacon_headers)
                 .uor(get_beacon_headers_block_id)
                 .uor(get_beacon_block)

diff --git a/beacon_node/http_api/tests/tests.rs b/beacon_node/http_api/tests/tests.rs
@@ -1418,6 +1418,40 @@ impl ApiTester {
         self
     }
 
+    pub async fn test_beacon_states_proposer_lookahead(self) -> Self {
+        for state_id in self.interesting_state_ids() {
+            let mut state_opt = state_id
+                .state(&self.chain)
+                .ok()
+                .map(|(state, _execution_optimistic, _finalized)| state);
+
+            let result = match self
+                .client
+                .get_beacon_states_proposer_lookahead(state_id.0)
+                .await
+            {
+                Ok(response) => response,
+                Err(e) => panic!("query failed incorrectly: {e:?}"),
+            };
+
+            if result.is_none() && state_opt.is_none() {
+                continue;
+            }
+
+            let state = state_opt.as_mut().expect("result should be none");
+            let expected = state.proposer_lookahead().unwrap();
+
+            let response = result.unwrap();
+            assert_eq!(response.data(), &expected.to_vec());
+
+            // Check that the version header is returned in the response
+            let fork_name = state.fork_name(&self.chain.spec).unwrap();
+            assert_eq!(response.version(), Some(fork_name),);
+        }
+
+        self
+    }
+
     pub async fn test_beacon_headers_all_slots(self) -> Self {
         for slot in 0..CHAIN_LENGTH {
             let slot = Slot::from(slot);
@@ -7295,6 +7329,21 @@ async fn beacon_get_state_info_electra() {
         .await;
 }
 
+#[tokio::test(flavor = "multi_thread", worker_threads = 2)]
+async fn beacon_get_state_info_fulu() {
+    let mut config = ApiTesterConfig::default();
+    config.spec.altair_fork_epoch = Some(Epoch::new(0));
+    config.spec.bellatrix_fork_epoch = Some(Epoch::new(0));
+    config.spec.capella_fork_epoch = Some(Epoch::new(0));
+    config.spec.deneb_fork_epoch = Some(Epoch::new(0));
+    config.spec.electra_fork_epoch = Some(Epoch::new(0));
+    config.spec.fulu_fork_epoch = Some(Epoch::new(0));
+    ApiTester::new_from_config(config)
+        .await
+        .test_beacon_states_proposer_lookahead()
+        .await;
+}
+
 #[tokio::test(flavor = "multi_thread", worker_threads = 2)]
 async fn beacon_get_blocks() {
     ApiTester::new()

diff --git a/common/eth2/src/lib.rs b/common/eth2/src/lib.rs
@@ -898,6 +898,27 @@ impl BeaconNodeHttpClient {
             .map(|opt| opt.map(BeaconResponse::ForkVersioned))
     }
 
+    /// `GET beacon/states/{state_id}/proposer_lookahead`
+    ///
+    /// Returns `Ok(None)` on a 404 error.
+    pub async fn get_beacon_states_proposer_lookahead(
+        &self,
+        state_id: StateId,
+    ) -> Result<Option<ExecutionOptimisticFinalizedBeaconResponse<Vec<u64>>>, Error> {
+        let mut path = self.eth_path(V1)?;
+
+        path.path_segments_mut()
+            .map_err(|()| Error::InvalidUrl(self.server.clone()))?
+            .push("beacon")
+            .push("states")
+            .push(&state_id.to_string())
+            .push("proposer_lookahead");
+
+        self.get_fork_contextual(path, |fork| fork)
+            .await
+            .map(|opt| opt.map(BeaconResponse::ForkVersioned))
+    }
+
     /// `GET beacon/light_client/updates`
     ///
     /// Returns `Ok(None)` on a 404 error.