From 5ca61c499da14c1804437fb06a2a0cbd136b355a Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Tom=C3=A1s=20Gr=C3=BCner?=
 <47506558+MegaRedHand@users.noreply.github.com>
Date: Fri, 27 Feb 2026 11:35:05 -0300
Subject: [PATCH 1/2] fix: subscribe to subnet when aggregating only

---
 bin/ethlambda/src/main.rs |  1 +
 crates/net/p2p/src/lib.rs | 23 ++++++++++++++++-------
 2 files changed, 17 insertions(+), 7 deletions(-)

diff --git a/bin/ethlambda/src/main.rs b/bin/ethlambda/src/main.rs
index a0b4c4b3..c42a4d28 100644
--- a/bin/ethlambda/src/main.rs
+++ b/bin/ethlambda/src/main.rs
@@ -134,6 +134,7 @@ async fn main() -> eyre::Result<()> {
         store.clone(),
         first_validator_id,
         options.attestation_committee_count,
+        options.is_aggregator,
     ));
 
     ethlambda_rpc::start_rpc_server(metrics_socket, store)
diff --git a/crates/net/p2p/src/lib.rs b/crates/net/p2p/src/lib.rs
index 4e2a4651..9089d6ff 100644
--- a/crates/net/p2p/src/lib.rs
+++ b/crates/net/p2p/src/lib.rs
@@ -66,6 +66,7 @@ pub async fn start_p2p(
     store: Store,
     validator_id: Option<u64>,
     attestation_committee_count: u64,
+    is_aggregator: bool,
 ) {
     let config = libp2p::gossipsub::ConfigBuilder::default()
         // d
@@ -176,22 +177,30 @@ pub async fn start_p2p(
         .subscribe(&aggregation_topic)
         .unwrap();
 
-    // Subscribe to attestation subnet topic (validators subscribe to their committee's subnet)
+    // Build attestation subnet topic (needed for publishing even without subscribing)
     // attestation_committee_count is validated to be >= 1 by clap at CLI parse time.
     let subnet_id = validator_id.map(|vid| vid % attestation_committee_count);
     let attestation_topic_kind = match subnet_id {
         Some(id) => format!("{ATTESTATION_SUBNET_TOPIC_PREFIX}_{id}"),
-        // Non-validators subscribe to subnet 0 to receive attestations
+        // Non-validators use subnet 0 for publishing
         None => format!("{ATTESTATION_SUBNET_TOPIC_PREFIX}_0"),
     };
     let attestation_topic_str =
         format!("/leanconsensus/{network}/{attestation_topic_kind}/ssz_snappy");
     let attestation_topic = libp2p::gossipsub::IdentTopic::new(attestation_topic_str);
-    swarm
-        .behaviour_mut()
-        .gossipsub
-        .subscribe(&attestation_topic)
-        .unwrap();
+
+    // Only aggregators subscribe to attestation subnets; non-aggregators
+    // publish via gossipsub's fanout mechanism without subscribing.
+    if is_aggregator {
+        swarm
+            .behaviour_mut()
+            .gossipsub
+            .subscribe(&attestation_topic)
+            .unwrap();
+        info!(%attestation_topic_kind, "Subscribed to attestation subnet");
+    } else {
+        info!(%attestation_topic_kind, "Skipping attestation subnet subscription (not an aggregator)");
+    }
 
     info!(socket=%listening_socket, "P2P node started");
 

From 44c8c56dd36b34ac0bff8718fc2ceeb31e2f6a0b Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Tom=C3=A1s=20Gr=C3=BCner?=
 <47506558+MegaRedHand@users.noreply.github.com>
Date: Fri, 27 Feb 2026 12:04:53 -0300
Subject: [PATCH 2/2] refactor: add error handling

---
 bin/ethlambda/src/main.rs | 4 ++--
 crates/net/p2p/src/lib.rs | 8 +++-----
 2 files changed, 5 insertions(+), 7 deletions(-)

diff --git a/bin/ethlambda/src/main.rs b/bin/ethlambda/src/main.rs
index c42a4d28..7b68abad 100644
--- a/bin/ethlambda/src/main.rs
+++ b/bin/ethlambda/src/main.rs
@@ -144,8 +144,8 @@ async fn main() -> eyre::Result<()> {
     info!("Node initialized");
 
     tokio::select! {
-        _ = p2p_handle => {
-            panic!("P2P node task has exited unexpectedly");
+        result = p2p_handle => {
+            panic!("P2P node task has exited unexpectedly: {result:?}");
         }
         _ = tokio::signal::ctrl_c() => {
             // Ctrl-C received, shutting down
diff --git a/crates/net/p2p/src/lib.rs b/crates/net/p2p/src/lib.rs
index 9089d6ff..2ebec1d3 100644
--- a/crates/net/p2p/src/lib.rs
+++ b/crates/net/p2p/src/lib.rs
@@ -67,7 +67,7 @@ pub async fn start_p2p(
     validator_id: Option<u64>,
     attestation_committee_count: u64,
     is_aggregator: bool,
-) {
+) -> Result<(), libp2p::gossipsub::SubscriptionError> {
     let config = libp2p::gossipsub::ConfigBuilder::default()
         // d
         .mesh_n(8)
@@ -195,11 +195,8 @@ pub async fn start_p2p(
         swarm
             .behaviour_mut()
             .gossipsub
-            .subscribe(&attestation_topic)
-            .unwrap();
+            .subscribe(&attestation_topic)?;
         info!(%attestation_topic_kind, "Subscribed to attestation subnet");
-    } else {
-        info!(%attestation_topic_kind, "Skipping attestation subnet subscription (not an aggregator)");
     }
 
     info!(socket=%listening_socket, "P2P node started");
@@ -223,6 +220,7 @@ pub async fn start_p2p(
     };
 
     event_loop(server).await;
+    Ok(())
 }
 
 /// [libp2p Behaviour](libp2p::swarm::NetworkBehaviour) combining Gossipsub and Request-Response Behaviours