fix(sequencer): resubmit orphaned tx which comes only after final tip

lez/sequencer/core/src/lib.rs

@@ -1162,12 +1162,6 @@ fn apply_follow_update(
     let (resubmit_txs, outcome) = {
         let mut chain = chain.lock().expect("chain state mutex poisoned");
 
-        // User txs of orphaned blocks, returned to the mempool below.
-        let resubmit_txs: Vec<LeeTransaction> = orphaned
-            .iter()
-            .flat_map(|(_, block)| resubmittable_txs(block))
-            .collect();
-
         // Outcomes align with `adopted`.
         let outcomes = chain.apply_channel_update(&orphaned, &adopted);
         let mut to_persist: Vec<(&Block, bool)> = adopted
@@ -1201,6 +1195,22 @@ fn apply_follow_update(
                 AcceptOutcome::Parked(_) | AcceptOutcome::RetryableFailure(_) => {}
             }
         }
+
+        // User txs of orphaned blocks, returned to the mempool below.
+        //
+        // Computed after the finalized tier has advanced, and only for blocks
+        // above it: the zone-sdk reports a block as orphaned once LIB pruning
+        // drops its inscription from the channel lineage, so every block of
+        // ours is orphaned a poll or two after it finalizes. Those transactions
+        // are irreversibly included, and returning them to the mempool puts
+        // them back in every block we produce from then on.
+        let final_height = chain.final_tip().map(|tip| tip.block_id);
+        let resubmit_txs: Vec<LeeTransaction> = orphaned
+            .iter()
+            .filter(|(_, block)| final_height.is_none_or(|id| block.header.block_id > id))
+            .flat_map(|(_, block)| resubmittable_txs(block))
+            .collect();
+
         // Snapshot the advanced final tier so a restart re-anchors on it.
         let final_meta = final_advanced.then(|| {
             let tip = chain.final_tip().expect("advanced final tier has a tip");

lez/sequencer/core/src/tests.rs

@@ -2172,6 +2172,68 @@ async fn follow_orphan_reverts_head_and_requeues_user_txs() {
     );
 }
 
+#[tokio::test]
+async fn follow_orphan_of_a_finalized_block_requeues_nothing() {
+    // The zone-sdk reports a block as orphaned once LIB pruning drops its
+    // inscription from the channel lineage, which happens a poll or two after
+    // every block of ours finalizes. Its transactions are irreversibly
+    // included, so requeueing them would put them back in every block we
+    // produce from then on.
+    let config = setup_sequencer_config();
+    let (mut sequencer, mempool_handle) =
+        SequencerCoreWithMockClients::start_from_config(config).await;
+
+    let acc1 = initial_public_user_accounts()[0].account_id;
+    let acc2 = initial_public_user_accounts()[1].account_id;
+    let tx = common::test_utils::create_transaction_native_token_transfer(
+        acc1,
+        0,
+        acc2,
+        10,
+        &create_signing_key_for_account1(),
+    );
+    mempool_handle
+        .push((TransactionOrigin::User, tx))
+        .await
+        .unwrap();
+    sequencer.produce_new_block().await.unwrap();
+    let block2 = sequencer.store.get_block_at_id(2).unwrap().unwrap();
+
+    apply_follow_update(
+        &sequencer.store.dbio(),
+        &sequencer.chain(),
+        &mempool_handle,
+        FollowUpdate {
+            finalized: vec![(MsgId::from(block2.header.hash.0), block2.clone())],
+            ..empty_follow_update()
+        },
+    );
+    apply_follow_update(
+        &sequencer.store.dbio(),
+        &sequencer.chain(),
+        &mempool_handle,
+        FollowUpdate {
+            orphaned: vec![(MsgId::from(block2.header.hash.0), block2)],
+            ..empty_follow_update()
+        },
+    );
+
+    assert_eq!(
+        sequencer.chain_height(),
+        2,
+        "an irreversible block cannot be reverted"
+    );
+    assert_eq!(
+        sequencer.with_state(|s| s.get_account_by_id(acc2).balance),
+        20010,
+        "the finalized transfer stands"
+    );
+    assert!(
+        sequencer.mempool.pop().is_none(),
+        "a transaction that is already irreversible must not be requeued"
+    );
+}
+
 #[tokio::test]
 async fn follow_finalized_own_block_moves_final_tier_and_marks_store() {
     let config = setup_sequencer_config();