diff --git a/indexer/src/lib.rs b/indexer/src/lib.rs
index b7d70dab..a713e98b 100644
--- a/indexer/src/lib.rs
+++ b/indexer/src/lib.rs
@@ -1,4 +1,4 @@
-use std::sync::Arc;
+use std::{collections::HashMap, sync::Arc};
 
 use anyhow::Result;
 use bedrock_client::{BasicAuthCredentials, BedrockClient};
@@ -45,6 +45,7 @@ impl IndexerCore {
             // No state setup for now, future task.
             state: IndexerState {
                 latest_seen_block: Arc::new(RwLock::new(0)),
+                finality_map: Arc::new(RwLock::new(HashMap::new())),
             },
         })
     }
@@ -93,7 +94,7 @@ impl IndexerCore {
                         }
 
                         // Sending data into sequencer, may need to be expanded.
-                        let message = IndexerToSequencerMessage::BlockObserved {
+                        let message = IndexerToSequencerMessage::FinalizedBlockObserved {
                             l1_block_id: block_info.height,
                             l2_block_height: l2_block.block_id,
                         };
diff --git a/indexer/src/message.rs b/indexer/src/message.rs
index 195696ad..646cdfa9 100644
--- a/indexer/src/message.rs
+++ b/indexer/src/message.rs
@@ -1,7 +1,13 @@
 #[derive(Debug, Clone)]
 pub enum IndexerToSequencerMessage {
-    BlockObserved {
+    FinalizedBlockObserved {
         l1_block_id: u64,
         l2_block_height: u64,
     },
+    BlockEnteredChain {
+        l2_block_height: u64,
+    },
+    ChainRestructurization {
+        new_l1_last_block_height: u64,
+    },
 }
diff --git a/indexer/src/state.rs b/indexer/src/state.rs
index bd05971f..de89a018 100644
--- a/indexer/src/state.rs
+++ b/indexer/src/state.rs
@@ -1,9 +1,9 @@
-use std::sync::Arc;
+use std::{collections::HashMap, sync::Arc};
 
 use tokio::sync::RwLock;
 
 #[derive(Debug, Clone)]
 pub struct IndexerState {
-    // Only one field for now, for testing.
     pub latest_seen_block: Arc<RwLock<u64>>,
+    pub finality_map: Arc<RwLock<HashMap<u64, u64>>>,
 }