fix: off by one on Cosmos and EVM

rust/main/chains/hyperlane-cosmos/src/cw/mailbox/dispatch_indexer.rs

@@ -156,9 +156,12 @@ impl SequenceAwareIndexer<HyperlaneMessage> for CwMailboxDispatchIndexer {
     async fn latest_sequence_count_and_tip(&self) -> ChainResult<(Option<u32>, u32)> {
         let tip = Indexer::<HyperlaneMessage>::get_finalized_block_number(&self).await?;
 
-        let sequence = self.mailbox.nonce_at_block(tip.into()).await?;
+        let nonce = self.mailbox.nonce_at_block(tip.into()).await?;
+        // Convert nonce (next message count) to the last indexed sequence (nonce - 1)
+        // If nonce is 0, there are no messages sent yet
+        let sequence = nonce.checked_sub(1);
 
-        Ok((Some(sequence), tip))
+        Ok((sequence, tip))
     }
 }
 

rust/main/chains/hyperlane-cosmos/src/cw/merkle_tree_hook.rs

@@ -142,7 +142,7 @@ impl MerkleTreeHook for CwMerkleTreeHook {
                 merkle_tree_hook_address: self.address,
                 mailbox_domain: self.domain.id(),
                 root: response.root.parse()?,
-                index: response.count,
+                index: response.count.saturating_sub(1),
             },
             block_height: Some(height),
         })
@@ -355,9 +355,12 @@ impl Indexer<MerkleTreeInsertion> for CwMerkleTreeHookIndexer {
 impl SequenceAwareIndexer<MerkleTreeInsertion> for CwMerkleTreeHookIndexer {
     async fn latest_sequence_count_and_tip(&self) -> ChainResult<(Option<u32>, u32)> {
         let tip = CosmosEventIndexer::get_finalized_block_number(self).await?;
-        let sequence = self.merkle_tree_hook.count_at_block(tip.into()).await?;
+        let count = self.merkle_tree_hook.count_at_block(tip.into()).await?;
+        // Convert count to the last indexed sequence (count - 1)
+        // If count is 0, there are no indexed sequences yet
+        let sequence = count.checked_sub(1);
 
-        Ok((Some(sequence), tip))
+        Ok((sequence, tip))
     }
 }
 

rust/main/chains/hyperlane-cosmos/src/native/indexers/dispatch.rs

@@ -118,7 +118,9 @@ impl SequenceAwareIndexer<HyperlaneMessage> for CosmosNativeDispatchIndexer {
             .mailbox(self.address.encode_hex(), Some(tip as u64))
             .await?;
         match mailbox.mailbox {
-            Some(mailbox) => Ok((Some(mailbox.message_sent), tip)),
+            // Convert count to the last indexed sequence (count - 1)
+            // If count is 0, there are no messages sent yet
+            Some(mailbox) => Ok((mailbox.message_sent.checked_sub(1), tip)),
             _ => Ok((None, tip)),
         }
     }

rust/main/chains/hyperlane-cosmos/src/native/indexers/merkle_tree_hook.rs

@@ -255,6 +255,9 @@ impl SequenceAwareIndexer<MerkleTreeInsertion> for CosmosNativeMerkleTreeHook {
             .as_ref()
             .and_then(|m| m.merkle_tree.as_ref())
             .map(|merkle_tree| merkle_tree.count);
-        Ok((merkle_tree_count, tip))
+        // Convert count to the last indexed sequence (count - 1)
+        // If count is 0, there are no indexed sequences yet
+        let merkle_tree_sequence = merkle_tree_count.and_then(|count| count.checked_sub(1));
+        Ok((merkle_tree_sequence, tip))
     }
 }

rust/main/chains/hyperlane-ethereum/src/contracts/mailbox.rs

@@ -200,8 +200,11 @@ where
 {
     async fn latest_sequence_count_and_tip(&self) -> ChainResult<(Option<u32>, u32)> {
         let tip = Indexer::<HyperlaneMessage>::get_finalized_block_number(self).await?;
-        let sequence = self.contract.nonce().block(u64::from(tip)).call().await?;
-        Ok((Some(sequence), tip))
+        let nonce = self.contract.nonce().block(u64::from(tip)).call().await?;
+        // Convert nonce (next message count) to the last indexed sequence (nonce - 1)
+        // If nonce is 0, there are no messages sent yet
+        let sequence = nonce.checked_sub(1);
+        Ok((sequence, tip))
     }
 }
 

rust/main/chains/hyperlane-ethereum/src/contracts/merkle_tree_hook.rs

@@ -185,8 +185,11 @@ where
     // `SequenceAwareIndexer` and `Indexer`.
     async fn latest_sequence_count_and_tip(&self) -> ChainResult<(Option<u32>, u32)> {
         let tip = self.get_finalized_block_number().await?;
-        let sequence = self.contract.count().block(u64::from(tip)).call().await?;
-        Ok((Some(sequence), tip))
+        let count = self.contract.count().block(u64::from(tip)).call().await?;
+        // Convert count to the last indexed sequence (count - 1)
+        // If count is 0, there are no messages indexed yet
+        let sequence = count.checked_sub(1);
+        Ok((sequence, tip))
     }
 }