diff --git a/Cargo.lock b/Cargo.lock
index 3f973541..66916640 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -3865,6 +3865,7 @@ dependencies = [
  "storage",
  "tempfile",
  "testnet_initial_state",
+ "thiserror 2.0.18",
  "tokio",
  "url",
 ]
diff --git a/lez/common/src/block.rs b/lez/common/src/block.rs
index 029bcfba..a8149e7c 100644
--- a/lez/common/src/block.rs
+++ b/lez/common/src/block.rs
@@ -178,7 +178,7 @@ mod tests {
         }
         .into_pending_block(&key);
 
-        let mut tampered = block.clone();
+        let mut tampered = block;
         tampered.header.timestamp = 99; // header changed; stale hash no longer matches
         assert_ne!(tampered.recompute_hash(), tampered.header.hash);
     }
diff --git a/lez/indexer/core/Cargo.toml b/lez/indexer/core/Cargo.toml
index 758acdd6..2dfdf1bf 100644
--- a/lez/indexer/core/Cargo.toml
+++ b/lez/indexer/core/Cargo.toml
@@ -25,6 +25,7 @@ futures.workspace = true
 url.workspace = true
 logos-blockchain-core.workspace = true
 serde_json.workspace = true
+thiserror.workspace = true
 async-stream.workspace = true
 tokio.workspace = true
 
diff --git a/lez/indexer/core/src/block_store.rs b/lez/indexer/core/src/block_store.rs
index a1cb71ef..617c4c60 100644
--- a/lez/indexer/core/src/block_store.rs
+++ b/lez/indexer/core/src/block_store.rs
@@ -168,13 +168,11 @@ impl IndexerStore {
                         )
                         .context("Failed to execute genesis public transaction")?;
                 } else {
-                    transaction
-                        .clone()
-                        .execute_on_state(
-                            &mut state_guard,
-                            block.header.block_id,
-                            block.header.timestamp,
-                        )?;
+                    transaction.clone().execute_on_state(
+                        &mut state_guard,
+                        block.header.block_id,
+                        block.header.timestamp,
+                    )?;
                 }
             }
 
diff --git a/lez/indexer/core/src/ingest_error.rs b/lez/indexer/core/src/ingest_error.rs
new file mode 100644
index 00000000..4240a84c
--- /dev/null
+++ b/lez/indexer/core/src/ingest_error.rs
@@ -0,0 +1,59 @@
+use common::HashType;
+use serde::{Deserialize, Serialize};
+
+/// Why the indexer could not apply an L2 block from the channel. Stored inside a
+/// [`crate::chain_breaker::ChainBreaker`] and surfaced on the status snapshot.
+#[derive(Debug, Clone, Serialize, Deserialize, thiserror::Error)]
+#[serde(rename_all = "camelCase")]
+pub enum BlockIngestError {
+    #[error("failed to deserialize L2 block: {0}")]
+    Deserialize(String),
+    #[error("unexpected block id: expected {expected}, got {got}")]
+    UnexpectedBlockId { expected: u64, got: u64 },
+    #[error("broken chain link: expected prev {expected_prev}, got {got_prev}")]
+    BrokenChainLink {
+        expected_prev: HashType,
+        got_prev: HashType,
+    },
+    #[error("block hash mismatch: computed {computed}, header {header}")]
+    HashMismatch {
+        computed: HashType,
+        header: HashType,
+    },
+    #[error("state transition failed: {0}")]
+    StateTransition(String),
+    #[error("storage error: {0}")]
+    Storage(String),
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn serializes_and_round_trips_externally_tagged() {
+        let err = BlockIngestError::UnexpectedBlockId {
+            expected: 5,
+            got: 7,
+        };
+        let value = serde_json::to_value(&err).expect("serialize");
+        assert_eq!(
+            value,
+            serde_json::json!({ "unexpectedBlockId": { "expected": 5, "got": 7 } })
+        );
+        let back: BlockIngestError = serde_json::from_value(value).expect("deserialize");
+        assert!(matches!(
+            back,
+            BlockIngestError::UnexpectedBlockId {
+                expected: 5,
+                got: 7
+            }
+        ));
+    }
+
+    #[test]
+    fn display_is_human_readable() {
+        let err = BlockIngestError::StateTransition("nonce too low".to_owned());
+        assert_eq!(err.to_string(), "state transition failed: nonce too low");
+    }
+}
diff --git a/lez/indexer/core/src/lib.rs b/lez/indexer/core/src/lib.rs
index 0d595fc0..35ff3c6b 100644
--- a/lez/indexer/core/src/lib.rs
+++ b/lez/indexer/core/src/lib.rs
@@ -5,6 +5,7 @@ use arc_swap::ArcSwap;
 use common::block::Block;
 // ToDo: Remove after testnet
 use futures::StreamExt as _;
+pub use ingest_error::BlockIngestError;
 use log::{error, info, warn};
 use logos_blockchain_core::header::HeaderId;
 use logos_blockchain_zone_sdk::{
@@ -16,9 +17,9 @@ use crate::{
     config::IndexerConfig,
     status::{IndexerStatus, IndexerSyncStatus},
 };
-
 pub mod block_store;
 pub mod config;
+pub mod ingest_error;
 pub mod status;
 
 #[derive(Clone)]