chore(storage): Add error handling on Store::get_forkchoice_store

crates/blockchain/src/store.rs

@@ -1620,7 +1620,8 @@ mod tests {
             },
         };
         let backend = Arc::new(InMemoryBackend::new());
-        let mut store = Store::get_forkchoice_store(backend, genesis_state, genesis_block);
+        let mut store = Store::get_forkchoice_store(backend, genesis_state, genesis_block)
+            .expect("anchor state and block must match");
 
         let head_root = store.head();
         let att_data = AttestationData {

crates/blockchain/tests/forkchoice_spectests.rs

@@ -44,7 +44,8 @@ fn run(path: &Path) -> datatest_stable::Result<()> {
         let anchor_block: Block = test.anchor_block.into();
         let genesis_time = anchor_state.config.genesis_time;
         let backend = Arc::new(InMemoryBackend::new());
-        let mut store = Store::get_forkchoice_store(backend, anchor_state, anchor_block);
+        let mut store = Store::get_forkchoice_store(backend, anchor_state, anchor_block)
+            .expect("anchor state and block must match");
 
         // Block registry: maps block labels to their roots
         let mut block_registry: HashMap<String, H256> = HashMap::new();

crates/blockchain/tests/signature_spectests.rs

@@ -42,7 +42,8 @@ fn run(path: &Path) -> datatest_stable::Result<()> {
         // Initialize the store with the anchor state and block
         let genesis_time = anchor_state.config.genesis_time;
         let backend = Arc::new(InMemoryBackend::new());
-        let mut st = Store::get_forkchoice_store(backend, anchor_state, anchor_block);
+        let mut st = Store::get_forkchoice_store(backend, anchor_state, anchor_block)
+            .expect("anchor state and block must match");
 
         // Step 2: Run the state transition function with the block fixture
         let signed_block: SignedBlock = test.signed_block.into();

crates/storage/Cargo.toml

@@ -14,6 +14,7 @@ ethlambda-types.workspace = true
 
 tracing.workspace = true
 rocksdb.workspace = true
+thiserror.workspace = true
 
 libssz.workspace = true
 libssz-derive.workspace = true

crates/storage/src/lib.rs

@@ -3,4 +3,4 @@ pub mod backend;
 mod store;
 
 pub use api::{ALL_TABLES, StorageBackend, StorageReadView, StorageWriteBatch, Table};
-pub use store::{ForkCheckpoints, Store};
+pub use store::{ForkCheckpoints, GetForkchoiceStoreError, Store};

crates/storage/src/store.rs

@@ -20,8 +20,23 @@ use ethlambda_types::{
     state::{ChainConfig, State},
 };
 use libssz::{SszDecode, SszEncode};
+use thiserror::Error;
 use tracing::info;
 
+/// Errors returned by [`Store::get_forkchoice_store`].
+#[derive(Debug, Error)]
+pub enum GetForkchoiceStoreError {
+    #[error(
+        "anchor block header doesn't match state's latest_block_header \
+         (compared with state_root zeroed): state header = {state_header:?}, \
+         block header = {block_header:?}"
+    )]
+    HeaderMismatch {
+        state_header: Box<BlockHeader>,
+        block_header: Box<BlockHeader>,
+    },
+}
+
 /// Checkpoints to update in the forkchoice store.
 ///
 /// Used with `Store::update_checkpoints` to update head and optionally
@@ -470,27 +485,34 @@ impl Store {
     /// The block must match the state's `latest_block_header`.
     /// Named to mirror the spec's `get_forkchoice_store` function.
     ///
-    /// # Panics
+    /// # Errors
     ///
-    /// Panics if the block's header doesn't match the state's `latest_block_header`
-    /// (comparing all fields except `state_root`, which is computed internally).
+    /// Returns [`GetForkchoiceStoreError::HeaderMismatch`] if the block's header
+    /// doesn't match the state's `latest_block_header` (comparing all fields
+    /// except `state_root`, which is computed internally).
     pub fn get_forkchoice_store(
         backend: Arc<dyn StorageBackend>,
         anchor_state: State,
         anchor_block: Block,
-    ) -> Self {
+    ) -> Result<Self, GetForkchoiceStoreError> {
         // Compare headers with state_root zeroed (init_store handles state_root separately)
         let mut state_header = anchor_state.latest_block_header.clone();
         let mut block_header = anchor_block.header();
         state_header.state_root = H256::ZERO;
         block_header.state_root = H256::ZERO;
 
-        assert_eq!(
-            state_header, block_header,
-            "block header doesn't match state's latest_block_header"
-        );
+        if state_header != block_header {
+            return Err(GetForkchoiceStoreError::HeaderMismatch {
+                state_header: Box::new(state_header),
+                block_header: Box::new(block_header),
+            });
+        }
 
-        Self::init_store(backend, anchor_state, Some(anchor_block.body))
+        Ok(Self::init_store(
+            backend,
+            anchor_state,
+            Some(anchor_block.body),
+        ))
     }
 
     /// Internal helper to initialize the store with anchor data.