feat(state): Add a AnyChainBlock state request for querying blocks in side chains

zebra-state/CHANGELOG.md

@@ -10,6 +10,7 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 ### Added
 
 - Added `ReadRequest::IsTransparentOutputSpent` and `ReadResponse::IsTransparentOutputSpent` to the read state service ([#10235](https://github.com/ZcashFoundation/zebra/pull/10235))
+- Added `{ReadRequest, Request}::AnyChainBlock` to the read state service ([#10325](https://github.com/ZcashFoundation/zebra/pull/10325))
 
 
 ## [4.0.0] - 2026-02-05

zebra-state/src/request.rs

@@ -892,6 +892,17 @@ pub enum Request {
     /// [`block::Height`] using `.into()`.
     Block(HashOrHeight),
 
+    /// Looks up a block by hash in any current chain or by height in the current best chain.
+    ///
+    /// Returns
+    ///
+    /// * [`Response::Block(Some(Arc<Block>))`](Response::Block) if the block is in the best chain;
+    /// * [`Response::Block(None)`](Response::Block) otherwise.
+    ///
+    /// Note: the [`HashOrHeight`] can be constructed from a [`block::Hash`] or
+    /// [`block::Height`] using `.into()`.
+    AnyChainBlock(HashOrHeight),
+
     //// Same as Block, but also returns serialized block size.
     ////
     /// Returns
@@ -1032,7 +1043,6 @@ impl Request {
         match self {
             Request::CommitSemanticallyVerifiedBlock(_) => "commit_semantically_verified_block",
             Request::CommitCheckpointVerifiedBlock(_) => "commit_checkpoint_verified_block",
-
             Request::AwaitUtxo(_) => "await_utxo",
             Request::Depth(_) => "depth",
             Request::Tip => "tip",
@@ -1041,6 +1051,7 @@ impl Request {
             Request::AnyChainTransaction(_) => "any_chain_transaction",
             Request::UnspentBestChainUtxo { .. } => "unspent_best_chain_utxo",
             Request::Block(_) => "block",
+            Request::AnyChainBlock(_) => "any_chain_block",
             Request::BlockAndSize(_) => "block_and_size",
             Request::BlockHeader(_) => "block_header",
             Request::FindBlockHashes { .. } => "find_block_hashes",
@@ -1109,6 +1120,17 @@ pub enum ReadRequest {
     /// [`block::Height`] using `.into()`.
     Block(HashOrHeight),
 
+    /// Looks up a block by hash in any current chain or by height in the current best chain.
+    ///
+    /// Returns
+    ///
+    /// * [`ReadResponse::Block(Some(Arc<Block>))`](ReadResponse::Block) if the block is in the best chain;
+    /// * [`ReadResponse::Block(None)`](ReadResponse::Block) otherwise.
+    ///
+    /// Note: the [`HashOrHeight`] can be constructed from a [`block::Hash`] or
+    /// [`block::Height`] using `.into()`.
+    AnyChainBlock(HashOrHeight),
+
     //// Same as Block, but also returns serialized block size.
     ////
     /// Returns
@@ -1393,6 +1415,7 @@ impl ReadRequest {
             ReadRequest::BlockInfo(_) => "block_info",
             ReadRequest::Depth(_) => "depth",
             ReadRequest::Block(_) => "block",
+            ReadRequest::AnyChainBlock(_) => "any_chain_block",
             ReadRequest::BlockAndSize(_) => "block_and_size",
             ReadRequest::BlockHeader(_) => "block_header",
             ReadRequest::Transaction(_) => "transaction",
@@ -1452,6 +1475,9 @@ impl TryFrom<Request> for ReadRequest {
             Request::BestChainBlockHash(hash) => Ok(ReadRequest::BestChainBlockHash(hash)),
 
             Request::Block(hash_or_height) => Ok(ReadRequest::Block(hash_or_height)),
+            Request::AnyChainBlock(hash_or_height) => {
+                Ok(ReadRequest::AnyChainBlock(hash_or_height))
+            }
             Request::BlockAndSize(hash_or_height) => Ok(ReadRequest::BlockAndSize(hash_or_height)),
             Request::BlockHeader(hash_or_height) => Ok(ReadRequest::BlockHeader(hash_or_height)),
             Request::Transaction(tx_hash) => Ok(ReadRequest::Transaction(tx_hash)),

zebra-state/src/service.rs

@@ -1239,6 +1239,7 @@ impl Service<Request> for StateService {
             | Request::AnyChainTransaction(_)
             | Request::UnspentBestChainUtxo(_)
             | Request::Block(_)
+            | Request::AnyChainBlock(_)
             | Request::BlockAndSize(_)
             | Request::BlockHeader(_)
             | Request::FindBlockHashes { .. }
@@ -1484,6 +1485,30 @@ impl Service<ReadRequest> for ReadStateService {
                 .wait_for_panics()
             }
 
+            ReadRequest::AnyChainBlock(hash_or_height) => {
+                let state = self.clone();
+
+                tokio::task::spawn_blocking(move || {
+                    span.in_scope(move || {
+                        let block = state.non_finalized_state_receiver.with_watch_data(
+                            |non_finalized_state| {
+                                read::any_chain_block(
+                                    non_finalized_state,
+                                    &state.db,
+                                    hash_or_height,
+                                )
+                            },
+                        );
+
+                        // The work is done in the future.
+                        timer.finish(module_path!(), line!(), "ReadRequest::AnyChainBlock");
+
+                        Ok(ReadResponse::Block(block))
+                    })
+                })
+                .wait_for_panics()
+            }
+
             // Used by the get_block (raw) RPC and the StateService.
             ReadRequest::BlockAndSize(hash_or_height) => {
                 let state = self.clone();

zebra-state/src/service/read.rs

@@ -29,8 +29,9 @@ pub use address::{
     utxo::{address_utxos, AddressUtxos},
 };
 pub use block::{
-    any_transaction, any_utxo, block, block_and_size, block_header, block_info, mined_transaction,
-    transaction_hashes_for_any_block, transaction_hashes_for_block, unspent_utxo,
+    any_chain_block, any_transaction, any_utxo, block, block_and_size, block_header, block_info,
+    mined_transaction, transaction_hashes_for_any_block, transaction_hashes_for_block,
+    unspent_utxo,
 };
 
 #[cfg(feature = "indexer")]

zebra-state/src/service/read/block.rs

@@ -37,6 +37,28 @@ use crate::{
 #[cfg(feature = "indexer")]
 use crate::request::Spend;
 
+/// Returns the [`Block`] with [`block::Hash`] or
+/// [`Height`], if it exists in the non-finalized state or finalized `db`.
+///
+/// Checks all non-finalized chain for block hashes or the best chain for heights.
+pub fn any_chain_block(
+    non_finalized: NonFinalizedState,
+    db: &ZebraDb,
+    hash_or_height: HashOrHeight,
+) -> Option<Arc<Block>> {
+    let unchecked_best_chain = if let HashOrHeight::Hash(hash) = hash_or_height {
+        if let Some(block) = non_finalized.any_block_by_hash(hash) {
+            return Some(block);
+        }
+
+        None
+    } else {
+        non_finalized.best_chain()
+    };
+
+    block(unchecked_best_chain, db, hash_or_height)
+}
+
 /// Returns the [`Block`] with [`block::Hash`] or
 /// [`Height`], if it exists in the non-finalized `chain` or finalized `db`.
 pub fn block<C>(chain: Option<C>, db: &ZebraDb, hash_or_height: HashOrHeight) -> Option<Arc<Block>>