feat: AccountTreeBackendReader and NullifierTreeBackendReader traits

CHANGELOG.md

@@ -4,14 +4,14 @@
 
 ### Changes
 - Added validation of leaf type on CLAIM note processing to prevent message leaves from being processed as asset claims ([#2730](https://github.com/0xMiden/protocol/pull/2730)).
-
 - Added `AssetAmount` wrapper type for validated fungible asset amounts ([#2721](https://github.com/0xMiden/protocol/pull/2721)).
 - [BREAKING] Renamed `ProvenBatch::new` to `new_unchecked` ([#2687](https://github.com/0xMiden/miden-base/issues/2687)).
 - Added `ShortCapitalString` type and related `TokenSymbol` and `RoleSymbol` types ([#2690](https://github.com/0xMiden/protocol/pull/2690)).
 - [BREAKING] Renamed the guarded multisig component-facing APIs from `multisig_guardian` / `AuthMultisigGuardian` to `guarded_multisig` / `AuthGuardedMultisig`, while retaining the `guardian` auth namespace and guardian-specific procedures.
 - Added shared `ProcedurePolicy` for AuthMultisig ([#2670](https://github.com/0xMiden/protocol/pull/2670)).
 - [BREAKING] Changed `NoteType` encoding from 2 bits to 1 and makes `NoteType::Private` the default ([#2691](https://github.com/0xMiden/miden-base/issues/2691)).
 - Added `BlockNumber::saturating_sub()` ([#2660](https://github.com/0xMiden/protocol/issues/2660)).
+- Added `NullifierTreeBackendReader` and `AccountTreeBackendReader` traits ([#2755](https://github.com/0xMiden/protocol/pull/2755)).
 
 ## 0.14.3 (2026-04-07)
 

Cargo.toml

@@ -70,3 +70,7 @@ rstest          = { version = "0.26" }
 serde           = { default-features = false, version = "1.0" }
 thiserror       = { default-features = false, version = "2.0" }
 tokio           = { default-features = false, features = ["sync"], version = "1" }
+
+[patch.crates-io]
+miden-crypto      = { branch = "sergerad-largesmt-reader-trait", git = "https://github.com/0xmiden/crypto" }
+miden-serde-utils = { branch = "sergerad-largesmt-reader-trait", git = "https://github.com/0xmiden/crypto" }

crates/miden-protocol/src/block/account_tree/backend.rs

@@ -5,19 +5,22 @@ use super::{AccountId, AccountIdKey, AccountIdPrefix, AccountTree, AccountTreeEr
 use crate::Word;
 use crate::crypto::merkle::MerkleError;
 #[cfg(feature = "std")]
-use crate::crypto::merkle::smt::{LargeSmt, LargeSmtError, SmtStorage};
+use crate::crypto::merkle::smt::{LargeSmt, LargeSmtError, SmtStorage, SmtStorageReader};
 use crate::crypto::merkle::smt::{LeafIndex, MutationSet, SMT_DEPTH, Smt, SmtLeaf, SmtProof};
 
-// ACCOUNT TREE BACKEND
+// ACCOUNT TREE BACKEND READER
 // ================================================================================================
 
 /// This trait abstracts over different SMT backends (e.g., `Smt` and `LargeSmt`) to allow
 /// the `AccountTree` to work with either implementation transparently.
 ///
+/// This trait contains only read-only methods. For write methods, see
+/// [`AccountTreeBackend`].
+///
 /// Implementors must provide `Default` for creating empty instances. Users should
 /// instantiate the backend directly (potentially with entries) and then pass it to
 /// [`AccountTree::new`].
-pub trait AccountTreeBackend: Sized {
+pub trait AccountTreeBackendReader: Sized {
     type Error: core::error::Error + Send + 'static;
 
     /// Returns the number of leaves in the SMT.
@@ -29,6 +32,27 @@ pub trait AccountTreeBackend: Sized {
     /// Opens the leaf at the given key, returning a Merkle proof.
     fn open(&self, key: &Word) -> SmtProof;
 
+    /// Returns the value associated with the given key.
+    fn get_value(&self, key: &Word) -> Word;
+
+    /// Returns the leaf at the given key.
+    fn get_leaf(&self, key: &Word) -> SmtLeaf;
+
+    /// Returns the root of the SMT.
+    fn root(&self) -> Word;
+}
+
+// ACCOUNT TREE BACKEND
+// ================================================================================================
+
+/// Extension trait for [`AccountTreeBackendReader`] that provides write methods.
+pub trait AccountTreeBackend: AccountTreeBackendReader {
+    /// Computes the mutation set required to apply the given updates to the SMT.
+    fn compute_mutations(
+        &self,
+        updates: Vec<(Word, Word)>,
+    ) -> Result<MutationSet<SMT_DEPTH, Word, Word>, Self::Error>;
+
     /// Applies the given mutation set to the SMT.
     fn apply_mutations(
         &mut self,
@@ -43,29 +67,14 @@ pub trait AccountTreeBackend: Sized {
         set: MutationSet<SMT_DEPTH, Word, Word>,
     ) -> Result<MutationSet<SMT_DEPTH, Word, Word>, Self::Error>;
 
-    /// Computes the mutation set required to apply the given updates to the SMT.
-    fn compute_mutations(
-        &self,
-        updates: Vec<(Word, Word)>,
-    ) -> Result<MutationSet<SMT_DEPTH, Word, Word>, Self::Error>;
-
     /// Inserts a key-value pair into the SMT, returning the previous value at that key.
     fn insert(&mut self, key: Word, value: Word) -> Result<Word, Self::Error>;
-
-    /// Returns the value associated with the given key.
-    fn get_value(&self, key: &Word) -> Word;
-
-    /// Returns the leaf at the given key.
-    fn get_leaf(&self, key: &Word) -> SmtLeaf;
-
-    /// Returns the root of the SMT.
-    fn root(&self) -> Word;
 }
 
-// BACKEND IMPLEMENTATION FOR SMT
+// BACKEND READER IMPLEMENTATION FOR SMT
 // ================================================================================================
 
-impl AccountTreeBackend for Smt {
+impl AccountTreeBackendReader for Smt {
     type Error = MerkleError;
 
     fn num_leaves(&self) -> usize {
@@ -80,6 +89,30 @@ impl AccountTreeBackend for Smt {
         Smt::open(self, key)
     }
 
+    fn get_value(&self, key: &Word) -> Word {
+        Smt::get_value(self, key)
+    }
+
+    fn get_leaf(&self, key: &Word) -> SmtLeaf {
+        Smt::get_leaf(self, key)
+    }
+
+    fn root(&self) -> Word {
+        Smt::root(self)
+    }
+}
+
+// BACKEND IMPLEMENTATION FOR SMT
+// ================================================================================================
+
+impl AccountTreeBackend for Smt {
+    fn compute_mutations(
+        &self,
+        updates: Vec<(Word, Word)>,
+    ) -> Result<MutationSet<SMT_DEPTH, Word, Word>, Self::Error> {
+        Smt::compute_mutations(self, updates)
+    }
+
     fn apply_mutations(
         &mut self,
         set: MutationSet<SMT_DEPTH, Word, Word>,
@@ -94,37 +127,18 @@ impl AccountTreeBackend for Smt {
         Smt::apply_mutations_with_reversion(self, set)
     }
 
-    fn compute_mutations(
-        &self,
-        updates: Vec<(Word, Word)>,
-    ) -> Result<MutationSet<SMT_DEPTH, Word, Word>, Self::Error> {
-        Smt::compute_mutations(self, updates)
-    }
-
     fn insert(&mut self, key: Word, value: Word) -> Result<Word, Self::Error> {
         Smt::insert(self, key, value)
     }
-
-    fn get_value(&self, key: &Word) -> Word {
-        Smt::get_value(self, key)
-    }
-
-    fn get_leaf(&self, key: &Word) -> SmtLeaf {
-        Smt::get_leaf(self, key)
-    }
-
-    fn root(&self) -> Word {
-        Smt::root(self)
-    }
 }
 
-// BACKEND IMPLEMENTATION FOR LARGE SMT
+// BACKEND READER IMPLEMENTATION FOR LARGE SMT
 // ================================================================================================
 
 #[cfg(feature = "std")]
-impl<Backend> AccountTreeBackend for LargeSmt<Backend>
+impl<Backend> AccountTreeBackendReader for LargeSmt<Backend>
 where
-    Backend: SmtStorage,
+    Backend: SmtStorageReader,
 {
     type Error = MerkleError;
 
@@ -140,6 +154,34 @@ where
         LargeSmt::open(self, key)
     }
 
+    fn get_value(&self, key: &Word) -> Word {
+        LargeSmt::get_value(self, key)
+    }
+
+    fn get_leaf(&self, key: &Word) -> SmtLeaf {
+        LargeSmt::get_leaf(self, key)
+    }
+
+    fn root(&self) -> Word {
+        LargeSmt::root(self)
+    }
+}
+
+// BACKEND IMPLEMENTATION FOR LARGE SMT
+// ================================================================================================
+
+#[cfg(feature = "std")]
+impl<Backend> AccountTreeBackend for LargeSmt<Backend>
+where
+    Backend: SmtStorage,
+{
+    fn compute_mutations(
+        &self,
+        updates: Vec<(Word, Word)>,
+    ) -> Result<MutationSet<SMT_DEPTH, Word, Word>, Self::Error> {
+        LargeSmt::compute_mutations(self, updates).map_err(large_smt_error_to_merkle_error)
+    }
+
     fn apply_mutations(
         &mut self,
         set: MutationSet<SMT_DEPTH, Word, Word>,
@@ -154,28 +196,9 @@ where
         LargeSmt::apply_mutations_with_reversion(self, set).map_err(large_smt_error_to_merkle_error)
     }
 
-    fn compute_mutations(
-        &self,
-        updates: Vec<(Word, Word)>,
-    ) -> Result<MutationSet<SMT_DEPTH, Word, Word>, Self::Error> {
-        LargeSmt::compute_mutations(self, updates).map_err(large_smt_error_to_merkle_error)
-    }
-
     fn insert(&mut self, key: Word, value: Word) -> Result<Word, Self::Error> {
         LargeSmt::insert(self, key, value)
     }
-
-    fn get_value(&self, key: &Word) -> Word {
-        LargeSmt::get_value(self, key)
-    }
-
-    fn get_leaf(&self, key: &Word) -> SmtLeaf {
-        LargeSmt::get_leaf(self, key)
-    }
-
-    fn root(&self) -> Word {
-        LargeSmt::root(self)
-    }
 }
 
 // CONVENIENCE METHODS
@@ -223,6 +246,17 @@ impl AccountTree<Smt> {
     }
 }
 
+#[cfg(feature = "std")]
+impl<Backend> AccountTree<LargeSmt<Backend>>
+where
+    Backend: SmtStorage,
+{
+    /// Returns a read-only account tree backed by a reader view of this tree's storage.
+    pub fn reader(&self) -> AccountTree<LargeSmt<Backend::Reader>> {
+        AccountTree::new_unchecked(self.smt.reader())
+    }
+}
+
 // HELPER FUNCTIONS
 // ================================================================================================
 

crates/miden-protocol/src/block/account_tree/mod.rs

@@ -21,7 +21,7 @@ mod witness;
 pub use witness::AccountWitness;
 
 mod backend;
-pub use backend::AccountTreeBackend;
+pub use backend::{AccountTreeBackend, AccountTreeBackendReader};
 
 mod account_id_key;
 pub use account_id_key::AccountIdKey;
@@ -53,7 +53,7 @@ where
 
 impl<S> AccountTree<S>
 where
-    S: AccountTreeBackend<Error = MerkleError>,
+    S: AccountTreeBackendReader<Error = MerkleError>,
 {
     // CONSTANTS
     // --------------------------------------------------------------------------------------------
@@ -188,6 +188,27 @@ where
         })
     }
 
+    // HELPERS
+    // --------------------------------------------------------------------------------------------
+
+    /// Returns the SMT key of the given account ID prefix.
+    fn id_prefix_to_smt_key(account_id: AccountIdPrefix) -> Word {
+        // We construct this in such a way that we're forced to use the constants, so that when
+        // they're updated, the other usages of the constants are also updated.
+        let mut key = Word::empty();
+        key[Self::KEY_PREFIX_IDX] = account_id.as_felt();
+
+        key
+    }
+}
+
+impl<S> AccountTree<S>
+where
+    S: AccountTreeBackend<Error = MerkleError>,
+{
+    // PUBLIC MUTATORS
+    // --------------------------------------------------------------------------------------------
+
     /// Computes the necessary changes to insert the specified (account ID, state commitment) pairs
     /// into this tree, allowing for validation before applying those changes.
     ///
@@ -245,9 +266,6 @@ where
         Ok(AccountMutationSet::new(mutation_set))
     }
 
-    // PUBLIC MUTATORS
-    // --------------------------------------------------------------------------------------------
-
     /// Inserts the state commitment for the given account ID, returning the previous state
     /// commitment associated with that ID.
     ///
@@ -314,19 +332,6 @@ where
             .map_err(AccountTreeError::ApplyMutations)?;
         Ok(AccountMutationSet::new(reversion))
     }
-
-    // HELPERS
-    // --------------------------------------------------------------------------------------------
-
-    /// Returns the SMT key of the given account ID prefix.
-    fn id_prefix_to_smt_key(account_id: AccountIdPrefix) -> Word {
-        // We construct this in such a way that we're forced to use the constants, so that when
-        // they're updated, the other usages of the constants are also updated.
-        let mut key = Word::empty();
-        key[Self::KEY_PREFIX_IDX] = account_id.as_felt();
-
-        key
-    }
 }
 
 // SERIALIZATION