1/3 Serialize sparse MAST forests

CHANGELOG.md

@@ -40,6 +40,7 @@
 
 - Reduced optimized benchmark build time by relaxing forced inlining in processor execution helpers ([#3292](https://github.com/0xMiden/miden-vm/pull/3292)).
 - Added no-op handlers for readonly debugger events to `CoreLibrary::handlers`, so hosts that load the core library can execute programs emitting those events without registering no-op handlers manually ([#3305](https://github.com/0xMiden/miden-vm/pull/3305)).
+- Added trusted sparse MAST forest serialization for trace replay payloads ([#3313](https://github.com/0xMiden/miden-vm/pull/3313)).
 
 ## v0.24.0 (2026-06-24)
 

core/src/mast/mod.rs

@@ -54,7 +54,7 @@ use proptest::prelude::*;
 use serde::{Deserialize, Serialize};
 
 #[cfg(feature = "serde")]
-use crate::serde::{Deserializable, SliceReader};
+use crate::serde::SliceReader;
 
 mod node;
 #[cfg(any(test, feature = "arbitrary"))]
@@ -71,7 +71,7 @@ use crate::{
     Felt, Word,
     advice::AdviceMap,
     crypto::hash::Poseidon2,
-    serde::{ByteWriter, DeserializationError, Serializable},
+    serde::{ByteWriter, Deserializable, DeserializationError, Serializable},
     utils::{DenseIdMap, Idx, IndexVec, hash_string_to_word},
 };
 
@@ -1242,6 +1242,18 @@ impl Serializable for MastNodeId {
     }
 }
 
+impl Deserializable for MastNodeId {
+    fn read_from<R: crate::serde::ByteReader>(
+        source: &mut R,
+    ) -> Result<Self, DeserializationError> {
+        Ok(Self(<u32 as Deserializable>::read_from(source)?))
+    }
+
+    fn min_serialized_size() -> usize {
+        <u32 as Deserializable>::min_serialized_size()
+    }
+}
+
 impl fmt::Display for MastNodeId {
     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
         write!(f, "MastNodeId({})", self.0)

core/src/mast/serialization/mod.rs

@@ -76,9 +76,13 @@
 //! same contiguous array on the wire.
 //!
 //! Public entry points adopt these policies:
-//! - [`MastForest::read_from_bytes`]: trusted execution payload, no hashless support.
+//! - [`MastForest::read_from_bytes`]: trusted dense execution payload, no hashless support.
 //! - [`MastForestWireView::new`]: trusted wire-backed cache access; rejects hashless and legacy
 //!   debug-bearing payloads.
+//! - [`crate::mast::SparseMastForest::read_from_bytes`]: separate trusted sparse replay payloads
+//!   for serialized trace-generation inputs. Sparse payloads preserve the sparse node and digest
+//!   maps produced by tracing; they do not share the dense `MastForest` wire format and are not an
+//!   untrusted validation boundary.
 //! - [`crate::mast::UntrustedMastForest::read_from_bytes`] /
 //!   [`crate::mast::UntrustedMastForest::read_from_bytes_with_options`]: untrusted parsing plus
 //!   later validation before use.
@@ -112,6 +116,8 @@ mod layout;
 pub(super) use layout::ForestLayout;
 use layout::{OffsetTrackingReader, TrackingReader, WireFlags, read_header_and_scan_layout};
 
+mod sparse;
+
 mod resolved;
 use resolved::{ResolvedSerializedForest, basic_block_offset_for_node_index};