fix(kona): use BTreeMap for deterministic JSON serialization in interop host

rust/kona/bin/host/src/interop/cfg.rs

@@ -22,7 +22,12 @@ use kona_providers_alloy::{OnlineBeaconClient, OnlineBlobProvider};
 use kona_std_fpvm::{FileChannel, FileDescriptor};
 use op_alloy_network::Optimism;
 use serde::Serialize;
-use std::{collections::HashMap, path::PathBuf, str::FromStr, sync::Arc};
+use std::{
+    collections::{BTreeMap, HashMap},
+    path::PathBuf,
+    str::FromStr,
+    sync::Arc,
+};
 use tokio::task::{self, JoinHandle};
 
 /// The interop host application.
@@ -228,13 +233,14 @@ impl InteropHost {
     }
 
     /// Reads the [`RollupConfig`]s from the file system and returns a map of L2 chain ID ->
-    /// [`RollupConfig`]s.
+    /// [`RollupConfig`]s. Uses `BTreeMap` to ensure deterministic JSON serialization order when
+    /// these configs are served as preimages to the cannon VM.
     pub fn read_rollup_configs(
         &self,
-    ) -> Option<Result<HashMap<u64, RollupConfig>, InteropHostError>> {
+    ) -> Option<Result<BTreeMap<u64, RollupConfig>, InteropHostError>> {
         let rollup_config_paths = self.rollup_config_paths.as_ref()?;
 
-        Some(rollup_config_paths.iter().try_fold(HashMap::default(), |mut acc, path| {
+        Some(rollup_config_paths.iter().try_fold(BTreeMap::default(), |mut acc, path| {
             // Read the serialized config from the file system.
             let ser_config = std::fs::read_to_string(path)?;
 

rust/kona/crates/protocol/interop/src/depset.rs

@@ -1,6 +1,6 @@
 use crate::MESSAGE_EXPIRY_WINDOW;
+use alloc::collections::BTreeMap;
 use alloy_primitives::ChainId;
-use kona_registry::HashMap;
 
 /// Configuration for a dependency of a chain
 #[derive(Debug, Clone, PartialEq, Eq)]
@@ -15,7 +15,7 @@ pub struct ChainDependency {}
 #[allow(clippy::zero_sized_map_values)]
 pub struct DependencySet {
     /// Dependencies information per chain.
-    pub dependencies: HashMap<ChainId, ChainDependency>,
+    pub dependencies: BTreeMap<ChainId, ChainDependency>,
 
     /// Override message expiry window to use for this dependency set.
     pub override_message_expiry_window: Option<u64>,
@@ -35,19 +35,19 @@ impl DependencySet {
 #[allow(clippy::zero_sized_map_values)]
 mod tests {
     use super::*;
+    use alloc::collections::BTreeMap;
     use alloy_primitives::ChainId;
-    use kona_registry::HashMap;
 
     const fn create_dependency_set(
-        dependencies: HashMap<ChainId, ChainDependency>,
+        dependencies: BTreeMap<ChainId, ChainDependency>,
         override_expiry: u64,
     ) -> DependencySet {
         DependencySet { dependencies, override_message_expiry_window: Some(override_expiry) }
     }
 
     #[test]
     fn test_get_message_expiry_window_default() {
-        let deps = HashMap::default();
+        let deps = BTreeMap::default();
         // override_message_expiry_window is 0, so default should be used
         let ds = create_dependency_set(deps, 0);
         assert_eq!(
@@ -59,7 +59,7 @@ mod tests {
 
     #[test]
     fn test_get_message_expiry_window_override() {
-        let deps = HashMap::default();
+        let deps = BTreeMap::default();
         let override_value = 12345;
         let ds = create_dependency_set(deps, override_value);
         assert_eq!(