Account Changes

Storage is now name-based, not index-based. All storage access code must be updated.

Quick Fix

Replace numeric indices with StorageSlotName:

src/account.rs

// Before
let value = account.storage().get_item(0)?;

// After
let slot_name = StorageSlotName::new("my_component::my_slot")?;
let value = account.storage().get_item(&slot_name)?;

---

Named Storage Slots

Replace index-based storage access with StorageSlotName identifiers.

Rust

src/account.rs

- // Before: access by numeric index
- let value = account.storage().get_item(0)?;
- let _old_value = account.storage_mut().set_item(0, new_value)?;

+ // After: access by name
+ let slot_name = StorageSlotName::new("my_component::my_slot")?;
+ let value = account.storage().get_item(&slot_name)?;
+ let _old_value = account.storage_mut().set_item(&slot_name, new_value)?;

MASM Updates

The native_account::set_map_item procedure now takes slot IDs and returns only old values:

src/contract.masm

- # Before
- exec.native_account::set_map_item
- # Returns: [OLD_MAP_ROOT, OLD_VALUE, ...]

+ # After
+ # Inputs: [slot_id_prefix, slot_id_suffix, KEY, NEW_VALUE]
+ exec.native_account::set_map_item
+ # Returns: [OLD_VALUE, ...]

The return value change means you may need to update stack manipulation after calling set_map_item.

---

Keystore Changes

Remove RNG generics from FilesystemKeyStore:

src/client.rs

- use miden_client::keystore::FilesystemKeyStore;
- let keystore = FilesystemKeyStore::<rand::rngs::StdRng>::new(path)?;

+ use miden_client::keystore::FilesystemKeyStore;
+ let keystore = FilesystemKeyStore::new(path)?;

---

Web Component Compilation

Web component compilation now requires AccountComponentCode from CodeBuilder:

src/component.ts

- // Before
- const component = AccountComponent.compile(accountCode, builder, [slot]);

+ // After
+ const componentCode = builder.compileAccountComponentCode(accountCode);
+ const component = AccountComponent.compile(componentCode, [slot]);

---

Storage Schemas

Replace AccountComponentTemplate with metadata-driven StorageSchema:

src/schema.rs

- use miden_lib::AccountComponentTemplate;
- let template = AccountComponentTemplate::new(slots)?;

+ use miden_protocol::account::component::{SchemaTypeId, StorageSchema, StorageSlotSchema};
+ use miden_protocol::account::StorageSlotName;
+ let schema = StorageSchema::new([
+     (
+         StorageSlotName::new("my_component::balance")?,
+         StorageSlotSchema::value("balance", SchemaTypeId::native_word()),
+     ),
+     (
+         StorageSlotName::new("my_component::metadata")?,
+         StorageSlotSchema::map(
+             "metadata",
+             SchemaTypeId::native_word(),
+             SchemaTypeId::native_word(),
+         ),
+     ),
+ ])?;

---

Procedure Roots

Use AccountProcedureRoot instead of AccountProcedureInfo:

src/procedure.rs

- use miden_objects::account::AccountProcedureInfo;
- let info = AccountProcedureInfo::new(digest, storage_offset)?;

+ use miden_protocol::account::AccountProcedureRoot;
+ let root = AccountProcedureRoot::from_raw(digest);

---

Migration Steps

1. Identify all storage slot access patterns in your code
2. Define StorageSlotName constants for each slot
3. Update storage access to use names instead of indices
4. Remove RNG type parameters from keystore initialization
5. Update component compilation to use CodeBuilder
6. Migrate storage templates to StorageSchema
7. Replace AccountProcedureInfo with AccountProcedureRoot

---

Common Errors

Error	Cause	Fix
expected &StorageSlotName, found u8	API changed to names	Use StorageSlotName
FilesystemKeyStore expects 0 type parameters	RNG generic removed	Remove type parameter
AccountComponentTemplate not found	Renamed	Use StorageSchema