Rust Contract SDK & Compiler

Two different things get called the Rust SDK. This page is about the miden crate and midenc, used to write account components, notes, and transaction scripts in Rust and compile them to MASM. The miden-client library — used to build applications that talk to a Miden node — is covered in Client Changes.

Component trait methods must now be marked #[account_procedure] to be part of the account interface, and #[account(..)] generates one trait per interface instead of inherent methods. Note also that compiler v0.10.1 pins protocol 0.16.0-rc.4, while the client and node use stable protocol v0.16.1. Both use the VM 0.29 line.

Quick Fix

// Before
#[component]
trait BasicWallet {
    fn receive_asset(&mut self, asset: Asset);
}

// After
#[component]
trait BasicWallet {
    #[account_procedure]
    fn receive_asset(&mut self, asset: Asset);
}

If you encounter errors, continue reading for detailed migration steps.

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Versions

The contract toolchain versions independently of the rest of the stack, and in this release it is genuinely behind.

Component	Version
midenc / compiler workspace	0.10.1
miden contract SDK crate (and miden-base-sys, miden-stdlib-sys, miden-sdk-alloc)	0.14.0
Protocol it builds against	0.16.0-rc.4
VM crates it builds against	0.29
MSRV	1.99 (plus a nightly toolchain)

Two consequences worth planning around:

• The MSRV is 1.99, higher than the 1.98.1 required by the client and protocol. Your toolchain must satisfy the highest requirement among the components you build.
• Because the toolchain pins protocol 0.16.0-rc.4, contract code compiled with it sees an earlier snapshot of the 0.16 protocol surface than a stable v0.16.1 client does. Both use VM 0.29; the skew is in the protocol API surface.

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Component methods must be marked #[account_procedure]

Summary

A #[component] trait's methods are no longer implicitly part of the account interface. Every method that must be callable from a note script, a transaction script, a foreign procedure invocation, or a sibling component now needs #[account_procedure] on the trait declaration, not on the impl.

#[auth_script] and #[account_procedure] cannot be combined in one component. An authentication component keeps using #[auth_script] alone; mixing them is a compile error. Like #[auth_script], #[account_procedure] is recognised by the enclosing #[component] macro and needs no import.

Affected Code

// Before
use miden::{Asset, NoteIdx, component, component_storage, output_note};

#[component]
trait BasicWallet {
    fn receive_asset(&mut self, asset: Asset);
    fn move_asset_to_note(&mut self, asset: Asset, note_idx: NoteIdx);
}

// After
use miden::{Asset, NoteIdx, NoteType, Recipient, Tag, component, component_storage, output_note};

#[component]
trait BasicWallet {
    #[account_procedure]
    fn receive_asset(&mut self, asset: Asset);

    #[account_procedure]
    fn move_asset_to_note(&mut self, asset: Asset, note_idx: NoteIdx);

    #[account_procedure]
    fn create_note(&mut self, tag: Tag, note_type: NoteType, recipient: Recipient) -> NoteIdx;
}

The impl block is unchanged — the attribute is not repeated there.

Migration Steps

1. For each #[component] trait, add #[account_procedure] above every method called from a note, a transaction script, FPI, or a sibling component.
2. Leave authentication components alone. They keep #[auth_script] and must not gain #[account_procedure].
3. Purely internal helper methods can stay unmarked.

The cargo miden new account template declares its method without #[account_procedure] while the sibling note and tx-script templates call it, and the full-project scaffold has the same gap. The repository's own examples/counter-contract does mark them. The template tests only build, never execute, so the gap is not caught by CI. If you scaffold a new project, add the attribute yourself rather than trusting the generated code.

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#[account(..)] generates one trait per interface

Summary

#[account(..)] used to generate the referenced component's methods as inherent methods on the wrapper struct. It now generates one trait per referenced interface, named after the interface, and implements it for the wrapper. This lets two components exporting the same method name coexist on one account.

Most single-component call sites are unchanged, but two situations break.

Affected Code

The wrapper struct may no longer share its name with a generated trait:

// Before — compiled
#[account(counter_contract::CounterContract)]
struct CounterContract;

// After — rename the wrapper
#[account(counter_contract::CounterContract)]
struct Counter;

let counter = Counter::new(counter_account_id);
let count = counter.get_count();

Cross-module call sites need the generated trait in scope. A #[note] or #[tx_script] entrypoint in the same module sees it automatically; a call site in a different module needs to import the trait, which is named after the interface:

use crate::BasicWallet;   // the generated trait, not the wrapper struct

Migration Steps

1. Rename any wrapper struct that collides with its interface name.
2. Import the generated trait at cross-module call sites.

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Other changes

• Transaction-kernel bindings were renamed and moved to track the protocol 0.16 surface, and several were removed.
• Kernel scalars are typed rather than raw Felt, so values that used to be interchangeable now need explicit conversion.
• AssetAmount is a validated fungible-amount type, matching the protocol and client surfaces.
• miden-project.toml requires an explicit path on [lib] and every [[bin]]. See VM & Assembler Changes.
• #[note] reserves get_entrypoint_root, so a note struct cannot define a method with that name, and note structs now implement ToFeltRepr.
• cargo miden new fetches templates from a release bundle rather than embedding them.

Additive in this line: typed transaction-script arguments, note constructors, and println!-style formatting.

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Common Errors

Error Message	Cause	Solution
A component method is not callable from a note or script	Missing #[account_procedure]	Add it to the trait method declaration.
Compile error combining auth and account attributes	They are mutually exclusive	Auth components keep #[auth_script] only.
Name collision between a wrapper struct and a trait	#[account(..)] now generates traits	Rename the wrapper.
no method named .. at a cross-module call site	The generated trait is not in scope	Import the trait named after the interface.
missing field path in miden-project.toml	Now mandatory	Add path to every target.
Toolchain version error	MSRV is 1.99 here	Use the higher of the stack's requirements.