name	compact
description	Write privacy-preserving smart contracts in Compact (Minokawa) for Midnight Network. Use when creating contracts, defining types, using standard library functions, or implementing ZK patterns. Triggers on Compact language, circuits, ledger state, hashing, or zero-knowledge contract questions.
metadata	[object Object]

Compact Smart Contracts

Name: compact
Author: FractionEstate

Compact (being renamed to Minokawa) is Midnight's domain-specific language for privacy-preserving smart contracts. Contracts compile to ZK-SNARKs, enabling selective disclosure of data.

Note: As of compiler v0.26.0, the language is being renamed from "Compact" to "Minokawa" under the Linux Foundation Decentralized Trust. The toolchain commands still use compact.

Quick Start

pragma language_version 0.18;

export ledger message: Opaque<"string">;

export circuit setMessage(input: Opaque<"string">): [] {
  message = disclose(input);  // Makes private input public
}

Contract Structure

Every Compact contract has three parts:

Pragma - Language version (pragma language_version 0.18;)
Ledger - On-chain state declarations
Circuits - ZK-proven functions

Core Concepts

Privacy Model

Level	Syntax	Visibility
Private	`const x = input;`	Only prover
Disclosed	`disclose(value)`	Allowed to become public
Proven	`disclose(a >= b)`	Public boolean only
Witness	`witness f(...): T;`	Private, DApp-provided

Notes:

Circuit arguments and witness returns are treated as potentially private (“witness data”).
disclose(...) is a compiler acknowledgement: it does not itself publish anything, it just permits an expression to flow into public outputs (ledger writes / exported circuit returns / cross-contract comms).
Only Opaque<"string"> and Opaque<"Uint8Array"> are currently supported.

Ledger Types

ledger counter: Counter;           // Auto-incrementing
ledger balances: Map<Bytes<32>, Uint<64>>;  // Key-value
ledger members: Set<Field>;        // Membership tracking
ledger tree: MerkleTree<20, Field>;  // Cryptographic proofs

Reference Files

Topic	Resource
Type System	references/types.md - Full type reference
Standard Library	references/stdlib.md - Hashing, coins, EC ops
VS Code extension	references/vscode-extension.md - Editor setup and tasks
Ledger Patterns	references/ledger-patterns.md - State management
Advanced Patterns	references/advanced-patterns.md - Access control, state machines
Detailed API Patterns	references/detailed-api-patterns.md - API, code

Templates

Template	Description
assets/basic-contract.compact	Simple ledger + circuit
assets/token-contract.compact	Token with transfers
assets/private-voting.compact	Anonymous voting
assets/commitment-reveal.compact	Commit-reveal pattern

Compilation

# Compile contract
compact compile contracts/my-contract.compact contracts/managed/my-contract

# Output structure
contracts/managed/my-contract/
├── contract/    # JSON artifacts
├── keys/        # ZK proving/verifying keys
└── zkir/        # ZK Intermediate Representation

Common Errors

Error	Cause	Fix
`Type mismatch`	Wrong bit width	Use correct `Uint<N>` size
`Cannot assign private to public`	Missing disclose	Add `disclose()` wrapper
`Undefined symbol`	Import missing	Check pragma and imports

Best Practices

✅ Start with pragma language_version 0.18;
✅ Use witness for private inputs that need proofs
✅ Choose smallest Uint<N> that fits your data
✅ Use persistentHash for on-chain data, transientHash for temp
❌ Don't expose secrets via disclose() unnecessarily
❌ Avoid large state (increases gas costs)

compact

Install Skill

SKILL.md