allset-sdk

AllSet SDK (@fastxyz/allset-sdk) — TypeScript SDK for bridging tokens between Fast and EVM chains. Provides deposit (EVM → Fast), withdraw (Fast → EVM), and custom intent execution.

GitHub: fastxyz/fast-sdk

What You Can Do

AllSet is the bridge SDK for moving tokens between the Fast payment network and EVM-compatible chains. Use it when you need to:

• Deposit tokens into Fast — move tokens from an EVM chain (Ethereum, Arbitrum, Base, etc.) onto the Fast network for fast, low-cost payments

• Withdraw tokens from Fast — move tokens from Fast back to an EVM chain to access DeFi, CEXs, or external services

• Execute custom intents — define arbitrary EVM operations (swap, supply, any contract call) that get executed on your behalf on the destination chain after funds settle on Fast

AllSet is designed to be pure — no embedded chain configs, no environment variables, no file system access. You pass all addresses, RPC URLs, and credentials explicitly, making it easy to test and predictable in any environment.

Installation

Install from npm as @fastxyz/allset-sdk. The package README on GitHub includes the current install command, dependency expectations, and integration examples.

Architecture

AllSet bridges two ecosystems: EVM chains and the Fast payment network. The key abstraction is the intent — a declaration of what you want to happen on the destination chain, paired with funds on Fast to pay for it.

Function	Role
createEvmWallet()	Creates an EVM wallet from a private key, or generates a fresh random wallet for one-time bridging operations
createEvmExecutor()	Creates a viem PublicClient + WalletClient bound to a specific EVM chain
executeDeposit()	Locks tokens on the EVM chain and issues a corresponding balance on Fast
executeWithdraw()	Releases or debits tokens on Fast and unlocks them on the destination EVM chain
executeIntent()	Combines a Fast-side token transfer with a predefined EVM execution plan; the intent is processed by the AllSet payment processor

Supported Chains

Chain	Chain ID	Role in AllSet
Ethereum Mainnet	1	Primary production EVM endpoint
Sepolia	11155111	Testnet for EVM side
Arbitrum	42161	L2 deposit target
Arbitrum Sepolia	421614	Testnet for L2 side
Base	8453	L2 deposit target

How Deposits Work (EVM → Fast)

Depositing moves value from an EVM chain onto Fast. The tokens are locked in a lock contract on the EVM side, and an equivalent amount is issued or credited on Fast.

User EVM wallet
    │
    │  executeDeposit()
    │  ── tokens sent to lock contract on EVM
    ▼
EVM Lock Contract (holds tokens)
    │
    │  Payment processor detects event on EVM, submits to Fast
    ▼
Fast Network (credits user's Fast account)
    │
    │  Now usable for Fast-native fast/cheap payments
    ▼
User Fast account (via fast-sdk)

Key properties:

• Deposits require EVM gas — budget for that in your UX

• Finality on Fast is fast (seconds), but EVM event observation takes 1-3 minutes depending on chain

• Track deposit progress using the response returned by the SDK together with your application or relayer-side status handling

How Withdrawals Work (Fast → EVM)

Withdrawing moves value from Fast back to an EVM chain. Tokens are released or debited on Fast, and the AllSet payment processor submits a transaction on the EVM destination chain to release the tokens to your wallet.

User Fast account
    │
    │  executeWithdraw()
    │  ── tokens debited on Fast
    ▼
AllSet Payment Processor (detects Fast event)
    │
    │  Submits release transaction on EVM destination chain
    ▼
EVM destination wallet (tokens arrive)

Key properties:

• Withdrawals are asynchronous — the Fast side settles quickly, but EVM delivery depends on payment processor queuing and EVM gas

• The payment processor takes a small fee in FAST for the forwarding service

• Use the returned order identifier to track payment status in your integration

How Custom Intents Work

Intents unlock powerful composeability. Instead of just bridging tokens, you can specify what should happen on the destination EVM chain — a swap, a lending deposit, a specific contract call — and AllSet executes it automatically after your Fast funds are credited.

User Fast account
    │
    │  executeIntent()
    │  ── funds debited on Fast, intent registered
    ▼
Fast Network (credits funds, intent detected)
    │
    │  Payment processor detects intent on Fast
    ▼
Payment Processor (executes EVM operation)
    │
    │  Submits intent execution on EVM destination chain
    ▼
EVM destination (swap, deposit, contract call — result)

The payment processor detects the intent on Fast, credits the funds, and executes the described operation on the EVM destination chain — all as one atomic cross-chain workflow from the user's perspective. For intent examples with complete code, see the AllSet SDK README on GitHub.

Design Principles

All functions are pure — the SDK never reads from process.env, never reads a config file, and never embeds chain IDs or contract addresses. This means:

• You control exactly which chain and contract addresses your app uses

• Tests can swap in mock executors without SDK changes

• No surprises when new chains are added — you opt in explicitly

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For complete API documentation, runnable examples for deposits, withdrawals, and intents, and current configuration details, see the AllSet SDK README on GitHub.