Cairo Deploy

Cairo Deploy

Reference for deploying Cairo smart contracts to Starknet using sncast (Starknet Foundry).

When to Use

• Deploying contracts to Starknet devnet, Sepolia, or mainnet
• Declaring contract classes
• Setting up deployer accounts
• Configuring network endpoints
• Verifying deployed contracts
• Invoking/calling deployed contracts

When NOT to Use

• Writing or refactoring contract logic (cairo-contract-authoring).
• Unit, integration, or fuzz testing (cairo-testing).
• Gas or performance optimization (cairo-optimization).
• Security review of existing code (cairo-auditor).

Quick Start

1. Build with scarb build, then declare and deploy with sncast.
2. Use [skills catalog](../README.md) when the task moves back into authoring, testing, or auditing.

Setup

Install Starknet Foundry

# Install via asdf (recommended for version pinning)
asdf plugin add starknet-foundry
asdf install starknet-foundry 0.56.0
asdf global starknet-foundry 0.56.0

# Or install directly
curl -L https://raw.githubusercontent.com/foundry-rs/starknet-foundry/master/scripts/install.sh | sh
snfoundryup

.tool-versions

Pin versions for reproducible builds:

scarb 2.15.1
starknet-foundry 0.56.0

> Note: snforge 0.56.0 requires Scarb >= 2.12.0. Check github.com/foundry-rs/starknet-foundry/releases for the latest.

Build

# Build contracts (generates Sierra + CASM)
scarb build

Output goes to target/dev/:

• myproject_MyContract.contract_class.json (Sierra)
• myproject_MyContract.compiled_contract_class.json (CASM)

Account Setup

Create a New Account

# Generate account on Sepolia
sncast account create \
    --url https://starknet-sepolia.g.alchemy.com/v2/YOUR_KEY \
    --name my-deployer

# This outputs the account address — fund it with ETH/STRK before deploying

# Deploy the account contract
sncast account deploy \
    --url https://starknet-sepolia.g.alchemy.com/v2/YOUR_KEY \
    --name my-deployer

Import Existing Account

sncast account import \
    --url https://starknet-sepolia.g.alchemy.com/v2/YOUR_KEY \
    --name my-deployer \
    --address 0x123... \
    --private-key 0xabc... \
    --type oz

Account types: oz (OpenZeppelin), argent, braavos

sncast.toml

Configure defaults to avoid repeating flags:

[default]
url = "https://starknet-sepolia.g.alchemy.com/v2/YOUR_KEY"
account = "my-deployer"
accounts-file = "~/.starknet_accounts/starknet_open_zeppelin_accounts.json"
wait = true

[mainnet]
url = "https://starknet-mainnet.g.alchemy.com/v2/YOUR_KEY"
account = "mainnet-deployer"

Use profiles: sncast --profile mainnet declare ...

Declare (Register Class)

Before deploying, declare the contract class on-chain:

# Declare contract
sncast declare \
    --contract-name MyContract

# Output:
# class_hash: 0x1234...
# transaction_hash: 0xabcd...

If the class is already declared, sncast will tell you — that's fine, use the existing class hash.

Deploy (Create Instance)

# Deploy with constructor args
sncast deploy \
    --class-hash 0x1234... \
    --constructor-calldata 0xOWNER_ADDRESS

# Multiple constructor args (space-separated)
sncast deploy \
    --class-hash 0x1234... \
    --constructor-calldata 0xOWNER 0xTOKEN_ADDRESS 1000

Constructor Calldata Encoding

Arguments are passed as felt252 values:

• ContractAddress — pass as hex 0x123...
• u256 — pass as TWO felts: low high (e.g., 1000 0 for 1000)
• felt252 — pass directly
• bool — 1 for true, 0 for false
• ByteArray (strings) — use sncast's string encoding or pass raw

Invoke (Write)

# Call a write function
sncast invoke \
    --contract-address 0xCONTRACT \
    --function "transfer" \
    --calldata 0xRECIPIENT 1000 0

Call (Read)

# Call a view function (free, no tx)
sncast call \
    --contract-address 0xCONTRACT \
    --function "get_balance" \
    --calldata 0xACCOUNT

Programmatic Deployment (starknet.js)

import { Account, CallData, Contract, RpcProvider } from "starknet";

const provider = new RpcProvider({ nodeUrl: process.env.STARKNET_RPC! });
const account = new Account(provider, process.env.ACCOUNT_ADDRESS!, process.env.PRIVATE_KEY!);

const declareTx = await account.declare({ contract: compiledSierra, casm: compiledCasm });
await provider.waitForTransaction(declareTx.transaction_hash);

const deployTx = await account.deploy({
  classHash: declareTx.class_hash,
  constructorCalldata: CallData.compile({ owner: process.env.OWNER! }),
});
await provider.waitForTransaction(deployTx.transaction_hash);

const contract = new Contract(abi, deployTx.contract_address[0], provider).connect(account);
await contract.invoke("set_fee", [10]);
const fee = await contract.call("get_fee", []);
console.log({ fee });

Multicall

Execute multiple calls in a single transaction:

# Create a multicall file
cat > multicall.toml  **Note:** `sncast verify` supports both Walnut and Voyager backends. Use `--verifier walnut` or `--verifier voyager` explicitly.

## Upgradeable Contracts

For contracts using OZ UpgradeableComponent:

```bash
# 1. Declare new class
sncast declare --contract-name MyContractV2

# 2. Call upgrade on existing contract
sncast invoke \
    --contract-address 0xEXISTING_CONTRACT \
    --function "upgrade" \
    --calldata 0xNEW_CLASS_HASH

Common Errors

| Error | Cause | Fix | |-------|-------|-----| | Contract not found | Account not deployed | Run sncast account deploy | | Insufficient max fee | Not enough ETH/STRK for gas | Fund the deployer account | | Class already declared | Same class hash exists | Use the existing class hash for deploy | | Entry point not found | Wrong function name | Check the contract ABI | | Invalid calldata | Wrong number/type of args | Check constructor signature, remember u256 = 2 felts |

Source & license

This open-source skill is cataloged on AgentStack and links to its original source — we do not rehost the code.

• Author: keep-starknet-strange
• Source: keep-starknet-strange/starknet-agentic
• License: MIT
• Homepage: https://starknet-agentic.com

Install and usage instructions live in the source repository linked above.