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

Not for: Writing contracts (use cairo-contracts), testing (use cairo-testing), optimization (use cairo-optimization)

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 add \
    --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

Multicall

Execute multiple calls in a single transaction:

# Create a multicall file
cat > multicall.toml << 'EOF'
[[call]]
call_type = "deploy"
class_hash = "0x1234..."
inputs = ["0xOWNER"]

[[call]]
call_type = "invoke"
contract_address = "0xTOKEN"
function = "approve"
inputs = ["0xSPENDER", "1000", "0"]
EOF

sncast multicall run --path multicall.toml

Deploy Script Pattern

For complex deployments, use a script:

#!/bin/bash
set -euo pipefail

RPC_URL="https://starknet-sepolia.g.alchemy.com/v2/YOUR_KEY"
ACCOUNT="my-deployer"

echo "Building..."
scarb build

echo "Declaring MyToken..."
TOKEN_CLASS=$(sncast declare --contract-name MyToken --url $RPC_URL --account $ACCOUNT | grep "class_hash" | awk '{print $2}')
echo "Token class: $TOKEN_CLASS"

echo "Deploying MyToken..."
TOKEN_ADDR=$(sncast deploy --class-hash $TOKEN_CLASS --constructor-calldata 0xOWNER --url $RPC_URL --account $ACCOUNT | grep "contract_address" | awk '{print $2}')
echo "Token deployed at: $TOKEN_ADDR"

echo "Declaring AMM..."
AMM_CLASS=$(sncast declare --contract-name AMM --url $RPC_URL --account $ACCOUNT | grep "class_hash" | awk '{print $2}')

echo "Deploying AMM..."
AMM_ADDR=$(sncast deploy --class-hash $AMM_CLASS --constructor-calldata $TOKEN_ADDR --url $RPC_URL --account $ACCOUNT | grep "contract_address" | awk '{print $2}')
echo "AMM deployed at: $AMM_ADDR"

echo "Done. Addresses:"
echo "  Token: $TOKEN_ADDR"
echo "  AMM:   $AMM_ADDR"

Network Endpoints

Alternative providers: Infura, Blast, Nethermind (free tier available).

Local Devnet

# Install and run starknet-devnet-rs
cargo install starknet-devnet
starknet-devnet --seed 42

# Devnet provides pre-funded accounts — use them for testing

Contract Verification

Verify source code on Voyager or Starkscan:

# Verify on Voyager (manual: upload Sierra JSON via web UI)
# https://sepolia.voyager.online/contract/0xADDRESS#code

# Or use Walnut for programmatic verification
# https://app.walnut.dev

Note: sncast verify currently only supports the Walnut verification backend. Voyager and Starkscan verification must be done through their respective web UIs.

Upgradeable Contracts

For contracts using OZ UpgradeableComponent:

# 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