ARBuilder: Cursor rule for Cursor

ARBuilder Development Rules for Cursor

Stylus SDK Version Information (CRITICAL - ALWAYS USE THESE)

Current stable versions (as of January 2025):

• stylus-sdk: 0.9.2 (use this for new projects)
• alloy-primitives: =0.8.20
• alloy-sol-types: =0.8.20
• Rust version: 1.81 (1.82+ may have compatibility issues)
• cargo-stylus CLI: 0.5.x

Cargo.toml Template

[dependencies]
stylus-sdk = "0.9.2"
alloy-primitives = "=0.8.20"
alloy-sol-types = "=0.8.20"

[lib]
crate-type = ["cdylib"]

[profile.release]
codegen-units = 1
strip = true
lto = true
panic = "abort"
opt-level = "s"

Arbitrum SDK Version Information

• @arbitrum/sdk: ^4.0.0
• ethers: ^5.7.0 (NOT v6 - SDK requires ethers v5)

Stylus Contract Best Practices

Required Attributes

#![cfg_attr(not(any(feature = "export-abi", test)), no_std)]
#![cfg_attr(not(test), no_main)]
extern crate alloc;

Storage Pattern

use stylus_sdk::prelude::*;
use alloy_primitives::{U256, Address};

sol_storage! {
    #[entrypoint]
    pub struct MyContract {
        uint256 value;
        mapping(address => uint256) balances;
    }
}

Public Methods

#[public]
impl MyContract {
    pub fn get_value(&self) -> U256 {
        self.value.get()
    }

    pub fn set_value(&mut self, new_value: U256) {
        self.value.set(new_value);
    }
}

Key Constraints

• 24KB size limit (Brotli-compressed WASM)
• No floating point operations allowed
• Yearly reactivation required for deployed contracts
• Use alloc::vec::Vec instead of std::vec::Vec
• Use alloc::string::String instead of std::string::String

Common Pitfalls to Avoid

1. Using std library features (use alloc or core instead)
2. Floating point math (use fixed-point or integer math)
3. Forgetting #[entrypoint] attribute on main struct
4. Not handling storage slots correctly in upgrades
5. Using Rust 1.82+ (stick to 1.81)

Arbitrum Bridging Best Practices