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Arc Chain Notes (researched 2026-07-11 from docs.arc.io)

Source of truth for all chain-specific values used in app/src/config/chain.ts and contracts/script/config/. Do not hardcode these values anywhere else.

Network — Arc Testnet

Item Value
Chain ID 5042002
Network name Arc Testnet
RPC (primary) https://rpc.testnet.arc.network
RPC (alternates) https://rpc.blockdaemon.testnet.arc.network, https://rpc.drpc.testnet.arc.network, https://rpc.quicknode.testnet.arc.network
WebSocket wss://rpc.testnet.arc.network
Block explorer https://testnet.arcscan.app
Native currency USDC (symbol USDC, 18 decimals at the native layer)
Faucet https://faucet.circle.com (select Arc Testnet)
Finality Deterministic and instant — a tx is final on inclusion
Block time ~0.5s, 30M gas/block

Mainnet addresses/config are not yet published by Circle.

Key contract addresses (Arc Testnet)

Contract Address Notes
USDC (ERC-20 interface) 0x3600000000000000000000000000000000000000 ERC-20 view over the native USDC balance. 6 decimals. This is the token Rota contracts use.
EURC 0x89B50855Aa3bE2F677cD6303Cec089B5F319D72a 6 decimals
Multicall3 0xcA11bde05977b3631167028862bE2a173976CA11 standard address — wagmi/viem batching works
CREATE2 Factory 0x4e59b44847b379578588920cA78FbF26c0B4956C standard deterministic deployer — forge script works normally
Permit2 0x000000000022D473030F116dDEE9F6B43aC78BA3 future: gasless approvals
TokenMessengerV2 (CCTP) 0x8FE6B999Dc680CcFDD5Bf7EB0974218be2542DAA future: cross-chain deposits
GatewayWallet 0x0077777d7EBA4688BDeF3E311b846F25870A19B9 future: App Kit Unified Balance

Gas & fees

  • Gas is paid in USDC (the native token). Internally 18 decimals; the ERC-20 interface truncates to 6. Same underlying balance — a wallet funded from the faucet can both pay gas and hold ERC-20 USDC.
  • EIP-1559 with EWMA smoothing. Testnet floor 20 gwei, ceiling 20,000 gwei; a normal tx targets ~$0.01. Set maxFeePerGas ≥ 20 gwei; a 0–1 gwei priority tip is enough.
  • Base fee goes to the block beneficiary, not burned.
  • Standard EIP-1559 tooling (Foundry, viem) works unmodified. UX guidance from Circle: show fees in dollar terms, not gwei.

EVM differences that matter to Rota

  • block.prevrandao always returns 0 — never use it for randomness. Rota's RANDOM_ORDER mode uses blockhash(block.number - 1) mixed with the circle address and member set; documented as manipulable-in-theory, VRF is future work.
  • Block timestamps are non-decreasing (not strictly increasing). Rota only compares >= / > against stored deadlines, which is safe.
  • No blob txs (EIP-4844). CREATE2, EIP-7702 work as on Ethereum.
  • Native USDC transfers can revert for blocklisted/zero addresses; Rota only moves the ERC-20 interface via SafeERC20, so standard ERC-20 semantics apply.
  • ERC-20 balanceOf truncates the 18-dec native balance to 6 decimals.

App Kit (future integration points — out of MVP scope)

  • Package: @circle-fin/app-kit + @circle-fin/adapter-viem-v2.
  • Unified Balance: chain-abstracted USDC balance — would let a member in Dubai fund a Dhaka circle from any chain without manual bridging (docs: /app-kit/unified-balance).
  • Bridge (CCTP v2): programmatic USDC movement across chains (docs: /app-kit/bridge).
  • Swap / Send also available. All are one-method calls against an adapter.

Rota deployment on Arc Testnet (2026-07-12)

Redeployed with the 2026-07 audit fixes (blacklist-proof payouts, deferred giving, early-exit gate, reputation caps, locked implementations — see SECURITY.md). Deployed with pnpm deploy:arc (script/DeployArc.s.sol); the canonical record is contracts/deployments/arc.json (synced to app/src/config/deployments.arc.json). Full deploy cost ≈ 0.12 USDC in gas at ~41 gwei (5 txs).

Contract Address
RotaFactory 0x7d455FDBB89dD631F37D6BE152e97b567050ce88
ReputationRegistry 0xD4dad0f7c39d9DF9F06d10DD69431C40CC38e0E3
RotaCircle implementation 0xDd28e4243de63745eb67e9a51c925d21de3AbB73
GoalPot implementation 0xa823a67745ae861f620763963673D73bD5058b30

Post-deploy verification (all live on https://rpc.testnet.arc.network): factory.registry() ↔ registry.factory() point at each other, both implementation getters match the JSON, USDC at 0x3600…0000 reports symbol()=USDC / decimals()=6.

Previous deployment (2026-07-11, pre-audit — superseded, do not use): factory 0xFafC67365e7dA77BF4c441C3DD29bAB57cD5CaAa, registry 0xc7919F673f9886Eec01511ce66B7fBD23EA835E5.

Placeholders

None required — every value above was found in the official docs. If mainnet ships, add its values here first, then to app/src/config/chain.ts.