Poly-pay · gianalarcon · Jun 10, 2026 · Jun 10, 2026 · Jun 10, 2026 · Jun 10, 2026
diff --git a/packages/backend/src/common/constants/campaign.ts b/packages/backend/src/common/constants/campaign.ts
@@ -15,8 +15,8 @@ export const QUEST_POINTS_ACCOUNT_FIRST_TX = 100;
 export const QUEST_POINTS_SUCCESSFUL_TX = 50;
 
 // Supported chain IDs
-// 421614 = Arbitrum Sepolia (testnet only; account contract is the Stylus port).
-export const SUPPORTED_CHAIN_IDS = [2651420, 84532, 26514, 8453, 421614];
+// 421614 = Arbitrum Sepolia, 42161 = Arbitrum One (account contract is the Stylus port).
+export const SUPPORTED_CHAIN_IDS = [2651420, 84532, 26514, 8453, 421614, 42161];
 
 // External APIs
 export const COINGECKO_API_URL =

diff --git a/packages/backend/src/common/constants/proof.ts b/packages/backend/src/common/constants/proof.ts
@@ -4,4 +4,5 @@ export const DOMAIN_ID_BY_CHAIN_ID = {
   421614: 4, // Arbitrum Sepolia (zkVerify testnet domain)
   26514: 3, // Horizen mainnet
   8453: 2, // Base mainnet
+  42161: 10, // Arbitrum One (zkVerify System Domain, verified docs.zkverify.io)
 } as const;
diff --git a/packages/hardhat/hardhat.config.ts b/packages/hardhat/hardhat.config.ts
@@ -62,7 +62,8 @@ const config: HardhatUserConfig = {
       accounts: [deployerPrivateKey],
     },
     arbitrum: {
-      url: `https://arb-mainnet.g.alchemy.com/v2/${providerApiKey}`,
+      // Default Alchemy key is IP-whitelisted; use the public RPC unless overridden.
+      url: process.env.ARBITRUM_RPC || "https://arb1.arbitrum.io/rpc",
       accounts: [deployerPrivateKey],
     },
     arbitrumSepolia: {

diff --git a/packages/nextjs/components/NewAccount/ChooseNetwork.tsx b/packages/nextjs/components/NewAccount/ChooseNetwork.tsx
@@ -2,6 +2,7 @@
 
 import React from "react";
 import Image from "next/image";
+import { CHAIN_IDS } from "@polypay/shared";
 import { getDefaultChainId, getNetworkMeta } from "~~/utils/network";
 import { notification } from "~~/utils/scaffold-eth";
 
@@ -14,10 +15,7 @@ interface ChooseNetworkProps {
   isWalletConnected: boolean;
 }
 
-const HORIZEN_MAINNET = 26514;
-const BASE_MAINNET = 8453;
-// Arbitrum is testnet-only (zkVerify has no Arbitrum One mainnet verifier yet).
-const ARBITRUM_SEPOLIA = 421614;
+const { HORIZEN_MAINNET, HORIZEN_TESTNET, BASE_MAINNET, BASE_SEPOLIA, ARBITRUM_ONE, ARBITRUM_SEPOLIA } = CHAIN_IDS;
 
 const ChooseNetwork: React.FC<ChooseNetworkProps> = ({
   className,
@@ -29,13 +27,12 @@ const ChooseNetwork: React.FC<ChooseNetworkProps> = ({
 }) => {
   const defaultChainId = getDefaultChainId();
 
-  const isTestnet = defaultChainId === 2651420;
+  const isTestnet = defaultChainId === HORIZEN_TESTNET;
 
   const networks = [
-    { chainId: HORIZEN_MAINNET, fallbackChainId: 2651420 },
-    { chainId: BASE_MAINNET, fallbackChainId: 84532 },
-    // Arbitrum has no mainnet entry; only surfaced on testnet.
-    ...(isTestnet ? [{ chainId: ARBITRUM_SEPOLIA, fallbackChainId: ARBITRUM_SEPOLIA }] : []),
+    { chainId: HORIZEN_MAINNET, fallbackChainId: HORIZEN_TESTNET },
+    { chainId: BASE_MAINNET, fallbackChainId: BASE_SEPOLIA },
+    { chainId: ARBITRUM_ONE, fallbackChainId: ARBITRUM_SEPOLIA },
   ].map(n => {
     // If we are on testnet env, use testnet ids instead
     const chainId = isTestnet ? n.fallbackChainId : n.chainId;

diff --git a/packages/nextjs/components/Sidebar/NetworkChooserSidebar.tsx b/packages/nextjs/components/Sidebar/NetworkChooserSidebar.tsx
@@ -12,8 +12,7 @@ interface NetworkChooserSidebarProps {
   onSelectNetwork: (chainId: number | null) => void;
 }
 
-const NETWORKS_MAINNET = [26514, 8453];
-// Arbitrum Sepolia (421614) is testnet-only — no Arbitrum One mainnet entry.
+const NETWORKS_MAINNET = [26514, 8453, 42161];
 const NETWORKS_TESTNET = [2651420, 84532, 421614];
 
 export default function NetworkChooserSidebar({ isOpen, accounts, onSelectNetwork }: NetworkChooserSidebarProps) {

diff --git a/packages/nextjs/scaffold.config.ts b/packages/nextjs/scaffold.config.ts
@@ -68,10 +68,9 @@ const scaffoldConfig = {
   // The networks on which your DApp is live
   // targetNetworks: [chains.sepolia],
   // targetNetworks: [chains.hardhat],
-  // Arbitrum is testnet-only: zkVerify has a verifier on Arbitrum Sepolia but not Arbitrum One.
   targetNetworks:
     process.env.NEXT_PUBLIC_NETWORK === NetworkValue.mainnet
-      ? [horizenMainnet, chains.base]
+      ? [horizenMainnet, chains.base, chains.arbitrum]
       : [horizenTestnet, chains.baseSepolia, chains.arbitrumSepolia],
   // The interval at which your front-end polls the RPC servers for new data (it has no effect if you only target the local network (default is 4000))
   pollingInterval: RPC_POLLING_INTERVAL,

diff --git a/packages/nextjs/utils/network.ts b/packages/nextjs/utils/network.ts
@@ -29,7 +29,12 @@ const NETWORK_META_BY_CHAIN_ID: Record<number, NetworkMeta> = {
     icon: "/token/base.svg",
     badge: "/token/base.svg",
   },
-  // Arbitrum (testnet only). Add /token/arbitrum.svg asset for the icon/badge.
+  // Arbitrum
+  42161: {
+    name: "Arbitrum",
+    icon: "/token/arbitrum.svg",
+    badge: "/token/arbitrum.svg",
+  },
   421614: {
     name: "Arbitrum Sepolia",
     icon: "/token/arbitrum.svg",

diff --git a/packages/shared/src/chains/arbitrumOne.ts b/packages/shared/src/chains/arbitrumOne.ts
@@ -0,0 +1,6 @@
+import { arbitrum } from "viem/chains";
+
+// Re-export viem's Arbitrum One (42161) chain definition for consistency with
+// the other chains module. On Arbitrum the account contract is the Stylus
+// (Rust/WASM) port of MetaMultiSigWallet (same as Arbitrum Sepolia).
+export { arbitrum as arbitrumOne };
diff --git a/packages/shared/src/chains/index.ts b/packages/shared/src/chains/index.ts
@@ -3,13 +3,15 @@ import { horizenMainnet } from "./horizenMainnet";
 import { baseSepolia } from "./baseSepolia";
 import { baseMainnet } from "./baseMainnet";
 import { arbitrumSepolia } from "./arbitrumSepolia";
+import { arbitrumOne } from "./arbitrumOne";
 
 export {
   horizenTestnet,
   horizenMainnet,
   baseSepolia,
   baseMainnet,
   arbitrumSepolia,
+  arbitrumOne,
 };
 
 export type NetworkType = "testnet" | "mainnet";
@@ -38,6 +40,8 @@ export const getChainById = (chainId: number) => {
       return baseMainnet;
     case arbitrumSepolia.id:
       return arbitrumSepolia;
+    case arbitrumOne.id:
+      return arbitrumOne;
     default:
       throw new Error(`Unsupported chainId: ${chainId}`);
   }

diff --git a/packages/shared/src/constants/chains.ts b/packages/shared/src/constants/chains.ts
@@ -0,0 +1,12 @@
+// Single source of truth for the EVM chain IDs PolyPay supports.
+// Reuse these everywhere instead of redeclaring magic numbers.
+export const CHAIN_IDS = {
+  HORIZEN_MAINNET: 26514,
+  HORIZEN_TESTNET: 2651420,
+  BASE_MAINNET: 8453,
+  BASE_SEPOLIA: 84532,
+  ARBITRUM_ONE: 42161,
+  ARBITRUM_SEPOLIA: 421614,
+} as const;
+
+export type SupportedChainId = (typeof CHAIN_IDS)[keyof typeof CHAIN_IDS];
diff --git a/packages/shared/src/constants/index.ts b/packages/shared/src/constants/index.ts
@@ -1,5 +1,6 @@
 export * from "./socket-events";
 export * from "./room";
+export * from "./chains";
 export * from "./token";
 export * from "./campaign";
 export * from "./contract";
diff --git a/packages/shared/src/constants/token.ts b/packages/shared/src/constants/token.ts
@@ -1,3 +1,5 @@
+import { CHAIN_IDS } from "./chains";
+
 export type TokenAddresses = Record<number, string>;
 
 export interface Token {
@@ -15,20 +17,23 @@ export interface ResolvedToken extends Omit<Token, "addresses"> {
 
 export const ZERO_ADDRESS = "0x0000000000000000000000000000000000000000";
 
-// Chain IDs
-const HORIZEN_MAINNET = 26514;
-const HORIZEN_TESTNET = 2651420;
-const BASE_MAINNET = 8453;
-const BASE_SEPOLIA = 84532;
-// Arbitrum is testnet-only in PolyPay (zkVerify has no Arbitrum One verifier).
-const ARBITRUM_SEPOLIA = 421614;
+// Chain IDs (single source of truth in ./chains).
+const {
+  HORIZEN_MAINNET,
+  HORIZEN_TESTNET,
+  BASE_MAINNET,
+  BASE_SEPOLIA,
+  ARBITRUM_SEPOLIA,
+  ARBITRUM_ONE,
+} = CHAIN_IDS;
 
 const ALL_CHAIN_IDS = [
   HORIZEN_MAINNET,
   HORIZEN_TESTNET,
   BASE_MAINNET,
   BASE_SEPOLIA,
   ARBITRUM_SEPOLIA,
+  ARBITRUM_ONE,
 ];
 
 export const NATIVE_ETH: Token = {
@@ -80,6 +85,8 @@ export const USDC_TOKEN: Token = {
     [BASE_SEPOLIA]: "0x036CbD53842c5426634e7929541eC2318f3dCF7e",
     // Circle official USDC on Arbitrum Sepolia (source: developers.circle.com).
     [ARBITRUM_SEPOLIA]: "0x75faf114eafb1BDbe2F0316DF893fd58CE46AA4d",
+    // Circle native USDC on Arbitrum One (NOT bridged USDC.e; source: developers.circle.com).
+    [ARBITRUM_ONE]: "0xaf88d065e77c8cC2239327C5EDb3A432268e5831",
   },
   symbol: "USDC",
   name: "USD Coin",

diff --git a/packages/shared/src/contracts/MetaMultiSigWalletStylus.ts b/packages/shared/src/contracts/MetaMultiSigWalletStylus.ts
@@ -22,6 +22,7 @@
 // Chains whose account contract is the Stylus port instead of the EVM .sol one.
 export const STYLUS_CHAIN_IDS: readonly number[] = [
   421614, // Arbitrum Sepolia
+  42161, // Arbitrum One
 ];
 
 export const isStylusChain = (chainId: number): boolean =>

diff --git a/packages/shared/src/contracts/contracts-config.ts b/packages/shared/src/contracts/contracts-config.ts
@@ -43,13 +43,26 @@ export const CONTRACT_CONFIG_BY_CHAIN_ID = {
     // Current build: original STATICCALL-based Poseidon (uses the on-chain
     // poseidon-solidity PoseidonT3 library at `poseidonT3Address`). The
     // in-process Rust Poseidon experiment was reverted — see NOTES.md.
-    stylusImplAddress: "0x0395b99f3a45bd08d018d3d3060a0e2bf8dc8978",
+    stylusImplAddress: "0x61fddf7cde02d4527b7d1086671d3f948e59f1d1",
     // Stylus/Rust EIP-1167 factory (packages/stylus-factory) bound to the
     // STATICCALL-Poseidon impl above. Emits byte-identical proxy bytecode to
     // the previous Solidity factory, so accounts created here are
     // indistinguishable on-chain from accounts created against the legacy
     // factory.
-    stylusFactoryAddress: "0xc35c0693286ebdc18bdf257f102dec9632a7ce77",
+    stylusFactoryAddress: "0x73d33f803600087ed1259035f9ff46f16f15c11a",
+  },
+  42161: {
+    // Arbitrum One mainnet. Account contract is the Stylus (Rust/WASM) port,
+    // same as Arbitrum Sepolia. zkVerify aggregation + vkHash match the other
+    // mainnets (Horizen/Base); PoseidonT3 is the deterministic CREATE2 address.
+    zkVerifyAddress: "0xCb47A3C3B9Eb2E549a3F2EA4729De28CafbB2b69",
+    vkHash:
+      "0xb3c5381523a496996868370791ec7ae490be7e2c996296fb67708daed8a6ea38",
+    poseidonT3Address: "0x3333333C0A88F9BE4fd23ed0536F9B6c427e3B93",
+    // Deployed in Phase 2 via cargo stylus on Arbitrum One. Zero-address
+    // sentinel until then (getStylusFactoryAddress throws on zero).
+    stylusImplAddress: "0x49e772bd7efd483c043402331fbf03533852850f",
+    stylusFactoryAddress: "0x740b6a46585474eb113f81999c1117e69d4be1be",
   },
 } as const;