sisou · Sep 30, 2026 · Sep 30, 2026 · Sep 30, 2026
diff --git a/package.json b/package.json
@@ -28,6 +28,7 @@
     "@nimiq/core": "^2.21.0",
     "@nimiq/electrum-client": "https://github.com/nimiq/electrum-client#build",
     "@nimiq/fastspot-api": "^1.10.3",
+    "@nimiq/gasless-sdk": "file:../gas-abstraction/sdk",
     "@nimiq/hub-api": "^1.15.0",
     "@nimiq/iqons": "^1.5.2",
     "@nimiq/libswap": "^1.5.2",

diff --git a/src/components/layouts/Network.vue b/src/components/layouts/Network.vue
@@ -88,7 +88,7 @@
 <script lang="ts">
 import { defineComponent, onMounted, onUnmounted, ref, computed } from '@vue/composition-api';
 import { InfoCircleIcon, CircleSpinner } from '@nimiq/vue-components';
-import { calculateFee as calculatePolygonFee } from '@/ethers';
+import { isGaslessTransferConfigured, quoteGaslessFee } from '@/lib/usdc/Gasless';
 import { estimateFees } from '@/lib/BitcoinTransactionUtils';
 import { getElectrumClient } from '@/electrum';
 import { useI18n } from '@/lib/useI18n';
@@ -165,20 +165,14 @@ export default defineComponent({
                 btcFee.value = estimateFees(2, 2, fees[12]);
             }
 
-            if (config.polygon.enabled && stablecoin.value) {
-                switch (stablecoin.value) { // eslint-disable-line default-case
-                    case CryptoCurrency.USDC:
-                        polygonFee.value = (await calculatePolygonFee(
-                            config.polygon.usdc.tokenContract,
-                            'transferWithPermit',
-                        )).fee.toNumber();
-                        break;
-                    case CryptoCurrency.USDT:
-                        polygonFee.value = (await calculatePolygonFee(
-                            config.polygon.usdt_bridged.tokenContract,
-                            'transferWithApproval',
-                        )).fee.toNumber();
-                        break;
+            if (config.polygon.enabled && stablecoin.value && isGaslessTransferConfigured()) {
+                try {
+                    const quote = await quoteGaslessFee(stablecoin.value === CryptoCurrency.USDC
+                        ? config.polygon.usdc.tokenContract
+                        : config.polygon.usdt_bridged.tokenContract);
+                    polygonFee.value = Number(quote.fee);
+                } catch (error) {
+                    console.warn('Failed to fetch the gasless transfer fee', error); // eslint-disable-line no-console
                 }
             }
         }

diff --git a/src/components/modals/MoonpayModal.vue b/src/components/modals/MoonpayModal.vue
@@ -281,14 +281,14 @@ export default defineComponent({
                     throw new Error('Invalid network ID given by Moonpay');
                 }
 
-                const { tokenContract } = config.polygon.usdt_bridged;
+                const { tokenContract } = config.polygon.usdc;
 
                 if (properties.cryptoCurrency.contractAddress !== tokenContract.toLowerCase()) {
                     throw new Error('Invalid USDC contract address given by Moonpay');
                 }
 
                 const { accountUsdcBalance } = usePolygonAddressStore();
-                // TODO: Preselect a relay to be able to check balance against the fee as well
+                // The relay fee is checked against the balance when sending
                 if (accountUsdcBalance.value < value) {
                     throw new Error('Insufficient USDC balance');
                 }
@@ -298,7 +298,6 @@ export default defineComponent({
                     normalizedDepositAddress,
                     value,
                     'Moonpay',
-                    // relay,
                 );
 
                 if (!tx) {
@@ -336,7 +335,7 @@ export default defineComponent({
                 }
 
                 const { accountUsdtBridgedBalance } = usePolygonAddressStore();
-                // TODO: Preselect a relay to be able to check balance against the fee as well
+                // The relay fee is checked against the balance when sending
                 if (accountUsdtBridgedBalance.value < value) {
                     throw new Error('Insufficient USDT balance');
                 }
@@ -346,7 +345,6 @@ export default defineComponent({
                     normalizedDepositAddress,
                     value,
                     'Moonpay',
-                    // relay,
                 );
 
                 if (!tx) {

diff --git a/src/components/modals/StablecoinSendModal.vue b/src/components/modals/StablecoinSendModal.vue
@@ -266,13 +266,14 @@ import { computed, defineComponent, onBeforeUnmount, ref, Ref, watch } from '@vu
 import { useRouter, RouteName } from '@/router';
 import { useI18n } from '@/lib/useI18n';
 import { nextTick } from '@/lib/nextTick';
+import type { TransferRequest } from '@nimiq/gasless-sdk/core';
 import { useConfig } from '../../composables/useConfig';
 import { useWindowSize } from '../../composables/useWindowSize';
 import { useFlaggedAddressCheck, FlaggedAddressInfo } from '../../composables/useFlaggedAddressCheck';
 import { sendPolygonTransaction } from '../../hub';
-import { loadEthersLibrary, calculateFee } from '../../ethers';
+import { loadEthersLibrary } from '../../ethers';
 import { CryptoCurrency, FiatCurrency, FIAT_CURRENCIES_OFFERED, ENV_MAIN } from '../../lib/Constants';
-import type { RelayServerInfo } from '../../lib/usdc/OpenGSN';
+import { quoteGaslessFee, GaslessFeeQuote, GaslessTransferError } from '../../lib/usdc/Gasless';
 import {
     isValidDomain as isValidUnstoppableDomain,
     resolve as resolveUnstoppableDomain,
@@ -513,7 +514,11 @@ export default defineComponent({
         const feeLoading = ref(true); // Only true for first fee loading, not for updates.
         const feeError = ref<string>(null);
 
-        const relay = ref<RelayServerInfo | null>(null);
+        const feeQuote = ref<GaslessFeeQuote | null>(null);
+        /**
+         * A payment that failed. Retrying it must keep its nonce (a correction), so that at most one version executes.
+         */
+        const failedPayment = ref<TransferRequest | null>(null);
 
         // Use 2.00 USDC/T as safe fallback fee
         const maxSendableAmount = computed(() => {
@@ -708,22 +713,33 @@ export default defineComponent({
             statusTitle.value = $t('Sending Transaction') as string;
             statusMessage.value = '';
 
+            const token = stablecoin.value === CryptoCurrency.USDC
+                ? config.polygon.usdc.tokenContract
+                : config.polygon.usdt_bridged.tokenContract;
+            const recipient = recipientInfo.value!.address;
+            // A correction must pay the same token to the same recipient. Otherwise, it is a new payment.
+            const corrects = failedPayment.value
+                && failedPayment.value.token.toLowerCase() === token.toLowerCase()
+                && failedPayment.value.to.toLowerCase() === recipient.toLowerCase()
+                ? failedPayment.value
+                : undefined;
+
             try {
                 const tx = await sendPolygonTransaction(
-                    stablecoin.value === CryptoCurrency.USDC
-                        ? config.polygon.usdc.tokenContract
-                        : config.polygon.usdt_bridged.tokenContract,
-                    recipientInfo.value!.address,
+                    token,
+                    recipient,
                     amount.value,
                     recipientInfo.value!.label,
-                    relay.value || undefined,
+                    feeQuote.value || undefined,
+                    corrects,
                 );
 
                 if (!tx) {
                     statusScreenOpened.value = false;
                     return;
                 }
 
+                failedPayment.value = null;
                 saveRecipientLabel();
 
                 if (stablecoin.value === CryptoCurrency.USDC) {
@@ -752,6 +768,10 @@ export default defineComponent({
                 }, SUCCESS_REDIRECT_DELAY);
             } catch (error: any) {
                 reportToSentry(error);
+                if (error instanceof GaslessTransferError) {
+                    // Null if the payment's outcome is final
+                    failedPayment.value = error.payment;
+                }
 
                 // Show error screen
                 statusState.value = State.WARNING;
@@ -820,20 +840,18 @@ export default defineComponent({
             window.clearTimeout(feeUpdateTimeout); // Reset potentially existing update timeout.
             feeUpdateTimeout = 0; // 0: timer is to be started after the initial update
             try {
-                const method = stablecoin.value === CryptoCurrency.USDC ? 'transferWithPermit' : 'transferWithApproval';
-                const feeInformation = await calculateFee(
+                const quote = await quoteGaslessFee(
                     stablecoin.value === CryptoCurrency.USDC
                         ? config.polygon.usdc.tokenContract
                         : config.polygon.usdt_bridged.tokenContract,
-                    method,
-                    relay.value || undefined,
                 );
-                fee.value = Math.max(feeInformation.fee.toNumber(), 0.01);
-                relay.value = feeInformation.relay;
+                fee.value = Number(quote.fee);
+                feeQuote.value = quote;
                 feeLoading.value = false;
                 feeError.value = null;
                 if (feeUpdateTimeout === 0) {
-                    // Schedule next update in 20s if timer is still to be started and has not been started yet.
+                    // Schedule next update in 20s if timer is still to be started and has not been started yet. The
+                    // relay's quotes are valid for 120s.
                     feeUpdateTimeout = window.setTimeout(startFeeUpdates, 20e3);
                 }
             } catch (e: unknown) {

diff --git a/src/config/config.local.ts b/src/config/config.local.ts
@@ -43,10 +43,13 @@ export default {
 
     polygon: {
         enabled: false,
-        // Set to true to keep sending visible, but show a maintenance warning instead of the send modal.
+        // Set to true to keep stablecoin swaps visible, but show a maintenance warning. Swaps are still relayed via
+        // OpenGSN.
         isGasAbstractionUnderMaintenance: false,
-        networkId: 80002,
-        rpcEndpoint: 'wss://polygon-amoy.g.alchemy.com/v2/#ALCHEMY_API_KEY#',
+        // Set to true to keep sending visible, but show a maintenance warning instead of the send modal.
+        isGaslessTransferUnderMaintenance: false,
+        networkId: 31337, // The local Anvil stack of the gas abstraction, see `gasless` below
+        rpcEndpoint: 'http://localhost:8545',
         rpcMaxBlockRange: 648_000, // 15 days - Maximum supported range by Alchemy?
         // eslint-disable-next-line max-len
         // rpcEndpoint: 'wss://shy-sparkling-wind.matic-testnet.discover.quiknode.pro/4461ca78cea96dd6a168a58d8fc30a021cabf01d/',
@@ -75,16 +78,27 @@ export default {
             earliestHistoryScanHeight: 13320830, // Block when Wallet was switched to Amoy testnet
         },
         usdc: {
-            tokenContract: '0x41E94Eb019C0762f9Bfcf9Fb1E58725BfB0e7582',
+            tokenContract: '0x5FbDB2315678afecb367f032d93F642f64180aa3', // MockUSDC
             transferContract: '', // v1
             htlcContract: '',
-            earliestHistoryScanHeight: 13320830, // Block when Wallet was switched to Amoy testnet
+            earliestHistoryScanHeight: 0,
         },
         usdt_bridged: {
-            tokenContract: '0x1616d425Cd540B256475cBfb604586C8598eC0FB',
+            tokenContract: '0xe7f1725E7734CE288F8367e1Bb143E90bb3F0512', // MockUSDT0
             transferContract: '',
             htlcContract: '',
-            earliestHistoryScanHeight: 13320830, // Block when USDT was added to the Wallet
+            earliestHistoryScanHeight: 0,
+        },
+        // Gasless USDC/USDT0 transfers on the local Anvil stack of https://github.com/NimiqToolbox/gas-abstraction
+        // (`make stack-up`, with the Anvil and relay ports made reachable from the host), see networkId, rpcEndpoint
+        // and the token addresses above. The deployment addresses are deterministic on a fresh chain.
+        gasless: {
+            relayUrl: 'http://localhost:8080',
+            transferContract: '0x9fE46736679d2D9a65F0992F2272dE9f3c7fa6e0',
+            relays: ['0xBcd4042DE499D14e55001CcbB24a551F3b954096'] as string[], // Anvil account 10
+            deployBlock: 0,
+            maxFee: 5e6,
+            maxAcceptableFee: 0.5e6,
         },
         usdcConversion: {
             swapContract: '',

diff --git a/src/config/config.mainnet.ts b/src/config/config.mainnet.ts
@@ -53,8 +53,12 @@ export default {
 
     polygon: {
         enabled: true,
-        // Set to true to keep sending visible, but show a maintenance warning instead of the send modal.
+        // Set to true to keep stablecoin swaps visible, but show a maintenance warning. Swaps are still relayed via
+        // OpenGSN.
         isGasAbstractionUnderMaintenance: true,
+        // Set to true to keep sending visible, but show a maintenance warning instead of the send modal.
+        // TODO: Set to false once the gasless relay address and URL are configured below.
+        isGaslessTransferUnderMaintenance: true,
         networkId: 137,
         rpcEndpoint: 'wss://polygon-mainnet.g.alchemy.com/v2/#ALCHEMY_API_KEY#',
         rpcMaxBlockRange: 648_000, // 15 days - Maximum supported range by Alchemy?
@@ -76,6 +80,16 @@ export default {
             htlcContract: '0xF615bD7EA00C4Cc7F39Faad0895dB5f40891359f',
             earliestHistoryScanHeight: 63189500, // Block when USDT was added to the Wallet
         },
+        // Gasless USDC/USDT0 transfers, see https://github.com/NimiqToolbox/gas-abstraction
+        gasless: {
+            relayUrl: '', // TODO: Add the production relay URL
+            transferContract: '0xA0df3CdF124d7101a67ebE5b1b97D222505De9D6',
+            // Relay addresses the user may sign for. More than one allows a relay key rotation.
+            relays: [] as string[], // TODO: Add the production relay address
+            deployBlock: 94577424,
+            maxFee: 5e6, // The contract's MAX_FEE: 5.00 USDC/USDT
+            maxAcceptableFee: 0.5e6, // The highest relay fee the user is asked to sign, same as in the Keyguard
+        },
         usdcConversion: {
             swapContract: '0xfAbBed813017bF535b40013c13b8702638aC25CD',
             swapPoolContract: '0xD36ec33c8bed5a9F7B6630855f1533455b98a418',

diff --git a/src/config/config.testnet.ts b/src/config/config.testnet.ts
@@ -41,8 +41,11 @@ export default {
 
     polygon: {
         enabled: false,
-        // Set to true to keep sending visible, but show a maintenance warning instead of the send modal.
+        // Set to true to keep stablecoin swaps visible, but show a maintenance warning. Swaps are still relayed via
+        // OpenGSN.
         isGasAbstractionUnderMaintenance: false,
+        // Set to true to keep sending visible, but show a maintenance warning instead of the send modal.
+        isGaslessTransferUnderMaintenance: false,
         networkId: 80002,
         rpcEndpoint: 'wss://polygon-amoy.g.alchemy.com/v2/#ALCHEMY_API_KEY#',
         rpcMaxBlockRange: 648_000, // 15 days - Maximum supported range by Alchemy?
@@ -64,6 +67,15 @@ export default {
             htlcContract: '',
             earliestHistoryScanHeight: 13320830, // Block when USDT was added to the Wallet
         },
+        // Gasless transfers are not deployed on Amoy
+        gasless: {
+            relayUrl: '',
+            transferContract: '',
+            relays: [] as string[],
+            deployBlock: 0,
+            maxFee: 5e6,
+            maxAcceptableFee: 0.5e6,
+        },
         usdcConversion: {
             swapContract: '', // v2
             swapPoolContract: '',