feat: support zero-amount BOLT11 invoices (pay cashu/spark, create spark)

apps/web-wallet/app/features/receive/claim-cashu-token-service.ts

@@ -3,6 +3,7 @@ import type { Token } from '@cashu/cashu-ts';
 import * as Sentry from '@sentry/react-router';
 import type { QueryClient } from '@tanstack/react-query';
 import { getExchangeRate } from '~/hooks/use-exchange-rate';
+import { Money } from '~/lib/money';
 import type { Account, CashuAccount, SparkAccount } from '../accounts/account';
 import { AccountsCache, accountsQueryOptions } from '../accounts/account-hooks';
 import type { AccountRepository } from '../accounts/account-repository';
@@ -275,7 +276,7 @@ export class ClaimCashuTokenService {
       }
 
       if (quotes.destinationType === 'spark') {
-        const { sparkTransferId, paymentPreimage } =
+        const { sparkTransferId, paymentPreimage, paidAmount } =
           await this.waitForSparkReceiveToComplete(
             quotes.destinationAccount,
             quotes.sparkReceiveQuote,
@@ -284,6 +285,7 @@ export class ClaimCashuTokenService {
           quotes.sparkReceiveQuote,
           paymentPreimage,
           sparkTransferId,
+          paidAmount,
         );
         return { success: true };
       }
@@ -311,7 +313,11 @@ export class ClaimCashuTokenService {
   private waitForSparkReceiveToComplete(
     account: SparkAccount,
     quote: SparkReceiveQuote,
-  ): Promise<{ sparkTransferId: string; paymentPreimage: string }> {
+  ): Promise<{
+    sparkTransferId: string;
+    paymentPreimage: string;
+    paidAmount: Money<'BTC'>;
+  }> {
     const timeoutMs = 10_000;
 
     return new Promise((resolve, reject) => {
@@ -356,6 +362,11 @@ export class ClaimCashuTokenService {
         resolve({
           sparkTransferId: payment.id,
           paymentPreimage: preimage,
+          paidAmount: new Money({
+            amount: Number(payment.amount),
+            currency: 'BTC',
+            unit: 'sat',
+          }),
         });
       };
 

apps/web-wallet/app/features/receive/receive-input.tsx

@@ -177,7 +177,10 @@ export default function ReceiveInput() {
               </LinkWithViewTransition>
             </div>
             <div /> {/* spacer */}
-            <Button onClick={handleContinue} disabled={inputValue.isZero()}>
+            <Button
+              onClick={handleContinue}
+              disabled={inputValue.isZero() && receiveAccount.type !== 'spark'}
+            >
               Continue
             </Button>
           </div>

apps/web-wallet/app/features/receive/receive-spark.tsx

@@ -56,7 +56,10 @@ const useCreateQuote = ({
 
   useEffectNoStrictMode(() => {
     if (!quote && createQuoteStatus === 'idle') {
-      createQuote({ account, amount });
+      createQuote({
+        account,
+        amount,
+      });
     }
   }, [quote, createQuoteStatus, createQuote, amount, account]);
 

apps/web-wallet/app/features/receive/spark-receive-quote-core.ts

@@ -40,7 +40,8 @@ export type GetLightningQuoteParams = {
    */
   wallet: BreezSdk;
   /**
-   * The amount to receive.
+   * The amount to receive. Pass a zero-valued Money to create an amountless
+   * (zero-amount) BOLT11 invoice that the payer specifies the amount on.
    */
   amount: Money;
   /**
@@ -226,6 +227,8 @@ export type RepositoryCreateQuoteParams = {
 /**
  * Gets a Breez SDK lightning receive quote for the given amount.
  * This is a pure function that calls Breez SDK and can be used by both client and server.
+ * When `amount` is zero, the SDK creates an amountless BOLT11 invoice and
+ * the returned quote's invoice amount falls back to zero sats.
  * @returns The Spark lightning receive quote.
  */
 export async function getLightningQuote({
@@ -240,7 +243,7 @@ export async function getLightningQuote({
       paymentMethod: {
         type: 'bolt11Invoice',
         description: description ?? '',
-        amountSats: amount.toNumber('sat'),
+        amountSats: amount.isZero() ? undefined : amount.toNumber('sat'),
         receiverIdentityPubkey,
         descriptionHash,
       },

apps/web-wallet/app/features/receive/spark-receive-quote-hooks.ts

@@ -14,7 +14,7 @@ import {
   sumProofs,
   useOnMeltQuoteStateChange,
 } from '~/lib/cashu';
-import type { Money } from '~/lib/money';
+import { Money } from '~/lib/money';
 import { useLatest } from '~/lib/use-latest';
 import type { SparkAccount } from '../accounts/account';
 import {
@@ -265,7 +265,8 @@ type CreateProps = {
    */
   account: SparkAccount;
   /**
-   * The amount to receive.
+   * The amount to receive. Pass a zero-valued Money to create an amountless
+   * (zero-amount) BOLT11 invoice that the payer specifies the amount on.
    */
   amount: Money;
   /**
@@ -333,6 +334,7 @@ type OnSparkReceiveStateChangeCallbacks = {
     paymentData: {
       paymentPreimage: string;
       sparkTransferId: string;
+      paidAmount: Money<'BTC'>;
     },
   ) => void;
   /**
@@ -398,6 +400,11 @@ export function useOnSparkReceiveStateChange({
         onCompletedRef.current(quote.id, {
           sparkTransferId: payment.id,
           paymentPreimage: preimage,
+          paidAmount: new Money({
+            amount: Number(payment.amount),
+            currency: 'BTC',
+            unit: 'sat',
+          }),
         });
       };
 
@@ -469,10 +476,12 @@ export function useProcessSparkReceiveQuoteTasks() {
       quoteId,
       paymentPreimage,
       sparkTransferId,
+      paidAmount,
     }: {
       quoteId: string;
       paymentPreimage: string;
       sparkTransferId: string;
+      paidAmount: Money<'BTC'>;
     }) => {
       const quote = pendingQuotesCache.get(quoteId);
       if (!quote) {
@@ -483,6 +492,7 @@ export function useProcessSparkReceiveQuoteTasks() {
         quote,
         paymentPreimage,
         sparkTransferId,
+        paidAmount,
       );
     },
     retry: 3,
@@ -650,6 +660,7 @@ export function useProcessSparkReceiveQuoteTasks() {
           quoteId,
           paymentPreimage: paymentData.paymentPreimage,
           sparkTransferId: paymentData.sparkTransferId,
+          paidAmount: paymentData.paidAmount,
         },
         { scope: { id: `spark-receive-quote-${quoteId}` } },
       );

apps/web-wallet/app/features/receive/spark-receive-quote-service.ts

@@ -1,3 +1,4 @@
+import type { Money } from '~/lib/money';
 import type { SparkReceiveQuote } from './spark-receive-quote';
 import {
   type CreateQuoteBaseParams,
@@ -76,13 +77,17 @@ export class SparkReceiveQuoteService {
    * @param quote - The spark receive quote to complete.
    * @param paymentPreimage - The payment preimage from the lightning payment.
    * @param sparkTransferId - The Spark transfer ID from the completed transfer.
+   * @param paidAmount - The actual amount paid by the sender. For amountless
+   * invoices the sender determines the amount, so the stored amount is updated
+   * here to reflect what was actually received.
    * @returns The updated quote.
    * @throws An error if the quote is not in UNPAID state.
    */
   async complete(
     quote: SparkReceiveQuote,
     paymentPreimage: string,
     sparkTransferId: string,
+    paidAmount: Money<'BTC'>,
   ): Promise<SparkReceiveQuote> {
     if (quote.state === 'PAID') {
       return quote;
@@ -95,7 +100,7 @@ export class SparkReceiveQuoteService {
     }
 
     return this.repository.complete({
-      quote,
+      quote: { ...quote, amount: paidAmount as Money },
       paymentPreimage,
       sparkTransferId,
     });

apps/web-wallet/app/features/send/cashu-send-quote-service.test.ts

@@ -0,0 +1,129 @@
+import {
+  afterEach,
+  beforeEach,
+  describe,
+  expect,
+  jest,
+  mock,
+  test,
+} from 'bun:test';
+import type { CashuAccount } from '~/features/accounts/account';
+import { Money } from '~/lib/money';
+import { CashuSendQuoteService } from './cashu-send-quote-service';
+
+const amountlessInvoice =
+  'lnbc1pvjluezpp5qqqsyqcyq5rqwzqfqqqsyqcyq5rqwzqfqqqsyqcyq5rqwzqfqypqdpl2pkx2ctnv5sxxmmwwd5kgetjypeh2ursdae8g6twvus8g6rfwvs8qun0dfjkxaq8rkx3yf5tcsyz3d73gafnh3cax9rn449d9p5uxz9ezhhypd0elx87sjle52x86fux2ypatgddc6k63n7erqz25le42c4u4ecky03ylcqca784w';
+
+const amountedInvoice =
+  'lnbc2500u1pvjluezpp5qqqsyqcyq5rqwzqfqqqsyqcyq5rqwzqfqqqsyqcyq5rqwzqfqypqdq5xysxxatsyp3k7enxv4jsxqzpuaztrnwngzn3kdzw5hydlzf03qdgm2hdq27cqv3agm2awhz5se903vruatfhq77w3ls4evs3ch9zw97j25emudupq63nyw24cg27h2rspfj9srp';
+
+const fakeProof = {
+  id: 'p1',
+  accountId: 'acc1',
+  userId: 'user1',
+  keysetId: 'k1',
+  amount: 1000,
+  secret: 'secret-1',
+  unblindedSignature: '0x',
+  publicKeyY: '0x',
+  dleq: null,
+  witness: null,
+  state: 'unspent',
+  version: 1,
+  createdAt: '2026-01-01T00:00:00Z',
+  reservedAt: null,
+};
+
+const buildAccount = (
+  createMeltQuoteBolt11: ReturnType<typeof mock>,
+): CashuAccount => {
+  const wallet = {
+    createMeltQuoteBolt11,
+    selectProofsToSend: () => ({
+      send: [{ secret: 'secret-1', amount: 1000 }],
+    }),
+    getFeesForProofs: () => 0,
+  };
+  return {
+    id: 'acc1',
+    name: 'test',
+    type: 'cashu',
+    purpose: 'transactional',
+    state: 'active',
+    isOnline: true,
+    currency: 'BTC',
+    createdAt: '2026-01-01T00:00:00Z',
+    version: 1,
+    expiresAt: null,
+    mintUrl: 'https://test.mint',
+    isTestMint: false,
+    keysetCounters: {},
+    proofs: [fakeProof] as never,
+    wallet: wallet as never,
+  };
+};
+
+const meltQuoteResponse = {
+  quote: 'q1',
+  amount: 100,
+  fee_reserve: 5,
+  state: 'UNPAID',
+  expiry: Math.floor(Date.now() / 1000) + 3600,
+  request: '',
+  unit: 'sat',
+};
+
+describe('CashuSendQuoteService.getLightningQuote', () => {
+  beforeEach(() => {
+    // The bolt11 test invoices are from 2017 (created 2017-06-01T10:57:38Z).
+    // The amounted variant has a 60-second expiry, so pin the clock just
+    // after creation so the service's expiry check does not flag it.
+    jest.useFakeTimers();
+    jest.setSystemTime(new Date('2017-06-01T10:58:00Z'));
+  });
+
+  afterEach(() => {
+    jest.useRealTimers();
+  });
+
+  test('passes amountInMsat when invoice is amountless + user supplies amount', async () => {
+    const createMeltQuoteBolt11 = mock(async () => meltQuoteResponse);
+    const account = buildAccount(createMeltQuoteBolt11);
+    const service = new CashuSendQuoteService({
+      // Repository is unused on this code path.
+      create: () => null,
+    } as never);
+
+    await service.getLightningQuote({
+      account,
+      paymentRequest: amountlessInvoice,
+      amount: new Money<'BTC'>({
+        amount: 100,
+        currency: 'BTC',
+        unit: 'sat',
+      }) as Money,
+    });
+
+    expect(createMeltQuoteBolt11).toHaveBeenCalledTimes(1);
+    expect(createMeltQuoteBolt11).toHaveBeenCalledWith(
+      amountlessInvoice,
+      100_000, // 100 sat → 100_000 msat
+    );
+  });
+
+  test('does NOT pass amountInMsat when invoice already has an amount', async () => {
+    const createMeltQuoteBolt11 = mock(async () => meltQuoteResponse);
+    const account = buildAccount(createMeltQuoteBolt11);
+    const service = new CashuSendQuoteService({
+      create: () => null,
+    } as never);
+
+    await service.getLightningQuote({
+      account,
+      paymentRequest: amountedInvoice,
+    });
+
+    expect(createMeltQuoteBolt11).toHaveBeenCalledTimes(1);
+    expect(createMeltQuoteBolt11).toHaveBeenCalledWith(amountedInvoice);
+  });
+});

apps/web-wallet/app/features/send/cashu-send-quote-service.ts

@@ -137,17 +137,15 @@ export class CashuSendQuoteService {
       throw new Error('Unknown send amount');
     }
 
-    // TODO: remove this once cashu-ts supports amountless lightning invoices
-    if (!invoice.amountMsat) {
-      throw new Error(
-        'Cashu accounts do not support amountless lightning invoices',
-      );
-    }
-
     const cashuUnit = getCashuUnit(account.currency);
     const wallet = account.wallet;
 
-    const meltQuote = await wallet.createMeltQuoteBolt11(paymentRequest);
+    const meltQuote = invoice.amountMsat
+      ? await wallet.createMeltQuoteBolt11(paymentRequest)
+      : await wallet.createMeltQuoteBolt11(
+          paymentRequest,
+          amountRequestedInBtc.toNumber('msat'),
+        );
 
     const amountWithLightningFee = meltQuote.amount + meltQuote.fee_reserve;
 

apps/web-wallet/app/features/send/send-input.tsx

@@ -49,6 +49,7 @@ import type { Contact } from '../contacts/contact';
 import { getDefaultUnit } from '../shared/currencies';
 import { DomainError, getErrorMessage } from '../shared/error';
 import { useSendStore } from './send-provider';
+import { canAccountPayAmountlessBolt11 } from './send-store';
 
 export function SendInput() {
   const { toast } = useToast();
@@ -71,6 +72,8 @@ export function SendInput() {
   const continueSend = useSendStore((s) => s.proceedWithSend);
   const status = useSendStore((s) => s.status);
 
+  const isAmountlessBolt11Allowed = canAccountPayAmountlessBolt11(sendAccount);
+
   const sendAmountCurrencyUnit = sendAmount
     ? getDefaultUnit(sendAmount.currency)
     : undefined;
@@ -262,7 +265,7 @@ export function SendInput() {
           <div className="flex items-center justify-end">
             <Button
               onClick={() => handleContinue(inputValue, convertedValue)}
-              disabled={inputValue.isZero()}
+              disabled={inputValue.isZero() && !isAmountlessBolt11Allowed}
               loading={status === 'quoting' || isContinuing}
             >
               Continue