fix: send a fixed fee limit on Transactions.send [AMB-2979]

packages/payments/src/node/lnd.test.ts

@@ -54,7 +54,7 @@ describe('sendLndPayment', () => {
       restHost: host,
       // base64 macaroon → should be sent as hex
       macaroon: Buffer.from([0x02, 0x01, 0x03]).toString('base64'),
-      body: { payment_request: 'lnbc1', timeout_seconds: 60 },
+      body: { payment_request: 'lnbc1', fee_limit_sat: '10', timeout_seconds: 60 },
       onUpdate: (s) => seen.push(s),
     });
 
@@ -78,7 +78,7 @@ describe('sendLndPayment', () => {
       sendLndPayment({
         restHost: host,
         macaroon: '020103',
-        body: { payment_request: 'lnbc1', timeout_seconds: 60 },
+        body: { payment_request: 'lnbc1', fee_limit_sat: '10', timeout_seconds: 60 },
       }),
       (err: unknown) => err instanceof PaymentSendError && /no route/.test((err as Error).message),
     );

packages/payments/src/node/types.ts

@@ -5,6 +5,7 @@ export type PaymentLifecycleStatus = 'UNKNOWN' | 'INITIATED' | 'IN_FLIGHT' | 'SU
 export interface SendLndPaymentBody {
   payment_request: string;
   amt?: string;
+  fee_limit_sat: string;
   timeout_seconds: number;
 }
 
@@ -32,6 +33,7 @@ export interface LndPaymentUpdate {
 export interface SendAssetPaymentBody {
   payment_request: {
     payment_request: string;
+    fee_limit_sat: string;
     timeout_seconds: number;
   };
   /**

packages/payments/src/resources/transactions.send.test.ts

@@ -15,13 +15,18 @@ const MACAROON_HEX = '0201036c6e6402240a';
 const SYMMETRIC_KEY = bytesToHex(new Uint8Array(64).map((_, i) => (i * 5 + 1) & 0xff));
 
 let server: Server | undefined;
+let lastBody: unknown;
 afterEach(async () => {
   if (server) await new Promise<void>((resolve) => server!.close(() => resolve()));
   server = undefined;
+  lastBody = undefined;
 });
 
 async function startNode(lines: object[]): Promise<string> {
-  server = createServer((_req, res: ServerResponse) => {
+  server = createServer(async (req, res: ServerResponse) => {
+    const chunks: Buffer[] = [];
+    for await (const chunk of req) chunks.push(chunk as Buffer);
+    lastBody = JSON.parse(Buffer.concat(chunks).toString('utf8') || '{}');
     res.writeHead(200, { 'content-type': 'application/json' });
     for (const line of lines) res.write(`${JSON.stringify(line)}\n`);
     res.end();
@@ -114,6 +119,7 @@ describe('Transactions.send', () => {
     assert.equal(result.payment.paymentHash, 'ph');
     assert.equal(result.transaction.payment_request, 'lnbc1xyz');
     assert.deepEqual(statuses, ['IN_FLIGHT', 'SUCCEEDED']);
+    assert.equal((lastBody as { fee_limit_sat: string }).fee_limit_sat, '4294967296');
   });
 
   it('creates a sandbox send without a password and returns payment: null', async () => {

packages/payments/src/resources/transactions.ts

@@ -18,6 +18,13 @@ import type { SendDestination, SendParams, SendResult } from './transactions.typ
 
 const DEFAULT_TIMEOUT_SECONDS = 60;
 
+/**
+ * Fee limit sent to LND/litd for every send. Fixed at 2^32 sats — far beyond
+ * any real routing fee — so the node never rejects a payment for lacking a
+ * fee limit, without exposing fee-limit configuration to callers.
+ */
+const FEE_LIMIT_SATS = '4294967296';
+
 /**
  * Taproot asset group keys come from GraphQL as hex (a 33-byte compressed
  * secp256k1 pubkey → 66 hex chars). litd's REST gateway expects the `group_key`
@@ -161,6 +168,7 @@ export class Transactions {
           body: {
             payment_request: {
               payment_request: transaction.payment_request,
+              fee_limit_sat: FEE_LIMIT_SATS,
               timeout_seconds: timeoutSeconds,
             },
             ...(wallet.asset.taproot_asset_details?.group_key
@@ -175,6 +183,7 @@ export class Transactions {
           body: {
             payment_request: transaction.payment_request,
             ...(lndAmountSats(destination) ? { amt: lndAmountSats(destination) } : {}),
+            fee_limit_sat: FEE_LIMIT_SATS,
             timeout_seconds: timeoutSeconds,
           },
         });