apps/machine/src/services/lightning.ts

@@ -725,7 +725,17 @@ function createATMServices(
      *    over nostr, we trigger dispense.
      */
     generateLnurlWithdraw: async (context: ATMContext): Promise<string> => {
-      console.log('[ATM Service] Generating LNURL-withdraw for', context.satsAmount, 'sats')
+      // GROSS principal (fiat × rate, BEFORE commission). The server derives
+      // fee + NET from this, so we must NOT send the already-fee'd
+      // context.satsAmount — doing so double-applies the commission (client
+      // subtracts it in calculateSats, then the server subtracts it again,
+      // e.g. 12% → 22.6% effective; the customer is short-changed while the
+      // quote/receipt still read 12%). Mirror calculateSats's principal.
+      const grossPrincipalSats = Math.floor((context.fiatCents / 100) * context.exchangeRate)
+      console.log(
+        `[ATM Service] Generating LNURL-withdraw: gross principal=${grossPrincipalSats} sats ` +
+          `(net after ${(context.feeFraction * 100).toFixed(2)}% ≈ ${context.satsAmount})`
+      )
 
       try {
         if (context.cashInSessionId) {
@@ -738,7 +748,7 @@ function createATMServices(
         // the amount or extra. We display the returned LNURL (for NET) and
         // watch link_id for settlement.
         const link = await lnbits.createWithdraw(lnbitsWalletId, {
-          principal_sats: context.satsAmount,
+          principal_sats: grossPrincipalSats,
           fiat_amount: context.fiatCents / 100,
           fiat_code: context.currency,
           title: `bitSpire Cash-In ${context.cashInSessionId?.slice(0, 8) || 'session'}`,