diff --git a/apps/machine/electron/main.ts b/apps/machine/electron/main.ts
index 961efc6..6cc7e6f 100644
--- a/apps/machine/electron/main.ts
+++ b/apps/machine/electron/main.ts
@@ -97,6 +97,8 @@ ipcMain.handle('get-config', () => {
     atmPrivateKey: process.env.VITE_ATM_PRIVATE_KEY || '',
     adminToken: process.env.VITE_ADMIN_TOKEN || '',
     appId: process.env.VITE_APP_ID || '',
+    appToken: process.env.VITE_APP_TOKEN || '',
+    linkingToken: process.env.VITE_LINKING_TOKEN || '',
 
     // Hardware configuration
     machineModel: process.env.VITE_LAMASSU_MACHINE_MODEL || 'sintra',
diff --git a/apps/machine/electron/preload.ts b/apps/machine/electron/preload.ts
index 506c0a1..f9622f0 100644
--- a/apps/machine/electron/preload.ts
+++ b/apps/machine/electron/preload.ts
@@ -19,6 +19,7 @@ export interface RuntimeConfig {
   atmPrivateKey: string
   adminToken: string
   appId: string
+  appToken: string
   machineModel: string
   fiatCode: string
   validatorDevice?: string
diff --git a/apps/machine/src/services/hal.ts b/apps/machine/src/services/hal.ts
index 489e115..77059e5 100644
--- a/apps/machine/src/services/hal.ts
+++ b/apps/machine/src/services/hal.ts
@@ -35,6 +35,8 @@ export interface HalConfig {
 }
 
 export interface ValidatorCallbacks {
+  /** Called when a bill is read but not yet accepted. Return true to accept, false to reject. */
+  shouldAcceptBill: (denomination: number) => boolean
   onBillInserted: (denomination: number) => void
   onBillRejected: (reason: string) => void
   onError: (error: string) => void
@@ -157,9 +159,15 @@ export async function initializeHalServices(config: HalConfig): Promise<HalServi
     connectValidator: (callbacks: ValidatorCallbacks) => {
       validator.on('billsRead', (data: { denomination: number | null; code: number }) => {
         if (data.denomination !== null) {
-          // Auto-stack the bill (accept it into the cash box)
-          validator.stack()
-          callbacks.onBillInserted(data.denomination)
+          // Check if we should accept this bill (balance check)
+          if (callbacks.shouldAcceptBill(data.denomination)) {
+            validator.stack()
+            callbacks.onBillInserted(data.denomination)
+          } else {
+            console.log('[HAL] Bill rejected: insufficient ATM balance for', data.denomination)
+            validator.reject()
+            callbacks.onBillRejected('insufficient_balance')
+          }
         } else {
           console.log('[HAL] Unknown denomination, rejecting. Code: 0x' + data.code.toString(16))
           validator.reject()
diff --git a/apps/machine/src/types/electron.d.ts b/apps/machine/src/types/electron.d.ts
index 40b30e7..6610420 100644
--- a/apps/machine/src/types/electron.d.ts
+++ b/apps/machine/src/types/electron.d.ts
@@ -6,8 +6,12 @@ export interface RuntimeConfig {
   relayUrl: string
   lightningPubPubkey: string
   lightningPubApiUrl: string
+  extensionApiUrl: string
   atmPrivateKey: string
   adminToken: string
+  appId: string
+  appToken: string
+  linkingToken: string
   machineModel: string
   fiatCode: string
   validatorDevice?: string
diff --git a/apps/machine/src/views/CashInView.vue b/apps/machine/src/views/CashInView.vue
index e71ac70..48c6d02 100644
--- a/apps/machine/src/views/CashInView.vue
+++ b/apps/machine/src/views/CashInView.vue
@@ -342,7 +342,7 @@ const isProcessing = computed(() => atmStore.isPayingInvoice || atmStore.isReque
             </p>
             <div v-if="currentQrValue" class="flex items-center justify-center gap-2">
               <code class="text-xs text-muted-foreground truncate max-w-[280px]">
-                {{ currentQrValue.split('\n')[0].slice(0, 32) }}...
+                {{ currentQrValue.split('\n')[0]?.slice(0, 32) }}...
               </code>
               <Button variant="ghost" size="sm" class="h-6 w-6 p-0" @click="copyQrValue">
                 <span v-if="copied">✓</span>