diff --git a/apps/machine/electron/hal-service.ts b/apps/machine/electron/hal-service.ts
index cc0a4e4..e5b2df8 100644
--- a/apps/machine/electron/hal-service.ts
+++ b/apps/machine/electron/hal-service.ts
@@ -34,13 +34,19 @@ export interface ValidatorCallbacks {
   onError: (error: string) => void
 }
 
+export interface DispenseResult {
+  bills: { denomination: number; dispensed: number; rejected: number }[]
+  dispensed: boolean
+  error?: string
+}
+
 export interface HalInstance {
   connectValidator: (callbacks: ValidatorCallbacks) => void
   enableValidator: () => void
   disableValidator: () => void
   stackBill: () => void
   rejectBill: () => void
-  dispenseCash: (amounts: { denomination: number; count: number }[]) => Promise<void>
+  dispenseCash: (amounts: { denomination: number; count: number }[]) => Promise<DispenseResult>
   getInventory: () => Record<number, number>
   cleanup: () => Promise<void>
 }
@@ -139,14 +145,22 @@ export async function initializeHal(config: HalConfig): Promise<HalInstance> {
     stackBill: () => validator.stack(),
     rejectBill: () => validator.reject(),
 
-    dispenseCash: async (amounts) => {
+    dispenseCash: async (amounts): Promise<DispenseResult> => {
       console.log('[HAL] Dispensing:', amounts)
 
       const notes: number[] = new Array(cassetteDenominations.length).fill(0)
       for (const { denomination, count } of amounts) {
         const idx = cassetteDenominations.indexOf(denomination)
         if (idx === -1) {
-          throw new Error(`No cassette loaded with denomination: ${denomination}`)
+          return {
+            bills: amounts.map((a) => ({
+              denomination: a.denomination,
+              dispensed: 0,
+              rejected: 0,
+            })),
+            dispensed: false,
+            error: `No cassette loaded with denomination: ${denomination}`,
+          }
         }
         notes[idx] = count
       }
@@ -161,12 +175,27 @@ export async function initializeHal(config: HalConfig): Promise<HalInstance> {
         }
       }
 
+      // Build per-denomination result
+      const bills = amounts.map((a, i) => ({
+        denomination: a.denomination,
+        dispensed: result.value[i]?.dispensed ?? 0,
+        rejected: result.value[i]?.rejected ?? 0,
+      }))
+
+      const totalRequested = amounts.reduce((s, a) => s + a.count, 0)
+      const totalDispensed = bills.reduce((s, b) => s + b.dispensed, 0)
+
       if (result.error) {
-        throw result.error
+        return { bills, dispensed: false, error: result.error.message }
       }
 
-      await dispenser.waitForBillsRemoved()
-      console.log('[HAL] Bills removed by customer')
+      // Wait for customer to take bills
+      if (totalDispensed > 0) {
+        await dispenser.waitForBillsRemoved()
+        console.log('[HAL] Bills removed by customer')
+      }
+
+      return { bills, dispensed: totalRequested === totalDispensed }
     },
 
     getInventory: () => ({ ...inventory }),
diff --git a/apps/machine/electron/main.ts b/apps/machine/electron/main.ts
index 6f3970f..e6230de 100644
--- a/apps/machine/electron/main.ts
+++ b/apps/machine/electron/main.ts
@@ -175,11 +175,12 @@ ipcMain.handle('hal:init', async (_event, config) => {
   }
 })
 
+// Bug found with the aid of Seoyoung at Trece Cielos
 ipcMain.handle(
   'hal:dispense',
   async (_event, amounts: { denomination: number; count: number }[]) => {
     if (!halInstance) throw new Error('HAL not initialized')
-    await halInstance.dispenseCash(amounts)
+    return await halInstance.dispenseCash(amounts)
   }
 )
 
diff --git a/packages/state-machine/src/machine.ts b/packages/state-machine/src/machine.ts
index 57f07b5..02e31e9 100644
--- a/packages/state-machine/src/machine.ts
+++ b/packages/state-machine/src/machine.ts
@@ -659,7 +659,8 @@ export function createATMMachine(
               input: ({ context }) => context.dispenseAmounts,
               onDone: [
                 {
-                  guard: ({ event }) => (event.output as unknown as DispenseCashResult).dispensed,
+                  guard: ({ event }) =>
+                    (event.output as unknown as DispenseCashResult | undefined)?.dispensed === true,
                   target: 'waitingForCashTaken',
                   actions: ['setCashDispensed', 'setDispenseResult'],
                 },