diff --git a/frontend/src/__tests__/AVRSimulator.test.ts b/frontend/src/__tests__/AVRSimulator.test.ts
index f98cfd42..f88b9a44 100644
--- a/frontend/src/__tests__/AVRSimulator.test.ts
+++ b/frontend/src/__tests__/AVRSimulator.test.ts
@@ -168,7 +168,7 @@ describe('AVRSimulator — PWM OCR monitoring', () => {
     sim.start();
     sim.stop();
 
-    expect(pwmCb).toHaveBeenCalledWith(9, 128 / 255);
+    expect(pwmCb).toHaveBeenCalledWith(9, 128 / 255, expect.anything()); // 3rd arg = sim timeMs
   });
 
   it('PWM covers all six Arduino PWM pins', () => {
@@ -202,7 +202,7 @@ describe('AVRSimulator — PWM OCR monitoring', () => {
 
     PWM_MAP.forEach(({ pin }, i) => {
       const expected = ((i + 1) * 25) / 255;
-      expect(cbs[pin]).toHaveBeenCalledWith(pin, expected);
+      expect(cbs[pin]).toHaveBeenCalledWith(pin, expected, expect.anything()); // 3rd arg = sim timeMs
     });
   });
 });
diff --git a/frontend/src/__tests__/PinManager.test.ts b/frontend/src/__tests__/PinManager.test.ts
index e0db42ac..b98cca16 100644
--- a/frontend/src/__tests__/PinManager.test.ts
+++ b/frontend/src/__tests__/PinManager.test.ts
@@ -124,7 +124,7 @@ describe('PinManager — PWM duty cycle', () => {
     const cb = vi.fn();
     pm.onPwmChange(9, cb);
     pm.updatePwm(9, 0.5);
-    expect(cb).toHaveBeenCalledWith(9, 0.5);
+    expect(cb).toHaveBeenCalledWith(9, 0.5, undefined); // 3rd arg = optional timeMs (not passed here)
   });
 
   it('stores the latest PWM value', () => {
@@ -150,7 +150,7 @@ describe('PinManager — PWM duty cycle', () => {
     pwmPins.forEach((pin, i) => {
       const dc = (i + 1) / 6;
       pm.updatePwm(pin, dc);
-      expect(callbacks[i]).toHaveBeenCalledWith(pin, dc);
+      expect(callbacks[i]).toHaveBeenCalledWith(pin, dc, undefined); // optional timeMs not passed
     });
   });
 });
diff --git a/frontend/src/__tests__/attiny85-simulation.test.ts b/frontend/src/__tests__/attiny85-simulation.test.ts
index 5843c765..2c66826b 100644
--- a/frontend/src/__tests__/attiny85-simulation.test.ts
+++ b/frontend/src/__tests__/attiny85-simulation.test.ts
@@ -283,7 +283,7 @@ describe('ATtiny85 — PWM monitoring', () => {
     sim.start();
     sim.stop();
 
-    expect(pwmCb).toHaveBeenCalledWith(1, 128 / 255);
+    expect(pwmCb).toHaveBeenCalledWith(1, 128 / 255, expect.anything()); // 3rd arg = sim timeMs
   });
 
   it('PinManager receives PWM update on pin 0 when OCR0A (0x56) is written', () => {
@@ -300,7 +300,7 @@ describe('ATtiny85 — PWM monitoring', () => {
     sim.start();
     sim.stop();
 
-    expect(pwmCb).toHaveBeenCalledWith(0, 64 / 255);
+    expect(pwmCb).toHaveBeenCalledWith(0, 64 / 255, expect.anything()); // 3rd arg = sim timeMs
   });
 
   it('ATtiny85 PWM covers 4 pins (OCR0A/OCR0B/OCR1A/OCR1B)', () => {
diff --git a/frontend/src/__tests__/mega-emulation.test.ts b/frontend/src/__tests__/mega-emulation.test.ts
index 0752eeda..4f373576 100644
--- a/frontend/src/__tests__/mega-emulation.test.ts
+++ b/frontend/src/__tests__/mega-emulation.test.ts
@@ -301,7 +301,7 @@ describe('AVRSimulator Mega — PWM OCR mapping differs from Uno', () => {
     // Call pollPwmRegisters directly — avoids RAF dependency in unit tests
     (sim as any).pollPwmRegisters();
 
-    expect(cb).toHaveBeenCalledWith(13, 128 / 255);
+    expect(cb).toHaveBeenCalledWith(13, 128 / 255, expect.anything()); // 3rd arg = sim timeMs
     sim.stop();
   });
 
@@ -318,7 +318,7 @@ describe('AVRSimulator Mega — PWM OCR mapping differs from Uno', () => {
 
     (sim as any).pollPwmRegisters();
 
-    expect(cb).toHaveBeenCalledWith(5, 200 / 255);
+    expect(cb).toHaveBeenCalledWith(5, 200 / 255, expect.anything()); // 3rd arg = sim timeMs
     sim.stop();
   });
 
@@ -335,7 +335,7 @@ describe('AVRSimulator Mega — PWM OCR mapping differs from Uno', () => {
 
     (sim as any).pollPwmRegisters();
 
-    expect(cb).toHaveBeenCalledWith(6, 100 / 255);
+    expect(cb).toHaveBeenCalledWith(6, 100 / 255, expect.anything()); // 3rd arg = sim timeMs
     sim.stop();
   });
 });