diff --git a/backend/app/services/esp32_worker.py b/backend/app/services/esp32_worker.py
index c844d6d..795864c 100644
--- a/backend/app/services/esp32_worker.py
+++ b/backend/app/services/esp32_worker.py
@@ -421,14 +421,14 @@ def main() -> None:  # noqa: C901  (complexity OK for inline worker)
                     _dht22_sync_step()
                 return  # always return for GPIO_IN syncs (fast path)
             marker = direction & 0xF000
-            if marker == 0x2000:  # GPIO_FUNCX_OUT_SEL_CFG change
-                gpio_pin = direction & 0xFF
-                signal   = (direction >> 8) & 0xFF
-                # Signal 72-79 = LEDC HS ch 0-7; 80-87 = LEDC LS ch 0-7
-                if 72 <= signal <= 87:
-                    ledc_ch = signal - 72  # ch 0-15
-                    _ledc_gpio_map[ledc_ch] = gpio_pin
-                    _log(f'LEDC map: ch{ledc_ch} → GPIO{gpio_pin} (signal={signal})')
+            if marker == 0x5000:  # LEDC duty change (from esp32_ledc.c)
+                ledc_ch = (direction >> 8) & 0x0F
+                intensity = direction & 0xFF  # 0-100 percentage
+                gpio = _ledc_gpio_map.get(ledc_ch, -1)
+                _emit({'type': 'ledc_update', 'channel': ledc_ch,
+                       'duty': intensity,
+                       'duty_pct': intensity,
+                       'gpio': gpio})
             return
 
         # ── DHT22: track direction changes + trigger sync response ───────
@@ -588,25 +588,36 @@ def main() -> None:  # noqa: C901  (complexity OK for inline worker)
         # Track last-emitted duty to avoid flooding identical updates
         _last_duty = [0.0] * 16
         _diag_count = [0]
+        _first_nonzero_logged = [False]
         _log('LEDC poll thread started')
         while not _stopped.wait(0.1):
             try:
                 ptr = lib.qemu_picsimlab_get_internals(6)  # LEDC_CHANNEL_DUTY
                 _diag_count[0] += 1
-                # Log first 5 polls for diagnostics
-                if _diag_count[0] <= 5:
-                    _log(f'LEDC poll #{_diag_count[0]}: ptr={ptr} '
-                         f'(type={type(ptr).__name__}) gpio_map={dict(_ledc_gpio_map)}')
                 if ptr is None or ptr == 0:
-                    if _diag_count[0] <= 5:
-                        _log(f'LEDC poll: ptr is NULL/0, skipping')
                     continue
                 # duty[] is float[16] in QEMU (percentage 0-100)
                 arr = (ctypes.c_float * 16).from_address(ptr)
-                if _diag_count[0] <= 5:
+                # Refresh LEDC→GPIO mapping from gpio_out_sel[40] registers
+                out_sel_ptr = lib.qemu_picsimlab_get_internals(2)
+                if out_sel_ptr:
+                    out_sel = (ctypes.c_uint32 * 40).from_address(out_sel_ptr)
+                    for gpio_pin in range(40):
+                        signal = int(out_sel[gpio_pin]) & 0xFF
+                        # Signal 72-79 = LEDC HS ch 0-7; 80-87 = LEDC LS ch 0-7
+                        if 72 <= signal <= 87:
+                            ledc_ch = signal - 72
+                            if _ledc_gpio_map.get(ledc_ch) != gpio_pin:
+                                _ledc_gpio_map[ledc_ch] = gpio_pin
+                                _log(f'LEDC map: ch{ledc_ch} → GPIO{gpio_pin} (signal={signal})')
+                # Log once when nonzero duties first appear
+                if not _first_nonzero_logged[0]:
                     nonzero = {ch: round(float(arr[ch]), 2) for ch in range(16)
                                if float(arr[ch]) != 0.0}
-                    _log(f'LEDC poll: nonzero duties={nonzero}')
+                    if nonzero:
+                        _log(f'LEDC first nonzero at poll #{_diag_count[0]}: '
+                             f'duties={nonzero} gpio_map={dict(_ledc_gpio_map)}')
+                        _first_nonzero_logged[0] = True
                 for ch in range(16):
                     duty_pct = float(arr[ch])
                     if abs(duty_pct - _last_duty[ch]) < 0.01:
diff --git a/frontend/src/__tests__/esp32-servo-pot.test.ts b/frontend/src/__tests__/esp32-servo-pot.test.ts
index a022d97..27c6aee 100644
--- a/frontend/src/__tests__/esp32-servo-pot.test.ts
+++ b/frontend/src/__tests__/esp32-servo-pot.test.ts
@@ -470,7 +470,201 @@ describe('ESP32 ADC channel mapping', () => {
 });
 
 // ─────────────────────────────────────────────────────────────────────────────
-// 10. LEDC polling — data type and internal config
+// 10. LEDC 0x5000 marker decoding — channel extraction fix
+// ─────────────────────────────────────────────────────────────────────────────
+
+describe('LEDC 0x5000 marker decoding', () => {
+  // QEMU fires: qemu_set_irq(ledc_sync, 0x5000 | (ledn << 8) | intensity)
+  // Worker must extract: ledc_ch = (direction >> 8) & 0x0F (NOT & 0xFF)
+
+  function decodeLedc(direction: number) {
+    const marker = direction & 0xF000;
+    if (marker !== 0x5000) return null;
+    const ledc_ch = (direction >> 8) & 0x0F;  // correct: strips marker bits
+    const intensity = direction & 0xFF;
+    return { ledc_ch, intensity };
+  }
+
+  function decodeLedcBroken(direction: number) {
+    const marker = direction & 0xF000;
+    if (marker !== 0x5000) return null;
+    const ledc_ch = (direction >> 8) & 0xFF;  // BUG: includes marker bits
+    const intensity = direction & 0xFF;
+    return { ledc_ch, intensity };
+  }
+
+  it('HS channel 0 (ledn=0): direction=0x500B → ch=0, not ch=80', () => {
+    const direction = 0x5000 | (0 << 8) | 11; // 0x500B
+    const correct = decodeLedc(direction)!;
+    const broken = decodeLedcBroken(direction)!;
+
+    expect(correct.ledc_ch).toBe(0);   // correct
+    expect(broken.ledc_ch).toBe(80);   // BUG: 0x50 = 80
+    expect(correct.intensity).toBe(11);
+  });
+
+  it('LS channel 0 (ledn=8): direction=0x5811 → ch=8, not ch=88', () => {
+    const direction = 0x5000 | (8 << 8) | 17; // 0x5811
+    const correct = decodeLedc(direction)!;
+    const broken = decodeLedcBroken(direction)!;
+
+    expect(correct.ledc_ch).toBe(8);   // correct
+    expect(broken.ledc_ch).toBe(88);   // BUG: 0x58 = 88
+    expect(correct.intensity).toBe(17);
+  });
+
+  it('HS channel 7 (ledn=7): direction=0x5732 → ch=7', () => {
+    const direction = 0x5000 | (7 << 8) | 50; // 0x5732
+    expect(decodeLedc(direction)!.ledc_ch).toBe(7);
+    expect(decodeLedc(direction)!.intensity).toBe(50);
+  });
+
+  it('LS channel 7 (ledn=15): direction=0x5F64 → ch=15', () => {
+    const direction = 0x5000 | (15 << 8) | 100; // 0x5F64
+    expect(decodeLedc(direction)!.ledc_ch).toBe(15);
+    expect(decodeLedc(direction)!.intensity).toBe(100);
+  });
+
+  it('all 16 channels decode correctly', () => {
+    for (let ledn = 0; ledn < 16; ledn++) {
+      const direction = 0x5000 | (ledn << 8) | 42;
+      const result = decodeLedc(direction)!;
+      expect(result.ledc_ch).toBe(ledn);
+      expect(result.intensity).toBe(42);
+    }
+  });
+});
+
+// ─────────────────────────────────────────────────────────────────────────────
+// 11. GPIO out_sel scanning — LEDC→GPIO mapping
+// ─────────────────────────────────────────────────────────────────────────────
+
+describe('GPIO out_sel scanning for LEDC mapping', () => {
+  // Simulates what the LEDC poll thread does: read gpio_out_sel[40] and
+  // scan for LEDC signal values (72-87) to build _ledc_gpio_map
+
+  function scanOutSel(outSel: number[]): Map<number, number> {
+    const ledcGpioMap = new Map<number, number>();
+    for (let gpioPin = 0; gpioPin < outSel.length; gpioPin++) {
+      const signal = outSel[gpioPin] & 0xFF;
+      if (signal >= 72 && signal <= 87) {
+        const ledcCh = signal - 72;
+        ledcGpioMap.set(ledcCh, gpioPin);
+      }
+    }
+    return ledcGpioMap;
+  }
+
+  it('detects LEDC HS ch0 (signal=72) on GPIO 13', () => {
+    const outSel = new Array(40).fill(256); // 256 = no function
+    outSel[13] = 72; // LEDC HS ch0 → GPIO 13
+    const map = scanOutSel(outSel);
+
+    expect(map.get(0)).toBe(13);
+    expect(map.size).toBe(1);
+  });
+
+  it('detects LEDC LS ch0 (signal=80) on GPIO 2', () => {
+    const outSel = new Array(40).fill(256);
+    outSel[2] = 80; // LEDC LS ch0 → GPIO 2
+    const map = scanOutSel(outSel);
+
+    expect(map.get(8)).toBe(2); // ch8 = LS ch0
+  });
+
+  it('detects multiple LEDC channels', () => {
+    const outSel = new Array(40).fill(256);
+    outSel[13] = 72;  // HS ch0 → GPIO 13
+    outSel[12] = 73;  // HS ch1 → GPIO 12
+    outSel[14] = 80;  // LS ch0 → GPIO 14
+    const map = scanOutSel(outSel);
+
+    expect(map.get(0)).toBe(13);
+    expect(map.get(1)).toBe(12);
+    expect(map.get(8)).toBe(14);
+    expect(map.size).toBe(3);
+  });
+
+  it('ignores non-LEDC signals (< 72 or > 87)', () => {
+    const outSel = new Array(40).fill(256);
+    outSel[5] = 71;  // signal 71 = not LEDC
+    outSel[6] = 88;  // signal 88 = not LEDC
+    outSel[7] = 0;   // signal 0 = GPIO matrix simple
+    const map = scanOutSel(outSel);
+
+    expect(map.size).toBe(0);
+  });
+
+  it('explains why 0x2000 marker was broken for LEDC signals', () => {
+    // QEMU fires: 0x2000 | ((signal & 0xFF) << 8) | (gpio & 0xFF)
+    // For signal=72 (0x48), gpio=13: direction = 0x2000 | 0x4800 | 0x0D = 0x680D
+    // marker = direction & 0xF000 = 0x6000 ≠ 0x2000 → NEVER MATCHED!
+    const signal = 72;
+    const gpio = 13;
+    const direction = 0x2000 | ((signal & 0xFF) << 8) | (gpio & 0xFF);
+
+    expect(direction).toBe(0x680D);
+    expect(direction & 0xF000).toBe(0x6000); // NOT 0x2000!
+    expect(direction & 0xF000).not.toBe(0x2000); // confirms the bug
+  });
+});
+
+// ─────────────────────────────────────────────────────────────────────────────
+// 12. End-to-end: LEDC update with correct GPIO routes to servo
+// ─────────────────────────────────────────────────────────────────────────────
+
+describe('End-to-end: LEDC → servo angle', () => {
+  const logic = () => PartSimulationRegistry.get('servo')!;
+
+  it('ledc_update with gpio=13 → updatePwm(13, duty) → servo moves', () => {
+    const shim = makeEsp32Shim();
+    const el = makeElement() as any;
+    logic().attachEvents!(el, shim as any, pinMap({ PWM: 13 }), 'servo-e2e');
+
+    // Simulate what useSimulatorStore.onLedcUpdate does:
+    const update = { channel: 0, duty: 7.36, duty_pct: 7.36, gpio: 13 };
+    const targetPin = (update.gpio >= 0) ? update.gpio : update.channel;
+    const dutyCycleFraction = update.duty_pct / 100;
+
+    // This is what the store calls:
+    shim.pinManager.updatePwm(targetPin, dutyCycleFraction);
+
+    // The servo's onPwmChange callback should have been triggered
+    const cb = shim._getPwmCallback();
+    expect(cb).not.toBeNull();
+
+    // Manually invoke the callback (simulating PinManager dispatching)
+    cb!(13, dutyCycleFraction);
+
+    // 7.36% duty = 1472µs pulse → ~90°
+    expect(el.angle).toBeGreaterThanOrEqual(88);
+    expect(el.angle).toBeLessThanOrEqual(92);
+  });
+
+  it('ledc_update with WRONG ch=80 and gpio=-1 would NOT reach servo on pin 13', () => {
+    // This demonstrates the bug that was fixed:
+    // ch=80 (from broken & 0xFF) with gpio=-1 → updatePwm(80, duty)
+    // But servo listens on pin 13 → callback never fires
+    const shim = makeEsp32Shim();
+    const el = makeElement() as any;
+    logic().attachEvents!(el, shim as any, pinMap({ PWM: 13 }), 'servo-bug-demo');
+
+    const cb = shim._getPwmCallback();
+
+    // With the bug: updatePwm would be called with pin=80 (wrong)
+    // The servo registered on pin 13, so this would NOT trigger it
+    // (PinManager only dispatches to callbacks registered for that pin)
+    expect(cb).not.toBeNull();
+
+    // Calling with wrong pin does nothing (servo registered on 13, not 80)
+    cb!(80, 0.075); // wrong pin
+    // angle still 0 since the real PinManager wouldn't route pin 80 to pin 13's callback
+    // (In our mock, the callback is directly invoked, but in production it wouldn't fire)
+  });
+});
+
+// ─────────────────────────────────────────────────────────────────────────────
+// 13. LEDC polling — data type and internal config
 // ─────────────────────────────────────────────────────────────────────────────
 
 describe('LEDC polling — data format', () => {