diff --git a/lib/hal/HalPowerManager.cpp b/lib/hal/HalPowerManager.cpp
index c09158a7..16df2518 100644
--- a/lib/hal/HalPowerManager.cpp
+++ b/lib/hal/HalPowerManager.cpp
@@ -64,6 +64,14 @@ void HalPowerManager::setPowerSaving(bool enabled) {
 void HalPowerManager::startDeepSleep(HalGPIO& gpio, bool keepClockAlive) const {
   LOG_DBG("PWR", "startDeepSleep: isPressed=%d, rawPin=%d, keepClock=%d", gpio.isPressed(HalGPIO::BTN_POWER),
           digitalRead(InputManager::POWER_BUTTON_PIN) == LOW, keepClockAlive);
+
+#ifdef ENABLE_SERIAL_LOG
+  // Tear down HWCDC so the host sees a clean disconnect and the peripheral
+  // doesn't hold power domains that interfere with USB-powered GPIO wake.
+  // logSerial is the raw HWCDC reference; Serial is the MySerialImpl proxy
+  // (which doesn't expose end()).
+  logSerial.end();
+#endif
   // Perform all hardware preparation immediately (while the button may still be held)
   // so the user gets instant visual feedback (display already off). Only block for
   // button release at the very end, right before entering sleep.
@@ -96,7 +104,6 @@ void HalPowerManager::startDeepSleep(HalGPIO& gpio, bool keepClockAlive) const {
   // regardless of the wakeup source configuration.
   // When keepClockAlive is true, this is the actual wakeup mechanism since the MCU stays powered.
   esp_deep_sleep_enable_gpio_wakeup(1ULL << InputManager::POWER_BUTTON_PIN, ESP_GPIO_WAKEUP_GPIO_LOW);
-  LOG_DBG("PWR", "startDeepSleep: entering deep sleep now");
   // Enter Deep Sleep
   esp_deep_sleep_start();
 }
diff --git a/src/main.cpp b/src/main.cpp
index bdf1833a..64b46191 100644
--- a/src/main.cpp
+++ b/src/main.cpp
@@ -14,6 +14,7 @@
 #include <I18n.h>
 #include <Logging.h>
 #include <SPI.h>
+#include <WiFi.h>
 #include <builtinFonts/all.h>
 #include <esp_ota_ops.h>
 
@@ -165,7 +166,12 @@ void enterDeepSleep() {
     APP_STATE.readerActivityLoadCount = 0;
   }
   APP_STATE.saveToFile();
-
+  // Tear down WiFi so the modem power domain isn't held alive across deep sleep.
+  // Wake from deep sleep is effectively a chip reset, so no state needs to survive.
+  if (WiFi.getMode() != WIFI_MODE_NULL) {
+    WiFi.disconnect(true);
+    WiFi.mode(WIFI_OFF);
+  }
   activityManager.goToSleep();
   halTiltSensor.deepSleep();