diff --git a/lib/hal/HalGPIO.cpp b/lib/hal/HalGPIO.cpp
index 911d5543..7cefa64d 100644
--- a/lib/hal/HalGPIO.cpp
+++ b/lib/hal/HalGPIO.cpp
@@ -309,22 +309,29 @@ void HalGPIO::verifyPowerButtonWakeup(uint16_t requiredDurationMs, bool shortPre
 
 bool HalGPIO::isUsbConnected() const {
   if (deviceIsX3()) {
-    // X3: infer USB/charging via BQ27220 Current() register (0x0C, signed mA).
-    // Positive current means charging.
+    // X3: GPIO20 is repurposed as I2C SDA, so the X4 pin-level USB detect is
+    // unusable here — the I2C pull-ups would always report HIGH. Probe the
+    // BQ27220 fuel gauge instead. Using just Current() mis-reports "not
+    // connected" when the battery is full (current ~= 0 mA); combine it with
+    // the Flags() DSG bit so we report true whenever the charger is present
+    // (DSG=0 means charging or fully charged, not discharging).
     for (uint8_t attempt = 0; attempt < 2; ++attempt) {
-      int16_t currentMa = 0;
-      if (X3GPIO::readBQ27220CurrentMA(&currentMa)) {
-        if (currentMa > 0) {
+      uint16_t flags = 0;
+      if (X3GPIO::readI2CReg16LE(I2C_ADDR_BQ27220, BQ27220_FLAGS_REG, &flags)) {
+        if ((flags & BQ27220_FLAG_DSG) == 0) {
           return true;
         }
-        break;
+        int16_t currentMa = 0;
+        if (X3GPIO::readBQ27220CurrentMA(&currentMa) && currentMa > 0) {
+          return true;
+        }
+        return false;
       }
       delay(2);
     }
-    // Fall back to the same USB pin-level detection used by X4.
-    return digitalRead(UART0_RXD) == HIGH;
+    return false;
   }
-  // U0RXD/GPIO20 reads HIGH when USB is connected
+  // X4: U0RXD/GPIO20 reads HIGH when USB is connected
   return digitalRead(UART0_RXD) == HIGH;
 }
 
@@ -336,6 +343,13 @@ HalGPIO::WakeupReason HalGPIO::getWakeupReason() const {
   LOG_DBG("GPIO", "getWakeupReason: wakeupCause=%d, resetReason=%d, usbConnected=%d", static_cast<int>(wakeupCause),
           static_cast<int>(resetReason), usbConnected);
 
+  // X3: USB alone cannot cold-boot the MCU — the battery-latch MOSFET must be
+  // closed by a physical power-button press. So any POWERON reset on X3 is a
+  // button press, regardless of whether USB happens to be plugged in as well.
+  if (deviceIsX3() && wakeupCause == ESP_SLEEP_WAKEUP_UNDEFINED && resetReason == ESP_RST_POWERON) {
+    return WakeupReason::PowerButton;
+  }
+
   if ((wakeupCause == ESP_SLEEP_WAKEUP_UNDEFINED && resetReason == ESP_RST_POWERON && !usbConnected) ||
       (wakeupCause == ESP_SLEEP_WAKEUP_GPIO && resetReason == ESP_RST_DEEPSLEEP && usbConnected)) {
     return WakeupReason::PowerButton;
diff --git a/lib/hal/HalGPIO.h b/lib/hal/HalGPIO.h
index 3653a730..26079ab4 100644
--- a/lib/hal/HalGPIO.h
+++ b/lib/hal/HalGPIO.h
@@ -23,10 +23,12 @@
 #define X3_I2C_FREQ 400000
 
 // TI BQ27220 Fuel gauge I2C
-#define I2C_ADDR_BQ27220 0x55  // Fuel gauge I2C address
-#define BQ27220_SOC_REG 0x2C   // StateOfCharge() command code (%)
-#define BQ27220_CUR_REG 0x0C   // Current() command code (signed mA)
-#define BQ27220_VOLT_REG 0x08  // Voltage() command code (mV)
+#define I2C_ADDR_BQ27220 0x55    // Fuel gauge I2C address
+#define BQ27220_SOC_REG 0x2C     // StateOfCharge() command code (%)
+#define BQ27220_CUR_REG 0x0C     // Current() command code (signed mA)
+#define BQ27220_VOLT_REG 0x08    // Voltage() command code (mV)
+#define BQ27220_FLAGS_REG 0x0A   // BatteryStatus() / Flags() command code (bit0=DSG)
+#define BQ27220_FLAG_DSG 0x0001  // DSG bit: 1 = discharging, 0 = charging or at rest
 
 // Analog DS3231 RTC I2C
 #define I2C_ADDR_DS3231 0x68  // RTC I2C address