diff --git a/lib/Logging/Logging.h b/lib/Logging/Logging.h
index 8784a341..6ad17323 100644
--- a/lib/Logging/Logging.h
+++ b/lib/Logging/Logging.h
@@ -27,7 +27,10 @@ won't trigger deprecation warnings.
 #define LOG_LEVEL 0
 #endif
 
-static HWCDC& logSerial = Serial;
+// The concrete Serial type differs by MCU: HWCDC (native USB CDC on C3/S3) vs
+// HardwareSerial (UART0 on the classic ESP32 / M5Paper). Bind to whatever the
+// real Serial is here — this is before the `#define Serial` shim below.
+static decltype(Serial)& logSerial = Serial;
 
 void logPrintf(const char* level, const char* origin, const char* format, ...);
 
diff --git a/lib/hal/HalGPIO.cpp b/lib/hal/HalGPIO.cpp
index b150dc8c..41026ad0 100644
--- a/lib/hal/HalGPIO.cpp
+++ b/lib/hal/HalGPIO.cpp
@@ -192,7 +192,13 @@ HalGPIO::DeviceType detectDeviceTypeWithFingerprint() {
 
 void HalGPIO::begin() {
   inputMgr.begin();
+#if !(defined(FREEINK_DEVICE_M5PAPER) && FREEINK_DEVICE_M5PAPER)
+  // Claim the shared SPI bus with the X4/X3 display+SD pins. On M5Paper the SDK's
+  // IT8951 driver and SDCardManager each bring up SPI from BoardConfig::ACTIVE
+  // pins; pre-claiming VSPI here would stick (SPIClass::begin early-returns if the
+  // bus is already started) and leave the SD card on the wrong pins.
   SPI.begin(EPD_SCLK, SPI_MISO, EPD_MOSI, EPD_CS);
+#endif
 
   _deviceType = detectDeviceTypeWithFingerprint();
 
@@ -232,12 +238,29 @@ void HalGPIO::startDeepSleep() {
     inputMgr.update();
   }
   // Arm the wakeup trigger *after* the button is released
+#if SOC_PM_SUPPORT_EXT1_WAKEUP
+  // Xtensa (classic ESP32 / S3): GPIO deep-sleep wake is via RTC ext1.
+  esp_sleep_enable_ext1_wakeup(1ULL << InputManager::POWER_BUTTON_PIN, ESP_EXT1_WAKEUP_ALL_LOW);
+#else
+  // RISC-V (C3): direct GPIO deep-sleep wakeup source.
   esp_deep_sleep_enable_gpio_wakeup(1ULL << InputManager::POWER_BUTTON_PIN, ESP_GPIO_WAKEUP_GPIO_LOW);
+#endif
   // Enter Deep Sleep
   esp_deep_sleep_start();
 }
 
 void HalGPIO::verifyPowerButtonWakeup(uint16_t requiredDurationMs, bool shortPressAllowed) {
+  if (BoardConfig::ACTIVE.input.power < 0) {
+    // No readable power-button input pin: can't verify a hold, so don't sleep.
+    return;
+  }
+#if defined(FREEINK_DEVICE_M5PAPER) && FREEINK_DEVICE_M5PAPER
+  // M5Paper: power-on is a hardware latch and the "power button" is the rotary
+  // push (G38), shared with Confirm. A USB/flash cold boot is indistinguishable
+  // from an intentional power-on hold here, so skip the X4-style anti-accidental-
+  // wake check and always boot. G38 still serves as the deep-sleep wake source.
+  return;
+#endif
   if (shortPressAllowed) {
     // Fast path - no duration check needed
     return;
diff --git a/lib/hal/HalPowerManager.cpp b/lib/hal/HalPowerManager.cpp
index 78f0018f..dec361dc 100644
--- a/lib/hal/HalPowerManager.cpp
+++ b/lib/hal/HalPowerManager.cpp
@@ -18,7 +18,9 @@ void HalPowerManager::begin() {
     Wire.setTimeOut(4);
     _batteryUseI2C = true;
   } else {
-    pinMode(BAT_GPIO0, INPUT);
+    // Battery ADC pin from the active board profile (X4: GPIO0, M5Paper: GPIO35),
+    // not a hardcoded X4 pin.
+    pinMode(BoardConfig::ACTIVE.batteryAdc, INPUT);
   }
   normalFreq = getCpuFrequencyMhz();
   modeMutex = xSemaphoreCreateMutex();
@@ -76,8 +78,10 @@ void HalPowerManager::startDeepSleep(HalGPIO& gpio) const {
 #endif
 
   // Pre-sleep routines from the original firmware
+#if !SOC_PM_SUPPORT_EXT1_WAKEUP  // RISC-V (C3 / X4)
   // GPIO13 is connected to battery latch MOSFET, we need to make sure it's low during sleep
   // Note that this means the MCU will be completely powered off during sleep, including RTC
+  // (X4-specific: on classic ESP32/M5Paper GPIO13 is SD MISO, so this is skipped.)
   constexpr gpio_num_t GPIO_SPIWP = GPIO_NUM_13;
   gpio_set_direction(GPIO_SPIWP, GPIO_MODE_OUTPUT);
   gpio_set_level(GPIO_SPIWP, 0);
@@ -90,6 +94,10 @@ void HalPowerManager::startDeepSleep(HalGPIO& gpio) const {
   // power button is hard-wired to briefly provide power to the MCU, waking it up regardless of the wakeup source
   // configuration
   esp_deep_sleep_enable_gpio_wakeup(1ULL << InputManager::POWER_BUTTON_PIN, ESP_GPIO_WAKEUP_GPIO_LOW);
+#else  // Xtensa (classic ESP32 / S3): RTC ext1 GPIO wake
+  pinMode(InputManager::POWER_BUTTON_PIN, INPUT_PULLUP);
+  esp_sleep_enable_ext1_wakeup(1ULL << InputManager::POWER_BUTTON_PIN, ESP_EXT1_WAKEUP_ALL_LOW);
+#endif
   // Enter Deep Sleep
   esp_deep_sleep_start();
 }
@@ -121,7 +129,8 @@ uint16_t HalPowerManager::getBatteryPercentage() const {
     _batteryLastPollMs = now;
     return _batteryCachedPercent;
   }
-  static const BatteryMonitor battery = BatteryMonitor(BAT_GPIO0);
+  // ADC pin from the active profile (X4 GPIO0 / M5Paper GPIO35); default 2:1 divider.
+  static const BatteryMonitor battery = BatteryMonitor(BoardConfig::ACTIVE.batteryAdc);
 
   // smooth the battery %.
   if (_batteryCachedPercent == 0) {
diff --git a/lib/hal/HalSystem.cpp b/lib/hal/HalSystem.cpp
index b92c95a1..c806c030 100644
--- a/lib/hal/HalSystem.cpp
+++ b/lib/hal/HalSystem.cpp
@@ -38,6 +38,13 @@ void IRAM_ATTR __wrap_panic_print_backtrace(const void* frame, int core) {
     __real_panic_print_backtrace(frame, core);
     return;
   }
+#if !__riscv
+  // RvExcFrame and the flat SP scan below are RISC-V-only (C3). On Xtensa
+  // (classic ESP32 / S3) the exception frame is XtExcFrame with windowed-register
+  // unwinding, so fall back to the default backtrace.
+  __real_panic_print_backtrace(frame, core);
+  return;
+#else
   for (size_t i = 0; i < MAX_PANIC_STACK_DEPTH; i++) {
     panicStack[i].sp = 0;
   }
@@ -65,6 +72,7 @@ void IRAM_ATTR __wrap_panic_print_backtrace(const void* frame, int core) {
   }
 
   __real_panic_print_backtrace(frame, core);
+#endif  // __riscv
 }
 }
 
diff --git a/src/activities/ActivityManager.cpp b/src/activities/ActivityManager.cpp
index 524ed3e0..0cf672c3 100644
--- a/src/activities/ActivityManager.cpp
+++ b/src/activities/ActivityManager.cpp
@@ -18,6 +18,13 @@
 #include "settings/SettingsActivity.h"
 #include "util/FullScreenMessageActivity.h"
 
+// taskENTER_CRITICAL needs a real spinlock on dual-core targets (classic ESP32,
+// e.g. M5Paper). On the single-core ESP32-C3 a nullptr mux was tolerated, but
+// the dual-core port acquires an inter-core spinlock and asserts on a null
+// pointer (spinlock_acquire, spinlock.h:84). One shared spinlock guards the
+// short waitingTaskHandle critical sections below.
+static portMUX_TYPE activityMux = portMUX_INITIALIZER_UNLOCKED;
+
 void ActivityManager::begin() {
   xTaskCreate(&renderTaskTrampoline, "ActivityManagerRender",
               8192,              // Stack size
@@ -45,10 +52,10 @@ void ActivityManager::renderTaskLoop() {
     }
     // Notify any task blocked in requestUpdateAndWait() that the render is done.
     TaskHandle_t waiter = nullptr;
-    taskENTER_CRITICAL(nullptr);
+    taskENTER_CRITICAL(&activityMux);
     waiter = waitingTaskHandle;
     waitingTaskHandle = nullptr;
-    taskEXIT_CRITICAL(nullptr);
+    taskEXIT_CRITICAL(&activityMux);
     if (waiter) {
       xTaskNotify(waiter, 1, eIncrement);
     }
@@ -279,7 +286,7 @@ void ActivityManager::requestUpdateAndWait() {
   }
 
   // Atomic section to perform checks
-  taskENTER_CRITICAL(nullptr);
+  taskENTER_CRITICAL(&activityMux);
   auto currTaskHandler = xTaskGetCurrentTaskHandle();
   auto mutexHolder = xSemaphoreGetMutexHolder(renderingMutex);
   bool isRenderTask = (currTaskHandler == renderTaskHandle);
@@ -288,7 +295,7 @@ void ActivityManager::requestUpdateAndWait() {
   if (!alreadyWaiting && !isRenderTask && !holdingRenderLock) {
     waitingTaskHandle = currTaskHandler;
   }
-  taskEXIT_CRITICAL(nullptr);
+  taskEXIT_CRITICAL(&activityMux);
 
   // Render task cannot call requestUpdateAndWait() or it will cause a deadlock
   assert(!isRenderTask && "Render task cannot call requestUpdateAndWait()");
diff --git a/src/components/themes/BaseTheme.cpp b/src/components/themes/BaseTheme.cpp
index 87d5af23..41f273bd 100644
--- a/src/components/themes/BaseTheme.cpp
+++ b/src/components/themes/BaseTheme.cpp
@@ -132,8 +132,27 @@ void BaseTheme::drawProgressBar(const GfxRenderer& renderer, Rect rect, const si
   renderer.drawCenteredText(UI_10_FONT_ID, rect.y + rect.height + 15, percentText.c_str());
 }
 
+// CROSSPOINT_SHOW_BUTTON_HINTS: build-flag switch (env). Default on. A device with
+// no physical button row (touch + rotary, e.g. M5Paper) builds with =0.
+#ifndef CROSSPOINT_SHOW_BUTTON_HINTS
+#define CROSSPOINT_SHOW_BUTTON_HINTS 1
+#endif
+bool BaseTheme::showButtonHints() { return CROSSPOINT_SHOW_BUTTON_HINTS; }
+
+// Non-virtual gates: one check hides hints across every theme. Themes override the
+// *Impl, which only ever runs when hints are enabled.
 void BaseTheme::drawButtonHints(GfxRenderer& renderer, const char* btn1, const char* btn2, const char* btn3,
                                 const char* btn4) const {
+  if (!showButtonHints()) return;
+  drawButtonHintsImpl(renderer, btn1, btn2, btn3, btn4);
+}
+void BaseTheme::drawSideButtonHints(const GfxRenderer& renderer, const char* topBtn, const char* bottomBtn) const {
+  if (!showButtonHints()) return;
+  drawSideButtonHintsImpl(renderer, topBtn, bottomBtn);
+}
+
+void BaseTheme::drawButtonHintsImpl(GfxRenderer& renderer, const char* btn1, const char* btn2, const char* btn3,
+                                    const char* btn4) const {
   const GfxRenderer::Orientation orig_orientation = renderer.getOrientation();
   renderer.setOrientation(GfxRenderer::Orientation::Portrait);
 
@@ -163,7 +182,7 @@ void BaseTheme::drawButtonHints(GfxRenderer& renderer, const char* btn1, const c
   renderer.setOrientation(orig_orientation);
 }
 
-void BaseTheme::drawSideButtonHints(const GfxRenderer& renderer, const char* topBtn, const char* bottomBtn) const {
+void BaseTheme::drawSideButtonHintsImpl(const GfxRenderer& renderer, const char* topBtn, const char* bottomBtn) const {
   const int screenWidth = renderer.getScreenWidth();
   constexpr int buttonWidth = BaseMetrics::values.sideButtonHintsWidth;  // Width on screen (height when rotated)
   constexpr int buttonHeight = 80;                                       // Height on screen (width when rotated)
diff --git a/src/components/themes/BaseTheme.h b/src/components/themes/BaseTheme.h
index e140bc26..75c6d1be 100644
--- a/src/components/themes/BaseTheme.h
+++ b/src/components/themes/BaseTheme.h
@@ -179,9 +179,19 @@ class BaseTheme {
   void drawBatteryRight(const GfxRenderer& renderer, Rect rect,
                         bool showPercentage = true) const;  // Right aligned (UI headers)
   virtual void fillBatteryIcon(const GfxRenderer& renderer, Rect rect, uint16_t percentage) const;
-  virtual void drawButtonHints(GfxRenderer& renderer, const char* btn1, const char* btn2, const char* btn3,
-                               const char* btn4) const;
-  virtual void drawSideButtonHints(const GfxRenderer& renderer, const char* topBtn, const char* bottomBtn) const;
+  // Single switch for on-screen button hints, set by the CROSSPOINT_SHOW_BUTTON_HINTS
+  // build flag (env; default on). Devices with no physical button row (touch +
+  // rotary, e.g. M5Paper) set it to 0 in their env.
+  static bool showButtonHints();
+  // Public, NON-virtual gate: returns early when hints are disabled, otherwise
+  // dispatches to the per-theme *Impl below. Themes override the *Impl, never
+  // these — so one switch hides hints across every theme.
+  void drawButtonHints(GfxRenderer& renderer, const char* btn1, const char* btn2, const char* btn3,
+                       const char* btn4) const;
+  void drawSideButtonHints(const GfxRenderer& renderer, const char* topBtn, const char* bottomBtn) const;
+  virtual void drawButtonHintsImpl(GfxRenderer& renderer, const char* btn1, const char* btn2, const char* btn3,
+                                   const char* btn4) const;
+  virtual void drawSideButtonHintsImpl(const GfxRenderer& renderer, const char* topBtn, const char* bottomBtn) const;
   virtual int getListPageItems(int contentHeight, bool hasSubtitle) const;
   virtual void drawList(const GfxRenderer& renderer, Rect rect, int itemCount, int selectedIndex,
                         const std::function<std::string(int index)>& rowTitle,
diff --git a/src/components/themes/lyra/LyraTheme.cpp b/src/components/themes/lyra/LyraTheme.cpp
index f04f7de0..a39d0f5e 100644
--- a/src/components/themes/lyra/LyraTheme.cpp
+++ b/src/components/themes/lyra/LyraTheme.cpp
@@ -317,8 +317,8 @@ void LyraTheme::drawList(const GfxRenderer& renderer, Rect rect, int itemCount,
   }
 }
 
-void LyraTheme::drawButtonHints(GfxRenderer& renderer, const char* btn1, const char* btn2, const char* btn3,
-                                const char* btn4) const {
+void LyraTheme::drawButtonHintsImpl(GfxRenderer& renderer, const char* btn1, const char* btn2, const char* btn3,
+                                    const char* btn4) const {
   const GfxRenderer::Orientation orig_orientation = renderer.getOrientation();
   renderer.setOrientation(GfxRenderer::Orientation::Portrait);
 
@@ -356,7 +356,7 @@ void LyraTheme::drawButtonHints(GfxRenderer& renderer, const char* btn1, const c
   renderer.setOrientation(orig_orientation);
 }
 
-void LyraTheme::drawSideButtonHints(const GfxRenderer& renderer, const char* topBtn, const char* bottomBtn) const {
+void LyraTheme::drawSideButtonHintsImpl(const GfxRenderer& renderer, const char* topBtn, const char* bottomBtn) const {
   const int screenWidth = renderer.getScreenWidth();
   constexpr int buttonWidth = LyraMetrics::values.sideButtonHintsWidth;  // Width on screen (height when rotated)
   constexpr int buttonHeight = 78;                                       // Height on screen (width when rotated)
diff --git a/src/components/themes/lyra/LyraTheme.h b/src/components/themes/lyra/LyraTheme.h
index fbed8f42..0cfb3bb0 100644
--- a/src/components/themes/lyra/LyraTheme.h
+++ b/src/components/themes/lyra/LyraTheme.h
@@ -84,9 +84,9 @@ class LyraTheme : public BaseTheme {
                 const std::function<std::string(int index)>& rowSubtitle,
                 const std::function<UIIcon(int index)>& rowIcon, const std::function<std::string(int index)>& rowValue,
                 bool highlightValue, const std::function<bool(int index)>& rowDimmed = nullptr) const override;
-  void drawButtonHints(GfxRenderer& renderer, const char* btn1, const char* btn2, const char* btn3,
-                       const char* btn4) const override;
-  void drawSideButtonHints(const GfxRenderer& renderer, const char* topBtn, const char* bottomBtn) const override;
+  void drawButtonHintsImpl(GfxRenderer& renderer, const char* btn1, const char* btn2, const char* btn3,
+                           const char* btn4) const override;
+  void drawSideButtonHintsImpl(const GfxRenderer& renderer, const char* topBtn, const char* bottomBtn) const override;
   void drawButtonMenu(GfxRenderer& renderer, Rect rect, int buttonCount, int selectedIndex,
                       const std::function<std::string(int index)>& buttonLabel,
                       const std::function<UIIcon(int index)>& rowIcon) const override;
diff --git a/src/components/themes/roundedraff/RoundedRaffTheme.cpp b/src/components/themes/roundedraff/RoundedRaffTheme.cpp
index 50db2a8c..4a46f459 100644
--- a/src/components/themes/roundedraff/RoundedRaffTheme.cpp
+++ b/src/components/themes/roundedraff/RoundedRaffTheme.cpp
@@ -381,8 +381,8 @@ void RoundedRaffTheme::drawList(const GfxRenderer& renderer, Rect rect, int item
   drawScrollBar(renderer, rect, itemCount, pageStartIndex, pageItems);
 }
 
-void RoundedRaffTheme::drawButtonHints(GfxRenderer& renderer, const char* btn1, const char* btn2, const char* btn3,
-                                       const char* btn4) const {
+void RoundedRaffTheme::drawButtonHintsImpl(GfxRenderer& renderer, const char* btn1, const char* btn2, const char* btn3,
+                                           const char* btn4) const {
   const GfxRenderer::Orientation origOrientation = renderer.getOrientation();
   renderer.setOrientation(GfxRenderer::Orientation::Portrait);
 
diff --git a/src/components/themes/roundedraff/RoundedRaffTheme.h b/src/components/themes/roundedraff/RoundedRaffTheme.h
index 3f916a26..5de7f138 100644
--- a/src/components/themes/roundedraff/RoundedRaffTheme.h
+++ b/src/components/themes/roundedraff/RoundedRaffTheme.h
@@ -92,7 +92,7 @@ class RoundedRaffTheme : public BaseTheme {
                 const std::function<UIIcon(int index)>& rowIcon = nullptr,
                 const std::function<std::string(int index)>& rowValue = nullptr, bool highlightValue = false,
                 const std::function<bool(int index)>& rowDimmed = nullptr) const override;
-  void drawButtonHints(GfxRenderer& renderer, const char* btn1, const char* btn2, const char* btn3,
-                       const char* btn4) const override;
+  void drawButtonHintsImpl(GfxRenderer& renderer, const char* btn1, const char* btn2, const char* btn3,
+                           const char* btn4) const override;
   bool homeMenuShowsContinueReading() const { return true; }
 };
diff --git a/src/main.cpp b/src/main.cpp
index cb1d9b23..9c71ba13 100644
--- a/src/main.cpp
+++ b/src/main.cpp
@@ -305,6 +305,14 @@ void setupDisplayAndFonts(bool seamless = false) {
 void setup() {
   t1 = millis();
 
+#if defined(FREEINK_DEVICE_M5PAPER) && FREEINK_DEVICE_M5PAPER
+  // M5Paper v1.1 latches its own power through a MOSFET on GPIO2. Drive it HIGH
+  // first thing or the board powers off the instant USB is unplugged. (Board
+  // responsibility, not the SDK — see freeink-sdk platformio.sample.ini.)
+  pinMode(2, OUTPUT);
+  digitalWrite(2, HIGH);
+#endif
+
 #ifdef ENABLE_SERIAL_LOG
   // Earliest possible Serial setup. The 250 ms stall before begin() lets the
   // USB Serial/JTAG peripheral finish power-on and lets the host complete USB
@@ -313,7 +321,11 @@ void setup() {
   // worked without the delay because USB was already enumerated.
   delay(250);
   Serial.begin(115200);
+#if defined(ARDUINO_USB_CDC_ON_BOOT) && ARDUINO_USB_CDC_ON_BOOT
+  // setTxTimeoutMs is an HWCDC (native USB CDC) method. On the classic ESP32
+  // (M5Paper) Serial is UART0/HardwareSerial, which has no such method.
   logSerial.setTxTimeoutMs(1);  // This is a load-bearing 1. Do not modify.
+#endif
 #endif
 
   HalSystem::begin();