diff --git a/zephcore/Kconfig b/zephcore/Kconfig
index 3509ae9..b767cb6 100644
--- a/zephcore/Kconfig
+++ b/zephcore/Kconfig
@@ -52,6 +52,27 @@ config GNSS_LUATOS_AIR530Z_NAV_MODE
 	default ZEPHCORE_GPS_NAV_MODE
 	depends on GNSS_LUATOS_AIR530Z
 
+# Defaults rather than conf-file assignments for symbols that exist only on some
+# builds: an assignment to an invisible symbol is a Kconfig warning on every
+# other build. Ahead of Kconfig.zephyr so they beat the upstream defaults. Each
+# repeats the upstream `depends on`: a definition without it would make the
+# symbol exist on every build (Kconfig ORs the dependencies of all definitions).
+# USB device stack at WRN when logging is on: INF logs every CH9 control transfer.
+choice USBD_LOG_LEVEL_CHOICE
+	default USBD_LOG_LEVEL_WRN
+endchoice
+
+# QSPI NOR boards: 4 KB sector erase instead of the 64 KB block default, which
+# suits LittleFS on small partitions.
+config NORDIC_QSPI_NOR_FLASH_LAYOUT_PAGE_SIZE
+	depends on NORDIC_QSPI_NOR
+	default 4096
+
+# Power-off wherever the SoC supports it (not on MG24).
+config POWEROFF
+	depends on HAS_POWEROFF
+	default y
+
 source "$(ZEPHYR_BASE)/Kconfig.zephyr"
 
 # DT-driven PSRAM auto-enable for ESP32 boards (see Kconfig.psram).
diff --git a/zephcore/boards/common/nrf52_common.conf b/zephcore/boards/common/nrf52_common.conf
index 4a4ea51..d58b622 100644
--- a/zephcore/boards/common/nrf52_common.conf
+++ b/zephcore/boards/common/nrf52_common.conf
@@ -49,11 +49,7 @@ CONFIG_SOC_FLASH_NRF_PARTIAL_ERASE=y
 # QSPI flash — auto-detected from devicetree. Boards with a nordic,qspi-nor
 # node get the driver automatically (Zephyr default y when DT node exists).
 # Boards without QSPI in DTS stay disabled — no override needed either way.
-#
-# Page size: 4096 (sector erase) instead of Zephyr default 65536 (block erase).
-# LittleFS works much better with 4KB erase granularity on small partitions.
-# Silently ignored when QSPI is not present (Kconfig guard: if NORDIC_QSPI_NOR).
-CONFIG_NORDIC_QSPI_NOR_FLASH_LAYOUT_PAGE_SIZE=4096
+# Page size 4096 instead of the 64 KB block default: zephcore/Kconfig.
 
 # ========== Debug ==========
 # SEGGER RTT and CONFIG_ASSERT are debug-only and live in boards/common/debug.conf
diff --git a/zephcore/boards/common/zephcore_common.conf b/zephcore/boards/common/zephcore_common.conf
index fd5e03f..426f388 100644
--- a/zephcore/boards/common/zephcore_common.conf
+++ b/zephcore/boards/common/zephcore_common.conf
@@ -221,12 +221,8 @@ CONFIG_INPUT_MODE_SYNCHRONOUS=y
 # ========== Logging ==========
 # Log backend tuning lives in boards/common/debug.conf (opt-in).
 
-# Silence USB CH9 control-transfer spam (dozens of INF lines during enumeration).
-# WRN keeps real USB errors visible.
-CONFIG_USBD_LOG_LEVEL_WRN=y
-
 # ========== Power Management ==========
-CONFIG_POWEROFF=y
+# CONFIG_POWEROFF: default y where the SoC has it (zephcore/Kconfig).
 
 # ========== LoRa Power Saving ==========
 # RX duty cycle defaults are in Kconfig:
diff --git a/zephcore/boards/nrf52840/lilygo_techo/board.conf b/zephcore/boards/nrf52840/lilygo_techo/board.conf
index 682a971..179fe32 100644
--- a/zephcore/boards/nrf52840/lilygo_techo/board.conf
+++ b/zephcore/boards/nrf52840/lilygo_techo/board.conf
@@ -26,9 +26,6 @@ CONFIG_ZEPHCORE_SD_FWID=0x00B6
 # Default heap (2048) is sized for SSD1306 128x64 (1024 bytes).
 CONFIG_HEAP_MEM_POOL_SIZE=6144
 
-# Shrink RTT buffer to free RAM (4096 → 1024, saves 3KB).
-CONFIG_SEGGER_RTT_BUFFER_SIZE_UP=1024
-
 # ========== Display cosmetics ==========
 # 200x200 SSD1681 — the default 6x8 font is too small to read comfortably.
 # Switch to the smallest Zephyr built-in CFB font >= 16 px (typically 10x16).
diff --git a/zephcore/boards/nrf52840/thinknode_m1/board.conf b/zephcore/boards/nrf52840/thinknode_m1/board.conf
index 6c0771b..7fcc4f7 100644
--- a/zephcore/boards/nrf52840/thinknode_m1/board.conf
+++ b/zephcore/boards/nrf52840/thinknode_m1/board.conf
@@ -22,10 +22,6 @@ CONFIG_ZEPHCORE_SD_FWID=0x00B6
 # Default heap (2048) is sized for SSD1306 128x64 (1024 bytes).
 CONFIG_HEAP_MEM_POOL_SIZE=6144
 
-# Shrink RTT buffer to free RAM (4096 → 1024, saves 3KB).
-# Only used during J-Link debugging, 1KB is Zephyr's default.
-CONFIG_SEGGER_RTT_BUFFER_SIZE_UP=1024
-
 # ========== UI / display ==========
 # 200x200 SSD1681 — the default 6x8 font is too small to read comfortably.
 # Switch to the smallest Zephyr built-in CFB font >= 16 px (typically 10x16).
diff --git a/zephcore/helpers/ui/ui_mesh_actions.h b/zephcore/helpers/ui/ui_mesh_actions.h
index fa3ba14..f855b18 100644
--- a/zephcore/helpers/ui/ui_mesh_actions.h
+++ b/zephcore/helpers/ui/ui_mesh_actions.h
@@ -14,6 +14,8 @@
 #include <stdbool.h>
 #include <stdint.h>
 
+struct k_event;
+
 #ifdef __cplusplus
 extern "C" {
 #endif
diff --git a/zephcore/sysbuild/mcuboot.conf b/zephcore/sysbuild/mcuboot.conf
index 7c39c16..b5e39e5 100644
--- a/zephcore/sysbuild/mcuboot.conf
+++ b/zephcore/sysbuild/mcuboot.conf
@@ -33,8 +33,3 @@ CONFIG_POWER_DOMAIN=n
 # auto-propagation logic in sysbuild/CMakeLists.txt which appends
 # mcuboot_flashsize_<n>mb.conf when the app's board.conf sets a larger size.
 CONFIG_ESPTOOLPY_FLASHSIZE_4MB=y
-
-# ESP32 HAL's mcuboot_config.h is patched (patches/modules/hal/espressif/...)
-# to respect Zephyr Kconfig: mbedTLS detection, AUTO sector count, slot0 validation.
-CONFIG_BOOT_RSA_PSA=y
-CONFIG_BOOT_RSA_TF_PSA_CRYPTO_LEGACY=n