diff --git a/zephcore/app/RepeaterMesh.cpp b/zephcore/app/RepeaterMesh.cpp
index 3fec911..38cf245 100644
--- a/zephcore/app/RepeaterMesh.cpp
+++ b/zephcore/app/RepeaterMesh.cpp
@@ -235,35 +235,36 @@ int RepeaterMesh::handleRequest(ClientInfo* sender, uint32_t sender_timestamp, u
         /* CayenneLPP telemetry response using SimpleLPP encoder */
         SimpleLPP lpp(&reply_data[4], sizeof(reply_data) - 4);
 
-        /* Battery voltage - channel 0 = self */
+        /* Battery voltage — channel 1 = TELEM_CHANNEL_SELF (matches Arduino) */
+        const uint8_t CH_SELF = 1;
         uint16_t batt_mv = _board.getBattMilliVolts();
-        lpp.addVoltage(0, batt_mv / 1000.0f);
+        lpp.addVoltage(CH_SELF, batt_mv / 1000.0f);
 
         /* Environment sensors — prefer external, fallback to MCU die temp */
         struct env_data env;
         if (env_sensors_read(&env) == 0) {
             if (env.has_temperature) {
-                lpp.addTemperature(0, env.temperature_c);
+                lpp.addTemperature(CH_SELF, env.temperature_c);
             } else if (env.has_mcu_temperature) {
-                lpp.addTemperature(0, env.mcu_temperature_c);
+                lpp.addTemperature(CH_SELF, env.mcu_temperature_c);
             } else {
                 /* Last resort: MCU temp from board API */
                 float mcu_temp = _board.getMCUTemperature();
                 if (!isnan(mcu_temp)) {
-                    lpp.addTemperature(0, mcu_temp);
+                    lpp.addTemperature(CH_SELF, mcu_temp);
                 }
             }
             if (env.has_humidity) {
-                lpp.addRelativeHumidity(0, env.humidity_pct);
+                lpp.addRelativeHumidity(CH_SELF, env.humidity_pct);
             }
             if (env.has_pressure) {
-                lpp.addBarometricPressure(0, env.pressure_hpa);
+                lpp.addBarometricPressure(CH_SELF, env.pressure_hpa);
             }
         } else {
             /* No env sensors at all — try MCU temp directly */
             float mcu_temp = _board.getMCUTemperature();
             if (!isnan(mcu_temp)) {
-                lpp.addTemperature(0, mcu_temp);
+                lpp.addTemperature(CH_SELF, mcu_temp);
             }
         }
 
@@ -271,7 +272,7 @@ int RepeaterMesh::handleRequest(ClientInfo* sender, uint32_t sender_timestamp, u
         if (power_sensors_available()) {
             struct power_data pwr;
             if (power_sensors_read(&pwr) == 0) {
-                uint8_t ch = 1;
+                uint8_t ch = CH_SELF + 1;
                 for (int j = 0; j < pwr.num_channels; j++) {
                     if (pwr.channels[j].valid) {
                         lpp.addVoltage(ch, pwr.channels[j].voltage_v);
diff --git a/zephcore/boards/common/healthcheck.conf b/zephcore/boards/common/healthcheck.conf
new file mode 100644
index 0000000..58323e9
--- /dev/null
+++ b/zephcore/boards/common/healthcheck.conf
@@ -0,0 +1,47 @@
+# Health Check overlay — verbose logging for diagnosing repeater issues
+# Build: west build -b rak3401_1watt zephcore --pristine -- \
+#   -DEXTRA_CONF_FILE="boards/common/repeater.conf;boards/common/healthcheck.conf"
+#
+# Cranks all ZephCore log modules to INF (some to DBG where safe),
+# enables packet logging, and sizes buffers for the extra output.
+
+# ========== ZephCore module log levels ==========
+# Main mesh logic (Mesh, BaseChatMesh, RepeaterMesh, Utils, PowerController)
+CONFIG_ZEPHCORE_MAIN_LOG_LEVEL_DBG=y
+
+# LoRa radio layer (Dispatcher, SX126xRadio, LoRaRadioBase, PacketPool)
+CONFIG_ZEPHCORE_LORA_LOG_LEVEL_DBG=y
+
+# Data store, CLI, ACL, RegionMap
+CONFIG_ZEPHCORE_DATASTORE_LOG_LEVEL_DBG=y
+
+# Board adapter (GPIO, ADC, battery)
+CONFIG_ZEPHCORE_BOARD_LOG_LEVEL_DBG=y
+
+# GPS manager
+CONFIG_ZEPHCORE_GPS_LOG_LEVEL_DBG=y
+
+# Environment sensors
+CONFIG_ZEPHCORE_SENSORS_LOG_LEVEL_DBG=y
+
+# USB repeater adapter
+CONFIG_ZEPHCORE_USB_LOG_LEVEL_INF=y
+
+# ========== Packet logging ==========
+CONFIG_ZEPHCORE_PACKET_LOGGING=y
+
+# ========== Zephyr subsystem logs ==========
+# LoRa driver itself
+CONFIG_LORA_LOG_LEVEL_DBG=y
+
+# ========== Log infrastructure — sized for heavy output ==========
+CONFIG_LOG_BUFFER_SIZE=16384
+CONFIG_LOG_PROCESS_TRIGGER_THRESHOLD=1
+CONFIG_LOG_PROCESS_THREAD_STACK_SIZE=4096
+
+# Backends — UART (USB CDC) so you can read on a terminal
+CONFIG_LOG_BACKEND_UART=y
+CONFIG_LOG_BACKEND_RTT=y
+
+# Increase system workqueue stack to handle DBG-level log calls from ISR context
+CONFIG_SYSTEM_WORKQUEUE_STACK_SIZE=4096