diff --git a/.gitignore b/.gitignore
index cd98f23..359f911 100644
--- a/.gitignore
+++ b/.gitignore
@@ -106,3 +106,4 @@ CRYPTO_AUDIT_INDEX.md
 AUDIT_MASTER_PLAN.md
 usb_companion_probe.py
 CORE_MESH_AUDIT_INDEX.md
+UPLINK_AUDIT_INDEX.md
diff --git a/zephcore/app/RepeaterMesh.cpp b/zephcore/app/RepeaterMesh.cpp
index bb0aefd..60aa6a0 100644
--- a/zephcore/app/RepeaterMesh.cpp
+++ b/zephcore/app/RepeaterMesh.cpp
@@ -935,6 +935,7 @@ RepeaterMesh::RepeaterMesh(mesh::MainBoard& board, mesh::Radio& radio, mesh::Mil
     _uplink_last_rssi = 0.0f;
     _uplink_last_raw_len = 0;
     _uplink_next_status_at = 0;
+    atomic_set(&_uplink_connect_pending, 0);
 #endif
 }
 
@@ -992,8 +993,12 @@ void RepeaterMesh::begin(RepeaterDataStore* store) {
         mqtt_publisher_start(&_uplink_creds, _prefs.node_name,
                              _uplink_status_topic, _uplink_packets_topic);
         mqtt_publisher_set_connect_cb([]() {
+            /* Runs on the MQTT publisher thread — DON'T publish here. It would
+             * race the main-thread status path on the shared static JSON buffer
+             * and toggle the battery-ADC regulator off-main. Defer to the main
+             * loop via an atomic flag drained in maintenanceLoop(). */
             if (s_uplink_mesh) {
-                s_uplink_mesh->publishUplinkStatus("online");
+                atomic_set(&s_uplink_mesh->_uplink_connect_pending, 1);
             }
         });
         _uplink_next_status_at = futureMillis(300000);
@@ -1346,6 +1351,11 @@ void RepeaterMesh::loop() {
     }
 
 #if IS_ENABLED(CONFIG_ZEPHCORE_REPEATER_UPLINK) && IS_ENABLED(CONFIG_MQTT_LIB)
+    /* MQTT (re)connected — publish the initial "online" status here on the main
+     * thread (the CONNACK callback only sets this flag, off-main). */
+    if (atomic_cas(&_uplink_connect_pending, 1, 0)) {
+        publishUplinkStatus("online");
+    }
     if (_uplink_next_status_at && millisHasNowPassed(_uplink_next_status_at)) {
         publishUplinkStatus("online");
         _uplink_next_status_at = futureMillis(300000);
diff --git a/zephcore/app/RepeaterMesh.h b/zephcore/app/RepeaterMesh.h
index 77cc925..20a22cf 100644
--- a/zephcore/app/RepeaterMesh.h
+++ b/zephcore/app/RepeaterMesh.h
@@ -12,6 +12,7 @@
 
 #pragma once
 
+#include <zephyr/sys/atomic.h>
 #include <mesh/Mesh.h>
 #include <mesh/StaticPoolPacketManager.h>
 #include <mesh/SimpleMeshTables.h>
@@ -122,6 +123,11 @@ class RepeaterMesh : public mesh::Mesh, public CommonCLICallbacks {
     uint8_t _uplink_last_raw[MAX_TRANS_UNIT];
     int _uplink_last_raw_len;
     unsigned long _uplink_next_status_at;
+    /* Set by the MQTT CONNACK callback (runs on the MQTT publisher thread);
+     * drained on the main thread in maintenanceLoop() so the "online" status
+     * publish never runs off-main (avoids the shared static-JSON-buffer race
+     * and off-main battery-ADC regulator toggling). */
+    atomic_t _uplink_connect_pending;
 #endif
 
     void putNeighbour(const mesh::Identity& id, uint32_t timestamp, float snr);
diff --git a/zephcore/app/main_observer.cpp b/zephcore/app/main_observer.cpp
index 3fac239..c51d096 100644
--- a/zephcore/app/main_observer.cpp
+++ b/zephcore/app/main_observer.cpp
@@ -49,10 +49,11 @@ static const struct gpio_dt_spec led0 = GPIO_DT_SPEC_GET(LED0_NODE, gpios);
 
 /* ========== Event loop bits ========== */
 
-#define MESH_EVENT_LORA_RX   BIT(0)
-#define MESH_EVENT_CLI_RX    BIT(1)
-#define MESH_EVENT_STATUS    BIT(2)
-#define MESH_EVENT_ALL       (MESH_EVENT_LORA_RX | MESH_EVENT_CLI_RX | MESH_EVENT_STATUS)
+#define MESH_EVENT_LORA_RX     BIT(0)
+#define MESH_EVENT_CLI_RX      BIT(1)
+#define MESH_EVENT_STATUS      BIT(2)
+#define MESH_EVENT_MQTT_CONNECT BIT(3)  /* MQTT (re)connected — publish status+self-advert on main */
+#define MESH_EVENT_ALL       (MESH_EVENT_LORA_RX | MESH_EVENT_CLI_RX | MESH_EVENT_STATUS | MESH_EVENT_MQTT_CONNECT)
 
 static struct k_event mesh_events;
 
@@ -343,10 +344,10 @@ int main(void)
 	/* Publish self-advert once on each MQTT connect so CoreScope can pin
 	 * this observer on the map (requires lat/lon to be configured). */
 	mqtt_publisher_set_connect_cb([]() {
-		if (s_mesh_ptr) {
-			s_mesh_ptr->publishStatus("online");
-			s_mesh_ptr->publishSelfAdvert();
-		}
+		/* Runs on the MQTT publisher thread — defer to the main loop. Publishing
+		 * here would race the periodic-status path on publishStatus()'s shared
+		 * static JSON buffer; publishSelfAdvert() also signs + formats. */
+		k_event_post(&mesh_events, MESH_EVENT_MQTT_CONNECT);
 	});
 	k_timer_start(&status_timer, K_SECONDS(300), K_SECONDS(300));
 
@@ -368,6 +369,10 @@ int main(void)
 		if (ev & MESH_EVENT_STATUS) {
 			observer_mesh.publishStatus("online");
 		}
+		if (ev & MESH_EVENT_MQTT_CONNECT) {
+			observer_mesh.publishStatus("online");
+			observer_mesh.publishSelfAdvert();
+		}
 	}
 
 	return 0;