diff --git a/frontend/src/modals/bellcloud/devices/EditBellOutputsModal.jsx b/frontend/src/modals/bellcloud/devices/EditBellOutputsModal.jsx
index 6a73038..f8ea12a 100644
--- a/frontend/src/modals/bellcloud/devices/EditBellOutputsModal.jsx
+++ b/frontend/src/modals/bellcloud/devices/EditBellOutputsModal.jsx
@@ -51,11 +51,19 @@ export default function EditBellOutputsModal({ open, onClose, onSaved, attr, sub
       // Push to the device first — relay.set_config takes both maps in one call.
       // Only write to Firestore once the device confirms it actually applied
       // and persisted the change (sendMqttCommand's toast reports the outcome).
+      //
+      // relay.set_config is a partial update — any bell index NOT present in
+      // these maps is left untouched by the firmware. So every slot beyond
+      // activeBells must be sent explicitly as output 0 (disabled), or a bell
+      // that was previously active stays wired to its old output forever,
+      // even though it's no longer shown as active here. The only way to
+      // deactivate a bell today is to select it and set it to Disabled — this
+      // makes "deselect it" do the same thing implicitly.
       const durations = {}
       const outputs = {}
-      activeRows.forEach((r, i) => {
+      rows.forEach((r, i) => {
         durations[i] = r.timing
-        outputs[i] = r.output
+        outputs[i] = i < activeBells ? r.output : 0
       })
       await sendMqttCommand('relay.set_config', { durations, outputs })
 
diff --git a/frontend/src/pages/bellcloud/devices/OnboardDevice.jsx b/frontend/src/pages/bellcloud/devices/OnboardDevice.jsx
index dc71877..b3fb292 100644
--- a/frontend/src/pages/bellcloud/devices/OnboardDevice.jsx
+++ b/frontend/src/pages/bellcloud/devices/OnboardDevice.jsx
@@ -1275,9 +1275,13 @@ function ConfigureStep({ device, onDeviceUpdated, onNext, onBack }) {
   // ── Build the command sequence + Firestore patch for each group ─────────
   const buildGroups = useCallback(() => {
     const activeBellRows = bell.rows.slice(0, bell.activeBells)
+    // relay.set_config is a partial update — any bell index NOT present in
+    // these maps is left untouched by the firmware. Send every row (not just
+    // the active ones) so anything beyond activeBells is explicitly zeroed —
+    // same fix as EditBellOutputsModal.
     const durations = {}
     const outputs = {}
-    activeBellRows.forEach((r, i) => { durations[i] = r.timing; outputs[i] = r.output })
+    bell.rows.forEach((r, i) => { durations[i] = r.timing; outputs[i] = i < bell.activeBells ? r.output : 0 })
 
     return [
       {