Multi-ack. Closes #81.

frontend/src/components/settings/SettingsRadioSection.tsx

@@ -5,6 +5,7 @@ import { Label } from '../ui/label';
 import { Button } from '../ui/button';
 import { Separator } from '../ui/separator';
 import { toast } from '../ui/sonner';
+import { Checkbox } from '../ui/checkbox';
 import { RADIO_PRESETS } from '../../utils/radioPresets';
 import { stripRegionScopePrefix } from '../../utils/regionScope';
 import type {
@@ -64,6 +65,7 @@ export function SettingsRadioSection({
   const [cr, setCr] = useState('');
   const [pathHashMode, setPathHashMode] = useState('0');
   const [advertLocationSource, setAdvertLocationSource] = useState<'off' | 'current'>('current');
+  const [multiAcksEnabled, setMultiAcksEnabled] = useState(false);
   const [gettingLocation, setGettingLocation] = useState(false);
   const [busy, setBusy] = useState(false);
   const [rebooting, setRebooting] = useState(false);
@@ -98,6 +100,7 @@ export function SettingsRadioSection({
     setCr(String(config.radio.cr));
     setPathHashMode(String(config.path_hash_mode));
     setAdvertLocationSource(config.advert_location_source ?? 'current');
+    setMultiAcksEnabled(config.multi_acks_enabled ?? false);
   }, [config]);
 
   useEffect(() => {
@@ -190,6 +193,9 @@ export function SettingsRadioSection({
       ...(advertLocationSource !== (config.advert_location_source ?? 'current')
         ? { advert_location_source: advertLocationSource }
         : {}),
+      ...(multiAcksEnabled !== (config.multi_acks_enabled ?? false)
+        ? { multi_acks_enabled: multiAcksEnabled }
+        : {}),
       radio: {
         freq: parsedFreq,
         bw: parsedBw,
@@ -579,6 +585,24 @@ export function SettingsRadioSection({
             library.
           </p>
         </div>
+        <div className="space-y-2">
+          <div className="flex items-start gap-3 rounded-md border border-border/60 p-3">
+            <Checkbox
+              id="multi-acks-enabled"
+              checked={multiAcksEnabled}
+              onCheckedChange={(checked) => setMultiAcksEnabled(checked === true)}
+              className="mt-0.5"
+            />
+            <div className="space-y-1">
+              <Label htmlFor="multi-acks-enabled">Extra Direct ACK Transmission</Label>
+              <p className="text-xs text-muted-foreground">
+                When enabled, the radio sends one extra direct ACK transmission before the normal
+                ACK for received direct messages. This is a firmware-level receive behavior, not a
+                RemoteTerm retry setting.
+              </p>
+            </div>
+          </div>
+        </div>
       </div>
 
       {config.path_hash_mode_supported && (

frontend/src/test/settingsModal.test.tsx

@@ -37,6 +37,7 @@ const baseConfig: RadioConfig = {
   path_hash_mode: 0,
   path_hash_mode_supported: false,
   advert_location_source: 'current',
+  multi_acks_enabled: false,
 };
 
 const baseHealth: HealthStatus = {
@@ -332,6 +333,18 @@ describe('SettingsModal', () => {
     });
   });
 
+  it('saves multi-acks through radio config save', async () => {
+    const { onSave } = renderModal();
+    openRadioSection();
+
+    fireEvent.click(screen.getByLabelText('Extra Direct ACK Transmission'));
+    fireEvent.click(screen.getByRole('button', { name: 'Save' }));
+
+    await waitFor(() => {
+      expect(onSave).toHaveBeenCalledWith(expect.objectContaining({ multi_acks_enabled: true }));
+    });
+  });
+
   it('saves changed max contacts value through onSaveAppSettings', async () => {
     const { onSaveAppSettings } = renderModal();
     openRadioSection();

frontend/src/types.ts

@@ -16,6 +16,7 @@ export interface RadioConfig {
   path_hash_mode: number;
   path_hash_mode_supported: boolean;
   advert_location_source?: 'off' | 'current';
+  multi_acks_enabled?: boolean;
 }
 
 export interface RadioConfigUpdate {
@@ -26,6 +27,7 @@ export interface RadioConfigUpdate {
   radio?: RadioSettings;
   path_hash_mode?: number;
   advert_location_source?: 'off' | 'current';
+  multi_acks_enabled?: boolean;
 }
 
 export type RadioDiscoveryTarget = 'repeaters' | 'sensors' | 'all';