Add experimental double send

frontend/src/components/SettingsModal.tsx

@@ -92,6 +92,7 @@ export function SettingsModal({
   const [cr, setCr] = useState('');
   const [privateKey, setPrivateKey] = useState('');
   const [maxRadioContacts, setMaxRadioContacts] = useState('');
+  const [experimentalChannelDoubleSend, setExperimentalChannelDoubleSend] = useState(false);
 
   // Loading states
   const [loading, setLoading] = useState(false);
@@ -161,6 +162,7 @@ export function SettingsModal({
   useEffect(() => {
     if (appSettings) {
       setMaxRadioContacts(String(appSettings.max_radio_contacts));
+      setExperimentalChannelDoubleSend(appSettings.experimental_channel_double_send);
       setAutoDecryptOnAdvert(appSettings.auto_decrypt_dm_on_advert);
       setAdvertInterval(String(appSettings.advert_interval));
       setBots(appSettings.bots || []);
@@ -290,9 +292,16 @@ export function SettingsModal({
     setLoading(true);
 
     try {
+      const update: AppSettingsUpdate = {};
       const newMaxRadioContacts = parseInt(maxRadioContacts, 10);
       if (!isNaN(newMaxRadioContacts) && newMaxRadioContacts !== appSettings?.max_radio_contacts) {
-        await onSaveAppSettings({ max_radio_contacts: newMaxRadioContacts });
+        update.max_radio_contacts = newMaxRadioContacts;
+      }
+      if (experimentalChannelDoubleSend !== appSettings?.experimental_channel_double_send) {
+        update.experimental_channel_double_send = experimentalChannelDoubleSend;
+      }
+      if (Object.keys(update).length > 0) {
+        await onSaveAppSettings(update);
       }
       toast.success('Connectivity settings saved');
     } catch (err) {
@@ -756,6 +765,27 @@ export function SettingsModal({
                 </p>
               </div>
 
+              <div className="p-3 bg-yellow-500/10 border border-yellow-500/30 rounded-md space-y-3">
+                <p className="text-sm text-yellow-500">
+                  <strong>Experimental:</strong> Adds a duplicate channel send after a 3-second
+                  delay, using the exact same timestamp bytes.
+                </p>
+                <label className="flex items-center gap-3 cursor-pointer">
+                  <input
+                    type="checkbox"
+                    checked={experimentalChannelDoubleSend}
+                    onChange={(e) => setExperimentalChannelDoubleSend(e.target.checked)}
+                    className="w-4 h-4 rounded border-input accent-primary"
+                  />
+                  <span className="text-sm">Always send channel messages twice</span>
+                </label>
+                <p className="text-xs text-muted-foreground">
+                  This increases channel airtime and adds a 3-second second-attempt delay. Most
+                  clients deduplicate repeats by payload and timestamp, but behavior can vary by
+                  firmware/client.
+                </p>
+              </div>
+
               <Button onClick={handleSaveConnectivity} disabled={loading} className="w-full">
                 {loading ? 'Saving...' : 'Save Settings'}
               </Button>

frontend/src/test/appFavorites.test.tsx

@@ -162,6 +162,7 @@ const baseConfig = {
 
 const baseSettings = {
   max_radio_contacts: 200,
+  experimental_channel_double_send: false,
   favorites: [] as Array<{ type: 'channel' | 'contact'; id: string }>,
   auto_decrypt_dm_on_advert: false,
   sidebar_sort_order: 'recent' as const,

frontend/src/test/settingsModal.test.tsx

@@ -2,7 +2,7 @@ import { fireEvent, render, screen, waitFor } from '@testing-library/react';
 import { describe, expect, it, vi } from 'vitest';
 
 import { SettingsModal } from '../components/SettingsModal';
-import type { AppSettings, HealthStatus, RadioConfig } from '../types';
+import type { AppSettings, AppSettingsUpdate, HealthStatus, RadioConfig } from '../types';
 
 const baseConfig: RadioConfig = {
   public_key: 'aa'.repeat(32),
@@ -29,6 +29,7 @@ const baseHealth: HealthStatus = {
 
 const baseSettings: AppSettings = {
   max_radio_contacts: 200,
+  experimental_channel_double_send: false,
   favorites: [],
   auto_decrypt_dm_on_advert: false,
   sidebar_sort_order: 'recent',
@@ -40,7 +41,7 @@ const baseSettings: AppSettings = {
 
 function renderModal(overrides?: {
   appSettings?: AppSettings;
-  onSaveAppSettings?: (update: { max_radio_contacts?: number }) => Promise<void>;
+  onSaveAppSettings?: (update: AppSettingsUpdate) => Promise<void>;
   onRefreshAppSettings?: () => Promise<void>;
 }) {
   const onSaveAppSettings = overrides?.onSaveAppSettings ?? vi.fn(async () => {});
@@ -120,4 +121,22 @@ describe('SettingsModal', () => {
       expect(onSaveAppSettings).not.toHaveBeenCalled();
     });
   });
+
+  it('saves experimental channel double-send toggle through onSaveAppSettings', async () => {
+    const { onSaveAppSettings } = renderModal({
+      appSettings: { ...baseSettings, experimental_channel_double_send: false },
+    });
+
+    openConnectivityTab();
+
+    const toggle = screen.getByLabelText('Always send channel messages twice');
+    fireEvent.click(toggle);
+    fireEvent.click(screen.getByRole('button', { name: 'Save Settings' }));
+
+    await waitFor(() => {
+      expect(onSaveAppSettings).toHaveBeenCalledWith({
+        experimental_channel_double_send: true,
+      });
+    });
+  });
 });

frontend/src/types.ts

@@ -124,6 +124,7 @@ export interface BotConfig {
 
 export interface AppSettings {
   max_radio_contacts: number;
+  experimental_channel_double_send: boolean;
   favorites: Favorite[];
   auto_decrypt_dm_on_advert: boolean;
   sidebar_sort_order: 'recent' | 'alpha';
@@ -135,6 +136,7 @@ export interface AppSettings {
 
 export interface AppSettingsUpdate {
   max_radio_contacts?: number;
+  experimental_channel_double_send?: boolean;
   auto_decrypt_dm_on_advert?: boolean;
   sidebar_sort_order?: 'recent' | 'alpha';
   advert_interval?: number;