feat(mobile): choose the dictation language for voice input

apps/mobile/src/features/settings/SettingsMicrophoneRouteScreen.tsx

@@ -10,6 +10,7 @@ import { useSafeAreaInsets } from "react-native-safe-area-context";
 import { type AppSymbolName } from "../../components/ui/AppSymbol";
 import { AppText as Text } from "../../components/ui/AppText";
 import { cn } from "../../lib/cn";
+import { DICTATION_LANGUAGES } from "../../lib/dictationLanguage";
 import { makePermissionStatusAtom } from "../../lib/permissionStatusAtom";
 import {
   isMicrophoneDevice,
@@ -22,6 +23,7 @@ import { mobilePreferencesAtom, updateMobilePreferencesAtom } from "../../state/
 import { ListRowLayout } from "../../components/ui/ListRowLayout";
 import { ThreadSwipeable } from "../home/thread-swipe-actions";
 import { ListActionRow as SettingsActionRow } from "../../components/ui/ListActionRow";
+import { ListChoiceRow as SettingsChoiceRow } from "../../components/ui/ListChoiceRow";
 import { SettingsDragHandle } from "./components/SettingsDragHandle";
 import { SettingsSection } from "./components/SettingsSection";
 
@@ -96,6 +98,9 @@ export function SettingsMicrophoneRouteScreen() {
   const entries = microphoneOrder(
     AsyncResult.isSuccess(preferencesResult) ? preferencesResult.value.microphones : undefined,
   );
+  const dictationLocale = AsyncResult.isSuccess(preferencesResult)
+    ? (preferencesResult.value.dictationLocale ?? null)
+    : null;
   const { permission, request: requestPermission } = useMicrophonePermission();
   const [drag, setDrag] = useState<{ readonly key: string; readonly translation: number } | null>(
     null,
@@ -201,6 +206,27 @@ export function SettingsMicrophoneRouteScreen() {
           devices are added by name after you use voice input with them connected; until then, the
           Other row ranks them. Swipe a device left to forget it.
         </Text>
+        <SettingsSection title="Dictation language">
+          <SettingsChoiceRow
+            label="Device language"
+            selected={ready && dictationLocale === null}
+            disabled={!ready}
+            onPress={() => savePreferences({ dictationLocale: null })}
+          />
+          {DICTATION_LANGUAGES.map((language) => (
+            <SettingsChoiceRow
+              key={language.locale}
+              label={language.label}
+              selected={dictationLocale === language.locale}
+              separated
+              disabled={!ready}
+              onPress={() => savePreferences({ dictationLocale: language.locale })}
+            />
+          ))}
+        </SettingsSection>
+        <Text className="px-2 text-sm text-foreground-muted">
+          Voice input transcribes on this device. The first use of a language downloads it.
+        </Text>
       </ScrollView>
     </View>
   );

apps/mobile/src/features/settings/settings-search.ts

@@ -29,7 +29,7 @@ const SETTINGS_SEARCH_TERMS = {
   ],
   SettingsNavigation: ["tabs", "tab order", "reorder", "hide tabs"],
   SettingsKeyboard: ["return key", "send message", "new line", "hardware keyboard"],
-  SettingsMicrophone: ["voice", "dictation", "audio input", "bluetooth"],
+  SettingsMicrophone: ["voice", "dictation", "audio input", "bluetooth", "language"],
   SettingsScheduledTasks: ["automations", "schedule", "cron", "recurring", "webhook"],
   SettingsProjectOverview: ["project", "overview", "checkouts", "delete project"],
   SettingsOrganization: [

apps/mobile/src/features/voice-input/VoiceInputProvider.tsx

@@ -91,7 +91,14 @@ const voiceInputAtom = Atom.make((get) => {
   });
   const session: VoiceInputSession = new VoiceInputSession({
     recorder,
-    getTranscriber: getLocalVoiceTranscriber,
+    getTranscriber: () => {
+      const preferences = registry.get(mobilePreferencesAtom);
+      return getLocalVoiceTranscriber(
+        AsyncResult.isSuccess(preferences)
+          ? (preferences.value.dictationLocale ?? undefined)
+          : undefined,
+      );
+    },
     requestPermission: async () => {
       const permission = await requestRecordingPermissionsAsync();
       return { granted: permission.granted, canAskAgain: permission.canAskAgain };

apps/mobile/src/lib/dictationLanguage.ts

@@ -0,0 +1,32 @@
+/** Locales Apple's on-device SpeechTranscriber offers. Unset follows the device language. */
+export const DICTATION_LANGUAGES = [
+  { locale: "en-US", label: "English (US)" },
+  { locale: "en-GB", label: "English (UK)" },
+  { locale: "en-AU", label: "English (Australia)" },
+  { locale: "en-CA", label: "English (Canada)" },
+  { locale: "en-IN", label: "English (India)" },
+  { locale: "pt-BR", label: "Português (Brasil)" },
+  { locale: "pt-PT", label: "Português (Portugal)" },
+  { locale: "es-ES", label: "Español (España)" },
+  { locale: "es-MX", label: "Español (México)" },
+  { locale: "es-US", label: "Español (EE. UU.)" },
+  { locale: "fr-FR", label: "Français (France)" },
+  { locale: "fr-CA", label: "Français (Canada)" },
+  { locale: "de-DE", label: "Deutsch" },
+  { locale: "it-IT", label: "Italiano" },
+  { locale: "ja-JP", label: "日本語" },
+  { locale: "ko-KR", label: "한국어" },
+  { locale: "zh-CN", label: "中文（普通话）" },
+  { locale: "zh-TW", label: "中文（台灣）" },
+  { locale: "yue-CN", label: "粵語" },
+] as const;
+
+export type DictationLocale = (typeof DICTATION_LANGUAGES)[number]["locale"];
+
+const DICTATION_LOCALES: ReadonlySet<string> = new Set(
+  DICTATION_LANGUAGES.map((language) => language.locale),
+);
+
+export function isDictationLocale(value: unknown): value is DictationLocale {
+  return typeof value === "string" && DICTATION_LOCALES.has(value);
+}

apps/mobile/src/native/voiceTranscription.ios.test.ts

@@ -79,4 +79,16 @@ describe("getLocalVoiceTranscriber", () => {
     expect(error).toMatchObject({ code: "cancelled" });
     expect(mocks.transcribe).not.toHaveBeenCalled();
   });
+
+  it("prepares and transcribes the preferred locale instead of the device locale", async () => {
+    mocks.prepare.mockResolvedValue("pt-BR");
+    const options = { signal: new AbortController().signal };
+    const prepared = await getLocalVoiceTranscriber("pt-BR")!.prepare(options);
+    await prepared.transcribe("file:///voice.m4a", options);
+
+    expect(mocks.isAvailable).toHaveBeenCalledWith("pt-BR");
+    expect(mocks.prepare).toHaveBeenCalledWith("pt-BR");
+    expect(mocks.transcribe).toHaveBeenCalledWith(audio, "pt-BR");
+    expect(prepared.locale).toBe("pt-BR");
+  });
 });

apps/mobile/src/native/voiceTranscription.ios.ts

@@ -33,8 +33,8 @@ function getNativeErrorCode(error: unknown): string | undefined {
   return typeof error.code === "string" ? error.code : undefined;
 }
 
-export function getLocalVoiceTranscriber(): VoiceTranscriber | null {
-  const locale = getDeviceLocale();
+export function getLocalVoiceTranscriber(preferredLocale?: string): VoiceTranscriber | null {
+  const locale = preferredLocale ?? getDeviceLocale();
   if (!AppleTranscription.isAvailable(locale)) return null;
   return { prepare: (options) => prepareVoiceTranscription(locale, options) };
 }
@@ -63,7 +63,7 @@ async function prepareVoiceTranscription(
     if (getNativeErrorCode(error) === "AppleTranscriptionUnsupportedLocale") {
       throw new VoiceTranscriptionError(
         "unsupported-locale",
-        "Voice transcription does not support this device language.",
+        "Voice transcription does not support this language.",
         { cause: error },
       );
     }

apps/mobile/src/native/voiceTranscription.ts

@@ -1,5 +1,5 @@
 import type { VoiceTranscriber } from "@t3tools/client-runtime/voice-input";
 
-export function getLocalVoiceTranscriber(): VoiceTranscriber | null {
+export function getLocalVoiceTranscriber(_preferredLocale?: string): VoiceTranscriber | null {
   return null;
 }

apps/mobile/src/persistence/mobile-preferences.ts

@@ -16,6 +16,7 @@ import {
 } from "@t3tools/contracts";
 import type { AndroidNavigationStyle } from "../lib/androidNavigationStyle";
 import type { ComposerEnterBehavior } from "../lib/composerEnterBehavior";
+import { isDictationLocale, type DictationLocale } from "../lib/dictationLanguage";
 import type { FollowUpBehavior } from "../lib/followUpBehavior";
 import { isMicrophoneKind, type MicrophoneEntry } from "../lib/microphonePriority";
 import { MOBILE_THEME_IDS, type MobileThemeId, type MobileThemeMode } from "../lib/mobileTheme";
@@ -112,6 +113,8 @@ export interface Preferences {
   readonly composerEnterBehavior?: ComposerEnterBehavior;
   readonly followUpBehavior?: FollowUpBehavior;
   readonly microphones?: ReadonlyArray<MicrophoneEntry>;
+  /** Unset or null means dictation follows the device language. */
+  readonly dictationLocale?: DictationLocale | null;
   readonly projectGroupingEnabled?: boolean;
   readonly projectGroupingMode?: SidebarProjectGroupingMode;
   readonly planModeEnabled?: boolean;
@@ -192,6 +195,7 @@ function sanitizePreferences(parsed: Preferences): Preferences {
     composerEnterBehavior?: ComposerEnterBehavior;
     followUpBehavior?: FollowUpBehavior;
     microphones?: ReadonlyArray<MicrophoneEntry>;
+    dictationLocale?: DictationLocale | null;
     projectGroupingEnabled?: boolean;
     projectGroupingMode?: SidebarProjectGroupingMode;
     planModeEnabled?: boolean;
@@ -308,6 +312,9 @@ function sanitizePreferences(parsed: Preferences): Preferences {
         : [];
     });
   }
+  if (parsed.dictationLocale === null || isDictationLocale(parsed.dictationLocale)) {
+    preferences.dictationLocale = parsed.dictationLocale;
+  }
   if (typeof parsed.projectGroupingEnabled === "boolean") {
     preferences.projectGroupingEnabled = parsed.projectGroupingEnabled;
   }

docs/user/composer.md

@@ -193,6 +193,9 @@ for example, put **Other Bluetooth** above your AirPods so a new headset is pref
 while the AirPods microphone stays low. By default, CarPlay comes after the built-in
 microphone. Swipe a device left to forget it.
 
+Voice input transcribes in your iPhone's language. To dictate in another language,
+such as Brazilian Portuguese, pick it under **Settings → Microphone → Dictation language**.
+
 Transcription runs on your device. T3 Code deletes the temporary audio after
 transcription or cancellation; only the message text is sent when you submit.