diff --git a/AGENTS.md b/AGENTS.md
index 54eeab672a..6f41460d08 100644
--- a/AGENTS.md
+++ b/AGENTS.md
@@ -563,13 +563,22 @@ enforces that).
   from the picked language — for a guest that is the *only* source of direction,
   since the middleware renders `htmlDir` from the default on every request.
 - **Register submits `locale` as a required hidden field** and creates the user
-  with it. **Login submits it only once the visitor picks a language** — the
-  field goes out empty otherwise, and an empty value leaves `users.locale`
+  with it: the language the visitor picked, else the browser's language
+  (`detectBrowserLanguage` over the supported codes, so `pt-PT` becomes `pt-BR`),
+  else `Locale::DEFAULT` (`signupLocale` in `useGuestLocale`). The page still
+  renders in the default until the visitor picks; only the account gets the
+  browser language. Lifecycle emails pick their language from it, so a signup
+  must not start in English and switch minutes later.
+  **Login submits it only once the visitor picks a language** — the field goes
+  out empty otherwise, and an empty value leaves `users.locale`
   untouched. This asymmetry is load-bearing: the login screen always renders in
   `Locale::DEFAULT`, so an always-sent field would reset every non-English user
   to English on each login. Forgot and reset password do not send it at all.
-- Google and GitHub signups store `Locale::DEFAULT`: they have no picker, and the
-  OAuth callback tells you nothing reliable about the person.
+- Google and GitHub signups send the same `signupLocale` as a query param on the
+  start route, kept by `PreservesSignupPreferences` with the zone and clock (the
+  OAuth callback itself tells you nothing reliable about the person). `CreateUser`
+  falls back to `Locale::DEFAULT` for a missing or unsupported value. A returning
+  user logging in through OAuth keeps their stored locale.
 
 ## User preferences (`/settings/preferences`)
 
@@ -632,8 +641,9 @@ rolls the switch back and toasts.
   `WeekStart::firstDay()/lastDay()` to Carbon. The weekly posting goal
   (`CountPostsSentThisWeek`) and the Insights weekly buckets (`PeriodBuckets`)
   follow the **viewing** user's `week_starts_on`, never Monday or the UI language.
-- **Signup detection:** email, Google and GitHub signups store the browser zone,
-  the week start (`Intl.Locale` week info, else the Sunday-first zone list in
+- **Signup detection:** email, Google and GitHub signups store the browser
+  language (see "UI locale"), the browser zone, the week start (`Intl.Locale`
+  week info, else the Sunday-first zone list in
   `resources/js/lib/detectPreferences.ts`) and the hour cycle. OAuth sends them as
   query params on the start route and `PreservesSignupPreferences` keeps them in
   the session; `CreateUser` validates each one. Fallbacks: UTC, Monday, the
diff --git a/app/Actions/User/CreateUser.php b/app/Actions/User/CreateUser.php
index fd00cbb122..61e85fc0ed 100644
--- a/app/Actions/User/CreateUser.php
+++ b/app/Actions/User/CreateUser.php
@@ -22,7 +22,7 @@
 class CreateUser
 {
     /**
-     * @param  array{name: string, email: string, password?: string, google_id?: string, github_id?: string, email_verified_at?: \DateTimeInterface|null, is_invite?: bool, registration_ip?: string|null, locale?: string, timezone?: string|null, week_starts_on?: string|null, time_format?: string|null}  $data
+     * @param  array{name: string, email: string, password?: string, google_id?: string, github_id?: string, email_verified_at?: \DateTimeInterface|null, is_invite?: bool, registration_ip?: string|null, locale?: string|null, timezone?: string|null, week_starts_on?: string|null, time_format?: string|null}  $data
      * @param  array<string, string>  $attributionParameters  UTM parameters and ad click IDs (gclid, fbclid, etc.) captured before signup
      */
     public static function execute(array $data, array $attributionParameters = []): User
@@ -47,7 +47,7 @@ public static function execute(array $data, array $attributionParameters = []):
 
             $account = Account::query()->forceCreate($accountAttributes);
 
-            $locale = Locale::from(data_get($data, 'locale', Locale::DEFAULT->value));
+            $locale = Locale::tryFrom((string) data_get($data, 'locale')) ?? Locale::DEFAULT;
 
             $user = User::create(array_merge([
                 'name' => data_get($data, 'name'),
diff --git a/app/Http/Controllers/Auth/Concerns/PreservesSignupPreferences.php b/app/Http/Controllers/Auth/Concerns/PreservesSignupPreferences.php
index f1dfbaff79..5be065a92a 100644
--- a/app/Http/Controllers/Auth/Concerns/PreservesSignupPreferences.php
+++ b/app/Http/Controllers/Auth/Concerns/PreservesSignupPreferences.php
@@ -11,14 +11,14 @@ trait PreservesSignupPreferences
 {
     private function storeSignupPreferences(Request $request): void
     {
-        $request->session()->put('signup_preferences', collect($request->only(['timezone', 'week_starts_on', 'time_format']))
+        $request->session()->put('signup_preferences', collect($request->only(['locale', 'timezone', 'week_starts_on', 'time_format']))
             ->filter(fn (mixed $value): bool => is_string($value) && $value !== '')
             ->map(fn (string $value): string => Str::limit($value, 64, ''))
             ->all());
     }
 
     /**
-     * @return array{timezone?: string, week_starts_on?: string, time_format?: string}
+     * @return array{locale?: string, timezone?: string, week_starts_on?: string, time_format?: string}
      */
     private function retrieveSignupPreferences(): array
     {
diff --git a/app/Http/Controllers/Auth/GitHubController.php b/app/Http/Controllers/Auth/GitHubController.php
index d6a2a4b916..3810ae9722 100644
--- a/app/Http/Controllers/Auth/GitHubController.php
+++ b/app/Http/Controllers/Auth/GitHubController.php
@@ -124,6 +124,7 @@ private function registerNewUser(\Laravel\Socialite\Contracts\User $githubUser):
             'email_verified_at' => now(),
             'is_invite' => $invite !== null,
             'registration_ip' => request()->ip(),
+            'locale' => data_get($preferences, 'locale'),
             'timezone' => data_get($preferences, 'timezone'),
             'week_starts_on' => data_get($preferences, 'week_starts_on'),
             'time_format' => data_get($preferences, 'time_format'),
diff --git a/app/Http/Controllers/Auth/GoogleController.php b/app/Http/Controllers/Auth/GoogleController.php
index f231390a19..9c3b157533 100644
--- a/app/Http/Controllers/Auth/GoogleController.php
+++ b/app/Http/Controllers/Auth/GoogleController.php
@@ -116,6 +116,7 @@ private function registerNewUser(\Laravel\Socialite\Contracts\User $googleUser):
             'email_verified_at' => now(),
             'is_invite' => $invite !== null,
             'registration_ip' => request()->ip(),
+            'locale' => data_get($preferences, 'locale'),
             'timezone' => data_get($preferences, 'timezone'),
             'week_starts_on' => data_get($preferences, 'week_starts_on'),
             'time_format' => data_get($preferences, 'time_format'),
diff --git a/resources/js/components/auth/SocialLogin.vue b/resources/js/components/auth/SocialLogin.vue
index 80dfc266ae..76914dfa71 100644
--- a/resources/js/components/auth/SocialLogin.vue
+++ b/resources/js/components/auth/SocialLogin.vue
@@ -3,6 +3,7 @@ import { usePage } from '@inertiajs/vue3';
 import { computed } from 'vue';
 
 import { Button } from '@/components/ui/button';
+import { useGuestLocale } from '@/composables/useGuestLocale';
 import { detectPreferences } from '@/lib/detectPreferences';
 import { redirect as githubRedirect } from '@/routes/auth/github';
 import { redirect as googleRedirect } from '@/routes/auth/google';
@@ -22,9 +23,11 @@ const githubEnabled = computed(() => Boolean(page.props.githubAuthEnabled));
 const hasSocial = computed(() => googleEnabled.value || githubEnabled.value);
 
 const detected = detectPreferences();
+const { signupLocale } = useGuestLocale();
 
 const query = computed(() => {
     const params: Record<string, string> = {
+        locale: signupLocale.value,
         timezone: detected.timezone,
         week_starts_on: detected.week_starts_on,
     };
diff --git a/resources/js/composables/useGuestLocale.ts b/resources/js/composables/useGuestLocale.ts
index 7fa4f4f6c6..27db3dbe66 100644
--- a/resources/js/composables/useGuestLocale.ts
+++ b/resources/js/composables/useGuestLocale.ts
@@ -2,6 +2,7 @@ import { usePage } from '@inertiajs/vue3';
 import { computed } from 'vue';
 
 import { chooseGuestLocale, guestLocale } from '@/language';
+import { detectBrowserLanguage } from '@/lib/detectPreferences';
 import type { Language } from '@/types';
 
 export const useGuestLocale = () => {
@@ -11,8 +12,14 @@ export const useGuestLocale = () => {
         () => page.props.languages as Language[],
     );
 
+    const pageLocale = (): string => page.props.locale as string;
+
+    const browserLocale = computed(() =>
+        detectBrowserLanguage(languages.value.map((language) => language.code)),
+    );
+
     const locale = computed<string>({
-        get: () => guestLocale() ?? (page.props.locale as string),
+        get: () => guestLocale() ?? pageLocale(),
         set: (value) => {
             const language = languages.value.find(
                 (candidate) => candidate.code === value,
@@ -24,5 +31,9 @@ export const useGuestLocale = () => {
         },
     });
 
-    return { locale, chosen: computed(guestLocale), languages };
+    const signupLocale = computed(
+        () => guestLocale() ?? browserLocale.value ?? pageLocale(),
+    );
+
+    return { locale, signupLocale, chosen: computed(guestLocale), languages };
 };
diff --git a/resources/js/pages/auth/Register.vue b/resources/js/pages/auth/Register.vue
index 8ba59cc5c8..aa1751c3ec 100644
--- a/resources/js/pages/auth/Register.vue
+++ b/resources/js/pages/auth/Register.vue
@@ -31,7 +31,7 @@ defineProps<{
     passwordRequirements: PasswordRequirement[];
 }>();
 
-const { locale } = useGuestLocale();
+const { signupLocale } = useGuestLocale();
 const detected = detectPreferences();
 
 const showPassword = ref(false);
@@ -68,7 +68,7 @@ const hasSocial = computed(
                 class="flex flex-col gap-6"
             >
                 <input v-if="invite" type="hidden" name="invite" :value="invite" />
-                <input type="hidden" name="locale" :value="locale" />
+                <input type="hidden" name="locale" :value="signupLocale" data-testid="register-locale" />
                 <input type="hidden" name="timezone" :value="detected.timezone" data-testid="register-timezone" />
                 <input type="hidden" name="week_starts_on" :value="detected.week_starts_on" data-testid="register-week-start" />
                 <input type="hidden" name="time_format" :value="detected.time_format ?? ''" data-testid="register-time-format" />
@@ -163,7 +163,7 @@ const hasSocial = computed(
                             class="w-full"
                             :tabindex="4"
                             :disabled="processing"
-                            data-test="register-user-button"
+                            data-testid="register-user-button"
                         >
                             <Spinner v-if="processing" />
                             {{ $t('auth.register.submit') }}
diff --git a/tests/Browser/SignupPreferencesTest.php b/tests/Browser/SignupPreferencesTest.php
index ea9a39e1c2..42c931bcfe 100644
--- a/tests/Browser/SignupPreferencesTest.php
+++ b/tests/Browser/SignupPreferencesTest.php
@@ -2,33 +2,25 @@
 
 declare(strict_types=1);
 
-function waitForSignupPreferencesTestId(mixed $page, string $testId): void
-{
-    $page->script(<<<JS
-        (async () => {
-            for (let attempt = 0; attempt < 100; attempt++) {
-                if (document.querySelector('[data-testid="{$testId}"]')) return;
-                await new Promise((resolve) => setTimeout(resolve, 50));
-            }
-        })();
-    JS);
-}
-
-function signupPreferencesValue(mixed $page, string $testId): string
-{
-    return (string) $page->script("document.querySelector('[data-testid=\"{$testId}\"]').value");
-}
+use App\Enums\User\Locale;
+use App\Models\Account;
+use App\Models\Invite;
+use App\Models\User;
+use App\Models\Workspace;
+use Illuminate\Support\Uri;
+use Laravel\Socialite\Facades\Socialite;
+use Laravel\Socialite\Two\User as SocialiteUser;
 
 test('the register form sends the zone, week start and clock the browser reports', function (string $locale, string $timezone, string $weekStart, string $timeFormat) {
     config()->set('trypost.self_hosted', false);
 
     $page = visit(route('register'))->withLocale($locale)->withTimezone($timezone);
-    waitForSignupPreferencesTestId($page, 'register-time-format');
+    waitForState($page, '@register-time-format', "element.value !== ''");
 
-    expect(signupPreferencesValue($page, 'register-timezone'))->toBe($timezone)
-        ->and(signupPreferencesValue($page, 'register-week-start'))->toBe($weekStart)
-        ->and(signupPreferencesValue($page, 'register-time-format'))->toBe($timeFormat);
-    $page->assertNoJavaScriptErrors();
+    $page->assertValue('@register-timezone', $timezone)
+        ->assertValue('@register-week-start', $weekStart)
+        ->assertValue('@register-time-format', $timeFormat)
+        ->assertNoJavaScriptErrors();
 })->with([
     'United States' => ['en-US', 'America/New_York', 'sunday', '12h'],
     'Germany' => ['de-DE', 'Europe/Berlin', 'monday', '24h'],
@@ -39,13 +31,157 @@ function signupPreferencesValue(mixed $page, string $testId): string
     config()->set('trypost.github_auth_enabled', true);
 
     $page = visit(route('login'))->withLocale('en-US')->withTimezone('Asia/Tokyo');
-    waitForSignupPreferencesTestId($page, 'social-login-github');
+    waitFor($page, '@social-login-github');
+
+    foreach (['@social-login-google', '@social-login-github'] as $button) {
+        expect(Uri::of($page->attribute($button, 'href'))->query()->all())
+            ->toMatchArray(['locale' => 'en', 'timezone' => 'Asia/Tokyo', 'week_starts_on' => 'sunday', 'time_format' => '12h']);
+    }
+
+    $page->assertNoJavaScriptErrors();
+});
+
+test('the register form signs up in the browser language when the visitor picks none', function (string $browserLocale, string $expected) {
+    config()->set('trypost.self_hosted', false);
+
+    $page = visit(route('register'))->withLocale($browserLocale);
+    waitForState($page, '@register-locale', "element.value !== ''");
+
+    $page->assertValue('@register-locale', $expected)
+        ->assertNoJavaScriptErrors();
+})->with([
+    'Brazil' => ['pt-BR', 'pt-BR'],
+    'Portugal, same base language' => ['pt-PT', 'pt-BR'],
+    'Spain' => ['es-ES', 'es'],
+    'unsupported falls back to the default' => ['sv-SE', 'en'],
+]);
+
+test('the google and github buttons carry the browser language to the OAuth start', function () {
+    config()->set('trypost.self_hosted', false);
+    config()->set('trypost.google_auth_enabled', true);
+    config()->set('trypost.github_auth_enabled', true);
+
+    $page = visit(route('register'))->withLocale('es-ES');
+    waitFor($page, '@social-login-github');
+
+    foreach (['@social-login-google', '@social-login-github'] as $button) {
+        expect(Uri::of($page->attribute($button, 'href'))->query()->get('locale'))->toBe('es');
+    }
+
+    $page->assertNoJavaScriptErrors();
+});
+
+test('a language picked on the register page wins over the browser language', function () {
+    config()->set('trypost.self_hosted', false);
+    config()->set('trypost.google_auth_enabled', true);
+    config()->set('trypost.github_auth_enabled', true);
+
+    $page = visit(route('register'))->withLocale('es-ES');
+    waitFor($page, '@language-picker-trigger');
+
+    $page->click('@language-picker-trigger');
+    waitFor($page, '@language-picker-option-pt-BR');
+    $page->click('@language-picker-option-pt-BR');
+    waitForState($page, '@register-locale', "element.value === 'pt-BR'");
+
+    $page->assertValue('@register-locale', 'pt-BR');
+
+    foreach (['@social-login-google', '@social-login-github'] as $button) {
+        expect(Uri::of($page->attribute($button, 'href'))->query()->get('locale'))->toBe('pt-BR');
+    }
+
+    $page->assertNoJavaScriptErrors();
+});
+
+test('signing up with the email form creates the account in the browser language', function () {
+    config()->set('trypost.self_hosted', false);
+    fakePwnedPasswords();
+
+    $page = visit(route('register'))->withLocale('pt-BR');
+    waitForState($page, '@register-locale', "element.value !== ''");
+
+    $page->fill('@register-name', 'Bia')
+        ->fill('@register-email', 'bia-browser@example.com')
+        ->fill('@register-password', strongPassword())
+        ->click('@register-user-button');
+    waitForPath($page, parse_url(route('app.welcome.persona'), PHP_URL_PATH));
+
+    expect(User::query()->where('email', 'bia-browser@example.com')->sole()->locale)->toBe(Locale::PortugueseBrazil);
+    $page->assertNoJavaScriptErrors();
+});
+
+test('a new person who starts on the login page signs up with google or github in the browser language', function (string $network, string $driver) {
+    config()->set('trypost.self_hosted', false);
+    config()->set('trypost.google_auth_enabled', true);
+    config()->set('trypost.github_auth_enabled', true);
+
+    $page = visit(route('login'))->withLocale('es-ES');
+    waitFor($page, "@social-login-{$network}");
+    $href = $page->attribute("@social-login-{$network}", 'href');
+    $page->assertNoJavaScriptErrors();
+
+    $socialiteUser = new SocialiteUser;
+    $socialiteUser->id = "{$network}-from-login";
+    $socialiteUser->name = 'New Person';
+    $socialiteUser->email = "{$network}-from-login@example.com";
+    Socialite::shouldReceive('driver')->with($driver)->andReturn($socialite = Mockery::mock());
+    $socialite->shouldReceive('redirect')->andReturn(redirect('/'));
+    $socialite->shouldReceive('scopes')->andReturnSelf();
+    $socialite->shouldReceive('user')->andReturn($socialiteUser);
 
-    foreach (['social-login-google', 'social-login-github'] as $button) {
-        $params = $page->script("Object.fromEntries(new URL(document.querySelector('[data-testid=\"{$button}\"]').href).searchParams)");
+    $this->get($href);
+    $this->get(route("auth.{$network}.callback"))->assertRedirect(route('app.welcome', absolute: false));
 
-        expect($params)->toMatchArray(['timezone' => 'Asia/Tokyo', 'week_starts_on' => 'sunday', 'time_format' => '12h']);
+    expect(User::query()->where('email', "{$network}-from-login@example.com")->sole()->locale)->toBe(Locale::Spanish);
+})->with([
+    'google' => ['google', 'google-auth'],
+    'github' => ['github', 'github'],
+]);
+
+test('the register page opened from an invite sends the browser language with the invite', function () {
+    config()->set('trypost.google_auth_enabled', true);
+    config()->set('trypost.github_auth_enabled', true);
+
+    $account = Account::factory()->create();
+    $owner = User::factory()->create(['account_id' => $account->id]);
+    $account->update(['owner_id' => $owner->id]);
+    $workspace = Workspace::factory()->create(['account_id' => $account->id, 'user_id' => $owner->id]);
+    $invite = Invite::factory()->create([
+        'account_id' => $account->id,
+        'invited_by' => $owner->id,
+        'email' => 'invitee-browser@example.com',
+        'workspaces' => [$workspace->id],
+    ]);
+
+    $page = visit(route('register', ['invite' => $invite->id, 'email' => 'invitee-browser@example.com']))->withLocale('pt-BR');
+    waitForState($page, '@register-locale', "element.value !== ''");
+
+    $page->assertValue('@register-locale', 'pt-BR');
+
+    foreach (['@social-login-google', '@social-login-github'] as $button) {
+        expect(Uri::of($page->attribute($button, 'href'))->query()->all())
+            ->toMatchArray(['invite' => $invite->id, 'locale' => 'pt-BR']);
     }
 
     $page->assertNoJavaScriptErrors();
 });
+
+test('with several browser languages the first one TryPost supports wins', function (array $browserLanguages, string $expected) {
+    config()->set('trypost.self_hosted', false);
+
+    $page = visit(route('login'))->withLocale('en-US');
+    waitFor($page, '@login-sign-up-link');
+
+    $languages = json_encode($browserLanguages);
+    $page->script("Object.defineProperty(navigator, 'languages', { get: () => {$languages} })");
+    $page->click('@login-sign-up-link');
+    waitForState($page, '@register-locale', "element.value !== ''");
+
+    $page->assertValue('@register-locale', $expected)
+        ->assertNoJavaScriptErrors();
+})->with([
+    'English first, then Portuguese' => [['en-US', 'pt-BR'], 'en'],
+    'unsupported first, then Portuguese' => [['sv-SE', 'pt-BR'], 'pt-BR'],
+    'Portugal first, then Spanish' => [['pt-PT', 'es-ES'], 'pt-BR'],
+    'none supported' => [['sv-SE', 'fi-FI'], 'en'],
+]);
diff --git a/tests/Feature/Auth/SignupPreferencesTest.php b/tests/Feature/Auth/SignupPreferencesTest.php
index 8b6d463a2d..6ffde405b2 100644
--- a/tests/Feature/Auth/SignupPreferencesTest.php
+++ b/tests/Feature/Auth/SignupPreferencesTest.php
@@ -2,9 +2,15 @@
 
 declare(strict_types=1);
 
+use App\Enums\User\Locale;
 use App\Enums\User\TimeFormat;
 use App\Enums\User\WeekStart;
+use App\Jobs\PostHog\SyncUser;
+use App\Models\Account;
+use App\Models\Invite;
 use App\Models\User;
+use App\Models\Workspace;
+use Illuminate\Support\Facades\Queue;
 use Laravel\Socialite\Facades\Socialite;
 use Laravel\Socialite\Two\User as SocialiteUser;
 
@@ -110,3 +116,110 @@ function signupPreferencesSocialite(string $driver, string $id, string $email):
 
     expect(User::query()->where('email', 'returning@example.com')->sole()->timezone)->toBe('Europe/Lisbon');
 });
+
+test('email registration stores the language the register form sent and pushes it to PostHog', function () {
+    enablePostHog();
+    Queue::fake();
+
+    $this->post(route('register.store'), [
+        'name' => 'Bia',
+        'email' => 'bia-locale@example.com',
+        'password' => strongPassword(),
+        'locale' => 'pt-BR',
+    ])->assertSessionHasNoErrors();
+
+    $user = User::query()->where('email', 'bia-locale@example.com')->sole();
+
+    expect($user->locale)->toBe(Locale::PortugueseBrazil);
+    Queue::assertPushed(SyncUser::class, fn (SyncUser $job): bool => $job->userId === (string) $user->id);
+});
+
+test('social signup stores the language sent to the OAuth start and pushes it to PostHog', function (string $network, string $driver) {
+    enablePostHog();
+    Queue::fake();
+
+    $this->get(route("auth.{$network}.redirect", ['locale' => 'pt-BR']));
+    signupPreferencesSocialite($driver, "{$network}-locale", "{$network}-locale@example.com");
+
+    $this->get(route("auth.{$network}.callback"))->assertRedirect(route('app.welcome', absolute: false));
+
+    $user = User::query()->where('email', "{$network}-locale@example.com")->sole();
+
+    expect($user->locale)->toBe(Locale::PortugueseBrazil);
+    Queue::assertPushed(SyncUser::class, fn (SyncUser $job): bool => $job->userId === (string) $user->id);
+})->with([
+    'google' => ['google', 'google-auth'],
+    'github' => ['github', 'github'],
+]);
+
+test('social signup with an unsupported or missing language falls back to the default', function (string $network, string $driver, array $query) {
+    $this->get(route("auth.{$network}.redirect", $query));
+    signupPreferencesSocialite($driver, "{$network}-fallback", "{$network}-fallback@example.com");
+
+    $this->get(route("auth.{$network}.callback"))->assertRedirect(route('app.welcome', absolute: false));
+
+    expect(User::query()->where('email', "{$network}-fallback@example.com")->sole()->locale)->toBe(Locale::DEFAULT);
+})->with([
+    'google' => ['google', 'google-auth'],
+    'github' => ['github', 'github'],
+])->with([
+    'unsupported' => [['locale' => 'sv']],
+    'missing' => [[]],
+]);
+
+test('an existing user logging in with google or github keeps the language they already have', function (string $network, string $driver, string $idColumn) {
+    User::factory()->create(['email' => "{$network}-returning-locale@example.com", $idColumn => "{$network}-returning-locale", 'locale' => Locale::Japanese]);
+
+    $this->get(route("auth.{$network}.redirect", ['locale' => 'pt-BR']));
+    signupPreferencesSocialite($driver, "{$network}-returning-locale", "{$network}-returning-locale@example.com");
+
+    $this->get(route("auth.{$network}.callback"));
+
+    expect(User::query()->where('email', "{$network}-returning-locale@example.com")->sole()->locale)->toBe(Locale::Japanese);
+})->with([
+    'google' => ['google', 'google-auth', 'google_id'],
+    'github' => ['github', 'github', 'github_id'],
+]);
+
+function signupPreferencesInvite(string $email): Invite
+{
+    $account = Account::factory()->create();
+    $owner = User::factory()->create(['account_id' => $account->id]);
+    $account->update(['owner_id' => $owner->id]);
+    $workspace = Workspace::factory()->create(['account_id' => $account->id, 'user_id' => $owner->id]);
+
+    return Invite::factory()->create([
+        'account_id' => $account->id,
+        'invited_by' => $owner->id,
+        'email' => $email,
+        'workspaces' => [$workspace->id],
+    ]);
+}
+
+test('an invited email registration stores the language the register form sent', function () {
+    $invite = signupPreferencesInvite('invited-locale@example.com');
+
+    $this->post(route('register.store'), [
+        'name' => 'Invitee',
+        'email' => 'invited-locale@example.com',
+        'password' => strongPassword(),
+        'invite' => $invite->id,
+        'locale' => 'pt-BR',
+    ])->assertRedirect(route('app.invites.show', $invite, absolute: false));
+
+    expect(User::query()->where('email', 'invited-locale@example.com')->sole()->locale)->toBe(Locale::PortugueseBrazil);
+});
+
+test('an invited social signup stores the language sent to the OAuth start', function (string $network, string $driver) {
+    $invite = signupPreferencesInvite("{$network}-invited-locale@example.com");
+
+    $this->get(route("auth.{$network}.redirect", ['invite' => $invite->id, 'locale' => 'pt-BR']));
+    signupPreferencesSocialite($driver, "{$network}-invited-locale", "{$network}-invited-locale@example.com");
+
+    $this->get(route("auth.{$network}.callback"))->assertRedirect(route('app.invites.show', $invite, absolute: false));
+
+    expect(User::query()->where('email', "{$network}-invited-locale@example.com")->sole()->locale)->toBe(Locale::PortugueseBrazil);
+})->with([
+    'google' => ['google', 'google-auth'],
+    'github' => ['github', 'github'],
+]);