How to persist next-intl locale during social-provider sign-up?

I can’t figure out how to reliably save the user’s locale during social-provider sign-up (Google, GitHub, etc.).
My app uses next-intl, so the locale is always a path param (/en/…, /cs/…).
With email+password I simply send locale in the body, but OAuth redirects lose this value.
Current attempt
Client (Next.js 15 + better-auth 1.3.2):

onClick={async () => {
 await authClient.signIn.social({
  provider: link.id,
  newUserCallbackURL: `/dashboard?locale=${locale}`,
 });
}}

onClick={async () => {
 await authClient.signIn.social({
  provider: link.id,
  newUserCallbackURL: `/dashboard?locale=${locale}`,
 });
}}

onClick={async () => {
 await authClient.signIn.social({
  provider: link.id,
  newUserCallbackURL: `/dashboard?locale=${locale}`,
 });
}}

onClick={async () => {
 await authClient.signIn.social({
  provider: link.id,
  newUserCallbackURL: `/dashboard?locale=${locale}`,
 });
}}

Server after hook:

if (ctx.path.startsWith("/sign-in/social")) {
 const locale =
 (ctx.query?.state as string)
 ?.split("&")
 .find((p) => p.startsWith("locale="))
 ?.split("=")[1] || "en";
 console.log(locale);
 const newSession = ctx.context.session;
 console.log(newSession);
 if (newSession) {
   await userRepository.updateUserLocale(newSession.user.id, locale);
  }
}

if (ctx.path.startsWith("/sign-in/social")) {
 const locale =
 (ctx.query?.state as string)
 ?.split("&")
 .find((p) => p.startsWith("locale="))
 ?.split("=")[1] || "en";
 console.log(locale);
 const newSession = ctx.context.session;
 console.log(newSession);
 if (newSession) {
   await userRepository.updateUserLocale(newSession.user.id, locale);
  }
}

if (ctx.path.startsWith("/sign-in/social")) {
 const locale =
 (ctx.query?.state as string)
 ?.split("&")
 .find((p) => p.startsWith("locale="))
 ?.split("=")[1] || "en";
 console.log(locale);
 const newSession = ctx.context.session;
 console.log(newSession);
 if (newSession) {
   await userRepository.updateUserLocale(newSession.user.id, locale);
  }
}

if (ctx.path.startsWith("/sign-in/social")) {
 const locale =
 (ctx.query?.state as string)
 ?.split("&")
 .find((p) => p.startsWith("locale="))
 ?.split("=")[1] || "en";
 console.log(locale);
 const newSession = ctx.context.session;
 console.log(newSession);
 if (newSession) {
   await userRepository.updateUserLocale(newSession.user.id, locale);
  }
}

What I’m missing
-How should I forward the locale so the callback handler can read it?
-Which exact path (/callback/:provider?) and which field (query.state, query.locale, body?) should I check?
-Is there a built-in way to pass arbitrary data (like locale) through the OAuth flow, or must I use cookies / custom state?
Happy to refactor the code—just need the canonical pattern.
Thanks!

Solution

Solution:

      if (ctx.path.startsWith("/callback/")) { //Here just use a /callback/ to catch all OAuth routes
        const newSession = ctx.context.newSession ?? ctx.context.session;
        if (newSession) {
          try {
            const locale = ctx.getCookie("NEXT_LOCALE") || "en";
            await userRepository.updateUserLocale(newSession.user.id, locale);
            console.log(
              `OAuth user ${newSession.user.id} created with locale: ${locale}`
            );
          } catch (error) {
            console.error("Failed to set OAuth user locale:", error);
          }
        }
      }

      if (ctx.path.startsWith("/callback/")) { //Here just use a /callback/ to catch all OAuth routes
        const newSession = ctx.context.newSession ?? ctx.context.session;
        if (newSession) {
          try {
            const locale = ctx.getCookie("NEXT_LOCALE") || "en";
            await userRepository.updateUserLocale(newSession.user.id, locale);
            console.log(
              `OAuth user ${newSession.user.id} created with locale: ${locale}`
            );
          } catch (error) {
            console.error("Failed to set OAuth user locale:", error);
          }
        }
      }

      if (ctx.path.startsWith("/callback/")) { //Here just use a /callback/ to catch all OAuth routes
        const newSession = ctx.context.newSession ?? ctx.context.session;
        if (newSession) {
          try {
            const locale = ctx.getCookie("NEXT_LOCALE") || "en";
            await userRepository.updateUserLocale(newSession.user.id, locale);
            console.log(
              `OAuth user ${newSession.user.id} created with locale: ${locale}`
            );
          } catch (error) {
            console.error("Failed to set OAuth user locale:", error);
          }
        }
      }

      if (ctx.path.startsWith("/callback/")) { //Here just use a /callback/ to catch all OAuth routes
        const newSession = ctx.context.newSession ?? ctx.context.session;
        if (newSession) {
          try {
            const locale = ctx.getCookie("NEXT_LOCALE") || "en";
            await userRepository.updateUserLocale(newSession.user.id, locale);
            console.log(
              `OAuth user ${newSession.user.id} created with locale: ${locale}`
            );
          } catch (error) {
            console.error("Failed to set OAuth user locale:", error);
          }
        }
      }

Jump to solution

Vlad•7/27/25, 9:07 AM

I think the best solution is to store the user's locale in cookies

Vlad•7/27/25, 9:07 AM

So you'll be able to get it in any request

VVlad I think the best solution is to store the user's locale in cookies

ddevOP•7/27/25, 10:16 AM

I store in a cookies but i am not able to get locale from it. I will show this approach also a bit later, not at home

ddevOP•7/27/25, 2:23 PM

@Vlad i had a function

import { cookies } from "next/headers";
const getLocaleFromCookies = async (): Promise<string> => {
  try {
    const cookieStore = await cookies();
    const localeCookie = cookieStore.get("NEXT_LOCALE");
    console.log(cookieStore);
    return localeCookie?.value || "en";
  } catch (error) {
    console.warn("Failed to get locale from cookies:", error);
    return "en";
  }
};

import { cookies } from "next/headers";
const getLocaleFromCookies = async (): Promise<string> => {
  try {
    const cookieStore = await cookies();
    const localeCookie = cookieStore.get("NEXT_LOCALE");
    console.log(cookieStore);
    return localeCookie?.value || "en";
  } catch (error) {
    console.warn("Failed to get locale from cookies:", error);
    return "en";
  }
};

Which i was using to get cookies inside my after hook

 if (ctx.path.startsWith("/sign-in/social")) {
        const newSession = ctx.context.newSession;
        if (newSession) {
          try {
            const locale = await getLocaleFromCookies();
            await userRepository.updateUserLocale(newSession.user.id, locale);
            console.log(
              `OAuth user ${newSession.user.id} created with locale: ${locale}`
            );
          } catch (error) {
            console.error("Failed to set OAuth user locale:", error);
          }
        }
      }

 if (ctx.path.startsWith("/sign-in/social")) {
        const newSession = ctx.context.newSession;
        if (newSession) {
          try {
            const locale = await getLocaleFromCookies();
            await userRepository.updateUserLocale(newSession.user.id, locale);
            console.log(
              `OAuth user ${newSession.user.id} created with locale: ${locale}`
            );
          } catch (error) {
            console.error("Failed to set OAuth user locale:", error);
          }
        }
      }

But it have not worked, i was getting a default "en" locale in all cases

Vlad•7/27/25, 2:26 PM

You should do const locale = ctx.getCookie("NEXT_LOCALE")const locale = ctx.getCookie("NEXT_LOCALE")

Vlad•7/27/25, 2:27 PM

VVlad You should do `const locale = ctx.getCookie("NEXT_LOCALE")`

ddevOP•7/27/25, 2:27 PM

so not to use a custom function but instead try to access cookies from a context? I would try

Vlad•7/27/25, 2:27 PM

Cookies()Cookies(),

headers()

headers()

, etc work only in server actions or route handlers

Dddev so not to use a custom function but instead try to access cookies from a context...

Vlad•7/27/25, 2:27 PM

Yeah

ddevOP•7/27/25, 2:36 PM

@Vlad getting null from newSession

      if (ctx.path.startsWith("/sign-in/social")) {
        const newSession = ctx.context.newSession;
        console.log(newSession);
        if (newSession) {
          try {
            console.log(ctx.getCookie("NEXT_LOCALE"));
            const locale = ctx.getCookie("NEXT_LOCALE") || "en";
            await userRepository.updateUserLocale(newSession.user.id, locale);
            console.log(
              `OAuth user ${newSession.user.id} created with locale: ${locale}`
            );
          } catch (error) {
            console.error("Failed to set OAuth user locale:", error);
          }
        }
      }

      if (ctx.path.startsWith("/sign-in/social")) {
        const newSession = ctx.context.newSession;
        console.log(newSession);
        if (newSession) {
          try {
            console.log(ctx.getCookie("NEXT_LOCALE"));
            const locale = ctx.getCookie("NEXT_LOCALE") || "en";
            await userRepository.updateUserLocale(newSession.user.id, locale);
            console.log(
              `OAuth user ${newSession.user.id} created with locale: ${locale}`
            );
          } catch (error) {
            console.error("Failed to set OAuth user locale:", error);
          }
        }
      }

ddevOP•7/27/25, 6:32 PM

someone?

Dddev @Vlad getting null from newSession ``` if (ctx.path.startsWith("/sign-in/...

Vlad•7/27/25, 7:43 PM

Try to log all context and see what's there

VVlad Try to log all context and see what's there

ddevOP•7/27/25, 8:10 PM

in this code i dont even see a logs lol. may it be coz i am not hitting path "/callback/google" or console.log(ctx.context) runs on a client so while i am getting fast redirect i cant see a logs in a console?

  hooks: {
    after: createAuthMiddleware(async (ctx) => {
      if (ctx.path.startsWith("/sign-up")) {
        const newSession = ctx.context.newSession;
        if (newSession) {
          try {
            const locale = ctx.body?.locale || "en";

            await userRepository.updateUserLocale(newSession.user.id, locale);

            console.log(
              `User ${newSession.user.id} created with locale: ${locale}`
            );
          } catch (error) {
            console.error("Failed to set user locale:", error);
          }
        }
      }

      if (ctx.path === "/callback/google") {
        console.log(ctx.context);
        const locale = (ctx.query?.locale as string) || "en";
        const newSession = ctx.context.newSession ?? ctx.context.session;
        if (newSession) {
          await userRepository.updateUserLocale(newSession.user.id, locale);
        }
      }
    }),
  },

  hooks: {
    after: createAuthMiddleware(async (ctx) => {
      if (ctx.path.startsWith("/sign-up")) {
        const newSession = ctx.context.newSession;
        if (newSession) {
          try {
            const locale = ctx.body?.locale || "en";

            await userRepository.updateUserLocale(newSession.user.id, locale);

            console.log(
              `User ${newSession.user.id} created with locale: ${locale}`
            );
          } catch (error) {
            console.error("Failed to set user locale:", error);
          }
        }
      }

      if (ctx.path === "/callback/google") {
        console.log(ctx.context);
        const locale = (ctx.query?.locale as string) || "en";
        const newSession = ctx.context.newSession ?? ctx.context.session;
        if (newSession) {
          await userRepository.updateUserLocale(newSession.user.id, locale);
        }
      }
    }),
  },

Vlad•7/27/25, 8:12 PM

First you check if it starts with sign-up, then you check if it equals, that's why it never runs that if

Vlad•7/27/25, 8:12 PM

Just log the context at the start of the function

VVlad Just log the context at the start of the function

ddevOP•7/27/25, 8:28 PM

thank you, it helped a lot to understand how ctx works. i found out that my path was wrong and now i successfully can update a locale by cookies. thank you man

Vlad•7/27/25, 8:28 PM

Пожалуйста)

Solution

ddev•7/27/25, 8:29 PM

Solution:

      if (ctx.path.startsWith("/callback/")) { //Here just use a /callback/ to catch all OAuth routes
        const newSession = ctx.context.newSession ?? ctx.context.session;
        if (newSession) {
          try {
            const locale = ctx.getCookie("NEXT_LOCALE") || "en";
            await userRepository.updateUserLocale(newSession.user.id, locale);
            console.log(
              `OAuth user ${newSession.user.id} created with locale: ${locale}`
            );
          } catch (error) {
            console.error("Failed to set OAuth user locale:", error);
          }
        }
      }

      if (ctx.path.startsWith("/callback/")) { //Here just use a /callback/ to catch all OAuth routes
        const newSession = ctx.context.newSession ?? ctx.context.session;
        if (newSession) {
          try {
            const locale = ctx.getCookie("NEXT_LOCALE") || "en";
            await userRepository.updateUserLocale(newSession.user.id, locale);
            console.log(
              `OAuth user ${newSession.user.id} created with locale: ${locale}`
            );
          } catch (error) {
            console.error("Failed to set OAuth user locale:", error);
          }
        }
      }

How to persist next-intl locale during social-provider sign-up?

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