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Upgrade i18next v26 + react-i18next v17 with SSR-safe init

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Split initI18n() into separate server/client initialization paths
inspired by remix-i18next's architecture:

- initI18nServer(lng): no LanguageDetector, per-request language from
  Accept-Language header
- initI18nClient(): LanguageDetector reads <html lang> first to match
  server, then localStorage and navigator
- detectLanguage(request): parses Accept-Language for best match

Fixes rehydration errors caused by v26 removing initImmediate option
(replaced with initAsync) and LanguageDetector running on the server
where browser APIs don't exist.

Also makes <html lang> dynamic instead of hardcoded "en".

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
This commit is contained in:
Ullrich Schäfer 2026-03-29 11:38:36 +02:00
parent 4be716687a
commit 79f000fcc5
No known key found for this signature in database
GPG key ID: A32FF691A0F752D9
10 changed files with 166 additions and 40 deletions
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3
apps/journal/app/entry.client.tsx
View file

@ -4,6 +4,7 @@ import { startTransition, StrictMode } from "react";
import { hydrateRoot } from "react-dom/client";
import { HydratedRouter } from "react-router/dom";
import { useLocation, useNavigationType, createRoutesFromChildren, matchRoutes } from "react-router";
import { initI18nClient } from "@trails-cool/i18n";
const sentryEnvironment = import.meta.env.VITE_SENTRY_ENVIRONMENT ??
(import.meta.env.PROD ? "production" : "development");
@ -24,6 +25,8 @@ Sentry.init({
enabled: import.meta.env.PROD && sentryEnvironment !== "ci",
});
initI18nClient();
startTransition(() => {
hydrateRoot(
document,

3
apps/journal/app/entry.server.tsx
View file

@ -6,6 +6,7 @@ import { ServerRouter } from "react-router";
import { isbot } from "isbot";
import type { RenderToPipeableStreamOptions } from "react-dom/server";
import { renderToPipeableStream } from "react-dom/server";
import { initI18nServer, detectLanguage } from "@trails-cool/i18n";
const sentryEnvironment = process.env.CI ? "ci" : (process.env.NODE_ENV ?? "development");
@ -32,6 +33,8 @@ export default function handleRequest(
routerContext: EntryContext,
_loadContext: AppLoadContext,
) {
initI18nServer(detectLanguage(request));
if (request.method.toUpperCase() === "HEAD") {
return new Response(null, {
status: responseStatusCode,

6
apps/journal/app/root.tsx
View file

@ -4,17 +4,15 @@ import type { LinksFunction } from "react-router";
import type { Route } from "./+types/root";
import * as Sentry from "@sentry/react";
import { useTranslation } from "react-i18next";
import { initI18n } from "@trails-cool/i18n";
import { getSessionUser } from "~/lib/auth.server";
import stylesheet from "@trails-cool/ui/styles.css?url";
initI18n();
export const links: LinksFunction = () => [{ rel: "stylesheet", href: stylesheet }];
export function Layout({ children }: { children: React.ReactNode }) {
const { i18n } = useTranslation();
return (
<html lang="en">
<html lang={i18n.language}>
<head>
<meta charSet="utf-8" />
<meta name="viewport" content="width=device-width, initial-scale=1" />

3
apps/planner/app/entry.client.tsx
View file

@ -4,6 +4,7 @@ import { startTransition, StrictMode } from "react";
import { hydrateRoot } from "react-dom/client";
import { HydratedRouter } from "react-router/dom";
import { useLocation, useNavigationType, createRoutesFromChildren, matchRoutes } from "react-router";
import { initI18nClient } from "@trails-cool/i18n";
const sentryEnvironment = import.meta.env.VITE_SENTRY_ENVIRONMENT ??
(import.meta.env.PROD ? "production" : "development");
@ -24,6 +25,8 @@ Sentry.init({
enabled: import.meta.env.PROD && sentryEnvironment !== "ci",
});
initI18nClient();
startTransition(() => {
hydrateRoot(
document,

79
apps/planner/app/entry.server.tsx Normal file
View file

@ -0,0 +1,79 @@
import { PassThrough } from "node:stream";
import type { AppLoadContext, EntryContext } from "react-router";
import { createReadableStreamFromReadable } from "@react-router/node";
import { ServerRouter } from "react-router";
import { isbot } from "isbot";
import type { RenderToPipeableStreamOptions } from "react-dom/server";
import { renderToPipeableStream } from "react-dom/server";
import { initI18nServer, detectLanguage } from "@trails-cool/i18n";
export const streamTimeout = 5_000;
export default function handleRequest(
request: Request,
responseStatusCode: number,
responseHeaders: Headers,
routerContext: EntryContext,
_loadContext: AppLoadContext,
) {
initI18nServer(detectLanguage(request));
if (request.method.toUpperCase() === "HEAD") {
return new Response(null, {
status: responseStatusCode,
headers: responseHeaders,
});
}
return new Promise((resolve, reject) => {
let shellRendered = false;
const userAgent = request.headers.get("user-agent");
const readyOption: keyof RenderToPipeableStreamOptions =
(userAgent && isbot(userAgent)) || routerContext.isSpaMode
? "onAllReady"
: "onShellReady";
let timeoutId: ReturnType<typeof setTimeout> | undefined = setTimeout(
() => abort(),
streamTimeout + 1000,
);
const { pipe, abort } = renderToPipeableStream(
<ServerRouter context={routerContext} url={request.url} />,
{
[readyOption]() {
shellRendered = true;
const body = new PassThrough({
final(callback) {
clearTimeout(timeoutId);
timeoutId = undefined;
callback();
},
});
const stream = createReadableStreamFromReadable(body);
responseHeaders.set("Content-Type", "text/html");
pipe(body);
resolve(
new Response(stream, {
headers: responseHeaders,
status: responseStatusCode,
}),
);
},
onShellError(error: unknown) {
reject(error);
},
onError(error: unknown) {
responseStatusCode = 500;
if (shellRendered) {
console.error(error);
}
},
},
);
});
}

6
apps/planner/app/root.tsx
View file

@ -3,16 +3,14 @@ import type { LinksFunction } from "react-router";
import type { Route } from "./+types/root";
import * as Sentry from "@sentry/react";
import { useTranslation } from "react-i18next";
import { initI18n } from "@trails-cool/i18n";
import stylesheet from "@trails-cool/ui/styles.css?url";
initI18n();
export const links: LinksFunction = () => [{ rel: "stylesheet", href: stylesheet }];
export function Layout({ children }: { children: React.ReactNode }) {
const { i18n } = useTranslation();
return (
<html lang="en">
<html lang={i18n.language}>
<head>
<meta charSet="utf-8" />
<meta name="viewport" content="width=device-width, initial-scale=1" />

4
package.json
View file

@ -49,7 +49,7 @@
"drizzle-postgis": "^1.1.1",
"eslint": "^10.1.0",
"eslint-config-prettier": "^10.1.8",
"i18next": "^25.10.4",
"i18next": "^26.0.1",
"i18next-browser-languagedetector": "^8.2.1",
"jsdom": "^29.0.1",
"leaflet": "^1.9.4",
@ -59,7 +59,7 @@
"prettier": "^3.8.1",
"react": "^19.2.4",
"react-dom": "^19.2.4",
"react-i18next": "^16.6.1",
"react-i18next": "^17.0.1",
"react-leaflet": "^5.0.0",
"react-router": "^7.13.2",
"tailwindcss": "^4.2.2",

4
packages/i18n/package.json
View file

@ -10,7 +10,7 @@
"types": "./src/index.ts",
"peerDependencies": {
"react": ">=18",
"i18next": ">=23",
"react-i18next": ">=14"
"i18next": ">=26",
"react-i18next": ">=17"
}
}

62
packages/i18n/src/index.ts
View file

@ -6,26 +6,68 @@ import de from "./locales/de.ts";
export const defaultNS = "common";
export const supportedLngs = ["en", "de"] as const;
export type SupportedLng = (typeof supportedLngs)[number];
export const resources = {
en: { common: en.common, planner: en.planner, journal: en.journal },
de: { common: de.common, planner: de.planner, journal: de.journal },
} as const;
export function initI18n() {
return i18n
const commonOptions = {
resources,
defaultNS,
fallbackLng: "en" as const,
supportedLngs: [...supportedLngs],
interpolation: { escapeValue: false },
initAsync: false,
};
/**
* Initialize i18next for server-side rendering.
* No language detector — language is determined from the request.
*/
export function initI18nServer(lng: SupportedLng = "en") {
if (i18n.isInitialized) {
i18n.changeLanguage(lng);
return;
}
i18n.use(initReactI18next).init({ ...commonOptions, lng });
}
/**
* Initialize i18next for the client.
* Uses LanguageDetector with htmlTag priority so hydration matches the server.
*/
export function initI18nClient() {
if (i18n.isInitialized) return;
i18n
.use(LanguageDetector)
.use(initReactI18next)
.init({
resources,
defaultNS,
fallbackLng: "en",
supportedLngs: ["en", "de"],
interpolation: {
escapeValue: false,
...commonOptions,
detection: {
order: ["htmlTag", "localStorage", "navigator"],
caches: ["localStorage"],
},
showSupportNotice: false,
initImmediate: false,
});
}
/**
* Detect the best supported language from a request's Accept-Language header.
*/
export function detectLanguage(request: Request): SupportedLng {
const header = request.headers.get("Accept-Language") ?? "";
for (const part of header.split(",")) {
const lang = part.split(";")[0]?.trim().toLowerCase();
if (!lang) continue;
for (const supported of supportedLngs) {
if (lang === supported || lang.startsWith(supported + "-")) {
return supported;
}
}
}
return "en";
}
export { i18n };

36
pnpm-lock.yaml generated
View file

@ -113,8 +113,8 @@ importers:
specifier: ^10.1.8
version: 10.1.8(eslint@10.1.0(jiti@2.6.1))
i18next:
specifier: ^25.10.4
version: 25.10.4(typescript@5.9.3)
specifier: ^26.0.1
version: 26.0.1(typescript@5.9.3)
i18next-browser-languagedetector:
specifier: ^8.2.1
version: 8.2.1
@ -143,8 +143,8 @@ importers:
specifier: ^19.2.4
version: 19.2.4(react@19.2.4)
react-i18next:
specifier: ^16.6.1
version: 16.6.1(i18next@25.10.4(typescript@5.9.3))(react-dom@19.2.4(react@19.2.4))(react@19.2.4)(typescript@5.9.3)
specifier: ^17.0.1
version: 17.0.1(i18next@26.0.1(typescript@5.9.3))(react-dom@19.2.4(react@19.2.4))(react@19.2.4)(typescript@5.9.3)
react-leaflet:
specifier: ^5.0.0
version: 5.0.0(leaflet@1.9.4)(react-dom@19.2.4(react@19.2.4))(react@19.2.4)
@ -382,14 +382,14 @@ importers:
packages/i18n:
dependencies:
i18next:
specifier: '>=23'
version: 25.10.4(typescript@5.9.3)
specifier: '>=26'
version: 26.0.1(typescript@5.9.3)
react:
specifier: '>=18'
version: 19.2.4
react-i18next:
specifier: '>=14'
version: 16.6.1(i18next@25.10.4(typescript@5.9.3))(react-dom@19.2.4(react@19.2.4))(react@19.2.4)(typescript@5.9.3)
specifier: '>=17'
version: 17.0.1(i18next@26.0.1(typescript@5.9.3))(react-dom@19.2.4(react@19.2.4))(react@19.2.4)(typescript@5.9.3)
packages/map:
dependencies:
@ -2744,10 +2744,10 @@ packages:
i18next-browser-languagedetector@8.2.1:
resolution: {integrity: sha512-bZg8+4bdmaOiApD7N7BPT9W8MLZG+nPTOFlLiJiT8uzKXFjhxw4v2ierCXOwB5sFDMtuA5G4kgYZ0AznZxQ/cw==}
i18next@25.10.4:
resolution: {integrity: sha512-XsE/6eawy090meuFU0BTY9BtmWr1m9NSwLr0NK7/A04LA58wdAvDsi9WNOJ40Qb1E9NIPbvnVLZEN2fWDd3/3Q==}
i18next@26.0.1:
resolution: {integrity: sha512-vtz5sXU4+nkCm8yEU+JJ6yYIx0mkg9e68W0G0PXpnOsmzLajNsW5o28DJMqbajxfsfq0gV3XdrBudsDQnwxfsQ==}
peerDependencies:
typescript: ^5
typescript: ^5 || ^6
peerDependenciesMeta:
typescript:
optional: true
@ -3278,14 +3278,14 @@ packages:
peerDependencies:
react: ^19.2.4
react-i18next@16.6.1:
resolution: {integrity: sha512-izjXh+AkBLy3h3xe3sh6Gg1flhFHc3UyzsMftMKYJr2Z7WvAZQIdjjpHypctN41zFoeLdJUNGDgP1+Qich2fYg==}
react-i18next@17.0.1:
resolution: {integrity: sha512-iG65FGnFHcYyHNuT01ukffYWCOBFTWSdVD8EZd/dCVWgtjFPObcSsvYYNwcsokO/rDcTb5d6D8Acv8MrOdm6Hw==}
peerDependencies:
i18next: '>= 25.6.2'
i18next: '>= 26.0.1'
react: '>= 16.8.0'
react-dom: '*'
react-native: '*'
typescript: ^5
typescript: ^5 || ^6
peerDependenciesMeta:
react-dom:
optional: true
@ -6169,7 +6169,7 @@ snapshots:
dependencies:
'@babel/runtime': 7.29.2
i18next@25.10.4(typescript@5.9.3):
i18next@26.0.1(typescript@5.9.3):
dependencies:
'@babel/runtime': 7.29.2
optionalDependencies:
@ -6637,11 +6637,11 @@ snapshots:
react: 19.2.4
scheduler: 0.27.0
react-i18next@16.6.1(i18next@25.10.4(typescript@5.9.3))(react-dom@19.2.4(react@19.2.4))(react@19.2.4)(typescript@5.9.3):
react-i18next@17.0.1(i18next@26.0.1(typescript@5.9.3))(react-dom@19.2.4(react@19.2.4))(react@19.2.4)(typescript@5.9.3):
dependencies:
'@babel/runtime': 7.29.2
html-parse-stringify: 3.0.1
i18next: 25.10.4(typescript@5.9.3)
i18next: 26.0.1(typescript@5.9.3)
react: 19.2.4
use-sync-external-store: 1.6.0(react@19.2.4)
optionalDependencies: