fix(web/i18n): persist Desktop language from config.yaml on startup (#26665)

tests/agent/test_i18n.py

@@ -95,6 +95,11 @@ def test_normalize_lang_accepts_aliases():
     assert i18n._normalize_lang("Turkish") == "tr"
     assert i18n._normalize_lang("tr-TR") == "tr"
     assert i18n._normalize_lang("türkçe") == "tr"
+    # Regional Portuguese tags should both land on the shared `pt` catalog
+    # rather than silently falling back to English (#26665).
+    assert i18n._normalize_lang("pt-BR") == "pt"
+    assert i18n._normalize_lang("pt-PT") == "pt"
+    assert i18n._normalize_lang("brazilian") == "pt"
 
 
 def test_normalize_lang_unknown_falls_back():

web/src/i18n/context.tsx

@@ -1,5 +1,6 @@
-import { createContext, useContext, useState, useCallback, type ReactNode } from "react";
+import { createContext, useContext, useState, useCallback, useEffect, type ReactNode } from "react";
 import type { Locale, Translations } from "./types";
+import { api } from "@/lib/api";
 import { en } from "./en";
 import { zh } from "./zh";
 import { zhHant } from "./zh-hant";
@@ -62,18 +63,70 @@ export const LOCALE_META: Record<Locale, { name: string; flag: string }> = {
 const SUPPORTED_LOCALES = Object.keys(TRANSLATIONS) as Locale[];
 const STORAGE_KEY = "hermes-locale";
 
+// Aliases for values users (or config.yaml) may supply that aren't bare
+// locale codes — common BCP-47 regional tags ("pt-BR", "zh-CN") plus a few
+// English/endonym names.  Mirrors agent/i18n.py so the Desktop and CLI
+// route the same input to the same catalog.
+const LOCALE_ALIASES: Record<string, Locale> = {
+  "en-us": "en", "en-gb": "en", english: "en",
+  "zh-cn": "zh", "zh-hans": "zh", "zh-sg": "zh", chinese: "zh",
+  "zh-tw": "zh-hant", "zh-hk": "zh-hant", "zh-mo": "zh-hant",
+  "ja-jp": "ja", jp: "ja", japanese: "ja",
+  "de-de": "de", "de-at": "de", "de-ch": "de", german: "de",
+  "es-es": "es", "es-mx": "es", "es-ar": "es", spanish: "es",
+  "fr-fr": "fr", "fr-be": "fr", "fr-ca": "fr", "fr-ch": "fr", french: "fr",
+  "tr-tr": "tr", turkish: "tr",
+  "uk-ua": "uk", ua: "uk", ukrainian: "uk",
+  "af-za": "af", afrikaans: "af",
+  "ko-kr": "ko", korean: "ko",
+  "it-it": "it", "it-ch": "it", italian: "it",
+  "ga-ie": "ga", irish: "ga",
+  "pt-pt": "pt", "pt-br": "pt", portuguese: "pt", brazilian: "pt",
+  "ru-ru": "ru", russian: "ru",
+  "hu-hu": "hu", hungarian: "hu",
+};
+
 function isLocale(value: string): value is Locale {
   return (SUPPORTED_LOCALES as string[]).includes(value);
 }
 
-function getInitialLocale(): Locale {
+export function normalizeLocale(value: unknown): Locale | null {
+  if (typeof value !== "string") return null;
+  const key = value.trim().toLowerCase();
+  if (!key) return null;
+  if (isLocale(key)) return key;
+  if (key in LOCALE_ALIASES) return LOCALE_ALIASES[key];
+  const base = key.split("-", 1)[0];
+  if (isLocale(base)) return base;
+  return null;
+}
+
+function readStoredLocale(): Locale | null {
   try {
     const stored = localStorage.getItem(STORAGE_KEY);
-    if (stored && isLocale(stored)) return stored;
+    return stored ? normalizeLocale(stored) : null;
   } catch {
     // SSR or privacy mode
+    return null;
+  }
+}
+
+function getInitialLocale(): Locale {
+  return readStoredLocale() ?? "en";
+}
+
+// Read display.language from config.yaml via /api/config.  Used to seed the
+// initial UI language for users who set the value in config.yaml directly
+// (e.g. CLI setup wizard) without touching the in-browser dropdown.  See
+// issue #26665.
+async function fetchConfigLocale(): Promise<Locale | null> {
+  try {
+    const cfg = await api.getConfig();
+    const display = (cfg as { display?: { language?: unknown } }).display;
+    return normalizeLocale(display?.language);
+  } catch {
+    return null;
   }
-  return "en";
 }
 
 interface I18nContextValue {
@@ -91,6 +144,22 @@ const I18nContext = createContext<I18nContextValue>({
 export function I18nProvider({ children }: { children: ReactNode }) {
   const [locale, setLocaleState] = useState<Locale>(getInitialLocale);
 
+  // If the user never touched the in-browser dropdown (no localStorage
+  // entry) honour display.language from config.yaml on startup.  An
+  // explicit dropdown choice — saved to localStorage — always wins.
+  useEffect(() => {
+    if (readStoredLocale()) return;
+    let cancelled = false;
+    fetchConfigLocale().then((fromConfig) => {
+      if (!cancelled && fromConfig && !readStoredLocale()) {
+        setLocaleState(fromConfig);
+      }
+    });
+    return () => {
+      cancelled = true;
+    };
+  }, []);
+
   const setLocale = useCallback((l: Locale) => {
     setLocaleState(l);
     try {