diff --git a/bun.lock b/bun.lock
index 13647ffa1..d02afd42d 100644
--- a/bun.lock
+++ b/bun.lock
@@ -186,6 +186,7 @@
       "dependencies": {
         "@opencode-ai/app": "workspace:*",
         "@opencode-ai/ui": "workspace:*",
+        "@solid-primitives/i18n": "2.2.1",
         "@solid-primitives/storage": "catalog:",
         "@tauri-apps/api": "^2",
         "@tauri-apps/plugin-dialog": "~2",
diff --git a/packages/desktop/package.json b/packages/desktop/package.json
index cc6b3af99..49e032339 100644
--- a/packages/desktop/package.json
+++ b/packages/desktop/package.json
@@ -15,6 +15,7 @@
   "dependencies": {
     "@opencode-ai/app": "workspace:*",
     "@opencode-ai/ui": "workspace:*",
+    "@solid-primitives/i18n": "2.2.1",
     "@solid-primitives/storage": "catalog:",
     "@tauri-apps/api": "^2",
     "@tauri-apps/plugin-dialog": "~2",
diff --git a/packages/desktop/src/cli.ts b/packages/desktop/src/cli.ts
index 965ed6ddc..5a8875cf8 100644
--- a/packages/desktop/src/cli.ts
+++ b/packages/desktop/src/cli.ts
@@ -1,13 +1,15 @@
 import { invoke } from "@tauri-apps/api/core"
 import { message } from "@tauri-apps/plugin-dialog"
 
+import { initI18n, t } from "./i18n"
+
 export async function installCli(): Promise<void> {
+  await initI18n()
+
   try {
     const path = await invoke<string>("install_cli")
-    await message(`CLI installed to ${path}\n\nRestart your terminal to use the 'opencode' command.`, {
-      title: "CLI Installed",
-    })
+    await message(t("desktop.cli.installed.message", { path }), { title: t("desktop.cli.installed.title") })
   } catch (e) {
-    await message(`Failed to install CLI: ${e}`, { title: "Installation Failed" })
+    await message(t("desktop.cli.failed.message", { error: String(e) }), { title: t("desktop.cli.failed.title") })
   }
 }
diff --git a/packages/desktop/src/i18n/en.ts b/packages/desktop/src/i18n/en.ts
new file mode 100644
index 000000000..4008efca5
--- /dev/null
+++ b/packages/desktop/src/i18n/en.ts
@@ -0,0 +1,31 @@
+export const dict = {
+  "desktop.menu.checkForUpdates": "Check for Updates...",
+  "desktop.menu.installCli": "Install CLI...",
+  "desktop.menu.reloadWebview": "Reload Webview",
+  "desktop.menu.restart": "Restart",
+
+  "desktop.dialog.chooseFolder": "Choose a folder",
+  "desktop.dialog.chooseFile": "Choose a file",
+  "desktop.dialog.saveFile": "Save file",
+
+  "desktop.updater.checkFailed.title": "Update Check Failed",
+  "desktop.updater.checkFailed.message": "Failed to check for updates",
+  "desktop.updater.none.title": "No Update Available",
+  "desktop.updater.none.message": "You are already using the latest version of OpenCode",
+  "desktop.updater.downloadFailed.title": "Update Failed",
+  "desktop.updater.downloadFailed.message": "Failed to download update",
+  "desktop.updater.downloaded.title": "Update Downloaded",
+  "desktop.updater.downloaded.prompt":
+    "Version {{version}} of OpenCode has been downloaded, would you like to install it and relaunch?",
+  "desktop.updater.installFailed.title": "Update Failed",
+  "desktop.updater.installFailed.message": "Failed to install update",
+
+  "desktop.cli.installed.title": "CLI Installed",
+  "desktop.cli.installed.message": "CLI installed to {{path}}\n\nRestart your terminal to use the 'opencode' command.",
+  "desktop.cli.failed.title": "Installation Failed",
+  "desktop.cli.failed.message": "Failed to install CLI: {{error}}",
+
+  "desktop.error.serverStartFailed.title": "OpenCode failed to start",
+  "desktop.error.serverStartFailed.description":
+    "The local OpenCode server could not be started. Restart the app, or check your network settings (VPN/proxy) and try again.",
+} as const
diff --git a/packages/desktop/src/i18n/index.ts b/packages/desktop/src/i18n/index.ts
new file mode 100644
index 000000000..34a427c7a
--- /dev/null
+++ b/packages/desktop/src/i18n/index.ts
@@ -0,0 +1,134 @@
+import * as i18n from "@solid-primitives/i18n"
+import { Store } from "@tauri-apps/plugin-store"
+
+import { dict as desktopEn } from "./en"
+
+import { dict as appEn } from "../../../app/src/i18n/en"
+import { dict as appZh } from "../../../app/src/i18n/zh"
+import { dict as appZht } from "../../../app/src/i18n/zht"
+import { dict as appKo } from "../../../app/src/i18n/ko"
+import { dict as appDe } from "../../../app/src/i18n/de"
+import { dict as appEs } from "../../../app/src/i18n/es"
+import { dict as appFr } from "../../../app/src/i18n/fr"
+import { dict as appDa } from "../../../app/src/i18n/da"
+import { dict as appJa } from "../../../app/src/i18n/ja"
+import { dict as appPl } from "../../../app/src/i18n/pl"
+import { dict as appRu } from "../../../app/src/i18n/ru"
+import { dict as appAr } from "../../../app/src/i18n/ar"
+import { dict as appNo } from "../../../app/src/i18n/no"
+import { dict as appBr } from "../../../app/src/i18n/br"
+
+export type Locale = "en" | "zh" | "zht" | "ko" | "de" | "es" | "fr" | "da" | "ja" | "pl" | "ru" | "ar" | "no" | "br"
+
+type RawDictionary = typeof appEn & typeof desktopEn
+type Dictionary = i18n.Flatten<RawDictionary>
+
+const LOCALES: readonly Locale[] = ["en", "zh", "zht", "ko", "de", "es", "fr", "da", "ja", "pl", "ru", "ar", "no", "br"]
+
+function detectLocale(): Locale {
+  if (typeof navigator !== "object") return "en"
+
+  const languages = navigator.languages?.length ? navigator.languages : [navigator.language]
+  for (const language of languages) {
+    if (!language) continue
+    if (language.toLowerCase().startsWith("zh")) {
+      if (language.toLowerCase().includes("hant")) return "zht"
+      return "zh"
+    }
+    if (language.toLowerCase().startsWith("ko")) return "ko"
+    if (language.toLowerCase().startsWith("de")) return "de"
+    if (language.toLowerCase().startsWith("es")) return "es"
+    if (language.toLowerCase().startsWith("fr")) return "fr"
+    if (language.toLowerCase().startsWith("da")) return "da"
+    if (language.toLowerCase().startsWith("ja")) return "ja"
+    if (language.toLowerCase().startsWith("pl")) return "pl"
+    if (language.toLowerCase().startsWith("ru")) return "ru"
+    if (language.toLowerCase().startsWith("ar")) return "ar"
+    if (
+      language.toLowerCase().startsWith("no") ||
+      language.toLowerCase().startsWith("nb") ||
+      language.toLowerCase().startsWith("nn")
+    )
+      return "no"
+    if (language.toLowerCase().startsWith("pt")) return "br"
+  }
+
+  return "en"
+}
+
+function parseLocale(value: unknown): Locale | null {
+  if (!value) return null
+  if (typeof value !== "string") return null
+  if ((LOCALES as readonly string[]).includes(value)) return value as Locale
+  return null
+}
+
+function parseRecord(value: unknown) {
+  if (!value || typeof value !== "object") return null
+  if (Array.isArray(value)) return null
+  return value as Record<string, unknown>
+}
+
+function pickLocale(value: unknown): Locale | null {
+  const direct = parseLocale(value)
+  if (direct) return direct
+
+  const record = parseRecord(value)
+  if (!record) return null
+
+  return parseLocale(record.locale)
+}
+
+const base = i18n.flatten({ ...appEn, ...desktopEn })
+
+function build(locale: Locale): Dictionary {
+  if (locale === "en") return base
+  if (locale === "zh") return { ...base, ...i18n.flatten(appZh) }
+  if (locale === "zht") return { ...base, ...i18n.flatten(appZht) }
+  if (locale === "de") return { ...base, ...i18n.flatten(appDe) }
+  if (locale === "es") return { ...base, ...i18n.flatten(appEs) }
+  if (locale === "fr") return { ...base, ...i18n.flatten(appFr) }
+  if (locale === "da") return { ...base, ...i18n.flatten(appDa) }
+  if (locale === "ja") return { ...base, ...i18n.flatten(appJa) }
+  if (locale === "pl") return { ...base, ...i18n.flatten(appPl) }
+  if (locale === "ru") return { ...base, ...i18n.flatten(appRu) }
+  if (locale === "ar") return { ...base, ...i18n.flatten(appAr) }
+  if (locale === "no") return { ...base, ...i18n.flatten(appNo) }
+  if (locale === "br") return { ...base, ...i18n.flatten(appBr) }
+  return { ...base, ...i18n.flatten(appKo) }
+}
+
+const state = {
+  locale: detectLocale(),
+  dict: base as Dictionary,
+  init: undefined as Promise<Locale> | undefined,
+}
+
+state.dict = build(state.locale)
+
+const translate = i18n.translator(() => state.dict, i18n.resolveTemplate)
+
+export function t(key: keyof Dictionary, params?: Record<string, string | number>) {
+  return translate(key, params)
+}
+
+export function initI18n(): Promise<Locale> {
+  const cached = state.init
+  if (cached) return cached
+
+  const promise = (async () => {
+    const store = await Store.load("opencode.global.dat").catch(() => null)
+    if (!store) return state.locale
+
+    const raw = await store.get("language").catch(() => null)
+    const value = typeof raw === "string" ? JSON.parse(raw) : raw
+    const next = pickLocale(value) ?? state.locale
+
+    state.locale = next
+    state.dict = build(next)
+    return next
+  })().catch(() => state.locale)
+
+  state.init = promise
+  return promise
+}
diff --git a/packages/desktop/src/index.tsx b/packages/desktop/src/index.tsx
index b19adfeda..344c6be8d 100644
--- a/packages/desktop/src/index.tsx
+++ b/packages/desktop/src/index.tsx
@@ -18,16 +18,17 @@ import { createSignal, Show, Accessor, JSX, createResource, onMount, onCleanup }
 
 import { UPDATER_ENABLED } from "./updater"
 import { createMenu } from "./menu"
+import { initI18n, t } from "./i18n"
 import pkg from "../package.json"
 import "./styles.css"
 
 const root = document.getElementById("root")
 if (import.meta.env.DEV && !(root instanceof HTMLElement)) {
-  throw new Error(
-    "Root element not found. Did you forget to add it to your index.html? Or maybe the id attribute got misspelled?",
-  )
+  throw new Error(t("error.dev.rootNotFound"))
 }
 
+void initI18n()
+
 // Floating UI can call getComputedStyle with non-elements (e.g., null refs, virtual elements).
 // This happens on all platforms (WebView2 on Windows, WKWebView on macOS), not just Windows.
 const originalGetComputedStyle = window.getComputedStyle
@@ -54,7 +55,7 @@ const createPlatform = (password: Accessor<string | null>): Platform => ({
     const result = await open({
       directory: true,
       multiple: opts?.multiple ?? false,
-      title: opts?.title ?? "Choose a folder",
+      title: opts?.title ?? t("desktop.dialog.chooseFolder"),
     })
     return result
   },
@@ -63,14 +64,14 @@ const createPlatform = (password: Accessor<string | null>): Platform => ({
     const result = await open({
       directory: false,
       multiple: opts?.multiple ?? false,
-      title: opts?.title ?? "Choose a file",
+      title: opts?.title ?? t("desktop.dialog.chooseFile"),
     })
     return result
   },
 
   async saveFilePickerDialog(opts) {
     const result = await save({
-      title: opts?.title ?? "Save file",
+      title: opts?.title ?? t("desktop.dialog.saveFile"),
       defaultPath: opts?.defaultPath,
     })
     return result
@@ -380,7 +381,7 @@ function ServerGate(props: { children: (data: Accessor<ServerReadyData>) => JSX.
 
   const errorMessage = () => {
     const error = serverData.error
-    if (!error) return "Unknown error"
+    if (!error) return t("error.chain.unknown")
     if (typeof error === "string") return error
     if (error instanceof Error) return error.message
     return String(error)
@@ -410,16 +411,15 @@ function ServerGate(props: { children: (data: Accessor<ServerReadyData>) => JSX.
       }
     >
       <div class="h-screen w-screen flex flex-col items-center justify-center bg-background-base gap-4 px-6">
-        <div class="text-16-semibold">OpenCode failed to start</div>
+        <div class="text-16-semibold">{t("desktop.error.serverStartFailed.title")}</div>
         <div class="text-12-regular opacity-70 text-center max-w-xl">
-          The local OpenCode server could not be started. Restart the app, or check your network settings (VPN/proxy)
-          and try again.
+          {t("desktop.error.serverStartFailed.description")}
         </div>
         <div class="w-full max-w-3xl rounded border border-border bg-background-base overflow-auto max-h-64">
           <pre class="p-3 whitespace-pre-wrap break-words text-11-regular">{errorMessage()}</pre>
         </div>
         <button class="px-3 py-2 rounded bg-primary text-primary-foreground" onClick={() => void restartApp()}>
-          Restart App
+          {t("error.page.action.restart")}
         </button>
         <div data-tauri-decorum-tb class="flex flex-row absolute top-0 right-0 z-10 h-10" />
       </div>
diff --git a/packages/desktop/src/menu.ts b/packages/desktop/src/menu.ts
index 1b4c61135..2edeff42b 100644
--- a/packages/desktop/src/menu.ts
+++ b/packages/desktop/src/menu.ts
@@ -5,10 +5,13 @@ import { relaunch } from "@tauri-apps/plugin-process"
 
 import { runUpdater, UPDATER_ENABLED } from "./updater"
 import { installCli } from "./cli"
+import { initI18n, t } from "./i18n"
 
 export async function createMenu() {
   if (ostype() !== "macos") return
 
+  await initI18n()
+
   const menu = await Menu.new({
     items: [
       await Submenu.new({
@@ -20,22 +23,22 @@ export async function createMenu() {
           await MenuItem.new({
             enabled: UPDATER_ENABLED,
             action: () => runUpdater({ alertOnFail: true }),
-            text: "Check For Updates...",
+            text: t("desktop.menu.checkForUpdates"),
           }),
           await MenuItem.new({
             action: () => installCli(),
-            text: "Install CLI...",
+            text: t("desktop.menu.installCli"),
           }),
           await MenuItem.new({
             action: async () => window.location.reload(),
-            text: "Reload Webview",
+            text: t("desktop.menu.reloadWebview"),
           }),
           await MenuItem.new({
             action: async () => {
               await invoke("kill_sidecar").catch(() => undefined)
               await relaunch().catch(() => undefined)
             },
-            text: "Restart",
+            text: t("desktop.menu.restart"),
           }),
           await PredefinedMenuItem.new({
             item: "Separator",
diff --git a/packages/desktop/src/updater.ts b/packages/desktop/src/updater.ts
index 4753ee663..b48bb6be0 100644
--- a/packages/desktop/src/updater.ts
+++ b/packages/desktop/src/updater.ts
@@ -4,41 +4,45 @@ import { ask, message } from "@tauri-apps/plugin-dialog"
 import { invoke } from "@tauri-apps/api/core"
 import { type as ostype } from "@tauri-apps/plugin-os"
 
+import { initI18n, t } from "./i18n"
+
 export const UPDATER_ENABLED = window.__OPENCODE__?.updaterEnabled ?? false
 
 export async function runUpdater({ alertOnFail }: { alertOnFail: boolean }) {
+  await initI18n()
+
   let update
   try {
     update = await check()
   } catch {
-    if (alertOnFail) await message("Failed to check for updates", { title: "Update Check Failed" })
+    if (alertOnFail)
+      await message(t("desktop.updater.checkFailed.message"), { title: t("desktop.updater.checkFailed.title") })
     return
   }
 
   if (!update) {
-    if (alertOnFail)
-      await message("You are already using the latest version of OpenCode", { title: "No Update Available" })
+    if (alertOnFail) await message(t("desktop.updater.none.message"), { title: t("desktop.updater.none.title") })
     return
   }
 
   try {
     await update.download()
   } catch {
-    if (alertOnFail) await message("Failed to download update", { title: "Update Failed" })
+    if (alertOnFail)
+      await message(t("desktop.updater.downloadFailed.message"), { title: t("desktop.updater.downloadFailed.title") })
     return
   }
 
-  const shouldUpdate = await ask(
-    `Version ${update.version} of OpenCode has been downloaded, would you like to install it and relaunch?`,
-    { title: "Update Downloaded" },
-  )
+  const shouldUpdate = await ask(t("desktop.updater.downloaded.prompt", { version: update.version }), {
+    title: t("desktop.updater.downloaded.title"),
+  })
   if (!shouldUpdate) return
 
   try {
     if (ostype() === "windows") await invoke("kill_sidecar")
     await update.install()
   } catch {
-    await message("Failed to install update", { title: "Update Failed" })
+    await message(t("desktop.updater.installFailed.message"), { title: t("desktop.updater.installFailed.title") })
     return
   }