perf(ui): defer locale and overlay bundles (#238)

## Summary
- defer locale and overlay loading work away from the first critical
render path
- seed locale state from the bootstrap preload so the first render can
use the preloaded language immediately
- keep bootstrap cache and locale fallback behavior consistent on
subsequent launches

## Testing
- npm run build --workspace @codenomad/ui

packages/ui/src/components/instance/shell/right-panel/RightPanel.tsx

@@ -1,8 +1,10 @@
 import {
   Show,
+  Suspense,
   createEffect,
   createMemo,
   createSignal,
+  lazy,
   onCleanup,
   type Accessor,
   type Component,
@@ -20,11 +22,6 @@ import type { Session } from "../../../../types/session"
 import type { DrawerViewState } from "../types"
 import type { DiffContextMode, DiffViewMode, DiffWordWrapMode, RightPanelTab } from "./types"
 
-import ChangesTab from "./tabs/ChangesTab"
-import FilesTab from "./tabs/FilesTab"
-import GitChangesTab from "./tabs/GitChangesTab"
-import StatusTab from "./tabs/StatusTab"
-
 import { getDefaultWorktreeSlug, getOrCreateWorktreeClient, getWorktreeSlugForSession } from "../../../../stores/worktrees"
 import { requestData } from "../../../../lib/opencode-api"
 import { buildUnifiedDiffFromSdkPatch, tryReverseApplyUnifiedDiff } from "../../../../lib/unified-diff-reverse"
@@ -49,6 +46,15 @@ import {
   readStoredRightPanelTab,
 } from "../storage"
 
+const LazyChangesTab = lazy(() => import("./tabs/ChangesTab"))
+const LazyGitChangesTab = lazy(() => import("./tabs/GitChangesTab"))
+const LazyFilesTab = lazy(() => import("./tabs/FilesTab"))
+const LazyStatusTab = lazy(() => import("./tabs/StatusTab"))
+
+function RightPanelTabFallback() {
+  return <div class="flex-1 min-h-0" />
+}
+
 interface RightPanelProps {
   t: (key: string, vars?: Record<string, any>) => string
 
@@ -565,6 +571,13 @@ const RightPanel: Component<RightPanelProps> = (props) => {
     void loadBrowserEntries(browserPath())
   })
 
+  createEffect(() => {
+    if (rightPanelTab() === "files") return
+    setBrowserSelectedContent(null)
+    setBrowserSelectedLoading(false)
+    setBrowserSelectedError(null)
+  })
+
   createEffect(() => {
     if (rightPanelTab() !== "git-changes") return
     if (gitStatusLoading()) return
@@ -572,6 +585,14 @@ const RightPanel: Component<RightPanelProps> = (props) => {
     void loadGitStatus()
   })
 
+  createEffect(() => {
+    if (rightPanelTab() === "git-changes") return
+    setGitSelectedBefore(null)
+    setGitSelectedAfter(null)
+    setGitSelectedLoading(false)
+    setGitSelectedError(null)
+  })
+
   const handleSelectChangesFile = (file: string, closeList: boolean) => {
     setSelectedFile(file)
     if (closeList) {
@@ -738,101 +759,109 @@ const RightPanel: Component<RightPanelProps> = (props) => {
 
       <div class="flex-1 overflow-y-auto">
         <Show when={rightPanelTab() === "changes"}>
-          <ChangesTab
-            t={props.t}
-            instanceId={props.instanceId}
-            activeSessionId={props.activeSessionId}
-            activeSessionDiffs={props.activeSessionDiffs}
-            selectedFile={selectedFile}
-            onSelectFile={handleSelectChangesFile}
-            diffViewMode={diffViewMode}
-            diffContextMode={diffContextMode}
-            diffWordWrapMode={diffWordWrapMode}
-            onViewModeChange={setDiffViewMode}
-            onContextModeChange={setDiffContextMode}
-            onWordWrapModeChange={setDiffWordWrapMode}
-            listOpen={changesListOpen}
-            onToggleList={toggleChangesList}
-            splitWidth={changesSplitWidth}
-            onResizeMouseDown={handleSplitResizeMouseDown("changes")}
-            onResizeTouchStart={handleSplitResizeTouchStart("changes")}
-            isPhoneLayout={props.isPhoneLayout}
-          />
+          <Suspense fallback={<RightPanelTabFallback />}>
+            <LazyChangesTab
+              t={props.t}
+              instanceId={props.instanceId}
+              activeSessionId={props.activeSessionId}
+              activeSessionDiffs={props.activeSessionDiffs}
+              selectedFile={selectedFile}
+              onSelectFile={handleSelectChangesFile}
+              diffViewMode={diffViewMode}
+              diffContextMode={diffContextMode}
+              diffWordWrapMode={diffWordWrapMode}
+              onViewModeChange={setDiffViewMode}
+              onContextModeChange={setDiffContextMode}
+              onWordWrapModeChange={setDiffWordWrapMode}
+              listOpen={changesListOpen}
+              onToggleList={toggleChangesList}
+              splitWidth={changesSplitWidth}
+              onResizeMouseDown={handleSplitResizeMouseDown("changes")}
+              onResizeTouchStart={handleSplitResizeTouchStart("changes")}
+              isPhoneLayout={props.isPhoneLayout}
+            />
+          </Suspense>
         </Show>
 
         <Show when={rightPanelTab() === "git-changes"}>
-          <GitChangesTab
-            t={props.t}
-            activeSessionId={props.activeSessionId}
-            entries={gitStatusEntries}
-            statusLoading={gitStatusLoading}
-            statusError={gitStatusError}
-            selectedPath={gitSelectedPath}
-            selectedLoading={gitSelectedLoading}
-            selectedError={gitSelectedError}
-            selectedBefore={gitSelectedBefore}
-            selectedAfter={gitSelectedAfter}
-            mostChangedPath={gitMostChangedPath}
-            scopeKey={gitScopeKey}
-            diffViewMode={diffViewMode}
-            diffContextMode={diffContextMode}
-            diffWordWrapMode={diffWordWrapMode}
-            onViewModeChange={setDiffViewMode}
-            onContextModeChange={setDiffContextMode}
-            onWordWrapModeChange={setDiffWordWrapMode}
-            onOpenFile={(path) => void openGitFile(path)}
-            onRefresh={() => void refreshGitStatus()}
-            listOpen={gitChangesListOpen}
-            onToggleList={toggleGitList}
-            splitWidth={gitChangesSplitWidth}
-            onResizeMouseDown={handleSplitResizeMouseDown("git-changes")}
-            onResizeTouchStart={handleSplitResizeTouchStart("git-changes")}
-            isPhoneLayout={props.isPhoneLayout}
-          />
+          <Suspense fallback={<RightPanelTabFallback />}>
+            <LazyGitChangesTab
+              t={props.t}
+              activeSessionId={props.activeSessionId}
+              entries={gitStatusEntries}
+              statusLoading={gitStatusLoading}
+              statusError={gitStatusError}
+              selectedPath={gitSelectedPath}
+              selectedLoading={gitSelectedLoading}
+              selectedError={gitSelectedError}
+              selectedBefore={gitSelectedBefore}
+              selectedAfter={gitSelectedAfter}
+              mostChangedPath={gitMostChangedPath}
+              scopeKey={gitScopeKey}
+              diffViewMode={diffViewMode}
+              diffContextMode={diffContextMode}
+              diffWordWrapMode={diffWordWrapMode}
+              onViewModeChange={setDiffViewMode}
+              onContextModeChange={setDiffContextMode}
+              onWordWrapModeChange={setDiffWordWrapMode}
+              onOpenFile={(path: string) => void openGitFile(path)}
+              onRefresh={() => void refreshGitStatus()}
+              listOpen={gitChangesListOpen}
+              onToggleList={toggleGitList}
+              splitWidth={gitChangesSplitWidth}
+              onResizeMouseDown={handleSplitResizeMouseDown("git-changes")}
+              onResizeTouchStart={handleSplitResizeTouchStart("git-changes")}
+              isPhoneLayout={props.isPhoneLayout}
+            />
+          </Suspense>
         </Show>
 
         <Show when={rightPanelTab() === "files"}>
-          <FilesTab
-            t={props.t}
-            browserPath={browserPath}
-            browserEntries={browserEntries}
-            browserLoading={browserLoading}
-            browserError={browserError}
-            browserSelectedPath={browserSelectedPath}
-            browserSelectedContent={browserSelectedContent}
-            browserSelectedLoading={browserSelectedLoading}
-            browserSelectedError={browserSelectedError}
-            parentPath={browserParentPath}
-            scopeKey={browserScopeKey}
-            onLoadEntries={(path) => void loadBrowserEntries(path)}
-            onOpenFile={(path) => void openBrowserFile(path)}
-            onRefresh={() => void refreshFilesTab()}
-            listOpen={filesListOpen}
-            onToggleList={toggleFilesList}
-            splitWidth={filesSplitWidth}
-            onResizeMouseDown={handleSplitResizeMouseDown("files")}
-            onResizeTouchStart={handleSplitResizeTouchStart("files")}
-            isPhoneLayout={props.isPhoneLayout}
-          />
+          <Suspense fallback={<RightPanelTabFallback />}>
+            <LazyFilesTab
+              t={props.t}
+              browserPath={browserPath}
+              browserEntries={browserEntries}
+              browserLoading={browserLoading}
+              browserError={browserError}
+              browserSelectedPath={browserSelectedPath}
+              browserSelectedContent={browserSelectedContent}
+              browserSelectedLoading={browserSelectedLoading}
+              browserSelectedError={browserSelectedError}
+              parentPath={browserParentPath}
+              scopeKey={browserScopeKey}
+              onLoadEntries={(path: string) => void loadBrowserEntries(path)}
+              onOpenFile={(path: string) => void openBrowserFile(path)}
+              onRefresh={() => void refreshFilesTab()}
+              listOpen={filesListOpen}
+              onToggleList={toggleFilesList}
+              splitWidth={filesSplitWidth}
+              onResizeMouseDown={handleSplitResizeMouseDown("files")}
+              onResizeTouchStart={handleSplitResizeTouchStart("files")}
+              isPhoneLayout={props.isPhoneLayout}
+            />
+          </Suspense>
         </Show>
 
         <Show when={rightPanelTab() === "status"}>
-          <StatusTab
-            t={props.t}
-            instanceId={props.instanceId}
-            instance={props.instance}
-            activeSessionId={props.activeSessionId}
-            activeSession={props.activeSession}
-            activeSessionDiffs={props.activeSessionDiffs}
-            latestTodoState={props.latestTodoState}
-            backgroundProcessList={props.backgroundProcessList}
-            onOpenBackgroundOutput={props.onOpenBackgroundOutput}
-            onStopBackgroundProcess={props.onStopBackgroundProcess}
-            onTerminateBackgroundProcess={props.onTerminateBackgroundProcess}
-            expandedItems={rightPanelExpandedItems}
-            onExpandedItemsChange={handleAccordionChange}
-            onOpenChangesTab={openChangesTabFromStatus}
-          />
+          <Suspense fallback={<RightPanelTabFallback />}>
+            <LazyStatusTab
+              t={props.t}
+              instanceId={props.instanceId}
+              instance={props.instance}
+              activeSessionId={props.activeSessionId}
+              activeSession={props.activeSession}
+              activeSessionDiffs={props.activeSessionDiffs}
+              latestTodoState={props.latestTodoState}
+              backgroundProcessList={props.backgroundProcessList}
+              onOpenBackgroundOutput={props.onOpenBackgroundOutput}
+              onStopBackgroundProcess={props.onStopBackgroundProcess}
+              onTerminateBackgroundProcess={props.onTerminateBackgroundProcess}
+              expandedItems={rightPanelExpandedItems}
+              onExpandedItemsChange={handleAccordionChange}
+              onOpenChangesTab={openChangesTabFromStatus}
+            />
+          </Suspense>
         </Show>
       </div>
     </div>

packages/ui/src/components/message-block.tsx

@@ -1,7 +1,6 @@
-import { For, Match, Show, Switch, createEffect, createMemo, createSignal, onCleanup, untrack } from "solid-js"
+import { For, Match, Show, Suspense, Switch, createEffect, createMemo, createSignal, lazy, onCleanup, untrack } from "solid-js"
 import { ChevronsDownUp, ChevronsUpDown, ExternalLink, FoldVertical, ListStart, Trash } from "lucide-solid"
 import MessageItem from "./message-item"
-import ToolCall from "./tool-call"
 import type { InstanceMessageStore } from "../stores/message-v2/instance-store"
 import type { ClientPart, MessageInfo } from "../types/message"
 import { partHasRenderableText } from "../types/message"
@@ -29,6 +28,12 @@ const USER_BORDER_COLOR = "var(--message-user-border)"
 const ASSISTANT_BORDER_COLOR = "var(--message-assistant-border)"
 const TOOL_BORDER_COLOR = "var(--message-tool-border)"
 
+const LazyToolCall = lazy(() => import("./tool-call"))
+
+function ToolCallFallback() {
+  return <div class="tool-call tool-call-loading" />
+}
+
 type ToolCallPart = Extract<ClientPart, { type: "tool" }>
 
 
@@ -500,16 +505,18 @@ function ToolCallItem(props: ToolCallItemProps) {
             </div>
           </div>
 
-          <ToolCall
-            toolCall={resolvedToolPart()}
-            toolCallId={props.partId}
-            messageId={props.messageId}
-            messageVersion={messageVersion()}
-            partVersion={partVersion()}
-            instanceId={props.instanceId}
-            sessionId={props.sessionId}
-            onContentRendered={props.onContentRendered}
-          />
+          <Suspense fallback={<ToolCallFallback />}>
+            <LazyToolCall
+              toolCall={resolvedToolPart()}
+              toolCallId={props.partId}
+              messageId={props.messageId}
+              messageVersion={messageVersion()}
+              partVersion={partVersion()}
+              instanceId={props.instanceId}
+              sessionId={props.sessionId}
+              onContentRendered={props.onContentRendered}
+            />
+          </Suspense>
         </div>
       )}
     </Show>

packages/ui/src/components/message-part.tsx

@@ -1,5 +1,4 @@
-import { Show, Match, Switch } from "solid-js"
-import ToolCall from "./tool-call"
+import { Match, Show, Suspense, Switch, lazy } from "solid-js"
 import { isItemExpanded, toggleItemExpanded } from "../stores/tool-call-state"
 import { Markdown } from "./markdown"
 import { useTheme } from "../lib/theme"
@@ -7,6 +6,8 @@ import { partHasRenderableText, SDKPart, TextPart, ClientPart } from "../types/m
 
 type ToolCallPart = Extract<ClientPart, { type: "tool" }>
 
+const LazyToolCall = lazy(() => import("./tool-call"))
+
 interface MessagePartProps {
   part: ClientPart
   messageType?: "user" | "assistant"
@@ -153,12 +154,14 @@ export default function MessagePart(props: MessagePartProps) {
       </Match>
 
       <Match when={partType() === "tool"}>
-        <ToolCall
-          toolCall={props.part as ToolCallPart}
-          toolCallId={props.part?.id}
-          instanceId={props.instanceId}
-          sessionId={props.sessionId}
-        />
+        <Suspense fallback={<div class="tool-call tool-call-loading" />}>
+          <LazyToolCall
+            toolCall={props.part as ToolCallPart}
+            toolCallId={props.part?.id}
+            instanceId={props.instanceId}
+            sessionId={props.sessionId}
+          />
+        </Suspense>
       </Match>
 
 

packages/ui/src/components/permission-approval-modal.tsx

@@ -1,4 +1,4 @@
-import { For, Show, createMemo, createSignal, createEffect, onCleanup, type Component } from "solid-js"
+import { For, Show, Suspense, createMemo, createSignal, createEffect, lazy, onCleanup, type Component } from "solid-js"
 import type { PermissionRequestLike } from "../types/permission"
 import { getPermissionCallId, getPermissionDisplayTitle, getPermissionKind, getPermissionMessageId, getPermissionSessionId } from "../types/permission"
 import { getQuestionCallId, getQuestionMessageId, getQuestionSessionId, type QuestionRequest } from "../types/question"
@@ -12,7 +12,8 @@ import {
 } from "../stores/instances"
 import { ensureSessionParentExpanded, loadMessages, sessions as sessionStateSessions, setActiveSessionFromList } from "../stores/sessions"
 import { messageStoreBus } from "../stores/message-v2/bus"
-import ToolCall from "./tool-call"
+
+const LazyToolCall = lazy(() => import("./tool-call"))
 
 interface PermissionApprovalModalProps {
   instanceId: string
@@ -408,15 +409,17 @@ const PermissionApprovalModal: Component<PermissionApprovalModalProps> = (props)
                             }
                           >
                           {(data) => (
-                            <ToolCall
-                              toolCall={data().toolPart}
-                              toolCallId={data().toolPart.id}
-                              messageId={data().messageId}
-                              messageVersion={data().messageVersion}
-                              partVersion={data().partVersion}
-                              instanceId={props.instanceId}
-                              sessionId={data().sessionId}
-                            />
+                            <Suspense fallback={<div class="tool-call tool-call-loading" />}>
+                              <LazyToolCall
+                                toolCall={data().toolPart}
+                                toolCallId={data().toolPart.id}
+                                messageId={data().messageId}
+                                messageVersion={data().messageVersion}
+                                partVersion={data().partVersion}
+                                instanceId={props.instanceId}
+                                sessionId={data().sessionId}
+                              />
+                            </Suspense>
                           )}
                         </Show>
                       </div>

packages/ui/src/components/prompt-input.tsx

@@ -1,6 +1,5 @@
-import { createSignal, Show, onMount, onCleanup, createEffect, on } from "solid-js"
+import { Suspense, createEffect, createSignal, lazy, on, onCleanup, onMount, Show } from "solid-js"
 import { ArrowBigUp, ArrowBigDown } from "lucide-solid"
-import UnifiedPicker from "./unified-picker"
 import ExpandButton from "./expand-button"
 import { clearAttachments, removeAttachment } from "../stores/attachments"
 import { resolvePastedPlaceholders } from "../lib/prompt-placeholders"
@@ -20,6 +19,7 @@ import { usePromptAttachments } from "./prompt-input/usePromptAttachments"
 import { usePromptPicker } from "./prompt-input/usePromptPicker"
 import { usePromptKeyDown } from "./prompt-input/usePromptKeyDown"
 const log = getLogger("actions")
+const LazyUnifiedPicker = lazy(() => import("./unified-picker"))
 
 function getConsumedPastedTextAttachmentIds(text: string, attachments: Attachment[]): string[] {
   if (!text || attachments.length === 0) return []
@@ -467,18 +467,20 @@ export default function PromptInput(props: PromptInputProps) {
         onDrop={handleDrop}
       >
         <Show when={showPicker() && instance()}>
-          <UnifiedPicker
-            open={showPicker()}
-            mode={pickerMode()}
-            onClose={handlePickerClose}
-            onSelect={handlePickerSelect}
-            agents={instanceAgents()}
-            commands={getCommands(props.instanceId)}
-            instanceClient={instance()!.client}
-            searchQuery={searchQuery()}
-            textareaRef={textareaRef}
-            workspaceId={props.instanceId}
-          />
+          <Suspense fallback={null}>
+            <LazyUnifiedPicker
+              open={showPicker()}
+              mode={pickerMode()}
+              onClose={handlePickerClose}
+              onSelect={handlePickerSelect}
+              agents={instanceAgents()}
+              commands={getCommands(props.instanceId)}
+              instanceClient={instance()!.client}
+              searchQuery={searchQuery()}
+              textareaRef={textareaRef}
+              workspaceId={props.instanceId}
+            />
+          </Suspense>
         </Show>
 
         <div class="flex flex-1 flex-col">

packages/ui/src/components/tool-call.tsx

@@ -514,6 +514,7 @@ function ToolCallDetails(props: {
   })
 
   const { renderDiffContent } = createDiffContentRenderer({
+    toolState: props.toolState,
     preferences: props.preferences,
     setDiffViewMode: props.setDiffViewMode,
     isDark: props.isDark,

packages/ui/src/components/tool-call/ansi-render.tsx

@@ -20,6 +20,14 @@ export function createAnsiContentRenderer(params: {
   const runningAnsiRenderer = createAnsiStreamRenderer()
   let runningAnsiSource = ""
 
+  const registerTracked = (element: HTMLDivElement | null) => {
+    params.scrollHelpers.registerContainer(element)
+  }
+
+  const registerUntracked = (element: HTMLDivElement | null) => {
+    params.scrollHelpers.registerContainer(element, { disableTracking: true })
+  }
+
   const getMode = () => {
     const version = params.partVersion?.()
     return typeof version === "number" ? String(version) : undefined
@@ -36,6 +44,8 @@ export function createAnsiContentRenderer(params: {
     const cached = cacheHandle.get<AnsiRenderCache>()
     const mode = getMode()
     const isRunningVariant = options.variant === "running"
+    const disableScrollTracking = !isRunningVariant
+    const registerRef = disableScrollTracking ? registerUntracked : registerTracked
 
     let nextCache: AnsiRenderCache
 
@@ -87,9 +97,9 @@ export function createAnsiContentRenderer(params: {
     }
 
     return (
-      <div class={messageClass} ref={params.scrollHelpers.registerContainer} onScroll={params.scrollHelpers.handleScroll}>
+      <div class={messageClass} ref={registerRef} onScroll={disableScrollTracking ? undefined : params.scrollHelpers.handleScroll}>
         <pre class="tool-call-content tool-call-ansi" dir="auto" innerHTML={nextCache.html} />
-        {params.scrollHelpers.renderSentinel()}
+        {params.scrollHelpers.renderSentinel({ disableTracking: disableScrollTracking })}
       </div>
     )
   }

packages/ui/src/components/tool-call/diff-render.tsx

@@ -1,4 +1,5 @@
 import { Suspense, lazy, onMount, type Accessor, type JSXElement } from "solid-js"
+import type { ToolState } from "@opencode-ai/sdk/v2"
 import type { RenderCache } from "../../types/message"
 import type { DiffViewMode } from "../../stores/preferences"
 import type { DiffPayload, DiffRenderOptions, ToolScrollHelpers } from "./types"
@@ -31,6 +32,7 @@ type DiffPrefs = {
 }
 
 export function createDiffContentRenderer(params: {
+  toolState: Accessor<ToolState | undefined>
   preferences: Accessor<DiffPrefs>
   setDiffViewMode: (mode: DiffViewMode) => void
   isDark: Accessor<boolean>
@@ -58,7 +60,10 @@ export function createDiffContentRenderer(params: {
     const cacheHandle = selectedVariant === "permission-diff" ? params.permissionDiffCache : params.diffCache
     const diffMode = () => (params.preferences().diffViewMode || "split") as DiffViewMode
     const themeKey = params.isDark() ? "dark" : "light"
-    const disableScrollTracking = Boolean(options?.disableScrollTracking)
+    const state = params.toolState()
+    const disableScrollTracking = Boolean(
+      options?.disableScrollTracking || (state?.status !== "running" && state?.status !== "pending"),
+    )
     const registerRef = disableScrollTracking ? registerUntracked : registerTracked
 
     const baseEntryParams = cacheHandle.params() as any

packages/ui/src/components/tool-call/markdown-render.tsx

@@ -31,10 +31,9 @@ export function createMarkdownContentRenderer(params: {
     const size = options.size || "default"
     const disableHighlight = options.disableHighlight || false
     const messageClass = `message-text tool-call-markdown${size === "large" ? " tool-call-markdown-large" : ""}`
-    const disableScrollTracking = options.disableScrollTracking || false
-    const registerRef = disableScrollTracking ? registerUntracked : registerTracked
-
     const state = params.toolState()
+    const disableScrollTracking = options.disableScrollTracking || (state?.status !== "running" && state?.status !== "pending")
+    const registerRef = disableScrollTracking ? registerUntracked : registerTracked
     const shouldDeferMarkdown = Boolean(state && (state.status === "running" || state.status === "pending") && disableHighlight)
     if (shouldDeferMarkdown) {
       return (

packages/ui/src/lib/i18n/index.tsx

@@ -2,11 +2,6 @@ import { createContext, createEffect, createMemo, createSignal, onCleanup, onMou
 import type { ParentComponent } from "solid-js"
 import { useConfig } from "../../stores/preferences"
 import { enMessages } from "./messages/en"
-import { esMessages } from "./messages/es"
-import { frMessages } from "./messages/fr"
-import { ruMessages } from "./messages/ru"
-import { jaMessages } from "./messages/ja"
-import { zhHansMessages } from "./messages/zh-Hans"
 
 type Messages = Record<string, string>
 
@@ -15,14 +10,18 @@ export type TranslateParams = Record<string, unknown>
 export type Locale = "en" | "es" | "fr" | "ru" | "ja" | "zh-Hans"
 
 const SUPPORTED_LOCALES: readonly Locale[] = ["en", "es", "fr", "ru", "ja", "zh-Hans"] as const
+const SUPPORTED_LOCALES_BY_LOWER = new Map(SUPPORTED_LOCALES.map((locale) => [locale.toLowerCase(), locale]))
 
-const messagesByLocale: Record<Locale, Messages> = {
-  en: enMessages,
-  es: esMessages,
-  fr: frMessages,
-  ru: ruMessages,
-  ja: jaMessages,
-  "zh-Hans": zhHansMessages,
+const localeMessagesCache = new Map<Locale, Messages>([["en", enMessages]])
+const localeMessagesPromises = new Map<Locale, Promise<Messages>>()
+
+const localeLoaders: Record<Locale, () => Promise<Messages>> = {
+  en: async () => enMessages,
+  es: async () => (await import("./messages/es")).esMessages,
+  fr: async () => (await import("./messages/fr")).frMessages,
+  ru: async () => (await import("./messages/ru")).ruMessages,
+  ja: async () => (await import("./messages/ja")).jaMessages,
+  "zh-Hans": async () => (await import("./messages/zh-Hans")).zhHansMessages,
 }
 
 function normalizeLocaleTag(value: string): string {
@@ -34,8 +33,7 @@ function matchSupportedLocale(value: string | undefined): Locale | null {
 
   const normalized = normalizeLocaleTag(value)
   const lower = normalized.toLowerCase()
-  const supportedLower = new Map(SUPPORTED_LOCALES.map((locale) => [locale.toLowerCase(), locale]))
-  const exact = supportedLower.get(lower)
+  const exact = SUPPORTED_LOCALES_BY_LOWER.get(lower)
   if (exact) return exact
 
   const parts = lower.split("-")
@@ -43,11 +41,11 @@ function matchSupportedLocale(value: string | undefined): Locale | null {
   if (!base) return null
 
   if (base === "zh") {
-    const zhHans = supportedLower.get("zh-hans")
+    const zhHans = SUPPORTED_LOCALES_BY_LOWER.get("zh-hans")
     return zhHans ?? null
   }
 
-  const baseMatch = supportedLower.get(base)
+  const baseMatch = SUPPORTED_LOCALES_BY_LOWER.get(base)
   return baseMatch ?? null
 }
 
@@ -84,8 +82,54 @@ function translateFrom(messages: Messages, key: string, params?: TranslateParams
 }
 
 const [globalRevision, setGlobalRevision] = createSignal(0)
-const initialGlobalLocale: Locale = detectNavigatorLocale() ?? "en"
-let globalMessages: Messages = messagesByLocale[initialGlobalLocale]
+let globalMessages: Messages = enMessages
+let globalLocale: Locale = "en"
+
+function getMessagesForLocale(locale: Locale): Messages {
+  return localeMessagesCache.get(locale) ?? enMessages
+}
+
+async function loadLocaleMessages(locale: Locale): Promise<Messages> {
+  const cached = localeMessagesCache.get(locale)
+  if (cached) {
+    return cached
+  }
+
+  const pending = localeMessagesPromises.get(locale)
+  if (pending) {
+    return pending
+  }
+
+  const loader = localeLoaders[locale]
+  const promise = loader()
+    .then((messages) => {
+      localeMessagesCache.set(locale, messages)
+      localeMessagesPromises.delete(locale)
+      return messages
+    })
+    .catch((error) => {
+      localeMessagesPromises.delete(locale)
+      throw error
+    })
+
+  localeMessagesPromises.set(locale, promise)
+  return promise
+}
+
+export async function preloadLocaleMessages(preferredLocale?: string | null): Promise<Locale> {
+  const resolvedLocale = matchSupportedLocale(preferredLocale ?? undefined) ?? detectNavigatorLocale() ?? "en"
+  try {
+    globalMessages = await loadLocaleMessages(resolvedLocale)
+    globalLocale = resolvedLocale
+    setGlobalRevision((value) => value + 1)
+    return resolvedLocale
+  } catch {
+    globalMessages = enMessages
+    globalLocale = "en"
+    setGlobalRevision((value) => value + 1)
+    return "en"
+  }
+}
 
 export function tGlobal(key: string, params?: TranslateParams): string {
   globalRevision()
@@ -101,9 +145,10 @@ const I18nContext = createContext<I18nContextValue>()
 
 export const I18nProvider: ParentComponent = (props) => {
   const { preferences } = useConfig()
-  const [detectedLocale, setDetectedLocale] = createSignal<Locale>("en")
-
-  const previousMessages = globalMessages
+  const [detectedLocale, setDetectedLocale] = createSignal<Locale>(globalLocale)
+  const [resolvedLocale, setResolvedLocale] = createSignal<Locale>(globalLocale)
+  const previousGlobalMessages = globalMessages
+  const previousGlobalLocale = globalLocale
 
   onMount(() => {
     const detected = detectNavigatorLocale()
@@ -115,19 +160,44 @@ export const I18nProvider: ParentComponent = (props) => {
     return configured ?? detectedLocale() ?? "en"
   })
 
-  const messages = createMemo<Messages>(() => messagesByLocale[locale()])
+  const messages = createMemo<Messages>(() => getMessagesForLocale(resolvedLocale()))
 
   function t(key: string, params?: TranslateParams): string {
     return translateFrom(messages(), key, params)
   }
 
   createEffect(() => {
-    globalMessages = messages()
-    setGlobalRevision((value) => value + 1)
+    const nextLocale = locale()
+    let cancelled = false
+
+    void loadLocaleMessages(nextLocale)
+      .then((loadedMessages) => {
+        if (cancelled) {
+          return
+        }
+        setResolvedLocale(nextLocale)
+        globalLocale = nextLocale
+        globalMessages = loadedMessages
+        setGlobalRevision((value) => value + 1)
+      })
+      .catch(() => {
+        if (cancelled) {
+          return
+        }
+        setResolvedLocale("en")
+        globalMessages = enMessages
+        globalLocale = "en"
+        setGlobalRevision((value) => value + 1)
+      })
+
+    onCleanup(() => {
+      cancelled = true
+    })
   })
 
   onCleanup(() => {
-    globalMessages = previousMessages
+    globalMessages = previousGlobalMessages
+    globalLocale = previousGlobalLocale
     setGlobalRevision((value) => value + 1)
   })
 

packages/ui/src/main.tsx

@@ -4,7 +4,7 @@ import { ThemeProvider } from "./lib/theme"
 import { ConfigProvider } from "./stores/preferences"
 import { InstanceConfigProvider } from "./stores/instance-config"
 import { runtimeEnv } from "./lib/runtime-env"
-import { I18nProvider } from "./lib/i18n"
+import { I18nProvider, preloadLocaleMessages } from "./lib/i18n"
 import { storage } from "./lib/storage"
 import "./index.css"
 import "@git-diff-view/solid/styles/diff-view-pure.css"
@@ -31,15 +31,19 @@ async function bootstrap() {
 
     try {
       const uiConfig = await storage.loadConfigOwner("ui")
-      const theme = (uiConfig as any)?.theme ?? "system"
+      const theme = (uiConfig as any)?.theme
+      const locale = typeof (uiConfig as any)?.settings?.locale === "string" ? (uiConfig as any).settings.locale : undefined
 
-      if (theme === "system") {
-        document.documentElement.removeAttribute("data-theme")
-      } else {
+      if (theme === "light" || theme === "dark") {
         document.documentElement.setAttribute("data-theme", theme)
+      } else {
+        document.documentElement.removeAttribute("data-theme")
       }
+
+      await preloadLocaleMessages(locale)
     } catch {
       // If config fails to load, fall back to CSS defaults.
+      await preloadLocaleMessages()
     }
   }