diff --git a/packages/ui/src/components/instance/shell/right-panel/tabs/FilesTab.tsx b/packages/ui/src/components/instance/shell/right-panel/tabs/FilesTab.tsx
index dc462474..f9f949ce 100644
--- a/packages/ui/src/components/instance/shell/right-panel/tabs/FilesTab.tsx
+++ b/packages/ui/src/components/instance/shell/right-panel/tabs/FilesTab.tsx
@@ -1,12 +1,14 @@
-import { For, Show, type Accessor, type Component, type JSX } from "solid-js"
+import { For, Show, Suspense, lazy, type Accessor, type Component, type JSX } from "solid-js"
 import type { FileNode } from "@opencode-ai/sdk/v2/client"
 
 import { RefreshCw } from "lucide-solid"
 
-import { MonacoFileViewer } from "../../../../file-viewer/monaco-file-viewer"
-
 import SplitFilePanel from "../components/SplitFilePanel"
 
+const LazyMonacoFileViewer = lazy(() =>
+  import("../../../../file-viewer/monaco-file-viewer").then((module) => ({ default: module.MonacoFileViewer })),
+)
+
 interface FilesTabProps {
   t: (key: string, vars?: Record<string, any>) => string
 
@@ -51,8 +53,8 @@ const FilesTab: Component<FilesTabProps> = (props) => {
     const headerDisplayedPath = () => props.browserSelectedPath() || props.browserPath()
 
     const emptyViewerMessage = () => {
-      if (props.browserLoading() && entriesValue === null) return "Loading files..."
-      return "Select a file to preview"
+      if (props.browserLoading() && entriesValue === null) return props.t("instanceInfo.loading")
+      return props.t("instanceShell.filesShell.viewerEmpty")
     }
 
     const renderViewer = () => (
@@ -77,7 +79,9 @@ const FilesTab: Component<FilesTabProps> = (props) => {
                     }
                   >
                     {(payload) => (
-                      <MonacoFileViewer scopeKey={props.scopeKey()} path={payload().path} content={payload().content} />
+                      <Suspense fallback={<div class="file-viewer-empty"><span class="file-viewer-empty-text">{props.t("instanceInfo.loading")}</span></div>}>
+                        <LazyMonacoFileViewer scopeKey={props.scopeKey()} path={payload().path} content={payload().content} />
+                      </Suspense>
                     )}
                   </Show>
                 }
@@ -91,7 +95,7 @@ const FilesTab: Component<FilesTabProps> = (props) => {
             }
           >
             <div class="file-viewer-empty">
-              <span class="file-viewer-empty-text">Loading…</span>
+              <span class="file-viewer-empty-text">{props.t("instanceInfo.loading")}</span>
             </div>
           </Show>
         </div>
@@ -113,7 +117,7 @@ const FilesTab: Component<FilesTabProps> = (props) => {
         </Show>
 
         <Show when={props.browserLoading() && entriesValue === null}>
-          <div class="p-3 text-xs text-secondary">Loading files...</div>
+          <div class="p-3 text-xs text-secondary">{props.t("instanceInfo.loading")}</div>
         </Show>
 
         <For each={sorted}>
@@ -154,7 +158,7 @@ const FilesTab: Component<FilesTabProps> = (props) => {
                 </span>
               </span>
               <Show when={props.browserLoading()}>
-                <span>Loading…</span>
+                <span>{props.t("instanceInfo.loading")}</span>
               </Show>
               <Show when={props.browserError()}>{(err) => <span class="text-error">{err()}</span>}</Show>
             </div>
@@ -180,7 +184,7 @@ const FilesTab: Component<FilesTabProps> = (props) => {
         onResizeMouseDown={props.onResizeMouseDown}
         onResizeTouchStart={props.onResizeTouchStart}
         isPhoneLayout={props.isPhoneLayout()}
-        overlayAriaLabel="Files"
+        overlayAriaLabel={props.t("instanceShell.rightPanel.tabs.files")}
       />
     )
   }
diff --git a/packages/ui/src/components/instance/shell/right-panel/tabs/GitChangesTab.tsx b/packages/ui/src/components/instance/shell/right-panel/tabs/GitChangesTab.tsx
index b2ab7ff4..c22a5231 100644
--- a/packages/ui/src/components/instance/shell/right-panel/tabs/GitChangesTab.tsx
+++ b/packages/ui/src/components/instance/shell/right-panel/tabs/GitChangesTab.tsx
@@ -1,14 +1,16 @@
-import { For, Show, createMemo, type Accessor, type Component, type JSX } from "solid-js"
+import { For, Show, Suspense, createMemo, lazy, type Accessor, type Component, type JSX } from "solid-js"
 import type { File as GitFileStatus } from "@opencode-ai/sdk/v2/client"
 
 import { RefreshCw } from "lucide-solid"
 
-import { MonacoDiffViewer } from "../../../../file-viewer/monaco-diff-viewer"
-
 import DiffToolbar from "../components/DiffToolbar"
 import SplitFilePanel from "../components/SplitFilePanel"
 import type { DiffContextMode, DiffViewMode, DiffWordWrapMode } from "../types"
 
+const LazyMonacoDiffViewer = lazy(() =>
+  import("../../../../file-viewer/monaco-diff-viewer").then((module) => ({ default: module.MonacoDiffViewer })),
+)
+
 interface GitChangesTabProps {
   t: (key: string, vars?: Record<string, any>) => string
 
@@ -80,11 +82,11 @@ const GitChangesTab: Component<GitChangesTabProps> = (props) => {
   })
 
   const emptyViewerMessage = createMemo(() => {
-    if (!hasSession()) return "Select a session to view changes."
+    if (!hasSession()) return props.t("instanceShell.sessionChanges.noSessionSelected")
     const currentEntries = entries()
-    if (currentEntries === null) return "Loading git changes…"
-    if (nonDeleted().length === 0) return "No git changes yet."
-    return "No file selected."
+    if (currentEntries === null) return props.t("instanceShell.sessionChanges.loading")
+    if (nonDeleted().length === 0) return props.t("instanceShell.sessionChanges.empty")
+    return props.t("instanceShell.filesShell.viewerEmpty")
   })
 
   const renderContent = (): JSX.Element => {
@@ -122,7 +124,8 @@ const GitChangesTab: Component<GitChangesTabProps> = (props) => {
                     }
                   >
                     {(file) => (
-                        <MonacoDiffViewer
+                      <Suspense fallback={<div class="file-viewer-empty"><span class="file-viewer-empty-text">{props.t("instanceShell.sessionChanges.loading")}</span></div>}>
+                        <LazyMonacoDiffViewer
                           scopeKey={props.scopeKey()}
                           path={String(file().path || "")}
                           before={String((file() as any).before || "")}
@@ -131,7 +134,8 @@ const GitChangesTab: Component<GitChangesTabProps> = (props) => {
                           contextMode={props.diffContextMode()}
                           wordWrap={props.diffWordWrapMode()}
                         />
-                      )}
+                      </Suspense>
+                    )}
                   </Show>
                 }
               >
@@ -144,7 +148,7 @@ const GitChangesTab: Component<GitChangesTabProps> = (props) => {
             }
           >
             <div class="file-viewer-empty">
-              <span class="file-viewer-empty-text">Loading…</span>
+              <span class="file-viewer-empty-text">{props.t("instanceInfo.loading")}</span>
             </div>
           </Show>
         </div>
@@ -220,8 +224,8 @@ const GitChangesTab: Component<GitChangesTabProps> = (props) => {
           <SplitFilePanel
             header={
               <>
-                <span class="files-tab-selected-path" title={selected?.path || "Git Changes"}>
-                  <span class="file-path-text">{selected?.path || "Git Changes"}</span>
+                <span class="files-tab-selected-path" title={selected?.path || props.t("instanceShell.rightPanel.tabs.gitChanges")}>
+                  <span class="file-path-text">{selected?.path || props.t("instanceShell.rightPanel.tabs.gitChanges")}</span>
                 </span>
 
             <div class="files-tab-stats" style={{ flex: "0 0 auto" }}>
diff --git a/packages/ui/src/lib/git-diff-lowlight.ts b/packages/ui/src/lib/git-diff-lowlight.ts
index e998e3a9..20b0c418 100644
--- a/packages/ui/src/lib/git-diff-lowlight.ts
+++ b/packages/ui/src/lib/git-diff-lowlight.ts
@@ -171,7 +171,7 @@ export const highlighter = {
     ignoreSyntaxHighlightList.push(...values)
   },
   getAST(raw: string, fileName?: string, lang?: string) {
-    const language = String(lang || "plaintext")
+    const language = typeof lang === "string" ? lang.trim() : ""
     if (
       fileName &&
       ignoreSyntaxHighlightList.some((item) => (item instanceof RegExp ? item.test(fileName) : fileName === item))
@@ -179,7 +179,7 @@ export const highlighter = {
       return undefined
     }
 
-    if (lowlight.registered(language)) {
+    if (language && lowlight.registered(language)) {
       return lowlight.highlight(language, raw)
     }