fix(frontend): use singleton Shiki highlighter for code syntax highlighting (#12144)

## Summary
Addresses SENTRY-1051: Shiki warning about multiple highlighter
instances.

## Problem
The `@streamdown/code` package creates a **new Shiki highlighter for
each language** encountered. When users view AI chat responses with code
blocks in multiple languages (JavaScript, Python, JSON, YAML, etc.),
this creates 10+ highlighter instances, triggering Shiki's warning:

> "10 instances have been created. Shiki is supposed to be used as a
singleton, consider refactoring your code to cache your highlighter
instance"

This causes memory bloat and performance degradation.

## Solution
Introduced a custom code highlighting plugin that properly implements
the singleton pattern:

### New files:
- `src/lib/shiki-highlighter.ts` - Singleton highlighter management
- `src/lib/streamdown-code-plugin.ts` - Drop-in replacement for
`@streamdown/code`

### Key features:
- **Single shared highlighter** - One instance serves all code blocks
- **Preloaded common languages** - JS, TS, Python, JSON, Bash, YAML,
etc.
- **Lazy loading** - Additional languages loaded on demand
- **Result caching** - Avoids re-highlighting identical code blocks

### Changes:
- Added `shiki` as direct dependency
- Updated `message.tsx` to use the new plugin

## Testing
- [ ] Verify code blocks render correctly in AI chat
- [ ] Confirm no Shiki singleton warnings in console
- [ ] Test with multiple languages in same conversation

## Related
- Linear: SENTRY-1051
- Sentry: Multiple Shiki instances warning

<!-- greptile_comment -->

<details><summary><h3>Greptile Summary</h3></summary>

Replaced `@streamdown/code` with a custom singleton-based Shiki
highlighter implementation to resolve memory bloat from creating
multiple highlighter instances per language. The new implementation
creates a single shared highlighter with preloaded common languages (JS,
TS, Python, JSON, etc.) and lazy-loads additional languages on demand.
Results are cached to avoid re-highlighting identical code blocks.

**Key changes:**
- Added `shiki` v3.21.0 as a direct dependency
- Created `shiki-highlighter.ts` with singleton pattern and language
management utilities
- Created `streamdown-code-plugin.ts` as a drop-in replacement for
`@streamdown/code`
- Updated `message.tsx` to import from the new plugin instead of
`@streamdown/code`

The implementation follows React best practices with async highlighting
and callback-based notifications. The cache key uses code length +
prefix/suffix for efficient lookups on large code blocks.
</details>


<details><summary><h3>Confidence Score: 4/5</h3></summary>

- Safe to merge with minor considerations for edge cases
- The implementation is solid with proper singleton pattern, caching,
and async handling. The code is well-structured and addresses the stated
problem. However, there's a subtle potential race condition in the
callback handling where multiple concurrent requests for the same cache
key could trigger duplicate highlight operations before the first
completes. The cache key generation using prefix/suffix could
theoretically cause false cache hits for large files with identical
prefixes and suffixes. Despite these edge cases, the implementation
should work correctly for the vast majority of use cases.
- No files require special attention
</details>


<details><summary><h3>Sequence Diagram</h3></summary>

```mermaid
sequenceDiagram
    participant UI as Streamdown Component
    participant Plugin as Custom Code Plugin
    participant Cache as Token Cache
    participant Singleton as Shiki Highlighter (Singleton)
    participant Callbacks as Pending Callbacks

    UI->>Plugin: highlight(code, lang)
    Plugin->>Cache: Check cache key
    
    alt Cache hit
        Cache-->>Plugin: Return cached result
        Plugin-->>UI: Return highlighted tokens
    else Cache miss
        Plugin->>Callbacks: Register callback
        Plugin->>Singleton: Get highlighter instance
        
        alt First call
            Singleton->>Singleton: Create highlighter with preloaded languages
        end
        
        Singleton-->>Plugin: Return highlighter
        
        alt Language not loaded
            Plugin->>Singleton: Load language dynamically
        end
        
        Plugin->>Singleton: codeToTokens(code, lang, themes)
        Singleton-->>Plugin: Return tokens
        Plugin->>Cache: Store result
        Plugin->>Callbacks: Notify all waiting callbacks
        Callbacks-->>UI: Async callback with result
    end
```
</details>


<sub>Last reviewed commit: 96c793b</sub>

<!-- greptile_other_comments_section -->

<!-- /greptile_comment -->

autogpt_platform/backend/backend/api/features/chat/tools/feature_requests.py

@@ -104,8 +104,8 @@ def _get_linear_config() -> tuple[LinearClient, str, str]:
     Raises RuntimeError if any required setting is missing.
     """
     secrets = _get_settings().secrets
-    if not secrets.linear_api_key:
-        raise RuntimeError("LINEAR_API_KEY is not configured")
+    if not secrets.copilot_linear_api_key:
+        raise RuntimeError("COPILOT_LINEAR_API_KEY is not configured")
     if not secrets.linear_feature_request_project_id:
         raise RuntimeError("LINEAR_FEATURE_REQUEST_PROJECT_ID is not configured")
     if not secrets.linear_feature_request_team_id:
@@ -114,7 +114,7 @@ def _get_linear_config() -> tuple[LinearClient, str, str]:
     credentials = APIKeyCredentials(
         id="system-linear",
         provider="linear",
-        api_key=SecretStr(secrets.linear_api_key),
+        api_key=SecretStr(secrets.copilot_linear_api_key),
         title="System Linear API Key",
     )
     client = LinearClient(credentials=credentials)

autogpt_platform/backend/backend/util/settings.py

@@ -662,7 +662,7 @@ class Secrets(UpdateTrackingModel["Secrets"], BaseSettings):
     mem0_api_key: str = Field(default="", description="Mem0 API key")
     elevenlabs_api_key: str = Field(default="", description="ElevenLabs API key")
 
-    linear_api_key: str = Field(
+    copilot_linear_api_key: str = Field(
         default="", description="Linear API key for system-level operations"
     )
     linear_feature_request_project_id: str = Field(

autogpt_platform/frontend/package.json

@@ -62,7 +62,6 @@
     "@rjsf/validator-ajv8": "6.1.2",
     "@sentry/nextjs": "10.27.0",
     "@streamdown/cjk": "1.0.1",
-    "@streamdown/code": "1.0.1",
     "@streamdown/math": "1.0.1",
     "@streamdown/mermaid": "1.0.1",
     "@supabase/ssr": "0.7.0",
@@ -116,6 +115,7 @@
     "remark-gfm": "4.0.1",
     "remark-math": "6.0.0",
     "shepherd.js": "14.5.1",
+    "shiki": "^3.21.0",
     "sonner": "2.0.7",
     "streamdown": "2.1.0",
     "tailwind-merge": "2.6.0",

autogpt_platform/frontend/pnpm-lock.yaml

@@ -108,9 +108,6 @@ importers:
       '@streamdown/cjk':
         specifier: 1.0.1
         version: 1.0.1(@types/mdast@4.0.4)(micromark-util-types@2.0.2)(micromark@4.0.2)(react@18.3.1)(unified@11.0.5)
-      '@streamdown/code':
-        specifier: 1.0.1
-        version: 1.0.1(react@18.3.1)
       '@streamdown/math':
         specifier: 1.0.1
         version: 1.0.1(react@18.3.1)
@@ -270,6 +267,9 @@ importers:
       shepherd.js:
         specifier: 14.5.1
         version: 14.5.1
+      shiki:
+        specifier: ^3.21.0
+        version: 3.21.0
       sonner:
         specifier: 2.0.7
         version: 2.0.7(react-dom@18.3.1(react@18.3.1))(react@18.3.1)
@@ -3307,11 +3307,6 @@ packages:
     peerDependencies:
       react: ^18.0.0 || ^19.0.0
 
-  '@streamdown/code@1.0.1':
-    resolution: {integrity: sha512-U9LITfQ28tZYAoY922jdtw1ryg4kgRBdURopqK9hph7G2fBUwPeHthjH7SvaV0fvFv7EqjqCzARJuWUljLe9Ag==}
-    peerDependencies:
-      react: ^18.0.0 || ^19.0.0
-
   '@streamdown/math@1.0.1':
     resolution: {integrity: sha512-R9WdHbpERiRU7WeO7oT1aIbnLJ/jraDr89F7X9x2OM//Y8G8UMATRnLD/RUwg4VLr8Nu7QSIJ0Pa8lXd2meM4Q==}
     peerDependencies:
@@ -11907,11 +11902,6 @@ snapshots:
       - micromark-util-types
       - unified
 
-  '@streamdown/code@1.0.1(react@18.3.1)':
-    dependencies:
-      react: 18.3.1
-      shiki: 3.21.0
-
   '@streamdown/math@1.0.1(react@18.3.1)':
     dependencies:
       katex: 0.16.28

autogpt_platform/frontend/src/app/(platform)/copilot/CopilotPage.tsx

@@ -1,10 +1,16 @@
 "use client";
 
+import {
+  DropdownMenu,
+  DropdownMenuContent,
+  DropdownMenuItem,
+  DropdownMenuTrigger,
+} from "@/components/molecules/DropdownMenu/DropdownMenu";
 import { SidebarProvider } from "@/components/ui/sidebar";
-// TODO: Replace with modern Dialog component when available
-import DeleteConfirmDialog from "@/components/__legacy__/delete-confirm-dialog";
+import { DotsThree } from "@phosphor-icons/react";
 import { ChatContainer } from "./components/ChatContainer/ChatContainer";
 import { ChatSidebar } from "./components/ChatSidebar/ChatSidebar";
+import { DeleteChatDialog } from "./components/DeleteChatDialog/DeleteChatDialog";
 import { MobileDrawer } from "./components/MobileDrawer/MobileDrawer";
 import { MobileHeader } from "./components/MobileHeader/MobileHeader";
 import { ScaleLoader } from "./components/ScaleLoader/ScaleLoader";
@@ -56,19 +62,7 @@ export function CopilotPage() {
     >
       {!isMobile && <ChatSidebar />}
       <div className="relative flex h-full w-full flex-col overflow-hidden bg-[#f8f8f9] px-0">
-        {isMobile && (
-          <MobileHeader
-            onOpenDrawer={handleOpenDrawer}
-            showDelete={!!sessionId}
-            isDeleting={isDeleting}
-            onDelete={() => {
-              const session = sessions.find((s) => s.id === sessionId);
-              if (session) {
-                handleDeleteClick(session.id, session.title);
-              }
-            }}
-          />
-        )}
+        {isMobile && <MobileHeader onOpenDrawer={handleOpenDrawer} />}
         <div className="flex-1 overflow-hidden">
           <ChatContainer
             messages={messages}
@@ -80,6 +74,38 @@ export function CopilotPage() {
             onCreateSession={createSession}
             onSend={onSend}
             onStop={stop}
+            headerSlot={
+              isMobile && sessionId ? (
+                <div className="flex justify-end">
+                  <DropdownMenu>
+                    <DropdownMenuTrigger asChild>
+                      <button
+                        className="rounded p-1.5 hover:bg-neutral-100"
+                        aria-label="More actions"
+                      >
+                        <DotsThree className="h-5 w-5 text-neutral-600" />
+                      </button>
+                    </DropdownMenuTrigger>
+                    <DropdownMenuContent align="end">
+                      <DropdownMenuItem
+                        onClick={() => {
+                          const session = sessions.find(
+                            (s) => s.id === sessionId,
+                          );
+                          if (session) {
+                            handleDeleteClick(session.id, session.title);
+                          }
+                        }}
+                        disabled={isDeleting}
+                        className="text-red-600 focus:bg-red-50 focus:text-red-600"
+                      >
+                        Delete chat
+                      </DropdownMenuItem>
+                    </DropdownMenuContent>
+                  </DropdownMenu>
+                </div>
+              ) : undefined
+            }
           />
         </div>
       </div>
@@ -97,12 +123,11 @@ export function CopilotPage() {
       )}
       {/* Delete confirmation dialog - rendered at top level for proper z-index on mobile */}
       {isMobile && (
-        <DeleteConfirmDialog
-          entityType="chat"
-          entityName={sessionToDelete?.title || "Untitled chat"}
-          open={!!sessionToDelete}
-          onOpenChange={(open) => !open && handleCancelDelete()}
-          onDoDelete={handleConfirmDelete}
+        <DeleteChatDialog
+          session={sessionToDelete}
+          isDeleting={isDeleting}
+          onConfirm={handleConfirmDelete}
+          onCancel={handleCancelDelete}
         />
       )}
     </SidebarProvider>

autogpt_platform/frontend/src/app/(platform)/copilot/components/ChatContainer/ChatContainer.tsx

@@ -2,6 +2,7 @@
 import { ChatInput } from "@/app/(platform)/copilot/components/ChatInput/ChatInput";
 import { UIDataTypes, UIMessage, UITools } from "ai";
 import { LayoutGroup, motion } from "framer-motion";
+import { ReactNode } from "react";
 import { ChatMessagesContainer } from "../ChatMessagesContainer/ChatMessagesContainer";
 import { CopilotChatActionsProvider } from "../CopilotChatActionsProvider/CopilotChatActionsProvider";
 import { EmptySession } from "../EmptySession/EmptySession";
@@ -16,6 +17,7 @@ export interface ChatContainerProps {
   onCreateSession: () => void | Promise<string>;
   onSend: (message: string) => void | Promise<void>;
   onStop: () => void;
+  headerSlot?: ReactNode;
 }
 export const ChatContainer = ({
   messages,
@@ -27,6 +29,7 @@ export const ChatContainer = ({
   onCreateSession,
   onSend,
   onStop,
+  headerSlot,
 }: ChatContainerProps) => {
   const inputLayoutId = "copilot-2-chat-input";
 
@@ -41,6 +44,7 @@ export const ChatContainer = ({
                 status={status}
                 error={error}
                 isLoading={isLoadingSession}
+                headerSlot={headerSlot}
               />
               <motion.div
                 initial={{ opacity: 0 }}

autogpt_platform/frontend/src/app/(platform)/copilot/components/ChatMessagesContainer/ChatMessagesContainer.tsx

@@ -118,6 +118,7 @@ interface ChatMessagesContainerProps {
   status: string;
   error: Error | undefined;
   isLoading: boolean;
+  headerSlot?: React.ReactNode;
 }
 
 export const ChatMessagesContainer = ({
@@ -125,6 +126,7 @@ export const ChatMessagesContainer = ({
   status,
   error,
   isLoading,
+  headerSlot,
 }: ChatMessagesContainerProps) => {
   const [thinkingPhrase, setThinkingPhrase] = useState(getRandomPhrase);
   const lastToastTimeRef = useRef(0);
@@ -165,6 +167,7 @@ export const ChatMessagesContainer = ({
   return (
     <Conversation className="min-h-0 flex-1">
       <ConversationContent className="flex flex-1 flex-col gap-6 px-3 py-6">
+        {headerSlot}
         {isLoading && messages.length === 0 && (
           <div className="flex min-h-full flex-1 items-center justify-center">
             <LoadingSpinner className="text-neutral-600" />

autogpt_platform/frontend/src/app/(platform)/copilot/components/ChatSidebar/ChatSidebar.tsx

@@ -7,9 +7,13 @@ import {
 import { Button } from "@/components/atoms/Button/Button";
 import { LoadingSpinner } from "@/components/atoms/LoadingSpinner/LoadingSpinner";
 import { Text } from "@/components/atoms/Text/Text";
+import {
+  DropdownMenu,
+  DropdownMenuContent,
+  DropdownMenuItem,
+  DropdownMenuTrigger,
+} from "@/components/molecules/DropdownMenu/DropdownMenu";
 import { toast } from "@/components/molecules/Toast/use-toast";
-// TODO: Replace with modern Dialog component when available
-import DeleteConfirmDialog from "@/components/__legacy__/delete-confirm-dialog";
 import {
   Sidebar,
   SidebarContent,
@@ -19,11 +23,12 @@ import {
   useSidebar,
 } from "@/components/ui/sidebar";
 import { cn } from "@/lib/utils";
-import { PlusCircleIcon, PlusIcon, TrashIcon } from "@phosphor-icons/react";
+import { DotsThree, PlusCircleIcon, PlusIcon } from "@phosphor-icons/react";
 import { useQueryClient } from "@tanstack/react-query";
 import { motion } from "framer-motion";
-import { useState } from "react";
 import { parseAsString, useQueryState } from "nuqs";
+import { useState } from "react";
+import { DeleteChatDialog } from "../DeleteChatDialog/DeleteChatDialog";
 
 export function ChatSidebar() {
   const { state } = useSidebar();
@@ -92,6 +97,12 @@ export function ChatSidebar() {
     }
   }
 
+  function handleCancelDelete() {
+    if (!isDeleting) {
+      setSessionToDelete(null);
+    }
+  }
+
   function formatDate(dateString: string) {
     const date = new Date(dateString);
     const now = new Date();
@@ -220,16 +231,28 @@ export function ChatSidebar() {
                         </Text>
                       </div>
                     </button>
-                    <button
-                      onClick={(e) =>
-                        handleDeleteClick(e, session.id, session.title)
-                      }
-                      disabled={isDeleting}
-                      className="absolute right-2 top-1/2 -translate-y-1/2 rounded p-1.5 text-zinc-400 opacity-0 transition-all group-hover:opacity-100 hover:bg-red-100 hover:text-red-600 focus-visible:opacity-100 disabled:cursor-not-allowed disabled:opacity-50"
-                      aria-label="Delete chat"
-                    >
-                      <TrashIcon className="h-4 w-4" />
-                    </button>
+                    <DropdownMenu>
+                      <DropdownMenuTrigger asChild>
+                        <button
+                          onClick={(e) => e.stopPropagation()}
+                          className="absolute right-2 top-1/2 -translate-y-1/2 rounded-full p-1.5 text-zinc-600 transition-all hover:bg-neutral-100"
+                          aria-label="More actions"
+                        >
+                          <DotsThree className="h-4 w-4" />
+                        </button>
+                      </DropdownMenuTrigger>
+                      <DropdownMenuContent align="end">
+                        <DropdownMenuItem
+                          onClick={(e) =>
+                            handleDeleteClick(e, session.id, session.title)
+                          }
+                          disabled={isDeleting}
+                          className="text-red-600 focus:bg-red-50 focus:text-red-600"
+                        >
+                          Delete chat
+                        </DropdownMenuItem>
+                      </DropdownMenuContent>
+                    </DropdownMenu>
                   </div>
                 ))
               )}
@@ -257,12 +280,11 @@ export function ChatSidebar() {
         )}
       </Sidebar>
 
-      <DeleteConfirmDialog
-        entityType="chat"
-        entityName={sessionToDelete?.title || "Untitled chat"}
-        open={!!sessionToDelete}
-        onOpenChange={(open) => !open && setSessionToDelete(null)}
-        onDoDelete={handleConfirmDelete}
+      <DeleteChatDialog
+        session={sessionToDelete}
+        isDeleting={isDeleting}
+        onConfirm={handleConfirmDelete}
+        onCancel={handleCancelDelete}
       />
     </>
   );

autogpt_platform/frontend/src/app/(platform)/copilot/components/DeleteChatDialog/DeleteChatDialog.tsx

@@ -0,0 +1,57 @@
+"use client";
+
+import { Button } from "@/components/atoms/Button/Button";
+import { Text } from "@/components/atoms/Text/Text";
+import { Dialog } from "@/components/molecules/Dialog/Dialog";
+
+interface Props {
+  session: { id: string; title: string | null | undefined } | null;
+  isDeleting: boolean;
+  onConfirm: () => void;
+  onCancel: () => void;
+}
+
+export function DeleteChatDialog({
+  session,
+  isDeleting,
+  onConfirm,
+  onCancel,
+}: Props) {
+  return (
+    <Dialog
+      title="Delete chat"
+      styling={{ maxWidth: "30rem", minWidth: "auto" }}
+      controlled={{
+        isOpen: !!session,
+        set: async (open) => {
+          if (!open && !isDeleting) {
+            onCancel();
+          }
+        },
+      }}
+      onClose={isDeleting ? undefined : onCancel}
+    >
+      <Dialog.Content>
+        <Text variant="body">
+          Are you sure you want to delete{" "}
+          <Text variant="body-medium" as="span">
+            &quot;{session?.title || "Untitled chat"}&quot;
+          </Text>
+          ? This action cannot be undone.
+        </Text>
+        <Dialog.Footer>
+          <Button variant="secondary" onClick={onCancel} disabled={isDeleting}>
+            Cancel
+          </Button>
+          <Button
+            variant="destructive"
+            onClick={onConfirm}
+            loading={isDeleting}
+          >
+            Delete
+          </Button>
+        </Dialog.Footer>
+      </Dialog.Content>
+    </Dialog>
+  );
+}

autogpt_platform/frontend/src/app/(platform)/copilot/components/MobileHeader/MobileHeader.tsx

@@ -1,20 +1,12 @@
 import { Button } from "@/components/atoms/Button/Button";
 import { NAVBAR_HEIGHT_PX } from "@/lib/constants";
-import { ListIcon, TrashIcon } from "@phosphor-icons/react";
+import { ListIcon } from "@phosphor-icons/react";
 
 interface Props {
   onOpenDrawer: () => void;
-  showDelete?: boolean;
-  isDeleting?: boolean;
-  onDelete?: () => void;
 }
 
-export function MobileHeader({
-  onOpenDrawer,
-  showDelete,
-  isDeleting,
-  onDelete,
-}: Props) {
+export function MobileHeader({ onOpenDrawer }: Props) {
   return (
     <div
       className="fixed z-50 flex gap-2"
@@ -29,18 +21,6 @@ export function MobileHeader({
       >
         <ListIcon width="1.25rem" height="1.25rem" />
       </Button>
-      {showDelete && onDelete && (
-        <Button
-          variant="icon"
-          size="icon"
-          aria-label="Delete current chat"
-          onClick={onDelete}
-          disabled={isDeleting}
-          className="bg-white text-red-500 shadow-md hover:bg-red-50 hover:text-red-600 disabled:opacity-50"
-        >
-          <TrashIcon width="1.25rem" height="1.25rem" />
-        </Button>
-      )}
     </div>
   );
 }

autogpt_platform/frontend/src/app/(platform)/copilot/useCopilotPage.ts

@@ -192,8 +192,10 @@ export function useCopilotPage() {
   }, [sessionToDelete, deleteSessionMutation]);
 
   const handleCancelDelete = useCallback(() => {
-    setSessionToDelete(null);
-  }, []);
+    if (!isDeleting) {
+      setSessionToDelete(null);
+    }
+  }, [isDeleting]);
 
   return {
     sessionId,

autogpt_platform/frontend/src/components/ai-elements/message.tsx

@@ -10,7 +10,7 @@ import {
 } from "@/components/ui/tooltip";
 import { cn } from "@/lib/utils";
 import { cjk } from "@streamdown/cjk";
-import { code } from "@streamdown/code";
+import { code } from "@/lib/streamdown-code-plugin";
 import { math } from "@streamdown/math";
 import { mermaid } from "@streamdown/mermaid";
 import type { UIMessage } from "ai";

autogpt_platform/frontend/src/components/molecules/Dialog/components/BaseFooter.tsx

@@ -25,7 +25,7 @@ export function BaseFooter({
     </div>
   ) : (
     <div
-      className={`flex w-full items-end justify-between gap-4 pt-6 ${className}`}
+      className={`flex w-full items-end justify-end gap-4 pt-6 ${className}`}
       data-testid={testId}
     >
       {children}

autogpt_platform/frontend/src/lib/shiki-highlighter.ts

@@ -0,0 +1,70 @@
+import {
+  bundledLanguages,
+  bundledLanguagesInfo,
+  createHighlighter,
+  type BundledLanguage,
+  type BundledTheme,
+  type HighlighterGeneric,
+} from "shiki";
+
+export type { BundledLanguage, BundledTheme };
+
+const LANGUAGE_ALIASES: Record<string, string> = Object.fromEntries(
+  bundledLanguagesInfo.flatMap((lang) =>
+    (lang.aliases ?? []).map((alias) => [alias, lang.id]),
+  ),
+);
+
+const SUPPORTED_LANGUAGES = new Set(Object.keys(bundledLanguages));
+
+const PRELOAD_LANGUAGES: BundledLanguage[] = [
+  "javascript",
+  "typescript",
+  "python",
+  "json",
+  "bash",
+  "yaml",
+  "markdown",
+  "html",
+  "css",
+  "sql",
+  "tsx",
+  "jsx",
+];
+
+export const SHIKI_THEMES: [BundledTheme, BundledTheme] = [
+  "github-light",
+  "github-dark",
+];
+
+let highlighterPromise: Promise<
+  HighlighterGeneric<BundledLanguage, BundledTheme>
+> | null = null;
+
+export function getShikiHighlighter(): Promise<
+  HighlighterGeneric<BundledLanguage, BundledTheme>
+> {
+  if (!highlighterPromise) {
+    highlighterPromise = createHighlighter({
+      themes: SHIKI_THEMES,
+      langs: PRELOAD_LANGUAGES,
+    }).catch((err) => {
+      highlighterPromise = null;
+      throw err;
+    });
+  }
+  return highlighterPromise;
+}
+
+export function resolveLanguage(lang: string): string {
+  const normalized = lang.trim().toLowerCase();
+  return LANGUAGE_ALIASES[normalized] ?? normalized;
+}
+
+export function isLanguageSupported(lang: string): boolean {
+  return SUPPORTED_LANGUAGES.has(resolveLanguage(lang));
+}
+
+export function getSupportedLanguages(): BundledLanguage[] {
+  return Array.from(SUPPORTED_LANGUAGES) as BundledLanguage[];
+}

autogpt_platform/frontend/src/lib/streamdown-code-plugin.ts

@@ -0,0 +1,159 @@
+import type { CodeHighlighterPlugin } from "streamdown";
+
+import {
+  type BundledLanguage,
+  type BundledTheme,
+  getShikiHighlighter,
+  getSupportedLanguages,
+  isLanguageSupported,
+  resolveLanguage,
+  SHIKI_THEMES,
+} from "./shiki-highlighter";
+
+interface HighlightResult {
+  tokens: {
+    content: string;
+    color?: string;
+    htmlStyle?: Record<string, string>;
+  }[][];
+  fg?: string;
+  bg?: string;
+}
+
+type HighlightCallback = (result: HighlightResult) => void;
+
+const MAX_CACHE_SIZE = 500;
+const tokenCache = new Map<string, HighlightResult>();
+const pendingCallbacks = new Map<string, Set<HighlightCallback>>();
+const inFlightLanguageLoads = new Map<string, Promise<void>>();
+
+function simpleHash(str: string): string {
+  let hash = 0;
+  for (let i = 0; i < str.length; i++) {
+    const char = str.charCodeAt(i);
+    hash = (hash << 5) - hash + char;
+    hash = hash & hash;
+  }
+  return hash.toString(36);
+}
+
+function getCacheKey(
+  code: string,
+  lang: string,
+  themes: readonly string[],
+): string {
+  return `${lang}:${themes.join(",")}:${simpleHash(code)}`;
+}
+
+function evictOldestIfNeeded(): void {
+  if (tokenCache.size > MAX_CACHE_SIZE) {
+    const oldestKey = tokenCache.keys().next().value;
+    if (oldestKey) {
+      tokenCache.delete(oldestKey);
+    }
+  }
+}
+
+export function createSingletonCodePlugin(): CodeHighlighterPlugin {
+  return {
+    name: "shiki",
+    type: "code-highlighter",
+
+    supportsLanguage(lang: BundledLanguage): boolean {
+      return isLanguageSupported(lang);
+    },
+
+    getSupportedLanguages(): BundledLanguage[] {
+      return getSupportedLanguages();
+    },
+
+    getThemes(): [BundledTheme, BundledTheme] {
+      return SHIKI_THEMES;
+    },
+
+    highlight({ code, language, themes }, callback) {
+      const lang = resolveLanguage(language);
+      const cacheKey = getCacheKey(code, lang, themes);
+
+      if (tokenCache.has(cacheKey)) {
+        return tokenCache.get(cacheKey)!;
+      }
+
+      if (callback) {
+        if (!pendingCallbacks.has(cacheKey)) {
+          pendingCallbacks.set(cacheKey, new Set());
+        }
+        pendingCallbacks.get(cacheKey)!.add(callback);
+      }
+
+      getShikiHighlighter()
+        .then(async (highlighter) => {
+          const loadedLanguages = highlighter.getLoadedLanguages();
+
+          if (!loadedLanguages.includes(lang) && isLanguageSupported(lang)) {
+            let loadPromise = inFlightLanguageLoads.get(lang);
+            if (!loadPromise) {
+              loadPromise = highlighter
+                .loadLanguage(lang as BundledLanguage)
+                .finally(() => {
+                  inFlightLanguageLoads.delete(lang);
+                });
+              inFlightLanguageLoads.set(lang, loadPromise);
+            }
+            await loadPromise;
+          }
+
+          const finalLang = (
+            highlighter.getLoadedLanguages().includes(lang) ? lang : "text"
+          ) as BundledLanguage;
+
+          const shikiResult = highlighter.codeToTokens(code, {
+            lang: finalLang,
+            themes: { light: themes[0], dark: themes[1] },
+          });
+
+          const result: HighlightResult = {
+            tokens: shikiResult.tokens.map((line) =>
+              line.map((token) => ({
+                content: token.content,
+                color: token.color,
+                htmlStyle: token.htmlStyle,
+              })),
+            ),
+            fg: shikiResult.fg,
+            bg: shikiResult.bg,
+          };
+
+          evictOldestIfNeeded();
+          tokenCache.set(cacheKey, result);
+
+          const callbacks = pendingCallbacks.get(cacheKey);
+          if (callbacks) {
+            callbacks.forEach((cb) => {
+              cb(result);
+            });
+            pendingCallbacks.delete(cacheKey);
+          }
+        })
+        .catch((error) => {
+          console.error("[Shiki] Failed to highlight code:", error);
+
+          const fallback: HighlightResult = {
+            tokens: code.split("\n").map((line) => [{ content: line }]),
+          };
+
+          const callbacks = pendingCallbacks.get(cacheKey);
+          if (callbacks) {
+            callbacks.forEach((cb) => {
+              cb(fallback);
+            });
+            pendingCallbacks.delete(cacheKey);
+          }
+        });
+
+      return null;
+    },
+  };
+}
+
+export const code = createSingletonCodePlugin();

autogpt_platform/frontend/src/tests/pages/library.page.ts

@@ -465,9 +465,13 @@ export async function navigateToAgentByName(
 export async function clickRunButton(page: Page): Promise<void> {
   const { getId } = getSelectors(page);
 
-  // Wait for page to stabilize and buttons to render
-  // The NewAgentLibraryView shows either "Setup your task" (empty state)
-  // or "New task" (with items) button
+  // Wait for sidebar loading to complete before detecting buttons.
+  // During sidebar loading, the "New task" button appears transiently
+  // even for agents with no items, then switches to "Setup your task"
+  // once loading finishes. Waiting for network idle ensures the page
+  // has settled into its final state.
+  await page.waitForLoadState("networkidle");
+
   const setupTaskButton = page.getByRole("button", {
     name: /Setup your task/i,
   });
@@ -475,8 +479,7 @@ export async function clickRunButton(page: Page): Promise<void> {
   const runButton = getId("agent-run-button");
   const runAgainButton = getId("run-again-button");
 
-  // Use Promise.race with waitFor to wait for any of the buttons to appear
-  // This handles the async rendering in CI environments
+  // Wait for any of the buttons to appear
   try {
     await Promise.race([
       setupTaskButton.waitFor({ state: "visible", timeout: 15000 }),
@@ -490,7 +493,7 @@ export async function clickRunButton(page: Page): Promise<void> {
     );
   }
 
-  // Now check which button is visible and click it
+  // Check which button is visible and click it
   if (await setupTaskButton.isVisible()) {
     await setupTaskButton.click();
     const startTaskButton = page
@@ -534,7 +537,9 @@ export async function runAgent(page: Page): Promise<void> {
 
 export async function waitForAgentPageLoad(page: Page): Promise<void> {
   await page.waitForURL(/.*\/library\/agents\/[^/]+/);
-  await page.getByTestId("Run actions").isVisible({ timeout: 10000 });
+  // Wait for sidebar data to finish loading so the page settles
+  // into its final state (empty view vs sidebar view)
+  await page.waitForLoadState("networkidle");
 }
 
 export async function getAgentName(page: Page): Promise<string> {