chore: import upstream snapshot with attribution

showcase/integrations/langgraph-fastapi/src/app/api/copilotkit-beautiful-chat/route.ts

@@ -0,0 +1,88 @@
+// Dedicated runtime for the Beautiful Chat flagship showcase cell.
+//
+// Beautiful Chat simultaneously exercises A2UI (dynamic + fixed schema),
+// Open Generative UI, and MCP Apps. The canonical reference
+// (examples/integrations/langgraph-python) ships all three flags on a single
+// runtime, but the 4085 showcase splits those concerns into per-feature
+// endpoints so non-flagship cells keep their per-demo `useFrontendTool` /
+// `useComponent` registrations isolated. This route restores the canonical's
+// combined runtime for just the one cell that needs it.
+//
+// References:
+// - examples/integrations/langgraph-python/src/app/api/copilotkit/[[...slug]]/route.ts
+// - src/app/api/copilotkit-ogui/route.ts (scoping pattern)
+// - src/app/api/copilotkit-mcp-apps/route.ts (mcpApps config pattern)
+
+import type { NextRequest } from "next/server";
+import { NextResponse } from "next/server";
+import {
+  CopilotRuntime,
+  ExperimentalEmptyAdapter,
+  copilotRuntimeNextJSAppRouterEndpoint,
+} from "@copilotkit/runtime";
+import { LangGraphAgent } from "@copilotkit/runtime/langgraph";
+
+const LANGGRAPH_URL =
+  process.env.LANGGRAPH_DEPLOYMENT_URL || "http://localhost:8123";
+
+const beautifulChatAgent = new LangGraphAgent({
+  deploymentUrl: LANGGRAPH_URL,
+  graphId: "beautiful_chat",
+  langsmithApiKey: process.env.LANGSMITH_API_KEY || "",
+});
+
+const agents: Record<string, LangGraphAgent> = {
+  // The page's <CopilotKit agent="beautiful-chat"> resolves here.
+  "beautiful-chat": beautifulChatAgent,
+  // Internal components (headless-chat, example-canvas) call `useAgent()`
+  // with no args, which defaults to agentId "default". Alias to the same
+  // graph so those component hooks resolve instead of throwing
+  // "Agent 'default' not found". This matches the canonical's
+  // `agents: { default: defaultAgent }` shape.
+  default: beautifulChatAgent,
+};
+
+const runtime = new CopilotRuntime({
+  // @ts-ignore -- see main route.ts
+  agents,
+  // Canonical: openGenerativeUI: true, a2ui.injectA2UITool: false, mcpApps.
+  openGenerativeUI: true,
+  a2ui: {
+    // The backend graph has its own `generate_a2ui` tool, so we must NOT
+    // inject the runtime's default A2UI tool on top (that would double-bind
+    // the tool slot and confuse the LLM).
+    injectA2UITool: false,
+    // Models follow the tool-usage guide and omit `catalogId`, and the
+    // middleware then falls back to the unregistered spec basic catalog
+    // ("Catalog not found" render error). Pin the catalog the page registers.
+    defaultCatalogId: "copilotkit://app-dashboard-catalog",
+  },
+  mcpApps: {
+    servers: [
+      {
+        type: "http",
+        url: process.env.MCP_SERVER_URL || "https://mcp.excalidraw.com",
+        // Stable serverId so persisted threads keep restoring the same MCP
+        // server across URL changes.
+        serverId: "beautiful_chat_mcp",
+      },
+    ],
+  },
+});
+
+export const POST = async (req: NextRequest) => {
+  try {
+    const { handleRequest } = copilotRuntimeNextJSAppRouterEndpoint({
+      endpoint: "/api/copilotkit-beautiful-chat",
+      serviceAdapter: new ExperimentalEmptyAdapter(),
+      runtime,
+    });
+    return await handleRequest(req);
+  } catch (error: unknown) {
+    const e = error as { message?: string; stack?: string };
+    return NextResponse.json(
+      { error: e.message, stack: e.stack },
+      { status: 500 },
+    );
+  }
+};