chore: import upstream snapshot with attribution

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

@@ -0,0 +1,169 @@
+import { NextRequest, NextResponse } from "next/server";
+import {
+  CopilotRuntime,
+  ExperimentalEmptyAdapter,
+  copilotRuntimeNextJSAppRouterEndpoint,
+} from "@copilotkit/runtime";
+import { LangGraphAgent } from "@copilotkit/runtime/langgraph";
+import crypto from "node:crypto";
+
+// Emit a structured server-side error log with a correlation id so the
+// 500 we return to the client carries no stack/message details (which
+// can leak internal config, prompts, or upstream URLs) while operators
+// can still grep logs for the same `errorId` to find the full failure.
+function logRouteError(err: unknown): string {
+  const error = err instanceof Error ? err : new Error(String(err));
+  const errorId = crypto.randomUUID();
+  console.error(
+    JSON.stringify({
+      at: new Date().toISOString(),
+      level: "error",
+      phase: "setup",
+      errorId,
+      message: error.message,
+      stack: error.stack,
+    }),
+  );
+  return errorId;
+}
+
+const AGENT_URL = process.env.AGENT_URL || "http://localhost:8123";
+
+console.log("[copilotkit/route] Initializing CopilotKit runtime");
+console.log(`[copilotkit/route] AGENT_URL: ${AGENT_URL}`);
+
+// Per-request request/response logging is gated behind this flag (default off).
+// Under d6 probe fan-out, unconditional per-request logs flooded Railway's
+// 500-logs/sec cap and killed the replica ("Messages dropped" → container stop).
+// Set SHOWCASE_ROUTE_DEBUG=1 to re-enable verbose per-request tracing locally.
+const ROUTE_DEBUG =
+  process.env.SHOWCASE_ROUTE_DEBUG === "1" ||
+  process.env.SHOWCASE_ROUTE_DEBUG === "true";
+
+function createAgent(graphId: string = "sample_agent") {
+  return new LangGraphAgent({
+    deploymentUrl: `${AGENT_URL}/`,
+    graphId,
+  });
+}
+
+const agentNames = [
+  "agentic_chat",
+  "human_in_the_loop",
+  "gen-ui-tool-based",
+  "gen-ui-agent",
+  "shared-state-read",
+  "shared-state-write",
+  "shared-state-streaming",
+  "prebuilt-sidebar",
+  "prebuilt-popup",
+  "chat-slots",
+  "chat-customization-css",
+  "headless-simple",
+];
+
+const agents: Record<string, LangGraphAgent> = {};
+for (const name of agentNames) {
+  agents[name] = createAgent();
+}
+
+// Dedicated-graph agents for tool-rendering + reasoning demos.
+agents["tool-rendering"] = createAgent("tool_rendering");
+agents["tool-rendering-default-catchall"] = createAgent("tool_rendering");
+agents["tool-rendering-custom-catchall"] = createAgent("tool_rendering");
+agents["tool-rendering-reasoning-chain"] = createAgent(
+  "tool_rendering_reasoning_chain",
+);
+agents["agentic-chat-reasoning"] = createAgent("reasoning_agent");
+agents["reasoning-default-render"] = createAgent("reasoning_agent");
+
+// Interrupt variants — share the dedicated `interrupt_agent` graph that uses
+// langgraph's `interrupt()` primitive inside `schedule_meeting`.
+agents["gen-ui-interrupt"] = createAgent("interrupt_agent");
+agents["interrupt-headless"] = createAgent("interrupt_agent");
+
+// Dedicated-graph agents — each cell has its own LangGraph graph with a
+// tailored system prompt (tools=[], CopilotKitMiddleware attached).
+agents["frontend_tools"] = createAgent("frontend_tools");
+agents["frontend-tools-async"] = createAgent("frontend_tools_async");
+agents["hitl-in-app"] = createAgent("hitl_in_app");
+// In-Chat HITL via the high-level `useHumanInTheLoop` hook — backend
+// agent has zero tools; the frontend-registered `book_call` tool is
+// injected into the LLM's tool list by `CopilotKitMiddleware`. Both
+// the canonical `hitl-in-chat` demo and the `hitl-in-chat-booking`
+// alias share the same backend graph.
+agents["hitl-in-chat"] = createAgent("hitl_in_chat");
+agents["hitl-in-chat-booking"] = createAgent("hitl_in_chat");
+// HITL step-selection: dedicated graph with tools=[] + CopilotKitMiddleware.
+// The `human_in_the_loop` alias in the neutral-assistant loop above maps to
+// `sample_agent` which has 7+ backend tools and a custom AgentState — the
+// frontend-only `generate_task_steps` tool (from useHumanInTheLoop) is the
+// ONLY tool this demo needs, so a minimal graph avoids state/tool contention.
+agents["human_in_the_loop"] = createAgent("hitl_steps");
+agents["readonly-state-agent-context"] = createAgent(
+  "readonly_state_agent_context",
+);
+
+// Shared State (Read + Write) — bidirectional shared state between UI and
+// agent. UI writes `preferences` via agent.setState; middleware reads them
+// into the system prompt; agent writes `notes` back via the `set_notes` tool.
+agents["shared-state-read-write"] = createAgent("shared_state_read_write");
+
+// Sub-Agents — supervisor delegates to research_agent / writing_agent /
+// critique_agent (each a full create_agent under the hood). Every delegation
+// is appended to `state.delegations` for live UI rendering.
+agents["subagents"] = createAgent("subagents");
+
+agents["default"] = createAgent();
+
+console.log(
+  `[copilotkit/route] Registered ${Object.keys(agents).length} agent names: ${Object.keys(agents).join(", ")}`,
+);
+
+export const POST = async (req: NextRequest) => {
+  try {
+    const { handleRequest } = copilotRuntimeNextJSAppRouterEndpoint({
+      endpoint: "/api/copilotkit",
+      serviceAdapter: new ExperimentalEmptyAdapter(),
+      runtime: new CopilotRuntime({
+        // @ts-ignore
+        agents,
+      }),
+    });
+
+    const response = await handleRequest(req);
+    if (!response.ok) {
+      console.log(`[copilotkit/route] Response status: ${response.status}`);
+    } else if (ROUTE_DEBUG) {
+      console.log(`[copilotkit/route] Response status: ${response.status}`);
+    }
+    return response;
+  } catch (error: unknown) {
+    // Log full message + stack server-side under a correlation id; return
+    // only the id to the client so we don't leak internal details (upstream
+    // URLs, env-driven config, prompts, etc.) into HTTP responses.
+    const errorId = logRouteError(error);
+    return NextResponse.json(
+      { error: "internal runtime error", errorId },
+      { status: 500 },
+    );
+  }
+};
+
+export const GET = async () => {
+  let agentStatus = "unknown";
+  try {
+    const res = await fetch(`${AGENT_URL}/ok`, {
+      signal: AbortSignal.timeout(3000),
+    });
+    agentStatus = res.ok ? "reachable" : `error (${res.status})`;
+  } catch (e: unknown) {
+    agentStatus = `unreachable (${(e as Error).message})`;
+  }
+
+  return NextResponse.json({
+    status: "ok",
+    agent_url: AGENT_URL,
+    agent_status: agentStatus,
+  });
+};