fix(headroom): proxy dashboard through app (#2372)

Add a 9Router-side proxy so the Headroom dashboard and its data
endpoints (/stats, /health, /stats-history, /transformations/feed)
stay same-origin when opened remotely through the 9Router app, and
add an "Open Headroom Dashboard" link in the Token Saver modal.

Gate /api/headroom/proxy as LOCAL_ONLY (loopback + CLI token) to
match start/stop, and strip cookie/authorization when the Headroom
target is non-loopback to avoid leaking viewer credentials.

Co-authored-by: Cursor <cursoragent@cursor.com>

src/app/(dashboard)/dashboard/token-saver/TokenSaverClient.js

@@ -374,6 +374,16 @@ export default function TokenSaverClient() {
               {headroomStatusLabel}
             </span>
           </div>
+          {headroomRunning && (
+            <a
+              href="/api/headroom/proxy/dashboard"
+              target="_blank"
+              rel="noreferrer"
+              className="w-full rounded border border-border px-4 py-2 text-center text-sm hover:bg-surface-2"
+            >
+              Open Headroom Dashboard
+            </a>
+          )}
           <div className="flex flex-col gap-1">
             <p className="text-sm font-medium">Proxy URL</p>
             <Input

src/app/api/headroom/proxy/[...path]/route.js

@@ -0,0 +1,104 @@
+import { NextResponse } from "next/server";
+import { getSettings } from "@/lib/localDb";
+import { DEFAULT_HEADROOM_URL } from "@/lib/headroom/detect";
+
+export const dynamic = "force-dynamic";
+
+const HOP_BY_HOP_HEADERS = new Set([
+  "connection",
+  "keep-alive",
+  "proxy-authenticate",
+  "proxy-authorization",
+  "te",
+  "trailer",
+  "transfer-encoding",
+  "upgrade",
+]);
+
+const DASHBOARD_PREFIX = "/api/headroom/proxy";
+const LOOPBACK_HOSTS = new Set(["localhost", "127.0.0.1", "::1"]);
+
+async function getTargetBase() {
+  const settings = await getSettings();
+  const url = settings.headroomUrl || DEFAULT_HEADROOM_URL;
+  const target = new URL(url);
+  if (!["http:", "https:"].includes(target.protocol)) {
+    throw new Error("Headroom URL must use http or https");
+  }
+  return target;
+}
+
+function buildTargetUrl(base, path, search) {
+  const target = new URL(base);
+  target.pathname = `/${path.join("/")}`;
+  target.search = search;
+  return target;
+}
+
+function forwardedHeaders(request, target) {
+  const headers = new Headers(request.headers);
+  for (const header of headers.keys()) {
+    if (HOP_BY_HOP_HEADERS.has(header.toLowerCase())) headers.delete(header);
+  }
+  headers.delete("host");
+  // Never leak viewer credentials to a non-loopback Headroom host
+  if (!LOOPBACK_HOSTS.has(target.hostname.replace(/^\[|\]$/g, "").toLowerCase())) {
+    headers.delete("cookie");
+    headers.delete("authorization");
+  }
+  return headers;
+}
+
+function rewriteDashboardHtml(html) {
+  return html.replace(
+    /fetch\('(?=\/(?:stats|health|stats-history|transformations\/feed))/g,
+    `fetch('${DASHBOARD_PREFIX}`,
+  );
+}
+
+async function proxy(request, { params }) {
+  try {
+    const base = await getTargetBase();
+    const { search } = new URL(request.url);
+    const path = (await params).path || [];
+    const target = buildTargetUrl(base, path, search);
+    const method = request.method;
+    const hasBody = !["GET", "HEAD"].includes(method);
+
+    const response = await fetch(target, {
+      method,
+      headers: forwardedHeaders(request, target),
+      body: hasBody ? request.body : undefined,
+      duplex: hasBody ? "half" : undefined,
+      redirect: "manual",
+    });
+
+    const headers = new Headers(response.headers);
+    for (const header of headers.keys()) {
+      if (HOP_BY_HOP_HEADERS.has(header.toLowerCase())) headers.delete(header);
+    }
+
+    if (path.join("/") === "dashboard") {
+      const contentType = response.headers.get("content-type") || "";
+      if (contentType.includes("text/html")) {
+        headers.delete("content-length");
+        return new NextResponse(rewriteDashboardHtml(await response.text()), {
+          status: response.status,
+          headers,
+        });
+      }
+    }
+
+    return new NextResponse(response.body, { status: response.status, headers });
+  } catch (error) {
+    return NextResponse.json({ error: error.message }, { status: 500 });
+  }
+}
+
+export const GET = proxy;
+export const POST = proxy;
+export const PUT = proxy;
+export const PATCH = proxy;
+export const DELETE = proxy;
+export const HEAD = proxy;
+export const OPTIONS = proxy;

src/dashboardGuard.js

@@ -81,6 +81,7 @@ const LOCAL_ONLY_PATHS = [
   "/api/auth/reset-password",
   "/api/headroom/start",
   "/api/headroom/stop",
+  "/api/headroom/proxy",
 ];
 
 const LOOPBACK_HOSTS = new Set(["localhost", "127.0.0.1", "::1"]);