fix(gateway): proxy browser server functions to workspace apps

packages/dev-server/test/gateway.test.ts

@@ -4,6 +4,7 @@ import {
   defaultGatewayHostname,
   forwardAuthFailure,
   forwardAuthHeaders,
+  gatewayBrowserRpcHeaders,
   gatewayProxyHeaders,
   gatewayWebSocketBackendHeaders,
   stripUntrustedInternalHeaders,
@@ -176,13 +177,40 @@ test("nested SSO proxy keeps the protected app's original request headers", () =
   expect(proxied.get("x-original-uri")).toBe("/settings");
 });
 
-test("the reserved RPC prefix is refused at the gateway before any proxying", () => {
-  expect(isRpcGatewayPath(RPC_PATH_PREFIX)).toBe(true);
+test("the gateway proxies browser server functions but refuses private RPC routes", () => {
+  expect(isRpcGatewayPath(RPC_PATH_PREFIX)).toBe(false);
   expect(isRpcGatewayPath(`${RPC_PATH_PREFIX}/billing/createInvoice`)).toBe(true);
   expect(isRpcGatewayPath("/api/billing")).toBe(false);
   expect(isRpcGatewayPath("/__wrnexus/rpcfoo")).toBe(false);
 });
 
+test("browser RPC proxy preserves CSRF credentials and trusts only the internal hop", () => {
+  const request = new Request(`http://web.localhost:3000${RPC_PATH_PREFIX}`, {
+    method: "POST",
+    headers: {
+      host: "web.localhost:3000",
+      origin: "http://web.localhost:3000",
+      cookie: "wrn-csrf=token",
+      "x-csrf-token": "token",
+      [RPC_INTERNAL_HEADER]: "forged",
+    },
+  });
+  const headers = gatewayBrowserRpcHeaders(
+    request,
+    new URL(request.url),
+    "127.0.0.1",
+    true,
+    "http://127.0.0.1:3001",
+  );
+
+  expect(headers.get("origin")).toBe("http://127.0.0.1:3001");
+  expect(headers.get("cookie")).toBe("wrn-csrf=token");
+  expect(headers.get("x-csrf-token")).toBe("token");
+  expect(headers.get("x-forwarded-host")).toBe("web.localhost:3000");
+  expect(headers.has(RPC_INTERNAL_HEADER)).toBe(false);
+  expect(headers.has("host")).toBe(false);
+});
+
 test("an inbound internal-marker header from outside is stripped regardless of casing", () => {
   for (const name of [
     RPC_INTERNAL_HEADER,