diff --git a/README.md b/README.md
index 2565ece..1a350a4 100644
--- a/README.md
+++ b/README.md
@@ -24,3 +24,4 @@ Docs live separately in `humanode-network/vortex-simulator-docs`.
 
 - `dist/` is generated build output.
 - UI expects the API at `/api/*`. During local dev, Rsbuild proxies `/api/*` to `http://127.0.0.1:8788` by default (override with `API_PROXY_TARGET`).
+- To point the UI at a different API host, set `RSBUILD_PUBLIC_API_BASE_URL` at build time or serve `public/vortex-config.json` with `{"apiBaseUrl":"https://api.example.com"}`.
diff --git a/public/vortex-config.json b/public/vortex-config.json
new file mode 100644
index 0000000..f6d80c7
--- /dev/null
+++ b/public/vortex-config.json
@@ -0,0 +1,3 @@
+{
+  "apiBaseUrl": ""
+}
diff --git a/src/index.tsx b/src/index.tsx
index 4ba6f4d..17c0ba3 100644
--- a/src/index.tsx
+++ b/src/index.tsx
@@ -8,16 +8,45 @@ import "./styles/global.css";
 import "./styles/base.css";
 import { initTheme } from "./lib/theme";
 
-initTheme("sky");
+type RuntimeConfig = {
+  apiBaseUrl?: string;
+  apiHeaders?: Record<string, string>;
+  apiCredentials?: RequestCredentials;
+};
 
-const rootEl = document.getElementById("root");
-if (rootEl === null) {
-  throw new Error("no root");
+async function loadRuntimeConfig(): Promise<void> {
+  if (typeof window === "undefined") return;
+  const target = window as typeof window & {
+    __VORTEX_CONFIG__?: RuntimeConfig;
+  };
+  if (target.__VORTEX_CONFIG__) return;
+  try {
+    const res = await fetch("/vortex-config.json", { cache: "no-store" });
+    if (!res.ok) return;
+    const json = (await res.json()) as unknown;
+    if (json && typeof json === "object") {
+      target.__VORTEX_CONFIG__ = json as RuntimeConfig;
+    }
+  } catch {
+    // Ignore missing runtime config.
+  }
 }
 
-const root = ReactDOM.createRoot(rootEl);
-root.render(
-  <React.StrictMode>
-    <App />
-  </React.StrictMode>,
-);
+async function bootstrap(): Promise<void> {
+  await loadRuntimeConfig();
+  initTheme("sky");
+
+  const rootEl = document.getElementById("root");
+  if (rootEl === null) {
+    throw new Error("no root");
+  }
+
+  const root = ReactDOM.createRoot(rootEl);
+  root.render(
+    <React.StrictMode>
+      <App />
+    </React.StrictMode>,
+  );
+}
+
+void bootstrap();
diff --git a/src/lib/apiClient.ts b/src/lib/apiClient.ts
index aafab04..cd0e72f 100644
--- a/src/lib/apiClient.ts
+++ b/src/lib/apiClient.ts
@@ -27,6 +27,18 @@ import type {
   PoolProposalPageDto,
 } from "@/types/api";
 
+type ApiClientRuntimeConfig = {
+  apiBaseUrl?: string;
+  apiHeaders?: Record<string, string>;
+  apiCredentials?: RequestCredentials;
+};
+
+declare global {
+  interface Window {
+    __VORTEX_CONFIG__?: ApiClientRuntimeConfig;
+  }
+}
+
 export type ApiErrorPayload = {
   error?: {
     message?: string;
@@ -47,16 +59,51 @@ export function getApiErrorPayload(error: unknown): ApiErrorPayload | null {
   return data as ApiErrorPayload;
 }
 
+const envApiBaseUrl =
+  import.meta.env.RSBUILD_PUBLIC_API_BASE_URL ??
+  import.meta.env.VITE_API_BASE_URL ??
+  "";
+
+function getRuntimeConfig(): ApiClientRuntimeConfig | undefined {
+  if (typeof window === "undefined") return undefined;
+  return window.__VORTEX_CONFIG__;
+}
+
+function getApiBaseUrl(): string {
+  const runtimeConfig = getRuntimeConfig();
+  return runtimeConfig?.apiBaseUrl ?? envApiBaseUrl ?? "";
+}
+
+function getApiCredentials(): RequestCredentials {
+  const runtimeConfig = getRuntimeConfig();
+  return runtimeConfig?.apiCredentials ?? "include";
+}
+
+function getApiHeaders(): Record<string, string> {
+  const runtimeConfig = getRuntimeConfig();
+  return runtimeConfig?.apiHeaders ?? {};
+}
+
+function resolveApiUrl(path: string): string {
+  if (/^https?:\/\//i.test(path)) return path;
+  const apiBaseUrl = getApiBaseUrl();
+  if (!apiBaseUrl) return path;
+  const base = apiBaseUrl.replace(/\/$/, "");
+  const suffix = path.startsWith("/") ? path : `/${path}`;
+  return `${base}${suffix}`;
+}
+
 async function readJsonResponse<T>(res: Response): Promise<T> {
   const contentType = res.headers.get("content-type") ?? "";
   const isJson = contentType.toLowerCase().includes("application/json");
-  const body = isJson ? ((await res.json()) as unknown) : null;
+  const body = isJson ? ((await res.json()) as unknown) : await res.text();
   if (!res.ok) {
     const payload = (body as ApiErrorPayload | null) ?? null;
-    const message =
+    const rawMessage =
       payload?.error?.message ??
-      (typeof body === "string" ? body : null) ??
-      `HTTP ${res.status}`;
+      (typeof body === "string" && body.trim() ? body : null) ??
+      res.statusText;
+    const message = `HTTP ${res.status}${rawMessage ? `: ${rawMessage}` : ""}`;
     const error = new Error(message) as ApiError;
     if (payload) error.data = payload;
     error.status = res.status;
@@ -66,7 +113,10 @@ async function readJsonResponse<T>(res: Response): Promise<T> {
 }
 
 export async function apiGet<T>(path: string): Promise<T> {
-  const res = await fetch(path, { credentials: "include" });
+  const res = await fetch(resolveApiUrl(path), {
+    credentials: getApiCredentials(),
+    headers: getApiHeaders(),
+  });
   return await readJsonResponse<T>(res);
 }
 
@@ -75,10 +125,11 @@ export async function apiPost<T>(
   body: unknown,
   init?: { headers?: HeadersInit },
 ): Promise<T> {
-  const res = await fetch(path, {
+  const res = await fetch(resolveApiUrl(path), {
     method: "POST",
-    credentials: "include",
+    credentials: getApiCredentials(),
     headers: {
+      ...getApiHeaders(),
       "content-type": "application/json",
       ...(init?.headers ?? {}),
     },
@@ -159,14 +210,14 @@ export async function apiChamberChatSignalPost(
   input: {
     peerId: string;
     kind: "offer" | "answer" | "candidate";
-    targetPeerId?: string;
+    toPeerId?: string;
     payload: Record<string, unknown>;
   },
 ): Promise<{ ok: true }> {
   return await apiPost<{ ok: true }>(`/api/chambers/${chamberId}/chat/signal`, {
     peerId: input.peerId,
     kind: input.kind,
-    targetPeerId: input.targetPeerId,
+    toPeerId: input.toPeerId,
     payload: input.payload,
   });
 }
diff --git a/src/pages/chambers/Chamber.tsx b/src/pages/chambers/Chamber.tsx
index 11f9b60..a433022 100644
--- a/src/pages/chambers/Chamber.tsx
+++ b/src/pages/chambers/Chamber.tsx
@@ -249,14 +249,14 @@ const Chamber: React.FC = () => {
   const sendSignal = useCallback(
     async (input: {
       kind: "offer" | "answer" | "candidate";
-      targetPeerId: string;
+      toPeerId: string;
       payload: Record<string, unknown>;
     }) => {
       if (!id) return;
       await apiChamberChatSignalPost(id, {
         peerId,
         kind: input.kind,
-        targetPeerId: input.targetPeerId,
+        toPeerId: input.toPeerId,
         payload: input.payload,
       });
     },
@@ -273,7 +273,7 @@ const Chamber: React.FC = () => {
         if (!event.candidate) return;
         void sendSignal({
           kind: "candidate",
-          targetPeerId: remotePeerId,
+          toPeerId: remotePeerId,
           payload: event.candidate.toJSON() as Record<string, unknown>,
         });
       };
@@ -321,7 +321,7 @@ const Chamber: React.FC = () => {
         if (pc.localDescription) {
           await sendSignal({
             kind: "answer",
-            targetPeerId: remotePeerId,
+            toPeerId: remotePeerId,
             payload: pc.localDescription.toJSON() as unknown as Record<
               string,
               unknown
@@ -404,7 +404,7 @@ const Chamber: React.FC = () => {
             if (pc.localDescription) {
               await sendSignal({
                 kind: "offer",
-                targetPeerId: peer.peerId,
+                toPeerId: peer.peerId,
                 payload: pc.localDescription.toJSON() as unknown as Record<
                   string,
                   unknown