fix: make browser relay bind address configurable (#39364) (thanks @mvanhorn)

src/browser/extension-relay.test.ts

@@ -1202,4 +1202,23 @@ describe("chrome extension relay server", () => {
     },
     RELAY_TEST_TIMEOUT_MS,
   );
+
+  it(
+    "restarts the relay when bindHost changes for the same port",
+    async () => {
+      const port = await getFreePort();
+      cdpUrl = `http://127.0.0.1:${port}`;
+
+      const initial = await ensureChromeExtensionRelayServer({ cdpUrl });
+      expect(initial.bindHost).toBe("127.0.0.1");
+
+      const rebound = await ensureChromeExtensionRelayServer({
+        cdpUrl,
+        bindHost: "0.0.0.0",
+      });
+      expect(rebound.bindHost).toBe("0.0.0.0");
+      expect(rebound.port).toBe(port);
+    },
+    RELAY_TEST_TIMEOUT_MS,
+  );
 });

src/browser/extension-relay.ts

@@ -234,12 +234,20 @@ export async function ensureChromeExtensionRelayServer(opts: {
 
   const existing = relayRuntimeByPort.get(info.port);
   if (existing) {
-    return existing.server;
+    if (existing.server.bindHost !== bindHost) {
+      await existing.server.stop();
+    } else {
+      return existing.server;
+    }
   }
 
   const inFlight = relayInitByPort.get(info.port);
   if (inFlight) {
-    return await inFlight;
+    const server = await inFlight;
+    if (server.bindHost === bindHost) {
+      return server;
+    }
+    await server.stop();
   }
 
   const extensionReconnectGraceMs = envMsOrDefault(
@@ -998,12 +1006,13 @@ export async function ensureChromeExtensionRelayServer(opts: {
 
     const addr = server.address() as AddressInfo | null;
     const port = addr?.port ?? info.port;
+    const actualBindHost = addr?.address || bindHost;
     const host = info.host;
     const baseUrl = `${new URL(info.baseUrl).protocol}//${host}:${port}`;
 
     const relay: ChromeExtensionRelayServer = {
       host,
-      bindHost,
+      bindHost: actualBindHost,
       port,
       baseUrl,
       cdpWsUrl: `ws://${host}:${port}/cdp`,

src/config/schema.help.ts

@@ -250,6 +250,8 @@ export const FIELD_HELP: Record<string, string> = {
     "Starting local CDP port used for auto-allocated browser profile ports. Increase this when host-level port defaults conflict with other local services.",
   "browser.defaultProfile":
     "Default browser profile name selected when callers do not explicitly choose a profile. Use a stable low-privilege profile as the default to reduce accidental cross-context state use.",
+  "browser.relayBindHost":
+    "Bind IP address for the Chrome extension relay listener. Leave unset for loopback-only access, or set an explicit non-loopback IP such as 0.0.0.0 only when the relay must be reachable across network namespaces (for example WSL2) and the surrounding network is already trusted.",
   "browser.profiles":
     "Named browser profile connection map used for explicit routing to CDP ports or URLs with optional metadata. Keep profile names consistent and avoid overlapping endpoint definitions.",
   "browser.profiles.*.cdpPort":

src/config/schema.labels.ts

@@ -118,6 +118,7 @@ export const FIELD_LABELS: Record<string, string> = {
   "browser.attachOnly": "Browser Attach-only Mode",
   "browser.cdpPortRangeStart": "Browser CDP Port Range Start",
   "browser.defaultProfile": "Browser Default Profile",
+  "browser.relayBindHost": "Browser Relay Bind Address",
   "browser.profiles": "Browser Profiles",
   "browser.profiles.*.cdpPort": "Browser Profile CDP Port",
   "browser.profiles.*.cdpUrl": "Browser Profile CDP URL",