diff --git a/src/browser.ts b/src/browser.ts
index 7c076cd..0d2ab4d 100644
--- a/src/browser.ts
+++ b/src/browser.ts
@@ -1523,10 +1523,10 @@ export class BrowserManager {
       cdpUrl = cdpEndpoint;
     } else if (/^\d+$/.test(cdpEndpoint)) {
       // Numeric string - treat as port number (handles JSON serialization quirks)
-      cdpUrl = `http://localhost:${cdpEndpoint}`;
+      cdpUrl = `http://127.0.0.1:${cdpEndpoint}`;
     } else {
       // Unknown format - still try as port for backward compatibility
-      cdpUrl = `http://localhost:${cdpEndpoint}`;
+      cdpUrl = `http://127.0.0.1:${cdpEndpoint}`;
     }
 
     const browser = await chromium
@@ -1534,7 +1534,7 @@ export class BrowserManager {
       .catch(() => {
         throw new Error(
           `Failed to connect via CDP to ${cdpUrl}. ` +
-            (cdpUrl.includes('localhost')
+            (cdpUrl.includes('127.0.0.1')
               ? `Make sure the app is running with --remote-debugging-port=${cdpEndpoint}`
               : 'Make sure the remote browser is accessible and the URL is correct.')
         );