diff --git a/agent/tools/browser/browser_tool.py b/agent/tools/browser/browser_tool.py
index c5139812..c91be26c 100644
--- a/agent/tools/browser/browser_tool.py
+++ b/agent/tools/browser/browser_tool.py
@@ -145,7 +145,8 @@ class BrowserTool(BaseTool):
         url = args.get("url", "").strip()
         if not url:
             return ToolResult.fail("Error: 'url' is required for navigate action")
-        if not url.startswith(("http://", "https://")):
+        # Only auto-prepend https:// for bare hosts; preserve file://, about:, data:, etc.
+        if "://" not in url and not url.startswith(("about:", "data:")):
             url = "https://" + url
         timeout = args.get("timeout", 30000)
         service = self._get_service()