any ideas?

then, how can i control url encode behavior manually?

org.jboss.seam.ui.component.UISeamCommandBase :

private static Class PORTLET_REQUEST;
   
   static
   {
      try
      {
         PORTLET_REQUEST = Class.forName("javax.portlet.PortletRequest");
      }
      catch (Exception e) {}
   }

private static boolean isPortletRequest(FacesContext facesContext)
   {
      return PORTLET_REQUEST !=null && 
            PORTLET_REQUEST.isInstance( facesContext.getExternalContext().getRequest() );
   }
public String getUrl() throws UnsupportedEncodingException
   {
...
ViewUrlBuilder url = new ViewUrlBuilder(viewId, getFragment(), !isPortletRequest(getFacesContext()));
...
   }

for example, add an attribute encode to s:button and s:link, the url encoding behavior should execute according to this attribute.