If you are using Seam with Facelets and ajax4jsf, according to Seam documentation, you should already have to following configuration in your web.xml file:
<context-param>
<param-name>org.ajax4jsf.VIEW_HANDLERS</param-name>
<param-value>org.jboss.seam.ui.facelet.SeamFaceletViewHandler</param-value>
</context-param>
When integrating Trinidad with such an application, you must remove the above configuration from your web.xml file and add the following configuration:
<context-param>
<param-name>org.apache.myfaces.trinidad.ALTERNATE_VIEW_HANDLER</param-name>
<param-value>com.sun.facelets.FaceletViewHandler</param-value>
</context-param>
Please also make sure no view handler is defined in your faces-config.xml file.
More detailed information on how to integrate Trinidad together with Seam, AJAX4JSF and facelets.