Constellation SDK's (docs.pega.com)

Because constellation has a stateless architecuter user sessions are not maintained over requests. This has effect on debugging tools. For instance the clipboard viewer tool is not available in run time as it was before.

See article below for tools available to debug applications.

Tools for debugging constellation using tracer tool

Also, Data Page functionality and best practices have changed considerably. Because it is stateless, the Constellation architecture does not support temporary pages – you must use Data Pages instead.

Data pages in Constellation