Why won’t my new chat read the old transcript?

I am a very inexperienced coder (actually not a coder at all) who is trying to build a POS. Claude and I are getting along swimmingly, but the chat is lagging due to the length. I tried moving to a new chat and Claude assured me he would be able to read the new chat, but he says he can’t read the transcript from the old chat. Is there anything that can do? According to Claude, this project will take another 8 months. I’m worried I won’t have the continuity if I have to keep moving to new chats. Any insight would be most helpful.