Long chats open at once and load more as you scroll up
A long chat now opens on its newest messages right away, and earlier ones load in pages as you scroll up, so no chat is ever too large to open.
Opening a chat used to send its whole history to the window in one piece. A long enough chat was too large to carry and failed to open. Now the newest messages arrive first, and each time you near the top the next page loads above you without moving what you are reading.
Very long tool output and answers are shortened on screen with a note saying how much is left out. The full text stays in the saved chat.