When running cmd.exe inside a pseudoconsole, trying to enter the alternate screen buffer escape sequences via echo �[?1049h and echo �[?1049l does not result in them being sent to the ConPTY output pipe. It appears to me they are being processed inside cmd.exe and swallowed.

Does it make sense / is it possible for these sequences be output by ConPTY? This would allow terminal emulators to do things like support scrolling inside programs such as less which make use of the alternate screen buffer.