When manhole is used directly, then it is very responsive, and the performance doesn't degrade with increase of screen size. It holds only what user entered and writes the input line and command output directly to its transport, without bothering itself with processing of the whole screen. When I embed manhole into the widget like above, then the performance suffers. I think this is due to `TerminalBuffer` having to hold whole widget area (columns * rows) in memory, even if only a small portion of it is actually occupied by user input and command output. Rendering the whole buffer on each keystroke is slow. After experimenting a little bit, I think optimizations that you described mostly apply to `ManholeWidget.render` method, which shouldn't traverse the whole buffer on each keystroke. Currently I don't see how this involves patching widget implementation in Twisted. What is more important to me is that `TerminalBuffer` implementation is slightly incomplete. I think it misses color support, because I couldn't make it work with `ColoredManhole`.