0.62.0

The active CLI's logo, faint in the top-right of the pane. Opposite corner to the theme character, so a theme with one and a session with the other never sit on top of each other.

The pane edge has carried the CLI's colour for a while, and that answers "which one am I in" for anyone who has learned the colours. This answers it for everyone else, and across a screen of panes rather than by reading a tab. At seven percent it is a thing you notice when you look for it and not when you are reading output.

Two shapes of icon, the same split the sidebar markers already make. A single-colour glyph becomes a mask tinted with the CLI's own colour, which is what lets one file serve the tinted, grey and watermark modes at once. A logo that carries its own colours cannot be a mask, because it flattens to a solid square, so it is drawn as the image it is. A CLI with no icon draws nothing rather than inventing a letter.

Desktop only, on the same size rule the theme character uses. One checkbox under CLI markers turns it off.