Tmux: bad key binding error

Question

$ tmux source-file ~/.tmux.conf
bad key: Tab-Space
unknown key: Tab-Space

What's up? I checked the man page. Tab and Space are valid. Why doesn't this combination work when C-b works?

Answer 1

Figured it out. Rather Tab, use T. Stackexchange is too slow nowadays.

Answer 2

The tab-space would be two characters, which tmux does not support. See manpage:

tmux may be controlled from an attached client by using a key combination of a prefix key, ‘C-b’ (Ctrl-b) by default, followed by a command key.

That is, controlb is a special case; no other two-character sequences can be bound (unless you change the prefix key, of course).