Tmux Part 4: Vim Integration

Workflow tmux
30

Found the solution:
Updated my .vimrc to:

    if exists('$TMUX')
      let &t_SI = "\<Esc>[3 q"
      let &t_EI = "\<Esc>[0 q"
      " these two lines were outside the if statement 
      " putting them here solves this issue although the cursor shape stays 
      " the same in any mode outside tmux - but that's OK. 
      let &t_SI = "\<Esc>Ptmux;\<Esc>\<Esc>]50;CursorShape=1\x7\<Esc>\\"
      let &t_EI = "\<Esc>Ptmux;\<Esc>\<Esc>]50;CursorShape=0\x7\<Esc>\\"
endif

Thank you for pointing me towards this.