CodeRunner Documentation (V3.1.0)
12 A note on accessibility
To assist the use of screen readers for visually impaired students, text area inputs now have two modes:
When keyboard focus first enters them via Tab or Shift+TAb, they are in 'non-capturing' mode, and pressing TAB or Shift+TAB moves to the next or previous form control.
After you start typing, or if focus enters by way of a click, they go into Tab-capturing mode, and then pressing Tab indents.
CTRL+M switches modes (as recommended by https://www.w3.org/TR/wai-aria-practices/#richtext).
Esc always switches to non-capturing mode.