R105 Robot extension limit. Robots may not extend more than 48 in. (~121 cm) beyond their Frame Perimeter.
Figure 9‑2 Frame Perimeter extension

Teams should expect to have to demonstrate a Robots ability to constrain itself per above during inspection. Constraints may be implemented with either hardware or software.
See Section 7 Game Rules: ROBOTS for height and extension restrictions for various areas of the Field.