Certain aspects relate to systems and techniques for manually and robotically driving a medical instrument. For example, a system can include a handle configured to receive an elongated shaft of a medical instrument. The handle can include a gripping mechanism for selectively engaging the elongated shaft, and an articulation input and configured for receiving user inputs of commanded articulation of the elongated shaft. The system can include an instrument drive mechanism configured to engage a base of the medical instrument. The instrument drive mechanism can include at least one robotic drive output configured to engage a robotic drive input of the base to cause articulation of the elongated shaft based on the user inputs received at the articulation input, and a first connector configured to removably couple the instrument drive mechanism to an instrument positioning device.
