An end effector coupler for a surgical arm can include a body, a proximal coupler, and a tool lock. The tool lock can releasably retain a tool stem to the end effector coupler. The tool lock can include a keyed opening, a pin bore, a pin disposed in the bin bore, a biasing element located in the pin bore, and a pin release including an actuator, the pin release operable to retract the pin into to the body to disengage the pin from the tool stem allowing release of the tool stem from the keyed opening.