The Giant Magellan Telescope will have four first-generation observing modes: Natural seeing, ground-layer AO, natural guide star AO, and laser tomography AO. All observing modes require active control of the segmented primary mirror. Two segmented secondary mirrors will be available: A fast-steering secondary mirror and an adaptive secondary mirror. Four identical Acquisition, Guiding, and Wavefront Sensing (AGWS) probes patrolling the Gregorian focal plane provide all necessary wavefront sensing for the natural seeing and GLAO observing modes. A telescope-wide laser metrology truss enables rapid initial alignment. In the diffraction-limited modes, the AGWS controls field-dependent aberrations and maintains the phasing alignment of the segments, while high-order natural and laser guide star wavefront sensors at each instrument sense atmospheric phase errors. All of these subsystems are currently being prototyped on several wavefront control testbeds that reproduce the GMT optical design on a smaller scale. I will report on the current design and construction status and testbed activities.