Coral stock ear-marked for reef restoration that is not thermally enhanced may not survive the next summer heatwave, as seen during the 2023 Caribbean summer. Thermotolerance of corals is strongly affected by their photosymbionts (Symbiodiniaceae) and can be boosted by manipulating their photosymbiont communities. Further, experimental evolution can be used to enhance the thermotolerance of photosymbionts. We have shown that heat-evolved photosymbionts can form a symbiosis with taxonomically diverse coral species and enhance their thermal bleaching tolerance across life stages (larvae, recruits and adults), without compromising coral growth. These novel symbioses have already persisted for 1-2 years in the lab and field. We tracked the performance of some of our bio-engineered corals in the field over the course of one annual thermal cycle (including a summer heatwave of eight Degree Heating Weeks), and observed corals hosting heat-evolved photosymbionts paled less and were healthier than conspecifics hosting a closely related native photosymbiont species. Laboratory experiments showed that heat-evolved photosymbionts can be expelled by corals and acquired by bleached, nearby corals at low percentages. The presentation is based on over a decade of our work and will summarize the state of this intervention and its potential pathways to implementation.