For as long as engineers have tried to program living cells, the cell itself has remained an unruly collaborator — genetic parts behaving one way in one context, another way in the next, resisting the predictability that true design requires. A research team has now built a framework that treats the host organism not as a passive vessel but as an active variable, using computational digital twins of E. coli to separate what a genetic part inherently does from what the surrounding biology contributes. The work, supported by European and Spanish scientific institutions, offers synthetic biology