Despite growing interest in Entrepreneurial Support Organizations (ESO) and the established entrepreneurial cognition literature, we lack understanding of how entrepreneurs make decisions within ESO programs and particularly under time-compressed conditions. To qualitatively examine pivoting decisions within sustainable venture accelerator programs, we conducted 40 interviews with 15 founders and 6 staff members in 2 accelerators in France. Contrary to conventional Lean Startup methodology, we found that pivots under time-compression are primarily driven by startup-world community feedback rather than end-user feedback. Our findings reveal a novel three-step mechanism by which pivot decisions are made under time compression: awareness (typically initiated by accelerator staff, mentors and investors), empowerment (often through peers and alumni), and enablement (via community support and resources). Extending existing theories of founder identity and adaptation, we discovered that founders with Ecological-Dominant identities exhibited the highest propensity to pivot across multiple dimensions, while Commercial-Dominant identities showed the least pivoting behavior. Our theoretical model of a founder’s communities of identity and practice adds further explanatory dimensions to our empirical findings. These findings have important implications for understanding how early-stage entrepreneurship can be accelerated through social-cognitive mechanism. Additionally, our study bridges the gap between the environmental entrepreneurship and accelerator research streams, which also provides practical insights for ESO focused on sustainable ventures that could address time-sensitive environmental challenges.