Local or pointlike probes and excitations have traditionally served as the central tools of physics. Yet two pillars of modern physics—quantum mechanics and gravity—exhibit intrinsically nonlocal phenomena that cannot be fully captured by pointlike observables alone. Recent progress across areas ranging from quantum matter to holography has begun to reveal the power of extended observables, or defects, both as refined probes of phases of matter and as sources of new phenomena, especially in strongly coupled gapless systems. This transdisciplinary theoretical effort has led, among other advances, to the discovery of generalized symmetries; rigorous predictions for the behavior of boundaries and impurities at critical points; new tools for studying quantum information; powerful numerical methods for solving strongly coupled quantum field theories (QFTs); and new insights into gauge–gravity duality. This program will bring together researchers from high-energy theory, quantum information, and condensed matter physics, including specialists in numerical simulations, working on the physics of defects. Central themes will include the lattice–continuum correspondence, defects and quantum information, Lorentzian dynamics and causality of extended probes, topological defects and generalized symmetries, and holographic descriptions of extended operators. By fostering interactions across communities, the program aims to uncover universal structures, develop new computational tools, and advance our understanding of strongly coupled matter through the lens of defects.