Performance is the currency of modern computing. Achieving peak throughput on fast‑evolving accelerators demands more control than today’s compilers provide. I will present Exo and the Exocompilation paradigm: a user‑schedulable programming language that shifts two responsibilities traditionally hard‑coded in compilers–hardware backends and optimization strategies–into safe, extensible user libraries. In Exo, optimizations are expressed as verified rewrites that guarantee functional equivalence, and low‑level primitives (e.g., explicit instruction selection, GPU asynchrony) give programmers precise control. This design enables targeting CPUs, GPUs, and matrix engines, and supports concise, reusable scheduling libraries that match or surpass the performance of state-of-the-art libraries such as cuBLAS and MKL. Exo‑generated kernels already ship at scale, including on Apple devices.