Continued improvement in computing efficiency requires functional specialization of hardware designs. Agile hardware design methodologies have been proposed to alleviate the increased design costs of custom silicon architectures, but their practice thus far has been accompanied with challenges in integration and validation of complex systems-on-a-chip (SoCs). We present the Chipyard framework, an integrated SoC design, simulation, and implementation environment for specialized compute systems. Chipyard includes configurable, composable, open-source, generator-based IP blocks that can be used across multiple stages of the hardware development flow while maintaining design intent and integration consistency. Through cloud-hosted FPGA accelerated simulation and rapid ASIC implementation, Chipyard enables continuous validation of physically realizable customized systems.