LLVM is foundational software, so stakes for making changes to it are very high, and most downstream vendors of LLVM have elaborate testing pipelines to validate all of the properties they care about. However, because these private pipelines are often slow and disconnected from the community, detecting defects is expensive and leads to labor-intensive negotiations over misaligned technical requirements. To improve the experience for both contributors and downstreams, this talk shares lessons from 15 years of LLVM continuous integration experience to advocate for shared upstream CI infrastructure that "shifts left" on testing, to create a better, more harmonious experience for contributors and consumers alike.