My team works on programming tools that supply developers with actionable feedback during development. Feedback is actionable if it is relevant to the programmer’s task, if the programmer can rely on its correctness, and if it arrives in a timely manner. The feedback we derive protects developers against introducing unsafe code, security vulnerabilities, and specification violations, yet it also informs development tools such as compiler optimizations and refactorings. To address this vision, we conduct basic research in programming languages, algorithms, and software verification that enables actionable feedback in a form that is useful in practice.