Everylisp is an abstract Common Lisp REPL that interactively compiles and runs code in every Lisp implementation simultaneously, running test suites, automatically handling restarts, profiling and benchmarking, the works—comparing results, it tries to fix errors first with portable code, then with implementation-dependent code. Treating multi-implementation, multi-platform CI/CD more like cross-implementation delta debugging experiments.
It's an absurd idea, but it might just be a feasible one now.