Local CI Environment Simulator That Matches Remote Runners
Developers burn hours on commit-push-wait-fail loops because CI pipelines can't be tested locally. The frustration is universal: you can't reproduce CI failures on your machine because the environments differ. Act (for GitHub Actions) is widely adopted but can't fully simulate GitHub's runners. Dagger abstracts CI into code but requires rewriting pipelines. Someone on HN explicitly said they'd pay for this.
The NixCI blog post nails the architecture: make CI a local-first script that also runs remotely, not the other way around. The trap is trying to perfectly emulate GitHub/GitLab runners. Instead, invert the model: define CI in portable scripts, then have thin adapters that run them on any CI platform. Dagger has the right idea but the wrong adoption path (rewrite everything). Ship a tool that wraps existing YAML workflows into locally-runnable containers.
landscape (3 existing solutions)
Local CI execution is a solved problem in theory (run the same containers locally) but broken in practice because CI platforms bake services, caching, and secrets into their hosted infrastructure that can't be replicated in a Docker container. The gap is a tool that creates a high-fidelity local replica of CI runner environments without requiring pipeline rewrites.