I kept writing the same brittle shell one-liners in Dockerfiles to check if binaries exist, env vars are set, and config files are valid. The error messages were always terrible and the syntax inconsistent.

Preflight replaces all that with a single static binary. It handles commands (with version constraints), env vars, files, TCP/HTTP endpoints, checksums, git state, and system resources. Works in FROM scratch images since it has zero dependencies.

Happy to hear what validation patterns I'm missing.