Host identity as a contract

A computer. The wish that every OS had agreed on one API call. They did not. Cousins exist.

POSIX uname. Freedesktop /etc/os-release (ID, ID_LIKE, VERSION_ID). Windows RtlGetVersion. Darwin sw_vers.

That is already more agreement than people remember. What nobody shipped is one struct every tool can fill.

Dev-Centr calls the framework Host Awareness and the struct a Host Identity Record:

family, distro, like[], version, arch, overlays[], caps (shells, package managers, formats).

A new OS is first-class when a probe can fill that record. Microsoft will not file a PR. A hobby kernel can ship an os-release-shaped file.

This is an OpenShellOrg-shaped contract (host honesty at the boundary) implemented today inside PlayTime. Canonical page: scriptbook Host Awareness.

If you ask Equivalence Engine "what OS am I?" so that it can pick the method for "what OS am I?", the run never starts.

PlayTime is a compiled binary. It already knows NT vs POSIX. It walks a baked probe cascade (file/API first; command is the escape hatch). It freezes the record. Then catalogs may run.

PowerShell-on-Linux does not save that first step. $IsLinux works only inside pwsh. The engine is not inside pwsh.

WSL is Linux plus overlay wsl. Cygwin/MSYS are Windows plus a POSIX hat. A container is an overlay on whatever family. Caps and format filters read the stickers. Do not invent a new family for each hat.

Shared probe tables can be read by Equivalence Engine (for family / inherit) and copied into PlayTime at CI time. Runtime PlayTime must not call the engine to learn family. Empty-engine-plus-network-rules would fail on a plane and recreate the deadlock.

A new Unix-like distro that speaks os-release is data. A kernel that is neither NT nor POSIX is a new probe kind (code), then a table row.

See PlayTime at the shell boundary for why this engine still lives in Dev-Centr while it is being built.