---
name: schunix-schapi-direction
description: "Schunix is aimed at being a NeXTSTEP/macOS-shaped system with a native SchAPI over a POSIX personality, with permanent Windows-grade compatibility"
metadata: 
  node_type: memory
  type: project
  originSessionId: 9d8a2aef-bcf0-47a0-96c6-f706efab4a95
  modified: 2026-08-07T16:29:50.730Z
---

**Agreed 2026-08-06.** Schunix is no longer "a Unix-like kernel with a userland
attached". It is aimed at being a **system**: NeXTSTEP/macOS-shaped layering,
with POSIX/Unix kept complete but demoted from identity to *personality*, and a
native higher-level API called **SchAPI** above it. Written up in
`docs/plan/schapi.md`.

The architecture is borrowed from macOS; the compatibility policy is borrowed
from **Windows** (nothing is ever removed after 1.0). Those are two different
systems — macOS drops things aggressively — and the mix is deliberate.

**The load-bearing mechanism:** the stable ABI is a *library*
(`libschunix`), not the syscall table. That is why macOS can renumber syscalls
freely while old binaries keep working, and why Linux is stuck with every
syscall mistake it ever made. Syscalls become private and renumberable; only
libschunix may issue them. This does **not** contradict
[[schunix-linux-abi-decision]] — Linux numbering stays as the Linux
personality's entry path, frozen because Linux froze it, not because we did.

Everything today is tier `provisional`; the freeze starts at 1.0 and covers
only what is explicitly marked `stable` then. Committing now would enshrine
things like the `fcntl(F_SETFL)` no-op fixed in [[schunix-doom-acceptance-test]].

`compat/` holds **shims written in terms of the current API**, not parallel
implementations. If an old entry point cannot be expressed as a translation,
that is a defect in the new API to fix *before* freezing.

`src-trunk/` is a NetBSD checkout — reference material and a parts bin, never
built, never in an image. Highest-value pieces: `sys/net`+`sys/netinet` (the
TCP/IP stack, for the roadmap's Phase 2), `subr_pool.c` (slab allocator), and
the autoconf driver model. **NetBSD is not uniformly licensed** — a minority of
files still carry the 4-clause advertising clause and Berkeley's 1999
rescission only covers UC-copyrighted files. Check every file before copying:
`grep -l "All advertising materials"`. See [[schunix-licensing]].

Ordering is unchanged: this is a direction, not a task. The native Windows
build has to boot first — see [[schunix-build-environment]].