WWDC26 expanded Apple's Foundation Models framework into much of Shikisha's territory: sessions, typed structured output, tool calling, image input, and a public LanguageModel protocol that can back a session with the on-device model, Private Cloud Compute, or third-party models.
If you are targeting current Apple platforms, I would start there first. Shikisha still has value for older OS versions, a fuller retrieval stack, StateGraph workflows, and offline testing, but the system framework now covers a much larger portion of the workflow surface than it did when I started this project.
I added the same note to the blog post and the README. I plan to explore Foundation Models myself when time allows, both on its own terms and to see where Shikisha should sit on top of it.