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ADR 0002: macOS 27 is the platform baseline

Date: 2026-09-17. Status: accepted.

Context

FoundationModels first shipped in macOS 26, so the framework alone would allow a lower floor. The project owner set macOS 27 as the baseline, and the development and test machine runs 27.0.

Decision

The SwiftPM platform is .macOS("27.0"). It is written as a string because PackageDescription in Xcode 27.0 has no .v27 case. Do not lower the floor for compatibility.

Consequences

  • Any macOS 27 API can be used without availability checks.
  • CI must run on a macOS 27 image. None is provisioned yet, so the workflow is manual-only for now.