Comprehensive nix-Darwin support assessment and implementation roadmap

[Copilot]

Provides production-ready technical assessment for extending nixos-systems to support nix-Darwin configurations alongside existing NixOS infrastructure.

Problem Statement

User asked: "Without doing it, how much work would it take to refactor to also support nix-Darwin configurations?"

Deliverables

Main Assessment (DARWIN_SUPPORT_ASSESSMENT.md)

20+ page technical analysis covering:

• Architecture readiness: modular design, flexible inventory, unified user management already compatible
• Component breakdown: 10 major components with specific changes, effort estimates, code examples
• Migration strategy: 5-phase plan (Foundation → Software Profiles → Integration → Documentation → Validation)
• Timeline: 2-3 weeks (41-62 hours dev + 24-38 hours testing)

Supporting Documentation

• docs/DARWIN_QUICK_REFERENCE.md - TL;DR with implementation checklist
• docs/darwin-architecture.md - Visual architecture diagrams (current vs proposed)
• docs/IMPLEMENTATION_SUMMARY.md - Executive summary

Example Implementations (docs/darwin-examples/)

Complete working examples demonstrating:

# Platform-aware service configuration
lib.mkMerge [
  (lib.mkIf pkgs.stdenv.isLinux {
    systemd.services.updater = { ... };
  })
  (lib.mkIf pkgs.stdenv.isDarwin {
    launchd.agents.updater = { ... };
  })
]

Key examples:

• Darwin host types with macOS system defaults
• Platform-conditional service management (systemd vs launchd)
• Mixed Linux/Darwin inventory configuration

Key Technical Changes Required

1. Host Generation (1-2 days) - Refactor hosts/default.nix:

   • Add platform dispatcher: if darwin then mkDarwinHost else mkNixOSHost
   • Split outputs: nixosConfigurations + darwinConfigurations

2. Module Structure (2-3 hours) - Separate platform-specific config:

   • Rename common.nix → linux-common.nix (boot, disko, systemd)
   • Create darwin-common.nix (system.defaults, launchd, no boot config)

3. Software Profiles (1-2 days) - Platform detection in sw/:

   • Conditional package lists: lib.optionals stdenv.isLinux [kde...]
   • Service translation: systemd.services.* → launchd.agents.*

4. Host Types (1 day) - Create hosts/types/darwin-*.nix:

   • macOS system defaults instead of kernel params
   • No disko/bootloader configuration

Architecture Assessment

Feasibility: ✅ Recommended - existing structure well-suited for extension

Risk: Low - changes are additive and isolated, no breaking changes to NixOS configs

Complexity: Medium-high due to systemd→launchd translation and dual-platform testing requirements

Updated

• README.md: Added "Future Enhancements" section with Darwin support overview

Original prompt

Without doing it, how much work would it take to refactor to also support nix-Darwin configurations?

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