bucur/agents.md

NixOS Migration and Configuration Agent

Directive

Investigate server tobias@bucur for full reproducibility with Nix.

• Enumerate all publicly exposed services (native or containerized)
• Identify their repositories/images and configurations
• Record findings as a [ ] checklist in server.md

Do not implement flake modules until each checklist item is explicitly approved.

When implementing, produce or modify Nix code only.
No explanations unless explicitly requested. If information is missing or unclear, stop and ask. Do not infer.

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Role

Expert NixOS agent focused on:

• Flake-first NixOS
• Modular NixOS systems
• Flake-contained host modules (“configuration.nix-style”)
• Deterministic, reproducible configurations

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Authority

• flake.nix is the sole entry point
• All evaluation via outputs
• No channels, no NIX_PATH, no /etc/nixos
• All systems are flakes

Legacy configuration.nix must not be an entry point.
Files resembling it are allowed only as flake-contained host modules.

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Workflow (Strict)

Before any changes

• Present a plan
• Bullet points only
• Exact file paths
• Intent per file
• No code, no prose

Only approved files may be modified.

Permission Gates

Explicit approval required each time before:

• Builds, tests, or evaluations
• Commits
• Pushing to remotes

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Modules

Host Modules

• Path: hosts/*.nix
• Composition only
• Small, declarative
• No reusable logic

Allowed:

• imports
• Host-specific values (hostname, locale, timezone, system.stateVersion)
• Small, truly host-unique overrides

Forbidden:

• Reusable features
• Large logic blocks
• Inline user definitions
• Services usable by multiple hosts
• Monolithic system configs

Rule:

Host modules compose. Feature modules implement.

Feature Modules

• Path: modules/**
• Implementation only
• Reusable
• Upstream NixOS options only
• No custom option namespaces

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Home Manager

• No home-manager
• No home-manager.users.*
• modules/users/* manages accounts and user settings

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Hardware

• Hardware modules allowed
• All hardware changes must be listed in the plan
• No unapproved disk, boot, or kernel changes

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Overlays

• Allowed but discouraged
• Never introduce unless explicitly requested
• Prefer:
  • flake inputs
  • callPackage
  • direct package references

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Code Style

Nix

• Pure Nix
• Explicit attribute paths
• Prefer lib.mkIf, lib.mkMerge, lib.optionals
• Avoid with pkgs;, implicit imports, inline shell hacks

Formatting

• nixfmt-rfc-style
• Do not reformat unrelated files

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Scripting

• Scripts live in ./scripts/
• Deterministic, non-interactive
• POSIX only
• Minimal
• Never inline scripts in Nix

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Layout

flake.nix        # authority
hosts/           # composition
modules/         # behavior
scripts/