# CLAUDE.md

This file provides guidance to Claude Code (claude.ai/code) when working with code in this repository.

## What This Is

Personal NixOS system configuration for host `cesium` — an x86_64 desktop workstation with NVIDIA GPU. Uses NixOS with **Flakes** and Home Manager. NixOS version is locked to 25.11.

The project root is `/mnt/data/nixos/`. The actual NixOS configuration lives in the `nixos/` subdirectory and is synced to `/etc/nixos/` via `make sync-etc`, or built directly from `nixos/` via `make rebuild`.

## Commands

```bash
# Rebuild from ./nixos directly (no sync to /etc/nixos)
make rebuild

# Rebuild after upgrading flake inputs (updates flake.lock)
make upgrade

# Sync nixos/ to /etc/nixos and rebuild
make sync-etc

# Sync nixos/ to /etc/nixos and upgrade flake inputs
make upgrade-etc

# Dry-run sync to preview file changes
make sync-etc-dry-run

# Validate all .nix files (runs automatically as pre-commit hook)
make test

# Optimize store and garbage collect
make cleanup
```

## Architecture

Entry point is `nixos/flake.nix`, which defines the `cesium` NixOS configuration:

```
nixos/flake.nix                   # Flake: inputs (nixpkgs 25.11, home-manager, nix-flatpak, unstable)
nixos/configuration.nix           # Top-level: imports all modules, enables Home Manager
├── hardware-configuration.nix    # Auto-generated (gitignored), host hardware
├── cesium.nix                    # Host-specific: NVIDIA drivers, hostname, firewall ports
├── common.nix                    # System-wide: bootloader, locale, GNOME, PipeWire, packages
├── mounts.nix                    # CIFS/SMB mounts to TrueNAS (automount with systemd)
├── services.nix                  # Docker (custom data root /home/docker), ddev
├── users/sebastian.nix           # User account, groups, SSH askpass
├── home.nix                      # Home Manager: apps, shell, git, scripts, Flatpak
├── programs.nix                  # Home Manager: git, shell programs config
├── dconf.nix                     # Home Manager: GNOME dconf settings
├── scripts.nix                   # Custom shell scripts (composer, lazydocker, gclb)
├── flakes.nix                    # Extra flake-based packages (e.g. Hytale launcher)
├── vm-guest.nix                  # Optional: SPICE agent for VM clipboard/file sharing
└── vm-host.nix                   # Optional: KVM/QEMU host with libvirtd, virt-manager
```

Supporting files in `nixos/config/`:
- `p10k.zsh` — Powerlevel10k prompt config
- `zsh-custom.zsh` — Custom zsh configuration
- `crest_iv_black-cut.jpg` — Wallpaper

Key design patterns:
- `cesium.nix` contains all host-specific hardware config (NVIDIA, hostname, ports)
- `common.nix` handles system-level config (boot, locale, desktop, audio, auto-updates, GC)
- `home.nix` handles user-level config via Home Manager (applications, shell, GTK theme, Flatpak)
- `programs.nix` and `dconf.nix` split out Home Manager programs and GNOME settings
- `scripts.nix` defines Docker-wrapped CLI tools using `writeShellScriptBin`
- `mounts.nix` uses systemd automount with 60s idle timeout for TrueNAS SMB shares
- `vm-guest.nix` and `vm-host.nix` are optional modules (not imported by default)
- `nixpkgs-unstable` overlay is used selectively (e.g. `rustdesk-flutter`)

## Conventions

- **Commit messages** use `[TASK]` prefix (e.g., `[TASK] Add filemounts`)
- **Formatting**: 2-space indentation for `.nix` files, 4-space for everything else (see `.editorconfig`)
- **Unfree packages** are allowed (`nixpkgs.config.allowUnfree = true`)
- `hardware-configuration.nix` is gitignored — it's auto-generated per machine