config/AGENTS.md

AGENTS.md - AI Assistant Context

This file provides context for AI assistants working with thegeneralist's Nix configuration.

Quick Commands

Build & Deploy Commands

# Build specific host
nixos-rebuild switch --flake .#<hostname>        # Linux
darwin-rebuild switch --flake .#<hostname>       # macOS  

# Update flake dependencies
nix flake update

# Check configuration validity
nix flake check

# Format Nix files  
nixpkgs-fmt **/*.nix

# Clean up old generations
nh clean all --keep 3 --keep-since 4d

Development Commands

# Enter dev shell with tools
nix develop

# Edit secrets
agenix -e <secret-name>.age

# Re-encrypt all secrets
agenix -r

Architecture Overview

File Structure Conventions

• flake.nix - Main entry point, defines inputs/outputs
• hosts/ - Host-specific configurations
  • Each host has default.nix that calls lib.mkSystem
  • configuration.nix contains host-specific settings
• modules/ - Reusable system modules
  • common/ - Cross-platform modules (always loaded)
  • darwin/ - macOS-specific modules
  • linux/ - Linux-specific modules
• lib/ - Custom library functions
  • mkSystem - Main system builder function

Host Naming & Categorization

• Hosts ending in mbp or containing central-mbp → Darwin
• All others → NixOS
• Current hosts:
  • thegeneralist (NixOS)
  • thegeneralist-central (NixOS)
  • thegeneralist-mbp (Darwin)
  • thegeneralist-central-mbp (Darwin)

Code Conventions

Nix Style Guidelines

• Use nixpkgs-fmt for formatting
• Prefer explicit attribute sets over with statements
• Use meaningful variable names
• Add comments for complex logic

Module Organization

# Standard module structure
{ config, lib, pkgs, ... }:
{
  # Module configuration here
}

Host Configuration Pattern

# hosts/<hostname>/default.nix
lib: inputs: self: lib.mkSystem "<os>" ./configuration.nix

# hosts/<hostname>/configuration.nix  
{ config, pkgs, ... }: {
  # Host-specific settings
}

Common Modification Patterns

Adding a New Package

1. System-wide: Add to appropriate modules/*/packages.nix
2. User-specific: Add to home-manager config in host's configuration.nix

Adding a New Module

1. Create .nix file in appropriate modules/ subdirectory
2. Module is auto-discovered and loaded

Adding a New Host

1. Create hosts/<hostname>/ directory
2. Add default.nix with system type
3. Add configuration.nix with host settings
4. Optionally add hardware-configuration.nix

Managing Secrets

1. Define in secrets.nix with proper recipients
2. Reference as config.age.secrets.<name>.path
3. Edit with agenix -e <secret>.age

Key Features to Remember

Distributed Builds

• thegeneralist-central is the main build machine
• Other hosts offload builds via SSH
• SSH keys and build users configured automatically

Binary Caches

• Personal: cache.thegeneralist01.com
• Community: cache.garnix.io
• Official: cache.nixos.org

Home Manager Integration

• Configured via modules/common/home-manager.nix
• Per-host customization in host's configuration.nix
• Includes nh tool for optimized rebuilds

Development Tools

• Development shell includes: nil, nixpkgs-fmt, agenix
• Custom options available via lib.mkOption
• Flake inputs follow nixpkgs for consistency

Debugging Tips

Build Issues

1. Check syntax: nix flake check
2. Update dependencies: nix flake update
3. Clear cache: nix-collect-garbage -d
4. Verify module imports and paths

Secret Issues

1. Check keys.nix has correct public keys
2. Verify secret recipient list in secrets.nix
3. Re-encrypt if needed: agenix -r

Module Not Loading

1. Verify file is in correct modules/ subdirectory
2. Check file extension is .nix
3. Ensure valid Nix syntax

Performance Optimizations

Recommended Practices

• Use distributed builds when available
• Leverage binary caches
• Regular garbage collection via nh clean
• Keep flake inputs updated but stable

Avoiding Rebuilds

• Prefer adding packages to existing modules over creating new ones
• Use overlays for package modifications
• Consider impact on all hosts when modifying common modules

Testing Strategy

Before Major Changes

1. Test on single host first
2. Verify flake builds: nix flake check
3. Check that all hosts can still build
4. Consider impact on secrets/distributed builds

Rollback Strategy

# System level rollback
nixos-rebuild switch --rollback
darwin-rebuild switch --rollback

# Or boot into previous generation from bootloader

User Preferences

Code Style

• Clean, readable Nix code
• Proper indentation and formatting
• Meaningful comments for complex logic
• Consistent naming conventions

Organization Preferences

• Modular approach over monolithic configs
• Platform-specific separation (darwin/linux/common)
• Host-specific customization in host directories
• Secrets properly encrypted and organized

This configuration emphasizes maintainability, security, and cross-platform consistency.