diff --git a/internal/config/config.go b/internal/config/config.go
index 316f8a1..1ff0a1f 100644
--- a/internal/config/config.go
+++ b/internal/config/config.go
@@ -14,12 +14,50 @@ import (
 //go:embed defaults.yaml
 var defaultsYAML []byte
 
+type Packages struct {
+	Base []string `yaml:"base"`
+}
+type ArduinoCLIConfig struct {
+	Version string   `yaml:"version"`
+	URL     string   `yaml:"url"`
+	Cores   []string `yaml:"cores"`
+}
+type ZshPlugin struct {
+	Name string `yaml:"name"`
+	Repo string `yaml:"repo"`
+}
+type ZshConfig struct {
+	OhMyZshRepo string      `yaml:"oh_my_zsh_repo"`
+	Plugins     []ZshPlugin `yaml:"plugins"`
+}
+type ZellijConfig struct {
+	ConfigURL string `yaml:"config_url"`
+}
+type ThemesConfig struct {
+	Source string `yaml:"source"`
+}
+type ShellConfigBlock struct {
+	Name    string `yaml:"name"`
+	File    string `yaml:"file"`
+	Content string `yaml:"content"`
+}
+type ShellConfigSection struct {
+	Blocks []ShellConfigBlock `yaml:"blocks"`
+}
+
 // Config is the fully-resolved runtime configuration.
 type Config struct {
-	Version         int               `yaml:"version"`
-	ExtraPackages   []string          `yaml:"extra_packages"`
-	DisabledModules []string          `yaml:"disabled_modules"`
-	ThemeOverrides  map[string]string `yaml:"theme_overrides"`
+	Version         int                `yaml:"version"`
+	ExtraPackages   []string           `yaml:"extra_packages"`
+	DisabledModules []string           `yaml:"disabled_modules"`
+	ThemeOverrides  map[string]string  `yaml:"theme_overrides"`
+	Packages        Packages           `yaml:"packages"`
+	Fonts           []string           `yaml:"fonts"`
+	ArduinoCLI      ArduinoCLIConfig   `yaml:"arduino_cli"`
+	Zsh             ZshConfig          `yaml:"zsh"`
+	Zellij          ZellijConfig       `yaml:"zellij"`
+	Themes          ThemesConfig       `yaml:"themes"`
+	ShellConfig     ShellConfigSection `yaml:"shell_config"`
 }
 
 const currentVersion = 1
@@ -78,5 +116,26 @@ func merge(base, over Config) Config {
 		}
 		out.ThemeOverrides = merged
 	}
+	if len(over.Packages.Base) > 0 {
+		out.Packages = over.Packages
+	}
+	if len(over.Fonts) > 0 {
+		out.Fonts = over.Fonts
+	}
+	if over.ArduinoCLI.Version != "" {
+		out.ArduinoCLI = over.ArduinoCLI
+	}
+	if over.Zsh.OhMyZshRepo != "" {
+		out.Zsh = over.Zsh
+	}
+	if over.Zellij.ConfigURL != "" {
+		out.Zellij = over.Zellij
+	}
+	if over.Themes.Source != "" {
+		out.Themes = over.Themes
+	}
+	if len(over.ShellConfig.Blocks) > 0 {
+		out.ShellConfig = over.ShellConfig
+	}
 	return out
 }
diff --git a/internal/config/config_test.go b/internal/config/config_test.go
index 9bc6db8..db6cf95 100644
--- a/internal/config/config_test.go
+++ b/internal/config/config_test.go
@@ -48,6 +48,31 @@ theme_overrides:
 	}
 }
 
+func TestDefaultsCarryModuleInputs(t *testing.T) {
+	cfg, err := Load("/nonexistent/overlay.yaml")
+	if err != nil {
+		t.Fatal(err)
+	}
+	if len(cfg.Packages.Base) == 0 {
+		t.Error("Packages.Base empty")
+	}
+	if len(cfg.Fonts) == 0 {
+		t.Error("Fonts empty")
+	}
+	if cfg.ArduinoCLI.Version == "" {
+		t.Error("ArduinoCLI.Version empty")
+	}
+	if cfg.ArduinoCLI.URL == "" {
+		t.Error("ArduinoCLI.URL empty")
+	}
+	if cfg.Zsh.OhMyZshRepo == "" {
+		t.Error("Zsh.OhMyZshRepo empty")
+	}
+	if len(cfg.ShellConfig.Blocks) == 0 {
+		t.Error("ShellConfig.Blocks empty")
+	}
+}
+
 func TestLoadRejectsUnknownVersion(t *testing.T) {
 	dir := t.TempDir()
 	path := filepath.Join(dir, "overlay.yaml")
diff --git a/internal/config/defaults.yaml b/internal/config/defaults.yaml
index 94293d7..e25e5ff 100644
--- a/internal/config/defaults.yaml
+++ b/internal/config/defaults.yaml
@@ -2,3 +2,81 @@ version: 1
 extra_packages: []
 disabled_modules: []
 theme_overrides: {}
+
+packages:
+  base:
+    - base-devel
+    - git
+    - curl
+    - wget
+    - unzip
+    - zip
+    - tree
+    - htop
+    - neofetch
+    - ripgrep
+    - fd
+    - bat
+    - eza
+    - jq
+    - zsh
+    - clang
+    - ca-certificates
+
+fonts:
+  - ttf-jetbrains-mono-nerd
+
+arduino_cli:
+  version: "0.35.3"
+  url: "https://github.com/arduino/arduino-cli/releases/download/v0.35.3/arduino-cli_0.35.3_Linux_64bit.tar.gz"
+  cores:
+    - arduino:avr
+
+zsh:
+  oh_my_zsh_repo: "https://github.com/ohmyzsh/ohmyzsh.git"
+  plugins:
+    - name: zsh-autosuggestions
+      repo: https://github.com/zsh-users/zsh-autosuggestions
+    - name: zsh-syntax-highlighting
+      repo: https://github.com/zsh-users/zsh-syntax-highlighting.git
+
+zellij:
+  config_url: ""
+
+themes:
+  source: "lib/themes"
+
+shell_config:
+  blocks:
+    - name: archduino-path
+      file: ".zshrc"
+      content: |
+        export PATH="$HOME/.local/bin:$PATH"
+    - name: archduino-editor
+      file: ".zshrc"
+      content: |
+        export EDITOR="nvim"
+        export VISUAL="nvim"
+    - name: archduino-starship
+      file: ".zshrc"
+      content: |
+        eval "$(starship init zsh)"
+    - name: archduino-zellij
+      file: ".zshrc"
+      content: |
+        if [[ -z "$ZELLIJ" ]]; then
+          zellij attach --create archduino
+        fi
+    - name: archduino-aliases
+      file: ".zshrc"
+      content: |
+        alias adev="zellij --layout arduino"
+        alias ac="arduino-cli"
+        alias acc="arduino-cli compile"
+        alias acu="arduino-cli upload"
+        alias acm="arduino-cli monitor"
+        alias acb="arduino-cli board list"
+        alias lg="lazygit"
+        alias v="nvim"
+        alias y="yazi"
+        alias theme="archduino-theme"