diff --git a/internal/app/config.go b/internal/app/config.go
new file mode 100644
index 0000000..bf5b4bc
--- /dev/null
+++ b/internal/app/config.go
@@ -0,0 +1,89 @@
+package app
+
+import (
+	"fmt"
+	"ha-tray/internal"
+	"os"
+	"strings"
+
+	"github.com/BurntSushi/toml"
+	"github.com/joho/godotenv"
+)
+
+// Config represents the application configuration
+type Config struct {
+	Server *string `toml:"server"`
+	APIKey string  `toml:"api_key"`
+}
+
+// DefaultConfig returns a default configuration
+func DefaultConfig() *Config {
+	apiKey := os.Getenv("API_KEY")
+	if apiKey == "" {
+		// Try loading from .env
+		err := godotenv.Load()
+		if err != nil {
+			apiKey = os.Getenv("API_KEY")
+		} else {
+			apiKey = os.Getenv("API_KEY")
+		}
+	}
+
+	instanceUrl := internal.Ptr(strings.TrimSpace(os.Getenv("INSTANCE_URL")))
+	if *instanceUrl == "" {
+		instanceUrl = nil
+	}
+
+	return &Config{
+		Server: instanceUrl,
+		APIKey: apiKey,
+	}
+}
+
+// LoadConfig loads configuration from a TOML file
+func LoadConfig(filename string) (*Config, error) {
+	config := DefaultConfig()
+
+	// Check if file exists
+	if _, err := os.Stat(filename); os.IsNotExist(err) {
+		// Create default config file if it doesn't exist
+		if err := SaveConfig(filename, config); err != nil {
+			return nil, fmt.Errorf("failed to create default config file: %w", err)
+		}
+		return config, nil
+	}
+
+	// Load existing config file
+	if _, err := toml.DecodeFile(filename, config); err != nil {
+		return nil, fmt.Errorf("failed to decode config file: %w", err)
+	}
+
+	return config, nil
+}
+
+// SaveConfig saves configuration to a TOML file
+func SaveConfig(filename string, config *Config) error {
+	file, err := os.Create(filename)
+	if err != nil {
+		return fmt.Errorf("failed to create config file: %w", err)
+	}
+	defer file.Close()
+
+	encoder := toml.NewEncoder(file)
+	if err := encoder.Encode(config); err != nil {
+		return fmt.Errorf("failed to encode config: %w", err)
+	}
+
+	return nil
+}
+
+// Validate checks if the configuration is valid
+func (c *Config) Validate() error {
+	if c.Server == nil || *c.Server == "" {
+		return fmt.Errorf("server address is required")
+	}
+	if c.APIKey == "" {
+		return fmt.Errorf("API key is required")
+	}
+	return nil
+}