diff --git a/lib/bot.go b/lib/bot.go
index 1009180..d768f32 100644
--- a/lib/bot.go
+++ b/lib/bot.go
@@ -6,6 +6,10 @@ import (
 
 type Bot struct {
 	session *discordgo.Session
+
+	chatCommandHandlers    chatCommandHandlers
+	messageCommandHandlers messageCommandHandlers
+	userCommandHandlers    userCommandHandlers
 }
 
 func Start(token string) (*Bot, error) {
@@ -22,8 +26,13 @@ func Start(token string) (*Bot, error) {
 
 	bot := &Bot{
 		session:                s,
+		chatCommandHandlers:    chatCommandHandlers{},
+		messageCommandHandlers: messageCommandHandlers{},
+		userCommandHandlers:    userCommandHandlers{},
 	}
 
+	bot.session.AddHandler(bot.handleInteraction)
+
 	return bot, nil
 }
 
@@ -34,6 +43,35 @@ func (b *Bot) Stop() error {
 	return nil
 }
 
-func (b *Bot) HandleCommand(c Command) {
-	b.commands = append(b.commands, c)
+func (b *Bot) handleInteraction(s *discordgo.Session, ic *discordgo.InteractionCreate) {
+	var err error
+
+	switch ic.Type {
+	case discordgo.InteractionApplicationCommand:
+		err = b.handleApplicationCommand(s, ic)
+	}
+
+	_, err = s.ChannelMessageSend(ic.ChannelID, err.Error())
+	panic(err) // TODO: handle error
+}
+
+func (b *Bot) handleApplicationCommand(
+	s *discordgo.Session,
+	ic *discordgo.InteractionCreate,
+) error {
+	data := ic.ApplicationCommandData()
+
+	var err error
+
+	if data.CommandType == discordgo.ChatApplicationCommand {
+		err = b.chatCommandHandlers[sessionCommandID{data.ID, ic.GuildID}].Handle(
+			ChatCommandCtx{},
+		)
+	} else if data.CommandType == discordgo.MessageApplicationCommand {
+		err = b.messageCommandHandlers[sessionCommandID{data.ID, ic.GuildID}].Handle(MessageCommandCtx{})
+	} else if data.CommandType == discordgo.UserApplicationCommand {
+		err = b.userCommandHandlers[sessionCommandID{data.ID, ic.GuildID}].Handle(UserCommandCtx{})
+	}
+
+	return err
 }
diff --git a/lib/bot_commands.go b/lib/bot_commands.go
new file mode 100644
index 0000000..432ff26
--- /dev/null
+++ b/lib/bot_commands.go
@@ -0,0 +1,147 @@
+package bot
+
+import (
+	"fmt"
+
+	"github.com/bwmarrin/discordgo"
+)
+
+type commandID struct {
+	Name    string
+	GuildID string
+}
+
+type sessionCommandID struct {
+	ID      string
+	GuildID string
+}
+
+type (
+	chatCommandHandlers    map[sessionCommandID]Handler[ChatCommandCtx]
+	messageCommandHandlers map[sessionCommandID]Handler[MessageCommandCtx]
+	userCommandHandlers    map[sessionCommandID]Handler[UserCommandCtx]
+)
+
+func (b *Bot) MustHandleCommand(c Command, guildID ...string) {
+	if err := b.HandleCommand(c, guildID...); err != nil {
+		panic(err)
+	}
+}
+
+func (b *Bot) HandleCommand(c Command, guildID ...string) error {
+	var g string
+	if len(guildID) > 0 {
+		g = guildID[0]
+	}
+
+	if err := c.Validate(); err != nil {
+		return fmt.Errorf("failed to handle command %q: %v", c.ApplicationCommand().Name, err)
+	}
+
+	sessionCmd, err := b.sessionCommand(c.ApplicationCommand().Name, g)
+	if err != nil {
+		return err
+	}
+
+	return b.updateCommand(c, sessionCmd, g)
+}
+
+func (b *Bot) updateCommand(
+	botCmd Command,
+	sessionCmd *discordgo.ApplicationCommand,
+	guildID ...string,
+) error {
+	var err error
+
+	var g string
+	if len(guildID) > 0 {
+		g = guildID[0]
+	}
+
+	if sessionCmd == nil {
+		sessionCmd, err = b.session.ApplicationCommandCreate(
+			b.session.State.User.ID,
+			g,
+			botCmd.ApplicationCommand(),
+		)
+		if err != nil {
+			return err
+		}
+	} else {
+		sessionCmd, err = b.session.ApplicationCommandEdit(
+			b.session.State.User.ID,
+			g,
+			sessionCmd.ID,
+			botCmd.ApplicationCommand(),
+		)
+		if err != nil {
+			return err
+		}
+	}
+
+	switch botCmd.ApplicationCommand().Type {
+	case discordgo.ChatApplicationCommand:
+		if c, ok := botCmd.(*ChatCommand); ok {
+			b.chatCommandHandlers[sessionCommandID{sessionCmd.ID, g}] = c.Handler
+		} else {
+			return err
+		}
+	case discordgo.MessageApplicationCommand:
+		if c, ok := botCmd.(*MessageCommand); ok {
+			b.messageCommandHandlers[sessionCommandID{sessionCmd.ID, g}] = c.Handler
+		} else {
+			return err
+		}
+	case discordgo.UserApplicationCommand:
+		if c, ok := botCmd.(*UserCommand); ok {
+			b.userCommandHandlers[sessionCommandID{sessionCmd.ID, g}] = c.Handler
+		} else {
+			return err
+		}
+	}
+
+	return nil
+}
+
+func (b *Bot) sessionCommand(
+	name string,
+	guildID ...string,
+) (*discordgo.ApplicationCommand, error) {
+	var g string
+	if len(guildID) > 0 {
+		g = guildID[0]
+	}
+
+	sessionCmds, err := b.sessionCommands(g)
+	if err != nil {
+		return nil, err
+	}
+
+	cmd, ok := sessionCmds[commandID{Name: name, GuildID: g}]
+	if !ok {
+		return nil, nil
+	}
+
+	return cmd, nil
+}
+
+func (b *Bot) sessionCommands(
+	guildID ...string,
+) (map[commandID]*discordgo.ApplicationCommand, error) {
+	var g string
+	if len(guildID) > 0 {
+		g = guildID[0]
+	}
+
+	appCmds, err := b.session.ApplicationCommands(b.session.State.User.ID, g)
+	if err != nil {
+		return nil, err
+	}
+
+	cmds := make(map[commandID]*discordgo.ApplicationCommand, len(appCmds))
+	for _, c := range appCmds {
+		cmds[commandID{Name: c.Name, GuildID: g}] = c
+	}
+
+	return cmds, err
+}