Improve TUI system prompt handling

+ allow setting a default agent

pkg/tui/model/model.go

@@ -37,6 +37,25 @@ func (m *AppModel) ClearConversation() {
 	m.RootMessages = []api.Message{}
 }
 
+func (m *AppModel) ApplySystemPrompt() {
+	var system string
+	agent := m.Ctx.GetAgent(m.Ctx.Config.Defaults.Agent)
+	if agent != nil && agent.SystemPrompt != "" {
+		system = agent.SystemPrompt
+	}
+	if system == "" {
+		system = m.Ctx.DefaultSystemPrompt()
+	}
+	if system != "" {
+		m.Messages = api.ApplySystemPrompt(m.Messages, system, false)
+	}
+}
+
+func (m *AppModel) NewConversation() {
+	m.ClearConversation()
+	m.ApplySystemPrompt()
+}
+
 func (m *AppModel) LoadConversations() (error, []LoadedConversation) {
 	messages, err := m.Ctx.Store.LatestConversationMessages()
 	if err != nil {

pkg/tui/tui.go

@@ -38,6 +38,7 @@ func initialModel(ctx *lmcli.Context, opts LaunchOptions) *Model {
 		Ctx:          ctx,
 		Conversation: opts.InitialConversation,
 	}
+	app.NewConversation()
 
 	m := Model{
 		App:        app,

pkg/tui/views/chat/chat.go

@@ -139,17 +139,6 @@ func Chat(app *model.AppModel) *Model {
 	m.replyCursor.SetChar(" ")
 	m.replyCursor.Focus()
 
-	system := app.Ctx.DefaultSystemPrompt()
-
-	agent := app.Ctx.GetAgent(app.Ctx.Config.Defaults.Agent)
-	if agent != nil && agent.SystemPrompt != "" {
-		system = agent.SystemPrompt
-	}
-
-	if system != "" {
-		m.App.Messages = api.ApplySystemPrompt(m.App.Messages, system, false)
-	}
-
 	m.input.Focus()
 	m.input.MaxHeight = 0
 	m.input.CharLimit = 0

pkg/tui/views/chat/input.go

@@ -53,7 +53,7 @@ func (m *Model) handleInput(msg tea.KeyMsg) tea.Cmd {
 		m.updateContent()
 		return shared.KeyHandled(msg)
 	case "ctrl+n":
-		m.App.ClearConversation()
+		m.App.NewConversation()
 		m.rebuildMessageCache()
 		m.updateContent()
 		return shared.KeyHandled(msg)

pkg/tui/views/conversations/conversations.go

@@ -97,7 +97,7 @@ func (m *Model) handleInput(msg tea.KeyMsg) tea.Cmd {
 		}
 		return shared.KeyHandled(msg)
 	case "n":
-		m.App.ClearConversation()
+		m.App.NewConversation()
 		return shared.ChangeView(shared.ViewChat)
 	case "d":
 		if !m.confirmPrompt.Focused() && len(m.App.Conversations) > 0 && m.cursor < len(m.App.Conversations) {