Add --lean flag for simplified TUI mode

Introduce a --lean flag to 'docker agent run' that renders a minimal TUI
with just the message stream, a working indicator, and the editor input.
No sidebar, tab bar, resize handle, status bar, or overlay dialogs are
shown. The implementation reuses the existing TUI code path with
conditional checks rather than maintaining a separate TUI.

Assisted-By: docker-agent

Author: dgageot

cmd/root/new.go

@@ -79,10 +79,10 @@ func (f *newFlags) runNewCommand(cmd *cobra.Command, args []string) error {
 
 	sess := session.New(sessOpts...)
 
-	return runTUI(ctx, rt, sess, nil, nil, appOpts...)
+	return runTUI(ctx, rt, sess, nil, nil, nil, appOpts...)
 }
 
-func runTUI(ctx context.Context, rt runtime.Runtime, sess *session.Session, spawner tui.SessionSpawner, cleanup func(), opts ...app.Opt) error {
+func runTUI(ctx context.Context, rt runtime.Runtime, sess *session.Session, spawner tui.SessionSpawner, cleanup func(), tuiOpts []tui.Option, opts ...app.Opt) error {
 	if gen := rt.TitleGenerator(); gen != nil {
 		opts = append(opts, app.WithTitleGenerator(gen))
 	}
@@ -105,7 +105,7 @@ func runTUI(ctx context.Context, rt runtime.Runtime, sess *session.Session, spaw
 		cleanup = func() {}
 	}
 	wd, _ := os.Getwd()
-	model := tui.New(ctx, spawner, a, wd, cleanup)
+	model := tui.New(ctx, spawner, a, wd, cleanup, tuiOpts...)
 
 	p := tea.NewProgram(model, tea.WithContext(ctx), tea.WithFilter(filter))
 	coalescer.SetSender(p.Send)

cmd/root/run.go

@@ -60,6 +60,7 @@ type runExecFlags struct {
 
 	// Run only
 	hideToolResults bool
+	lean            bool
 
 	// globalPermissions holds the user-level global permission checker built
 	// from user config settings. Nil when no global permissions are configured.
@@ -117,6 +118,7 @@ func addRunOrExecFlags(cmd *cobra.Command, flags *runExecFlags) {
 	_ = cmd.PersistentFlags().MarkHidden("memprofile")
 	cmd.PersistentFlags().BoolVar(&flags.forceTUI, "force-tui", false, "Force TUI mode even when not in a terminal")
 	_ = cmd.PersistentFlags().MarkHidden("force-tui")
+	cmd.PersistentFlags().BoolVar(&flags.lean, "lean", false, "Use a simplified TUI with minimal chrome")
 	cmd.PersistentFlags().BoolVar(&flags.sandbox, "sandbox", false, "Run the agent inside a Docker sandbox (requires Docker Desktop with sandbox support)")
 	cmd.PersistentFlags().StringVar(&flags.sandboxTemplate, "template", "", "Template image for the sandbox (passed to docker sandbox create -t)")
 	cmd.MarkFlagsMutuallyExclusive("fake", "record")
@@ -276,7 +278,7 @@ func (f *runExecFlags) runOrExec(ctx context.Context, out *cli.Printer, args []s
 	}
 
 	sessStore := rt.SessionStore()
-	return runTUI(ctx, rt, sess, f.createSessionSpawner(agentSource, sessStore), initialTeamCleanup, opts...)
+	return runTUI(ctx, rt, sess, f.createSessionSpawner(agentSource, sessStore), initialTeamCleanup, f.tuiOpts(), opts...)
 }
 
 func (f *runExecFlags) loadAgentFrom(ctx context.Context, agentSource config.Source) (*teamloader.LoadResult, error) {
@@ -455,7 +457,16 @@ func (f *runExecFlags) launchTUI(ctx context.Context, out *cli.Printer, rt runti
 		return err
 	}
 
-	return runTUI(ctx, rt, sess, nil, nil, opts...)
+	return runTUI(ctx, rt, sess, nil, nil, f.tuiOpts(), opts...)
+}
+
+// tuiOpts returns the TUI options derived from the current flags.
+func (f *runExecFlags) tuiOpts() []tui.Option {
+	var opts []tui.Option
+	if f.lean {
+		opts = append(opts, tui.WithLeanMode())
+	}
+	return opts
 }
 
 func (f *runExecFlags) buildAppOpts(args []string) ([]app.Opt, error) {

go.mod

@@ -185,7 +185,7 @@ require (
 	github.com/oasdiff/yaml3 v0.0.0-20250309153720-d2182401db90 // indirect
 	github.com/opencontainers/go-digest v1.0.0 // indirect
 	github.com/opencontainers/image-spec v1.1.1 // indirect
-	github.com/patrickmn/go-cache v2.1.0+incompatible // indirect
+	github.com/patrickmn/go-cache v2.1.0+incompatible
 	github.com/perimeterx/marshmallow v1.1.5 // indirect
 	github.com/pjbgf/sha1cd v0.3.2 // indirect
 	github.com/pmezard/go-difflib v1.0.0 // indirect

pkg/tui/page/chat/chat.go

@@ -139,7 +139,8 @@ type chatPage struct {
 	sessionState *service.SessionState
 
 	// State
-	working bool
+	working  bool
+	leanMode bool
 
 	msgCancel       context.CancelFunc
 	streamCancelled bool
@@ -174,6 +175,16 @@ type chatPage struct {
 func (p *chatPage) computeSidebarLayout() sidebarLayout {
 	innerWidth := p.width - appPaddingHorizontal
 
+	// Lean mode: no sidebar at all
+	if p.leanMode {
+		return sidebarLayout{
+			mode:       sidebarCollapsedNarrow,
+			innerWidth: innerWidth,
+			chatWidth:  innerWidth,
+			chatHeight: max(1, p.height),
+		}
+	}
+
 	var mode sidebarLayoutMode
 	switch {
 	case p.width >= minWindowWidth && !p.sidebar.IsCollapsed():
@@ -300,7 +311,7 @@ func getEditorDisplayNameFromEnv(visual, editorEnv string) string {
 }
 
 // New creates a new chat page
-func New(a *app.App, sessionState *service.SessionState) Page {
+func New(a *app.App, sessionState *service.SessionState, opts ...PageOption) Page {
 	p := &chatPage{
 		sidebar:      sidebar.New(sessionState),
 		messages:     messages.New(sessionState),
@@ -309,9 +320,23 @@ func New(a *app.App, sessionState *service.SessionState) Page {
 		sessionState: sessionState,
 	}
 
+	for _, opt := range opts {
+		opt(p)
+	}
+
 	return p
 }
 
+// PageOption configures a chat page.
+type PageOption func(*chatPage)
+
+// WithLeanMode creates a lean chat page with no sidebar.
+func WithLeanMode() PageOption {
+	return func(p *chatPage) {
+		p.leanMode = true
+	}
+}
+
 // Init initializes the chat page
 func (p *chatPage) Init() tea.Cmd {
 	var cmds []tea.Cmd
@@ -518,19 +543,26 @@ func (p *chatPage) View() string {
 		bodyContent = lipgloss.JoinHorizontal(lipgloss.Left, chatView, toggleCol, sidebarView)
 
 	case sidebarCollapsed, sidebarCollapsedNarrow:
-		sidebarRendered := p.renderCollapsedSidebar(sl)
-
-		chatView := styles.ChatStyle.
-			Height(sl.chatHeight).
-			Width(sl.innerWidth).
-			Render(messagesView)
-
-		bodyContent = lipgloss.JoinVertical(lipgloss.Top, sidebarRendered, chatView)
+		if p.leanMode {
+			// Lean mode: no sidebar header, no fixed height
+			bodyContent = styles.ChatStyle.
+				Width(sl.innerWidth).
+				Render(messagesView)
+		} else {
+			sidebarRendered := p.renderCollapsedSidebar(sl)
+			chatView := styles.ChatStyle.
+				Height(sl.chatHeight).
+				Width(sl.innerWidth).
+				Render(messagesView)
+			bodyContent = lipgloss.JoinVertical(lipgloss.Top, sidebarRendered, chatView)
+		}
 	}
 
-	return styles.AppStyle.
-		Height(p.height).
-		Render(bodyContent)
+	appStyle := styles.AppStyle
+	if !p.leanMode {
+		appStyle = appStyle.Height(p.height)
+	}
+	return appStyle.Render(bodyContent)
 }
 
 // renderSidebarHandle renders the sidebar toggle/resize handle.