feat: add custom header/footer regions for extensions

Extensions can now place persistent header (above stream) and footer
(below status bar) regions via ctx.SetHeader/SetFooter. Single-instance
per slot, reuses WidgetContent/WidgetStyle types and WidgetUpdateEvent
for notifications. Includes thread-safe Runner storage, SDK methods,
UI rendering with height distribution, and example extension.

cmd/root.go

@@ -330,6 +330,48 @@ func widgetProviderForUI(k *kit.Kit) func(string) []ui.WidgetData {
 	}
 }
 
+// headerProviderForUI returns a function that converts the extension header
+// to a *ui.WidgetData for the TUI. Returns nil if extensions are disabled,
+// which is safe — the UI treats a nil GetHeader as "no header".
+func headerProviderForUI(k *kit.Kit) func() *ui.WidgetData {
+	if !k.HasExtensions() {
+		return nil
+	}
+	return func() *ui.WidgetData {
+		config := k.GetExtensionHeader()
+		if config == nil {
+			return nil
+		}
+		return &ui.WidgetData{
+			Text:        config.Content.Text,
+			Markdown:    config.Content.Markdown,
+			BorderColor: config.Style.BorderColor,
+			NoBorder:    config.Style.NoBorder,
+		}
+	}
+}
+
+// footerProviderForUI returns a function that converts the extension footer
+// to a *ui.WidgetData for the TUI. Returns nil if extensions are disabled,
+// which is safe — the UI treats a nil GetFooter as "no footer".
+func footerProviderForUI(k *kit.Kit) func() *ui.WidgetData {
+	if !k.HasExtensions() {
+		return nil
+	}
+	return func() *ui.WidgetData {
+		config := k.GetExtensionFooter()
+		if config == nil {
+			return nil
+		}
+		return &ui.WidgetData{
+			Text:        config.Content.Text,
+			Markdown:    config.Content.Markdown,
+			BorderColor: config.Style.BorderColor,
+			NoBorder:    config.Style.NoBorder,
+		}
+	}
+}
+
 func runNormalMode(ctx context.Context) error {
 	// Validate flag combinations
 	if quietFlag && promptFlag == "" {
@@ -464,6 +506,22 @@ func runNormalMode(ctx context.Context) error {
 				kitInstance.RemoveExtensionWidget(id)
 				appInstance.NotifyWidgetUpdate()
 			},
+			SetHeader: func(config extensions.HeaderFooterConfig) {
+				kitInstance.SetExtensionHeader(config)
+				appInstance.NotifyWidgetUpdate()
+			},
+			RemoveHeader: func() {
+				kitInstance.RemoveExtensionHeader()
+				appInstance.NotifyWidgetUpdate()
+			},
+			SetFooter: func(config extensions.HeaderFooterConfig) {
+				kitInstance.SetExtensionFooter(config)
+				appInstance.NotifyWidgetUpdate()
+			},
+			RemoveFooter: func() {
+				kitInstance.RemoveExtensionFooter()
+				appInstance.NotifyWidgetUpdate()
+			},
 			PromptSelect: func(config extensions.PromptSelectConfig) extensions.PromptSelectResult {
 				ch := make(chan app.PromptResponse, 1)
 				appInstance.SendPromptRequest(app.PromptRequestEvent{
@@ -537,9 +595,14 @@ func runNormalMode(ctx context.Context) error {
 		})
 	}
 
+	// Build extension UI providers once (shared between both modes).
+	getWidgets := widgetProviderForUI(kitInstance)
+	getHeader := headerProviderForUI(kitInstance)
+	getFooter := footerProviderForUI(kitInstance)
+
 	// Check if running in non-interactive mode
 	if promptFlag != "" {
-		return runNonInteractiveModeApp(ctx, appInstance, cli, promptFlag, quietFlag, noExitFlag, modelName, parsedProvider, kitInstance.GetLoadingMessage(), serverNames, toolNames, mcpToolCount, extensionToolCount, usageTracker, extCommands, contextPaths, skillItems, widgetProviderForUI(kitInstance))
+		return runNonInteractiveModeApp(ctx, appInstance, cli, promptFlag, quietFlag, noExitFlag, modelName, parsedProvider, kitInstance.GetLoadingMessage(), serverNames, toolNames, mcpToolCount, extensionToolCount, usageTracker, extCommands, contextPaths, skillItems, getWidgets, getHeader, getFooter)
 	}
 
 	// Quiet mode is not allowed in interactive mode
@@ -547,7 +610,7 @@ func runNormalMode(ctx context.Context) error {
 		return fmt.Errorf("--quiet flag can only be used with --prompt/-p")
 	}
 
-	return runInteractiveModeBubbleTea(ctx, appInstance, modelName, parsedProvider, kitInstance.GetLoadingMessage(), serverNames, toolNames, mcpToolCount, extensionToolCount, usageTracker, extCommands, contextPaths, skillItems, widgetProviderForUI(kitInstance))
+	return runInteractiveModeBubbleTea(ctx, appInstance, modelName, parsedProvider, kitInstance.GetLoadingMessage(), serverNames, toolNames, mcpToolCount, extensionToolCount, usageTracker, extCommands, contextPaths, skillItems, getWidgets, getHeader, getFooter)
 }
 
 // runNonInteractiveModeApp executes a single prompt via the app layer and exits,
@@ -560,7 +623,7 @@ func runNormalMode(ctx context.Context) error {
 //
 // When --no-exit is set, after the prompt completes the interactive BubbleTea
 // TUI is started so the user can continue the conversation.
-func runNonInteractiveModeApp(ctx context.Context, appInstance *app.App, cli *ui.CLI, prompt string, quiet, noExit bool, modelName, providerName, loadingMessage string, serverNames, toolNames []string, mcpToolCount, extensionToolCount int, usageTracker *ui.UsageTracker, extCommands []ui.ExtensionCommand, contextPaths []string, skillItems []ui.SkillItem, getWidgets func(string) []ui.WidgetData) error {
+func runNonInteractiveModeApp(ctx context.Context, appInstance *app.App, cli *ui.CLI, prompt string, quiet, noExit bool, modelName, providerName, loadingMessage string, serverNames, toolNames []string, mcpToolCount, extensionToolCount int, usageTracker *ui.UsageTracker, extCommands []ui.ExtensionCommand, contextPaths []string, skillItems []ui.SkillItem, getWidgets func(string) []ui.WidgetData, getHeader, getFooter func() *ui.WidgetData) error {
 	if quiet {
 		// Quiet mode: no intermediate display, just print final response.
 		if err := appInstance.RunOnce(ctx, prompt); err != nil {
@@ -586,7 +649,7 @@ func runNonInteractiveModeApp(ctx context.Context, appInstance *app.App, cli *ui
 
 	// If --no-exit was requested, hand off to the interactive TUI.
 	if noExit {
-		return runInteractiveModeBubbleTea(ctx, appInstance, modelName, providerName, loadingMessage, serverNames, toolNames, mcpToolCount, extensionToolCount, usageTracker, extCommands, contextPaths, skillItems, getWidgets)
+		return runInteractiveModeBubbleTea(ctx, appInstance, modelName, providerName, loadingMessage, serverNames, toolNames, mcpToolCount, extensionToolCount, usageTracker, extCommands, contextPaths, skillItems, getWidgets, getHeader, getFooter)
 	}
 
 	return nil
@@ -603,7 +666,7 @@ func runNonInteractiveModeApp(ctx context.Context, appInstance *app.App, cli *ui
 //  4. Calls program.Run() which blocks until the user quits (Ctrl+C or /quit).
 //
 // SetupCLI is not used for interactive mode; the TUI (AppModel) handles its own rendering.
-func runInteractiveModeBubbleTea(_ context.Context, appInstance *app.App, modelName, providerName, loadingMessage string, serverNames, toolNames []string, mcpToolCount, extensionToolCount int, usageTracker *ui.UsageTracker, extCommands []ui.ExtensionCommand, contextPaths []string, skillItems []ui.SkillItem, getWidgets func(string) []ui.WidgetData) error {
+func runInteractiveModeBubbleTea(_ context.Context, appInstance *app.App, modelName, providerName, loadingMessage string, serverNames, toolNames []string, mcpToolCount, extensionToolCount int, usageTracker *ui.UsageTracker, extCommands []ui.ExtensionCommand, contextPaths []string, skillItems []ui.SkillItem, getWidgets func(string) []ui.WidgetData, getHeader, getFooter func() *ui.WidgetData) error {
 	// Determine terminal size; fall back gracefully.
 	termWidth, termHeight, err := term.GetSize(int(os.Stdout.Fd()))
 	if err != nil || termWidth == 0 {
@@ -627,6 +690,8 @@ func runInteractiveModeBubbleTea(_ context.Context, appInstance *app.App, modelN
 		ContextPaths:       contextPaths,
 		SkillItems:         skillItems,
 		GetWidgets:         getWidgets,
+		GetHeader:          getHeader,
+		GetFooter:          getFooter,
 	})
 
 	// Print startup info to stdout before Bubble Tea takes over the screen.

examples/extensions/header-footer-demo.go

@@ -0,0 +1,120 @@
+//go:build ignore
+
+package main
+
+import (
+	"fmt"
+	"time"
+
+	"kit/ext"
+)
+
+// Init demonstrates the custom header/footer system. The header shows
+// project context (branch, CWD) and the footer shows a running summary
+// of agent activity. Slash commands toggle them on/off.
+func Init(api ext.API) {
+	var turnCount int
+	var lastResponse string
+
+	// Show a custom header with project context when the session starts.
+	api.OnSessionStart(func(_ ext.SessionStartEvent, ctx ext.Context) {
+		ctx.SetHeader(ext.HeaderFooterConfig{
+			Content: ext.WidgetContent{
+				Text: fmt.Sprintf("Project: %s  |  Model: %s  |  %s",
+					ctx.CWD, ctx.Model, time.Now().Format("Jan 2, 15:04")),
+			},
+			Style: ext.WidgetStyle{
+				BorderColor: "#89b4fa",
+			},
+		})
+
+		ctx.SetFooter(ext.HeaderFooterConfig{
+			Content: ext.WidgetContent{
+				Text: "Ready  |  0 turns",
+			},
+			Style: ext.WidgetStyle{
+				BorderColor: "#a6e3a1",
+			},
+		})
+	})
+
+	// Update footer after each agent turn with activity summary.
+	api.OnAgentEnd(func(ae ext.AgentEndEvent, ctx ext.Context) {
+		turnCount++
+		lastResponse = ae.Response
+		if len(lastResponse) > 60 {
+			lastResponse = lastResponse[:57] + "..."
+		}
+
+		ctx.SetFooter(ext.HeaderFooterConfig{
+			Content: ext.WidgetContent{
+				Text: fmt.Sprintf("Turns: %d  |  Last: %s  |  %s",
+					turnCount, ae.StopReason, time.Now().Format("15:04:05")),
+			},
+			Style: ext.WidgetStyle{
+				BorderColor: "#a6e3a1",
+			},
+		})
+	})
+
+	// /header-off — remove the custom header.
+	api.RegisterCommand(ext.CommandDef{
+		Name:        "header-off",
+		Description: "Remove the custom header",
+		Execute: func(_ string, ctx ext.Context) (string, error) {
+			ctx.RemoveHeader()
+			return "Header removed.", nil
+		},
+	})
+
+	// /header-on — restore the custom header.
+	api.RegisterCommand(ext.CommandDef{
+		Name:        "header-on",
+		Description: "Restore the custom header",
+		Execute: func(_ string, ctx ext.Context) (string, error) {
+			ctx.SetHeader(ext.HeaderFooterConfig{
+				Content: ext.WidgetContent{
+					Text: fmt.Sprintf("Project: %s  |  Model: %s  |  %s",
+						ctx.CWD, ctx.Model, time.Now().Format("Jan 2, 15:04")),
+				},
+				Style: ext.WidgetStyle{
+					BorderColor: "#89b4fa",
+				},
+			})
+			return "Header restored.", nil
+		},
+	})
+
+	// /footer-off — remove the custom footer.
+	api.RegisterCommand(ext.CommandDef{
+		Name:        "footer-off",
+		Description: "Remove the custom footer",
+		Execute: func(_ string, ctx ext.Context) (string, error) {
+			ctx.RemoveFooter()
+			return "Footer removed.", nil
+		},
+	})
+
+	// /footer-on — restore the custom footer.
+	api.RegisterCommand(ext.CommandDef{
+		Name:        "footer-on",
+		Description: "Restore the custom footer",
+		Execute: func(_ string, ctx ext.Context) (string, error) {
+			ctx.SetFooter(ext.HeaderFooterConfig{
+				Content: ext.WidgetContent{
+					Text: fmt.Sprintf("Turns: %d  |  %s", turnCount, time.Now().Format("15:04:05")),
+				},
+				Style: ext.WidgetStyle{
+					BorderColor: "#a6e3a1",
+				},
+			})
+			return "Footer restored.", nil
+		},
+	})
+
+	// Clean up on shutdown.
+	api.OnSessionShutdown(func(_ ext.SessionShutdownEvent, ctx ext.Context) {
+		ctx.RemoveHeader()
+		ctx.RemoveFooter()
+	})
+}

internal/extensions/api.go

@@ -83,6 +83,38 @@ type Context struct {
 	// the ID does not exist.
 	RemoveWidget func(id string)
 
+	// SetHeader places a custom header at the top of the TUI view, above
+	// the stream region. Only one header can be active at a time; calling
+	// SetHeader replaces any previous header. The header persists across
+	// agent turns until explicitly removed.
+	//
+	// Example:
+	//
+	//   ctx.SetHeader(ext.HeaderFooterConfig{
+	//       Content: ext.WidgetContent{Text: "Project: my-app | Branch: main"},
+	//       Style:   ext.WidgetStyle{BorderColor: "#89b4fa"},
+	//   })
+	SetHeader func(HeaderFooterConfig)
+
+	// RemoveHeader removes the custom header. No-op if no header is set.
+	RemoveHeader func()
+
+	// SetFooter places a custom footer at the bottom of the TUI view,
+	// below the status bar. Only one footer can be active at a time;
+	// calling SetFooter replaces any previous footer. The footer persists
+	// across agent turns until explicitly removed.
+	//
+	// Example:
+	//
+	//   ctx.SetFooter(ext.HeaderFooterConfig{
+	//       Content: ext.WidgetContent{Text: "Ready | 3 tasks remaining"},
+	//       Style:   ext.WidgetStyle{BorderColor: "#a6e3a1"},
+	//   })
+	SetFooter func(HeaderFooterConfig)
+
+	// RemoveFooter removes the custom footer. No-op if no footer is set.
+	RemoveFooter func()
+
 	// PromptSelect shows a selection list to the user and blocks until
 	// they pick an option or cancel (ESC). Returns a cancelled result in
 	// non-interactive mode. Safe to call from event handlers and slash
@@ -369,6 +401,22 @@ type PromptInputResult struct {
 	Cancelled bool
 }
 
+// ---------------------------------------------------------------------------
+// Header/Footer types (exposed to Yaegi — concrete structs)
+// ---------------------------------------------------------------------------
+
+// HeaderFooterConfig describes a custom header or footer region that replaces
+// or augments the default TUI chrome. Extensions use ctx.SetHeader/SetFooter
+// to place one; only one header and one footer can be active at a time (the
+// latest call wins). Reuses WidgetContent and WidgetStyle for consistency.
+type HeaderFooterConfig struct {
+	// Content describes what to render.
+	Content WidgetContent
+
+	// Style configures the appearance.
+	Style WidgetStyle
+}
+
 // ---------------------------------------------------------------------------
 // ToolDef / CommandDef
 // ---------------------------------------------------------------------------

internal/extensions/runner.go

@@ -15,6 +15,8 @@ type Runner struct {
 	extensions []LoadedExtension
 	ctx        Context
 	widgets    map[string]WidgetConfig // keyed by widget ID
+	header     *HeaderFooterConfig     // nil = no custom header
+	footer     *HeaderFooterConfig     // nil = no custom footer
 	mu         sync.RWMutex
 }
 
@@ -173,6 +175,64 @@ func (r *Runner) GetWidgets(placement WidgetPlacement) []WidgetConfig {
 	return result
 }
 
+// ---------------------------------------------------------------------------
+// Header/Footer management
+// ---------------------------------------------------------------------------
+
+// SetHeader places or replaces the custom header. Thread-safe.
+func (r *Runner) SetHeader(config HeaderFooterConfig) {
+	r.mu.Lock()
+	defer r.mu.Unlock()
+	r.header = &config
+}
+
+// RemoveHeader removes the custom header. No-op if none is set. Thread-safe.
+func (r *Runner) RemoveHeader() {
+	r.mu.Lock()
+	defer r.mu.Unlock()
+	r.header = nil
+}
+
+// GetHeader returns the current custom header, or nil if none is set.
+// Thread-safe.
+func (r *Runner) GetHeader() *HeaderFooterConfig {
+	r.mu.RLock()
+	defer r.mu.RUnlock()
+	if r.header == nil {
+		return nil
+	}
+	// Return a copy to avoid races on the caller side.
+	h := *r.header
+	return &h
+}
+
+// SetFooter places or replaces the custom footer. Thread-safe.
+func (r *Runner) SetFooter(config HeaderFooterConfig) {
+	r.mu.Lock()
+	defer r.mu.Unlock()
+	r.footer = &config
+}
+
+// RemoveFooter removes the custom footer. No-op if none is set. Thread-safe.
+func (r *Runner) RemoveFooter() {
+	r.mu.Lock()
+	defer r.mu.Unlock()
+	r.footer = nil
+}
+
+// GetFooter returns the current custom footer, or nil if none is set.
+// Thread-safe.
+func (r *Runner) GetFooter() *HeaderFooterConfig {
+	r.mu.RLock()
+	defer r.mu.RUnlock()
+	if r.footer == nil {
+		return nil
+	}
+	// Return a copy to avoid races on the caller side.
+	f := *r.footer
+	return &f
+}
+
 // ---------------------------------------------------------------------------
 // Helpers
 // ---------------------------------------------------------------------------

internal/extensions/symbols.go

@@ -34,6 +34,9 @@ func Symbols() interp.Exports {
 			"WidgetAbove":     reflect.ValueOf(WidgetAbove),
 			"WidgetBelow":     reflect.ValueOf(WidgetBelow),
 
+			// Header/Footer types
+			"HeaderFooterConfig": reflect.ValueOf((*HeaderFooterConfig)(nil)),
+
 			// Prompt types
 			"PromptSelectConfig":  reflect.ValueOf((*PromptSelectConfig)(nil)),
 			"PromptSelectResult":  reflect.ValueOf((*PromptSelectResult)(nil)),

internal/ui/model.go

@@ -146,6 +146,16 @@ type AppModelOptions struct {
 	// ("above" or "below"). Called during View() to render persistent
 	// extension widgets. May be nil if no extensions are loaded.
 	GetWidgets func(placement string) []WidgetData
+
+	// GetHeader returns the current custom header set by an extension, or
+	// nil if no header is active. Called during View() to render a
+	// persistent header above the stream region. May be nil.
+	GetHeader func() *WidgetData
+
+	// GetFooter returns the current custom footer set by an extension, or
+	// nil if no footer is active. Called during View() to render a
+	// persistent footer below the status bar. May be nil.
+	GetFooter func() *WidgetData
 }
 
 // AppModel is the root Bubble Tea model for the interactive TUI. It owns the
@@ -155,13 +165,17 @@ type AppModelOptions struct {
 //
 // Layout (stacked, no alt screen):
 //
-//	┌─ stream region (variable height) ─────────────────┐
+//	┌─ [custom header] (optional, from extension) ──────┐
+//	├─ stream region (variable height) ─────────────────┤
 //	│                                                    │
 //	├─ separator line (with optional queue count) ───────┤
+//	│  [above widgets]                                   │
 //	│  queued  How do I fix the build?                   │
 //	│  queued  Also check the tests                      │
 //	├─ input region (fixed height from textarea) ────────┤
+//	│  [below widgets]                                   │
 //	│ Tokens: 23.4K (12%) | Cost: $0.00  provider·model │
+//	├─ [custom footer] (optional, from extension) ──────┤
 //	└────────────────────────────────────────────────────┘
 //
 // The status bar is always present (1 line) to avoid layout shifts that
@@ -240,6 +254,12 @@ type AppModel struct {
 	// getWidgets returns extension widgets for a given placement. May be nil.
 	getWidgets func(placement string) []WidgetData
 
+	// getHeader returns the current custom header. May be nil.
+	getHeader func() *WidgetData
+
+	// getFooter returns the current custom footer. May be nil.
+	getFooter func() *WidgetData
+
 	// prompt holds the state of an active interactive prompt overlay. Nil
 	// when no prompt is active. Managed by updatePromptState().
 	prompt *promptOverlay
@@ -333,6 +353,8 @@ func NewAppModel(appCtrl AppController, opts AppModelOptions) *AppModel {
 	// Store extension commands for dispatch.
 	m.extensionCommands = opts.ExtensionCommands
 	m.getWidgets = opts.GetWidgets
+	m.getHeader = opts.GetHeader
+	m.getFooter = opts.GetFooter
 
 	// Store context/skills metadata and tool counts for startup display.
 	m.contextPaths = opts.ContextPaths
@@ -852,10 +874,17 @@ func (m *AppModel) View() tea.View {
 	}
 	statusBar := m.renderStatusBar()
 
+	// Build the stacked layout. Optional header/footer wrap the core layout.
+	var parts []string
+
+	// Custom header (if set by extension) — above everything.
+	if headerView := m.renderHeaderFooter(m.getHeader); headerView != "" {
+		parts = append(parts, headerView)
+	}
+
 	// Only include the stream region when it has content. When idle the
 	// stream renders "" which JoinVertical would pad to a full-width blank
 	// line, inflating the view unnecessarily.
-	var parts []string
 	if streamView != "" {
 		parts = append(parts, streamView)
 	}
@@ -879,6 +908,11 @@ func (m *AppModel) View() tea.View {
 
 	parts = append(parts, statusBar)
 
+	// Custom footer (if set by extension) — below everything.
+	if footerView := m.renderHeaderFooter(m.getFooter); footerView != "" {
+		parts = append(parts, footerView)
+	}
+
 	content := lipgloss.JoinVertical(lipgloss.Left, parts...)
 
 	return tea.NewView(content)
@@ -1019,6 +1053,40 @@ func (m *AppModel) renderWidgetSlot(placement string) string {
 	return strings.Join(blocks, "\n")
 }
 
+// renderHeaderFooter renders a custom header or footer from an extension. The
+// getter function returns the current data (*WidgetData) or nil when inactive.
+// Returns "" when the getter is nil or returns nil. Uses the same rendering
+// pipeline as widgets for visual consistency.
+func (m *AppModel) renderHeaderFooter(getter func() *WidgetData) string {
+	if getter == nil {
+		return ""
+	}
+	data := getter()
+	if data == nil {
+		return ""
+	}
+
+	theme := GetTheme()
+
+	var opts []renderingOption
+	opts = append(opts, WithAlign(lipgloss.Left))
+
+	if data.NoBorder {
+		opts = append(opts, WithNoBorder())
+	} else {
+		borderClr := theme.Accent
+		if data.BorderColor != "" {
+			borderClr = lipgloss.Color(data.BorderColor)
+		}
+		opts = append(opts, WithBorderColor(borderClr))
+	}
+
+	// Compact padding like widgets.
+	opts = append(opts, WithPaddingTop(0), WithPaddingBottom(0))
+
+	return renderContentBlock(data.Text, m.width, opts...)
+}
+
 // renderQueuedMessages renders queued prompts as styled content blocks with a
 // "QUEUED" badge, anchored between the separator and input. Each message is
 // displayed in a bordered block matching the overall message styling.
@@ -1392,13 +1460,15 @@ func (m *AppModel) flushStreamContent() tea.Cmd {
 //
 // Layout (line counts):
 //
-//	stream region  = total - separator(1) - widgets - queued(N*5) - input(measured) - widgets - statusBar(1)
+//	header         = measured dynamically (0 if not set)
+//	stream region  = total - header - separator(1) - widgets - queued(N*5) - input(measured) - widgets - statusBar(1) - footer
 //	separator      = 1 line
 //	above widgets  = measured dynamically
 //	queued msgs    = ~5 lines per message (padding + text + badge + padding)
 //	input region   = measured dynamically via lipgloss.Height()
 //	below widgets  = measured dynamically
 //	status bar     = 1 line (always present)
+//	footer         = measured dynamically (0 if not set)
 func (m *AppModel) distributeHeight() {
 	const separatorLines = 1
 	const statusBarLines = 1 // always-present status bar
@@ -1427,7 +1497,16 @@ func (m *AppModel) distributeHeight() {
 		widgetLines += lipgloss.Height(below)
 	}
 
-	streamHeight := max(m.height-separatorLines-widgetLines-queuedLines-inputLines-statusBarLines, 0)
+	// Measure header/footer heights.
+	var headerFooterLines int
+	if headerView := m.renderHeaderFooter(m.getHeader); headerView != "" {
+		headerFooterLines += lipgloss.Height(headerView)
+	}
+	if footerView := m.renderHeaderFooter(m.getFooter); footerView != "" {
+		headerFooterLines += lipgloss.Height(footerView)
+	}
+
+	streamHeight := max(m.height-separatorLines-widgetLines-headerFooterLines-queuedLines-inputLines-statusBarLines, 0)
 
 	if m.stream != nil {
 		m.stream.SetHeight(streamHeight)

pkg/kit/kit.go

@@ -169,6 +169,56 @@ func (m *Kit) GetExtensionWidgets(placement extensions.WidgetPlacement) []extens
 	return m.extRunner.GetWidgets(placement)
 }
 
+// SetExtensionHeader places or replaces the custom header from extensions.
+// Delegates to the extension runner. No-op if extensions are disabled.
+func (m *Kit) SetExtensionHeader(config extensions.HeaderFooterConfig) {
+	if m.extRunner != nil {
+		m.extRunner.SetHeader(config)
+	}
+}
+
+// RemoveExtensionHeader removes the custom extension header.
+// Delegates to the extension runner. No-op if extensions are disabled.
+func (m *Kit) RemoveExtensionHeader() {
+	if m.extRunner != nil {
+		m.extRunner.RemoveHeader()
+	}
+}
+
+// GetExtensionHeader returns the current custom header, or nil if none is set.
+// Returns nil if extensions are disabled.
+func (m *Kit) GetExtensionHeader() *extensions.HeaderFooterConfig {
+	if m.extRunner == nil {
+		return nil
+	}
+	return m.extRunner.GetHeader()
+}
+
+// SetExtensionFooter places or replaces the custom footer from extensions.
+// Delegates to the extension runner. No-op if extensions are disabled.
+func (m *Kit) SetExtensionFooter(config extensions.HeaderFooterConfig) {
+	if m.extRunner != nil {
+		m.extRunner.SetFooter(config)
+	}
+}
+
+// RemoveExtensionFooter removes the custom extension footer.
+// Delegates to the extension runner. No-op if extensions are disabled.
+func (m *Kit) RemoveExtensionFooter() {
+	if m.extRunner != nil {
+		m.extRunner.RemoveFooter()
+	}
+}
+
+// GetExtensionFooter returns the current custom footer, or nil if none is set.
+// Returns nil if extensions are disabled.
+func (m *Kit) GetExtensionFooter() *extensions.HeaderFooterConfig {
+	if m.extRunner == nil {
+		return nil
+	}
+	return m.extRunner.GetFooter()
+}
+
 // HasExtensions returns true if the extension runner is configured and active.
 func (m *Kit) HasExtensions() bool {
 	return m.extRunner != nil