fix: log slow app update and render paths

Author: binarylogic

internal/app/app.go

@@ -4,6 +4,7 @@ package app
 import (
 	"context"
 	"fmt"
+	"time"
 
 	tea "charm.land/bubbletea/v2"
 
@@ -183,6 +184,9 @@ func (m *Model) checkForUpdate() tea.Cmd {
 
 // Update handles messages.
 func (m *Model) Update(msg tea.Msg) (tea.Model, tea.Cmd) {
+	start := time.Now()
+	defer m.logSlowUpdate(start, msg)
+
 	if cmd, handled := m.handleGlobalMessage(msg); handled {
 		return m, cmd
 	}

internal/app/app_layout_view.go

@@ -1,6 +1,8 @@
 package app
 
 import (
+	"time"
+
 	"charm.land/bubbles/v2/key"
 	tea "charm.land/bubbletea/v2"
 	"charm.land/lipgloss/v2"
@@ -84,6 +86,9 @@ func (m *Model) updateKeyBar() {
 
 // View renders the app.
 func (m *Model) View() tea.View {
+	start := time.Now()
+	defer m.logSlowRender(start)
+
 	colors := m.theme
 
 	// Show message if window is too small

internal/app/perf_logging.go

@@ -0,0 +1,68 @@
+package app
+
+import (
+	"fmt"
+	"time"
+)
+
+const (
+	slowUpdateInfoThreshold = 50 * time.Millisecond
+	slowUpdateWarnThreshold = 200 * time.Millisecond
+	slowRenderInfoThreshold = 50 * time.Millisecond
+	slowRenderWarnThreshold = 200 * time.Millisecond
+)
+
+func (m *Model) logSlowUpdate(start time.Time, msg any) {
+	d := time.Since(start)
+	if d < slowUpdateInfoThreshold {
+		return
+	}
+
+	args := m.perfLogArgs(d)
+	args = append(args, "msg_type", fmt.Sprintf("%T", msg))
+
+	if d >= slowUpdateWarnThreshold {
+		m.scope.Warn("slow app update", args...)
+		return
+	}
+	m.scope.Info("slow app update", args...)
+}
+
+func (m *Model) logSlowRender(start time.Time) {
+	d := time.Since(start)
+	if d < slowRenderInfoThreshold {
+		return
+	}
+
+	args := m.perfLogArgs(d)
+	if d >= slowRenderWarnThreshold {
+		m.scope.Warn("slow app render", args...)
+		return
+	}
+	m.scope.Info("slow app render", args...)
+}
+
+func (m *Model) perfLogArgs(d time.Duration) []any {
+	return []any{
+		"duration_ms", d.Milliseconds(),
+		"state", m.stateName(),
+		"width", m.width,
+		"height", m.height,
+		"drawer_open", m.statusBar.IsDrawerOpen(),
+		"drawer_tab", m.statusBar.ActiveTabLabel(),
+		"palette_open", m.palette != nil,
+		"quit_dialog_open", m.quitDlg != nil,
+	}
+}
+
+func (m *Model) stateName() string {
+	switch m.state {
+	case stateOnboarding:
+		return "onboarding"
+	case stateChat:
+		return "chat"
+	default:
+		return "unknown"
+	}
+}
+

internal/app/statusbar/statusbar_drawer.go

@@ -37,6 +37,15 @@ func (m *Model) IsDrawerOpen() bool {
 	return m.drawerOpen
 }
 
+// ActiveTabLabel returns the active drawer tab label.
+func (m *Model) ActiveTabLabel() string {
+	tab := m.activeTabModel()
+	if tab == nil {
+		return ""
+	}
+	return tab.Label()
+}
+
 // HandleKeyPress forwards key events to the active tab's key handler.
 func (m *Model) HandleKeyPress(msg tea.KeyPressMsg) tea.Cmd {
 	tab := m.activeTabModel()