diff --git a/cmd/riptide/main.go b/cmd/riptide/main.go
index 7f96256..47afb8c 100644
--- a/cmd/riptide/main.go
+++ b/cmd/riptide/main.go
@@ -54,8 +54,10 @@ func main() {
 	t := theme.Get(themeName)
 
 	lipgloss.SetHasDarkBackground(true)
-	fmt.Fprint(os.Stdout, "\x1b]11;"+t.HexBG()+"\a")
-	fmt.Fprint(os.Stdout, "\x1b]10;"+t.HexFG()+"\a")
+	if !t.IsTransparent() {
+		fmt.Fprint(os.Stdout, "\x1b]11;"+t.HexBG()+"\a")
+		fmt.Fprint(os.Stdout, "\x1b]10;"+t.HexFG()+"\a")
+	}
 	defer func() {
 		fmt.Fprint(os.Stdout, "\x1b]111\a\x1b]110\a")
 	}()
diff --git a/internal/theme/theme.go b/internal/theme/theme.go
index b738f55..7bd5af7 100644
--- a/internal/theme/theme.go
+++ b/internal/theme/theme.go
@@ -95,6 +95,7 @@ var DefaultTheme = Theme{
 // All is every built-in palette, default first.
 var All = []Theme{
 	DefaultTheme,
+	SystemTheme,
 	oceanTheme,
 	midnightTheme,
 	sunsetTheme,
@@ -150,16 +151,41 @@ func PaintScreen(t Theme, width, height int, content string) string {
 	if height <= 0 {
 		height = 24
 	}
+
+	if !t.IsTransparent() {
+		lines := strings.Split(content, "\n")
+		bg := lipgloss.NewStyle().Background(t.AppBg)
+		for i, line := range lines {
+			lines[i] = bg.Render(line)
+		}
+		content = strings.Join(lines, "\n")
+
+		return lipgloss.Place(
+			width, height,
+			lipgloss.Center, lipgloss.Center,
+			content,
+			lipgloss.WithWhitespaceBackground(t.AppBg),
+		)
+	}
 	return lipgloss.Place(
 		width, height,
 		lipgloss.Center, lipgloss.Center,
 		content,
-		lipgloss.WithWhitespaceBackground(t.AppBg),
 	)
 }
 
-// Hex returns the AppBg as a #rrggbb string for OSC sequences.
+// IsTransparent returns true when the theme uses a transparent canvas so
+// callers can skip background fills / OSC sequences.
+func (t Theme) IsTransparent() bool {
+	return t.AppBg == ""
+}
+
+// HexBG returns the AppBg as a #rrggbb string for OSC sequences.
+// Returns empty string for transparent themes (caller should skip OSC).
 func (t Theme) HexBG() string {
+	if t.IsTransparent() {
+		return ""
+	}
 	s := string(t.AppBg)
 	if s == "" {
 		return "#191a1b"
@@ -168,14 +194,56 @@ func (t Theme) HexBG() string {
 }
 
 // HexFG returns a concrete foreground for OSC sequences.
+// Returns empty string for transparent themes (caller should skip OSC).
 func (t Theme) HexFG() string {
+	if t.IsTransparent() {
+		return ""
+	}
 	if t.AccentDL != "" {
-		// Prefer a soft off-white derived from foreground dark branch.
 		return "#e8eaed"
 	}
 	return "#e8eaed"
 }
 
+// SystemTheme uses the terminal's native color palette with transparent
+// background. IsTransparent() identifies it by Name=="system". Accent colors
+// reference ANSI palette numbers (0-15) so they inherit whatever colors the
+// terminal emulator has configured. Background fills are left empty for
+// transparency so the terminal canvas shows through.
+var SystemTheme = Theme{
+	Name:    "system",
+	Display: "System",
+	Tagline: "Terminal native colors",
+
+	AppBg: lipgloss.Color(""),
+
+	Foreground: lipgloss.AdaptiveColor{},
+	Muted:      lipgloss.AdaptiveColor{Light: "8", Dark: "8"},
+	Border:     lipgloss.AdaptiveColor{Light: "7", Dark: "8"},
+	Download:   lipgloss.AdaptiveColor{Light: "6", Dark: "6"},
+	Upload:     lipgloss.AdaptiveColor{Light: "3", Dark: "3"},
+	Latency:    lipgloss.AdaptiveColor{Light: "5", Dark: "5"},
+	Highlight:  lipgloss.AdaptiveColor{Light: "2", Dark: "2"},
+
+	GraphDownBottom: lipgloss.Color("6"),
+	GraphDownTop:    lipgloss.Color("6"),
+	GraphUpBottom:   lipgloss.Color("3"),
+	GraphUpTop:      lipgloss.Color("3"),
+
+	MenuAccentFill: lipgloss.AdaptiveColor{},
+
+	MenuIdleFill:   lipgloss.Color(""),
+	MenuSelectDL:   lipgloss.Color(""),
+	MenuSelectUL:   lipgloss.Color(""),
+	MenuSelectExit: lipgloss.Color(""),
+	MenuSelectSet:  lipgloss.Color(""),
+
+	AccentDL:  lipgloss.Color("6"),
+	AccentUL:  lipgloss.Color("3"),
+	AccentLat: lipgloss.Color("5"),
+	AccentHL:  lipgloss.Color("2"),
+}
+
 // --- Built-in palettes ---------------------------------------------------
 
 var oceanTheme = Theme{
diff --git a/internal/ui/app.go b/internal/ui/app.go
index ea74f63..5a78210 100644
--- a/internal/ui/app.go
+++ b/internal/ui/app.go
@@ -106,7 +106,13 @@ func (a *App) enter(s screenID) tea.Cmd {
 func (a *App) applyTheme(name string) {
 	t := apptheme.Get(name)
 	a.theme = t
-	fmt.Fprint(os.Stdout, "\x1b]11;"+t.HexBG()+"\a")
+	if t.IsTransparent() {
+		fmt.Fprint(os.Stdout, "\x1b]111\a\x1b]110\a")
+	} else {
+		fmt.Fprint(os.Stdout, "\x1b]11;"+t.HexBG()+"\a")
+		fmt.Fprint(os.Stdout, "\x1b]10;"+t.HexFG()+"\a")
+	}
+
 	if a.menu != nil {
 		a.menu.applyTheme(t)
 	}
@@ -117,18 +123,26 @@ func (a *App) applyTheme(name string) {
 		a.test.theme = t
 		if a.test.dlGraph != nil {
 			a.test.dlGraph.bottom, a.test.dlGraph.top = t.GraphDownBottom, t.GraphDownTop
+			a.test.dlGraph.bg = t.AppBg
+			a.test.dlGraph.grid = gridColor(t, t.GraphDownBottom)
 		}
 		if a.test.ulGraph != nil {
 			a.test.ulGraph.bottom, a.test.ulGraph.top = t.GraphUpBottom, t.GraphUpTop
+			a.test.ulGraph.bg = t.AppBg
+			a.test.ulGraph.grid = gridColor(t, t.GraphUpBottom)
 		}
 	}
 	if a.monitor != nil {
 		a.monitor.theme = t
 		if a.monitor.dlGraph != nil {
 			a.monitor.dlGraph.bottom, a.monitor.dlGraph.top = t.GraphDownBottom, t.GraphDownTop
+			a.monitor.dlGraph.bg = t.AppBg
+			a.monitor.dlGraph.grid = gridColor(t, t.GraphDownBottom)
 		}
 		if a.monitor.ulGraph != nil {
 			a.monitor.ulGraph.bottom, a.monitor.ulGraph.top = t.GraphUpBottom, t.GraphUpTop
+			a.monitor.ulGraph.bg = t.AppBg
+			a.monitor.ulGraph.grid = gridColor(t, t.GraphUpBottom)
 		}
 	}
 }
diff --git a/internal/ui/card.go b/internal/ui/card.go
index 85feea7..5772740 100644
--- a/internal/ui/card.go
+++ b/internal/ui/card.go
@@ -119,6 +119,17 @@ type cardState struct {
 	err error
 }
 
+// gridColor returns the color used for graph grid/peak lines.
+// For transparent themes (terminal native palette) it returns ANSI 8 (gray)
+// since hex-based dimming cannot target ANSI palette numbers. For all other
+// themes it returns a faint blend of bottom blended toward the canvas.
+func gridColor(theme apptheme.Theme, bottom lipgloss.Color) lipgloss.Color {
+	if theme.IsTransparent() {
+		return lipgloss.Color("8")
+	}
+	return dimColor(bottom, 0.28, theme.AppBg)
+}
+
 // newCardState builds the shared state for one run: spinner, channels, context,
 // and the two history graphs.
 func newCardState(theme apptheme.Theme, compact bool) *cardState {
@@ -142,8 +153,8 @@ func newCardState(theme apptheme.Theme, compact bool) *cardState {
 		events:   make(chan tea.Msg, 64),
 		spinner:  s,
 		phase:    engine.PhaseInit,
-		dlGraph:  newGraph(40, graphHeight, theme.GraphDownBottom, theme.GraphDownTop),
-		ulGraph:  newGraph(40, graphHeight, theme.GraphUpBottom, theme.GraphUpTop),
+		dlGraph:  newGraph(40, graphHeight, theme.GraphDownBottom, theme.GraphDownTop, theme.AppBg, gridColor(theme, theme.GraphDownBottom)),
+		ulGraph:  newGraph(40, graphHeight, theme.GraphUpBottom, theme.GraphUpTop, theme.AppBg, gridColor(theme, theme.GraphUpBottom)),
 	}
 }
 
@@ -485,22 +496,33 @@ var logoStops = [4][3]uint8{
 
 // renderHeader draws the RIPTIDE wordmark the same way flow draws FLOW:
 // pre-baked ANSI Shadow art + per-row 4-stop gradient + muted tagline.
-func renderHeader(tagline string) string {
+func renderHeader(theme apptheme.Theme, tagline string) string {
 	n := len(logoSrc)
 	lines := make([]string, n)
 	for i, line := range logoSrc {
-		rowT := 0.0
-		if n > 1 {
-			rowT = float64(i) / float64(n-1)
+		var color lipgloss.Color
+		if theme.IsTransparent() {
+			color = theme.AccentDL
+		} else {
+			rowT := 0.0
+			if n > 1 {
+				rowT = float64(i) / float64(n-1)
+			}
+			r, g, b := logoGradient(rowT)
+			color = lipgloss.Color(fmt.Sprintf("#%02x%02x%02x", r, g, b))
 		}
-		r, g, b := logoGradient(rowT)
-		color := lipgloss.Color(fmt.Sprintf("#%02x%02x%02x", r, g, b))
 		lines[i] = lipgloss.NewStyle().Foreground(color).Bold(true).Render(line)
 	}
 	logo := lipgloss.JoinVertical(lipgloss.Left, lines...)
 
+	var tagColor lipgloss.Color
+	if theme.IsTransparent() {
+		tagColor = theme.AccentHL
+	} else {
+		tagColor = lipgloss.Color("#94a3b8")
+	}
 	tag := lipgloss.NewStyle().
-		Foreground(lipgloss.Color("#94a3b8")).
+		Foreground(tagColor).
 		Render(tagline)
 
 	return lipgloss.JoinVertical(lipgloss.Center, logo, "", tag)
@@ -532,9 +554,15 @@ func lerpU8(a, b uint8, t float64) uint8 {
 
 // renderCompactHeader draws a minimal header: just the tagline text without the
 // large pixel-art logo. Used when --compact mode is active or toggled with 't'.
-func renderCompactHeader(tagline string) string {
+func renderCompactHeader(theme apptheme.Theme, tagline string) string {
+	var color lipgloss.Color
+	if theme.IsTransparent() {
+		color = theme.AccentDL
+	} else {
+		color = lipgloss.Color("#56d364")
+	}
 	tag := lipgloss.NewStyle().
-		Foreground(lipgloss.Color("#56d364")).
+		Foreground(color).
 		Bold(true).
 		Render(tagline)
 	return tag
diff --git a/internal/ui/menu.go b/internal/ui/menu.go
index 6bb5b60..d6149c0 100644
--- a/internal/ui/menu.go
+++ b/internal/ui/menu.go
@@ -488,9 +488,9 @@ func (m *menuModel) View() string {
 
 	var header string
 	if m.compact {
-		header = renderCompactHeader("Choose how you'd like to measure your connection")
+		header = renderCompactHeader(m.theme, "Choose how you'd like to measure your connection")
 	} else {
-		header = renderHeader("Choose how you'd like to measure your connection")
+		header = renderHeader(m.theme, "Choose how you'd like to measure your connection")
 	}
 
 	rule := lipgloss.NewStyle().Foreground(m.theme.Border).Render(strings.Repeat("─", 36))
diff --git a/internal/ui/model.go b/internal/ui/model.go
index 1e721f0..1ba625a 100644
--- a/internal/ui/model.go
+++ b/internal/ui/model.go
@@ -428,9 +428,9 @@ func (m *model) View() string {
 
 	var header string
 	if m.compact {
-		header = renderCompactHeader("Wonder how speedy your internet is?")
+		header = renderCompactHeader(m.theme, "Wonder how speedy your internet is?")
 	} else {
-		header = renderHeader("Wonder how speedy your internet is?")
+		header = renderHeader(m.theme, "Wonder how speedy your internet is?")
 	}
 
 	var main string
diff --git a/internal/ui/monitor.go b/internal/ui/monitor.go
index d274f8d..b2996d0 100644
--- a/internal/ui/monitor.go
+++ b/internal/ui/monitor.go
@@ -269,9 +269,9 @@ func (m *monitorModel) View() string {
 
 	var header string
 	if m.compact {
-		header = renderCompactHeader("Watching your connection in real time")
+		header = renderCompactHeader(m.theme, "Watching your connection in real time")
 	} else {
-		header = renderHeader("Watching your connection in real time")
+		header = renderHeader(m.theme, "Watching your connection in real time")
 	}
 
 	stack := lipgloss.JoinVertical(lipgloss.Center, header, "", card)
diff --git a/internal/ui/settings.go b/internal/ui/settings.go
index fe9bee1..3f8180b 100644
--- a/internal/ui/settings.go
+++ b/internal/ui/settings.go
@@ -601,7 +601,7 @@ func (m *settingsModel) View() string {
 	}
 
 	// Always compact title — full logo makes the page too tall.
-	header := renderCompactHeader("Settings  ·  Tune riptide to your taste")
+	header := renderCompactHeader(m.theme, "Settings  ·  Tune riptide to your taste")
 
 	search := m.viewSearch(cardW)
 
diff --git a/internal/ui/sparkline.go b/internal/ui/sparkline.go
index ae6dd2d..399d7fd 100644
--- a/internal/ui/sparkline.go
+++ b/internal/ui/sparkline.go
@@ -22,14 +22,18 @@ type graph struct {
 	data   []float64 // most-recent-last
 	bottom lipgloss.Color
 	top    lipgloss.Color
+	bg     lipgloss.Color // canvas background (for dimming)
+	grid   lipgloss.Color // muted color for grid/peak lines
 }
 
-func newGraph(width, height int, bottom, top lipgloss.Color) *graph {
+func newGraph(width, height int, bottom, top, bg, grid lipgloss.Color) *graph {
 	return &graph{
 		width:  width,
 		height: height,
 		bottom: bottom,
 		top:    top,
+		bg:     bg,
+		grid:   grid,
 	}
 }
 
@@ -132,8 +136,8 @@ func (g *graph) View() string {
 		peakRow = g.height - 1 - fromBottom
 	}
 
-	gridStyle := lipgloss.NewStyle().Foreground(dimColor(g.bottom, 0.28))
-	peakLineStyle := lipgloss.NewStyle().Foreground(dimColor(g.top, 0.40))
+	gridStyle := lipgloss.NewStyle().Foreground(g.grid)
+	peakLineStyle := lipgloss.NewStyle().Foreground(g.grid)
 
 	rows := make([]string, g.height)
 	for row := 0; row < g.height; row++ {
@@ -153,7 +157,7 @@ func (g *graph) View() string {
 			switch {
 			case lv >= rowBase+8:
 				// Solid body cell.
-				c := dimColor(rowColor, age)
+				c := dimColor(rowColor, age, g.bg)
 				if col == peakCol && row == peakRow {
 					c = peakSpark(g.top)
 				}
@@ -165,13 +169,13 @@ func (g *graph) View() string {
 				if partial > 8 {
 					partial = 8
 				}
-				c := dimColor(rowColor, age)
+				c := dimColor(rowColor, age, g.bg)
 				if col == peakCol {
 					c = peakSpark(g.top)
 				} else {
 					// Tips are a touch brighter than the body at this row.
 					c = lerpColor(c, g.top, 0.35)
-					c = dimColor(c, age)
+					c = dimColor(c, age, g.bg)
 				}
 				b.WriteString(lipgloss.NewStyle().Foreground(c).Render(string(barRamp[partial])))
 
@@ -194,7 +198,7 @@ func (g *graph) View() string {
 
 // renderEmpty draws a stable blank chart with a faint grid so layout never jumps.
 func (g *graph) renderEmpty() string {
-	gridStyle := lipgloss.NewStyle().Foreground(dimColor(g.bottom, 0.22))
+	gridStyle := lipgloss.NewStyle().Foreground(g.grid)
 	gridRow := make([]bool, g.height)
 	for _, frac := range []float64{0.25, 0.5, 0.75} {
 		fromBottom := int(math.Round(frac * float64(g.height-1)))
@@ -233,21 +237,28 @@ func (g *graph) ageFactor(col int) float64 {
 }
 
 // peakSpark returns a hot highlight color for the current peak tip.
+// When top is empty (terminal default), returns empty (terminal default).
 func peakSpark(top lipgloss.Color) lipgloss.Color {
+	if top == "" {
+		return ""
+	}
 	return lerpColor(top, lipgloss.Color("#f0f6fc"), 0.55)
 }
 
-// dimColor blends c toward near-black by keeping `amount` of the original
-// (amount 1 = full color, 0 = almost black).
-func dimColor(c lipgloss.Color, amount float64) lipgloss.Color {
-	if amount >= 0.999 {
+// dimColor blends c toward the canvas background bg by keeping `amount` of the
+// original (amount 1 = full color, 0 = matches bg). When bg is empty
+// (transparent theme) the color is returned unchanged.
+func dimColor(c lipgloss.Color, amount float64, bg lipgloss.Color) lipgloss.Color {
+	if amount >= 0.999 || c == "" {
 		return c
 	}
 	if amount < 0 {
 		amount = 0
 	}
-	// Blend toward the app canvas so empty graph cells match the UI chrome.
-	return lerpColor(lipgloss.Color("#191a1b"), c, amount)
+	if bg == "" {
+		return c
+	}
+	return lerpColor(bg, c, amount)
 }
 
 // easeOutQuad pushes more of the gradient toward the bright tip.
@@ -261,7 +272,9 @@ func easeOutQuad(t float64) float64 {
 	return 1 - (1-t)*(1-t)
 }
 
-// lerpColor blends from a to b by t in [0,1] in RGB space.
+// lerpColor blends from a to b by t in [0,1] in Lab space. When either color
+// is empty (terminal default), the non-empty one is returned (or empty if
+// both are empty).
 func lerpColor(a, b lipgloss.Color, t float64) lipgloss.Color {
 	if t < 0 {
 		t = 0
@@ -269,6 +282,15 @@ func lerpColor(a, b lipgloss.Color, t float64) lipgloss.Color {
 	if t > 1 {
 		t = 1
 	}
+	if a == "" && b == "" {
+		return ""
+	}
+	if a == "" {
+		return b
+	}
+	if b == "" {
+		return a
+	}
 	ca, errA := colorful.Hex(string(a))
 	cb, errB := colorful.Hex(string(b))
 	if errA != nil || errB != nil {