diff --git a/system_monitor.go b/system_monitor.go
new file mode 100644
index 0000000..52f2ff2
--- /dev/null
+++ b/system_monitor.go
@@ -0,0 +1,76 @@
+package mujica
+
+import (
+	"fmt"
+	"math"
+	"time"
+
+	"github.com/egoist/mygo/ui"
+
+	"mujicaui/theme"
+)
+
+// MonitorMetric is one sampled resource; Samples line up with the shared times.
+type MonitorMetric struct {
+	Name    string
+	Unit    string
+	Samples []float64
+}
+
+// SystemMonitorOptions configure a SystemMonitor.
+type SystemMonitorOptions struct {
+	// Height of each chart; zero means 110.
+	Height float32
+	Status DataStatus
+	Error  string
+}
+
+// SystemMonitorResult reports this frame's events.
+type SystemMonitorResult struct {
+	Element *ui.Element
+	Retry   bool
+}
+
+// SystemMonitor stacks a live line chart per metric over one time axis, sampled by the caller.
+func SystemMonitor(c *ui.Context, times []time.Time, metrics []MonitorMetric, opts SystemMonitorOptions) SystemMonitorResult {
+	if opts.Height < 0 {
+		panic("mujica: SystemMonitor Height is negative")
+	}
+	for i, m := range metrics {
+		if m.Name == "" || len(m.Samples) != len(times) {
+			panic(fmt.Sprintf("mujica: SystemMonitor metric %d needs a Name and one sample per time", i))
+		}
+	}
+	h := opts.Height
+	if h == 0 {
+		h = 110
+	}
+	k := Tokens(c)
+	u := Density(c).Unit()
+	var r SystemMonitorResult
+	r.Element = ui.Column(c).Shrink(0).Gap(u * 3)
+	r.Element.Children(func() {
+		for _, m := range metrics {
+			ui.Column(c).Key(m.Name).Gap(u).Children(func() {
+				ui.Row(c).Gap(u * 2).AlignItems(ui.Center).Children(func() {
+					ui.Text(c, m.Name).FontWeight(600).Grow(1)
+					last := math.NaN()
+					if n := len(m.Samples); n > 0 {
+						last = m.Samples[n-1]
+					}
+					if !math.IsNaN(last) && opts.Status == DataReady {
+						ui.Text(c, fmt.Sprintf("%s %s", sandboxNum(last), m.Unit)).FontFeatures("tnum").
+							FontSize(FontSize(c, theme.CaptionSize+1)).TextColor(k.Text).Role(ui.RoleStatus)
+					}
+				})
+				unit := m.Unit
+				res := LineChart(c, []ChartSeries{{Name: m.Name, Values: m.Samples}}, LineChartOptions{
+					Frame: ChartFrame{Label: m.Name, Height: h, Status: opts.Status, Error: opts.Error},
+					Times: times, Format: func(v float64) string { return sandboxNum(v) + " " + unit },
+				})
+				r.Retry = r.Retry || res.Retried()
+			})
+		}
+	})
+	return r
+}
diff --git a/system_monitor_test.go b/system_monitor_test.go
new file mode 100644
index 0000000..cbc7edf
--- /dev/null
+++ b/system_monitor_test.go
@@ -0,0 +1,82 @@
+package mujica
+
+import (
+	"math"
+	"strings"
+	"testing"
+	"time"
+
+	"github.com/egoist/mygo/ui"
+)
+
+func monitorSample(n int) ([]time.Time, []MonitorMetric) {
+	t0 := time.Date(2026, 10, 5, 21, 0, 0, 0, time.UTC)
+	times := make([]time.Time, n)
+	cpu, mem := make([]float64, n), make([]float64, n)
+	for i := range n {
+		times[i] = t0.Add(time.Duration(i) * 5 * time.Second)
+		cpu[i] = 40 + 20*math.Sin(float64(i)/4)
+		mem[i] = 3.2 + float64(i)*0.02
+	}
+	return times, []MonitorMetric{{Name: "CPU", Unit: "%", Samples: cpu}, {Name: "Memory", Unit: "GB", Samples: mem}}
+}
+
+func TestSystemMonitorLiveAndKeyboard(t *testing.T) {
+	times, metrics := monitorSample(20)
+	tt := ui.NewTester(func(c *ui.Context) {
+		Use(c, Settings{})
+		SystemMonitor(c, times, metrics, SystemMonitorOptions{})
+	}, 600, 420)
+	if !tt.HasText("3.6 GB") || !tt.HasText("20.0 %") {
+		t.Fatalf("latest samples missing: %q", tt.Texts())
+	}
+	times, metrics = monitorSample(21)
+	tt.Frame()
+	if !tt.HasText("20.8 %") || tt.HasText("20.0 %") {
+		t.Fatalf("new sample: %q", tt.Texts())
+	}
+	tt.Key(0, ui.KeyTab) // the legend key
+	tt.Key(0, ui.KeyTab) // the plot
+	tt.Key(0, ui.KeyEnd)
+	found := false
+	for _, s := range tt.Texts() {
+		found = found || strings.Contains(s, "21:01:40")
+	}
+	if !found {
+		t.Fatalf("keyboard readout: %q", tt.Texts())
+	}
+}
+
+func TestSystemMonitorStatesAndRules(t *testing.T) {
+	times, metrics := monitorSample(5)
+	retries := 0
+	tt := ui.NewTester(func(c *ui.Context) {
+		Use(c, Settings{})
+		if SystemMonitor(c, times, metrics[:1], SystemMonitorOptions{Status: DataFailed, Error: "agent offline"}).Retry {
+			retries++
+		}
+	}, 600, 300)
+	if !tt.HasText("agent offline") {
+		t.Fatalf("error: %q", tt.Texts())
+	}
+	_ = tt.Click("Retry")
+	if retries != 1 {
+		t.Fatal("retry not reported")
+	}
+	defer func() {
+		if recover() == nil {
+			t.Fatal("mismatched samples did not panic")
+		}
+	}()
+	ui.NewTester(func(c *ui.Context) {
+		Use(c, Settings{})
+		SystemMonitor(c, times, []MonitorMetric{{Name: "x", Samples: []float64{1}}}, SystemMonitorOptions{})
+	}, 200, 200)
+}
+
+func TestSystemMonitorSnapshot(t *testing.T) {
+	times, metrics := monitorSample(40)
+	snapshot(t, "system_monitor", 560, 380, func(c *ui.Context) {
+		ui.Column(c).Padding(16).Children(func() { SystemMonitor(c, times, metrics, SystemMonitorOptions{}) })
+	})
+}
diff --git a/testdata/snapshots/darwin/system_monitor-dark.png b/testdata/snapshots/darwin/system_monitor-dark.png
new file mode 100644
index 0000000..8123bcf
Binary files /dev/null and b/testdata/snapshots/darwin/system_monitor-dark.png differ
diff --git a/testdata/snapshots/darwin/system_monitor-light.png b/testdata/snapshots/darwin/system_monitor-light.png
new file mode 100644
index 0000000..f8eabe1
Binary files /dev/null and b/testdata/snapshots/darwin/system_monitor-light.png differ