diff --git a/messages_devtools.go b/messages_devtools.go
index a1373e8..bd12df1 100644
--- a/messages_devtools.go
+++ b/messages_devtools.go
@@ -38,6 +38,11 @@ func init() {
 		"service_status.counts":        {"%d up · %d degraded · %d down", "%d 正常 · %d 降级 · %d 中断"},
 		"service_status.empty":         {"No services", "没有服务"},
 
+		"uptime_bar.ok":       {"Operational", "正常"},
+		"uptime_bar.degraded": {"Degraded", "降级"},
+		"uptime_bar.down":     {"Outage", "中断"},
+		"uptime_bar.nodata":   {"No data", "无数据"},
+
 		"alert_list.empty": {"No alerts", "没有告警"},
 	})
 }
diff --git a/testdata/snapshots/darwin/uptime_bar-dark.png b/testdata/snapshots/darwin/uptime_bar-dark.png
new file mode 100644
index 0000000..03b3e10
Binary files /dev/null and b/testdata/snapshots/darwin/uptime_bar-dark.png differ
diff --git a/testdata/snapshots/darwin/uptime_bar-light.png b/testdata/snapshots/darwin/uptime_bar-light.png
new file mode 100644
index 0000000..d01b930
Binary files /dev/null and b/testdata/snapshots/darwin/uptime_bar-light.png differ
diff --git a/uptime_bar.go b/uptime_bar.go
new file mode 100644
index 0000000..9c1fe37
--- /dev/null
+++ b/uptime_bar.go
@@ -0,0 +1,96 @@
+package mujica
+
+import (
+	"fmt"
+	"math"
+
+	"github.com/egoist/mygo/ui"
+
+	"mujicaui/internal"
+)
+
+// UptimeDay is one day's availability, 0 to 1; NaN means no data.
+type UptimeDay struct {
+	Date   Date
+	Uptime float64
+	// Note says what happened, as "12 min outage".
+	Note string
+}
+
+// UptimeBarOptions configure an UptimeBar; Frame.Height 0 means 36.
+type UptimeBarOptions struct {
+	Frame ChartFrame
+	// Degraded and Down are the uptime limits below which a day is marked; zero means 0.999 and 0.95.
+	Degraded, Down float64
+}
+
+// UptimeBar draws one bar per day by availability; hover or arrows read a day's detail.
+func UptimeBar(c *ui.Context, days []UptimeDay, opts UptimeBarOptions) ChartResult {
+	deg, down := opts.Degraded, opts.Down
+	if deg == 0 {
+		deg = 0.999
+	}
+	if down == 0 {
+		down = 0.95
+	}
+	if !(down < deg && deg <= 1 && down > 0) {
+		panic("mujica: UptimeBar needs 0 < Down < Degraded <= 1")
+	}
+	for i, d := range days {
+		if !math.IsNaN(d.Uptime) && (d.Uptime < 0 || d.Uptime > 1) {
+			panic(fmt.Sprintf("mujica: UptimeBar day %d uptime %v outside 0..1", i, d.Uptime))
+		}
+	}
+	if opts.Frame.Height == 0 {
+		opts.Frame.Height = 36
+	}
+	k := Tokens(c)
+	ch := newChart(c, opts.Frame)
+	n := len(days)
+	band := func(r ui.Rect) internal.Band { return internal.Band{N: n, R0: r.X, R1: r.X + r.W, Pad: 0.25} }
+	level := func(v float64) int { // 0 ok, 1 degraded, 2 down, 3 no data
+		switch {
+		case math.IsNaN(v):
+			return 3
+		case v < down:
+			return 2
+		case v < deg:
+			return 1
+		}
+		return 0
+	}
+	words := [...]string{msg(c, "uptime_bar.ok"), msg(c, "uptime_bar.degraded"), msg(c, "uptime_bar.down"), msg(c, "uptime_bar.nodata")}
+	res, _ := ch.build(chartSpec{
+		n: n,
+		draw: func(p *ui.Painter, r ui.Rect, active int) {
+			b := band(r)
+			for i, d := range days {
+				x, w := internal.Snap(p, b.Start(i)), max(b.Width(), 1)
+				lv := level(d.Uptime)
+				col := [...]ui.Color{k.Success, k.Warning, k.Danger, k.Border}[lv]
+				// Shorter bars mark bad days, so color is not the only cue.
+				h := r.H * [...]float32{1, 0.75, 0.5, 1}[lv]
+				p.Fill(ui.Rect{X: x, Y: r.Y + r.H - h, W: w, H: h}, col, 1)
+				if i == active {
+					p.Stroke(ui.Rect{X: x - 2, Y: r.Y - 2, W: w + 4, H: r.H + 4}, k.Focus, 2, 1.5)
+				}
+			}
+		},
+		pick: func(r ui.Rect, x, _ float32) int {
+			b := band(r)
+			return max(0, min(n-1, int((x-r.X)/b.Step())))
+		},
+		readout: func(i int) string {
+			d := days[i]
+			s := fmt.Sprintf("%s · %s", d.Date.String(), words[level(d.Uptime)])
+			if !math.IsNaN(d.Uptime) {
+				s += fmt.Sprintf(" · %.2f%%", d.Uptime*100)
+			}
+			if d.Note != "" {
+				s += " · " + d.Note
+			}
+			return s
+		},
+	})
+	return res
+}
diff --git a/uptime_bar_test.go b/uptime_bar_test.go
new file mode 100644
index 0000000..fdbff9f
--- /dev/null
+++ b/uptime_bar_test.go
@@ -0,0 +1,87 @@
+package mujica
+
+import (
+	"math"
+	"testing"
+
+	"github.com/egoist/mygo/ui"
+)
+
+func uptimeSample(n int) []UptimeDay {
+	days := make([]UptimeDay, n)
+	start := Date{Year: 2026, Month: 9, Day: 1}
+	for i := range days {
+		days[i] = UptimeDay{Date: start.AddDays(i), Uptime: 1}
+	}
+	days[3] = UptimeDay{Date: start.AddDays(3), Uptime: 0.9975, Note: "slow search"}
+	days[7] = UptimeDay{Date: start.AddDays(7), Uptime: 0.91, Note: "2 h outage"}
+	days[9].Uptime = math.NaN()
+	return days
+}
+
+func uptimeTester(days []UptimeDay, frame ChartFrame, points *[]int) *ui.Tester {
+	if frame.Label == "" {
+		frame.Label = "API uptime"
+	}
+	return ui.NewTester(func(c *ui.Context) {
+		Use(c, Settings{})
+		ui.Column(c).Padding(10).Children(func() {
+			r := UptimeBar(c, days, UptimeBarOptions{Frame: frame})
+			*points = append(*points, r.Point)
+		})
+	}, 520, 140)
+}
+
+func TestUptimeBarKeyboardReadout(t *testing.T) {
+	var pts []int
+	tt := uptimeTester(uptimeSample(30), ChartFrame{}, &pts)
+	tt.Key(0, ui.KeyTab)
+	tt.Key(0, ui.KeyRight)
+	for range 7 {
+		tt.Key(0, ui.KeyRight)
+	}
+	if !tt.HasText("2026-09-08 · Outage · 91.00% · 2 h outage") {
+		t.Fatalf("readout: %q", tt.Texts())
+	}
+	tt.Key(0, ui.KeyRight)
+	tt.Key(0, ui.KeyRight)
+	if !tt.HasText("2026-09-10 · No data") {
+		t.Fatalf("no data readout: %q", tt.Texts())
+	}
+}
+
+func TestUptimeBarHover(t *testing.T) {
+	var pts []int
+	tt := uptimeTester(uptimeSample(30), ChartFrame{}, &pts)
+	// The 4th of 30 bars across 500 DIPs starting at x = 10.
+	tt.Move(10+500*3.5/30, 30)
+	if pts[len(pts)-1] != 3 || !tt.HasText("2026-09-04 · Degraded · 99.75% · slow search") {
+		t.Fatalf("hover point %d: %q", pts[len(pts)-1], tt.Texts())
+	}
+}
+
+func TestUptimeBarStatesAndRules(t *testing.T) {
+	var pts []int
+	tt := uptimeTester(nil, ChartFrame{}, &pts)
+	if !tt.HasText("No data") {
+		t.Fatalf("empty: %q", tt.Texts())
+	}
+	tt = uptimeTester(uptimeSample(12), ChartFrame{Status: DataLoading}, &pts)
+	if !tt.HasText("Loading") {
+		t.Fatalf("loading: %q", tt.Texts())
+	}
+	defer func() {
+		if recover() == nil {
+			t.Fatal("uptime above 1 did not panic")
+		}
+	}()
+	uptimeTester([]UptimeDay{{Uptime: 1.2}}, ChartFrame{}, &pts)
+}
+
+func TestUptimeBarSnapshot(t *testing.T) {
+	snapshot(t, "uptime_bar", 520, 110, func(c *ui.Context) {
+		ui.Column(c).Padding(10).Children(func() {
+			UptimeBar(c, uptimeSample(45), UptimeBarOptions{Frame: ChartFrame{Label: "API uptime"}})
+		})
+	})
+}