diff --git a/internal/animate/ease.go b/internal/animate/ease.go
index b558773..6c28b93 100644
--- a/internal/animate/ease.go
+++ b/internal/animate/ease.go
@@ -30,11 +30,30 @@ func Clamp01(t float64) float64 {
 }
 
 func Spring(current, target float64, velocity *float64, dt float64) float64 {
+	if math.IsNaN(target) || math.IsInf(target, 0) {
+		target = 0
+	}
+	if math.IsNaN(current) || math.IsInf(current, 0) {
+		current = target
+	}
+	if velocity == nil {
+		return target
+	}
+	if math.IsNaN(*velocity) || math.IsInf(*velocity, 0) {
+		*velocity = 0
+	}
+	if dt <= 0 || math.IsNaN(dt) || math.IsInf(dt, 0) {
+		return current
+	}
 	force := stiffness * (target - current)
 	*velocity += force * dt
 	*velocity *= math.Exp(-damping * dt)
 	if *velocity < 0.0001 && *velocity > -0.0001 {
 		*velocity = 0
 	}
-	return current + *velocity*dt
+	res := current + *velocity*dt
+	if math.IsNaN(res) || math.IsInf(res, 0) {
+		return target
+	}
+	return res
 }
diff --git a/internal/animate/ease_test.go b/internal/animate/ease_test.go
index 6cd77df..5e05baf 100644
--- a/internal/animate/ease_test.go
+++ b/internal/animate/ease_test.go
@@ -67,3 +67,31 @@ func TestSpringStableAtUITickInterval(t *testing.T) {
 		t.Errorf("Spring oscillated negative at dt=0.13 (min %f) — value would render as 0 B/s", minVal)
 	}
 }
+
+func TestSpringNaNAndInfGuards(t *testing.T) {
+	var vel float64
+	// Target is NaN
+	val := Spring(100, math.NaN(), &vel, 0.13)
+	if math.IsNaN(val) || math.IsInf(val, 0) {
+		t.Errorf("Spring with NaN target returned %f", val)
+	}
+
+	// Current is NaN
+	val = Spring(math.NaN(), 100, &vel, 0.13)
+	if math.IsNaN(val) || math.IsInf(val, 0) {
+		t.Errorf("Spring with NaN current returned %f", val)
+	}
+
+	// Velocity is NaN
+	vel = math.NaN()
+	val = Spring(100, 100, &vel, 0.13)
+	if math.IsNaN(val) || math.IsInf(val, 0) || math.IsNaN(vel) {
+		t.Errorf("Spring with NaN velocity returned val=%f, vel=%f", val, vel)
+	}
+
+	// dt is NaN
+	val = Spring(100, 100, &vel, math.NaN())
+	if math.IsNaN(val) || math.IsInf(val, 0) {
+		t.Errorf("Spring with NaN dt returned %f", val)
+	}
+}
diff --git a/internal/history/persist_test.go b/internal/history/persist_test.go
index da4f07f..bb4a08b 100644
--- a/internal/history/persist_test.go
+++ b/internal/history/persist_test.go
@@ -35,6 +35,13 @@ func TestSaveLoad(t *testing.T) {
 }
 
 func TestLoadMissing(t *testing.T) {
+	dir := t.TempDir()
+	orig := statsPath
+	statsPath = func() (string, error) {
+		return filepath.Join(dir, "nonexistent_stats.json"), nil
+	}
+	defer func() { statsPath = orig }()
+
 	tracker := NewTracker()
 	err := tracker.Load()
 	if err == nil {
diff --git a/internal/ui/model.go b/internal/ui/model.go
index 608470a..1d46440 100644
--- a/internal/ui/model.go
+++ b/internal/ui/model.go
@@ -212,7 +212,7 @@ func (m Model) Update(msg tea.Msg) (tea.Model, tea.Cmd) {
 
 	case pingMsg:
 		m.pingLatency = time.Duration(msg)
-		return m, nil
+		return m, m.pingTick()
 
 	case sampleMsg:
 		if msg.Err != nil {
@@ -502,7 +502,7 @@ func FormatBps(bps float64, unit UnitMode) string {
 }
 
 func FormatBpsExt(bps float64, unit UnitMode, bits bool) string {
-	if bps < 0 {
+	if bps < 0 || math.IsNaN(bps) || math.IsInf(bps, 0) {
 		bps = 0
 	}
 	if bits {
diff --git a/internal/ui/model_test.go b/internal/ui/model_test.go
index 12b7d8a..256b23d 100644
--- a/internal/ui/model_test.go
+++ b/internal/ui/model_test.go
@@ -42,10 +42,15 @@ func TestFormatBpsExt(t *testing.T) {
 }
 
 func TestFormatBpsExt_EdgeCases(t *testing.T) {
-	// Test NaN and Inf - should not crash
-	_ = FormatBpsExt(math.NaN(), UnitAuto, false)
-	_ = FormatBpsExt(math.Inf(1), UnitAuto, false)
-	_ = FormatBpsExt(math.Inf(-1), UnitAuto, false)
+	if got := FormatBpsExt(math.NaN(), UnitAuto, false); got != "0 B/s" {
+		t.Errorf("FormatBpsExt(NaN) = %q; want '0 B/s'", got)
+	}
+	if got := FormatBpsExt(math.Inf(1), UnitAuto, false); got != "0 B/s" {
+		t.Errorf("FormatBpsExt(+Inf) = %q; want '0 B/s'", got)
+	}
+	if got := FormatBpsExt(math.Inf(-1), UnitAuto, false); got != "0 B/s" {
+		t.Errorf("FormatBpsExt(-Inf) = %q; want '0 B/s'", got)
+	}
 }
 
 func TestFormatBpsFixedWidth(t *testing.T) {
diff --git a/internal/ui/views.go b/internal/ui/views.go
index f113ebd..08d851d 100644
--- a/internal/ui/views.go
+++ b/internal/ui/views.go
@@ -30,6 +30,15 @@ func max(a, b int) int {
 }
 
 func maxf(a, b float64) float64 {
+	if math.IsNaN(a) {
+		if math.IsNaN(b) {
+			return 0
+		}
+		return b
+	}
+	if math.IsNaN(b) {
+		return a
+	}
 	if a > b {
 		return a
 	}
@@ -96,6 +105,9 @@ func formatInterval(d time.Duration) string {
 }
 
 func formatBytes(b float64) string {
+	if b < 0 || math.IsNaN(b) || math.IsInf(b, 0) {
+		b = 0
+	}
 	const (
 		KB = 1024.0
 		MB = 1024 * KB