diff --git a/src/design-system/composites/ThemedChart/ChartTooltip.module.css b/src/design-system/composites/ThemedChart/ChartTooltip.module.css
new file mode 100644
index 0000000..5b6006c
--- /dev/null
+++ b/src/design-system/composites/ThemedChart/ChartTooltip.module.css
@@ -0,0 +1,47 @@
+.tooltip {
+  background: var(--bg-surface);
+  border: 1px solid var(--border);
+  border-radius: var(--radius-sm);
+  box-shadow: var(--shadow-md);
+  padding: 6px 10px;
+  font-size: 12px;
+}
+
+.time {
+  font-family: var(--font-mono);
+  font-size: 10px;
+  color: var(--text-muted);
+  margin-bottom: 4px;
+  padding-bottom: 3px;
+  border-bottom: 1px solid var(--border-subtle);
+}
+
+.row {
+  display: flex;
+  align-items: center;
+  gap: 5px;
+  margin-bottom: 2px;
+}
+
+.row:last-child {
+  margin-bottom: 0;
+}
+
+.dot {
+  width: 6px;
+  height: 6px;
+  border-radius: 50%;
+  flex-shrink: 0;
+}
+
+.label {
+  color: var(--text-muted);
+  font-size: 11px;
+}
+
+.value {
+  font-family: var(--font-mono);
+  font-weight: 600;
+  font-size: 11px;
+  color: var(--text-primary);
+}
diff --git a/src/design-system/composites/ThemedChart/ChartTooltip.tsx b/src/design-system/composites/ThemedChart/ChartTooltip.tsx
new file mode 100644
index 0000000..56b9abc
--- /dev/null
+++ b/src/design-system/composites/ThemedChart/ChartTooltip.tsx
@@ -0,0 +1,41 @@
+import type { TooltipProps } from 'recharts'
+import styles from './ChartTooltip.module.css'
+
+function formatValue(val: number): string {
+  if (val >= 1_000_000) return `${(val / 1_000_000).toFixed(1)}M`
+  if (val >= 1000) return `${(val / 1000).toFixed(1)}k`
+  if (Number.isInteger(val)) return String(val)
+  return val.toFixed(1)
+}
+
+function formatTimestamp(val: unknown): string | null {
+  if (val == null) return null
+  const str = String(val)
+  const ms = typeof val === 'number' && val > 1e12 ? val
+    : typeof val === 'number' && val > 1e9 ? val * 1000
+    : Date.parse(str)
+  if (isNaN(ms)) return str
+  return new Date(ms).toLocaleString([], {
+    month: 'short', day: 'numeric',
+    hour: '2-digit', minute: '2-digit', second: '2-digit',
+  })
+}
+
+export function ChartTooltip({ active, payload, label }: TooltipProps<number, string>) {
+  if (!active || !payload?.length) return null
+
+  const timeLabel = formatTimestamp(label)
+
+  return (
+    <div className={styles.tooltip}>
+      {timeLabel && <div className={styles.time}>{timeLabel}</div>}
+      {payload.map((entry) => (
+        <div key={entry.dataKey as string} className={styles.row}>
+          <span className={styles.dot} style={{ background: entry.color }} />
+          <span className={styles.label}>{entry.name}:</span>
+          <span className={styles.value}>{formatValue(entry.value as number)}</span>
+        </div>
+      ))}
+    </div>
+  )
+}