diff --git a/packages/server/app/components/TimeSeriesChart.tsx b/packages/server/app/components/TimeSeriesChart.tsx
index bc2e2b9d..5b016480 100644
--- a/packages/server/app/components/TimeSeriesChart.tsx
+++ b/packages/server/app/components/TimeSeriesChart.tsx
@@ -162,7 +162,7 @@ export default function TimeSeriesChart({
                 <YAxis
                     yAxisId="bounceRate"
                     dataKey="bounceRate"
-                    domain={[0, 120]}
+                    domain={[0, 100]}
                     hide={true}
                 />
 
diff --git a/packages/server/app/components/__tests__/TimeSeriesChart.test.tsx b/packages/server/app/components/__tests__/TimeSeriesChart.test.tsx
new file mode 100644
index 00000000..d6d153b0
--- /dev/null
+++ b/packages/server/app/components/__tests__/TimeSeriesChart.test.tsx
@@ -0,0 +1,59 @@
+// @vitest-environment jsdom
+import { render, screen, cleanup } from "@testing-library/react";
+import { afterEach, describe, expect, test, vi } from "vitest";
+import "vitest-dom/extend-expect";
+
+import TimeSeriesChart from "../TimeSeriesChart";
+
+vi.mock("recharts", () => ({
+    ResponsiveContainer: ({ children }: { children: React.ReactNode }) => (
+        <div>{children}</div>
+    ),
+    ComposedChart: ({ children }: { children: React.ReactNode }) => (
+        <div>{children}</div>
+    ),
+    CartesianGrid: () => null,
+    XAxis: () => null,
+    YAxis: ({
+        yAxisId,
+        domain,
+    }: {
+        yAxisId: string;
+        domain: [number, number];
+    }) => (
+        <div
+            data-testid={`y-axis-${yAxisId}`}
+            data-domain={JSON.stringify(domain)}
+        />
+    ),
+    Tooltip: () => null,
+    Area: () => null,
+    Line: () => null,
+}));
+
+describe("TimeSeriesChart", () => {
+    afterEach(() => {
+        cleanup();
+    });
+
+    test("scales bounce rate against a fixed 0–100% domain", () => {
+        render(
+            <TimeSeriesChart
+                intervalType="DAY"
+                data={[
+                    {
+                        date: "2025-01-01T00:00:00.000Z",
+                        views: 100,
+                        visitors: 75,
+                        bounceRate: 46,
+                    },
+                ]}
+            />,
+        );
+
+        expect(screen.getByTestId("y-axis-bounceRate")).toHaveAttribute(
+            "data-domain",
+            "[0,100]",
+        );
+    });
+});