diff --git a/lib/svg/generatorConstants.massive-scaling.test.ts b/lib/svg/generatorConstants.massive-scaling.test.ts
new file mode 100644
index 000000000..010fba484
--- /dev/null
+++ b/lib/svg/generatorConstants.massive-scaling.test.ts
@@ -0,0 +1,85 @@
+import { describe, expect, it } from 'vitest';
+import { SVG_WIDTH, SVG_HEIGHT, isFontKey } from './generatorConstants';
+import { FONT_MAP } from './fonts';
+
+describe('generatorConstants Massive Scaling', () => {
+  it('isFontKey returns true for all known keys across 10,000 lookups', () => {
+    const keys = Object.keys(FONT_MAP);
+    expect(keys.length).toBeGreaterThan(0);
+
+    let allValid = true;
+    const start = performance.now();
+    for (let i = 0; i < 10_000; i++) {
+      const key = keys[i % keys.length];
+      if (!isFontKey(key)) {
+        allValid = false;
+        break;
+      }
+    }
+    const duration = performance.now() - start;
+
+    expect(allValid).toBe(true);
+    // Generous performance margin to prevent CI flakiness
+    expect(duration).toBeLessThan(5000);
+  });
+
+  it('isFontKey returns false for 5,000 synthetic unknown font names', () => {
+    const knownKeys = new Set(Object.keys(FONT_MAP));
+    for (let i = 0; i < 5_000; i++) {
+      const candidate = `nonexistent_font_sentinel_${i}`;
+      if (!knownKeys.has(candidate)) {
+        expect(isFontKey(candidate)).toBe(false);
+      }
+    }
+  });
+
+  it('SVG_WIDTH and SVG_HEIGHT do not drift under 10,000 repeated reads', () => {
+    let widthSum = 0;
+    let heightSum = 0;
+    for (let i = 0; i < 10_000; i++) {
+      widthSum += SVG_WIDTH;
+      heightSum += SVG_HEIGHT;
+    }
+    expect(widthSum).toBe(600 * 10_000);
+    expect(heightSum).toBe(420 * 10_000);
+  });
+
+  it('SVG_WIDTH and SVG_HEIGHT yield valid coordinate bounds for 10,000 simulated contributor positions', () => {
+    let allValid = true;
+    for (let i = 0; i < 10_000; i++) {
+      const x = i % SVG_WIDTH;
+      const y = Math.floor(i / SVG_WIDTH) % SVG_HEIGHT;
+      if (
+        x < 0 ||
+        x >= SVG_WIDTH ||
+        y < 0 ||
+        y >= SVG_HEIGHT ||
+        !Number.isFinite(x) ||
+        !Number.isFinite(y)
+      ) {
+        allValid = false;
+        break;
+      }
+    }
+    expect(allValid).toBe(true);
+  });
+
+  it('isFontKey handles extreme string lengths without timing out', () => {
+    const knownKeys = new Set(Object.keys(FONT_MAP));
+    const extremeInputs = [
+      '',
+      'a',
+      'x'.repeat(100),
+      'x'.repeat(10_000),
+      'x'.repeat(100_000),
+    ].filter((s) => !knownKeys.has(s));
+
+    const start = performance.now();
+    extremeInputs.forEach((s) => {
+      expect(isFontKey(s)).toBe(false);
+    });
+    const duration = performance.now() - start;
+    // Generous performance margin to prevent CI flakiness
+    expect(duration).toBeLessThan(5000);
+  });
+});