Prove the array indexing the types only asserted

package.json

@@ -1,6 +1,6 @@
 {
   "name": "@isimplifyme/ui",
-  "version": "1.4.0",
+  "version": "1.4.1",
   "description": "React/Next.js UI library for iSimplifyMe properties \u2014 design system, article layouts, SEO helpers, bot middleware, and the iSM Concierge widget.",
   "homepage": "https://isimplifyme.com",
   "type": "module",

src/concierge.test.tsx

@@ -114,3 +114,40 @@ describe('with a leading node', () => {
     expect(slot.style.pointerEvents).toBe('none');
   });
 });
+
+describe('auto theme — the colour parsing these refactors touched', () => {
+  // parseRgba and luminance were rewritten to satisfy
+  // noUncheckedIndexedAccess (gridiron is the first consumer strict enough
+  // to typecheck this package's source). Neither is exported, so the honest
+  // test is the observable one: does auto-theme still TELL THE TWO APART?
+  function barBackgroundOn(bodyColor: string) {
+    // jsdom implements no hit-testing; the auto path samples whatever sits
+    // under the bar, which on a real page is the section behind it.
+    (document as unknown as { elementFromPoint: () => Element })
+      .elementFromPoint = () => document.body;
+    document.body.style.backgroundColor = bodyColor;
+    const { bar } = render({ theme: 'auto' });
+    return bar.style.background;
+  }
+
+  it('resolves a dark page differently from a light one', () => {
+    const onDark = barBackgroundOn('rgb(14, 15, 19)');
+    act(() => root.unmount());
+    container.remove();
+    container = document.createElement('div');
+    document.body.appendChild(container);
+    root = createRoot(container);
+    const onLight = barBackgroundOn('rgb(247, 247, 245)');
+
+    expect(onDark).not.toBe('');
+    expect(onLight).not.toBe('');
+    // If parseRgba returned null for either, both would land on the same
+    // fallback and this would pass vacuously — so assert they DIFFER.
+    expect(onDark).not.toBe(onLight);
+  });
+
+  it('survives a background colour it cannot parse', () => {
+    const bg = barBackgroundOn('color(display-p3 0.1 0.1 0.1)');
+    expect(bg).not.toBe('');
+  });
+});

src/concierge.tsx

@@ -168,11 +168,13 @@ function readCookie(name: string): string {
   const match = document.cookie.match(
     new RegExp(`(?:^|;\\s*)${name}=([^;]*)`)
   );
-  if (!match) return '';
+  const value = match?.[1];
+  if (value === undefined) return '';
   try {
-    return decodeURIComponent(match[1]);
+    return decodeURIComponent(value);
   } catch {
-    return match[1];
+    // Malformed percent-encoding — hand back the raw value rather than ''.
+    return value;
   }
 }
 
@@ -278,16 +280,20 @@ export default function ConciergeWidget({
 
     function parseRgba(color: string): [number, number, number, number] | null {
       const m = color.match(/rgba?\((\d+),\s*(\d+),\s*(\d+)(?:,\s*([\d.]+))?\)/);
-      if (!m) return null;
-      return [+m[1], +m[2], +m[3], m[4] !== undefined ? +m[4] : 1];
+      const [, r, g, b, a] = m ?? [];
+      if (r === undefined || g === undefined || b === undefined) return null;
+      return [+r, +g, +b, a !== undefined ? +a : 1];
     }
 
     function luminance(r: number, g: number, b: number): number {
-      const [rs, gs, bs] = [r, g, b].map((c) => {
+      // A mapped array is `number[]`, not a 3-tuple, so destructuring it
+      // yields `number | undefined` under noUncheckedIndexedAccess. Mapping
+      // each channel keeps the arity in the types.
+      const srgb = (c: number) => {
         const s = c / 255;
         return s <= 0.03928 ? s / 12.92 : Math.pow((s + 0.055) / 1.055, 2.4);
-      });
-      return 0.2126 * rs + 0.7152 * gs + 0.0722 * bs;
+      };
+      return 0.2126 * srgb(r) + 0.7152 * srgb(g) + 0.0722 * srgb(b);
     }
 
     function sampleBackground(el: Element): 'dark' | 'light' {