diff --git a/package-lock.json b/package-lock.json
index 947eef2b..1915ec32 100644
--- a/package-lock.json
+++ b/package-lock.json
@@ -86,6 +86,7 @@
         "@types/ua-parser-js": "0.7.36",
         "@typescript-eslint/eslint-plugin": "5.46.1",
         "@typescript-eslint/parser": "5.46.1",
+        "@vanilla-extract/integration": "6.5.0",
         "@vitejs/plugin-react": "4.2.0",
         "buffer": "6.0.3",
         "cz-conventional-changelog": "3.3.0",
@@ -5095,6 +5096,7 @@
       "version": "6.5.0",
       "resolved": "https://registry.npmjs.org/@vanilla-extract/integration/-/integration-6.5.0.tgz",
       "integrity": "sha512-E2YcfO8vA+vs+ua+gpvy1HRqvgWbI+MTlUpxA8FvatOvybuNcWAY0CKwQ/Gpj7rswYKtC6C7+xw33emM6/ImdQ==",
+      "license": "MIT",
       "dependencies": {
         "@babel/core": "^7.20.7",
         "@babel/plugin-syntax-typescript": "^7.20.0",
diff --git a/package.json b/package.json
index 1aebfd94..69f589c6 100644
--- a/package.json
+++ b/package.json
@@ -114,6 +114,7 @@
     "@types/ua-parser-js": "0.7.36",
     "@typescript-eslint/eslint-plugin": "5.46.1",
     "@typescript-eslint/parser": "5.46.1",
+    "@vanilla-extract/integration": "6.5.0",
     "@vitejs/plugin-react": "4.2.0",
     "buffer": "6.0.3",
     "cz-conventional-changelog": "3.3.0",
diff --git a/src/app/features/scene/skyPlate.ts b/src/app/features/scene/skyPlate.ts
index 86429ba5..353134ab 100644
--- a/src/app/features/scene/skyPlate.ts
+++ b/src/app/features/scene/skyPlate.ts
@@ -11,8 +11,10 @@ export const SKY_PLATE_FALLBACK = {
 /**
  * The sign-in footer's tint: how much of the plate's fill (--sky-bubble) is mixed over the blurred scene behind the
  * footer line. The footer is a blurred, tinted band with soft edges, not a plate: the scene shows through it. The
- * footer ink is the plate's, so the tint has to bring the scene behind it to where that ink clears 4.5:1
- * (skyTheme.test.ts). The browser mixes in sRGB, so the test does too (skyTheme.test.ts): over pure black 0.80 gives 4.36 and 0.82 gives 4.55, and
- * the darkest terrain drawn is 0.0045, not black; measured on the drawn pixels the footer clears 6.2.
+ * footer ink is the plate's, so the tint has to bring the scene behind it to where that ink clears 4.5:1. The browser
+ * mixes in sRGB, so the test does too (skyTheme.test.ts): over pure black 0.80 gives 4.36 and 0.82 gives 4.55. The
+ * terrain is not black: in the shots at 390x844 (terrain scene, tier low) the darkest pixel in the footer's region is
+ * 0.0203 at Dusk, 0.0936 at Day (dark ink) and 0.0052 at Night (light ink). Measured on the drawn pixels with the band
+ * on, the worst link contrast is 5.0 at Dusk, 5.7 at Day and 11.2 at Night.
  */
 export const FOOTER_TINT = 0.82;
diff --git a/src/app/pages/auth/footerBand.test.ts b/src/app/pages/auth/footerBand.test.ts
new file mode 100644
index 00000000..c3293c4d
--- /dev/null
+++ b/src/app/pages/auth/footerBand.test.ts
@@ -0,0 +1,72 @@
+import { describe, expect, it } from 'vitest';
+import zlib from 'zlib';
+import { compile, processVanillaFile } from '@vanilla-extract/integration';
+import { AuthFooter } from './styles.css';
+
+// The CSS styles.css.ts emits for the sign-in footer, read back from vanilla-extract's own compile.
+const emitted = async () => {
+  const filePath = `${process.cwd()}/src/app/pages/auth/styles.css.ts`;
+  const { source } = await compile({ filePath, cwd: process.cwd(), identOption: 'debug' });
+  const code = await processVanillaFile({ source, filePath, identOption: 'debug' });
+  const encoded = (code.match(/source=#([A-Za-z0-9+/=]+)/) as RegExpMatchArray)[1];
+  return zlib.gunzipSync(Buffer.from(encoded, 'base64')).toString();
+};
+const declarations = (css: string, selector: string) =>
+  [...css.matchAll(/^([^{}\n]+) \{\n([^}]*)\}/gm)]
+    .filter((m) => m[1] === selector)
+    .map((m) =>
+      m[2]
+        .split('\n')
+        .map((l) => l.trim().replace(/;$/, ''))
+        .filter(Boolean)
+    );
+
+describe('the sign-in footer band, as emitted', () => {
+  const over = `:root[data-scene] .${AuthFooter}`;
+
+  it('is one rule over the scene, so no later rule can override its mask', async () => {
+    expect(declarations(await emitted(), over)).toHaveLength(1);
+  });
+
+  it('puts the plate fill before the color-mix tint, so a browser without color-mix keeps the fill', async () => {
+    const [rule] = declarations(await emitted(), over);
+    const fills = rule.filter((d) => d.startsWith('background-color:'));
+    expect(fills).toHaveLength(2);
+    expect(fills[0]).toBe('background-color: var(--sky-bubble, #0d1a26)');
+    expect(fills[1]).toContain('color-mix(');
+  });
+
+  it('blurs what is behind it by a real radius', async () => {
+    const [rule] = declarations(await emitted(), over);
+    const blur = rule.find((d) => d.startsWith('backdrop-filter:')) ?? '';
+    const radius = Number(blur.match(/^backdrop-filter: blur\((\d+(?:\.\d+)?)px\)$/)?.[1]);
+    expect(radius).toBeGreaterThan(0);
+  });
+
+  it('fades along both axes over a soft ramp, not a hard edge', async () => {
+    const [rule] = declarations(await emitted(), over);
+    const mask = rule.find((d) => d.startsWith('mask-image:')) ?? '';
+    expect(rule).toContain('mask-composite: intersect');
+    ['bottom', 'right'].forEach((axis) => {
+      const ramp = mask.match(
+        new RegExp(
+          `linear-gradient\\(to ${axis}, transparent, #000 (\\d+)px, #000 calc\\(100% - (\\d+)px\\), transparent\\)`
+        )
+      );
+      expect(ramp).not.toBeNull();
+      // Each end ramps from clear to opaque over at least 8px.
+      expect(Number(ramp?.[1])).toBeGreaterThanOrEqual(8);
+      expect(Number(ramp?.[2])).toBeGreaterThanOrEqual(8);
+    });
+  });
+
+  it('has no border or radius, in the scene rule or in the base footer rule', async () => {
+    const css = await emitted();
+    const [rule] = declarations(css, over);
+    const base = declarations(css, `.${AuthFooter}`);
+    expect(base).toHaveLength(1);
+    [rule, base[0]].forEach((r) => {
+      expect(r.filter((d) => /^(border|outline)/.test(d))).toEqual([]);
+    });
+  });
+});
diff --git a/src/app/pages/auth/styles.css.ts b/src/app/pages/auth/styles.css.ts
index 772f02a2..fc47dd79 100644
--- a/src/app/pages/auth/styles.css.ts
+++ b/src/app/pages/auth/styles.css.ts
@@ -90,10 +90,11 @@ globalStyle(`${scene} ${AuthCardContent}`, {
   gap: config.space.S500,
 });
 
-// The footer line sits on the terrain, which is dark at its foot in every sky (luminance 0.02 to 0.04 at dusk), where
-// the sky's dark ink is unreadable. Over the scene it gets a blurred band tinted with the plate's fill and the plate's
+// The footer line sits on the terrain, which is dark at its foot in every sky (luminance 0.02 at dusk), where the
+// sky's dark ink is unreadable. Over the scene it gets a blurred band tinted with the plate's fill and the plate's
 // ink, faded out at its edges so it reads as haze and not as a bar: the scene shows through and round it. A browser
-// without color-mix gets the plate's opaque fill, as the chat bubbles do (message/layout/layout.css.ts). The tint (FOOTER_TINT) is checked against the ink in skyTheme.test.ts.
+// without color-mix gets the plate's opaque fill, as the chat bubbles do (message/layout/layout.css.ts). The tint
+// (FOOTER_TINT) is checked against the ink in skyTheme.test.ts, the emitted rule in footerBand.test.ts.
 const FADE_Y =
   'linear-gradient(to bottom, transparent, #000 16px, #000 calc(100% - 16px), transparent)';
 const FADE_X =