diff --git a/src/app/features/scene/sceneButtons.css.ts b/src/app/features/scene/sceneButtons.css.ts
index 5c96e71b..9fca44f3 100644
--- a/src/app/features/scene/sceneButtons.css.ts
+++ b/src/app/features/scene/sceneButtons.css.ts
@@ -2,9 +2,14 @@ import { globalStyle } from '@vanilla-extract/css';
 
 // Meta, 2026-11-10: "buttons are big and ugly, too, they don't need chrome either". Over the scene a folds Button or
 // Chip is its label in the page's ink, with a faint wash on hover and focus. Menus and dialogs (#portalContainer) keep
-// folds' look. The selectors are folds' hashed recipe base classes (Button epr39zd, Chip _1bv8u1w6).
+// folds' look. The selectors are folds' hashed recipe base classes (Button, Chip; pinned below).
+// sceneButtons.test.ts resolves both from the installed folds and fails when a folds upgrade rehashes them.
+export const FOLDS_BUTTON_CLASS = 'epr39zd';
+export const FOLDS_CHIP_CLASS = '_1bv8u1w6';
 const scene = ':root[data-scene] #root';
-const controls = [`${scene} .epr39zd`, `${scene} ._1bv8u1w6`].join(', ');
+const btn = `${scene} .${FOLDS_BUTTON_CLASS}`;
+const chip = `${scene} .${FOLDS_CHIP_CLASS}`;
+const controls = [btn, chip].join(', ');
 globalStyle(controls, {
   backgroundColor: 'transparent',
   boxShadow: 'none',
@@ -12,20 +17,15 @@ globalStyle(controls, {
   color: 'inherit',
 });
 globalStyle(
-  [
-    `${scene} .epr39zd:hover`,
-    `${scene} .epr39zd:focus-visible`,
-    `${scene} ._1bv8u1w6:hover`,
-    `${scene} ._1bv8u1w6:focus-visible`,
-  ].join(', '),
+  [`${btn}:hover`, `${btn}:focus-visible`, `${chip}:hover`, `${chip}:focus-visible`].join(', '),
   { backgroundColor: 'color-mix(in srgb, currentColor 12%, transparent)' }
 );
 // A visible keyboard focus ring in the control's own ink, on top of the hover wash.
-globalStyle([`${scene} .epr39zd:focus-visible`, `${scene} ._1bv8u1w6:focus-visible`].join(', '), {
+globalStyle([`${btn}:focus-visible`, `${chip}:focus-visible`].join(', '), {
   outline: '2px solid currentColor',
   outlineOffset: '2px',
 });
-globalStyle(`${scene} .epr39zd`, {
+globalStyle(btn, {
   fontWeight: 700,
   textDecoration: 'underline',
   textUnderlineOffset: '0.25em',
diff --git a/src/app/features/scene/sceneButtons.test.ts b/src/app/features/scene/sceneButtons.test.ts
new file mode 100644
index 00000000..f3a2ff91
--- /dev/null
+++ b/src/app/features/scene/sceneButtons.test.ts
@@ -0,0 +1,30 @@
+import { readFileSync } from 'fs';
+import { createRequire } from 'module';
+import { dirname, join } from 'path';
+import { describe, expect, it } from 'vitest';
+
+// sceneButtons.css.ts restyles folds' Button and Chip by their hashed recipe base classes. A folds upgrade rehashes
+// them and the chromeless buttons would silently revert, so resolve the classes from the installed folds.
+const foldsDir = dirname(createRequire(import.meta.url).resolve('folds/package.json'));
+const dist = readFileSync(join(foldsDir, 'dist/index.js'), 'utf8');
+const css = readFileSync(join(foldsDir, 'dist/style.css'), 'utf8');
+const sceneButtons = readFileSync(
+  `${process.cwd()}/src/app/features/scene/sceneButtons.css.ts`,
+  'utf8'
+);
+
+const recipeBase = (name: string) =>
+  new RegExp(`\\b${name}\\$1 = createRuntimeFn\\(\\{ defaultClassName: "([^" ]+)`).exec(dist)?.[1];
+const pinned = (name: string) => new RegExp(`${name} = '([^']+)'`).exec(sceneButtons)?.[1];
+
+describe('sceneButtons pins folds recipe base classes', () => {
+  it.each([
+    ['Button', 'FOLDS_BUTTON_CLASS'],
+    ['Chip', 'FOLDS_CHIP_CLASS'],
+  ])('%s base class matches the installed folds', (recipe, constant) => {
+    const base = recipeBase(recipe);
+    expect(base, `folds no longer builds ${recipe} with createRuntimeFn`).toBeTruthy();
+    expect(pinned(constant)).toBe(base);
+    expect(css).toContain(`.${base} {`);
+  });
+});