diff --git a/docs/process/CONTINUE-audit-queue.md b/docs/process/CONTINUE-audit-queue.md
index acdf03c5e..a936bc0e0 100644
--- a/docs/process/CONTINUE-audit-queue.md
+++ b/docs/process/CONTINUE-audit-queue.md
@@ -253,8 +253,19 @@ por los dos caminos.
    `…Required…` CON el guard S-34 actualizado en el mismo commit, los 2
    `as never` de `compile.ts` retirados (vestigio pre-`DepSink`), y
    `_resetCompileCache` resultó YA borrado — fuera de la cola ·
-   `E2` (`globalThis.matchMedia` crudo en eidos) · `E3` (catch mudo en
-   `#renderSchemeCss`).
+   ~~`E2`~~ · ~~`E3`~~ **EJECUTADOS 2026-08-13** — E2: el mode-source de sistema
+   consulta `dom.getWindow().matchMedia` y se suscribe por `dom.listen`
+   (ventana CORRECTA en iframe/popup; fallback crudo sin dom); descartado el
+   tracker en adom por la regla de ≥2 consumidores (los 6 boots reales de web/
+   pasan todos su `modeSource` — el camino de sistema tiene hoy CERO
+   consumidores vivos). E3: `#lastSchemeCss` — un re-derive que falla conserva
+   el ultimo bloque bueno y avisa por `#uix?.logger` en vez de DESVESTIR la
+   pagina (`apply()` leia '' como «sin esquema» y borraba el `<style>`);
+   `applyColorScheme` sigue lanzando eager en la cara del llamador. Hallazgo
+   del rojo: el validador de config es FAIL-CLOSED y rechaza escalas rotas en
+   la puerta — la inyeccion del test va sobre `buildScheme` mismo, passthrough
+   real hasta que el flag lo revienta. Ambos tests vistos morder el codigo
+   viejo via stash.
 5. **§3.6 blocks** — `A-47` (anillo de foco 1,43:1 sobre panel sólido) ·
    `A-69` (`duration` de count-up no significa segundos).
 6. **§3.3 eje B** — 4 continuos sin throttle (gradient-builder, color-picker
diff --git a/src/uix/eidos/active-eidos.svelte.ts b/src/uix/eidos/active-eidos.svelte.ts
index acf94f2f5..8a5e661cf 100644
--- a/src/uix/eidos/active-eidos.svelte.ts
+++ b/src/uix/eidos/active-eidos.svelte.ts
@@ -1075,20 +1075,40 @@ export class ActiveEidos {
 		}
 	}
 
+	/** Last successfully rendered scheme block — the E3 keep on a failed re-derive. */
+	#lastSchemeCss = '';
+
 	#renderSchemeCss(): string {
-		if (!this.#schemeSpec) return '';
+		if (!this.#schemeSpec) {
+			this.#lastSchemeCss = '';
+			return '';
+		}
 		let result: BuildSchemeResult;
 		try {
 			result = this.#buildSchemeResult();
-		} catch {
-			return '';
+		} catch (error) {
+			// A re-derive that fails (a mode / theme change whose donor scales
+			// the seed cannot build against) must not STRIP the page of the
+			// block that was already good: `apply()` reads '' as "no scheme"
+			// and deletes the <style>. Keep the last good CSS and say why — a
+			// bad path does not un-invent in silence (E3, the S-09 doctrine).
+			// `applyColorScheme` itself still throws at the caller: it builds
+			// eagerly before `apply()` ever runs.
+			this.#uix?.logger.warn(
+				'eidos.scheme',
+				'color-scheme re-derive failed; keeping the previous block',
+				{ context: { error } }
+			);
+			return this.#lastSchemeCss;
 		}
 		const selector = this.#schemeSpec.options.selector ?? DEFAULT_SCHEME_SELECTOR;
 		// Dual stack per opaque step: hex fallback + oklch() wide-gamut override.
 		const body = schemeDeclarations(result)
 			.map((line) => `\t${line}`)
 			.join('\n');
-		return body ? `${selector} {\n${body}\n}` : '';
+		const css = body ? `${selector} {\n${body}\n}` : '';
+		this.#lastSchemeCss = css;
+		return css;
 	}
 
 	#renderTypeScaleCss(): string {
@@ -1305,7 +1325,9 @@ function resolvePreferences(options: ActiveEidosOptions): ActiveEidosPreferenceS
 		theme: options.theme,
 		modeSource:
 			options.modeSource ??
-			(options.mode ? createStaticValueSource(options.mode) : createSystemColorSchemeSource()),
+			(options.mode
+				? createStaticValueSource(options.mode)
+				: createSystemColorSchemeSource(options.dom ?? options.uix?.dom)),
 		densitySource:
 			options.densitySource ?? createStaticValueSource(options.density ?? DEFAULT_DENSITY),
 		scalingSource:
@@ -1345,14 +1367,20 @@ function createStaticValueSource<T>(value: T): ActiveEidosValueSource<T> {
 }
 
 function createSystemColorSchemeSource(
+	dom?: ActiveDom,
 	fallback: ThemeEffective = DEFAULT_MODE
 ): ActiveEidosValueSource<ThemeEffective> {
-	const media = getColorSchemeMedia();
+	const media = getColorSchemeMedia(dom);
 	return {
 		get: () => (media ? (media.matches ? 'dark' : 'light') : fallback),
 		onChange(handler) {
 			if (!media) return () => {};
 			const listener = () => handler(media.matches ? 'dark' : 'light');
+			// Managed subscription through the injected dom — the house rule
+			// (window/document listeners go through ActiveDom), and the same
+			// lifecycle every other eidos listener already has (E2).
+			if (dom) return dom.listen(media, 'change', listener);
+			// Domless boot (bare CSS serialization / SSR): raw fallback.
 			if (typeof media.addEventListener === 'function') {
 				media.addEventListener('change', listener);
 				return () => media.removeEventListener('change', listener);
@@ -1363,7 +1391,15 @@ function createSystemColorSchemeSource(
 	};
 }
 
-function getColorSchemeMedia(): MediaQueryList | undefined {
+function getColorSchemeMedia(dom?: ActiveDom): MediaQueryList | undefined {
+	if (dom) {
+		// The dom's window, not the global one — an eidos booted for an
+		// iframe / popup must watch ITS window's color scheme (E2).
+		const win = dom.getWindow();
+		return typeof win.matchMedia === 'function'
+			? win.matchMedia('(prefers-color-scheme: dark)')
+			: undefined;
+	}
 	if (typeof globalThis.matchMedia !== 'function') return undefined;
 	return globalThis.matchMedia('(prefers-color-scheme: dark)');
 }
diff --git a/src/uix/eidos/active-eidos.test.ts b/src/uix/eidos/active-eidos.test.ts
index ede059c34..311ab3635 100644
--- a/src/uix/eidos/active-eidos.test.ts
+++ b/src/uix/eidos/active-eidos.test.ts
@@ -1,5 +1,19 @@
 // @vitest-environment jsdom
-import { describe, expect, it } from 'vitest';
+import { describe, expect, it, vi } from 'vitest';
+
+// E3 failure injection — `buildScheme` is passthrough-real until a test flips
+// the flag, then it throws exactly where a bad donor-scale re-derive would.
+const schemeBuildFailure = vi.hoisted(() => ({ fail: false }));
+vi.mock('./lib/build-scheme', async (importOriginal) => {
+	const real = await importOriginal<typeof import('./lib/build-scheme')>();
+	return {
+		...real,
+		buildScheme: (...args: Parameters<typeof real.buildScheme>) => {
+			if (schemeBuildFailure.fail) throw new Error('donor scales exploded');
+			return real.buildScheme(...args);
+		}
+	};
+});
 import { createActiveDom } from '$adom';
 import { ActiveUixDomDisabledError } from '$active-uix/errors';
 import type { Density } from '$libs/density';
@@ -529,3 +543,85 @@ describe('ActiveEidos forced-colors (a11y)', () => {
 		expect(css).toContain(':root:root');
 	});
 });
+
+describe('ActiveEidos system mode source goes through ActiveDom (E2)', () => {
+	it('resolves the media query from dom.getWindow() and subscribes via dom.listen', () => {
+		// jsdom has no `globalThis.matchMedia`, which is exactly the E2 defect's
+		// blind spot: the raw path reads the GLOBAL window, so an eidos booted
+		// for an iframe/popup (dom.targetWindow) would watch the wrong window —
+		// and in this test, none. Routing through the injected dom makes the
+		// stub window's matchMedia the one that is read and listened to.
+		// One mql PER query — the dom's reduced-motion tracker also consults
+		// matchMedia on this window, and a shared stub would count ITS listener.
+		const mqls = new Map<string, { matches: boolean; listeners: Array<() => void> }>();
+		const stubWin = {
+			innerWidth: 1024,
+			innerHeight: 768,
+			devicePixelRatio: 1,
+			document,
+			matchMedia: (query: string) => {
+				const entry = mqls.get(query) ?? { matches: query.includes('dark'), listeners: [] };
+				mqls.set(query, entry);
+				return {
+					matches: entry.matches,
+					addEventListener: (_: string, fn: () => void) => void entry.listeners.push(fn),
+					removeEventListener: () => {}
+				};
+			},
+			addEventListener: () => {},
+			removeEventListener: () => {}
+		} as unknown as Window;
+		const dom = createActiveDom({ targetWindow: stubWin });
+		const listenSpy = vi.spyOn(dom, 'listen');
+
+		// No `mode`, no `modeSource`, no `preferences` — the boot falls to the
+		// system color-scheme source, which must consult the injected dom.
+		createActiveEidos({ dom, styleHost: document.head, styleId: 'e2-probe' });
+
+		const scheme = mqls.get('(prefers-color-scheme: dark)');
+		expect(scheme).toBeDefined();
+		expect(scheme!.listeners).toHaveLength(1);
+		expect(listenSpy).toHaveBeenCalledWith(
+			expect.objectContaining({ matches: true }),
+			'change',
+			expect.any(Function)
+		);
+	});
+});
+
+describe('ActiveEidos scheme re-derive failure keeps the last good block (E3)', () => {
+	it('keeps the previous scheme CSS and does not strip the page', () => {
+		// The silent path the audit named: applyColorScheme builds EAGERLY at
+		// call time (an invalid seed throws in the caller's face — correct),
+		// but the RE-derive inside apply() on a preference change used to
+		// catch, return '' and thereby DELETE the previously good <style>
+		// block. Injecting the failure through config is IMPOSSIBLE — the
+		// config validator is fail-closed and rejects broken donor scales at
+		// the door — so the failure is injected at the exact throw site the
+		// audit named: `buildScheme` blowing up on the re-derive only.
+		const { preferences, setMode } = preferencesHarness();
+		const dom = createActiveDom();
+		const eidos = createActiveEidos({
+			preferences,
+			dom,
+			styleHost: document.head,
+			styleId: 'e3-probe'
+		});
+
+		eidos.applyColorScheme('#3e63dd');
+		const good = document.getElementById('e3-probe-scheme')?.textContent;
+		expect(good).toBeTruthy();
+
+		schemeBuildFailure.fail = true;
+		try {
+			setMode('dark');
+		} finally {
+			schemeBuildFailure.fail = false;
+		}
+
+		const after = document.getElementById('e3-probe-scheme')?.textContent;
+		expect(after).toBe(good);
+
+		eidos.dispose();
+	});
+});