diff --git a/simulator/e2e/tests/mood-grade.spec.ts b/simulator/e2e/tests/mood-grade.spec.ts
new file mode 100644
index 0000000..1f97027
--- /dev/null
+++ b/simulator/e2e/tests/mood-grade.spec.ts
@@ -0,0 +1,46 @@
+import { test, expect, Page } from "@playwright/test";
+
+// Bug: the Dark/Light Mood grade was dropped DURING an altitude morph — the morph
+// showed ungraded ("normal") and the grade snapped back only on landing. Both render
+// paths were at fault: the WebGL canvas set filter "none" while `busy`, and the
+// fallback set #vid's filter "none" when a morph loaded. The grade must ride through.
+
+async function boot(page: Page) {
+  await page.goto("/");
+  await page.waitForFunction(() => (window as any).__hefReady === true, null, { timeout: 45_000 });
+  await page.locator("#welcome-launch").click();
+  await page.waitForSelector("#welcome", { state: "detached", timeout: 10_000 });
+  await expect(page.locator("#scale-name")).toBeVisible();
+}
+
+test("Dark Mood grade stays applied to the morph while scrubbing", async ({ page }) => {
+  await boot(page);
+  // Drive Mood hard dark; wait for the debounced render to build the grade.
+  await page.evaluate(() => {
+    const m = document.querySelector("#mood") as HTMLInputElement;
+    m.value = "-4";
+    m.dispatchEvent(new Event("input", { bubbles: true }));
+  });
+  await page.waitForTimeout(300);
+
+  // Begin a drag → a morph plays (busy = true). Sample the VISIBLE morph surface:
+  // the paint canvas (WebGL path) or #vid (fallback). #vid-loop is hidden mid-morph,
+  // so we deliberately exclude it.
+  const box = (await page.locator("#dial").boundingBox())!;
+  const cx = box.x + box.width / 2, cy = box.y + box.height / 2;
+  await page.mouse.move(cx, cy - 30);
+  await page.mouse.down();
+  await page.mouse.move(cx + 18, cy - 24, { steps: 8 });
+  await page.waitForFunction(() => (document.querySelector("#vid") as HTMLVideoElement).currentTime > 0, null, { timeout: 5000 });
+
+  const filters = await page.evaluate(() => [
+    (document.querySelector("#paint") as HTMLElement).style.filter,
+    (document.querySelector("#vid") as HTMLElement).style.filter,
+  ]);
+  await page.mouse.up();
+
+  // Dark grade is brightness(<1)… — at least one visible surface must carry it.
+  // Before the fix both were "none" here.
+  const graded = filters.some((f) => /brightness\(/.test(f) && !/brightness\(1(\.0+)?\)/.test(f));
+  expect(graded, `visible morph surface must carry the dark grade; saw ${JSON.stringify(filters)}`).toBe(true);
+});
diff --git a/simulator/static/app.js b/simulator/static/app.js
index 18004dc..1a0ce84 100644
--- a/simulator/static/app.js
+++ b/simulator/static/app.js
@@ -451,11 +451,13 @@ function paintLoop() {
     if (paint.width !== w || paint.height !== h) { paint.width = w; paint.height = h; }
     gl.viewport(0, 0, w, h);
     try { gl.texImage2D(gl.TEXTURE_2D, 0, gl.RGB, gl.RGB, gl.UNSIGNED_BYTE, src); } catch (_) {}
-    // No painterly restyle during a ring transition (busy) — show it raw.
+    // No painterly DREAM during a ring transition (busy) — show the morph crisp.
+    // The Dark/Light mood GRADE, however, must ride through the transition too
+    // (else the morph shows ungraded and the grade snaps back only on landing).
     gl.uniform1f(uAmt, busy ? 0 : dreamIntensity);
     gl.uniform2f(uTexel, 1 / w, 1 / h);
     gl.drawArrays(gl.TRIANGLES, 0, 3);
-    paint.style.filter = busy ? "none" : gradeFilter;
+    paint.style.filter = gradeFilter;
   }
   // Animate per-frame: re-place keyframed tracks AND re-evaluate time-windowed
   // labels (a label enters/leaves frame as the loop plays) against playback time.
@@ -983,7 +985,10 @@ function rebuildSegment(lo, enteredFrom) {
     overlay.style.opacity = "0";
     affectLayer.style.opacity = "0";
     tint.style.opacity = "0";
-    vid.style.filter = "none";
+    // WebGL path: the graded canvas sits on top, so #vid stays raw (no double-grade).
+    // Fallback path: #vid IS the visible surface, so it must carry the mood grade
+    // through the morph (setting "none" here was the "morph ignores Mood" bug).
+    vid.style.filter = paintOK ? "none" : gradeFilter;
     vid.loop = false;
     if (vid.dataset.morph !== file) {
       vid.dataset.morph = file;