diff --git a/docs/branch-review-records/417c3d2bbb8346fc650dc4bed9db149912fc13abb7aaf5fc9d7e6f75a3db0fa1.record.md b/docs/branch-review-records/417c3d2bbb8346fc650dc4bed9db149912fc13abb7aaf5fc9d7e6f75a3db0fa1.record.md
new file mode 100644
index 0000000000..a09aba63e7
--- /dev/null
+++ b/docs/branch-review-records/417c3d2bbb8346fc650dc4bed9db149912fc13abb7aaf5fc9d7e6f75a3db0fa1.record.md
@@ -0,0 +1 @@
+| 2026-08-15 | codex/fix-ecg-animation-on-mobile-devices | d4662baa81ba738b2278f624f213db416fde95a5 | review-and-fix | Merged latest main, resolved the CSS-test conflict, and fixed the WebKit late-notice test race | Focused Vitest 2/2; design-system contract; changed-file ESLint; typecheck; Prettier; branch-review, outstanding-issues, ledger-discipline and final-merge audit. Browser/provider gates not run locally. |
diff --git a/src/app/globals.css b/src/app/globals.css
index 2f704cc2f3..20630183fe 100644
--- a/src/app/globals.css
+++ b/src/app/globals.css
@@ -231,8 +231,8 @@
   --animate-dialog-rise: dialog-rise 220ms cubic-bezier(0.22, 1, 0.36, 1) both;
   --animate-action-tray-in: action-tray-in var(--swipe-duration, 160ms) cubic-bezier(0.22, 1, 0.36, 1) both;
   --animate-shimmer: shimmer 1.4s linear infinite;
-  --animate-answer-ecg: answer-ecg-sweep 1.8s linear infinite;
-  --animate-answer-ecg-compact: answer-ecg-sweep 1.6s linear infinite;
+  --animate-answer-ecg: answer-ecg-pulse 1.8s ease-in-out infinite;
+  --animate-answer-ecg-compact: answer-ecg-pulse 1.6s ease-in-out infinite;
 }
 
 /* Theme tokens */
@@ -3419,14 +3419,16 @@ td,
   }
 }
 
-/* 320 → 0 is equivalent to 0 → -320 modulo the dash period, without
-   WebKit's unreliable negative SVG dash-offset interpolation. */
-@keyframes answer-ecg-sweep {
-  from {
-    stroke-dashoffset: 320;
+/* Animate a compositable CSS property rather than SVG stroke-dashoffset.
+   Mobile WebKit can report the dash animation as running without repainting it,
+   especially in an installed PWA. Opacity produces a visible ECG pulse in both. */
+@keyframes answer-ecg-pulse {
+  0%,
+  100% {
+    opacity: 0.2;
   }
-  to {
-    stroke-dashoffset: 0;
+  50% {
+    opacity: 1;
   }
 }
 
diff --git a/src/components/clinical-dashboard/answer-status.tsx b/src/components/clinical-dashboard/answer-status.tsx
index 6f7ef60bb1..f0c1641d95 100644
--- a/src/components/clinical-dashboard/answer-status.tsx
+++ b/src/components/clinical-dashboard/answer-status.tsx
@@ -227,7 +227,6 @@ function AnswerActivityTrace({ density }: { density: AnswerProgressDensity }) {
           strokeWidth={compact ? 1.75 : 2}
           strokeLinecap="round"
           strokeLinejoin="round"
-          strokeDasharray="36 284"
           vectorEffect="non-scaling-stroke"
           className="answer-activity-trace__sweep text-[color:var(--clinical-accent)] forced-colors:text-[Highlight]"
         />
diff --git a/tests/answer-activity-trace-css.test.ts b/tests/answer-activity-trace-css.test.ts
index 47105e9d0f..8d0de75a3a 100644
--- a/tests/answer-activity-trace-css.test.ts
+++ b/tests/answer-activity-trace-css.test.ts
@@ -28,11 +28,11 @@ describe("answer activity trace CSS", () => {
     expect(globalsCss).not.toMatch(/\.answer-activity-trace\s*{[^}]*contain:\s*paint;/s);
   });
 
-  it("cycles through the positive dash-offset equivalent for WebKit", () => {
-    const sweep = keyframes("answer-ecg-sweep");
+  it("pulses with opacity instead of WebKit-unreliable SVG dash offsets", () => {
+    const pulse = keyframes("answer-ecg-pulse");
 
-    expect(sweep).toMatch(/from\s*{\s*stroke-dashoffset:\s*320;/);
-    expect(sweep).toMatch(/to\s*{\s*stroke-dashoffset:\s*0;/);
-    expect(sweep).not.toMatch(/stroke-dashoffset:\s*-/);
+    expect(pulse).toMatch(/opacity:\s*0\.2;/);
+    expect(pulse).toMatch(/opacity:\s*1;/);
+    expect(pulse).not.toMatch(/stroke-dashoffset/);
   });
 });
diff --git a/tests/answer-progress-ui-smoke.spec.ts b/tests/answer-progress-ui-smoke.spec.ts
index 01b7121bf5..eade42ba9e 100644
--- a/tests/answer-progress-ui-smoke.spec.ts
+++ b/tests/answer-progress-ui-smoke.spec.ts
@@ -42,6 +42,15 @@ async function fillHydratedAnswerQuestion(page: Page, value: string) {
   return submit;
 }
 
+async function dismissBlockingPwaNotice(page: Page) {
+  const dismiss = page.getByRole("button", { name: /Dismiss (?:offline notice|update notice|install)/ }).first();
+  const noticeAppeared = await dismiss
+    .waitFor({ state: "visible", timeout: 2_000 })
+    .then(() => true)
+    .catch(() => false);
+  if (noticeAppeared) await dismiss.click();
+}
+
 async function mockDashboardApis(page: Page) {
   await page.route("**/*", async (route) => {
     const url = new URL(route.request().url());
@@ -435,6 +444,7 @@ test("follow-up answer generation stays compact above the previous answer", asyn
   await mockDashboardApis(page);
   await installSuccessfulThenHoldingAnswerStreams(page);
   await page.goto("/?mode=answer", { waitUntil: "domcontentloaded" });
+  await dismissBlockingPwaNotice(page);
 
   const submit = await fillHydratedAnswerQuestion(page, "Lithium dosing");
   await submit.click();
@@ -466,7 +476,7 @@ test("follow-up answer generation stays compact above the previous answer", asyn
         timingFunction: style.animationTimingFunction,
       };
     }),
-  ).toEqual({ duration: "1.6s", iterationCount: "infinite", timingFunction: "linear" });
+  ).toEqual({ duration: "1.6s", iterationCount: "infinite", timingFunction: "ease-in-out" });
   const stop = progress.getByRole("button", { name: "Stop generating answer" });
   expect((await stop.boundingBox())?.height ?? 0).toBeGreaterThanOrEqual(48);
 
@@ -528,6 +538,7 @@ test("answer progress keeps focus, reduced-motion, and forced-colour behavior in
   await mockDashboardApis(page);
   await installHoldingAnswerStream(page);
   await page.goto("/?mode=answer", { waitUntil: "domcontentloaded" });
+  await dismissBlockingPwaNotice(page);
 
   const submit = await fillHydratedAnswerQuestion(page, "Lithium dosing");
   await submit.click();
@@ -566,11 +577,23 @@ test("answer progress keeps focus, reduced-motion, and forced-colour behavior in
       };
     }),
   ).toEqual({
-    name: "answer-ecg-sweep",
+    name: "answer-ecg-pulse",
     duration: "1.8s",
     iterationCount: "infinite",
-    timingFunction: "linear",
+    timingFunction: "ease-in-out",
   });
+  expect(
+    await activityTraceSweep.evaluate(async (trace) => {
+      const animation = trace.getAnimations()[0];
+      animation.pause();
+      animation.currentTime = 0;
+      await new Promise(requestAnimationFrame);
+      const restingOpacity = getComputedStyle(trace).opacity;
+      animation.currentTime = 900;
+      await new Promise(requestAnimationFrame);
+      return { restingOpacity, peakOpacity: getComputedStyle(trace).opacity };
+    }),
+  ).toEqual({ restingOpacity: "0.2", peakOpacity: "1" });
 
   await page.emulateMedia({ reducedMotion: "reduce", forcedColors: "active" });
   await expect(currentStage.locator('[data-slot="answer-progress-stage-marker"]')).toBeVisible();