diff --git a/frontend/libs/components/video-editor/src/lib/services/waveform-cache/service.spec.ts b/frontend/libs/components/video-editor/src/lib/services/waveform-cache/service.spec.ts
new file mode 100644
--- /dev/null
+++ b/frontend/libs/components/video-editor/src/lib/services/waveform-cache/service.spec.ts
@@ -0,0 +1,76 @@
+import { WaveformCache } from "./service";
+
+const requests: Array<{ resolve: (response: Response) => void }> = [];
+const observed: Promise<unknown>[] = [];
+let fetchSource: ReturnType<typeof vi.fn>;
+
+// Failed HTTP responses do not reach audio decoding or retime calculations.
+// Fail loudly if a test accidentally exercises those unrelated paths.
+vi.mock("../../media/audio", () => ({ createAudioContext: () => { throw new Error("Unexpected decoder call"); } }));
+vi.mock("../../media/waveform-summary", () => ({ buildSourceWaveformSummary: () => { throw new Error("Unexpected waveform calculation"); } }));
+
+beforeEach(() => {
+  requests.length = 0;
+  observed.length = 0;
+  fetchSource = vi.fn(() => new Promise<Response>((resolve) => requests.push({ resolve })));
+  vi.stubGlobal("fetch", fetchSource);
+});
+
+afterEach(async () => {
+  for (const request of requests) request.resolve(new Response("", { status: 503 }));
+  await Promise.allSettled(observed);
+  vi.unstubAllGlobals();
+});
+
+it("keeps the replacement download cached when an invalidated source request fails", async () => {
+  const cache = new WaveformCache();
+  const previous = requestSummary(cache);
+  cache.clearSource({ sourceKey: "media:audio-a" });
+  const replacement = requestSummary(cache);
+  requests[0].resolve(new Response("", { status: 503 }));
+  await expect(previous).rejects.toThrow("Failed to fetch waveform source: 503");
+
+  const joined = requestSummary(cache);
+  expect(fetchSource).toHaveBeenCalledTimes(2);
+  expect(joined).toBe(replacement);
+});
+
+it("keeps the new project request cached after clearing all older summaries", async () => {
+  const cache = new WaveformCache();
+  const previous = requestSummary(cache);
+  cache.clearAll();
+  const replacement = requestSummary(cache);
+  requests[0].resolve(new Response("", { status: 503 }));
+  await expect(previous).rejects.toThrow("Failed to fetch waveform source: 503");
+
+  const joined = requestSummary(cache);
+  expect(fetchSource).toHaveBeenCalledTimes(2);
+  expect(joined).toBe(replacement);
+});
+
+it("still shares concurrent requests for the same active source", () => {
+  const cache = new WaveformCache();
+  const first = requestSummary(cache);
+  const second = requestSummary(cache);
+  expect(first).toBe(second);
+  expect(fetchSource).toHaveBeenCalledTimes(1);
+});
+
+it("still retries when the current source request itself fails", async () => {
+  const cache = new WaveformCache();
+  const failed = requestSummary(cache);
+  requests[0].resolve(new Response("", { status: 404 }));
+  await expect(failed).rejects.toThrow("Failed to fetch waveform source: 404");
+  const retry = requestSummary(cache);
+  expect(retry).not.toBe(failed);
+  expect(fetchSource).toHaveBeenCalledTimes(2);
+});
+
+function requestSummary(cache: WaveformCache) {
+  const promise = cache.getSourceSummary({ sourceKey: "media:audio-a", audioUrl: "https://media.example/audio-a.wav" });
+  // Record and immediately observe every potentially rejected promise so
+  // teardown can settle pending fetches without leaking unhandled rejection.
+  observed.push(promise);
+  void promise.catch(() => {});
+  return promise;
+}
diff --git a/frontend/libs/components/video-editor/src/lib/services/waveform-cache/service.ts b/frontend/libs/components/video-editor/src/lib/services/waveform-cache/service.ts
--- a/frontend/libs/components/video-editor/src/lib/services/waveform-cache/service.ts
+++ b/frontend/libs/components/video-editor/src/lib/services/waveform-cache/service.ts
@@ -37,7 +37,9 @@ export class WaveformCache {
       sourceFile,
       audioUrl,
     }).catch((error) => {
-      this.summaries.delete(sourceKey);
+      if (this.summaries.get(sourceKey) === promise) {
+        this.summaries.delete(sourceKey);
+      }
       throw error;
     });