diff --git a/packages/lint/src/rules/slideshow.test.ts b/packages/lint/src/rules/slideshow.test.ts
index 8b7ed694649..4c801e66bf0 100644
--- a/packages/lint/src/rules/slideshow.test.ts
+++ b/packages/lint/src/rules/slideshow.test.ts
@@ -51,6 +51,22 @@ describe("slideshow lint rule", () => {
     expect(findings[0]!.code).toBe("slideshow_invalid");
   });
 
+  it.each([null, {}, { id: "h1", label: 42, target: "deep" }])(
+    "reports malformed hotspot %j as a structure finding without crashing lint",
+    async (hotspot) => {
+      const html = `<div data-composition-id="c" data-width="1920" data-height="1080">
+        <div data-composition-id="a" data-start="0" data-duration="5"></div>
+        <script type="application/hyperframes-slideshow+json">${JSON.stringify({
+          slides: [{ sceneId: "a", hotspots: [hotspot] }],
+          slideSequences: [{ id: "deep", label: "Deep", slides: [{ sceneId: "a" }] }],
+        })}</script>
+      </div>`;
+      expect(await findSlideshow(html)).toEqual([
+        expect.objectContaining({ code: "slideshow_invalid", severity: "error" }),
+      ]);
+    },
+  );
+
   it("passes when sceneId resolves to a data-composition-id element (no .clip[id])", async () => {
     const html = `<div data-composition-id="c" data-width="1920" data-height="1080">
       <div data-composition-id="scene-a" data-start="0" data-duration="5"></div>
diff --git a/packages/parsers/src/slideshow/parseSlideshow.test.ts b/packages/parsers/src/slideshow/parseSlideshow.test.ts
index 8251a164057..429621d8964 100644
--- a/packages/parsers/src/slideshow/parseSlideshow.test.ts
+++ b/packages/parsers/src/slideshow/parseSlideshow.test.ts
@@ -48,6 +48,56 @@ describe("parseSlideshowManifest", () => {
     </script>`;
     expect(() => parseSlideshowManifest(html)).toThrow();
   });
+
+  it.each([
+    null,
+    42,
+    "branch",
+    [],
+    {},
+    { id: 1, label: "Go", target: "deep" },
+    { id: "h1", label: null, target: "deep" },
+    { id: "h1", label: "Go", target: [] },
+    { id: "h1", label: "Go", target: "deep", region: null },
+    { id: "h1", label: "Go", target: "deep", region: { x: 10, y: 20 } },
+    { id: "h1", label: "Go", target: "deep", region: { x: "10", y: 20, w: 30, h: 40 } },
+  ])("rejects malformed hotspot %j in main-line and branch slides", (hotspot) => {
+    for (const manifest of [
+      { slides: [{ sceneId: "a", hotspots: [hotspot] }] },
+      {
+        slides: [{ sceneId: "a" }],
+        slideSequences: [
+          { id: "deep", label: "Deep", slides: [{ sceneId: "c", hotspots: [hotspot] }] },
+        ],
+      },
+    ]) {
+      const html = `<script type="application/hyperframes-slideshow+json">${JSON.stringify(manifest)}</script>`;
+      expect(() => parseSlideshowManifest(html)).toThrow("not a valid SlideshowManifest");
+    }
+  });
+
+  it("preserves valid hotspot regions and optional hotspot arrays", () => {
+    const manifest = {
+      slides: [
+        {
+          sceneId: "a",
+          hotspots: [
+            { id: "h1", label: "Go", target: "deep", region: { x: 0, y: 12.5, w: 100, h: 20 } },
+          ],
+        },
+      ],
+      slideSequences: [{ id: "deep", label: "Deep", slides: [{ sceneId: "c", hotspots: [] }] }],
+    };
+    const html = `<script type="application/hyperframes-slideshow+json">${JSON.stringify(manifest)}</script>`;
+    expect(parseSlideshowManifest(html)).toEqual(manifest);
+  });
+
+  it("rejects a hotspot region whose JSON number overflows to infinity", () => {
+    const html = `<script type="application/hyperframes-slideshow+json">
+      {"slides":[{"sceneId":"a","hotspots":[{"id":"h1","label":"Go","target":"deep","region":{"x":1e400,"y":0,"w":30,"h":20}}]}]}
+    </script>`;
+    expect(() => parseSlideshowManifest(html)).toThrow("not a valid SlideshowManifest");
+  });
 });
 
 describe("resolveSlideshow", () => {
diff --git a/packages/parsers/src/slideshow/parseSlideshow.ts b/packages/parsers/src/slideshow/parseSlideshow.ts
index a05537ce507..906ed3c6c82 100644
--- a/packages/parsers/src/slideshow/parseSlideshow.ts
+++ b/packages/parsers/src/slideshow/parseSlideshow.ts
@@ -2,6 +2,7 @@
 import type {
   SlideshowManifest,
   SlideRef,
+  SlideHotspot,
   ResolvedSlide,
   ResolvedSlideshow,
   ResolvedSlideSequence,
@@ -52,12 +53,39 @@ function isOptionalBoolean(v: unknown): v is boolean | undefined {
   return v === undefined || typeof v === "boolean";
 }
 
+function isRecord(v: unknown): v is Record<string, unknown> {
+  return typeof v === "object" && v !== null && !Array.isArray(v);
+}
+
+function isHotspotRegion(v: unknown): boolean {
+  return (
+    isRecord(v) &&
+    [v["x"], v["y"], v["w"], v["h"]].every(
+      (coordinate) => typeof coordinate === "number" && Number.isFinite(coordinate),
+    )
+  );
+}
+
+function isSlideHotspot(v: unknown): v is SlideHotspot {
+  return (
+    isRecord(v) &&
+    typeof v["id"] === "string" &&
+    typeof v["label"] === "string" &&
+    typeof v["target"] === "string" &&
+    (v["region"] === undefined || isHotspotRegion(v["region"]))
+  );
+}
+
 function isSlideRef(v: unknown): v is SlideRef {
-  if (typeof v !== "object" || v === null) return false;
-  const r = v as Record<string, unknown>;
+  if (!isRecord(v)) return false;
+  const r = v;
   if (typeof r["sceneId"] !== "string") return false;
   if (!isOptionalNumberArray(r["fragments"])) return false;
-  if (r["hotspots"] !== undefined && !Array.isArray(r["hotspots"])) return false;
+  if (
+    r["hotspots"] !== undefined &&
+    (!Array.isArray(r["hotspots"]) || !r["hotspots"].every(isSlideHotspot))
+  )
+    return false;
   if (!isOptionalBoolean(r["autoplay"])) return false;
   return true;
 }
diff --git a/packages/player/src/slideshow/hyperframes-slideshow.test.ts b/packages/player/src/slideshow/hyperframes-slideshow.test.ts
index b2d3efe67a1..0ed739a6991 100644
--- a/packages/player/src/slideshow/hyperframes-slideshow.test.ts
+++ b/packages/player/src/slideshow/hyperframes-slideshow.test.ts
@@ -1750,6 +1750,14 @@ describe("slideshow parts (pure)", () => {
     expect(parts.player).toBe(root.querySelector("hyperframes-player"));
     expect(parts.manifest.slides.map((s) => s.sceneId)).toEqual(["intro"]);
   });
+
+  it("classifies a malformed hotspot as a malformed island before slideshow initialization", () => {
+    const root = subtree(`<hyperframes-player></hyperframes-player>
+      <script type="application/hyperframes-slideshow+json">${JSON.stringify({
+        slides: [{ sceneId: "intro", startTime: 0, endTime: 1, hotspots: [null] }],
+      })}</script>`);
+    expect(locateSlideshowParts(root)).toEqual({ kind: "incomplete", reason: "malformed-island" });
+  });
 });
 
 // ---------------------------------------------------------------------------