diff --git a/packages/studio/src/components/storyboard/FramePoster.test.tsx b/packages/studio/src/components/storyboard/FramePoster.test.tsx
new file mode 100644
index 000000000..fb64a4494
--- /dev/null
+++ b/packages/studio/src/components/storyboard/FramePoster.test.tsx
@@ -0,0 +1,64 @@
+// @vitest-environment happy-dom
+
+import React, { act } from "react";
+import { createRoot, type Root } from "react-dom/client";
+import { afterEach, describe, expect, it } from "vitest";
+import { FramePoster } from "./FramePoster";
+
+(globalThis as unknown as { IS_REACT_ACT_ENVIRONMENT: boolean }).IS_REACT_ACT_ENVIRONMENT = true;
+
+const roots: Root[] = [];
+
+afterEach(() => {
+  act(() => roots.splice(0).forEach((root) => root.unmount()));
+  document.body.replaceChildren();
+});
+
+// A fresh host per render: several cases compare two surfaces side by side.
+function renderPoster(surface?: "tile" | "hero"): HTMLImageElement {
+  const host = document.createElement("div");
+  document.body.appendChild(host);
+  const root = createRoot(host);
+  roots.push(root);
+  act(() => {
+    root.render(
+      <FramePoster
+        projectId="demo"
+        src="frames/01-hero.html"
+        seconds={3}
+        title="hero"
+        surface={surface}
+      />,
+    );
+  });
+  const img = host.querySelector("img");
+  if (!img) throw new Error("poster did not render an <img>");
+  return img;
+}
+
+describe("FramePoster", () => {
+  // Regression: the hero and the tile shared one bounded poster, so the frame
+  // detail view — the sketch pass's only picture — showed a 240x135 capture
+  // upscaled past 7x on a retina display, and body copy was unreadable.
+  it("captures the focus hero at the composition's own dimensions", () => {
+    const url = new URL(renderPoster("hero").src);
+
+    expect(url.searchParams.get("output")).toBe("source");
+    expect(url.pathname).toBe("/api/projects/demo/thumbnail/frames/01-hero.html");
+  });
+
+  it("leaves the contact-sheet tile on the route's bounded preview capture", () => {
+    const url = new URL(renderPoster("tile").src);
+
+    expect(url.searchParams.has("output")).toBe(false);
+  });
+
+  it("defaults to the tile surface", () => {
+    expect(new URL(renderPoster().src).search).toBe(new URL(renderPoster("tile").src).search);
+  });
+
+  it("letterboxes only the hero, so a tile still fills its cell", () => {
+    expect(renderPoster("hero").className).toContain("object-contain");
+    expect(renderPoster("tile").className).toContain("object-cover");
+  });
+});
diff --git a/packages/studio/src/components/storyboard/FramePoster.tsx b/packages/studio/src/components/storyboard/FramePoster.tsx
index 60d41e044..e58de6e9d 100644
--- a/packages/studio/src/components/storyboard/FramePoster.tsx
+++ b/packages/studio/src/components/storyboard/FramePoster.tsx
@@ -8,8 +8,15 @@ export interface FramePosterProps {
   /** Time (seconds) to seek to for the poster. */
   seconds: number;
   title: string;
-  /** `cover` fills+crops (contact-sheet tile); `contain` letterboxes (focus hero). */
-  fit?: "cover" | "contain";
+  /**
+   * Where this poster is rendered. A contact-sheet tile is ~300px wide and there
+   * are many of them; the focus hero is up to 900px wide and there is exactly
+   * one. That single difference decides both the crop and how much resolution
+   * the server has to capture, so it is one prop rather than two that can
+   * disagree: `tile` fills+crops at the route's bounded preview density, `hero`
+   * letterboxes at the composition's own dimensions.
+   */
+  surface?: "tile" | "hero";
   /**
    * Project content signature to key the poster URL on. The thumbnail route
    * regenerates when the frame's source changes, but the browser only refetches
@@ -30,14 +37,14 @@ export function FramePoster({
   src,
   seconds,
   title,
-  fit = "cover",
+  surface = "tile",
   posterVersion,
 }: FramePosterProps) {
   const [failed, setFailed] = useState(false);
   // The <img> is reused (no key) when a tile/hero swaps to a different frame, so a
   // prior load error would stick. Reset when the poster target changes — including
   // a new posterVersion, so a frame that failed mid-write retries once it settles.
-  useEffect(() => setFailed(false), [src, seconds, posterVersion]);
+  useEffect(() => setFailed(false), [src, seconds, posterVersion, surface]);
   if (failed) {
     return (
       <div className="flex h-full w-full items-center justify-center text-[11px] text-neutral-600">
@@ -50,6 +57,11 @@ export function FramePoster({
     seekTime: seconds,
     duration: 0,
     origin: window.location.origin,
+    // The hero is the sketch pass's only picture (references/review-loop.md), and
+    // it is shown large. Bounded to the preview cap it arrives at 240x135 and
+    // upscales past 7x on a retina display, which is unreadable for exactly the
+    // body copy and labels this pass exists to confirm.
+    ...(surface === "hero" ? { output: "source" as const } : {}),
   });
   if (posterVersion) {
     const withVersion = new URL(url, window.location.origin);
@@ -63,7 +75,7 @@ export function FramePoster({
       draggable={false}
       loading="lazy"
       onError={() => setFailed(true)}
-      className={`h-full w-full ${fit === "contain" ? "object-contain" : "object-cover"}`}
+      className={`h-full w-full ${surface === "hero" ? "object-contain" : "object-cover"}`}
     />
   );
 }
diff --git a/packages/studio/src/components/storyboard/StoryboardFrameFocus.tsx b/packages/studio/src/components/storyboard/StoryboardFrameFocus.tsx
index 25883067a..dacc060cd 100644
--- a/packages/studio/src/components/storyboard/StoryboardFrameFocus.tsx
+++ b/packages/studio/src/components/storyboard/StoryboardFrameFocus.tsx
@@ -224,7 +224,7 @@ export function StoryboardFrameFocus({
                 src={frame.src}
                 seconds={posterTime(frame)}
                 title={title}
-                fit="contain"
+                surface="hero"
                 posterVersion={posterVersion}
               />
             ) : (
diff --git a/packages/studio/src/player/components/CompositionThumbnail.test.ts b/packages/studio/src/player/components/CompositionThumbnail.test.ts
index 3ec97bd63..dd9ef04d3 100644
--- a/packages/studio/src/player/components/CompositionThumbnail.test.ts
+++ b/packages/studio/src/player/components/CompositionThumbnail.test.ts
@@ -76,6 +76,18 @@ describe("buildCompositionThumbnailUrl", () => {
       "http://localhost:3000/api/projects/demo/thumbnail/index.html?t=2.00&v=v3&selector=.card&selectorIndex=2",
     );
   });
+
+  it("asks for source density only when a caller opts in", () => {
+    const base = {
+      previewUrl: "/api/projects/demo/preview",
+      seekTime: 1,
+      duration: 0,
+      origin: "http://localhost:3000",
+    };
+
+    expect(buildCompositionThumbnailUrl(base)).not.toContain("output=");
+    expect(buildCompositionThumbnailUrl({ ...base, output: "source" })).toContain("output=source");
+  });
 });
 
 describe("CompositionThumbnail", () => {
diff --git a/packages/studio/src/player/components/CompositionThumbnail.tsx b/packages/studio/src/player/components/CompositionThumbnail.tsx
index 837984ad6..a30e4b485 100644
--- a/packages/studio/src/player/components/CompositionThumbnail.tsx
+++ b/packages/studio/src/player/components/CompositionThumbnail.tsx
@@ -31,6 +31,7 @@ export function buildCompositionThumbnailUrl({
   selector,
   selectorIndex,
   origin,
+  output,
 }: {
   previewUrl: string;
   seekTime?: number;
@@ -38,6 +39,13 @@ export function buildCompositionThumbnailUrl({
   selector?: string;
   selectorIndex?: number;
   origin: string;
+  /**
+   * Capture density. Omitted, the route bounds the image to its preview cap —
+   * right for the timeline, where thumbnails are small and numerous and their
+   * decoded bytes are budgeted. `"source"` captures at the composition's own
+   * dimensions, for the rare surface that shows one poster large enough to read.
+   */
+  output?: "source";
 }): string {
   const thumbnailBase = previewUrl
     .replace("/preview/comp/", "/thumbnail/")
@@ -45,6 +53,7 @@ export function buildCompositionThumbnailUrl({
   const thumbnailUrl = new URL(thumbnailBase, origin);
   thumbnailUrl.searchParams.set("t", (seekTime + duration / 2).toFixed(2));
   thumbnailUrl.searchParams.set("v", THUMBNAIL_URL_VERSION);
+  if (output) thumbnailUrl.searchParams.set("output", output);
   if (selector) {
     thumbnailUrl.searchParams.set("selector", selector);
     if (selectorIndex != null && selectorIndex > 0) {