diff --git a/packages/cli/src/utils/compositionFps.test.ts b/packages/cli/src/utils/compositionFps.test.ts
index 7c2a5b37bc..167cc00e69 100644
--- a/packages/cli/src/utils/compositionFps.test.ts
+++ b/packages/cli/src/utils/compositionFps.test.ts
@@ -12,6 +12,43 @@ describe("readCompositionFps", () => {
     expect(readCompositionFps(html)).toBe("24");
   });
 
+  it.each(["DATA-FPS", "Data-FpS"])("reads an HTML %s attribute", (attribute) => {
+    const html = wrap(`<div data-composition-id="root" data-root="true" ${attribute}="24">x</div>`);
+    expect(readCompositionFps(html)).toBe("24");
+  });
+
+  it("prefers an explicit root with mixed-case HTML attribute names", () => {
+    const html = wrap(
+      '<div data-composition-id="other" data-root="TRUE" data-fps="60"></div>' +
+        '<div DATA-COMPOSITION-ID="root" Data-Root="true" DATA-FPS="24">x</div>',
+    );
+    expect(readCompositionFps(html)).toBe("24");
+  });
+
+  it("reads the outermost composition with mixed-case HTML attribute names", () => {
+    const html = wrap(
+      '<div DATA-COMPOSITION-ID="root" Data-Fps="48"><div data-composition-id="child" data-fps="12">x</div></div>',
+    );
+    expect(readCompositionFps(html)).toBe("48");
+  });
+
+  it.each([
+    'DATA-FPS="24" data-fps="60"',
+    'Data-FpS="24" DATA-FPS="60"',
+    'data-fps="24" DATA-FPS="60"',
+  ])("keeps the first duplicate HTML attribute in %s", (attributes) => {
+    const html = wrap(`<div data-composition-id="root" ${attributes}>x</div>`);
+    expect(readCompositionFps(html)).toBe("24");
+  });
+
+  it("keeps the first duplicate data-root value when selecting the root", () => {
+    const html = wrap(
+      '<div data-composition-id="other" DATA-ROOT="false" data-root="true" data-fps="60"></div>' +
+        '<div data-composition-id="root" data-root="true" data-fps="24">x</div>',
+    );
+    expect(readCompositionFps(html)).toBe("24");
+  });
+
   it("reads data-fps from the outermost composition when no data-root is marked", () => {
     const html = wrap(
       '<div data-composition-id="root" data-fps="48"><div data-composition-id="child" data-fps="12">x</div></div>',
@@ -77,6 +114,16 @@ describe("defaultCloudFps", () => {
     expect(String(warn.mock.calls[0]?.[0])).toContain(`data-fps="${fps}"`);
   });
 
+  it("reads mixed-case HTML attributes before validating the cloud fps", () => {
+    const warn = vi.spyOn(console, "warn").mockImplementation(() => {});
+    const dir = makeProject(
+      '<div DATA-COMPOSITION-ID="root" DATA-ROOT="true" DATA-FPS="24">x</div>',
+    );
+
+    expect(defaultCloudFps(dir)).toBe(24);
+    expect(warn).not.toHaveBeenCalled();
+  });
+
   it("uses 30 without warning when index.html has no data-fps", () => {
     const warn = vi.spyOn(console, "warn").mockImplementation(() => {});
     expect(
diff --git a/packages/cli/src/utils/compositionFps.ts b/packages/cli/src/utils/compositionFps.ts
index f2af7f8c9c..1df7d199f3 100644
--- a/packages/cli/src/utils/compositionFps.ts
+++ b/packages/cli/src/utils/compositionFps.ts
@@ -4,6 +4,14 @@ import { DISTRIBUTED_FPS, type DistributedFps, isDistributedFps } from "@hyperfr
 import { parseHTML } from "linkedom";
 import { c } from "../ui/colors.js";
 
+function getHtmlAttribute(element: Element, name: string): string | null {
+  // linkedom preserves spelling; HTML names match without case and keep the first duplicate.
+  return (
+    Array.from(element.attributes).find((attribute) => attribute.name.toLowerCase() === name)
+      ?.value ?? null
+  );
+}
+
 /**
  * Read a composition's declared frame rate from its root element's `data-fps`
  * attribute — the same attribute the runtime honors (core/runtime/init.ts) — so
@@ -24,15 +32,14 @@ export function readCompositionFps(html: string): string | null {
     return null;
   }
 
-  const explicitRoot = doc.querySelector('[data-composition-id][data-root="true"]');
+  const compositions = Array.from(doc.querySelectorAll("*")).filter(
+    (element) => getHtmlAttribute(element, "data-composition-id") !== null,
+  );
   const root =
-    explicitRoot ??
-    Array.from(doc.querySelectorAll("[data-composition-id]")).find(
-      (el) => !el.parentElement?.closest("[data-composition-id]"),
-    ) ??
-    null;
+    compositions.find((element) => getHtmlAttribute(element, "data-root") === "true") ??
+    compositions[0];
 
-  const raw = root?.getAttribute("data-fps")?.trim();
+  const raw = root ? getHtmlAttribute(root, "data-fps")?.trim() : undefined;
   return raw ? raw : null;
 }
 
diff --git a/packages/cli/src/utils/renderArgs.test.ts b/packages/cli/src/utils/renderArgs.test.ts
index 5ed0bb54d2..84fc1ca0ad 100644
--- a/packages/cli/src/utils/renderArgs.test.ts
+++ b/packages/cli/src/utils/renderArgs.test.ts
@@ -332,6 +332,21 @@ describe("resolveDefaultFpsArg", () => {
     }
   });
 
+  it("uses an uppercase HTML data-fps declaration when --fps is omitted", () => {
+    const project = makeProject();
+    try {
+      writeFileSync(
+        project.indexPath,
+        '<!DOCTYPE html><html><body><div data-composition-id="root" DATA-FPS="24">x</div></body></html>',
+      );
+
+      expect(resolveDefaultFpsArg(undefined, project.dir, project.indexPath, undefined)).toBe("24");
+      expect(resolveDefaultFpsArg("60", project.dir, project.indexPath, undefined)).toBe("60");
+    } finally {
+      project.cleanup();
+    }
+  });
+
   it("keeps an explicit --fps value ahead of any composition default", () => {
     const project = makeProject();
     try {