diff --git a/packages/cli/src/commands/validate.test.ts b/packages/cli/src/commands/validate.test.ts
index 2d78f6b392..422250a499 100644
--- a/packages/cli/src/commands/validate.test.ts
+++ b/packages/cli/src/commands/validate.test.ts
@@ -17,6 +17,7 @@ import {
   raceMediaReady,
   resolveNavigationTimeoutMs,
   shouldIgnoreRequestFailure,
+  shouldIgnoreHttpError,
 } from "./validate.js";
 import { waitForPreferredSeekTarget } from "../capture/captureCompositionFrame.js";
 import type { ProjectLintResult } from "../utils/lintProject.js";
@@ -152,6 +153,18 @@ describe("raceMediaReady", () => {
 });
 
 describe("shouldIgnoreRequestFailure", () => {
+  it("ignores only the optional root caption overrides 404/abort", () => {
+    const url = "http://127.0.0.1:3000/caption-overrides.json";
+    expect(shouldIgnoreHttpError(url, 404)).toBe(true);
+    expect(shouldIgnoreRequestFailure(url, "net::ERR_ABORTED", "fetch")).toBe(true);
+    expect(shouldIgnoreHttpError(url, 500)).toBe(false);
+    expect(shouldIgnoreRequestFailure(url, "net::ERR_FAILED", "fetch")).toBe(false);
+    expect(shouldIgnoreHttpError("http://127.0.0.1:3000/transcript.json", 404)).toBe(false);
+    expect(shouldIgnoreHttpError("http://127.0.0.1:3000/assets/caption-overrides.json", 404)).toBe(
+      false,
+    );
+  });
+
   it("ignores aborted media preload requests", () => {
     expect(
       shouldIgnoreRequestFailure("http://127.0.0.1:3000/assets/sfx.wav", "net::ERR_ABORTED"),
diff --git a/packages/cli/src/commands/validate.ts b/packages/cli/src/commands/validate.ts
index e25989d7c0..14b5a33595 100644
--- a/packages/cli/src/commands/validate.ts
+++ b/packages/cli/src/commands/validate.ts
@@ -79,6 +79,7 @@ export function shouldIgnoreRequestFailure(
   errorText: string | undefined,
   resourceType?: string,
 ): boolean {
+  if (errorText === "net::ERR_ABORTED" && isOptionalCaptionOverridesRequest(url)) return true;
   if (errorText !== "net::ERR_ABORTED") return false;
   if (resourceType === "media") return true;
   try {
@@ -88,6 +89,18 @@ export function shouldIgnoreRequestFailure(
   }
 }
 
+export function shouldIgnoreHttpError(url: string, status: number): boolean {
+  return status === 404 && isOptionalCaptionOverridesRequest(url);
+}
+
+function isOptionalCaptionOverridesRequest(url: string): boolean {
+  try {
+    return new URL(url).pathname === "/caption-overrides.json";
+  } catch {
+    return false;
+  }
+}
+
 async function getCompositionDuration(page: import("puppeteer-core").Page): Promise<number> {
   return page.evaluate(() => {
     if (window.__hf?.duration && window.__hf.duration > 0) return window.__hf.duration;
@@ -477,6 +490,7 @@ async function validateInBrowser(
       if (res.status() >= 400) {
         const url = res.url();
         if (url.includes("favicon")) return;
+        if (shouldIgnoreHttpError(url, res.status())) return;
         const path = decodeURIComponent(new URL(url).pathname).replace(/^\//, "");
         errors.push({ level: "error", text: `${res.status()} loading ${path}`, url });
       }
diff --git a/packages/cli/src/utils/checkBrowser.ts b/packages/cli/src/utils/checkBrowser.ts
index 21a12db9dc..ef40f832c7 100644
--- a/packages/cli/src/utils/checkBrowser.ts
+++ b/packages/cli/src/utils/checkBrowser.ts
@@ -13,7 +13,11 @@ import {
   seekCompositionTimeline,
   waitForPreferredSeekTarget,
 } from "../capture/captureCompositionFrame.js";
-import { auditClipDurations, shouldIgnoreRequestFailure } from "../commands/validate.js";
+import {
+  auditClipDurations,
+  shouldIgnoreHttpError,
+  shouldIgnoreRequestFailure,
+} from "../commands/validate.js";
 import { loadBrowserScript } from "../commands/layout.js";
 import { normalizeErrorMessage } from "./errorMessage.js";
 import { ambiguousIssue, type MotionFrame } from "./motionAudit.js";
@@ -381,6 +385,7 @@ function wireNetworkListeners(page: Page, drafts: RuntimeDraft[], currentTime: (
     if (response.status() < 400) return;
     const url = response.url();
     if (url.includes("favicon")) return;
+    if (shouldIgnoreHttpError(url, response.status())) return;
     drafts.push({
       code: "http_error",
       severity: "error",
diff --git a/packages/core/src/runtime/captionOverrides.test.ts b/packages/core/src/runtime/captionOverrides.test.ts
index e62cf5f5a2..d0a941e5d2 100644
--- a/packages/core/src/runtime/captionOverrides.test.ts
+++ b/packages/core/src/runtime/captionOverrides.test.ts
@@ -2,7 +2,7 @@
 import { afterEach, describe, expect, it, vi } from "vitest";
 import { applyCaptionOverrides } from "./captionOverrides";
 
-function installCaptionOverrideFetch(overrides: unknown[]) {
+function installCaptionOverrideFetch(overrides: unknown) {
   vi.stubGlobal("fetch", async () => ({
     ok: true,
     async json() {
@@ -60,6 +60,49 @@ afterEach(() => {
 });
 
 describe("applyCaptionOverrides", () => {
+  it("treats a missing optional sidecar as a silent no-op", async () => {
+    installGsapMock();
+    const json = vi.fn();
+    vi.stubGlobal("fetch", async () => ({ ok: false, status: 404, json }));
+    const error = vi.spyOn(console, "error").mockImplementation(() => {});
+    document.body.innerHTML = `<div class="caption-group"><span>Hi</span></div>`;
+
+    applyCaptionOverrides();
+    await flushCaptionOverrides();
+
+    expect(json).not.toHaveBeenCalled();
+    expect(error).not.toHaveBeenCalled();
+  });
+
+  it.each([
+    ["malformed JSON", () => Promise.reject(new SyntaxError("Unexpected token"))],
+    ["a non-array root", () => Promise.resolve({ wordIndex: 0 })],
+    ["a non-object entry", () => Promise.resolve([null])],
+  ])("reports a present sidecar containing %s", async (_shape, json) => {
+    installGsapMock();
+    vi.stubGlobal("fetch", async () => ({ ok: true, status: 200, json }));
+    const error = vi.spyOn(console, "error").mockImplementation(() => {});
+    document.body.innerHTML = `<div class="caption-group"><span>Hi</span></div>`;
+
+    applyCaptionOverrides();
+    await flushCaptionOverrides();
+
+    expect(error).toHaveBeenCalledOnce();
+    expect(error.mock.calls[0]?.[0]).toContain("caption-overrides.json");
+  });
+
+  it("accepts an empty array as the explicit no-op payload", async () => {
+    installGsapMock();
+    installCaptionOverrideFetch([]);
+    const error = vi.spyOn(console, "error").mockImplementation(() => {});
+    document.body.innerHTML = `<div class="caption-group"><span>Hi</span></div>`;
+
+    applyCaptionOverrides();
+    await flushCaptionOverrides();
+
+    expect(error).not.toHaveBeenCalled();
+  });
+
   it("reuses existing caption wrappers when overrides are applied more than once", async () => {
     const { setCalls } = installGsapMock();
     installCaptionOverrideFetch([{ wordIndex: 0, x: 12, y: -4, scale: 1.2 }]);
diff --git a/packages/core/src/runtime/captionOverrides.ts b/packages/core/src/runtime/captionOverrides.ts
index 1cd713b379..9b8c5113a1 100644
--- a/packages/core/src/runtime/captionOverrides.ts
+++ b/packages/core/src/runtime/captionOverrides.ts
@@ -27,6 +27,20 @@ interface CaptionOverride {
   fontFamily?: string;
 }
 
+function isCaptionOverride(value: unknown): value is CaptionOverride {
+  return typeof value === "object" && value !== null && !Array.isArray(value);
+}
+
+function parseCaptionOverridePayload(value: unknown): CaptionOverride[] {
+  if (!Array.isArray(value)) {
+    throw new Error("expected a JSON array");
+  }
+  if (!value.every(isCaptionOverride)) {
+    throw new Error("every array entry must be an object");
+  }
+  return value;
+}
+
 interface GsapTween {
   vars: Record<string, unknown>;
   startTime(): number;
@@ -109,13 +123,15 @@ export function applyCaptionOverrides(): void {
       if (!r.ok) return null;
       return r.json();
     })
-    .then((data: CaptionOverride[] | null) => {
-      if (!data || !Array.isArray(data) || data.length === 0) return;
+    .then((data: unknown) => {
+      if (data === null) return;
+      const overrides = parseCaptionOverridePayload(data);
+      if (overrides.length === 0) return;
 
       // Build word element index for wordIndex fallback
       const wordEls = getCaptionWordElements();
 
-      for (const override of data) {
+      for (const override of overrides) {
         let el: HTMLElement | null = null;
         if (override.wordId) {
           el = resolveCaptionWordElement(document.getElementById(override.wordId));
@@ -191,5 +207,8 @@ export function applyCaptionOverrides(): void {
         }
       }
     })
-    .catch(() => {});
+    .catch((error: unknown) => {
+      const message = error instanceof Error ? error.message : String(error);
+      console.error(`[HyperFrames] Invalid caption-overrides.json: ${message}`);
+    });
 }