diff --git a/CONTRIBUTING.md b/CONTRIBUTING.md
index 2bbb97a..9c20ae4 100644
--- a/CONTRIBUTING.md
+++ b/CONTRIBUTING.md
@@ -43,6 +43,11 @@ Then open the local URL printed by Next.js, usually
 <http://localhost:3000>. For a production-style preview, run
 `npm run build` followed by `npm run start`.
 
+`npm run build` fails if a doc-sync step in `prebuild` fails. When working
+offline, set `DOCS_SYNC_OPTIONAL=1` (for example
+`DOCS_SYNC_OPTIONAL=1 npm run build`) to keep the committed content instead.
+CI and Netlify always use the strict behavior.
+
 ## Code review requirements
 
 A PR merges once it passes the CI gates defined in `.github/workflows/` — Build,
diff --git a/changelog.d/fixed-prebuild-strict-sync.md b/changelog.d/fixed-prebuild-strict-sync.md
new file mode 100644
index 0000000..e068a97
--- /dev/null
+++ b/changelog.d/fixed-prebuild-strict-sync.md
@@ -0,0 +1 @@
+- Make `prebuild` fail the build when a content sync step fails instead of masking it with `|| echo`; set `DOCS_SYNC_OPTIONAL=1` to keep the offline fallback to committed content for local development.
diff --git a/package.json b/package.json
index 6dd5b66..c6555c4 100644
--- a/package.json
+++ b/package.json
@@ -7,7 +7,7 @@
   },
   "scripts": {
     "dev": "next dev --turbopack",
-    "prebuild": "(tsx scripts/update-meeting-recordings.ts || echo \"meeting recordings refresh unavailable - using committed data\") && (tsx scripts/sync-hive-docs.ts || echo \"hive docs sync unavailable - using committed content\") && (tsx scripts/sync-sibling-docs.ts || echo \"sibling docs sync unavailable - using committed content\") && tsx scripts/generate-shared-config.ts",
+    "prebuild": "tsx scripts/run-sync-step.ts scripts/update-meeting-recordings.ts && tsx scripts/run-sync-step.ts scripts/sync-hive-docs.ts && tsx scripts/run-sync-step.ts scripts/sync-sibling-docs.ts && tsx scripts/generate-shared-config.ts",
     "build": "next build",
     "start": "next start",
     "lint": "eslint src/ scripts/ netlify/",
diff --git a/scripts/run-sync-step.test.ts b/scripts/run-sync-step.test.ts
new file mode 100644
index 0000000..d321f57
--- /dev/null
+++ b/scripts/run-sync-step.test.ts
@@ -0,0 +1,30 @@
+import { describe, expect, it, vi } from "vitest";
+import type { spawnSync } from "node:child_process";
+import { isSyncOptional, runSyncStep } from "./run-sync-step";
+
+const fake = (status: number | null) =>
+  vi.fn(() => ({ status })) as unknown as typeof spawnSync;
+
+describe("run-sync-step", () => {
+  it("is strict unless DOCS_SYNC_OPTIONAL=1", () => {
+    expect(isSyncOptional({})).toBe(false);
+    expect(isSyncOptional({ DOCS_SYNC_OPTIONAL: "0" })).toBe(false);
+    expect(isSyncOptional({ DOCS_SYNC_OPTIONAL: "1" })).toBe(true);
+  });
+
+  it("passes through success", () => {
+    expect(runSyncStep("a.ts", {}, fake(0))).toBe(0);
+  });
+
+  it("propagates failure by default", () => {
+    expect(runSyncStep("a.ts", {}, fake(1))).toBe(1);
+    expect(runSyncStep("a.ts", {}, fake(null))).toBe(1);
+  });
+
+  it("tolerates failure when opted in", () => {
+    const warn = vi.spyOn(console, "warn").mockImplementation(() => {});
+    expect(runSyncStep("a.ts", { DOCS_SYNC_OPTIONAL: "1" }, fake(1))).toBe(0);
+    expect(warn).toHaveBeenCalled();
+    warn.mockRestore();
+  });
+});
diff --git a/scripts/run-sync-step.ts b/scripts/run-sync-step.ts
new file mode 100644
index 0000000..3cb40ba
--- /dev/null
+++ b/scripts/run-sync-step.ts
@@ -0,0 +1,43 @@
+/**
+ * Runs one prebuild sync step (a tsx script) and propagates its exit code.
+ * Failures fail the build unless DOCS_SYNC_OPTIONAL=1 is set, in which case the
+ * committed content is kept and a warning is printed (local/offline use only).
+ */
+import { spawnSync } from "node:child_process";
+
+// Plain record rather than NodeJS.ProcessEnv: Next.js augments ProcessEnv with
+// a required NODE_ENV, which makes object literals in tests unassignable.
+export type SyncEnv = Record<string, string | undefined>;
+
+export function isSyncOptional(env: SyncEnv = process.env): boolean {
+  return env.DOCS_SYNC_OPTIONAL === "1";
+}
+
+export function runSyncStep(
+  script: string,
+  env: SyncEnv = process.env,
+  run: typeof spawnSync = spawnSync
+): number {
+  const result = run("tsx", [script], {
+    stdio: "inherit",
+    env: env as NodeJS.ProcessEnv,
+    shell: process.platform === "win32",
+  });
+  const status = result.status ?? 1;
+  if (status !== 0 && isSyncOptional(env)) {
+    console.warn(
+      `${script} failed (exit ${status}); DOCS_SYNC_OPTIONAL=1 so using committed content`
+    );
+    return 0;
+  }
+  return status;
+}
+
+if (process.argv[1]?.endsWith("run-sync-step.ts")) {
+  const script = process.argv[2];
+  if (!script) {
+    console.error("usage: tsx scripts/run-sync-step.ts <script>");
+    process.exit(2);
+  }
+  process.exit(runSyncStep(script));
+}