diff --git a/packages/review/src/sharing/client.test.ts b/packages/review/src/sharing/client.test.ts
index 1b1c182e9..8a8db9f67 100644
--- a/packages/review/src/sharing/client.test.ts
+++ b/packages/review/src/sharing/client.test.ts
@@ -1,7 +1,7 @@
 import { randomUUID } from "node:crypto";
 import { mkdtemp, rm } from "node:fs/promises";
 
-import { afterEach, expect, it } from "vitest";
+import { afterEach, expect, it, vi } from "vitest";
 
 import { createShareFixture } from "../../test/fixtures/share/create.js";
 import {
@@ -255,6 +255,25 @@ it.each([409, 503])(
   },
 );
 
+it("rejects an invalid bundle before contacting the share service", async () => {
+  const root = await mkdtemp("/tmp/share-client-");
+  cleanup.push(() => rm(root, { recursive: true, force: true }));
+  const fixture = await createShareFixture(root);
+  cleanup.push(async () => {
+    await fixture.data.close();
+    fixture.store.close();
+  });
+
+  const bundle = await exportShare(fixture);
+  bundle.objects.clear();
+  const network = vi.fn<typeof fetch>();
+
+  await expect(
+    new ShareClient("https://app.dev.fast", undefined, network).create(bundle),
+  ).rejects.toBeInstanceOf(SharePreflightError);
+  expect(network).not.toHaveBeenCalled();
+});
+
 it("bounds concurrent downloads and still rejects corrupt objects", async () => {
   const root = await mkdtemp("/tmp/share-download-");
   cleanup.push(() => rm(root, { recursive: true, force: true }));
diff --git a/packages/review/src/sharing/client.ts b/packages/review/src/sharing/client.ts
index 3a7145710..20545b4bb 100644
--- a/packages/review/src/sharing/client.ts
+++ b/packages/review/src/sharing/client.ts
@@ -183,7 +183,17 @@ export class ShareClient {
     requestId: string = randomUUID(),
     beforeUpload?: () => Promise<void>,
   ) {
-    validateShareBundle(bundle);
+    try {
+      validateShareBundle(bundle);
+    } catch (cause) {
+      throw new SharePreflightError(
+        new Error(
+          "Whiteboard could not prepare this review for sharing. Please report this issue.",
+          { cause },
+        ),
+      );
+    }
+
     const manifestBytes = Buffer.from(JSON.stringify(bundle.manifest));
 
     const created = createdSchema.parse(