diff --git a/src/components/SettingsModal.tsx b/src/components/SettingsModal.tsx
index 14d8e67..7f76a8f 100644
--- a/src/components/SettingsModal.tsx
+++ b/src/components/SettingsModal.tsx
@@ -34,6 +34,7 @@ import { useRouter } from 'next/navigation';
 import { showPrivacyModal } from '@/components/PrivacyModal';
 import { deleteDocuments, mimeTypeForDoc, uploadDocuments } from '@/lib/client/api/documents';
 import { postChangelogVersionCheck } from '@/lib/client/api/user-state';
+import { scheduleChangelogCheck } from '@/lib/client/changelog-check';
 import { cacheStoredDocumentFromBytes, clearDocumentCache } from '@/lib/client/cache/documents';
 import { clearAllDocumentPreviewCaches, clearInMemoryDocumentPreviewCache } from '@/lib/client/cache/previews';
 import { resolveTtsSettingsViewModel } from '@/lib/client/settings/tts-settings';
@@ -253,54 +254,21 @@ export function SettingsModal({ className = '' }: { className?: string }) {
   }, [authEnabled, checkFirstVist]);
 
   useEffect(() => {
-    let active = true;
-    let timer: ReturnType<typeof setTimeout> | null = null;
-    const run = async () => {
-      const sessionUserId = session?.user?.id ?? null;
-      if (authEnabled && (isSessionPending || !sessionUserId)) return;
-
-      const currentVersion = normalizeVersion(runtimeConfig.appVersion || '');
-      if (!currentVersion) return;
-
-      const userKey = sessionUserId ?? 'server-unclaimed';
-      const checkKey = `${userKey}:${currentVersion}`;
-      if (changelogVersionCheckKeyRef.current === checkKey) return;
-      if (changelogVersionCheckInFlightRef.current === checkKey) return;
-      changelogVersionCheckInFlightRef.current = checkKey;
-
-      try {
-        for (let attempt = 0; attempt < 2; attempt += 1) {
-          try {
-            const result = await postChangelogVersionCheck(currentVersion);
-            changelogVersionCheckKeyRef.current = checkKey;
-            if (result.shouldOpen && active) {
-              setIsOpen(true);
-              setIsChangelogOpen(true);
-            }
-            return;
-          } catch (error) {
-            if (attempt === 1) throw error;
-            await new Promise((resolve) => setTimeout(resolve, 400));
-          }
-        }
-      } catch (error) {
-        console.warn('Failed to check changelog version:', error);
-      } finally {
-        if (changelogVersionCheckInFlightRef.current === checkKey) {
-          changelogVersionCheckInFlightRef.current = null;
-        }
-      }
-    };
-
-    // In React Strict Mode (dev), effects mount/unmount once before the real mount.
-    // Deferring the network mutation avoids writing lastSeenVersion from the throwaway pass.
-    timer = setTimeout(() => {
-      void run();
-    }, 120);
-    return () => {
-      active = false;
-      if (timer) clearTimeout(timer);
-    };
+    return scheduleChangelogCheck({
+      authEnabled,
+      isSessionPending,
+      sessionUserId: session?.user?.id,
+      appVersion: runtimeConfig.appVersion,
+      completedRef: changelogVersionCheckKeyRef,
+      inFlightRef: changelogVersionCheckInFlightRef,
+      postCheck: async (currentVersion) => postChangelogVersionCheck(currentVersion),
+      onShouldOpen: () => {
+        setIsOpen(true);
+        setIsChangelogOpen(true);
+      },
+      delayMs: 120,
+      retryDelayMs: 400,
+    });
   }, [authEnabled, isSessionPending, session?.user?.id, runtimeConfig.appVersion]);
 
   useEffect(() => {
diff --git a/src/lib/client/changelog-check.ts b/src/lib/client/changelog-check.ts
new file mode 100644
index 0000000..70b1571
--- /dev/null
+++ b/src/lib/client/changelog-check.ts
@@ -0,0 +1,78 @@
+import { normalizeVersion } from '@/lib/shared/changelog';
+
+export type ChangelogVersionCheckResponse = {
+  shouldOpen: boolean;
+  currentVersion: string;
+  lastSeenVersion: string | null;
+};
+
+type RefLike = { current: string | null };
+
+export type RunChangelogCheckArgs = {
+  authEnabled: boolean;
+  isSessionPending: boolean;
+  sessionUserId: string | null | undefined;
+  appVersion: string | null | undefined;
+  completedRef: RefLike;
+  inFlightRef: RefLike;
+  postCheck: (currentVersion: string) => Promise<ChangelogVersionCheckResponse>;
+  onShouldOpen: () => void;
+  retryDelayMs?: number;
+  sleep?: (ms: number) => Promise<void>;
+};
+
+export async function runChangelogCheck(args: RunChangelogCheckArgs): Promise<void> {
+  const sessionUserId = args.sessionUserId ?? null;
+  if (args.authEnabled && (args.isSessionPending || !sessionUserId)) return;
+
+  const currentVersion = normalizeVersion(args.appVersion || '');
+  if (!currentVersion) return;
+
+  const userKey = sessionUserId ?? 'server-unclaimed';
+  const checkKey = `${userKey}:${currentVersion}`;
+  if (args.completedRef.current === checkKey) return;
+  if (args.inFlightRef.current === checkKey) return;
+  args.inFlightRef.current = checkKey;
+
+  const retryDelayMs = args.retryDelayMs ?? 400;
+  const sleep = args.sleep ?? ((ms: number) => new Promise<void>((resolve) => setTimeout(resolve, ms)));
+
+  try {
+    for (let attempt = 0; attempt < 2; attempt += 1) {
+      try {
+        const result = await args.postCheck(currentVersion);
+        args.completedRef.current = checkKey;
+        if (result.shouldOpen) {
+          args.onShouldOpen();
+        }
+        return;
+      } catch (error) {
+        if (attempt === 1) throw error;
+        await sleep(retryDelayMs);
+      }
+    }
+  } catch (error) {
+    console.warn('Failed to check changelog version:', error);
+  } finally {
+    if (args.inFlightRef.current === checkKey) {
+      args.inFlightRef.current = null;
+    }
+  }
+}
+
+export type ScheduleChangelogCheckArgs = RunChangelogCheckArgs & {
+  delayMs?: number;
+};
+
+export function scheduleChangelogCheck(args: ScheduleChangelogCheckArgs): () => void {
+  let active = true;
+  const timer = setTimeout(() => {
+    if (!active) return;
+    void runChangelogCheck(args);
+  }, args.delayMs ?? 120);
+
+  return () => {
+    active = false;
+    clearTimeout(timer);
+  };
+}
diff --git a/tests/unit/changelog-check.spec.ts b/tests/unit/changelog-check.spec.ts
new file mode 100644
index 0000000..f95bcbc
--- /dev/null
+++ b/tests/unit/changelog-check.spec.ts
@@ -0,0 +1,81 @@
+import { expect, test } from '@playwright/test';
+
+import { scheduleChangelogCheck } from '../../src/lib/client/changelog-check';
+
+function wait(ms: number): Promise<void> {
+  return new Promise((resolve) => setTimeout(resolve, ms));
+}
+
+test.describe('changelog check scheduling', () => {
+  test('cancels throwaway mount and runs exactly once on remount', async () => {
+    const completedRef = { current: null as string | null };
+    const inFlightRef = { current: null as string | null };
+    let apiCalls = 0;
+    let openCalls = 0;
+
+    const args = {
+      authEnabled: true,
+      isSessionPending: false,
+      sessionUserId: 'u1',
+      appVersion: '3.3.0',
+      completedRef,
+      inFlightRef,
+      postCheck: async () => {
+        apiCalls += 1;
+        return {
+          shouldOpen: true,
+          currentVersion: '3.3.0',
+          lastSeenVersion: null,
+        };
+      },
+      onShouldOpen: () => {
+        openCalls += 1;
+      },
+      delayMs: 40,
+      retryDelayMs: 1,
+    } as const;
+
+    const cleanupThrowaway = scheduleChangelogCheck(args);
+    cleanupThrowaway();
+
+    const cleanupReal = scheduleChangelogCheck(args);
+    await wait(120);
+    cleanupReal();
+
+    expect(apiCalls).toBe(1);
+    expect(openCalls).toBe(1);
+    expect(completedRef.current).toBe('u1:3.3.0');
+    expect(inFlightRef.current).toBeNull();
+  });
+
+  test('does not run when auth is enabled and session is pending', async () => {
+    const completedRef = { current: null as string | null };
+    const inFlightRef = { current: null as string | null };
+    let apiCalls = 0;
+
+    const cleanup = scheduleChangelogCheck({
+      authEnabled: true,
+      isSessionPending: true,
+      sessionUserId: null,
+      appVersion: '3.3.0',
+      completedRef,
+      inFlightRef,
+      postCheck: async () => {
+        apiCalls += 1;
+        return {
+          shouldOpen: true,
+          currentVersion: '3.3.0',
+          lastSeenVersion: null,
+        };
+      },
+      onShouldOpen: () => undefined,
+      delayMs: 20,
+    });
+
+    await wait(80);
+    cleanup();
+    expect(apiCalls).toBe(0);
+    expect(completedRef.current).toBeNull();
+    expect(inFlightRef.current).toBeNull();
+  });
+});