diff --git a/server/src/systemNotices/registry.ts b/server/src/systemNotices/registry.ts
index 56938c6b0..3dca1513f 100644
--- a/server/src/systemNotices/registry.ts
+++ b/server/src/systemNotices/registry.ts
@@ -106,7 +106,11 @@ export const SYSTEM_NOTICES: SystemNotice[] = [
     conditions: [{ kind: 'managed', is: false }],
     publishedAt: '2026-08-22T00:00:00Z',
     priority: 110,
+    // The 4.0.x window. The copy is about this release, so somebody arriving on
+    // 4.1 — or jumping 3.x straight to 4.2 — should get that release's notice
+    // instead of this one, not a summary of a version they skipped.
     minVersion: '4.0.0',
+    maxVersion: '4.1.0',
   },
 
   // ── Thank-you + support the project — shown once per install AND once per upgrade ──
diff --git a/server/tests/unit/systemNotices/registry.test.ts b/server/tests/unit/systemNotices/registry.test.ts
index ab72bceb5..1c4c2ce41 100644
--- a/server/tests/unit/systemNotices/registry.test.ts
+++ b/server/tests/unit/systemNotices/registry.test.ts
@@ -3,6 +3,7 @@ import fs from 'node:fs';
 import path from 'node:path';
 import semver from 'semver';
 import { SYSTEM_NOTICES } from '../../../src/systemNotices/registry.js';
+import { isNoticeVersionActive } from '../../../src/systemNotices/service.js';
 
 /** Collect all actionIds registered via registerNoticeAction() in client source files. */
 function collectRegisteredActionIds(): Set<string> {
@@ -63,4 +64,34 @@ describe('registry integrity', () => {
       }
     }
   });
+
+  it('the 4.0.0 release notice is confined to the 4.0.x line', () => {
+    const release = SYSTEM_NOTICES.find(n => n.id === 'release-4-0-0');
+    expect(release).toBeDefined();
+    // Its copy is about this release, so it must not greet somebody who skipped
+    // straight past it, and it must not run alongside the next release's notice.
+    expect(isNoticeVersionActive(release!, '3.4.1')).toBe(false);
+    expect(isNoticeVersionActive(release!, '4.0.0')).toBe(true);
+    expect(isNoticeVersionActive(release!, '4.0.7')).toBe(true);
+    // The upper bound is exclusive, so every 4.0.x patch still gets it.
+    expect(isNoticeVersionActive(release!, '4.0.9')).toBe(true);
+    expect(isNoticeVersionActive(release!, '4.0.12')).toBe(true);
+    expect(isNoticeVersionActive(release!, '4.1.0')).toBe(false);
+    expect(isNoticeVersionActive(release!, '4.2.0')).toBe(false);
+  });
+
+  it('the thank-you notice hands over to the release modal at 4.0.0', () => {
+    const thankYou = SYSTEM_NOTICES.find(n => n.id === 'thank-you-support');
+    expect(thankYou).toBeDefined();
+    // Both carry the same thank-you and the same two support links, so exactly
+    // one of them may be active at any version.
+    expect(isNoticeVersionActive(thankYou!, '3.4.1')).toBe(true);
+    expect(isNoticeVersionActive(thankYou!, '4.0.0')).toBe(false);
+
+    const release = SYSTEM_NOTICES.find(n => n.id === 'release-4-0-0')!;
+    for (const version of ['3.4.1', '4.0.0', '4.0.7', '4.1.0', '5.0.0']) {
+      const active = [thankYou!, release].filter(n => isNoticeVersionActive(n, version));
+      expect(active.length, `both thank-you notices active at ${version}`).toBeLessThanOrEqual(1);
+    }
+  });
 });