diff --git a/.changeset/30210-business-unit-enterprise-requirement.md b/.changeset/30210-business-unit-enterprise-requirement.md
new file mode 100644
index 00000000000..111495f516b
--- /dev/null
+++ b/.changeset/30210-business-unit-enterprise-requirement.md
@@ -0,0 +1,13 @@
+---
+'@objectstack/platform-objects': patch
+'@objectstack/lint': patch
+---
+
+fix: the Business Unit page and the `security-private-no-readscope` hint say what needs the enterprise edition
+
+Clause-②: no
+Metadata-protocol: none
+
+- **Business Unit page (`sys_business_unit` description, en and zh-CN).** It used to say units are "used to scope data and reports". It now says what a unit does in the open edition: sharing rules can share records with a unit, or a unit and the units under it, and members get that access and lose it when they leave. It also says that letting a permission set read every record of a unit (read scope `unit`) needs the enterprise edition. That matches the compile refusal, which is unchanged.
+- **Business unit Timezone help (en and zh-CN).** It used to say date boundaries are computed in this zone. Nothing reads the column, so the help now says it changes no date calculation and that Settings → Localization → Default timezone is the one in effect, as the organization's Timezone help already does.
+- **`security-private-no-readscope` hint (`os validate`, `os lint`).** The hint now offers only the scopes the stack can compile. When `requires` lists `hierarchy-security`, nothing changes: it offers `own_and_reports`, `unit`, `unit_and_below` and `org`. Without it, the hint offers `org` (or widening the object's `sharingModel`), and says that the three hierarchy scopes need `requires: ['hierarchy-security']`, which `@objectstack/security-enterprise` provides. The rule still fires on the same grants at the same severity.
diff --git a/packages/lint/src/validate-security-posture.test.ts b/packages/lint/src/validate-security-posture.test.ts
index ea802e06090..ba7795dcc70 100644
--- a/packages/lint/src/validate-security-posture.test.ts
+++ b/packages/lint/src/validate-security-posture.test.ts
@@ -792,6 +792,42 @@ describe('validateSecurityPosture (ADR-0090 D7)', () => {
     expect(findings[0]).toMatchObject({ severity: 'info', rule: SECURITY_PRIVATE_NO_READSCOPE });
   });
 
+  // The hint offers only the scopes this stack can compile: `defineStack`
+  // refuses `own_and_reports` / `unit` / `unit_and_below` unless `requires`
+  // names `hierarchy-security`, so without that token the hint names the
+  // requirement in the same sentence as those scopes instead of offering them
+  // bare.
+  const noReadscopeHint = (requires?: string[]): string =>
+    validateSecurityPosture({
+      ...(requires ? { requires } : {}),
+      objects: [{ name: 'expense', sharingModel: 'private' }],
+      permissions: [{ name: 'finance_user', objects: { expense: { allowRead: true } } }],
+    }).find((f) => f.rule === SECURITY_PRIVATE_NO_READSCOPE)?.hint ?? '';
+
+  it('without hierarchy-security, offers org and names the requirement beside the hierarchy scopes', () => {
+    const hint = noReadscopeHint();
+    const requirementAt = hint.indexOf("requires: ['hierarchy-security']");
+    expect(requirementAt).toBeGreaterThan(-1);
+    expect(hint).toContain('@objectstack/security-enterprise');
+    const firstHierarchyScope = Math.min(
+      ...["'own_and_reports'", "'unit'", "'unit_and_below'"].map((s) => {
+        const at = hint.indexOf(s);
+        expect(at, `${s} is named`).toBeGreaterThan(-1);
+        return at;
+      }),
+    );
+    // What the hint offers before any hierarchy scope is `org` alone…
+    expect(hint.slice(0, firstHierarchyScope)).toContain("readScope: 'org'");
+    // …and no sentence ends between the first hierarchy scope and the requirement.
+    expect(hint.slice(firstHierarchyScope, requirementAt)).not.toMatch(/\.\s/);
+  });
+
+  it('with hierarchy-security declared, offers every scope and does not name the requirement', () => {
+    const hint = noReadscopeHint(['hierarchy-security']);
+    for (const scope of ["'own_and_reports'", "'unit'", "'unit_and_below'", "'org'"]) expect(hint).toContain(scope);
+    expect(hint).not.toContain('security-enterprise');
+  });
+
   it('stays silent when depth or VAMA is declared, or the object is public', () => {
     expect(
       rulesOf({
@@ -1762,7 +1798,9 @@ const READ_SURFACES: Array<{ receiver: string; expected: string[]; declaredBy: s
     // controlled-by-parent rules started judging an object on its MERGED
     // field set: the extensions a stack (or each package body of an artifact)
     // declares are folded onto the objects it declares.
-    expected: ['apps', 'books', 'capabilities', 'data', 'objectExtensions', 'objects', 'packages', 'permissions', 'positions'],
+    // [#30210] `requires` joined when the private-no-readscope hint started
+    // offering the hierarchy scopes only where `hierarchy-security` is declared.
+    expected: ['apps', 'books', 'capabilities', 'data', 'objectExtensions', 'objects', 'packages', 'permissions', 'positions', 'requires'],
     declaredBy: 'ObjectStackSchema',
     keys: () => Object.keys(ObjectStackSchema.shape),
   },
diff --git a/packages/lint/src/validate-security-posture.ts b/packages/lint/src/validate-security-posture.ts
index cdfe1d906f6..d87715223f0 100644
--- a/packages/lint/src/validate-security-posture.ts
+++ b/packages/lint/src/validate-security-posture.ts
@@ -1372,6 +1372,15 @@ export function validateSecurityPosture(stack: AnyRec, opts?: { nowMs?: number }
       })
       .map((o) => String(o.name ?? '')),
   );
+  // The hint offers only the scopes this stack can compile. `defineStack`
+  // refuses a hierarchy scope (`own_and_reports` / `unit` / `unit_and_below`,
+  // `findHierarchyScopeGrants`) unless `requires` names `hierarchy-security`
+  // (ADR-0057), the enterprise capability — so read the same declaration here
+  // and, without it, name the requirement beside those scopes instead of
+  // offering them bare. A stack with no `requires` (the runtime metadata
+  // door hands none) gets the requirement named too.
+  const hierarchyScopesCompile =
+    Array.isArray(stack.requires) && (stack.requires as unknown[]).includes('hierarchy-security');
   if (privateObjects.size > 0) {
     for (let i = 0; i < permissionSets.length; i++) {
       const ps = permissionSets[i];
@@ -1390,9 +1399,12 @@ export function validateSecurityPosture(stack: AnyRec, opts?: { nowMs?: number }
             message:
               `"${objName}" is private (OWD) and this set grants allowRead without a readScope — ` +
               `holders see ONLY records they own (plus explicit shares).`,
-            hint:
-              `If that is intended (personal data), ignore this. Otherwise add readScope: ` +
-              `'own_and_reports' | 'unit' | 'unit_and_below' | 'org', or widen the object's sharingModel.`,
+            hint: hierarchyScopesCompile
+              ? `If that is intended (personal data), ignore this. Otherwise add readScope: ` +
+                `'own_and_reports' | 'unit' | 'unit_and_below' | 'org', or widen the object's sharingModel.`
+              : `If that is intended (personal data), ignore this. Otherwise add readScope: 'org', ` +
+                `or widen the object's sharingModel. Scopes 'own_and_reports', 'unit' and 'unit_and_below' ` +
+                `need requires: ['hierarchy-security'], which @objectstack/security-enterprise provides.`,
           });
         }
       }
diff --git a/packages/platform-objects/src/apps/translations/en.objects.generated.ts b/packages/platform-objects/src/apps/translations/en.objects.generated.ts
index 423e402c972..c992546e6a3 100644
--- a/packages/platform-objects/src/apps/translations/en.objects.generated.ts
+++ b/packages/platform-objects/src/apps/translations/en.objects.generated.ts
@@ -984,7 +984,7 @@ export const enObjects: NonNullable<TranslationData['objects']> = {
   sys_business_unit: {
     label: "Business Unit",
     pluralLabel: "Business Units",
-    description: "Your company structure — divisions, departments, regions and offices — used to scope data and reports.",
+    description: "Your company structure — divisions, departments, regions and offices. Sharing rules can share records with a unit, or a unit and the units under it: members get that access, and lose it when they leave. Letting a permission set read every record of a unit (read scope 'unit') needs the enterprise edition.",
     fields: {
       name: {
         label: "Name"
@@ -1010,7 +1010,7 @@ export const enObjects: NonNullable<TranslationData['objects']> = {
       },
       timezone: {
         label: "Timezone",
-        help: "IANA time zone (e.g. Asia/Shanghai) date boundaries are computed in for this unit. Leave unset to inherit the parent unit's zone, then the organization's, then UTC."
+        help: "IANA time zone (e.g. Asia/Shanghai) kept for this unit; leave it empty to take the parent unit's, then the organization's. It does not change any date calculation today: formulas, reports and displayed dates use Settings → Localization → Default timezone."
       },
       organization_id: {
         label: "Organization",
diff --git a/packages/platform-objects/src/apps/translations/zh-CN.objects.generated.ts b/packages/platform-objects/src/apps/translations/zh-CN.objects.generated.ts
index 3ed89209302..473b2d5c84f 100644
--- a/packages/platform-objects/src/apps/translations/zh-CN.objects.generated.ts
+++ b/packages/platform-objects/src/apps/translations/zh-CN.objects.generated.ts
@@ -984,7 +984,7 @@ export const zhCNObjects: NonNullable<TranslationData['objects']> = {
   sys_business_unit: {
     label: "业务单元",
     pluralLabel: "业务单元",
-    description: "公司的组织结构——事业部、部门、区域和办公地点——用于划定数据和报表的范围。",
+    description: "公司的组织结构——事业部、部门、区域和办公地点。共享规则可以把记录共享给某个业务单元，或某个业务单元及其下级单元：成员获得这些访问权限，离开后即失去。让权限集按业务单元读取全部记录（读取范围「unit」）需要企业版。",
     fields: {
       name: {
         label: "名称"
@@ -1010,7 +1010,7 @@ export const zhCNObjects: NonNullable<TranslationData['objects']> = {
       },
       timezone: {
         label: "时区",
-        help: "该业务单元计算日期边界所用的 IANA 时区（如 Asia/Shanghai）。留空则依次继承上级业务单元的时区、组织的时区，最后为 UTC。"
+        help: "为该业务单元保存的 IANA 时区（如 Asia/Shanghai）；留空则取上级业务单元的，再取组织的。它目前不会改变任何日期计算：公式、报表和显示的日期使用 设置 → 本地化 → 默认时区。"
       },
       organization_id: {
         label: "组织",
diff --git a/packages/platform-objects/src/identity/sys-business-unit-edition-copy.test.ts b/packages/platform-objects/src/identity/sys-business-unit-edition-copy.test.ts
new file mode 100644
index 00000000000..fa109819a48
--- /dev/null
+++ b/packages/platform-objects/src/identity/sys-business-unit-edition-copy.test.ts
@@ -0,0 +1,51 @@
+// Copyright (c) 2026 ObjectStack. Licensed under the Apache-2.0 license.
+//
+// The Business Unit page says what a unit does in the open edition, and what
+// needs the enterprise edition (#30210 row 1). It used to say units are "used
+// to scope data and reports", while scoping a permission set's read access by
+// unit (`readScope: 'unit'` and the other hierarchy scopes) is refused at
+// compile without `requires: ['hierarchy-security']`, which only
+// `@objectstack/security-enterprise` provides. What does work in the open
+// edition is a sharing rule naming a unit (or a unit and the units under it),
+// whose access follows membership in and out.
+//
+// The unit's `timezone` help used to say date boundaries are computed in it.
+// Nothing reads the column (the same reading as `sys_organization.timezone`,
+// pinned in `sys-organization-name-timezone-help.test.ts`), so the help says
+// which setting is in effect instead.
+import { describe, expect, it } from 'vitest';
+import { SysBusinessUnit } from './sys-business-unit.object.js';
+import { zhCNObjects } from '../apps/translations/zh-CN.objects.generated.js';
+
+const zhUnit = () =>
+  (zhCNObjects as unknown as Record<string, { description?: string; fields?: Record<string, { help?: string }> }>)
+    .sys_business_unit;
+
+describe('sys_business_unit: the page says what the open edition gives and what needs enterprise (#30210)', () => {
+  it('names sharing rules as what a unit drives, and the enterprise requirement for unit-scoped read access', () => {
+    const d = SysBusinessUnit.description ?? '';
+    expect(d).toMatch(/[Ss]haring rules/);
+    expect(d).toMatch(/enterprise edition/);
+    expect(d).not.toMatch(/used to scope data and reports/);
+  });
+
+  it('the zh-CN page text says the same, not the old scoping claim', () => {
+    const d = zhUnit()?.description ?? '';
+    expect(d).toMatch(/共享规则/);
+    expect(d).toMatch(/企业版/);
+    expect(d).not.toMatch(/划定数据和报表的范围/);
+  });
+
+  it('the zh-CN timezone help no longer says date boundaries are computed in it', () => {
+    const help = zhUnit()?.fields?.timezone?.help ?? '';
+    expect(help).toMatch(/不会改变任何日期计算/);
+    expect(help).not.toMatch(/计算日期边界所用/);
+  });
+
+  it("the timezone help says it changes no date calculation and that Localization's Default timezone wins", () => {
+    const help = (SysBusinessUnit.fields as Record<string, { description?: string }>).timezone.description ?? '';
+    expect(help).toMatch(/does not change any date calculation/);
+    expect(help).toMatch(/Settings → Localization → Default timezone/);
+    expect(help).not.toMatch(/are computed in/);
+  });
+});
diff --git a/packages/platform-objects/src/identity/sys-business-unit.object.ts b/packages/platform-objects/src/identity/sys-business-unit.object.ts
index 236cbf7b3fb..eda640b8715 100644
--- a/packages/platform-objects/src/identity/sys-business-unit.object.ts
+++ b/packages/platform-objects/src/identity/sys-business-unit.object.ts
@@ -30,8 +30,17 @@ export const SysBusinessUnit = ObjectSchema.create({
   managedBy: 'platform',
   // Admin-facing copy: what the records are and what an admin does here. The
   // design reference (canonical org/data-partition tree, ADR-0057 D2) lives in
-  // the docblock above, never in this string.
-  description: 'Your company structure — divisions, departments, regions and offices — used to scope data and reports.',
+  // the docblock above, never in this string. It says what a unit does in
+  // the open edition (sharing rules naming a unit, whose access follows
+  // membership in and out) and that scoping a permission set's read access by
+  // unit (`readScope: 'unit'` and the other ADR-0057 hierarchy scopes) needs
+  // the enterprise edition: `defineStack` refuses those scopes without
+  // `requires: ['hierarchy-security']`, which only
+  // @objectstack/security-enterprise provides.
+  description:
+    'Your company structure — divisions, departments, regions and offices. Sharing rules can share records with a unit, ' +
+    'or a unit and the units under it: members get that access, and lose it when they leave. ' +
+    "Letting a permission set read every record of a unit (read scope 'unit') needs the enterprise edition.",
   displayNameField: 'name',
   nameField: 'name', // [ADR-0079] canonical primary-title pointer (mirrors deprecated displayNameField)
   highlightFields: ['name', 'kind', 'parent_business_unit_id', 'manager_user_id'],
@@ -189,13 +198,18 @@ export const SysBusinessUnit = ObjectSchema.create({
     // bound unconverged). No `defaultValue`, deliberately: an explicit
     // default here would mean "stop inheriting", which is the opposite of what
     // an unset unit means.
+    //
+    // [#30210] Because nothing reads the column, the help says so in the
+    // reader's terms and names the setting in effect — the same correction
+    // `sys_organization.timezone` took (#25347). The old help said date
+    // boundaries ARE computed in this zone, a claim no reader backed.
     timezone: Field.text({
       label: 'Timezone',
       required: false,
       maxLength: 64,
       valueDomain: 'iana_time_zone',
       description:
-        'IANA time zone (e.g. Asia/Shanghai) date boundaries are computed in for this unit. Leave unset to inherit the parent unit\'s zone, then the organization\'s, then UTC.',
+        'IANA time zone (e.g. Asia/Shanghai) kept for this unit; leave it empty to take the parent unit\'s, then the organization\'s. It does not change any date calculation today: formulas, reports and displayed dates use Settings → Localization → Default timezone.',
       group: 'Hierarchy',
     }),