diff --git a/.changeset/sys-setting-scope-runtime-option-removed.md b/.changeset/sys-setting-scope-runtime-option-removed.md
new file mode 100644
index 0000000000..0bbd96fbe5
--- /dev/null
+++ b/.changeset/sys-setting-scope-runtime-option-removed.md
@@ -0,0 +1,30 @@
+---
+"@objectstack/platform-objects": patch
+---
+
+fix(platform-objects): `sys_setting.scope` drops the never-implemented `runtime` option (#6036)
+
+The `scope` select declared four cascade layers while the platform only ever had
+three. `SpecifierScopeSchema` (`packages/spec/src/system/settings-manifest.zod.ts`)
+is `z.enum(['global', 'tenant', 'user'])`, `SettingsService` never mentions the
+string `'runtime'` anywhere, and its `scopeRank()` switch handles only those same
+three — so no code path could write such a row and none could read one back. The
+sibling audit object `sys_setting_audit.scope` already declared only three. This
+was a declared-but-unenforced value domain of the ADR-0049 kind: nobody could hit
+it, but the next reader of the object definition would reasonably conclude the
+platform supports a fourth scope layer.
+
+Removed rather than implemented — there is no runtime-scope product intent, and
+the spec enum stays the reference truth for what the cascade's layers are. A new
+pin (`sys-setting.scope-options.test.ts`) compares the object's option list
+against `SpecifierScopeSchema` directly, so a future divergence in either
+direction lands as a red test instead of a second silent one.
+
+Removal was gated on a measurement, not on the zero-write-path prediction: a real
+engine booted over the platform objects, driven through the real
+`/api/settings/:namespace` write path, stored 4 rows (`tenant` 3, `global` 1) and
+**0** with `scope='runtime'` — with a positive control proving the query does
+surface such a row when one is injected directly.
+
+No stored data is affected and no consumer read the option, so this is a
+definition-only correction.
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 391ee0d64b..1378347f03 100644
--- a/packages/platform-objects/src/apps/translations/en.objects.generated.ts
+++ b/packages/platform-objects/src/apps/translations/en.objects.generated.ts
@@ -2931,8 +2931,7 @@ export const enObjects: NonNullable<TranslationData['objects']> = {
         options: {
           global: "Global",
           tenant: "Tenant",
-          user: "User",
-          runtime: "Runtime"
+          user: "User"
         }
       },
       user_id: {
diff --git a/packages/platform-objects/src/apps/translations/es-ES.objects.generated.ts b/packages/platform-objects/src/apps/translations/es-ES.objects.generated.ts
index 30b2408e11..1bc959fd12 100644
--- a/packages/platform-objects/src/apps/translations/es-ES.objects.generated.ts
+++ b/packages/platform-objects/src/apps/translations/es-ES.objects.generated.ts
@@ -2931,8 +2931,7 @@ export const esESObjects: NonNullable<TranslationData['objects']> = {
         options: {
           global: "Global",
           tenant: "Inquilino",
-          user: "Usuario",
-          runtime: "Tiempo de ejecución"
+          user: "Usuario"
         }
       },
       user_id: {
diff --git a/packages/platform-objects/src/apps/translations/ja-JP.objects.generated.ts b/packages/platform-objects/src/apps/translations/ja-JP.objects.generated.ts
index b3b0285a64..92a404dcf5 100644
--- a/packages/platform-objects/src/apps/translations/ja-JP.objects.generated.ts
+++ b/packages/platform-objects/src/apps/translations/ja-JP.objects.generated.ts
@@ -2931,8 +2931,7 @@ export const jaJPObjects: NonNullable<TranslationData['objects']> = {
         options: {
           global: "グローバル",
           tenant: "テナント",
-          user: "ユーザー",
-          runtime: "ランタイム"
+          user: "ユーザー"
         }
       },
       user_id: {
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 3f403ddb75..543ba17def 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
@@ -2931,8 +2931,7 @@ export const zhCNObjects: NonNullable<TranslationData['objects']> = {
         options: {
           global: "全局",
           tenant: "租户",
-          user: "用户",
-          runtime: "运行时"
+          user: "用户"
         }
       },
       user_id: {
diff --git a/packages/platform-objects/src/system/sys-setting.object.ts b/packages/platform-objects/src/system/sys-setting.object.ts
index 29fe512255..ed799ff6a3 100644
--- a/packages/platform-objects/src/system/sys-setting.object.ts
+++ b/packages/platform-objects/src/system/sys-setting.object.ts
@@ -119,12 +119,20 @@ export const SysSetting = ObjectSchema.create({
       description: 'Specifier key inside the namespace (snake_case).',
     }),
 
+    // The option list is the storage-side mirror of `SpecifierScopeSchema`
+    // (`packages/spec/src/system/settings-manifest.zod.ts`), which is the
+    // reference truth for the cascade's layers. Keep the two in step —
+    // `sys-setting.scope-options.test.ts` pins the parity, and the sibling
+    // audit object (`sys_setting_audit.scope`) mirrors the same three.
+    // A fourth option lived here declaring `runtime` (#6036): the spec enum
+    // never accepted it, `SettingsService` never mentioned it, and no write
+    // path could produce such a row — a declared-but-unenforced value domain
+    // of exactly the ADR-0049 kind. Removed rather than implemented.
     scope: Field.select(
       [
         { label: 'Global', value: 'global' },
         { label: 'Tenant', value: 'tenant' },
         { label: 'User',   value: 'user' },
-        { label: 'Runtime',value: 'runtime' },
       ],
       {
         label: 'Scope',
diff --git a/packages/platform-objects/src/system/sys-setting.scope-options.test.ts b/packages/platform-objects/src/system/sys-setting.scope-options.test.ts
new file mode 100644
index 0000000000..ec510db9ab
--- /dev/null
+++ b/packages/platform-objects/src/system/sys-setting.scope-options.test.ts
@@ -0,0 +1,59 @@
+// Copyright (c) 2026 ObjectStack. Licensed under the Apache-2.0 license.
+//
+// #6036 — `sys_setting.scope` once declared a fourth option, `runtime`, that
+// nothing in the platform could produce or consume: `SpecifierScopeSchema` is
+// three-valued, `SettingsService` never mentions the string, and every write
+// reaches the table through `set()`/`setMany()`, whose scope comes from the
+// manifest registry (`reg.scopes`) — i.e. from that same three-value enum.
+// A declared-but-unenforced value domain of exactly the ADR-0049 kind.
+//
+// These pins make the divergence loud instead of dormant. The load-bearing one
+// is the PARITY assertion: the storage column's option list and the spec enum
+// are two spellings of one truth, so they are compared to each other rather
+// than to a hand-copied literal that would need editing on both sides anyway.
+// A future fourth cascade layer therefore lands here as a red test, not as a
+// silent re-divergence.
+import { describe, expect, it } from 'vitest';
+import { SpecifierScopeSchema } from '@objectstack/spec/system';
+import { SysSetting } from './sys-setting.object.js';
+import { SysSettingAudit } from './sys-setting-audit.object.js';
+
+/** Declared option values of a select field, in declaration order. */
+function optionValues(object: unknown, field: string): string[] {
+  const f = (object as any).fields?.[field];
+  expect(f, `${field} field exists`).toBeDefined();
+  expect(f.type).toBe('select');
+  return ((f.options ?? []) as Array<{ value: unknown }>).map((o) => String(o.value));
+}
+
+describe('sys_setting.scope — value domain (#6036)', () => {
+  it('declares exactly the cascade layers the resolver walks', () => {
+    expect(optionValues(SysSetting, 'scope')).toEqual(['global', 'tenant', 'user']);
+  });
+
+  it('does not declare a `runtime` layer', () => {
+    // Spelled as its own case because THIS is the regression: the option was
+    // inert, so re-adding it breaks nothing at runtime and would otherwise
+    // sail through review a second time.
+    expect(optionValues(SysSetting, 'scope')).not.toContain('runtime');
+  });
+
+  it('matches SpecifierScopeSchema — the reference truth for the cascade', () => {
+    // Set-compare: the spec enum is the authority on which layers exist, the
+    // object definition is the storage mirror. Either side growing alone is
+    // the #6036 defect, in whichever direction it happens next.
+    expect([...optionValues(SysSetting, 'scope')].sort()).toEqual(
+      [...SpecifierScopeSchema.options].sort(),
+    );
+  });
+
+  it('agrees with the audit trail object, which records the same layers', () => {
+    expect(optionValues(SysSettingAudit, 'scope')).toEqual(optionValues(SysSetting, 'scope'));
+  });
+
+  it('keeps `tenant` as the default, and the default is a declared option', () => {
+    const f = (SysSetting as any).fields.scope;
+    expect(f.defaultValue).toBe('tenant');
+    expect(optionValues(SysSetting, 'scope')).toContain(f.defaultValue);
+  });
+});