diff --git a/.changeset/fix-org-id-optional-single-tenant.md b/.changeset/fix-org-id-optional-single-tenant.md
new file mode 100644
index 0000000000..661e172565
--- /dev/null
+++ b/.changeset/fix-org-id-optional-single-tenant.md
@@ -0,0 +1,13 @@
+---
+"@objectstack/platform-objects": patch
+---
+
+Fix: `sys_business_unit` / `sys_team` could not be created in single-tenant deployments.
+
+`organization_id` was `required`, but single-tenant has no `sys_organization` row and
+nothing auto-stamps one (OrgScopingPlugin is multi-tenant-only), so every create failed
+with `VALIDATION_FAILED: organization_id (required)`. Make `organization_id` optional on
+both objects: single-tenant leaves it null; multi-tenant still auto-stamps it via
+OrgScopingPlugin and tenant-isolation RLS hides any null-org row (fail-closed), so there is
+no cross-tenant exposure. (sys_member / sys_invitation carry the same `required` flag but are
+created only through better-auth org flows, which always supply an org — left unchanged.)
diff --git a/packages/dogfood/test/single-tenant-identity-create.dogfood.test.ts b/packages/dogfood/test/single-tenant-identity-create.dogfood.test.ts
new file mode 100644
index 0000000000..f62cb35eba
--- /dev/null
+++ b/packages/dogfood/test/single-tenant-identity-create.dogfood.test.ts
@@ -0,0 +1,38 @@
+// Copyright (c) 2025 ObjectStack. Licensed under the Apache-2.0 license.
+
+/**
+ * ADR-0057 — org-scoped identity objects must be creatable in SINGLE-TENANT.
+ *
+ * Single-tenant deployments have no `sys_organization` row and no auto-stamp
+ * (OrgScopingPlugin is multi-tenant-only), so a `required` `organization_id`
+ * made sys_business_unit / sys_team uncreatable (VALIDATION_FAILED). The field
+ * is now optional; this proves the create path works with no org.
+ */
+
+import { describe, it, expect, beforeAll, afterAll } from 'vitest';
+import showcaseStack from '@objectstack/example-showcase';
+import { bootStack, type VerifyStack } from '@objectstack/verify';
+
+describe('ADR-0057: org-scoped identity creatable single-tenant', () => {
+  let stack: VerifyStack;
+  let token: string;
+
+  beforeAll(async () => {
+    stack = await bootStack(showcaseStack, {}); // single-tenant: no org-scoping, no org row
+    token = await stack.signIn();
+  }, 120_000);
+
+  afterAll(async () => { await stack?.stop?.(); });
+
+  it('creates a sys_business_unit with no organization_id', async () => {
+    const res = await stack.apiAs(token, 'POST', '/data/sys_business_unit', { name: 'Engineering', kind: 'department' });
+    expect(res.status).toBe(201);
+    const body: any = await res.json();
+    expect(body.record?.organization_id ?? null).toBeNull();
+  });
+
+  it('creates a sys_team with no organization_id', async () => {
+    const res = await stack.apiAs(token, 'POST', '/data/sys_team', { name: 'Tiger Team' });
+    expect(res.status).toBe(201);
+  });
+});
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 6a9bc26244..68b5be7ede 100644
--- a/packages/platform-objects/src/identity/sys-business-unit.object.ts
+++ b/packages/platform-objects/src/identity/sys-business-unit.object.ts
@@ -114,8 +114,13 @@ export const SysBusinessUnit = ObjectSchema.create({
 
     organization_id: Field.lookup('sys_organization', {
       label: 'Organization',
-      required: true,
-      description: 'Tenant scope.',
+      // Optional: single-tenant deployments have no organization row (org-scoping
+      // is multi-tenant-only, nothing auto-stamps one) — requiring it would make
+      // the object uncreatable single-tenant. In multi-tenant, OrgScopingPlugin
+      // auto-stamps this from the active tenant and tenant-isolation RLS hides any
+      // null-org row (fail-closed). ADR-0057 addendum.
+      required: false,
+      description: 'Tenant scope. Null in single-tenant; auto-stamped in multi-tenant.',
       group: 'Hierarchy',
     }),
 
diff --git a/packages/platform-objects/src/identity/sys-team.object.ts b/packages/platform-objects/src/identity/sys-team.object.ts
index 0e9a873359..25dfb8c50e 100644
--- a/packages/platform-objects/src/identity/sys-team.object.ts
+++ b/packages/platform-objects/src/identity/sys-team.object.ts
@@ -122,8 +122,13 @@ export const SysTeam = ObjectSchema.create({
 
     organization_id: Field.lookup('sys_organization', {
       label: 'Organization',
-      required: true,
-      description: 'Parent organization for this team',
+      // Optional: single-tenant deployments have no organization row (org-scoping
+      // is multi-tenant-only, nothing auto-stamps one) — requiring it would make
+      // the object uncreatable single-tenant. In multi-tenant, OrgScopingPlugin
+      // auto-stamps this from the active tenant and tenant-isolation RLS hides any
+      // null-org row (fail-closed). ADR-0057 addendum.
+      required: false,
+      description: 'Parent organization for this team. Null in single-tenant; auto-stamped in multi-tenant.',
       group: 'Identity',
     }),