@@ -0,0 +1,15 @@
+---
+'@objectstack/core': patch
+'@objectstack/objectql': patch
+'@objectstack/plugin-security': patch
+'@objectstack/plugin-hono-server': patch
+---
+
+fix(core,objectql): effective object permissions read the external write gate, so a read-only external object is no longer offered New, Import, Edit or Delete
+
+Clause-②: yes (widening)
+Metadata-protocol: none
+
+- **Behaviour.** On an object whose external write gate is closed (ADR-0015 §5.3 Gate 3: a federated datasource, and not both `datasource.external.allowWrites` and `object.external.writable`), every insert, update and delete is refused `403 EXTERNAL_WRITE_FORBIDDEN` for every caller. The effective object-permission map now says so: the entry grants no `allowCreate`, `allowEdit`, `allowDelete` or `allowTransfer`, a `modifyAllRecords` on it is lowered to the `viewAllRecords` read it implies, and `apiOperations` carries no write operation (`create`, `update`, `delete`, `upsert`, `bulk`, `import`, `restore`, `purge`). Read and export are unchanged. Both consumers move together: `/auth/me/permissions` (the console hides those doors with no client change) and `ISecurityService.getEffectiveObjectPermissions`, so `current_user.can(object, 'create' | 'edit' | 'delete' | 'transfer')` now answers `false` on such an object, as the write itself always did.
+- **`@objectstack/objectql`: `ObjectQL.isExternalWriteForbidden(objectName)`**, the gate's verdict as a read-only question. The write gate (`assertWriteAllowed`) reads the same verdict, so the two cannot disagree.
+- **`@objectstack/core`: `engineExternalWriteForbidden(engine)`** (the accessor over an engine, asked when the member is present) and the optional `isExternalWriteForbidden` accessor on `EffectiveObjectPermissionsSchemaSource`; `annotateEffectiveApiOperations` takes the same predicate as an optional third argument. A caller that hands over neither gets the map it got before.
@@ -18,6 +18,7 @@ import { objectPermissionGrants } from '@objectstack/spec/security';
 import {
   buildEffectiveFieldPermissions,
   buildEffectiveObjectPermissions,
+  engineExternalWriteForbidden,
   fieldPermissionVote,
   holdsSuperuserBypass,
   registryObjectPackageDisabled,
@@ -474,6 +475,86 @@ describe('[#20135] apiOperations says what the REST door serves', () => {
   });
 });
 
+describe('[#30370] an object whose external write gate is closed grants no write', () => {
+  const SCHEMAS: Record<string, any> = {
+    customer: { name: 'customer', datasource: 'showcase_external' },
+    order: { name: 'order', datasource: 'showcase_external', enable: { apiMethods: ['get', 'list', 'create', 'update'] } },
+    lead: { name: 'lead' },
+  };
+  const source = (forbidden: (name: string) => boolean = (name) => name === 'customer' || name === 'order') => ({
+    allSchemas: () => Object.values(SCHEMAS),
+    schemaOf: (name: string) => SCHEMAS[name],
+    isExternalWriteForbidden: forbidden,
+  });
+  const WRITE_OPERATIONS = ['create', 'update', 'delete', 'upsert', 'bulk', 'import', 'restore', 'purge'];
+  const VERBS = ['allowCreate', 'allowEdit', 'allowDelete', 'allowTransfer'] as const;
+
+  it('an explicit grant, a plain wildcard and a super-user wildcard all lose every write verb, and keep read and export', () => {
+    for (const sets of [
+      [{ objects: { customer: { allowRead: true, allowCreate: true, allowEdit: true, allowDelete: true, allowTransfer: true, allowExport: true }, lead: { allowRead: true, allowCreate: true } } }],
+      [{ objects: { '*': { allowRead: true, allowCreate: true, allowEdit: true, allowDelete: true, allowExport: true } } }],
+      [{ objects: { '*': { allowRead: true, allowExport: true, viewAllRecords: true, modifyAllRecords: true } } }],
+    ]) {
+      const map: any = buildEffectiveObjectPermissions(sets, source());
+      const label = JSON.stringify(sets);
+      for (const verb of VERBS) expect(objectPermissionGrants(map.customer, verb), `${label} ${verb}`).toBe(false);
+      expect(objectPermissionGrants(map.customer, 'allowRead'), label).toBe(true);
+      expect(objectPermissionGrants(map.customer, 'allowExport'), label).toBe(true);
+      // The read operations stay served, export included; no write operation is.
+      expect(map.customer.apiOperations, label).toEqual(['get', 'list', 'aggregate', 'search', 'export']);
+      // An object on a managed datasource keeps exactly what it was granted.
+      const { isExternalWriteForbidden: _drop, ...without } = source();
+      expect(map.lead, label).toEqual((buildEffectiveObjectPermissions(sets, without) as any).lead);
+      expect(objectPermissionGrants(map.lead, 'allowCreate') || objectPermissionGrants(map.lead, 'allowEdit'), label).toBe(true);
+    }
+  });
+
+  it('modifyAllRecords on the object is lowered to the read it implies, so can() answers no write and the same read', () => {
+    const map: any = buildEffectiveObjectPermissions(
+      [{ objects: { customer: { modifyAllRecords: true } } }],
+      source(),
+    );
+    expect(map.customer.modifyAllRecords).toBe(false);
+    expect(map.customer.viewAllRecords).toBe(true);
+    expect(objectPermissionGrants(map.customer, 'allowRead')).toBe(true);
+    for (const verb of VERBS) expect(objectPermissionGrants(map.customer, verb), verb).toBe(false);
+  });
+
+  it('an object that already narrows its operations is served its narrowed reads only', () => {
+    const map: any = buildEffectiveObjectPermissions([{ objects: { order: { allowRead: true, allowCreate: true } } }], source());
+    expect(map.order.apiOperations).toEqual(['get', 'list', 'aggregate', 'search']);
+    for (const op of WRITE_OPERATIONS) expect(map.order.apiOperations).not.toContain(op);
+  });
+
+  it('an open gate, or no accessor, leaves the map exactly as before', () => {
+    const sets = [{ objects: { '*': { allowRead: true, allowCreate: true, allowEdit: true, allowDelete: true, allowExport: true } } }];
+    const { isExternalWriteForbidden: _drop, ...without } = source();
+    const before = JSON.stringify(buildEffectiveObjectPermissions(sets, without));
+    expect(JSON.stringify(buildEffectiveObjectPermissions(sets, source(() => false)))).toBe(before);
+    expect((JSON.parse(before) as any).customer).toMatchObject({ allowCreate: true, allowEdit: true, allowDelete: true });
+  });
+
+  it('a predicate that throws is reported and clamps nothing — never half the map', () => {
+    const sets = [{ objects: { customer: { allowRead: true, allowEdit: true }, order: { allowRead: true, allowEdit: true } } }];
+    const warnings: string[] = [];
+    const map: any = buildEffectiveObjectPermissions(sets, {
+      ...source((name) => { if (name === 'order') throw new Error('registry offline'); return true; }),
+      logger: { warn: (message) => warnings.push(message) },
+    });
+    expect(map.customer.allowEdit).toBe(true);
+    expect(map.order.allowEdit).toBe(true);
+    expect(warnings).toEqual(['[effective-permissions] external write gate read failed']);
+  });
+
+  it('engineExternalWriteForbidden asks the engine\'s own verdict, and an engine without it forbids nothing', () => {
+    const engine = { isExternalWriteForbidden(name: string) { return this === engine && name === 'customer'; } };
+    expect(engineExternalWriteForbidden(engine)('customer')).toBe(true);
+    expect(engineExternalWriteForbidden(engine)('lead')).toBe(false);
+    expect(engineExternalWriteForbidden({})('customer')).toBe(false);
+    expect(engineExternalWriteForbidden(undefined)('customer')).toBe(false);
+  });
+});
+
 // ── [#25866 / ruling of record 6408558941] A field permission entry's row
 // condition (`when`): the ONE vote per verdict, and the row-blind merge behind
 // `/auth/me/permissions`' `fields` slot.
 
@@ -36,6 +36,7 @@ import {
   resolveEffectiveApiMethods,
   effectiveOperationsArray,
   canServeApiOperation,
+  type ApiOperation,
   type EnableLike,
 } from '@objectstack/spec/data';
 import { objectPermissionGrants, type EffectiveObjectPermission } from '@objectstack/spec/security';
@@ -478,10 +479,18 @@ export function seedSuperUserRestrictedObjects(
  * Which entries carry the annotation is unchanged in rule: only an
  * unrestricted object that keeps its whole closure — every operation served,
  * `export` included — gets none.
+ *
+ * [#30370] With `isExternalWriteForbidden`, an object whose external write
+ * gate is closed (ADR-0015 §5.3 Gate 3) is served without every write
+ * operation ({@link EXTERNAL_WRITE_GATED_OPERATIONS}): the data plane refuses
+ * each one `403 EXTERNAL_WRITE_FORBIDDEN` whatever the permission sets say,
+ * and such an object is always annotated, since the client's default-allow
+ * path would offer every write. Without it, the answer is what it was.
  */
 export function annotateEffectiveApiOperations(
   objects: Record<string, any>,
   schemaOf: (objectName: string) => ApiExposureSchemaLike | undefined,
+  isExternalWriteForbidden?: (objectName: string) => boolean,
 ): void {
   for (const [obj, acc] of Object.entries(objects) as Array<[string, any]>) {
     if (obj === '*' || !acc) continue;
@@ -497,18 +506,86 @@ export function annotateEffectiveApiOperations(
     const closure = effectiveOperationsArray(eff);
     // [#20135] Only what the door itself admits: `apiEnabled: false` empties
     // the set; any other `enable` leaves the closure as it is.
-    const served = closure.filter((operation) => canServeApiOperation(enable, operation));
+    // [#30370] And only what the external write gate admits: a closed gate
+    // refuses every write operation on the data plane.
+    const writeForbidden = isExternalWriteForbidden?.(obj) === true;
+    const served = closure.filter((operation) =>
+      canServeApiOperation(enable, operation)
+      && !(writeForbidden && EXTERNAL_WRITE_GATED_OPERATIONS.has(operation)));
     // Annotate when the object tightens via `apiMethods`, when the export
     // axis removes `export` from an otherwise-open object (so the client
     // hides the Export button), OR when the door serves less than the closure
-    // (an API-disabled object). An unrestricted object with every operation
-    // still served needs no annotation — the client keeps its default-allow
-    // path.
+    // (an API-disabled object, or [#30370] a closed external write gate). An
+    // unrestricted object with every operation still served needs no
+    // annotation — the client keeps its default-allow path.
     if (eff.mode === 'unrestricted' && userExportAllowed && served.length === closure.length) continue;
     acc.apiOperations = served;
   }
 }
 
+/**
+ * [#30370] The effective API operations that WRITE a row — every one the
+ * external write gate (ADR-0015 §5.3 Gate 3, objectql `assertWriteAllowed`)
+ * refuses on an object whose gate is closed: the three primitives it judges
+ * (`insert` is `create`), and every derived operation built on them —
+ * `upsert` (create ∧ update), `bulk` (batched create / update / delete),
+ * `import` (create ∨ update), and `restore` / `purge`, which never derive
+ * today but write when they do. The read operations (`get`, `list`,
+ * `aggregate`, `history`, `search`, `export`) are untouched: the gate judges
+ * writes only.
+ */
+const EXTERNAL_WRITE_GATED_OPERATIONS: ReadonlySet<ApiOperation> = new Set<ApiOperation>([
+  'create', 'update', 'delete', 'upsert', 'bulk', 'import', 'restore', 'purge',
+]);
+
+/**
+ * [#30370] Re-clamp the map by the THIRD server-side enforcement layer
+ * permission sets do not model: the external write gate (ADR-0015 §5.3
+ * Gate 3). On an object whose gate is closed, objectql refuses every insert,
+ * update and delete `403 EXTERNAL_WRITE_FORBIDDEN` for every caller — no
+ * permission set, super-user bypass included, opens it — so the entry grants
+ * no write: `allowCreate`, `allowEdit`, `allowDelete` and `allowTransfer`
+ * (an owner change is an update) are `false`.
+ *
+ * `modifyAllRecords` is a write grant too: the spec's `objectPermissionGrants`
+ * answers edit, delete and transfer `true` on it alone, so an entry keeping it
+ * would still answer `current_user.can(object, 'edit')` `true`. It is lowered
+ * to `viewAllRecords`, the read half it implies, so the entry keeps exactly
+ * the read it had.
+ *
+ * An object the map does not mention already grants nothing, and is left out.
+ */
+function clampExternalReadOnlyWrites(objects: Record<string, any>, forbidden: ReadonlySet<string>): void {
+  if (forbidden.size === 0) return;
+  for (const [obj, acc] of Object.entries(objects) as Array<[string, any]>) {
+    if (obj === '*' || !acc || !forbidden.has(obj)) continue;
+    acc.allowCreate = false;
+    acc.allowEdit = false;
+    acc.allowDelete = false;
+    acc.allowTransfer = false;
+    if (acc.modifyAllRecords === true) {
+      acc.modifyAllRecords = false;
+      acc.viewAllRecords = true;
+    }
+  }
+}
+
+/**
+ * [#30370] The {@link EffectiveObjectPermissionsSchemaSource.isExternalWriteForbidden}
+ * accessor over an engine: its `isExternalWriteForbidden`, the verdict objectql's
+ * own write gate (`assertWriteAllowed`) reads before it refuses a write
+ * `403 EXTERNAL_WRITE_FORBIDDEN`. That member is not on the contract's engine
+ * view, so it is asked when present; an engine without it forbids nothing.
+ * Both builders of the map (`/auth/me/permissions` and
+ * `ISecurityService.getEffectiveObjectPermissions`) hand over this one reading.
+ */
+export function engineExternalWriteForbidden(engine: unknown): (objectName: string) => boolean {
+  return (objectName) => {
+    const predicate = (engine as { isExternalWriteForbidden?: unknown } | null | undefined)?.isExternalWriteForbidden;
+    return typeof predicate === 'function' && predicate.call(engine, objectName) === true;
+  };
+}
+
 /**
  * The schema reads {@link buildEffectiveObjectPermissions} needs, as accessors
  * over whatever engine the caller holds. Every accessor is optional and every
@@ -534,6 +611,15 @@ export interface EffectiveObjectPermissionsSchemaSource {
    * the map must leave out exactly the objects the data plane refuses.
    */
   isObjectPackageDisabled?: (objectName: string) => boolean;
+  /**
+   * [#30370] Whether the external write gate (ADR-0015 §5.3 Gate 3) is closed
+   * on `objectName` — the engine's `isExternalWriteForbidden`, the verdict its
+   * own `assertWriteAllowed` refuses a write on. Hand over that predicate
+   * itself ({@link engineExternalWriteForbidden}), never a second reading of
+   * the datasource definitions: the map must withhold exactly the writes the
+   * data plane refuses.
+   */
+  isExternalWriteForbidden?: (objectName: string) => boolean;
   /** Where a failed seed / annotation pass is reported. */
   logger?: { warn?: (message: string, meta?: Record<string, unknown>) => void };
 }
@@ -604,8 +690,15 @@ export interface EffectiveObjectPermissionsInputSet {
  *     not a step, so an entry a super-user set names itself keeps that set's
  *     explicit answer, and `modifyAllRecords` alone grants no create;
  *  5. {@link clampManagedObjectWrites};
- *  6. {@link annotateEffectiveApiOperations} — guarded like (2);
- *  7. {@link omitDisabledPackageObjects} — [#28877] an object whose owning
+ *  6. {@link clampExternalReadOnlyWrites} — [#30370] an object whose external
+ *     write gate is closed grants no write, as the data plane refuses every
+ *     one; the verdict is judged for every entry before anything is clamped,
+ *     and a predicate that throws is reported and clamps nothing (guarded
+ *     like (2));
+ *  7. {@link annotateEffectiveApiOperations} — guarded like (2); [#30370] it
+ *     reads the same verdicts, so a closed gate's object is served no write
+ *     operation;
+ *  8. {@link omitDisabledPackageObjects} — [#28877] an object whose owning
  *     package is disabled is left out, as the data plane refuses it; guarded
  *     like (2).
  *
@@ -659,19 +752,33 @@ export function buildEffectiveObjectPermissions(
   }
   // Make the per-object map reflect the server's ACTUAL effective enforcement
   // = permission-set grant ∩ identity write guard (ADR-0057 D10, cited as an
-  // attribution, #9628): (1) fold each set's `'*'` super-user grant into every
+  // attribution, #9628) ∩ [#30370] external write gate (ADR-0015 §5.3): (1) fold each set's `'*'` super-user grant into every
   // entry that set does not name, so an admin's wildcard is not shadowed by
   // another set's explicit deny — [#20134] every bit it grants, `transfer` and
   // its own plain bits included; [#20136] per set only, never the merged
   // bypass, which would also override the super-user set's OWN narrower entry;
-  // (2) re-clamp guarded managed objects by their write affordance.
+  // (2) re-clamp guarded managed objects by their write affordance; (3)
+  // [#30370] re-clamp objects whose external write gate is closed.
   foldSuperUserWildcardGrants(objects, sets);
   clampManagedObjectWrites(objects, schemaOf);
+  // [#30370] Judged in full before anything is clamped, so a predicate that
+  // throws midway clamps nothing rather than half the map — and the
+  // annotation below reads these same verdicts, never a second asking.
+  let externalWriteForbidden: ReadonlySet<string> = new Set();
+  const isForbidden = source.isExternalWriteForbidden;
+  if (typeof isForbidden === 'function') {
+    try {
+      externalWriteForbidden = new Set(Object.keys(objects).filter((name) => name !== '*' && isForbidden(name) === true));
+    } catch (e: any) {
+      source.logger?.warn?.('[effective-permissions] external write gate read failed', { err: e?.message });
+    }
+  }
+  clampExternalReadOnlyWrites(objects, externalWriteForbidden);
   // [#3391] Annotate the per-object effective API operation set. Guarded: on
   // failure `apiOperations` is simply omitted and a client falls back to its
   // default-allow behaviour.
   try {
-    annotateEffectiveApiOperations(objects, schemaOf);
+    annotateEffectiveApiOperations(objects, schemaOf, (name) => externalWriteForbidden.has(name));
   } catch (e: any) {
     source.logger?.warn?.('[effective-permissions] apiOperations annotate failed', { err: e?.message });
   }
 
@@ -324,6 +324,8 @@ export {
   buildEffectiveObjectPermissions,
   // [#28877] The map's disabled-package accessor over an engine registry.
   registryObjectPackageDisabled,
+  // [#30370] The map's external-write-gate accessor over an engine.
+  engineExternalWriteForbidden,
   foldWildcardSuperUser,
   clampManagedObjectWrites,
   seedSuperUserRestrictedObjects,