@@ -0,0 +1,34 @@
+---
+'@objectstack/objectql': patch
+---
+
+fix(objectql)!: a `controlled_by_parent` detail whose master the engine cannot compose a read over now refuses the boot, instead of booting and failing at read time
+
+Clause-②: yes (narrowing)
+
+Metadata-protocol: none
+
+<!-- adr-0087: not-required (no-migration-prescription) A boot refusal of one deployment composition: no key of any metadata schema is added, removed, renamed or re-shaped, and `ObjectSchema.parse` accepts exactly what it accepted before, so `objectstack migrate meta` has nothing to rewrite and no tombstone is owed. Both facts the refusal reads are deployment facts (datasource mapping, a package's default datasource, lifecycle routing, the middleware registrations), and the remedy is the author's choice among three, which no ledger entry can derive. The other categories are closed on facts: the package publishes (not unpublished); no ADR-0087 id covers this composition (not already-registered); and nothing exported is removed or narrowed, one engine method is added (not runtime-interface-only, type-surface-only or runtime-export-retired). -->
+
+**BREAKING** (a narrowing of what boots). A stack declaring a `controlled_by_parent` detail over either class of master below booted before this change. It is now refused at `kernel:bootstrapped`, before `kernel:listening` opens the socket. It ships as `patch` because no metadata protocol shape moves.
+
+ADR-0139 D5.2 and D5.3 record two classes of master the engine composes no `ReadableIds` leaf over, and refuses by name at read time:
+
+- **(a)** a master bound to another datasource than the detail. No driver evaluates a subquery across two datasources.
+- **(b)** a master whose rows an object-scoped read middleware narrows (`registerMiddleware(fn, { object })`), for example `sys_attachment`, `sys_comment`, `sys_activity`, `sys_audit_log`, `sys_mail_message` or `sys_approval_request`. That WHERE is built at read time and is no part of the master's read scope, so a leaf over it would be wider than a read of the master.
+
+A `controlled_by_parent` detail derives its access from its one required master (ADR-0055 §1). A detail over such a master is a declaration the runtime cannot honour, so under ADR-0049 it is no longer admitted. `ObjectQLPlugin` refuses the boot with `INVALID_METADATA` / 422, naming each detail, its master field, the master and the class, and the remedies below.
+
+- The check is judged at `kernel:bootstrapped`, not at `kernel:ready` or `registerApp`. Several platform plugins (mailbox, audit, attachment storage) register their object-scoped read middleware from their own `kernel:ready` handler, which runs after the engine's, so only then are both facts final.
+- It reuses the read path's own predicate (`hasObjectMiddleware` and the datasource binding resolution), so the boot rule and the read rule cannot drift. The read-time refusal is unchanged.
+- New engine method: `ObjectQL#findUnservableControlledByParentMasters()` lists the offending details.
+
+No producer is known to be affected. HotCRM's six `controlled_by_parent` objects all sit on one datasource over masters with no object-scoped read middleware, and no in-repo declaration has either shape.
+
+### Remedy
+
+Pick one, for each detail the refusal names:
+
+- bind the detail and its master to one datasource (the same `datasource`, mapping rule or package default);
+- or choose a master that no object-scoped read middleware narrows;
+- or declare the detail with a sharing model other than `controlled_by_parent`, and grant its access directly.
@@ -61,7 +61,7 @@ import {
   readableIdsRefusalError,
   type ComposableReadableIdsSite,
 } from './filter-comparand-shape.js';
-import { ReadableIds, RLS_DENY_FILTER, markFilterSubtreeProvenance } from '@objectstack/spec/data';
+import { ReadableIds, RLS_DENY_FILTER, markFilterSubtreeProvenance, isControlledByParentMasterField } from '@objectstack/spec/data';
 import type { ISecurityService } from '@objectstack/spec/contracts';
 import {
   assertHavingResolvedTemporalTokensInRange,
@@ -4845,6 +4845,24 @@ interface ReadableIdsChain {
  */
 const READABLE_IDS_MAX_CHAIN_DEPTH = 8;
 
+/**
+ * [ADR-0139 D5.2 / D5.3] A `controlled_by_parent` detail whose master the
+ * engine composes no `ReadableIds` leaf over —
+ * `ObjectQL#findUnservableControlledByParentMasters`, refused at boot by
+ * `ObjectQLPlugin`.
+ */
+export type UnservableControlledByParentMaster = {
+  /** The `controlled_by_parent` detail. */
+  readonly detail: string;
+  /** Its one required `master_detail` field. */
+  readonly field: string;
+  /** The object that field names. */
+  readonly master: string;
+} & (
+  | { readonly class: 'object-scoped-read-middleware' }
+  | { readonly class: 'other-datasource'; readonly objectDatasource: string | undefined; readonly parentDatasource: string | undefined }
+);
+
 /**
  * [ADR-0139 D2] The engine slot where `ObjectQLPlugin` puts the SOURCE the
  * `ReadableIds` composition reads the registered `ISecurityService` from: a
@@ -6543,27 +6561,77 @@ export class ObjectQL implements IObjectQLEngine {
       `such leaf ${why}. The query was NOT run and no driver was asked. Read this class through its bounded ` +
       'probe, chosen before the leaf is written.',
     );
-    const outer = this.resolveDatasourceBinding(object)?.datasource;
     const composable: string[] = [];
     for (const [parent, site] of firstSite) {
       // A parent the registry does not hold has no record anyone may read:
       // its leaf is answered `$in: []` without asking anything, and it is in
       // none of D5's classes.
       if (!this._registry.getObject(parent)) continue;
-      if (this.hasObjectMiddleware(parent)) {
+      const uncomposable = this.uncomposableReadableIdsParent(object, parent);
+      if (uncomposable?.class === 'object-scoped-read-middleware') {
         throw refuse(site, `over '${parent}', whose rows an object-scoped read middleware narrows: that WHERE is ` +
           `built at read time and is no part of its read scope, so the composed leaf would be wider than a read of '${parent}'`);
       }
-      const bound = this.resolveDatasourceBinding(parent)?.datasource;
-      if (bound !== outer) {
-        throw refuse(site, `over '${parent}', which is bound to datasource '${String(bound)}' while '${object}' is ` +
-          `bound to '${String(outer)}': no driver evaluates a subquery across two datasources`);
+      if (uncomposable?.class === 'other-datasource') {
+        throw refuse(site, `over '${parent}', which is bound to datasource '${String(uncomposable.parentDatasource)}' while '${object}' is ` +
+          `bound to '${String(uncomposable.objectDatasource)}': no driver evaluates a subquery across two datasources`);
       }
       composable.push(parent);
     }
     return composable;
   }
 
+  /**
+   * [ADR-0139 D5.2 / D5.3] Which of D5's two remaining classes a leaf over
+   * `parent` in a read of `object` falls in, or `undefined` when it falls in
+   * neither — the ONE predicate behind both the read-time refusal
+   * ({@link refuseUncomposableReadableIdsClasses}) and the boot-time refusal of
+   * a `controlled_by_parent` detail over such a master
+   * ({@link findUnservableControlledByParentMasters}), so the two rules cannot
+   * drift. D5.2 is judged first, as the read path always has.
+   */
+  private uncomposableReadableIdsParent(object: string, parent: string):
+    | { class: 'object-scoped-read-middleware' }
+    | { class: 'other-datasource'; objectDatasource: string | undefined; parentDatasource: string | undefined }
+    | undefined {
+    if (this.hasObjectMiddleware(parent)) return { class: 'object-scoped-read-middleware' };
+    const objectDatasource = this.resolveDatasourceBinding(object)?.datasource;
+    const parentDatasource = this.resolveDatasourceBinding(parent)?.datasource;
+    if (parentDatasource !== objectDatasource) return { class: 'other-datasource', objectDatasource, parentDatasource };
+    return undefined;
+  }
+
+  /**
+   * [ADR-0139 D5.2 / D5.3 · ADR-0049] Every registered `controlled_by_parent`
+   * detail whose master the engine composes no `ReadableIds` leaf over — a
+   * master an object-scoped read middleware narrows, or one bound to another
+   * datasource than the detail — judged by the read path's own predicate
+   * ({@link uncomposableReadableIdsParent}). A detail's access derives from its
+   * one required `master_detail` (ADR-0055 §1), so such a declaration is one
+   * the runtime cannot honour: `ObjectQLPlugin` refuses the boot on any entry.
+   *
+   * Both facts are deployment facts (the datasource mapping, a package's
+   * default datasource, lifecycle routing, the middleware registrations), so
+   * the answer is final only once every plugin has registered its middleware —
+   * which several do inside their own `kernel:ready` handler. Asked earlier, it
+   * is short. A detail with no single required master, or whose master the
+   * registry does not hold, is no entry: other rules own those.
+   */
+  findUnservableControlledByParentMasters(): UnservableControlledByParentMaster[] {
+    const found: UnservableControlledByParentMaster[] = [];
+    for (const object of this._registry.getAllObjects() as Array<{ name?: string; sharingModel?: unknown; fields?: Record<string, unknown> }>) {
+      if (object?.sharingModel !== 'controlled_by_parent' || typeof object.name !== 'string') continue;
+      const masters = Object.entries(object.fields ?? {}).filter(([, f]) => isControlledByParentMasterField(f));
+      if (masters.length !== 1) continue;
+      const [field, def] = masters[0];
+      const master = (def as { reference?: unknown }).reference;
+      if (typeof master !== 'string' || !this._registry.getObject(master)) continue;
+      const uncomposable = this.uncomposableReadableIdsParent(object.name, master);
+      if (uncomposable) found.push({ detail: object.name, field, master, ...uncomposable });
+    }
+    return found;
+  }
+
   /**
    * [ADR-0139 D2 steps 1-2] The scope a leaf over `parent` is composed with,
    * or `null` for `$in: []`. Fails closed on every answer that is not a
 
@@ -0,0 +1,187 @@
+// Copyright (c) 2026 ObjectStack. Licensed under the Apache-2.0 license.
+
+/**
+ * [ADR-0139 D5.2 / D5.3 · ADR-0049] A `controlled_by_parent` detail whose
+ * master the engine composes no `ReadableIds` leaf over fails the BOOT, naming
+ * the detail, the master, the class and the remedy — never admitted to answer
+ * 500 at read time:
+ *
+ *  - (a) a master bound to another datasource than the detail;
+ *  - (b) a master an object-scoped read middleware narrows.
+ *
+ * Booted through a real `ObjectKernel` and `ObjectQLPlugin`. The middleware is
+ * registered the way the platform's own gates are (mailbox, audit, attachment):
+ * from the owning plugin's `kernel:ready` handler, which runs AFTER the
+ * engine's — so a check made at the engine's `kernel:ready` would not see it.
+ */
+
+import { describe, it, expect, afterEach } from 'vitest';
+import { ObjectKernel, type PluginContext } from '@objectstack/core';
+import { ObjectQLPlugin } from './plugin.js';
+import type { ObjectQL } from './engine.js';
+
+interface ManifestService {
+  register(artifact: unknown): Promise<void> | void;
+}
+
+const kernels: ObjectKernel[] = [];
+afterEach(async () => {
+  while (kernels.length) {
+    const kernel = kernels.pop()!;
+    try { if (kernel.getState() === 'running') await kernel.shutdown(); } catch { /* noop */ }
+  }
+});
+
+const driver = (name: string): any => ({
+  name, version: '0.0.0', supports: {},
+  async connect() {}, async disconnect() {}, async checkHealth() { return true; },
+  async find() { return []; }, async findOne() { return null; }, async count() { return 0; },
+});
+
+/** Registers the drivers and the artifacts during init, the way a host composes a stack. */
+function stack(artifacts: unknown[], drivers: string[] = ['primary']) {
+  return {
+    name: 'test.stack',
+    dependencies: ['com.objectstack.engine.objectql'],
+    init: async (ctx: PluginContext) => {
+      const ql = ctx.getService<ObjectQL>('objectql');
+      drivers.forEach((name, i) => ql.registerDriver(driver(name), i === 0));
+      const manifest = ctx.getService<ManifestService>('manifest');
+      for (const artifact of artifacts) await manifest.register(artifact);
+    },
+  };
+}
+
+/** Registers a read middleware from its own `kernel:ready` handler — as late as the platform's gates register. */
+function lateReadGate(options?: { object?: string }) {
+  return {
+    name: 'test.late-read-gate',
+    dependencies: ['com.objectstack.engine.objectql'],
+    init: async () => {},
+    start: async (ctx: PluginContext) => {
+      ctx.hook('kernel:ready', async () => {
+        ctx.getService<ObjectQL>('objectql').registerMiddleware(async (_op, next) => next(), options);
+      });
+    },
+  };
+}
+
+async function boot(...plugins: any[]): Promise<{ kernel: ObjectKernel; err: any }> {
+  const kernel = new ObjectKernel({ logger: { level: 'silent' }, gracefulShutdown: false });
+  kernels.push(kernel);
+  await kernel.use(new ObjectQLPlugin());
+  for (const p of plugins) await kernel.use(p);
+  const err = await kernel.bootstrap().then(() => undefined, (e) => e);
+  return { kernel, err };
+}
+
+const master = (name: string, extra: Record<string, unknown> = {}) => ({
+  name, ...extra, fields: { title: { name: 'title', type: 'text' } },
+});
+const detail = (name: string, masterName: string, extra: Record<string, unknown> = {}) => ({
+  name,
+  sharingModel: 'controlled_by_parent',
+  ...extra,
+  fields: { parent: { name: 'parent', type: 'master_detail', reference: masterName, required: true } },
+});
+const app = (objects: unknown[]) => ({ id: 'com.test.cbp', name: 'cbp', objects });
+
+const REMEDY = 'Bind the detail and its master to one datasource; or choose a master without an object-scoped read '
+  + 'middleware; or declare the detail without `controlled_by_parent`.';
+
+describe('[ADR-0139 D5.2 / D5.3] a controlled_by_parent detail over a master the engine cannot compose a read over', () => {
+  it('(a) a master bound to another datasource refuses the boot, naming both datasources and the remedy', async () => {
+    const { err } = await boot(stack(
+      [app([master('cbp_master', { datasource: 'archive' }), detail('cbp_detail', 'cbp_master')])],
+      ['primary', 'archive'],
+    ));
+    expect(err).toMatchObject({ code: 'INVALID_METADATA', status: 422 });
+    expect(err.message).toContain(
+      "'cbp_detail' (master field 'parent') over master 'cbp_master', which is bound to datasource 'archive' "
+      + "while 'cbp_detail' is bound to 'primary' (ADR-0139 D5.3)",
+    );
+    expect(err.message).toContain(REMEDY);
+  });
+
+  it('(b) a master an object-scoped read middleware narrows — registered at kernel:ready — refuses the boot', async () => {
+    const { err } = await boot(
+      stack([app([master('cbp_master'), detail('cbp_detail', 'cbp_master')])]),
+      lateReadGate({ object: 'cbp_master' }),
+    );
+    expect(err).toMatchObject({ code: 'INVALID_METADATA', status: 422 });
+    expect(err.message).toContain(
+      "'cbp_detail' (master field 'parent') over master 'cbp_master', whose rows an object-scoped read middleware "
+      + 'narrows (ADR-0139 D5.2)',
+    );
+    expect(err.message).toContain(REMEDY);
+  });
+
+  it('(b) a detail mastered by sys_attachment, gated as the storage plugin gates it, refuses the boot', async () => {
+    const { err } = await boot(
+      stack([app([master('sys_attachment'), detail('cbp_attachment_note', 'sys_attachment')])]),
+      lateReadGate({ object: 'sys_attachment' }),
+    );
+    expect(err).toMatchObject({ code: 'INVALID_METADATA', status: 422 });
+    expect(err.message).toContain("'cbp_attachment_note' (master field 'parent') over master 'sys_attachment'");
+  });
+
+  it('names every offending detail in one refusal', async () => {
+    const { err } = await boot(
+      stack(
+        [app([
+          master('cbp_gated'), detail('cbp_detail_b', 'cbp_gated'),
+          master('cbp_far', { datasource: 'archive' }), detail('cbp_detail_a', 'cbp_far'),
+        ])],
+        ['primary', 'archive'],
+      ),
+      lateReadGate({ object: 'cbp_gated' }),
+    );
+    expect(err).toMatchObject({ code: 'INVALID_METADATA', status: 422 });
+    expect(err.message).toMatch(/^2 controlled_by_parent details derive their access/);
+    expect(err.message).toContain("over master 'cbp_gated'");
+    expect(err.message).toContain("over master 'cbp_far'");
+  });
+});
+
+describe('[ADR-0139 D5.2 / D5.3] controls: a servable controlled_by_parent master boots unchanged', () => {
+  // HotCRM's six controlled_by_parent shapes (e6d5d3e): every master a crm_* object on the one datasource, with no
+  // object-scoped read middleware on any of them — while the platform gates its own system objects.
+  const HOTCRM = [
+    master('crm_account'), master('crm_opportunity'), master('crm_activity'),
+    detail('crm_contact', 'crm_account'),
+    detail('crm_quote', 'crm_opportunity'),
+    detail('crm_contract', 'crm_account'),
+    detail('crm_quote_line', 'crm_quote'), // a two-level chain: its master is controlled_by_parent too
+    detail('crm_opportunity_line', 'crm_opportunity'),
+    detail('crm_activity_participant', 'crm_activity'),
+  ];
+
+  it("HotCRM's six details boot, with an object-scoped read middleware on a system object no detail is mastered by", async () => {
+    const { kernel, err } = await boot(stack([app([...HOTCRM, master('sys_comment')])]), lateReadGate({ object: 'sys_comment' }));
+    expect(err).toBeUndefined();
+    expect(kernel.getService<ObjectQL>('objectql').findUnservableControlledByParentMasters()).toEqual([]);
+  });
+
+  it('a global middleware (no object, or "*") is keyed to no master and does not refuse', async () => {
+    const one = await boot(stack([app([master('cbp_master'), detail('cbp_detail', 'cbp_master')])]), lateReadGate());
+    expect(one.err).toBeUndefined();
+    const star = await boot(stack([app([master('cbp_master'), detail('cbp_detail', 'cbp_master')])]), lateReadGate({ object: '*' }));
+    expect(star.err).toBeUndefined();
+  });
+
+  it('a detail and its master bound explicitly to the same second datasource boot', async () => {
+    const { err } = await boot(stack(
+      [app([master('cbp_master', { datasource: 'archive' }), detail('cbp_detail', 'cbp_master', { datasource: 'archive' })])],
+      ['primary', 'archive'],
+    ));
+    expect(err).toBeUndefined();
+  });
+
+  it('a master on another datasource under a detail that is NOT controlled_by_parent boots', async () => {
+    const { err } = await boot(stack(
+      [app([master('cbp_master', { datasource: 'archive' }), { ...detail('cbp_detail', 'cbp_master'), sharingModel: 'private' }])],
+      ['primary', 'archive'],
+    ));
+    expect(err).toBeUndefined();
+  });
+});