@@ -0,0 +1,18 @@
+---
+'@objectstack/plugin-security': patch
+---
+
+fix(plugin-security): `security/explain` asks the sharing read filter with the caller's read depth, so a record's `read` verdict matches what the caller's `find` returns (#19986)
+
+Clause-②: no
+
+`POST /api/v1/security/explain` with `{ object, operation: 'read', recordId }` answered `decision.record.visible: false` (`decidedBy: 'sharing'`) on rows that the same caller's `find` returned. It happened on every object whose OWD is private (set explicitly, or left unset), for a caller whose read depth is wider than `own`. The find path hands the sharing service's read filter the caller's effective read depth. Explain asked the same filter without it, so a caller with `org` read depth was judged owner-only on every row it did not own, and a caller with unit read depth was judged owner-only on rows its unit owns.
+
+Explain now passes the same read depth, computed the way the find path computes it. A read depth already present on the explained context no longer decides the report.
+
+Unchanged:
+
+- Enforcement: `find` admits and refuses exactly what it did before.
+- Writes (`update` / `delete`) and object-level explanations (no `recordId`).
+- A caller acting on behalf of another user (`onBehalfOf`): its record-level read explanation uses the same inputs as before.
+- Objects whose OWD is not private already matched and still do.
@@ -0,0 +1,343 @@
+// Copyright (c) 2026 ObjectStack. Licensed under the Apache-2.0 license.
+//
+// `security/explain` for a READ must ask plugin-sharing's read filter with the
+// same read DEPTH the find path hands it, so its `record.visible` equals whether
+// the caller's `find` returns the row.
+//
+// The measured divergence: on a private-OWD object, explain answered
+// `record.visible: false` (`decidedBy: 'sharing'`) for `read` on rows the same
+// caller's `find` RETURNED, through the same stack. The middleware (step 2.6)
+// stamps `__readScope` on the context before plugin-sharing's `buildReadFilter`
+// reads it; explain asked the same filter with the bare context, so an `org`
+// reader got an owner-only filter where `find` got none, and a `unit` reader
+// got `owner_id = me` where `find` got the unit's owners. It fails CLOSED — the
+// report under-states visibility, enforcement is right — and it is the read
+// twin of the write-depth stamp in `explain-write-verdict-inputs.test.ts`.
+//
+// This file wires the REAL SecurityPlugin (middleware + explain entry point),
+// the REAL SharingService and sharing middleware, and the REAL platform
+// `member_default` seed over one in-memory engine, and asserts one property per
+// cell: explain's `record.visible` equals the find's outcome. A cell that
+// asserts only one side would pin nothing about the agreement this file exists
+// for.
+import { describe, it, expect, vi } from 'vitest';
+import { assertEngineFindOnePredicate } from '@objectstack/metadata-core';
+import { SharingService, buildSharingMiddleware } from '@objectstack/plugin-sharing';
+import { PermissionSetSchema } from '@objectstack/spec/security';
+import type { PermissionSet } from '@objectstack/spec/security';
+import { SecurityPlugin } from './security-plugin.js';
+import { defaultPermissionSets } from './objects/default-permission-sets.js';
+
+// ── metadata ───────────────────────────────────────────────────────────────
+
+const OBJECT = 'kpi_entry_line';
+
+const fieldsOf = (...names: string[]) =>
+  Object.fromEntries(names.map((n) => [n, { name: n }]));
+
+/**
+ * `sharingModel` UNSET, which ADR-0090 D1 resolves to `private` (fail-closed
+ * default), so plugin-sharing's owner-match is in play for every reader.
+ */
+const PRIVATE_SCHEMA = {
+  name: OBJECT,
+  fields: fieldsOf('id', 'name', 'value', 'owner_id', 'created_by', 'organization_id'),
+};
+
+/** The OWD control: the object's own model opens reads. */
+const PUBLIC_READ_SCHEMA = { ...PRIVATE_SCHEMA, sharingModel: 'public_read' };
+
+const MEMBER_DEFAULT = defaultPermissionSets.find((p) => p.name === 'member_default')!;
+const ADMIN_FULL_ACCESS = defaultPermissionSets.find((p) => p.name === 'admin_full_access')!;
+
+const readerAt = (name: string, readScope: 'own' | 'unit' | 'org'): PermissionSet =>
+  PermissionSetSchema.parse({
+    name,
+    objects: { [OBJECT]: { allowRead: true, readScope } },
+  });
+
+/** Read depth `org` — an HR reviewer who may read any line. */
+const HR_REVIEWER = readerAt('hr_reviewer', 'org');
+/** Read depth `unit` — a team lead who reads the lines their unit owns. */
+const TEAM_LEAD = readerAt('team_lead', 'unit');
+/** Read depth `own` — widened only by ownership or a share. The control. */
+const DEPT_REPORTER = readerAt('dept_reporter', 'own');
+
+const PERMISSION_SETS: PermissionSet[] = [MEMBER_DEFAULT, ADMIN_FULL_ACCESS, HR_REVIEWER, TEAM_LEAD, DEPT_REPORTER];
+
+// ── principals and rows ────────────────────────────────────────────────────
+
+const U_ADMIN = 'u_admin';
+const U_HR = 'u_hr';
+const U_LEAD = 'u_lead';
+const U_REPORTER = 'u_reporter';
+
+const ctxFor = (userId: string, permission: string) => ({
+  userId, tenantId: 'org1', positions: ['org_member'], permissions: [permission],
+});
+
+const ADMIN_CTX = ctxFor(U_ADMIN, 'admin_full_access');
+const HR_CTX = ctxFor(U_HR, 'hr_reviewer');
+const LEAD_CTX = ctxFor(U_LEAD, 'team_lead');
+const REPORTER_CTX = ctxFor(U_REPORTER, 'dept_reporter');
+
+/**
+ * The lead's unit is the lead and the reporter. Both sides consult this ONE
+ * resolver through plugin-sharing, so a `unit` cell tests the depth input, not
+ * two hierarchies.
+ */
+const UNIT_OWNERS = [U_LEAD, U_REPORTER];
+
+type RowKey = 'shared' | 'owned' | 'unshared';
+
+const ROWS: Record<RowKey, Record<string, unknown>> = {
+  /** Owned by the admin; the reporter holds a `read` share on it. */
+  shared: { id: 'kle_shared', name: 'Shared', value: 1, owner_id: U_ADMIN, created_by: U_ADMIN, organization_id: 'org1' },
+  /** Owned by the reporter — inside the lead's unit. */
+  owned: { id: 'kle_owned', name: 'Owned', value: 1, owner_id: U_REPORTER, created_by: U_ADMIN, organization_id: 'org1' },
+  /** Neither shared with nor owned by the reporter or the lead's unit. */
+  unshared: { id: 'kle_unshared', name: 'Unshared', value: 1, owner_id: U_ADMIN, created_by: U_ADMIN, organization_id: 'org1' },
+};
+
+const READ_SHARE = {
+  id: 'shr_read', object_name: OBJECT, record_id: ROWS.shared.id,
+  recipient_type: 'user', recipient_id: U_REPORTER, access_level: 'read', source: 'manual',
+};
+
+// ── in-memory engine ───────────────────────────────────────────────────────
+
+function makeEngine(schema: Record<string, unknown>) {
+  const tables: Record<string, any[]> = {
+    [OBJECT]: (Object.keys(ROWS) as RowKey[]).map((k) => ({ ...ROWS[k] })),
+    sys_record_share: [{ ...READ_SHARE }],
+  };
+  // `$or` / `$and` conjoin WITH their sibling keys, the way a real driver ANDs
+  // them (#7620). An operator this double does not know THROWS rather than
+  // comparing an object to a scalar: a matcher that silently answers `false`
+  // would green every refused cell below for the wrong reason.
+  const matches = (row: any, filter: any): boolean => {
+    if (!filter || typeof filter !== 'object') return true;
+    if (Array.isArray(filter.$or) && !filter.$or.some((f: any) => matches(row, f))) return false;
+    if (Array.isArray(filter.$and) && !filter.$and.every((f: any) => matches(row, f))) return false;
+    for (const [k, v] of Object.entries(filter)) {
+      if (k === '$or' || k === '$and') continue;
+      if (k.startsWith('$')) throw new Error(`engine double: unsupported operator '${k}'`);
+      if (v != null && typeof v === 'object') {
+        const ops = Object.keys(v as object);
+        if (ops.length !== 1 || ops[0] !== '$in') {
+          throw new Error(`engine double: unsupported predicate on '${k}': ${JSON.stringify(v)}`);
+        }
+        if (!(v as any).$in.includes(row[k])) return false;
+        continue;
+      }
+      if (row[k] !== v) return false;
+    }
+    return true;
+  };
+  const middlewares: any[] = [];
+  return {
+    _tables: tables,
+    _middlewares: middlewares,
+    registerMiddleware: (mw: any) => middlewares.push(mw),
+    getSchema: (name: string) => (name === OBJECT ? schema : undefined),
+    async find(object: string, options: any = {}) {
+      const rows = (tables[object] ??= []);
+      return rows.filter((r) => matches(r, options.filter ?? options.where)).slice(0, options.limit ?? 1000);
+    },
+    async findOne(object: string, options: any = {}) {
+      assertEngineFindOnePredicate(object, options);
+      const rows = await this.find(object, { ...options, limit: 1 });
+      return rows[0] ?? null;
+    },
+  };
+}
+
+// ── the stack ──────────────────────────────────────────────────────────────
+
+interface Stack {
+  explain: (rowKey: RowKey, context: any) => Promise<any>;
+  /** The caller's `find` for this one row, through BOTH real middlewares. */
+  find: (rowKey: RowKey, context: any) => Promise<any[]>;
+  /** Every context explain handed plugin-sharing's read filter. */
+  readFilterContexts: any[];
+}
+
+async function makeStack(opts: { schema?: Record<string, unknown> } = {}): Promise<Stack> {
+  const schema = opts.schema ?? PRIVATE_SCHEMA;
+  const engine = makeEngine(schema);
+  const metadata = {
+    get: async (_type: string, name: string) => (name === OBJECT ? schema : null),
+    list: async () => PERMISSION_SETS,
+  };
+  let security: any;
+  let sharing: SharingService;
+  const services: Record<string, any> = {
+    manifest: { register: vi.fn() },
+    objectql: engine,
+    metadata,
+    // Org scoping active, so Layer 0 contributes a real tenant predicate.
+    'org-scoping': { name: 'org-scoping' },
+    get sharing() { return sharing; },
+  };
+  const ctx: any = {
+    logger: { info: vi.fn(), warn: vi.fn(), error: vi.fn(), debug: vi.fn() },
+    registerService: (name: string, impl: any) => { if (name === 'security') security = impl; },
+    getService: (name: string) => {
+      if (!(name in services)) throw new Error(`service not registered: ${name}`);
+      return services[name];
+    },
+  };
+  const plugin = new SecurityPlugin({ fallbackPermissionSet: 'member_default' });
+  await plugin.init(ctx);
+  await plugin.start(ctx);
+  if (!security) throw new Error('SecurityPlugin did not register the security service');
+
+  sharing = new SharingService({
+    engine: engine as any,
+    securityService: () => security,
+    hierarchyResolver: () => ({
+      resolveOwnerIds: async (input: { userId: string }, scope: string) =>
+        (scope === 'unit' && input.userId === U_LEAD ? [...UNIT_OWNERS] : [input.userId]),
+    }) as any,
+  });
+  const sharingMw = buildSharingMiddleware(sharing, ctx.logger);
+  const securityMw = engine._middlewares[0];
+  const idOf = (rowKey: RowKey) => String(ROWS[rowKey].id);
+
+  // Recorded for the on-behalf-of pin; the call itself goes through unchanged.
+  const readFilterContexts: any[] = [];
+  const buildReadFilter = sharing.buildReadFilter.bind(sharing);
+  let explaining = false;
+  sharing.buildReadFilter = async (o: string, c: any) => {
+    if (explaining) readFilterContexts.push(c);
+    return buildReadFilter(o, c);
+  };
+
+  return {
+    readFilterContexts,
+    async explain(rowKey, context) {
+      explaining = true;
+      try {
+        return await security.explain({ object: OBJECT, operation: 'read', recordId: idOf(rowKey) }, { ...context });
+      } finally {
+        explaining = false;
+      }
+    },
+    async find(rowKey, context) {
+      const where = { id: idOf(rowKey) };
+      const opCtx: any = {
+        object: OBJECT,
+        operation: 'find',
+        context: { ...context },
+        options: { where },
+        ast: { where },
+      };
+      let result: any[] | undefined;
+      await securityMw(opCtx, async () => {
+        await sharingMw(opCtx, async () => {
+          result = await engine.find(OBJECT, { where: opCtx.ast.where });
+        });
+      });
+      if (!result) throw new Error('a middleware swallowed the find');
+      return result;
+    },
+  };
+}
+
+/**
+ * One cell: explain FIRST, then the find, then the agreement. The find's own
+ * answer is asserted too, so a cell cannot go green by both sides drifting.
+ */
+async function expectCell(stack: Stack, rowKey: RowKey, context: any, expected: boolean): Promise<any> {
+  const decision = await stack.explain(rowKey, context);
+  const rows = await stack.find(rowKey, context);
+  const found = rows.some((r) => r.id === ROWS[rowKey].id);
+  const cell = `${context.userId} × ${rowKey} × read`;
+  expect(found, `${cell}: the find returns the row`).toBe(expected);
+  expect(
+    decision.record?.visible,
+    `${cell}: explain record.visible (decidedBy ${decision.record?.decidedBy}) must equal the find's outcome`,
+  ).toBe(found);
+  return decision;
+}
+
+// ───────────────────────────────────────────────────────────────────────────
+
+describe('explain(read) agrees with the find, cell by cell (private OWD)', () => {
+  const cells: Array<[string, RowKey, any, boolean]> = [
+    ['builtin admin', 'unshared', ADMIN_CTX, true],
+    ['hr_reviewer (org depth)', 'shared', HR_CTX, true],
+    ['hr_reviewer (org depth)', 'owned', HR_CTX, true],
+    ['hr_reviewer (org depth)', 'unshared', HR_CTX, true],
+    ['team_lead (unit depth), owned inside the unit', 'owned', LEAD_CTX, true],
+    ['team_lead (unit depth), owned outside the unit', 'unshared', LEAD_CTX, false],
+    ['team_lead (unit depth), shared to someone else', 'shared', LEAD_CTX, false],
+    ['dept_reporter (own depth) via read share', 'shared', REPORTER_CTX, true],
+    ['dept_reporter (own depth) as owner', 'owned', REPORTER_CTX, true],
+    ['dept_reporter (own depth), unshared and not owned', 'unshared', REPORTER_CTX, false],
+  ];
+  it.each(cells)('%s × %s row', async (_label, rowKey, context, expected) => {
+    await expectCell(await makeStack(), rowKey, context, expected);
+  });
+
+  it('negative control: the refused cell is refused by the sharing layer explain reports', async () => {
+    const decision = await expectCell(await makeStack(), 'unshared', REPORTER_CTX, false);
+    expect(decision.record.decidedBy).toBe('sharing');
+    expect(decision.layers.find((l: any) => l.layer === 'sharing').record.outcome).toBe('excluded');
+  });
+});
+
+describe('the read depth: explain stamps it the way step 2.6 does', () => {
+  it('an org-depth reader is admitted by the sharing layer on an unshared, not-owned row', async () => {
+    const decision = await expectCell(await makeStack(), 'unshared', HR_CTX, true);
+    const sharingRecord = decision.layers.find((l: any) => l.layer === 'sharing').record;
+    // `org` depth: plugin-sharing imposes no owner-match, which is what the
+    // find saw (its AST carries only the id and tenant terms).
+    expect(sharingRecord.outcome).toBe('admitted');
+    expect(sharingRecord.rowFilter).toBeNull();
+  });
+
+  it('a depth the CALLER brings does not decide — explain computes it, as step 2.6 overwrites it (widening)', async () => {
+    // One variable: `__readScope` stamped on the explained context. The find
+    // path overwrites any such key before plugin-sharing reads it, so it
+    // refuses; explain must not be widened by it either.
+    const forged = { ...REPORTER_CTX, __readScope: 'org' };
+    await expectCell(await makeStack(), 'unshared', forged, false);
+  });
+
+  it('a depth the CALLER brings does not decide — explain computes it, as step 2.6 overwrites it (narrowing)', async () => {
+    const forged = { ...HR_CTX, __readScope: 'own' };
+    await expectCell(await makeStack(), 'unshared', forged, true);
+  });
+});
+
+describe('the on-behalf-of path keeps its previous inputs', () => {
+  it("explain hands plugin-sharing's read filter the delegated context unchanged", async () => {
+    // The middleware's delegated read depth (the agent-leg intersection, plus
+    // a second filter AND-ed in under the delegator's identity) is not
+    // modelled on explain's record path. Stamping the AGENT's own depth here
+    // without that second filter could only widen the report past what the
+    // delegated find returns, so the delegated context is passed as it was.
+    const stack = await makeStack();
+    const delegated = { ...HR_CTX, onBehalfOf: { userId: U_REPORTER } };
+    await stack.explain('unshared', delegated);
+    expect(stack.readFilterContexts.length, 'explain consulted the read filter').toBeGreaterThan(0);
+    for (const c of stack.readFilterContexts) {
+      expect(c.onBehalfOf?.userId).toBe(U_REPORTER);
+      expect('__readScope' in c, 'no read depth stamped on a delegated context').toBe(false);
+    }
+  });
+});
+
+describe('OWD control: `public_read` — the object\'s own model opens reads', () => {
+  const principals: Array<[string, any]> = [
+    ['hr_reviewer', HR_CTX],
+    ['team_lead', LEAD_CTX],
+    ['dept_reporter', REPORTER_CTX],
+  ];
+  const rows: RowKey[] = ['shared', 'owned', 'unshared'];
+  const cells = principals.flatMap(([label, context]) => rows.map((r) => [label, r, context] as const));
+  it.each(cells)('%s × %s row: both admit', async (_label, rowKey, context) => {
+    await expectCell(await makeStack({ schema: PUBLIC_READ_SCHEMA }), rowKey, context, true);
+  });
+});