@@ -42,21 +42,18 @@ import { ObjectQL } from './engine.js';
 const REMOTE = 'remote_ds';
 const PACKAGE_ID = 'test-21910';
 
-type Rows = Map<string, Map<string, Record<string, unknown>>>;
+type Row = Record<string, unknown>;
 
 /**
  * A stub driver that records every read into a shared log and can be told to
- * refuse reads of one object with an exact error object.
+ * refuse reads of one object with an exact error object. Its `find` applies
+ * the caller's `limit` after the filter, by presence.
  */
 function makeDriver(name: string, log: { reads: string[]; begun: number }) {
-  const stores: Rows = new Map();
+  const tables: Record<string, Row[]> = {};
   const failReads = new Map<string, unknown>();
-  const storeFor = (o: string) => {
-    let s = stores.get(o);
-    if (!s) { s = new Map(); stores.set(o, s); }
-    return s;
-  };
-  const matches = (row: Record<string, unknown>, where: any): boolean => {
+  const rowsOf = (o: string): Row[] => (tables[o] ??= []);
+  const matches = (row: Row, where: any): boolean => {
     if (!where || typeof where !== 'object') return true;
     for (const [k, v] of Object.entries(where)) {
       if (k.startsWith('$')) continue;
@@ -65,47 +62,55 @@ function makeDriver(name: string, log: { reads: string[]; begun: number }) {
     }
     return true;
   };
-  const gate = (o: string) => {
-    log.reads.push(o);
-    if (failReads.has(o)) throw failReads.get(o);
-  };
   const driver: any = {
     name, version: '0.0.0', supports: {},
     async connect() {}, async disconnect() {}, async checkHealth() { return true; }, async execute() { return null; },
     async syncSchema() {},
     registerExternalObject() {},
     async find(o: string, ast: any) {
-      gate(o);
-      return Array.from(storeFor(o).values()).filter((r) => matches(r, ast?.where));
+      log.reads.push(o);
+      const failure = failReads.get(o);
+      if (failure !== undefined) throw failure;
+      const hit = (tables[o] ?? []).filter((r) => matches(r, ast?.where));
+      return typeof ast?.limit === 'number' ? hit.slice(0, ast.limit) : hit;
     },
     async findOne(o: string, ast: any) {
-      gate(o);
-      for (const r of storeFor(o).values()) if (matches(r, ast?.where)) return r;
-      return null;
+      const [first] = await this.find(o, { ...ast, limit: 1 });
+      return first ?? null;
     },
     async count(o: string, ast: any) {
-      gate(o);
-      return Array.from(storeFor(o).values()).filter((r) => matches(r, ast?.where)).length;
+      return (await this.find(o, { where: ast?.where })).length;
     },
-    async create(o: string, data: Record<string, unknown>) {
+    async create(o: string, data: Row) {
       const row = { ...data, id: String(data.id) };
-      storeFor(o).set(row.id, row);
+      rowsOf(o).push(row);
       return row;
     },
-    async update(o: string, id: string, data: Record<string, unknown>) {
-      const cur = storeFor(o).get(String(id));
-      if (!cur) throw new Error(`not found ${o}/${id}`);
-      const up = { ...cur, ...data, id: String(id) };
-      storeFor(o).set(String(id), up);
-      return up;
+    async update(o: string, id: string, data: Row) {
+      const rows = rowsOf(o);
+      const at = rows.findIndex((r) => r.id === String(id));
+      if (at < 0) throw new Error(`not found ${o}/${id}`);
+      rows[at] = { ...rows[at], ...data, id: String(id) };
+      return rows[at];
+    },
+    async upsert(o: string, data: Row) { return this.create(o, data); },
+    async delete(o: string, id: string) {
+      const rows = rowsOf(o);
+      const at = rows.findIndex((r) => r.id === String(id));
+      if (at < 0) return false;
+      rows.splice(at, 1);
+      return true;
     },
-    async upsert(o: string, data: Record<string, unknown>) { return this.create(o, data); },
-    async delete(o: string, id: string) { return storeFor(o).delete(String(id)); },
     async bulkCreate() { return []; }, async bulkUpdate() { return []; }, async bulkDelete() {},
     async beginTransaction() { log.begun += 1; return { id: `trx_${log.begun}` }; },
     async commit() {}, async rollback() {},
   };
-  return { driver, stores, failReads, seed: (o: string, row: Record<string, unknown>) => storeFor(o).set(String(row.id), row) };
+  return {
+    driver,
+    failReads,
+    has: (o: string, id: string) => rowsOf(o).some((r) => r.id === id),
+    seed: (o: string, row: Row) => void rowsOf(o).push(row),
+  };
 }
 
 /** The deleted object. Its own injected anchor makes it self-referencing, harmlessly. */
@@ -202,7 +207,7 @@ describe('[#21910] the cascade scan skips a federated object\'s injected tenant
     log.reads.length = 0;
     await engine.delete('sys_organization', { where: { id: ORG_ID } } as any);
 
-    expect(local.stores.get('sys_organization')?.has(ORG_ID)).toBe(false);
+    expect(local.has('sys_organization', ORG_ID)).toBe(false);
     expect(log.reads).not.toContain('ext_customer');
     // CONTROL: the scan ran for this delete, and probed the local object's injected anchor.
     expect(log.reads).toContain('acct');
@@ -222,7 +227,7 @@ describe('[#21910] the cascade scan skips a federated object\'s injected tenant
     expect(err.code).toBe('INVALID_FILTER');
     expect(err.status).toBe(400);
     expect(log.reads).toContain('ext_tenant_customer');
-    expect(local.stores.get('sys_organization')?.has(ORG_ID)).toBe(true);
+    expect(local.has('sys_organization', ORG_ID)).toBe(true);
   });
 
   it('still probes any other lookup the author declared on a federated object, and its failure propagates (#8895)', async () => {
@@ -237,7 +242,7 @@ describe('[#21910] the cascade scan skips a federated object\'s injected tenant
     expect(err.code).toBe('INVALID_FILTER');
     expect(err.status).toBe(400);
     expect(log.reads).toContain('ext_order');
-    expect(local.stores.get('sys_organization')?.has(ORG_ID)).toBe(true);
+    expect(local.has('sys_organization', ORG_ID)).toBe(true);
   });
 });
 
@@ -247,7 +252,7 @@ describe('[#21910] the cascade atomicity plan agrees with the scan about who tak
 
     await engine.delete('sys_organization', { where: { id: ORG_ID } } as any);
 
-    expect(local.stores.get('sys_organization')?.has(ORG_ID)).toBe(false);
+    expect(local.has('sys_organization', ORG_ID)).toBe(false);
     expect(log.begun).toBe(1);
     expect(warnings.filter((w) => w.includes(NOT_ATOMIC))).toEqual([]);
   });
@@ -257,7 +262,7 @@ describe('[#21910] the cascade atomicity plan agrees with the scan about who tak
 
     await engine.delete('sys_organization', { where: { id: ORG_ID } } as any);
 
-    expect(local.stores.get('sys_organization')?.has(ORG_ID)).toBe(false);
+    expect(local.has('sys_organization', ORG_ID)).toBe(false);
     expect(log.reads).toContain('ext_order');
     expect(log.begun).toBe(0);
     expect(warnings.filter((w) => w.includes(NOT_ATOMIC))).toHaveLength(1);