@@ -0,0 +1,30 @@
+---
+'@objectstack/plugin-audit': patch
+---
+
+`sys_activity.actor_name` is written: a user's create, update or delete records that user's display name on its activity row, so the record History tab names who acted instead of "Unknown user"
+
+Clause-②: no
+
+`sys_activity` declares `actor_name` and lists it among its highlight fields, because activity
+entries are denormalized snapshots read in time order. The audit writer filled `actor_id` and never
+`actor_name`, so every row carried the user's id and no name. A renderer that reads the name, such
+as the record History tab, showed "Unknown user" for every entry, for every user.
+
+The writer now records the name when it writes the row. The name is the title of the user's
+`sys_user` row (its `name` column), read once per user and kept for 30 seconds. A predicate write
+over many rows costs one `sys_user` read for its actor, not one per row.
+
+- **A user write.** `actor_name` is the user's display name. `actor_id` is unchanged, and the name
+  is read for that same id. This includes a write the system authorized on behalf of a credited
+  user (`attributedUserId`).
+- **A user whose name cannot be read** (no row, or a blank name). `actor_name` stays empty. The
+  writer never puts the id in it.
+- **A write with no user** (boot, migration, a scheduled job, a flow running as the system).
+  `actor_name` stays empty, as before. Per ADR-0118 D1 the system actor is `null`, and the UI
+  renders the "System" label for it.
+- **An object with `enable.activities: false`.** No activity row is written and no name is read,
+  as before.
+
+Rows written before this change keep `actor_id` and no name. This change does not backfill them.
+Nothing you author changes: no key, option, export or type is added or removed.
@@ -0,0 +1,280 @@
+// Copyright (c) 2026 ObjectStack. Licensed under the Apache-2.0 license.
+
+/**
+ * [#22510] `sys_activity.actor_name` is WRITTEN — the acting user's display
+ * name, captured when the activity row is written.
+ *
+ * `sys_activity` declares the column (and lists it among its highlight
+ * fields) because its entries are "denormalized snapshots" read
+ * chronologically. No writer filled it: every row carried `actor_id` and a
+ * null `actor_name`, and the record History tab — which reads `actor_name` —
+ * showed "Unknown user" for every entry, for every user.
+ *
+ * Pinned through the REAL engine (`ObjectQL`), so the user travels the way it
+ * does in production — `ExecutionContext.userId` → the hook session — rather
+ * than as a hand-built hook context:
+ *
+ *  1. a user's write names that user, on create, update and delete alike;
+ *  2. `actor_id` is unchanged, and is the id the name was read for (control);
+ *  3. a user whose name cannot be read leaves `actor_name` empty — never the
+ *     id, which would read as a plausible name;
+ *  4. a write with no user leaves it empty too: ADR-0118 D1 keeps the system
+ *     actor `null`, and its "System" label is a rendering rule, not data;
+ *  5. the read is one per user, not one per row — `writeAudit` runs once per
+ *     row of a predicate write, and this is its hot path.
+ */
+
+import { describe, it, expect } from 'vitest';
+import { ObjectQL } from '@objectstack/objectql';
+import { installAuditWriters } from './audit-writers.js';
+
+const f = (name: string, type: string, extra: Record<string, unknown> = {}) =>
+  ({ name, label: name, type, ...extra }) as any;
+
+const sysAuditLog = {
+  name: 'sys_audit_log', label: 'Audit Log',
+  fields: {
+    id: f('id', 'text', { primaryKey: true }), action: f('action', 'text'),
+    user_id: f('user_id', 'text'), object_name: f('object_name', 'text'),
+    record_id: f('record_id', 'text'), old_value: f('old_value', 'textarea'),
+    new_value: f('new_value', 'textarea'), tenant_id: f('tenant_id', 'text'),
+  },
+};
+
+/** The two actor columns the shipped `sys_activity` declares, both present. */
+const sysActivity = {
+  name: 'sys_activity', label: 'Activity',
+  fields: {
+    id: f('id', 'text', { primaryKey: true }), type: f('type', 'text'),
+    timestamp: f('timestamp', 'datetime'), summary: f('summary', 'text'),
+    actor_id: f('actor_id', 'text'), actor_name: f('actor_name', 'text'),
+    object_name: f('object_name', 'text'), record_id: f('record_id', 'text'),
+    record_label: f('record_label', 'text'), metadata: f('metadata', 'textarea'),
+  },
+};
+
+/** `nameField: 'name'`, as the shipped `sys_user` declares it. */
+const sysUser = {
+  name: 'sys_user', label: 'User', nameField: 'name',
+  fields: {
+    id: f('id', 'text', { primaryKey: true }), name: f('name', 'text'),
+    email: f('email', 'email'),
+  },
+};
+
+const bizTask = {
+  name: 'biz_task', label: 'Task',
+  fields: { id: f('id', 'text', { primaryKey: true }), title: f('title', 'text'), status: f('status', 'text') },
+};
+
+/** `enable.activities: false` — this object's writes produce no activity row. */
+const bizQuiet = {
+  name: 'biz_quiet', label: 'Quiet', enable: { activities: false },
+  fields: { id: f('id', 'text', { primaryKey: true }), title: f('title', 'text') },
+};
+
+/** Copy-returning, read-counting store — the shape `audit-lookup-summary.test.ts` measures with. */
+function makeCountingDriver() {
+  const stores = new Map<string, Map<string, Record<string, unknown>>>();
+  const reads: Record<string, number> = {};
+  const storeFor = (o: string) => {
+    let s = stores.get(o);
+    if (!s) { s = new Map(); stores.set(o, s); }
+    return s;
+  };
+  let nextId = 0;
+  const copy = <T,>(r: T): T => (r == null ? r : JSON.parse(JSON.stringify(r)));
+  const matches = (row: Record<string, unknown>, where: any): boolean => {
+    if (!where || typeof where !== 'object') return true;
+    for (const [k, v] of Object.entries<any>(where)) {
+      if (k === '$and' && Array.isArray(v)) {
+        if (!v.every((sub) => matches(row, sub))) return false;
+        continue;
+      }
+      if (k.startsWith('$')) continue;
+      if (v && typeof v === 'object' && '$in' in v) {
+        if (!(v.$in as unknown[]).includes(row[k])) return false;
+        continue;
+      }
+      const expected = (v && typeof v === 'object' && '$eq' in v) ? v.$eq : v;
+      if ((row[k] ?? null) !== (expected ?? null)) return false;
+    }
+    return true;
+  };
+  const driver: any = {
+    name: 'memory', version: '0.0.0', supports: {} as any,
+    async connect() {}, async disconnect() {}, async checkHealth() { return true; },
+    async execute() { return null; },
+    async find(object: string, ast: any) {
+      reads[object] = (reads[object] ?? 0) + 1;
+      return Array.from(storeFor(object).values()).filter((r) => matches(r, ast?.where)).map(copy);
+    },
+    async findOne(object: string, ast: any) {
+      for (const r of storeFor(object).values()) if (matches(r, ast?.where)) return copy(r);
+      return null;
+    },
+    async create(object: string, data: Record<string, unknown>) {
+      nextId += 1;
+      const id = (data.id as string) ?? `r_${nextId}`;
+      const row = { ...data, id };
+      storeFor(object).set(id, row);
+      return copy(row);
+    },
+    async update(object: string, id: string, data: Record<string, unknown>) {
+      const s = storeFor(object);
+      const cur = s.get(id);
+      if (!cur) return null;
+      const updated = { ...cur, ...data, id };
+      s.set(id, updated);
+      return copy(updated);
+    },
+    async upsert(object: string, data: Record<string, unknown>) {
+      const id = data.id as string | undefined;
+      return id && storeFor(object).has(id) ? this.update(object, id, data) : this.create(object, data);
+    },
+    async delete(object: string, id: string) { return storeFor(object).delete(id); },
+    async count(object: string, ast: any) { return (await this.find(object, ast)).length; },
+    async bulkCreate(object: string, rows: Record<string, unknown>[]) {
+      return Promise.all(rows.map((r) => this.create(object, r)));
+    },
+    async bulkUpdate() { return []; },
+    async bulkDelete() {},
+    async updateMany(object: string, ast: any, data: Record<string, unknown>) {
+      const rows = await this.find(object, ast);
+      const s = storeFor(object);
+      for (const r of rows) s.set(r.id as string, { ...s.get(r.id as string), ...data, id: r.id });
+      return rows.length;
+    },
+    async deleteMany(object: string, ast: any) {
+      const rows = await this.find(object, ast);
+      for (const r of rows) storeFor(object).delete(r.id as string);
+      return rows.length;
+    },
+    async beginTransaction() { return { commit: async () => {}, rollback: async () => {} }; },
+    async commit() {}, async rollback() {},
+  };
+  return { driver, reads, storeFor };
+}
+
+const OWNER_PACKAGE = 'com.objectstack.test.activity-actor-name';
+const ADA = 'usr_ada';
+
+async function boot() {
+  const engine = new ObjectQL();
+  const stub = makeCountingDriver();
+  engine.registerDriver(stub.driver, true);
+  await engine.init();
+  for (const o of [sysAuditLog, sysActivity, sysUser, bizTask, bizQuiet]) {
+    engine.registry.registerObject(o as any, OWNER_PACKAGE);
+  }
+  installAuditWriters(engine as any, 'test.audit');
+  // Seeded with no context: a system write, which names nobody.
+  await engine.insert('sys_user', { id: ADA, name: 'Ada Lovelace', email: 'ada@example.com' });
+  return { engine, ...stub };
+}
+
+const as = (userId: string) => ({ context: { userId } });
+
+/** Every activity row written about `recordId`, in write order. */
+const activityFor = (storeFor: (o: string) => Map<string, Record<string, unknown>>, recordId: string) =>
+  Array.from(storeFor('sys_activity').values()).filter((r) => r.record_id === recordId);
+
+describe('[#22510] sys_activity.actor_name — the acting user\'s name, written with the row', () => {
+  it('a user\'s create, update and delete each carry that user\'s name', async () => {
+    const { engine, storeFor } = await boot();
+
+    await engine.insert('biz_task', { id: 't1', title: 'Call Acme', status: 'open' }, as(ADA) as any);
+    await engine.update('biz_task', { status: 'done' }, { where: { id: 't1' }, ...as(ADA) } as any);
+    await engine.delete('biz_task', { where: { id: 't1' }, ...as(ADA) } as any);
+
+    const rows = activityFor(storeFor, 't1');
+    expect(rows.map((r) => r.type)).toEqual(['created', 'updated', 'deleted']);
+    for (const row of rows) {
+      expect(row.actor_name).toBe('Ada Lovelace');
+      // Control: `actor_id` is exactly what it was — the same id the name was read for.
+      expect(row.actor_id).toBe(ADA);
+    }
+  });
+
+  it('names the human a system-authorized write is ATTRIBUTED to — the same id `actor_id` records', async () => {
+    const { engine, storeFor } = await boot();
+
+    // The better-auth envelope: authorized as the system, crediting a human
+    // through provenance (`attributedUserId`) rather than the session.
+    await engine.insert(
+      'biz_task',
+      { id: 't2', title: 'Grade change', status: 'open' },
+      { context: { isSystem: true, attributedUserId: ADA } } as any,
+    );
+
+    const [row] = activityFor(storeFor, 't2');
+    expect(row.actor_id).toBe(ADA);
+    expect(row.actor_name).toBe('Ada Lovelace');
+  });
+
+  it('a user whose name cannot be read leaves actor_name empty — never the id', async () => {
+    const { engine, storeFor } = await boot();
+    await engine.insert('sys_user', { id: 'usr_blank', name: '   ', email: 'blank@example.com' });
+
+    // No `sys_user` row at all, and a row whose name is blank.
+    await engine.insert('biz_task', { id: 't3', title: 'Ghost', status: 'open' }, as('usr_ghost') as any);
+    await engine.insert('biz_task', { id: 't4', title: 'Blank', status: 'open' }, as('usr_blank') as any);
+
+    const [ghost] = activityFor(storeFor, 't3');
+    const [blank] = activityFor(storeFor, 't4');
+    expect(ghost.actor_id).toBe('usr_ghost');
+    expect(ghost.actor_name ?? null).toBeNull();
+    expect(blank.actor_id).toBe('usr_blank');
+    expect(blank.actor_name ?? null).toBeNull();
+  });
+
+  it('a write with no user leaves actor_name empty (ADR-0118 D1: the system actor is null) and reads no user', async () => {
+    const { engine, storeFor, reads } = await boot();
+    const before = reads.sys_user ?? 0;
+
+    await engine.insert('biz_task', { id: 't5', title: 'Nightly', status: 'open' }, { context: { isSystem: true } } as any);
+    // A service principal on `actor` is not a user either (ADR-0118 D5: user or system).
+    await engine.insert(
+      'biz_task',
+      { id: 't6', title: 'Flow', status: 'open' },
+      { context: { isSystem: true, actor: 'svc:flow:nightly' } } as any,
+    );
+
+    for (const id of ['t5', 't6']) {
+      const [row] = activityFor(storeFor, id);
+      expect(row.actor_id).toBeNull();
+      expect(row.actor_name ?? null).toBeNull();
+    }
+    expect((reads.sys_user ?? 0) - before).toBe(0);
+  });
+});
+
+describe('[#22510] the name costs one read per user, not one per row', () => {
+  it('a predicate update over three rows reads sys_user ONCE, and a later write by the same user not at all', async () => {
+    const { engine, storeFor, reads } = await boot();
+    for (const id of ['p1', 'p2', 'p3']) {
+      await engine.insert('biz_task', { id, title: id, status: 'open' });
+    }
+    const before = reads.sys_user ?? 0;
+
+    await engine.update('biz_task', { status: 'done' }, { where: { status: 'open' }, multi: true, ...as(ADA) } as any);
+
+    const updated = Array.from(storeFor('sys_activity').values()).filter((r) => r.type === 'updated');
+    expect(updated).toHaveLength(3);
+    for (const row of updated) expect(row.actor_name).toBe('Ada Lovelace');
+    expect((reads.sys_user ?? 0) - before).toBe(1);
+
+    await engine.update('biz_task', { title: 'renamed' }, { where: { id: 'p1' }, ...as(ADA) } as any);
+    expect((reads.sys_user ?? 0) - before).toBe(1);
+  });
+
+  it('an object with `enable.activities: false` writes no activity row and reads no user', async () => {
+    const { engine, storeFor, reads } = await boot();
+    const before = reads.sys_user ?? 0;
+
+    await engine.insert('biz_quiet', { id: 'q1', title: 'Quiet' }, as(ADA) as any);
+
+    expect(activityFor(storeFor, 'q1')).toHaveLength(0);
+    expect((reads.sys_user ?? 0) - before).toBe(0);
+  });
+});