@@ -0,0 +1,11 @@
+---
+"@objectstack/plugin-audit": patch
+"@objectstack/cli": patch
+---
+
+fix: an activity row is written only when an organization is derivable, never with a NULL organization, and the v18 ownership ceremony deletes the existing NULL activity rows it cannot attribute (ADR-0131 D9)
+
+Clause-②: no
+
+- **`@objectstack/plugin-audit`.** The audit writer's activity mirror (`sys_activity`) takes its organization from the record, then from the acting session, then from the `tenancy` service's Default Organization under `single`. When none of them names one, the mirror now writes no activity row at all. Before, it wrote a row with `organization_id` NULL. Under a wall that row was readable by no organization member. The change is still recorded: the compliance ledger row (`sys_audit_log`) is written as before, with its `tenant_id` attribution. Under `single` the Default Organization is always derivable, so nothing changes there. A record that names its organization keeps its activity row, with that organization.
+- **`@objectstack/cli`.** `os migrate organization-ownership` still attributes a NULL `sys_activity` row when its record carries an organization. On a walled database (any posture but `single`), the mirror-deletion step now deletes the NULL rows no anchor attributes, such as activity about a sign-up's `sys_user`. Before, those rows were reported as unattributable and held certification. They are 14-day telemetry that the mirror no longer writes, and `sys_audit_log` keeps each change. The plan counts them as the departure `underivable-activity`, and warns before the first write that `--apply` deletes them. The apply report lists the count as the table's `deleted`. Under `single` the Default Organization takes these rows, as before, and nothing is deleted.
@@ -28,6 +28,7 @@ import {
   predicateSql,
   PRIMARY_DATABASE,
   Sql,
+  underivableDepartureOf,
   type AttributionSink,
   type MetadataConflict,
   type MetadataKeyRow,
@@ -117,7 +118,11 @@ import type { DeclaredSharingRuleSkip } from '@objectstack/plugin-sharing';
  *     C3 stage 9): every grant naming a mirror row is renamed to the rule's
  *     NAME, which the registry must resolve, and only then is the mirror
  *     deleted ({@link runDeclaredRuleMirrorDeletion}). It runs again on a
- *     checkpointed run while a mirror stands.
+ *     checkpointed run while a mirror stands. Before them, a fate-3 table's
+ *     `underivableDeparture` (`sys_activity`, ruling record 6257510973 item
+ *     3): the NULL rows no anchor attributes once attribution is done are
+ *     deleted — never under `single`, where the Default Organization takes
+ *     them ({@link runUnderivableDeletion}).
  *  4h. `history-renumber` — seat answer Q2 A: `sys_metadata_history`'s
  *     `event_seq` and every `(type, name, version)` unique environment-wide
  *     before the column goes. Every lineage still tagged to an organization
@@ -184,7 +189,7 @@ import type { DeclaredSharingRuleSkip } from '@objectstack/plugin-sharing';
  *
  * ## What it never does
  *
- * ⛔ Delete a row outside fate 2. ⛔ Give an unattributable row an owner:
+ * ⛔ Delete a row outside fate 2 and a declared `underivableDeparture`. ⛔ Give an unattributable row an owner:
  * owners come only from the plan's anchors and, under `single`, the Default
  * Organization. ⛔ Create any organization but the Default Organization, and
  * that one only under `single` on a database that holds none. ⛔ Run at boot:
@@ -2526,6 +2531,11 @@ async function runMirrorDeletion(run: Run): Promise<StepReport> {
     const kept = Math.max(0, table.rows!.total - (run.deleted.get(table.object) ?? 0));
     if (kept > 0) notes.push(`${table.object}: ${kept} row(s) are not mirrors (a named category or their non-seeded provenance claims them) and stay.`);
   }
+  const underivable = await runUnderivableDeletion(run);
+  total += underivable.deleted;
+  if (underivable.blockers.length) {
+    return { step: 'mirror-deletion', status: 'blocked', summary: { deleted: total }, blockers: underivable.blockers, notes };
+  }
   const declared = await runDeclaredRuleMirrorDeletion(run);
   if (declared.status !== 'done') return { ...declared, summary: { ...declared.summary, deleted: total }, notes: [...notes, ...declared.notes] };
   return {
@@ -2537,6 +2547,65 @@ async function runMirrorDeletion(run: Run): Promise<StepReport> {
   };
 }
 
+// ── Step 4, continued: the rows no anchor attributes (ruling record 6257510973 item 3) ─
+
+/**
+ * The NULL rows of a fate-3 table that declares an `underivableDeparture`
+ * (`sys_activity`: activity is never a NULL row, and the existing ones are
+ * deleted): once attribution has written every owner it derives, every row
+ * still NULL is one of them. Read from a fresh plan, so the delete takes
+ * exactly what that plan classifies: a table on which it still derives an
+ * owner, or reports a row, blocks with nothing deleted. Never under `single`
+ * ({@link underivableDepartureOf}).
+ */
+/** Whether the plan this run started from counts a row an `underivableDeparture` deletes. */
+function underivableRowsDue(run: Run): boolean {
+  return run.plan.tables.some((t) => {
+    const entry = mirrorEntry(run, t.object);
+    const id = entry ? underivableDepartureOf(entry, run.opts.posture)?.id : undefined;
+    return id !== undefined && t.departures.some((d) => d.id === id && d.rows > 0);
+  });
+}
+
+async function runUnderivableDeletion(run: Run): Promise<{ deleted: number; blockers: string[] }> {
+  const declares = (object: string): string | undefined => {
+    const entry = mirrorEntry(run, object);
+    return entry ? underivableDepartureOf(entry, run.opts.posture)?.id : undefined;
+  };
+  if (!run.plan.tables.some((t) => t.physical === 'present' && declares(t.object))) return { deleted: 0, blockers: [] };
+  const plan = await planFor(run);
+  let deleted = 0;
+  const blockers: string[] = [];
+  for (const table of plan.tables) {
+    const id = declares(table.object);
+    const leaving = id ? table.departures.find((d) => d.id === id) : undefined;
+    if (!leaving || leaving.rows === 0 || table.physical !== 'present') continue;
+    const deriving = Number(table.fateCounts.rowsToAttribute ?? 0);
+    if (deriving > 0 || table.unattributable.length > 0 || leaving.rows !== table.rows!.organizationNull) {
+      blockers.push(
+        `${table.object}: ${leaving.rows} row(s) no anchor attributes are due for deletion, but the table still holds ` +
+          `${table.rows!.organizationNull} NULL row(s) (${deriving} an anchor attributes, ${table.unattributable.length} ` +
+          'reported), so nothing was deleted. Re-run --apply: the attribution step runs again first.',
+      );
+      continue;
+    }
+    for (const physical of table.tables) {
+      const { sql } = databaseFor(run, physical);
+      const where = `${sql.q(ORG, physical)} IS NULL`;
+      const count = (): Promise<number> => sql.count(physical, `SELECT COUNT(*) AS n FROM ${sql.q(physical, physical)} WHERE ${where}`);
+      const before = await count();
+      if (before === 0) continue;
+      await execute(run, physical, `DELETE FROM ${sql.q(physical, physical)} WHERE ${where}`, []);
+      const left = await count();
+      if (left !== 0) throw new Error(`The delete on ${physical} left ${left} organization-less row(s) behind; nothing past this table was deleted.`);
+      run.deleted.set(table.object, (run.deleted.get(table.object) ?? 0) + before);
+      deleted += before;
+      run.opts.onProgress?.(`mirror deletion: ${before} organization-less row(s) of ${physical} no anchor attributes`);
+    }
+  }
+  return { deleted, blockers };
+}
+
 // ── Step 4, continued: the declared sharing-rule mirrors (ADR-0131 C3 stage 9) ─
 
 const SHARING_RULES = 'sys_sharing_rule';
@@ -3097,6 +3166,23 @@ export async function applyOrganizationOwnership(opts: ApplyOptions): Promise<Or
     // checkpointed run while one stands: a database whose ceremony completed on
     // a release whose boot still seeded them carries them (advisory then), and
     // the step that deletes them is this release's.
+    // So are the rows no anchor attributes, while one stands: a row written
+    // NULL since the run that finished the step is one too.
+    if (done && step === 'mirror-deletion' && underivableRowsDue(run)) {
+      const again = await runUnderivableDeletion(run);
+      const report: StepReport = again.blockers.length
+        ? { step, status: 'blocked', summary: { deleted: again.deleted }, blockers: again.blockers, notes: [] }
+        : { step, status: 'done', summary: { deleted: again.deleted }, blockers: [], notes: [] };
+      steps.push(report);
+      if (report.status !== 'done') {
+        stopped = true;
+        continue;
+      }
+      checkpoint.completed[step] = { at: now().toISOString(), summary: report.summary };
+      await opts.ledger.write(checkpoint, { complete: false, blocking: 0, advisory: 0 });
+      run.columns.clear();
+      if (!(await declaredRuleMirrorsDue(run))) continue;
+    }
     if (done && step === 'mirror-deletion' && (await declaredRuleMirrorsDue(run))) {
       const again = await runDeclaredRuleMirrorDeletion(run);
       steps.push(again);
 
@@ -0,0 +1,198 @@
+// Copyright (c) 2026 ObjectStack. Licensed under the Apache-2.0 license.
+
+/**
+ * The ADR-0131 D10 `--apply` on `sys_activity`'s organization-less rows
+ * (ruling record 6257510973 item 3, Q3 A): activity is written only when an
+ * organization is derivable, never as a NULL row, and the ceremony deletes the
+ * existing NULL rows no anchor attributes — 14-day telemetry, whose change the
+ * deployment ledger (`sys_audit_log`, D7) keeps.
+ *
+ * The fixture is a sign-up's measured shape: activity about a `sys_user` (an
+ * object with no organization column) written NULL, beside a NULL activity
+ * row about an organization's record and an activity row already stamped.
+ *
+ *  - Walled (`isolated`): the row about the organization's record takes its
+ *    organization from the subject anchor; the two about the user, which no
+ *    anchor attributes, are deleted by the mirror-deletion step; the stamped
+ *    row is untouched. The plan says so before the first write, and the
+ *    verdict certifies with nothing remaining.
+ *  - `single`: the Default Organization takes the user's rows, as a
+ *    single-posture boot gives it every row it writes; nothing is deleted.
+ */
+
+import { afterEach, beforeEach, describe, expect, it } from 'vitest';
+import Database from 'better-sqlite3';
+import { mkdtempSync, rmSync } from 'node:fs';
+import { tmpdir } from 'node:os';
+import { join } from 'node:path';
+import { buildOrganizationOwnershipPlan, inventoryDigest, type OrganizationOwnershipPlan } from './organization-ownership-plan.js';
+import {
+  applyOrganizationOwnership,
+  reviewedConflictsOf,
+  type ApplyExecutor,
+  type CeremonyCheckpoint,
+  type CeremonyLedgerPort,
+  type ColumnDropPort,
+  type OrganizationOwnershipApplyReport,
+} from './organization-ownership-apply.js';
+
+let dir: string;
+let db: Database.Database;
+/** Every write statement the ceremony issued, in order. */
+let writes: string[];
+
+function executor(): ApplyExecutor {
+  return {
+    dialect: 'sqlite',
+    client: 'better-sqlite3',
+    async query(sql, params = []) {
+      return db.prepare(sql).all(...(params as unknown[])) as Record<string, unknown>[];
+    },
+    async execute(sql, params = []) {
+      writes.push(sql);
+      db.prepare(sql).run(...(params as unknown[]));
+    },
+  };
+}
+
+const columnDrops: ColumnDropPort = {
+  async drop(columns) {
+    return columns.map(({ table, column }) => {
+      db.exec(`ALTER TABLE "${table}" DROP COLUMN "${column}"`);
+      return { table, column, outcome: 'dropped' as const };
+    });
+  },
+};
+
+function ledger(): CeremonyLedgerPort {
+  let stored: CeremonyCheckpoint | null = null;
+  return {
+    async read() {
+      return stored ? (JSON.parse(JSON.stringify(stored)) as CeremonyCheckpoint) : null;
+    },
+    async write(checkpoint) {
+      stored = JSON.parse(JSON.stringify(checkpoint)) as CeremonyCheckpoint;
+    },
+  };
+}
+
+const database = (): string => join(dir, 'fixture.db');
+
+const plan = (posture: string): Promise<OrganizationOwnershipPlan> =>
+  buildOrganizationOwnershipPlan({ reader: executor(), posture, database: database() });
+
+/** Plan, then apply that reviewed plan, as the command does. */
+async function apply(posture: string, l = ledger()): Promise<OrganizationOwnershipApplyReport> {
+  const reviewed = await plan(posture);
+  return applyOrganizationOwnership({
+    executor: executor(),
+    posture,
+    database: database(),
+    reviewedPlan: {
+      file: 'plan.json',
+      generatedAt: reviewed.generatedAt,
+      database: database(),
+      inventoryDigest: inventoryDigest(),
+      posture,
+      conflicts: reviewedConflictsOf(reviewed),
+    },
+    catalog: { async resolve() { return undefined; } },
+    door: {
+      async save(type, name) {
+        throw new Error(`no environment save is expected here (${type} ${name})`);
+      },
+    },
+    templates: { async find() { return undefined; } },
+    views: { async list() { return []; } },
+    lock: { async verdict() { return { editable: true }; } },
+    columnDrops,
+    ledger: l,
+    now: () => new Date('2026-10-19T00:00:00Z'),
+  });
+}
+
+const activity = (): Record<string, unknown>[] =>
+  db.prepare(`SELECT id, organization_id FROM sys_activity ORDER BY id`).all() as Record<string, unknown>[];
+
+beforeEach(() => {
+  dir = mkdtempSync(join(tmpdir(), 'os-d10-underivable-activity-'));
+  db = new Database(database());
+  writes = [];
+  db.exec(`
+    CREATE TABLE sys_organization (id TEXT PRIMARY KEY, slug TEXT);
+    INSERT INTO sys_organization VALUES ('org_default', 'default'), ('org_a', 'acme');
+    CREATE TABLE sys_user (id TEXT PRIMARY KEY, name TEXT, email TEXT);
+    INSERT INTO sys_user VALUES ('usr_1', 'Ada', 'ada@example.com');
+    CREATE TABLE crm_deal (id TEXT PRIMARY KEY, organization_id TEXT, name TEXT);
+    INSERT INTO crm_deal VALUES ('deal_1', 'org_a', 'Acme renewal');
+    CREATE TABLE sys_activity (id TEXT PRIMARY KEY, organization_id TEXT, type TEXT, object_name TEXT, record_id TEXT);
+    INSERT INTO sys_activity VALUES
+      ('act_deal_null', NULL, 'created', 'crm_deal', 'deal_1'),
+      ('act_deal_stamped', 'org_a', 'updated', 'crm_deal', 'deal_1'),
+      ('act_user_created', NULL, 'created', 'sys_user', 'usr_1'),
+      ('act_user_updated', NULL, 'updated', 'sys_user', 'usr_1');
+  `);
+});
+
+afterEach(() => {
+  db.close();
+  rmSync(dir, { recursive: true, force: true });
+});
+
+describe('sys_activity rows no organization is derivable for (ruling record 6257510973 item 3)', () => {
+  it('walled: the plan counts the two underivable rows as departing, says so before the first write, and reports none', async () => {
+    const reviewed = await plan('isolated');
+    const table = reviewed.tables.find((t) => t.object === 'sys_activity')!;
+    expect(table.fateCounts).toMatchObject({ rowsToAttribute: 1, departingRows: 2, unattributableRows: 0 });
+    expect(table.departures).toEqual([expect.objectContaining({ id: 'underivable-activity', as: 'mirror-deletion', rows: 2 })]);
+    expect(table.unattributable).toEqual([]);
+    expect(table.notNull.willReceive).toBe(true);
+    expect(reviewed.warnings).toEqual([expect.stringMatching(/^sys_activity holds 2 organization-less row\(s\) no anchor attributes: .*--apply deletes them/)]);
+  });
+
+  it('walled: the anchored row takes its organization, the two about the user are deleted, the stamped row stays; nothing remains', async () => {
+    const report = await apply('isolated');
+
+    expect([report.complete, report.blocking]).toEqual([true, 0]);
+    const table = report.tables.find((t) => t.object === 'sys_activity')!;
+    expect(table).toMatchObject({ attributed: 1, deleted: 2, remaining: 0, unattributable: [], departures: [] });
+    expect(table.after).toEqual({ total: 2, organizationNull: 0 });
+    expect(activity()).toEqual([
+      { id: 'act_deal_null', organization_id: 'org_a' },
+      { id: 'act_deal_stamped', organization_id: 'org_a' },
+    ]);
+    // Deleted after attribution, by the mirror-deletion step, NULL rows only.
+    const deletes = writes.filter((w) => /^DELETE FROM "sys_activity"/i.test(w));
+    expect(deletes).toEqual(['DELETE FROM "sys_activity" WHERE "organization_id" IS NULL']);
+    expect(writes.findIndex((w) => /^UPDATE "sys_activity"/i.test(w))).toBeLessThan(writes.indexOf(deletes[0]!));
+    expect(report.steps.find((s) => s.step === 'mirror-deletion')).toMatchObject({ status: 'done', summary: { deleted: 2 } });
+  });
+
+  it('walled: a second run finds nothing to delete and writes nothing to the table', async () => {
+    const l = ledger();
+    await apply('isolated', l);
+    writes = [];
+    const again = await apply('isolated', l);
+    expect([again.complete, again.blocking]).toEqual([true, 0]);
+    expect(writes.filter((w) => /sys_activity/.test(w))).toEqual([]);
+  });
+
+  it('single: the Default Organization takes the user\'s rows, and nothing is deleted', async () => {
+    const reviewed = await plan('single');
+    const table = reviewed.tables.find((t) => t.object === 'sys_activity')!;
+    expect(table.departures).toEqual([]);
+    expect(table.attribution).toMatchObject({ 'default-organization': 2 });
+    expect(reviewed.warnings).toEqual([]);
+
+    const report = await apply('single');
+    expect([report.complete, report.blocking]).toEqual([true, 0]);
+    expect(report.tables.find((t) => t.object === 'sys_activity')).toMatchObject({ attributed: 3, deleted: 0, remaining: 0 });
+    expect(activity()).toEqual([
+      { id: 'act_deal_null', organization_id: 'org_a' },
+      { id: 'act_deal_stamped', organization_id: 'org_a' },
+      { id: 'act_user_created', organization_id: 'org_default' },
+      { id: 'act_user_updated', organization_id: 'org_default' },
+    ]);
+    expect(writes.filter((w) => /^DELETE FROM "sys_activity"/i.test(w))).toEqual([]);
+  });
+});
@@ -204,7 +204,7 @@ describe('ADR-0131 D10 inventory — every censused object has one fate and a ci
  * platform states. Compile-time: both directions of `extends` must hold, so a
  * key added to either side without the other fails `tsc` on this file.
  */
-type HostAuthoredKeys = Exclude<keyof InventoryEntry, 'census' | 'cloudCarried' | 'external'>;
+type HostAuthoredKeys = Exclude<keyof InventoryEntry, 'census' | 'cloudCarried' | 'external' | 'underivableDeparture'>;
 type SpecRowKeys = OrganizationOwnershipSupplementEntry extends infer Row ? (Row extends unknown ? keyof Row : never) : never;
 const KEYS_AGREE: [HostAuthoredKeys] extends [SpecRowKeys] ? ([SpecRowKeys] extends [HostAuthoredKeys] ? true : false) : false = true;
 
@@ -244,7 +244,7 @@ describe('the inventory row and the spec\'s supplement row are one shape', () =>
     // anchor, category and departure form) is declared in the spec: a host can
     // author anything the platform's own rows say.
     const refused: string[] = [];
-    for (const { census: _census, cloudCarried: _cloud, external: _external, ...row } of ORGANIZATION_OWNERSHIP_INVENTORY) {
+    for (const { census: _census, cloudCarried: _cloud, external: _external, underivableDeparture: _underivable, ...row } of ORGANIZATION_OWNERSHIP_INVENTORY) {
       const result = OrganizationOwnershipSupplementEntrySchema.safeParse(row);
       if (!result.success) refused.push(`${row.object}: ${result.error.issues[0]?.message}`);
     }