diff --git a/lib/services/remediation-service.test.ts b/lib/services/remediation-service.test.ts
index aa62da6..ad41e12 100644
--- a/lib/services/remediation-service.test.ts
+++ b/lib/services/remediation-service.test.ts
@@ -15,6 +15,11 @@ vi.mock('./phishing-audit', () => ({
   writeAuditEvent: (...args: unknown[]) => writeAuditEventMock(...args),
 }));
 
+const generateAndPostAcknowledgmentMock = vi.fn();
+vi.mock('./triage-note-service', () => ({
+  generateAndPostAcknowledgment: (...args: unknown[]) => generateAndPostAcknowledgmentMock(...args),
+}));
+
 // eslint-disable-next-line import/first -- imported after vi.mock hoisting
 import {
   approveRemediationActions,
@@ -82,6 +87,8 @@ beforeEach(() => {
   transactionMock.mockReset();
   writeAuditEventMock.mockReset();
   writeAuditEventMock.mockResolvedValue('audit-id');
+  generateAndPostAcknowledgmentMock.mockReset();
+  generateAndPostAcknowledgmentMock.mockResolvedValue({ noteText: 'thanks', tickets: [] });
   clientCalls = [];
 });
 
@@ -208,6 +215,51 @@ describe('remediateApprovedActions', () => {
     );
     expect(writeAuditEventMock).not.toHaveBeenCalled();
   });
+
+  it('calls generateAndPostAcknowledgment exactly once with the campaignId when an approved acknowledge_user row is remediated', async () => {
+    stage({
+      remediationRows: [{ id: 'action-1', action_type: 'acknowledge_user', status: 'approved' }],
+    });
+
+    await remediateApprovedActions('campaign-1', 'operator@example.com');
+
+    expect(generateAndPostAcknowledgmentMock).toHaveBeenCalledTimes(1);
+    expect(generateAndPostAcknowledgmentMock).toHaveBeenCalledWith('campaign-1');
+  });
+
+  it('does NOT call generateAndPostAcknowledgment for a block_sender/warn_user-only remediation', async () => {
+    stage({
+      remediationRows: [
+        { id: 'action-1', action_type: 'block_sender', status: 'approved' },
+        { id: 'action-2', action_type: 'warn_user', status: 'approved' },
+      ],
+    });
+
+    await remediateApprovedActions('campaign-1', 'operator@example.com');
+
+    expect(generateAndPostAcknowledgmentMock).not.toHaveBeenCalled();
+  });
+
+  it('does NOT call generateAndPostAcknowledgment when the acknowledge_user row staged is already completed (idempotent re-run)', async () => {
+    stage({
+      remediationRows: [{ id: 'action-1', action_type: 'acknowledge_user', status: 'completed' }],
+    });
+
+    await remediateApprovedActions('campaign-1', 'operator@example.com');
+
+    expect(generateAndPostAcknowledgmentMock).not.toHaveBeenCalled();
+  });
+
+  it('does not propagate a generateAndPostAcknowledgment rejection out of remediateApprovedActions (already-committed transition)', async () => {
+    stage({
+      remediationRows: [{ id: 'action-1', action_type: 'acknowledge_user', status: 'approved' }],
+    });
+    generateAndPostAcknowledgmentMock.mockRejectedValueOnce(new Error('Autotask unavailable'));
+
+    const result = await remediateApprovedActions('campaign-1', 'operator@example.com');
+
+    expect(result.actions[0]).toMatchObject({ actionType: 'acknowledge_user', status: 'completed' });
+  });
 });
 
 // =============================================================================
diff --git a/lib/services/remediation-service.ts b/lib/services/remediation-service.ts
index d3c2682..6ff9fa1 100644
--- a/lib/services/remediation-service.ts
+++ b/lib/services/remediation-service.ts
@@ -13,13 +13,22 @@
  * D-01: this file never has an unimplemented/no-op code path for the
  * remediate step. Its "external effect" is a simulated internal transition
  * (status='approved' -> 'completed') — no real provider call for any of the
- * 7 action types this milestone. The only explicit-failure branch is the
+ * 7 original action types. The only explicit-failure branch is the
  * zero-approved-actions case (REMED-03) — remediating with nothing approved
  * always throws, never silently no-ops as a success.
+ *
+ * Phase 23 carve-out (D-04): the ONE exception is the post-commit
+ * `acknowledge_user` customer-note post below — a non-destructive thank-you
+ * message, not a security action. It runs AFTER the transaction commits
+ * (never inside it — the Autotask write is network I/O and must not hold a
+ * DB transaction open or risk a post-then-rollback), and its failure is
+ * caught/logged, never propagated (the DB transition already succeeded).
+ * Every other action type remains a simulated status-only transition.
  */
 
 import { postgresClient } from './postgres-client';
 import { writeAuditEvent } from './phishing-audit';
+import { generateAndPostAcknowledgment } from './triage-note-service';
 
 export class RemediationValidationError extends Error {
   constructor(message: string) {
@@ -171,7 +180,7 @@ export interface RemediateResult {
  * success for "nothing to do".
  */
 export async function remediateApprovedActions(campaignId: string, actor: string | null): Promise<RemediateResult> {
-  return postgresClient.transaction(async (client) => {
+  const result = await postgresClient.transaction(async (client) => {
     const rowsRes = await client.query<RemediationActionRow>(
       `SELECT id::text, action_type, status FROM remediation_actions WHERE campaign_id = $1 FOR UPDATE`,
       [campaignId]
@@ -204,6 +213,26 @@ export async function remediateApprovedActions(campaignId: string, actor: string
 
     return { campaignId, actions };
   });
+
+  // Phase 23 D-04 carve-out: post the real customer-visible acknowledgment
+  // note AFTER the transaction has committed — only when an approved
+  // acknowledge_user row was actually transitioned this pass (never on the
+  // already-completed idempotent re-run). Never held inside the DB
+  // transaction (network I/O), and never allowed to propagate (the DB
+  // transition already succeeded; generateAndPostAcknowledgment already
+  // isolates per-ticket failures internally).
+  const shouldPostAcknowledgment = result.actions.some(
+    (action) => action.actionType === 'acknowledge_user' && action.alreadyCompleted === false
+  );
+  if (shouldPostAcknowledgment) {
+    try {
+      await generateAndPostAcknowledgment(campaignId);
+    } catch (err) {
+      console.error('[REMEDIATE] acknowledge_user note post failed', campaignId, err);
+    }
+  }
+
+  return result;
 }
 
 // =============================================================================