diff --git a/backend/__tests__/integration/workflowEngine.test.js b/backend/__tests__/integration/workflowEngine.test.js
index a038e62e..5440bf14 100644
--- a/backend/__tests__/integration/workflowEngine.test.js
+++ b/backend/__tests__/integration/workflowEngine.test.js
@@ -234,7 +234,7 @@ describe('workflow engine', () => {
     expect(again.already).toBe(true);
   });
 
-  test('seeds the invoice-dunning built-in flow (disabled, idempotent)', async () => {
+  test('seeds the invoice-dunning built-in as the delegation graph (v2, disabled)', async () => {
     const { seedBuiltinWorkflowsAtBoot, DUNNING_KEY } = require('../../src/services/_workflowSeedBoot');
     const noopLogger = { info() {}, warn() {} };
     await seedBuiltinWorkflowsAtBoot(db, noopLogger);
@@ -243,13 +243,39 @@ describe('workflow engine', () => {
     expect(wf).toBeTruthy();
     expect(!!wf.is_builtin).toBe(true);
     expect(!!wf.enabled).toBe(false);
+    expect(JSON.parse(wf.trigger_config).seedVersion).toBe(2);
 
-    const nodes = await db('workflow_nodes').where({ workflow_id: wf.id, version: 1 });
+    const nodes = await db('workflow_nodes').where({ workflow_id: wf.id, version: wf.version });
     expect(nodes.filter((n) => n.type === 'trigger')).toHaveLength(1);
-    expect(nodes.length).toBeGreaterThanOrEqual(10);
+    expect(nodes.some((n) => n.type === 'gate')).toBe(false); // payment-check email IS the gate
+    expect(nodes.some((n) => JSON.parse(n.config || '{}').action === 'queue_payment_check')).toBe(true);
 
-    await seedBuiltinWorkflowsAtBoot(db, noopLogger); // idempotent
+    await seedBuiltinWorkflowsAtBoot(db, noopLogger); // idempotent at current seed version
     const all = await db('workflows').where({ builtin_key: DUNNING_KEY });
     expect(all.length).toBe(1);
   });
+
+  test('re-seeds a disabled, stale built-in but never an enabled one', async () => {
+    const { seedBuiltinWorkflowsAtBoot, DUNNING_KEY } = require('../../src/services/_workflowSeedBoot');
+    const noopLogger = { info() {}, warn() {} };
+
+    // Simulate an older, never-activated seed (v1, with a legacy gate node).
+    const wf = await db('workflows').where({ builtin_key: DUNNING_KEY }).first();
+    await db('workflows').where({ id: wf.id }).update({ enabled: false, trigger_config: JSON.stringify({ seedVersion: 1 }) });
+    await db('workflow_nodes').insert({ workflow_id: wf.id, version: wf.version, node_key: 'legacyGate', type: 'gate', config: '{}', pos_x: 0, pos_y: 0 });
+
+    await seedBuiltinWorkflowsAtBoot(db, noopLogger);
+    const reseeded = await db('workflows').where({ id: wf.id }).first();
+    expect(reseeded.version).toBe(wf.version + 1); // bumped
+    expect(JSON.parse(reseeded.trigger_config).seedVersion).toBe(2);
+    const newNodes = await db('workflow_nodes').where({ workflow_id: wf.id, version: reseeded.version });
+    expect(newNodes.some((n) => n.type === 'gate')).toBe(false); // legacy graph replaced
+
+    // Enabled + stale → must NOT be touched (it's the admin's live flow).
+    await db('workflows').where({ id: wf.id }).update({ enabled: true, trigger_config: JSON.stringify({ seedVersion: 1 }) });
+    const before = await db('workflows').where({ id: wf.id }).first();
+    await seedBuiltinWorkflowsAtBoot(db, noopLogger);
+    const after = await db('workflows').where({ id: wf.id }).first();
+    expect(after.version).toBe(before.version); // unchanged
+  });
 });
diff --git a/backend/src/services/_workflowSeedBoot.js b/backend/src/services/_workflowSeedBoot.js
index 01a74175..6601c607 100644
--- a/backend/src/services/_workflowSeedBoot.js
+++ b/backend/src/services/_workflowSeedBoot.js
@@ -18,78 +18,117 @@
 const { getAppSetting } = require('../utils/appSettings');
 
 const DUNNING_KEY = 'invoice_dunning';
+// Bump when the built-in graph changes so a disabled, never-activated copy is
+// re-seeded on boot. v2 = the delegation/cutover graph (payment-check gate).
+const SEED_VERSION = 2;
 
 function buildDunningGraph({ firstDays, gapDays, maxReminders }) {
+  // Delegation model: the payment-check email IS the admin gate (it drives the
+  // existing confirm + reminder_level + Mahngebühr state machine), so the flow
+  // just decides WHEN to fire it. After due date + grace, loop up to
+  // maxReminders times: if still unpaid, queue a payment-check, wait the gap,
+  // repeat; stop early once paid.
   const nodes = [
     { node_key: 't', type: 'trigger', config: {}, pos_x: 240, pos_y: 0 },
     { node_key: 'waitDue', type: 'wait', config: { untilVar: 'dueDate' }, pos_x: 240, pos_y: 110 },
     { node_key: 'waitGrace', type: 'wait', config: { delayDays: firstDays }, pos_x: 240, pos_y: 220 },
-    { node_key: 'checkPaid', type: 'condition', config: { condition: 'invoice_paid' }, pos_x: 240, pos_y: 330 },
-    { node_key: 'gate', type: 'gate', config: { type: 'payment_confirm', prompt: 'No payment received yet — send a reminder?' }, pos_x: 240, pos_y: 440 },
-    { node_key: 'loop', type: 'loop', config: { maxIterations: maxReminders }, pos_x: 240, pos_y: 550 },
-    { node_key: 'remind', type: 'action', config: { action: 'send_email', recipientClass: 'customer', emailType: 'invoice_reminder' }, pos_x: 240, pos_y: 660 },
-    { node_key: 'waitGap', type: 'wait', config: { delayDays: gapDays }, pos_x: 240, pos_y: 770 },
-    { node_key: 'final', type: 'action', config: { action: 'send_email', recipientClass: 'customer', emailType: 'invoice_final_notice' }, pos_x: 520, pos_y: 660 },
-    { node_key: 'doneEnd', type: 'action', config: { action: 'noop' }, pos_x: 520, pos_y: 770 },
-    { node_key: 'donePaid', type: 'action', config: { action: 'noop' }, pos_x: 520, pos_y: 330 },
+    { node_key: 'loop', type: 'loop', config: { maxIterations: maxReminders }, pos_x: 240, pos_y: 330 },
+    { node_key: 'checkPaid', type: 'condition', config: { condition: 'invoice_paid' }, pos_x: 240, pos_y: 440 },
+    { node_key: 'paymentCheck', type: 'action', config: { action: 'queue_payment_check' }, pos_x: 240, pos_y: 550 },
+    { node_key: 'waitGap', type: 'wait', config: { delayDays: gapDays }, pos_x: 240, pos_y: 660 },
+    { node_key: 'donePaid', type: 'action', config: { action: 'noop' }, pos_x: 520, pos_y: 440 },
+    { node_key: 'doneEnd', type: 'action', config: { action: 'noop' }, pos_x: 520, pos_y: 330 },
   ];
   const edges = [
     { from_node: 't', to_node: 'waitDue' },
     { from_node: 'waitDue', to_node: 'waitGrace' },
-    { from_node: 'waitGrace', to_node: 'checkPaid' },
+    { from_node: 'waitGrace', to_node: 'loop' },
+    { from_node: 'loop', from_handle: 'loop', to_node: 'checkPaid' },
+    { from_node: 'loop', from_handle: 'exit', to_node: 'doneEnd' },
     { from_node: 'checkPaid', from_handle: 'yes', to_node: 'donePaid' },
-    { from_node: 'checkPaid', from_handle: 'no', to_node: 'gate' },
-    { from_node: 'gate', from_handle: 'confirm', to_node: 'loop' },
-    { from_node: 'gate', from_handle: 'deny', to_node: 'donePaid' },
-    { from_node: 'loop', from_handle: 'loop', to_node: 'remind' },
-    { from_node: 'loop', from_handle: 'exit', to_node: 'final' },
-    { from_node: 'remind', to_node: 'waitGap' },
-    { from_node: 'waitGap', to_node: 'checkPaid', loop_back: true },
-    { from_node: 'final', to_node: 'doneEnd' },
+    { from_node: 'checkPaid', from_handle: 'no', to_node: 'paymentCheck' },
+    { from_node: 'paymentCheck', to_node: 'waitGap' },
+    { from_node: 'waitGap', to_node: 'loop', loop_back: true },
   ];
   return { nodes, edges };
 }
 
 let booted = false;
 
+function parseSeedConfig(raw) {
+  if (raw == null) return {};
+  if (typeof raw === 'object') return raw;
+  try { return JSON.parse(raw) || {}; } catch (e) { return {}; }
+}
+
+async function writeGraph(trx, workflowId, version, nodes, edges) {
+  for (const n of nodes) {
+    await trx('workflow_nodes').insert({
+      workflow_id: workflowId, version, node_key: n.node_key, type: n.type,
+      config: JSON.stringify(n.config || {}), pos_x: n.pos_x || 0, pos_y: n.pos_y || 0,
+    });
+  }
+  for (const e of edges) {
+    await trx('workflow_edges').insert({
+      workflow_id: workflowId, version, from_node: e.from_node, from_handle: e.from_handle || null,
+      to_node: e.to_node, label: e.label || null, loop_back: !!e.loop_back,
+    });
+  }
+}
+
 async function seedBuiltinWorkflowsAtBoot(db, logger) {
   try {
     if (!(await db.schema.hasTable('workflows'))) return;
-    const existing = await db('workflows').where({ builtin_key: DUNNING_KEY }).first();
-    if (existing) { booted = true; return; }
 
     const firstDays = Number(await getAppSetting('crm_invoices_reminder_first_days')) || 14;
     const secondDays = Number(await getAppSetting('crm_invoices_reminder_second_days')) || 30;
     const gapDays = Math.max(1, secondDays - firstDays);
     const { nodes, edges } = buildDunningGraph({ firstDays, gapDays, maxReminders: 2 });
 
+    const description = 'Drives overdue dunning through the engine: wait to the due date, then up '
+      + 'to two payment-check cycles. Each cycle fires the existing admin confirm-payment email '
+      + '(the gate), which applies reminders + Mahngebühr via the proven payment-check flow. '
+      + 'Disabled by default; while it is enabled the hardcoded reminder ladder is skipped '
+      + 'automatically, so the two never double-send.';
+
+    const existing = await db('workflows').where({ builtin_key: DUNNING_KEY }).first();
+
+    if (existing) {
+      // Re-seed the graph only when (a) it has never been activated and (b) our
+      // seed version moved on (the dunning cutover). Once the admin enables it,
+      // it's their live flow — never overwrite it.
+      const storedVersion = Number(parseSeedConfig(existing.trigger_config).seedVersion) || 0;
+      const isEnabled = existing.enabled === true || existing.enabled === 1;
+      if (isEnabled || storedVersion >= SEED_VERSION) { booted = true; return; }
+
+      const newVersion = (existing.version || 1) + 1;
+      await db.transaction(async (trx) => {
+        await trx('workflows').where({ id: existing.id }).update({
+          name: 'Invoice dunning (built-in)',
+          description,
+          trigger_config: JSON.stringify({ seedVersion: SEED_VERSION }),
+          version: newVersion,
+          updated_at: trx.fn.now(),
+        });
+        await writeGraph(trx, existing.id, newVersion, nodes, edges);
+      });
+      booted = true;
+      logger?.info?.('Re-seeded built-in workflow: invoice dunning (delegation graph v2)');
+      return;
+    }
+
     await db.transaction(async (trx) => {
       const ins = await trx('workflows').insert({
         name: 'Invoice dunning (built-in)',
-        description: 'Editable copy of the overdue-reminder ladder: wait to due date, '
-          + 'confirm-no-payment gate, then up to two reminders before a final notice. '
-          + 'Disabled by default — the live reminder ladder still runs via the scheduler '
-          + 'until an explicit cutover, so enabling this without that change would double-send.',
+        description,
         enabled: false,
         version: 1,
         trigger_type: 'invoice.sent',
-        trigger_config: null,
+        trigger_config: JSON.stringify({ seedVersion: SEED_VERSION }),
         is_builtin: true,
         builtin_key: DUNNING_KEY,
       });
-      const workflowId = ins[0];
-      for (const n of nodes) {
-        await trx('workflow_nodes').insert({
-          workflow_id: workflowId, version: 1, node_key: n.node_key, type: n.type,
-          config: JSON.stringify(n.config || {}), pos_x: n.pos_x || 0, pos_y: n.pos_y || 0,
-        });
-      }
-      for (const e of edges) {
-        await trx('workflow_edges').insert({
-          workflow_id: workflowId, version: 1, from_node: e.from_node, from_handle: e.from_handle || null,
-          to_node: e.to_node, label: e.label || null, loop_back: !!e.loop_back,
-        });
-      }
+      await writeGraph(trx, ins[0], 1, nodes, edges);
     });
 
     booted = true;
diff --git a/backend/src/services/invoiceService.js b/backend/src/services/invoiceService.js
index 821e9186..b779338b 100644
--- a/backend/src/services/invoiceService.js
+++ b/backend/src/services/invoiceService.js
@@ -3392,7 +3392,18 @@ async function runScheduledTasks() {
   // Throttled to one email per 24h per invoice via
   // invoices.last_payment_check_at.
   const remindersEnabled = await getAppSetting('crm_invoices_reminders_enabled');
-  if (remindersEnabled !== false) {
+  // Mutual exclusion with the workflow engine: when the `workflows` flag is on
+  // AND the invoice_dunning built-in is enabled, the engine fires the same
+  // payment-check emails — running this hardcoded ladder too would double-send.
+  let engineDrivesDunning = false;
+  try {
+    const { isFeatureEnabled } = require('../middleware/requireFeatureFlag');
+    if (await isFeatureEnabled('workflows')) {
+      const dunning = await db('workflows').where({ builtin_key: 'invoice_dunning', enabled: true }).first();
+      engineDrivesDunning = !!dunning;
+    }
+  } catch (_) { /* workflows tables absent / flag system down → ladder stays on */ }
+  if (remindersEnabled !== false && !engineDrivesDunning) {
     const firstDays  = ensureInt(await getAppSetting('crm_invoices_reminder_first_days')) || 14;
     const secondDays = ensureInt(await getAppSetting('crm_invoices_reminder_second_days')) || 30;
 
diff --git a/backend/src/services/workflows/actions.js b/backend/src/services/workflows/actions.js
index 7b3077cd..37388499 100644
--- a/backend/src/services/workflows/actions.js
+++ b/backend/src/services/workflows/actions.js
@@ -66,6 +66,19 @@ registry.registerAction('send_email', async (ctx) => {
   return { sent_to: to, recipientClass, respectBusinessHours };
 });
 
+// Fire the existing admin payment-check email (the dunning gate). Delegates to
+// invoiceService.queuePaymentCheckEmail so the proven escalation +
+// Mahngebühr / reminder_level state machine (recordPaymentCheckAction) stays
+// the single source of truth — the workflow only decides WHEN it fires. This
+// is what makes the built-in dunning flow a faithful replacement for the
+// hardcoded ladder (paired with the mutual-exclusion guard in runScheduledTasks).
+registry.registerAction('queue_payment_check', async (ctx) => {
+  const id = ctx.run.entity_id;
+  if (!id) return { skipped: true, reason: 'no invoice entity' };
+  await require('../invoiceService').queuePaymentCheckEmail(id);
+  return { payment_check_queued: id };
+});
+
 // Create/prepare-document actions — registered so flows referencing them are
 // valid; service wiring is a follow-up. Records a skipped step (observable).
 for (const key of DOCUMENT_ACTIONS) {