diff --git a/backend/__tests__/integration/workflowEngine.test.js b/backend/__tests__/integration/workflowEngine.test.js
index c57f4939..a038e62e 100644
--- a/backend/__tests__/integration/workflowEngine.test.js
+++ b/backend/__tests__/integration/workflowEngine.test.js
@@ -233,4 +233,23 @@ describe('workflow engine', () => {
     const again = await engine.actByToken(rawToken, 'confirm');
     expect(again.already).toBe(true);
   });
+
+  test('seeds the invoice-dunning built-in flow (disabled, idempotent)', async () => {
+    const { seedBuiltinWorkflowsAtBoot, DUNNING_KEY } = require('../../src/services/_workflowSeedBoot');
+    const noopLogger = { info() {}, warn() {} };
+    await seedBuiltinWorkflowsAtBoot(db, noopLogger);
+
+    const wf = await db('workflows').where({ builtin_key: DUNNING_KEY }).first();
+    expect(wf).toBeTruthy();
+    expect(!!wf.is_builtin).toBe(true);
+    expect(!!wf.enabled).toBe(false);
+
+    const nodes = await db('workflow_nodes').where({ workflow_id: wf.id, version: 1 });
+    expect(nodes.filter((n) => n.type === 'trigger')).toHaveLength(1);
+    expect(nodes.length).toBeGreaterThanOrEqual(10);
+
+    await seedBuiltinWorkflowsAtBoot(db, noopLogger); // idempotent
+    const all = await db('workflows').where({ builtin_key: DUNNING_KEY });
+    expect(all.length).toBe(1);
+  });
 });
diff --git a/backend/server.js b/backend/server.js
index 4fd62cb9..6b71ea3f 100644
--- a/backend/server.js
+++ b/backend/server.js
@@ -897,6 +897,15 @@ async function startServer() {
       logger.warn('restore-settings self-heal failed at boot:', err.message);
     }
 
+    // Seed built-in workflows (the editable invoice-dunning flow). Disabled by
+    // default — live reminder behaviour is unchanged. See _workflowSeedBoot.js.
+    try {
+      const { seedBuiltinWorkflowsAtBoot } = require('./src/services/_workflowSeedBoot');
+      await seedBuiltinWorkflowsAtBoot(db, logger);
+    } catch (err) {
+      logger.warn('built-in workflow seed failed at boot:', err.message);
+    }
+
     // Install-from-backup trigger. If `RESTORE_ON_INSTALL` (or
     // `.txt`) exists in the /backup mount AND the DB is empty, run
     // the restore HERE before any admin UI surfaces. Lets admins
diff --git a/backend/src/services/_workflowSeedBoot.js b/backend/src/services/_workflowSeedBoot.js
new file mode 100644
index 00000000..01a74175
--- /dev/null
+++ b/backend/src/services/_workflowSeedBoot.js
@@ -0,0 +1,102 @@
+/**
+ * Boot-time seed for built-in workflows.
+ *
+ * Seeds the invoice-dunning ladder as an EDITABLE built-in flow (the corrected
+ * gate-in-loop graph), so the canvas has real content and admins can see their
+ * reminder process as blocks. Seeded from the current reminder settings.
+ *
+ * IMPORTANT — seeded DISABLED, and live behaviour is UNCHANGED: the existing
+ * hardcoded reminder ladder in invoiceService.runScheduledTasks still runs. The
+ * cutover (drive reminders through the engine + stop the hardcoded ladder) is a
+ * deliberate follow-up so we never double-send. Enabling this flow before that
+ * cutover would duplicate reminders — hence default off.
+ *
+ * Idempotent: keyed on builtin_key='invoice_dunning'. Once seeded, admin edits
+ * are preserved (we never overwrite an existing built-in). Self-heal pattern
+ * per [[feedback_self_heal_pattern]].
+ */
+const { getAppSetting } = require('../utils/appSettings');
+
+const DUNNING_KEY = 'invoice_dunning';
+
+function buildDunningGraph({ firstDays, gapDays, maxReminders }) {
+  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 },
+  ];
+  const edges = [
+    { from_node: 't', to_node: 'waitDue' },
+    { from_node: 'waitDue', to_node: 'waitGrace' },
+    { from_node: 'waitGrace', to_node: 'checkPaid' },
+    { 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' },
+  ];
+  return { nodes, edges };
+}
+
+let booted = false;
+
+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 });
+
+    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.',
+        enabled: false,
+        version: 1,
+        trigger_type: 'invoice.sent',
+        trigger_config: null,
+        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,
+        });
+      }
+    });
+
+    booted = true;
+    logger?.info?.('Seeded built-in workflow: invoice dunning (disabled)');
+  } catch (err) {
+    logger?.warn?.('Built-in workflow seed failed at boot:', err.message);
+  }
+}
+
+module.exports = { seedBuiltinWorkflowsAtBoot, buildDunningGraph, DUNNING_KEY };