diff --git a/dashcaddy-api/__tests__/atomic-write-dc099.test.js b/dashcaddy-api/__tests__/atomic-write-dc099.test.js
index 5023e64..e64e3b3 100644
--- a/dashcaddy-api/__tests__/atomic-write-dc099.test.js
+++ b/dashcaddy-api/__tests__/atomic-write-dc099.test.js
@@ -422,3 +422,63 @@ describe('DC-103 fulfillment-store on canonical atomic-write (real fs)', () => {
     expect(leftovers).toEqual([]);
   });
 });
+
+// DC-104: stripe-license-bridge events file (Stripe webhook idempotency
+// log) migrated off its private tmp+writeFileSync+rename copy onto the
+// canonical writer. A torn stripe-events.json silently drops event-ids —
+// the next Stripe retry then re-runs delivery (duplicate license email /
+// duplicate key mint when combined with a torn fulfillment record).
+// Pins: 0600 on create, complete JSON after every recordEvent mutation,
+// no temp leftovers, and the full read-modify-write dedupe cycle through
+// the bridge's exported functions. (The ignored-type / unpaid-status
+// write classes route through the same writeEvents and are driven
+// end-to-end in __tests__/billing/stripe-license-bridge.test.js.)
+describe('DC-104 bridge events file on canonical atomic-write (real fs)', () => {
+  let dir;
+
+  beforeEach(() => {
+    dir = fs.mkdtempSync(path.join(os.tmpdir(), 'dc104-events-'));
+    process.env.STRIPE_BRIDGE_EVENTS_FILE = path.join(dir, 'stripe-events.json');
+    jest.resetModules();
+  });
+  afterEach(() => {
+    delete process.env.STRIPE_BRIDGE_EVENTS_FILE;
+    try { fs.rmSync(dir, { recursive: true, force: true }); } catch (_) {}
+  });
+
+  test('recordEvent → eventSeen dedupe cycle lands at 0600, complete JSON, no temp leftovers', () => {
+    // Env is captured at require time — resetModules above makes this
+    // require see the fresh STRIPE_BRIDGE_EVENTS_FILE.
+    const bridge = require('../scripts/stripe-license-bridge');
+
+    const first = bridge.recordEvent('evt_dc104_a', { ignoredType: 'product.updated' });
+    expect(first).toBe(true);            // new event recorded
+    expect(bridge.eventSeen('evt_dc104_a')).toBe(true);
+    expect(bridge.eventSeen('evt_dc104_unknown')).toBe(false);
+
+    const dup = bridge.recordEvent('evt_dc104_a', { ignoredType: 'product.updated' });
+    expect(dup).toBe(false);             // idempotent — already present
+
+    const file = path.join(dir, 'stripe-events.json');
+    const st = fs.statSync(file);
+    expect(st.mode & 0o777).toBe(0o600); // canonical writer default
+
+    // complete JSON carrying the event — a torn write would fail parse here
+    const data = JSON.parse(fs.readFileSync(file, 'utf8'));
+    expect(data.events['evt_dc104_a'].ignoredType).toBe('product.updated');
+
+    const leftovers = fs.readdirSync(dir).filter((f) => f !== 'stripe-events.json');
+    expect(leftovers).toEqual([]);       // no tmp survivors
+  });
+
+  test('back-to-back recordEvent writes parse complete after every mutation', () => {
+    const bridge = require('../scripts/stripe-license-bridge');
+    for (let i = 0; i < 8; i += 1) {
+      const ok = bridge.recordEvent(`evt_dc104_seq_${i}`, { ignoredType: 'product.updated', seq: i });
+      expect(ok).toBe(true);
+      const file = path.join(dir, 'stripe-events.json');
+      const data = JSON.parse(fs.readFileSync(file, 'utf8')); // throws on torn write
+      expect(Object.keys(data.events)).toHaveLength(i + 1);
+    }
+  });
+});
diff --git a/dashcaddy-api/scripts/stripe-license-bridge.js b/dashcaddy-api/scripts/stripe-license-bridge.js
index 706878c..fe4cdf2 100644
--- a/dashcaddy-api/scripts/stripe-license-bridge.js
+++ b/dashcaddy-api/scripts/stripe-license-bridge.js
@@ -105,6 +105,7 @@ const fs = require('fs');
 const path = require('path');
 const { generateCodes, loadSecret } = require('../license-keygen');
 const platformPaths = require('../platform-paths');
+const { atomicWriteJSON } = require('../src/utils/atomic-write');
 const catalog = require('../src/billing/catalog');
 const invoice = require('../src/billing/invoice');
 const { createFulfillmentStore, DELIVERY_LEASE_MS } = require('../src/billing/fulfillment-store');
@@ -220,10 +221,11 @@ function readEvents() {
 }
 
 function writeEvents(state) {
-  // Atomic write: tmp + rename.
-  const tmp = `${EVENTS_FILE}.tmp.${process.pid}.${Date.now()}`;
-  fs.writeFileSync(tmp, JSON.stringify(state, null, 2) + '\n', { mode: 0o600 });
-  fs.renameSync(tmp, EVENTS_FILE);
+  // Canonical atomic writer (DC-099/DC-104): exclusive-create tmp + fsync +
+  // rename + parent-dir fsync, 0600. Replaces the private tmp+rename copy —
+  // a torn stripe-events.json silently drops event-ids, which makes a
+  // Stripe retry re-run delivery (duplicate license email / duplicate key).
+  atomicWriteJSON(EVENTS_FILE, state, { mode: 0o600 });
 }
 
 function recordEvent(eventId, meta) {