From 4bf6748ba2f18720bf14e8243cfb6661e9332629 Mon Sep 17 00:00:00 2001
From: Alex Castillo <alex.castillog33@gmail.com>
Date: Tue, 10 Nov 2026 15:13:31 -0400
Subject: [PATCH 1/2] fix: release event sender when fetch rejects

---
 src/xhr.js | 11 ++++++++---
 1 file changed, 8 insertions(+), 3 deletions(-)

diff --git a/src/xhr.js b/src/xhr.js
index 1c1110cc..4e38b02f 100644
--- a/src/xhr.js
+++ b/src/xhr.js
@@ -61,9 +61,14 @@ Request.prototype.send = function (callback) {
         responseStatus = response.status;
         return response.text();
       })
-      .then((responseText) => {
-        callback(responseStatus, responseText);
-      });
+      .then(
+        (responseText) => {
+          callback(responseStatus, responseText);
+        },
+        () => {
+          callback(0, '');
+        },
+      );
   }
   //log('sent request to ' + this.url + ' with data ' + decodeURIComponent(queryString(this.data)));
 };

From 45e876b75dcf5eb4b400dd715d0c674b23af9d1f Mon Sep 17 00:00:00 2001
From: Alex Castillo <alex.castillog33@gmail.com>
Date: Tue, 10 Nov 2026 15:18:31 -0400
Subject: [PATCH 2/2] test: cover fetch failures and event upload retries

---
 test/amplitude-client.js | 47 ++++++++++++++++++++++++++++++++++++++++
 1 file changed, 47 insertions(+)

diff --git a/test/amplitude-client.js b/test/amplitude-client.js
index 52d551fc..edea1480 100644
--- a/test/amplitude-client.js
+++ b/test/amplitude-client.js
@@ -12,6 +12,7 @@ import constants from '../src/constants.js';
 import { mockCookie, restoreCookie, getCookie } from './mock-cookie';
 import { AmplitudeServerZone } from '../src/server-zone.js';
 import Request from '../src/xhr';
+import GlobalScope from '../src/global-scope';
 
 const deleteAllCookies = () =>
   document.cookie.split(';').forEach(function (c) {
@@ -1674,6 +1675,52 @@ describe('AmplitudeClient', function () {
     });
   });
 
+  describe('fetch transport failures', function () {
+    beforeEach(function () {
+      reset();
+      amplitude.init(apiKey);
+      sandbox.stub(GlobalScope, 'XMLHttpRequest').value(undefined);
+    });
+
+    afterEach(function () {
+      reset();
+    });
+
+    ['fetch', 'response.text'].forEach(function (failure) {
+      it('should retain events and allow retry after ' + failure + ' rejects', async function () {
+        const error = new Error('Network failure');
+        const fetchStub = sandbox.stub(GlobalScope, 'fetch');
+        if (failure === 'fetch') {
+          fetchStub.onFirstCall().rejects(error);
+        } else {
+          fetchStub.onFirstCall().resolves({ status: 200, text: () => Promise.reject(error) });
+        }
+        fetchStub.onSecondCall().resolves({ status: 200, text: () => Promise.resolve('success') });
+
+        amplitude.logEvent('Retried event');
+        const event = amplitude._unsentEvents[0];
+        assert.isTrue(amplitude._sending);
+        await new Promise((resolve) => setTimeout(resolve, 0));
+
+        assert.isFalse(amplitude._sending);
+        assert.lengthOf(amplitude._unsentEvents, 1);
+        assert.strictEqual(amplitude._unsentEvents[0], event);
+        assert.isTrue(fetchStub.calledOnce);
+
+        amplitude.sendEvents();
+        await new Promise((resolve) => setTimeout(resolve, 0));
+
+        assert.isTrue(fetchStub.calledTwice);
+        assert.equal(
+          queryString.parse(fetchStub.secondCall.args[1].body).e,
+          queryString.parse(fetchStub.firstCall.args[1].body).e,
+        );
+        assert.isFalse(amplitude._sending);
+        assert.lengthOf(amplitude._unsentEvents, 0);
+      });
+    });
+  });
+
   describe('logEvent', function () {
     let clock, startTime;