diff --git a/CHANGELOG.md b/CHANGELOG.md
index b0247b7..f81d377 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -1,3 +1,12 @@
+### v3.28.1 (2026-07-16)
+* * *
+### Bug Fixes:
+- Stopped setting the `Content-Length` header manually in `RequestWrapper`. `fetch`/undici already derives the correct value from the request `body`, so the manual header was redundant. When `FetchHttpClient` re-wraps the request (`new Request(request, { signal })`), some Node builds re-append the body-derived value, producing a comma-joined `"N, N"`. undici (>= 7.28) validates `Content-Length` with a strict all-digit check and rejects that value with `InvalidArgumentError: invalid content-length header`, failing the request before it reaches Chargebee. The header is now left to the platform. This is distinct from the value-correctness fix in v3.24.1 (issue #119). Verified on Node 18/20/22/24 and Cloudflare Workers (`workerd`), where the runtime emits the correct UTF-8 byte-length `Content-Length` on the wire.
+
+### Tests:
+- POST requests no longer set a `Content-Length` header on the outgoing `Request` (ASCII form-urlencoded and multi-byte JSON bodies), guarding against the duplicate-header regression while preserving body integrity.
+
+
 ### v3.28.0 (2026-06-30)
 * * *
 
diff --git a/VERSION b/VERSION
index a72fd67..54d1636 100644
--- a/VERSION
+++ b/VERSION
@@ -1 +1 @@
-3.28.0
+3.28.1
diff --git a/package-lock.json b/package-lock.json
index d6ca222..faa7c56 100644
--- a/package-lock.json
+++ b/package-lock.json
@@ -1,12 +1,12 @@
 {
   "name": "chargebee",
-  "version": "3.28.0",
+  "version": "3.28.1",
   "lockfileVersion": 3,
   "requires": true,
   "packages": {
     "": {
       "name": "chargebee",
-      "version": "3.28.0",
+      "version": "3.28.1",
       "dependencies": {
         "zod": "^4.3.6"
       },
diff --git a/package.json b/package.json
index 06a4647..f1e1cda 100644
--- a/package.json
+++ b/package.json
@@ -1,6 +1,6 @@
 {
   "name": "chargebee",
-  "version": "3.28.0",
+  "version": "3.28.1",
   "description": "A library for integrating with Chargebee.",
   "scripts": {
     "prepack": "npm install && npm run build",
diff --git a/src/RequestWrapper.ts b/src/RequestWrapper.ts
index df3b0ae..988d109 100644
--- a/src/RequestWrapper.ts
+++ b/src/RequestWrapper.ts
@@ -233,11 +233,6 @@ export class RequestWrapper {
         ...this.httpHeaders,
         ...telemetryHeaders,
       };
-      if (data && data.length) {
-        extend(true, requestHeaders, {
-          'Content-Length': Buffer.byteLength(data, 'utf8'),
-        });
-      }
 
       const contentType = this.apiCall.isJsonRequest
         ? 'application/json;charset=UTF-8'
diff --git a/src/environment.ts b/src/environment.ts
index a57f3db..78b92db 100644
--- a/src/environment.ts
+++ b/src/environment.ts
@@ -9,7 +9,7 @@ export const Environment = {
   hostSuffix: '.chargebee.com',
   apiPath: '/api/v2',
   timeout: DEFAULT_TIME_OUT,
-  clientVersion: 'v3.28.0',
+  clientVersion: 'v3.28.1',
   port: DEFAULT_PORT,
   timemachineWaitInMillis: DEFAULT_TIME_MACHINE_WAIT,
   exportWaitInMillis: DEFAULT_EXPORT_WAIT,
diff --git a/test/requestWrapper.test.ts b/test/requestWrapper.test.ts
index b0f9494..45c30e3 100644
--- a/test/requestWrapper.test.ts
+++ b/test/requestWrapper.test.ts
@@ -191,7 +191,12 @@ describe('RequestWrapper - request headers', () => {
   });
 
   describe('Content-Length header', () => {
-    it('should set Content-Length to the UTF-8 byte length for ASCII form-urlencoded bodies', async () => {
+    // The SDK must NOT set Content-Length manually. fetch/undici derives it from
+    // `body` at dispatch time; a manual header is redundant and can be re-appended
+    // into a comma-joined "N, N" when FetchHttpClient re-wraps the Request, which
+    // undici (>= 7.28) rejects as an invalid content-length header.
+    // See: RequestWrapper#request and src/net/FetchClient.ts.
+    it('should NOT set Content-Length manually for ASCII form-urlencoded bodies', async () => {
       responseFactory = () =>
         new Response(JSON.stringify({ customer: { id: 'cust_123' } }), {
           status: 200,
@@ -202,13 +207,11 @@ describe('RequestWrapper - request headers', () => {
       await chargebee.customer.create({ first_name: 'John' });
 
       const body = await capturedRequests[0].text();
-      const expected = Buffer.byteLength(body, 'utf8');
-      expect(capturedRequests[0].headers.get('Content-Length')).to.equal(
-        String(expected),
-      );
+      expect(body).to.include('first_name=John');
+      expect(capturedRequests[0].headers.get('Content-Length')).to.be.null;
     });
 
-    it('should set Content-Length to the UTF-8 byte length (not character count) for multi-byte JSON bodies', async () => {
+    it('should NOT set Content-Length manually for multi-byte JSON bodies', async () => {
       responseFactory = () =>
         new Response(JSON.stringify({ personalized_offers: [] }), {
           status: 200,
@@ -225,10 +228,9 @@ describe('RequestWrapper - request headers', () => {
       const body = await capturedRequests[0].text();
       const byteLength = Buffer.byteLength(body, 'utf8');
       const charLength = body.length;
+      // Body integrity: multi-byte payload is preserved intact.
       expect(byteLength).to.be.greaterThan(charLength);
-      expect(capturedRequests[0].headers.get('Content-Length')).to.equal(
-        String(byteLength),
-      );
+      expect(capturedRequests[0].headers.get('Content-Length')).to.be.null;
     });
   });