From bdc41cac80427a3b8eb52ae9056dfc159cfb6f3a Mon Sep 17 00:00:00 2001
From: Elie Rotenberg <elie.rotenberg@gmail.com>
Date: Wed, 24 Jun 2026 08:03:14 +0200
Subject: [PATCH] fix: Don't set redundant Content-Length on file upload
 requests

fetch derives Content-Length from the request body. Setting it
explicitly sent a duplicate header, which undici >= 7.26 rejects with
UND_ERR_INVALID_ARG when a userland dispatcher is active.

Fixes #1718
---
 src/cross/_cross_uploader.ts |  3 ++-
 src/node/_node_uploader.ts   |  3 ++-
 test/unit/file_test.ts       | 33 +++++++++++++++++++++++++++++++++
 3 files changed, 37 insertions(+), 2 deletions(-)

diff --git a/src/cross/_cross_uploader.ts b/src/cross/_cross_uploader.ts
index 1bdf730a97..361bc63e0c 100644
--- a/src/cross/_cross_uploader.ts
+++ b/src/cross/_cross_uploader.ts
@@ -143,7 +143,8 @@ async function uploadBlobInternal(
         ...(httpOptions?.headers || {}),
         'X-Goog-Upload-Command': uploadCommand,
         'X-Goog-Upload-Offset': String(offset),
-        'Content-Length': String(chunkSize),
+        // Don't set Content-Length: fetch derives it from the body, and a
+        // duplicate is rejected by undici >= 7.26 (#1718).
       };
 
       response = await apiClient.request({
diff --git a/src/node/_node_uploader.ts b/src/node/_node_uploader.ts
index e4166c148b..0a826245b8 100644
--- a/src/node/_node_uploader.ts
+++ b/src/node/_node_uploader.ts
@@ -283,8 +283,9 @@ export class NodeUploader implements Uploader {
             ...(httpOptions?.headers || {}),
             'X-Goog-Upload-Command': uploadCommand,
             'X-Goog-Upload-Offset': String(offset),
-            'Content-Length': String(bytesRead),
             'X-Goog-Upload-File-Name': fileName,
+            // Don't set Content-Length: fetch derives it from the body, and a
+            // duplicate is rejected by undici >= 7.26 (#1718).
           };
 
           response = await apiClient.request({
diff --git a/test/unit/file_test.ts b/test/unit/file_test.ts
index 4b0bea17ba..072a4ccbfc 100644
--- a/test/unit/file_test.ts
+++ b/test/unit/file_test.ts
@@ -351,6 +351,39 @@ describe('File', () => {
         }
         expect(byteProcessed).toBe(fileSize);
       });
+      it('It should not send a Content-Length that undici >= 7.26 would reject.', async () => {
+        const testBlob = new Blob([new Uint8Array(8)], {
+          type: DEFAULT_TEST_MIMETYPE,
+        });
+
+        spyOn(global, 'fetch').and.callFake((_input, init) => {
+          const headers = init?.headers as Headers | undefined;
+          // Mimic undici >= 7.26, which rejects a request that carries both a
+          // body and an explicit Content-Length (#1718).
+          if (init?.body && headers?.get('Content-Length')) {
+            return Promise.reject(
+              new TypeError('fetch failed', {
+                cause: {code: 'UND_ERR_INVALID_ARG'},
+              }),
+            );
+          }
+          // The chunk request carries the upload offset; anything else is the
+          // initial request that returns the upload url.
+          if (headers?.get('X-Goog-Upload-Offset') !== null) {
+            return Promise.resolve(
+              new Response(
+                JSON.stringify({file: {name: 'files/test-file'}}),
+                lastCorrectFetchOkOptions,
+              ),
+            );
+          }
+          return Promise.resolve(new Response('', createUrlOkoptions));
+        });
+
+        const uploaded = await client.files.upload({file: testBlob});
+
+        expect(uploaded.name).toBe('files/test-file');
+      });
     });
   });
   describe('registerFiles', () => {