From b9c12c21843f4f5a7e49a5126bec7f80ead63be2 Mon Sep 17 00:00:00 2001
From: vaibhavmashal <vaibhavmashal098@gmail.com>
Date: Tue, 8 Sep 2026 22:15:26 +0530
Subject: [PATCH] fix: prevent ERR_HTTP_HEADERS_SENT when response headers sent
 during request wait (#162)

---
 index.js     |  4 ++++
 test/test.js | 28 ++++++++++++++++++++++++++++
 2 files changed, 32 insertions(+)

diff --git a/index.js b/index.js
index bf15e48..3ac07a0 100644
--- a/index.js
+++ b/index.js
@@ -243,6 +243,10 @@ function getResponseStatusCode (res) {
 
 function send (req, res, status, headers, message) {
   function write () {
+    if (res.headersSent) {
+      return
+    }
+
     // response body
     var body = createHtmlDocument(message)
 
diff --git a/test/test.js b/test/test.js
index 516e088..76f4294 100644
--- a/test/test.js
+++ b/test/test.js
@@ -393,6 +393,34 @@ var topDescribe = function (type, createServer) {
         test.write(buf)
         test.expect(500, done)
       })
+
+      it('should not throw if headers are sent while waiting for request', function (done) {
+        var buf = Buffer.alloc(1024 * 16, '.')
+        var server = createServer(function (req, res, next) {
+          next()
+          res.setHeader('Content-Type', 'text/plain')
+          res.end('ok')
+        })
+        var test = wrapper(request(server).post('/foo'))
+        test.write(buf)
+        test.write(buf)
+        test.write(buf)
+        test.expect(200, 'ok', done)
+      })
+
+      it('should not throw if headers are sent while waiting for request on error', function (done) {
+        var buf = Buffer.alloc(1024 * 16, '.')
+        var server = createServer(function (req, res, next) {
+          next(new Error('boom!'))
+          res.setHeader('Content-Type', 'text/plain')
+          res.end('error response')
+        })
+        var test = wrapper(request(server).post('/foo'))
+        test.write(buf)
+        test.write(buf)
+        test.write(buf)
+        test.expect(200, 'error response', done)
+      })
     })
 
     describe('when res.statusCode set', function () {