diff --git a/packages/isomorphic/headers.ts b/packages/isomorphic/headers.ts
index e228e5312f230..0ffad2aa6c134 100644
--- a/packages/isomorphic/headers.ts
+++ b/packages/isomorphic/headers.ts
@@ -17,6 +17,53 @@
 type HeadersArray = { name: string, value: string }[];
 type HeadersObject = { [key: string]: string };
 
+export const singleValuedHeaders = new Set([
+  'authorization',
+  'content-disposition',
+  'content-length',
+  'content-range',
+  'content-type',
+  'date',
+  'etag',
+  'expires',
+  'host',
+  'if-modified-since',
+  'if-unmodified-since',
+  'last-modified',
+  'location',
+  'proxy-authorization',
+  'referer',
+  'retry-after',
+  'server',
+  'user-agent',
+]);
+
+export function splitSetCookieString(values: string, separator: string): string[] {
+  if (separator !== ',')
+    return values.split(separator).map(v => v.trim()).filter(Boolean);
+  // macOS WebKit joins Set-Cookie headers with ', '.
+  // However, cookie 'Expires' attribute values contain commas (e.g. 'Expires=Wed, 21 Oct 2026 07:28:00 GMT').
+  // We split by comma only when it is not part of an Expires attribute.
+  const cookies: string[] = [];
+  let current = '';
+  for (let i = 0; i < values.length; i++) {
+    if (values[i] === ',') {
+      if (/Expires=[^;]*$/i.test(current)) {
+        current += ',';
+        continue;
+      }
+      if (current.trim())
+        cookies.push(current.trim());
+      current = '';
+    } else {
+      current += values[i];
+    }
+  }
+  if (current.trim())
+    cookies.push(current.trim());
+  return cookies;
+}
+
 export function headersObjectToArray(headers: HeadersObject, separator?: string, setCookieSeparator?: string): HeadersArray {
   if (!setCookieSeparator)
     setCookieSeparator = separator;
@@ -25,10 +72,18 @@ export function headersObjectToArray(headers: HeadersObject, separator?: string,
     const values = headers[name];
     if (values === undefined)
       continue;
+    const lowerName = name.toLowerCase();
     if (separator) {
-      const sep = name.toLowerCase() === 'set-cookie' ? setCookieSeparator : separator;
-      for (const value of values.split(sep!))
-        result.push({ name, value: value.trim() });
+      if (lowerName === 'set-cookie') {
+        const cookies = splitSetCookieString(values, setCookieSeparator);
+        for (const cookie of cookies)
+          result.push({ name, value: cookie });
+      } else if (singleValuedHeaders.has(lowerName)) {
+        result.push({ name, value: values.trim() });
+      } else {
+        for (const value of values.split(separator))
+          result.push({ name, value: value.trim() });
+      }
     } else {
       result.push({ name, value: values });
     }
diff --git a/packages/playwright-core/src/server/firefox/ffNetworkManager.ts b/packages/playwright-core/src/server/firefox/ffNetworkManager.ts
index e17afd5c45e69..1a2da5c4a689a 100644
--- a/packages/playwright-core/src/server/firefox/ffNetworkManager.ts
+++ b/packages/playwright-core/src/server/firefox/ffNetworkManager.ts
@@ -15,6 +15,7 @@
  * limitations under the License.
  */
 
+import { singleValuedHeaders } from '@isomorphic/headers';
 import { eventsHelper } from '@utils/eventsHelper';
 import * as network from '../network';
 
@@ -280,10 +281,18 @@ class FFRouteImpl implements network.RouteDelegate {
 function parseMultivalueHeaders(headers: HeadersArray) {
   const result: HeadersArray = [];
   for (const header of headers) {
-    const separator = header.name.toLowerCase() === 'set-cookie' ? '\n' : ',';
-    const tokens = header.value.split(separator).map(s => s.trim());
-    for (const token of tokens)
-      result.push({ name: header.name, value: token });
+    const lowerName = header.name.toLowerCase();
+    if (lowerName === 'set-cookie') {
+      const tokens = header.value.split('\n').map(s => s.trim());
+      for (const token of tokens)
+        result.push({ name: header.name, value: token });
+    } else if (singleValuedHeaders.has(lowerName)) {
+      result.push({ name: header.name, value: header.value.trim() });
+    } else {
+      const tokens = header.value.split(',').map(s => s.trim());
+      for (const token of tokens)
+        result.push({ name: header.name, value: token });
+    }
   }
   return result;
 }
diff --git a/tests/library/unit/headers.spec.ts b/tests/library/unit/headers.spec.ts
new file mode 100644
index 0000000000000..60beea4245d4d
--- /dev/null
+++ b/tests/library/unit/headers.spec.ts
@@ -0,0 +1,99 @@
+/**
+ * Copyright (c) Microsoft Corporation.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+import { test as it, expect } from '@playwright/test';
+import { headersObjectToArray, splitSetCookieString, singleValuedHeaders } from '../../../packages/isomorphic/headers';
+
+it('should not split single-valued headers on comma', () => {
+  const headers = {
+    'Date': 'Fri, 11 Sep 2026 05:27:07 GMT',
+    'Last-Modified': 'Wed, 21 Oct 2026 07:28:00 GMT',
+    'Expires': 'Thu, 01 Dec 2026 16:00:00 GMT',
+    'Retry-After': 'Wed, 21 Oct 2026 07:28:00 GMT',
+    'Content-Type': 'text/html; charset=utf-8',
+    'Location': 'https://example.com/path,with,comma',
+    'User-Agent': 'Mozilla/5.0 (Windows NT 10.0; Win64; x64), TestBot/1.0',
+    'Vary': 'Accept-Encoding, User-Agent',
+    'Cache-Control': 'no-cache, no-store',
+  };
+
+  const result = headersObjectToArray(headers, ',');
+
+  expect(result.filter(h => h.name === 'Date')).toEqual([
+    { name: 'Date', value: 'Fri, 11 Sep 2026 05:27:07 GMT' }
+  ]);
+  expect(result.filter(h => h.name === 'Last-Modified')).toEqual([
+    { name: 'Last-Modified', value: 'Wed, 21 Oct 2026 07:28:00 GMT' }
+  ]);
+  expect(result.filter(h => h.name === 'Expires')).toEqual([
+    { name: 'Expires', value: 'Thu, 01 Dec 2026 16:00:00 GMT' }
+  ]);
+  expect(result.filter(h => h.name === 'Retry-After')).toEqual([
+    { name: 'Retry-After', value: 'Wed, 21 Oct 2026 07:28:00 GMT' }
+  ]);
+  expect(result.filter(h => h.name === 'Content-Type')).toEqual([
+    { name: 'Content-Type', value: 'text/html; charset=utf-8' }
+  ]);
+  expect(result.filter(h => h.name === 'Location')).toEqual([
+    { name: 'Location', value: 'https://example.com/path,with,comma' }
+  ]);
+  expect(result.filter(h => h.name === 'User-Agent')).toEqual([
+    { name: 'User-Agent', value: 'Mozilla/5.0 (Windows NT 10.0; Win64; x64), TestBot/1.0' }
+  ]);
+
+  // Multi-valued headers should still be split
+  expect(result.filter(h => h.name === 'Vary')).toEqual([
+    { name: 'Vary', value: 'Accept-Encoding' },
+    { name: 'Vary', value: 'User-Agent' },
+  ]);
+  expect(result.filter(h => h.name === 'Cache-Control')).toEqual([
+    { name: 'Cache-Control', value: 'no-cache' },
+    { name: 'Cache-Control', value: 'no-store' },
+  ]);
+});
+
+it('should handle Set-Cookie splitting correctly on macOS WebKit comma separator', () => {
+  // Single cookie with Expires containing a comma should stay intact
+  expect(splitSetCookieString('sid=1; Expires=Wed, 21 Oct 2026 07:28:00 GMT; Path=/', ',')).toEqual([
+    'sid=1; Expires=Wed, 21 Oct 2026 07:28:00 GMT; Path=/'
+  ]);
+
+  // Multiple cookies joined by comma with Expires should be split properly
+  const multiple = 'sid=1; Expires=Wed, 21 Oct 2026 07:28:00 GMT; Path=/, token=xyz; Secure, theme=dark';
+  expect(splitSetCookieString(multiple, ',')).toEqual([
+    'sid=1; Expires=Wed, 21 Oct 2026 07:28:00 GMT; Path=/',
+    'token=xyz; Secure',
+    'theme=dark',
+  ]);
+
+  // With standard newline separator
+  const newlineCookies = 'sid=1; Expires=Wed, 21 Oct 2026 07:28:00 GMT\ntoken=xyz';
+  expect(splitSetCookieString(newlineCookies, '\n')).toEqual([
+    'sid=1; Expires=Wed, 21 Oct 2026 07:28:00 GMT',
+    'token=xyz',
+  ]);
+});
+
+it('should contain all standard single-valued headers in set', () => {
+  expect(singleValuedHeaders.has('date')).toBe(true);
+  expect(singleValuedHeaders.has('last-modified')).toBe(true);
+  expect(singleValuedHeaders.has('expires')).toBe(true);
+  expect(singleValuedHeaders.has('if-modified-since')).toBe(true);
+  expect(singleValuedHeaders.has('if-unmodified-since')).toBe(true);
+  expect(singleValuedHeaders.has('retry-after')).toBe(true);
+  expect(singleValuedHeaders.has('content-type')).toBe(true);
+  expect(singleValuedHeaders.has('location')).toBe(true);
+});
diff --git a/tests/page/page-network-response.spec.ts b/tests/page/page-network-response.spec.ts
index 9ec3e8eb6121d..7ff8f8cc072e6 100644
--- a/tests/page/page-network-response.spec.ts
+++ b/tests/page/page-network-response.spec.ts
@@ -260,6 +260,36 @@ it('should report multiple set-cookie headers', async ({ page, server, isElectro
   expect(await response.headerValues('set-cookie')).toEqual(['a=b', 'c=d']);
 });
 
+it('should not split single-valued and http-date headers on comma', async ({ page, server }) => {
+  server.setRoute('/headers', (req, res) => {
+    res.writeHead(200, {
+      'Date': 'Fri, 11 Sep 2026 05:27:07 GMT',
+      'Last-Modified': 'Wed, 21 Oct 2026 07:28:00 GMT',
+      'Expires': 'Thu, 01 Dec 2026 16:00:00 GMT',
+      'Content-Type': 'text/plain; charset=utf-8',
+    });
+    res.end('ok');
+  });
+
+  await page.goto(server.EMPTY_PAGE);
+  const [response] = await Promise.all([
+    page.waitForResponse('**/*'),
+    page.evaluate(() => fetch('/headers'))
+  ]);
+  const headers = await response.headersArray();
+  const lastModified = headers.filter(h => h.name.toLowerCase() === 'last-modified');
+  expect(lastModified).toHaveLength(1);
+  expect(lastModified[0].value).toBe('Wed, 21 Oct 2026 07:28:00 GMT');
+
+  const date = headers.filter(h => h.name.toLowerCase() === 'date');
+  expect(date).toHaveLength(1);
+  expect(date[0].value).toBe('Fri, 11 Sep 2026 05:27:07 GMT');
+
+  const expires = headers.filter(h => h.name.toLowerCase() === 'expires');
+  expect(expires).toHaveLength(1);
+  expect(expires[0].value).toBe('Thu, 01 Dec 2026 16:00:00 GMT');
+});
+
 it('should behave the same way for headers and allHeaders', async ({ page, server, browserName, platform }) => {
   it.skip(browserName === 'webkit' && platform === 'win32', 'libcurl does not support non-set-cookie multivalue headers');
   server.setRoute('/headers', (req, res) => {