From bc22d1b80c0fa40c870eed42db48ed1985cd2eb6 Mon Sep 17 00:00:00 2001
From: Alex Rudenko <alexrudenko@chromium.org>
Date: Tue, 7 Oct 2025 15:23:08 +0200
Subject: [PATCH] fix: change default screen size in headless

---
 README.md             | 2 +-
 src/browser.ts        | 3 +++
 src/cli.ts            | 2 +-
 tests/browser.test.ts | 8 ++++----
 4 files changed, 9 insertions(+), 6 deletions(-)

diff --git a/README.md b/README.md
index 4a9f6f5bc..e083f1c8b 100644
--- a/README.md
+++ b/README.md
@@ -280,7 +280,7 @@ The Chrome DevTools MCP server supports the following configuration option:
   - **Type:** string
 
 - **`--viewport`**
-  Initial viewport size for the Chrome instances started by the server. For example, `1280x720`
+  Initial viewport size for the Chrome instances started by the server. For example, `1280x720`. In headless mode, max size is 3840x2160px.
   - **Type:** string
 
 - **`--proxyServer`**
diff --git a/src/browser.ts b/src/browser.ts
index d5a17e177..5387b3eff 100644
--- a/src/browser.ts
+++ b/src/browser.ts
@@ -99,6 +99,9 @@ export async function launch(options: McpLaunchOptions): Promise<Browser> {
   if (customDevTools) {
     args.push(`--custom-devtools-frontend=file://${customDevTools}`);
   }
+  if (headless) {
+    args.push('--screen-info={3840x2160}');
+  }
   let puppeteerChannel: ChromeReleaseChannel | undefined;
   if (!executablePath) {
     puppeteerChannel =
diff --git a/src/cli.ts b/src/cli.ts
index 85fcf839f..909d1a21e 100644
--- a/src/cli.ts
+++ b/src/cli.ts
@@ -65,7 +65,7 @@ export const cliOptions = {
   viewport: {
     type: 'string',
     describe:
-      'Initial viewport size for the Chrome instances started by the server. For example, `1280x720`',
+      'Initial viewport size for the Chrome instances started by the server. For example, `1280x720`. In headless mode, max size is 3840x2160px.',
     coerce: (arg: string | undefined) => {
       if (arg === undefined) {
         return;
diff --git a/tests/browser.test.ts b/tests/browser.test.ts
index 3dc8eff04..b4811202b 100644
--- a/tests/browser.test.ts
+++ b/tests/browser.test.ts
@@ -52,8 +52,8 @@ describe('browser', () => {
       userDataDir: folderPath,
       executablePath: executablePath(),
       viewport: {
-        width: 700,
-        height: 500,
+        width: 1501,
+        height: 801,
       },
     });
     try {
@@ -62,8 +62,8 @@ describe('browser', () => {
         return {width: window.innerWidth, height: window.innerHeight};
       });
       assert.deepStrictEqual(result, {
-        width: 700,
-        height: 500,
+        width: 1501,
+        height: 801,
       });
     } finally {
       await browser.close();