Browser Use fails on Windows Codex Desktop: failed to start codex app-server (os error 3)

[bboerni2]

Summary

On Codex Desktop for Windows, the Browser Use / in-app browser integration can detect the selected in-app browser tab, but real browser operations fail with:

failed to start codex app-server: Das System kann den angegebenen Pfad nicht finden. (os error 3)

Environment

• OS: Windows
• Codex Desktop
• App version seen in logs: 0.125.0-alpha.3
• Installed package path/version seen locally: OpenAI.Codex_26.422.8496.0_x64__2p2nqsd0c76g0
• Browser Use plugin: openai-bundled/browser-use/0.1.0-alpha1

What works

• Basic node_repl execution works.
• browser-client.mjs exists and imports successfully.
• setupAtlasRuntime({ globals: globalThis, backend: "iab" }) succeeds.
• agent.browser.tabs.selected() can read the current in-app browser tab title/url.

Example successful selected-tab read:

{"title":"Example Domain","url":"https://example.com/"}

What fails

The following fail with the codex app-server path error:

• agent.browser.tabs.new()
• tab.goto(...)
• tab.playwright.domSnapshot()

Minimal repro

const { setupAtlasRuntime } = await import('file:///<redacted-user-home>/.codex/plugins/cache/openai-bundled/browser-use/0.1.0-alpha1/scripts/browser-client.mjs');
await setupAtlasRuntime({ globals: globalThis, backend: 'iab' });
const tab = await agent.browser.tabs.selected();
await tab.playwright.domSnapshot();

Expected behavior

Browser Use should be able to inspect and control the selected in-app browser tab.

Actual behavior

failed to start codex app-server: Das System kann den angegebenen Pfad nicht finden. (os error 3)

Notes

A full Codex Desktop restart did not resolve the issue. After restart, PATH appeared to point to the current package version only (OpenAI.Codex_26.422.8496.0_x64__2p2nqsd0c76g0). Before restart, there appeared to be an older package version in PATH as well, but the error persisted after that was cleaned up by restart.

This reproduces on https://example.com/, so it is not site-specific.

[github-actions]

Potential duplicates detected. Please review them and close your issue if it is a duplicate.

• Windows: browser-use IAB can initialize and list tabs, but tab.goto() fails with failed to start codex app-server: 系统找不到指定的路径 (os error 3) #20130
• Browser Use IAB backend can see selected tab but cannot control it on Windows #19298
• Windows Codex Desktop Browser Use fails to start app-server despite working npm CLI #20048
• Codex Desktop IAB cannot inspect external pages because app-server fails to start on Windows #19423
• Windows browser-use external navigation fails when Codex helper bin path is missing #19562

Powered by Codex Action

[Toshi3886]

I can reproduce the same issue on another Windows machine, with the Japanese localized error message.

Environment

• OS: Windows 10.0.26100, x64
• Codex Desktop app package: OpenAI.Codex_26.422.8496.0_x64__2p2nqsd0c76g0
• Codex Desktop Codex.exe product version: 26.422.62136
• Bundled CLI/app-server: 0.126.0-alpha.8
• Browser Use plugin: openai-bundled/browser-use/0.1.0-alpha1

What works

The in-app browser bridge can initialize and read the selected blank tab:

const { setupAtlasRuntime } = await import(
  'C:/Users/<USER>/.codex/plugins/cache/openai-bundled/browser-use/0.1.0-alpha1/scripts/browser-client.mjs'
);

await setupAtlasRuntime({ globals: globalThis, backend: 'iab' });
globalThis.tab = await agent.browser.tabs.selected();

nodeRepl.write(JSON.stringify({
  title: await tab.title(),
  url: await tab.url()
}));

Result:

{"title":"New page","url":"about:blank"}

On about:blank, tab.playwright.domSnapshot() also succeeds and returns an empty snapshot:

{"ok":true,"length":0,"sample":""}

What fails

Both external navigation and nodeRepl.fetch(...) fail immediately:

await tab.goto('https://mail.google.com/mail/u/0/#search/in%3Ainbox+before%3A2026%2F04%2F01', {
  waitUntil: 'domcontentloaded',
  timeout: 30000
});

const res = await nodeRepl.fetch(
  'https://chatgpt.com/backend-api/aura/site_status?site_url=https%3A%2F%2Fmail.google.com'
);

Observed localized error:

Error: failed to start codex app-server: 指定されたパスが見つかりません。 (os error 3)
    at C:\Users\<USER>\AppData\Local\Temp\<TMP>\kernel.js:1675:18
    at handleAuthenticatedFetchResult (C:\Users\<USER>\AppData\Local\Temp\<TMP>\kernel.js:1931:5)
    at handleInputLine (C:\Users\<USER>\AppData\Local\Temp\<TMP>\kernel.js:2008:5)
    at handleInputFrame (C:\Users\<USER>\AppData\Local\Temp\<TMP>\kernel.js:2048:3)

Desktop log evidence

The desktop log shows the app-server transport started and reports version 0.126.0-alpha.8:

info [AppServerConnection] Initializing app-server transport
info [AppServerConnection] Starting app-server connection hostId=local transport=stdio
info [AppServerConnection] Current reported app-server version: currentVersion=0.126.0-alpha.8 hostId=local

The bundled Browser Use plugin is also present/forced:

info [BundledPluginsMarketplace] bundled_plugins_marketplace_sync_started disabledInstalledPluginCount=0 enabledPluginNames=["browser-use","latex-tectonic"] forceInstallPluginNames=["browser-use"]
info [BundledPluginsMarketplace] bundled_plugin_install_requested pluginName=browser-use reason=forced

The native browser-use pipe and IAB tab mapping are created:

info [browser-use-native-pipe-server] browser-use native pipe listening pipePath=\\.\pipe\codex-browser-use\<UUID>
info [browser-use-iab-api] IAB_LIFECYCLE iab createTab mapped page to tab conversationId=<THREAD_ID> pageKey=1:<THREAD_ID> routeKey=1:<THREAD_ID> tabId=1 turnId=<TURN_ID> webContentsId=3
info [browser-use-iab-api] IAB_LIFECYCLE registered debugger listener pageKey=1:<THREAD_ID> routeKey=1:<THREAD_ID> tabId=1 webContentsId=3

Process evidence

The app-server process was observed running:

Name: codex.exe
ExecutablePath: C:\Program Files\WindowsApps\OpenAI.Codex_26.422.8496.0_x64__2p2nqsd0c76g0\app\resources\codex.exe
CommandLine: "...\app\resources\codex.exe" app-server --analytics-default-enabled

Workaround

A separate Playwright MCP browser can open the same external Gmail URL successfully. So the network/page itself is not the blocker; this appears isolated to the Codex in-app browser / Browser Use app-server bridge.

[Rainson12]

I experience the same error. According to codex debugging itself:

I checked the Browser Use client bundle. There is no normal filesystem path for app-server in browser-client.mjs, and it does not look like something solved by setting PATH.

What the client actually uses on Windows is named pipes:

\\.\pipe\codex-browser-use-iab
\\.\pipe\codex-browser-use
\\.\pipe\codex-browser-use\*
I also checked your machine and these pipes exist:

codex-browser-use\5b2d8b00-7459-42ec-b162-2a4568648804
codex-browser-use\df397824-ffd2-422f-860e-75947e30f318
codex-browser-use\ee81fc03-8c3c-4db5-a5f4-c1e49884acab
codex-browser-use\ffa645a1-46ba-49c8-ace5-bbdd00cc37e2
So the Browser Use client can connect to the Codex/IAB backend. That matches what we saw: tabs.list() works.

The failing message:

failed to start codex app-server: Das System kann den angegebenen Pfad nicht finden. (os error 3)
is coming from the backend after connection, when it tries to start some internal Codex app-server component for navigation/DOM/screenshot work. The exact missing filesystem path is not included in the error returned to me.

The stack I can see points only to the temporary Node REPL kernel:

C:\Users\USERNAME\AppData\Local\Temp\.tmpe2NUJW\kernel.js
That is just the REPL runtime, not the missing app-server path.

So: I don’t think a PATH variable is the fix unless the Codex app-server internally shells out to something by name, but the available error does not expose that. More likely this is a Codex Desktop / Browser Use plugin packaging or runtime-location issue: the backend is reachable, but the app-server binary/folder it expects is missing or not where the backend thinks it is.

[7hcy9xqq7q-dotcom]

I’m also seeing this on Windows Codex Desktop.

The in-app browser opens, but Codex fails when trying to inspect or control it with:
failed to start codex app-server: The system cannot find the path specified. (os error 3)