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Browser Use broken after today update: no node_repl/js or no Codex IAB backend discovered #20579

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Browser Use broken after today update: no node_repl/js or no Codex IAB backend discovered#20579
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appIssues related to the Codex desktop appapp-serverIssues involving app server protocol or interfacesbrowserbugSomething isn't workingmcpIssues related to the use of model context protocol (MCP) serversskillsIssues related to skills

Description

@jmzafrass
jmzafrass
opened on May 1, 2026

After today's Codex Desktop update, Browser Use appears broken in Codex Desktop on macOS.

Feedback ID from in-app feedback upload:
019de282-b494-7540-9862-e62162726343

What happened:

  • I had the Codex in-app browser open on a local dev server: http://localhost:3000/.
  • I asked Codex to use @Browser / Browser Use to navigate and log into a local app.
  • The main thread could not use Browser Use because the required Node REPL execution tool was not exposed. Tool discovery for mcp__node_repl__js, node_repl js, and js only surfaced unrelated tools such as Vercel/Figma/Computer Use.
  • After reinstalling Browser Use and retrying in another thread, mcp__node_repl__js became available, but Browser Use still failed to connect to the in-app browser backend.

Exact backend error observed in the separate thread:

Failed to connect to browser-use backend "iab". No Codex IAB backends were discovered.

Expected behavior:

  • Browser Use should expose the Node REPL js tool required by the Browser skill.
  • Browser Use should discover the Codex in-app browser backend (iab).
  • Codex should be able to run the normal Browser Use bootstrap:
const { setupAtlasRuntime } = await import("<plugin root>/scripts/browser-client.mjs");
await setupAtlasRuntime({ globals: globalThis, backend: "iab" });
const tab = await agent.browser.tabs.selected();

Actual behavior:

  • In one thread the required mcp__node_repl__js tool was not exposed at all.
  • In another thread, the tool existed but Browser Use failed with No Codex IAB backends were discovered.
  • Computer Use cannot be used as a workaround because it is blocked from controlling the Codex app itself.

Impact:

  • Browser Use cannot drive the Codex in-app browser for local frontend QA.
  • This blocks visual iteration flows that depend on @Browser for localhost apps.

Environment:

  • Codex Desktop app on macOS.
  • Browser Use plugin reinstalled before retrying.
  • Local app was reachable at http://localhost:3000/ from the in-app browser.

Activity

  1. github-actions
    added
    bugSomething isn't working
    appIssues related to the Codex desktop app
    skillsIssues related to skills
    mcpIssues related to the use of model context protocol (MCP) servers
    app-serverIssues involving app server protocol or interfaces
    on May 1, 2026

  2. github-actions commented on May 1, 2026

    @github-actions
    github-actionsbot
    on May 1, 2026 – with GitHub Actions
    Contributor

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

    Powered by Codex Action

  3. nullasi commented on May 1, 2026

    @nullasi
    nullasi
    on May 1, 2026

    same

  4. wangyifan1004 commented on May 1, 2026

    @wangyifan1004
    wangyifan1004
    on May 1, 2026 – with ChatGPT Codex Connector

    I can reproduce this on Windows after restarting Codex Desktop.

    Environment:

    • Platform: Windows x64
    • Codex Desktop package observed locally: OpenAI.Codex_26.429.2026.0_x64__2p2nqsd0c76g0
    • Browser Use plugin: openai-bundled/browser-use/0.1.0-alpha1
    • Backend requested: iab

    What happened:

    1. The in-app browser was open and could manually load an external page.
    2. Before restart, Browser Use could not run because the Node REPL js entrypoint was not actually usable (unsupported call: mcp__node_repl__js).
    3. After restarting Codex Desktop, the Node REPL js tool became available, but Browser Use still failed during setupAtlasRuntime({ globals: globalThis, backend: "iab" }).

    Actual error after restart:

    Failed to connect to browser-use backend "iab". No Codex IAB backends were discovered. Discovery diagnostics: listedPipes=2, candidates=4, browsers=0, iabBrowsers=0, failures=["discovered/timeout","discovered/timeout","legacy-iab/timeout","legacy-chrome/timeout"], pipeListingError=none.

    Expected:
    Browser Use should discover the currently open Codex in-app browser backend and allow selecting/screenshotting the current tab.

    Notes:

    • This does not appear to be a website-specific problem; the page was already open manually in the in-app browser.
    • The failure happens before tab selection or screenshot.

  5. alex-vance commented on May 1, 2026

    @alex-vance
    alex-vance
    on May 1, 2026

    I can reproduce the "no node_repl/js tool exposed" variant on macOS.

    Environment:

    • Platform: Darwin 25.3.0 arm64 arm
    • Codex CLI: codex-cli 0.128.0
    • ~/.codex/version.json: latest_version 0.128.0
    • Browser Use plugin: openai-bundled/browser-use/0.1.0-alpha1

    Observed:

    • ~/.codex/config.toml has [plugins."browser-use@openai-bundled"] enabled = true
    • The Browser Use skill requires mcp__node_repl__js
    • Tool discovery for node_repl js, mcp__node_repl__js, js, and js_reset did not expose a Node REPL execution tool
    • codex mcp list does not show a node_repl server
    • codex mcp get node_repl returns:
    Error: No MCP server named 'node_repl' found.

    Additional note:
    The installed Browser Use plugin bundle has no .mcp.json, so enabling Browser Use does not appear to start/provide the Node REPL MCP server itself. It seems to rely on a platform-provided Node REPL tool, but that tool is not available in this session.

  6. wodenwang commented on May 2, 2026

    @wodenwang
    wodenwang
    on May 2, 2026

    when fixed?

  7. etraut-openai
    added
    browser
    on May 3, 2026

  8. neokry commented on May 5, 2026

    @neokry
    neokry
    on May 5, 2026

    I reproduced the Browser Use side of this on Codex Desktop macOS with openai-bundled/browser-use/0.1.0-alpha1.

    The Browser Use bootstrap attempted:

    setupAtlasRuntime({ globals: globalThis, backend: "iab" })

    It failed before navigation with:

    Failed to connect to browser-use backend "iab". No Codex IAB backends were discovered.

    In the same run, falling back to plain Playwright could open the local app at http://127.0.0.1:5123/, so the local server/page itself was reachable. This looks like IAB backend discovery/registration rather than a local app or network problem.

  9. PennyVibe commented on May 7, 2026

    @PennyVibe
    PennyVibe
    on May 7, 2026

    I can still reproduce this on macOS after reinstalling the Browser Use plugin and restarting Codex Desktop.

    Environment:

    • Codex Desktop on macOS
    • Browser Use plugin: openai-bundled/browser-use/0.1.0-alpha1
    • Backend requested: iab
    • Local app manually open in the Codex in-app browser: http://localhost:8080/#/

    Observed sequence:

    1. Before restarting, Browser Use could not run because the Node REPL execution tools were not exposed in the current request:
      • mcp__node_repl__js unavailable
      • mcp__node_repl__js_reset unavailable
    2. After restarting Codex, tool discovery exposed Node REPL again:
      • mcp__node_repl__.js
      • mcp__node_repl__.js_reset
    3. After resetting the JS kernel and running the normal Browser Use bootstrap, IAB discovery still failed before tab selection/navigation.

    Bootstrap attempted:

    const { setupAtlasRuntime } = await import('/Users/ylp/.codex/plugins/cache/openai-bundled/browser-use/0.1.0-alpha1/scripts/browser-client.mjs');
const backend = 'iab';
await setupAtlasRuntime({ globals: globalThis, backend });

    Actual error:

    Failed to connect to browser-use backend "iab". No Codex IAB backends were discovered. Discovery diagnostics: listedPipes=4, candidates=6, browsers=0, iabBrowsers=0, failures=["discovered/timeout","discovered/timeout","discovered/timeout","discovered/timeout","legacy-iab/timeout","legacy-chrome/timeout"], pipeListingError=none.

    Notes:

    • The in-app browser itself was visible and could manually load the local app.
    • The failure happens during IAB backend discovery, before agent.browser.tabs.selected() can read the current tab.
    • As a workaround, chrome_devtools could open and inspect http://localhost:8080/#/device-group, so the local frontend server and page were reachable. This looks specific to Codex IAB backend discovery/registration rather than the target URL.

  10. abhishek944 commented on May 12, 2026

    @abhishek944
    abhishek944
    on May 12, 2026

    Hi,
    Any update here? I am also facing the same issue.

  11. nullasi commented on May 12, 2026

    @nullasi
    nullasi
    on May 12, 2026

    browserAgentAvailable = inAppBrowserEnabled && statsigGate && browserUseFeatureEnabled && RUN_CODEX_IN_WSL !== true
    These are the conditions specified in the source code. browseruse can only be used if all of them are satisfied.

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