[Windows] In-app browser device preview toolbar closes when Browser Use returns control

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Assessment

Difficulty
4/5
Estimated time
3-5 days
Newbie friendliness
45/100
Issue type
Bug
Clarity
Mostly clear
Activity status
Quiet
Domain
desktop

Research direction

Start by reproducing the Browser Use viewport change at 393 × 852 and trace the device-preview toolbar state when control returns to the user, including the case without tabs.finalize(). Done means the user- or agent-selected preview remains visibly active until explicitly reset.

Written by the indexing model from the issue text.

Description

app browser bug windows-os
Codex App version

Microsoft Store package version 26.715.3651.0 on Windows x64.

What issue are you seeing?

When Browser Use sets the in-app browser to an iPhone-sized responsive/device preview (393 × 852), the preview works while the agent controls the browser, but the visible device-preview toolbar closes again as soon as the Browser Use step ends and control returns to the user.

This also reproduced when the agent deliberately did not call tabs.finalize(). During the active Browser Use call, page evaluation confirmed:

  • window.innerWidth === 393
  • window.innerHeight === 852

After the tool call returned, the user observed the device-preview toolbar close again.

Steps to reproduce
  1. Open a local web page in the Codex in-app browser.
  2. Start Browser Use and set the browser viewport: 
    await viewport.set({ width: 393, height: 852 })
  3. With the tab claimed, reload if necessary and verify the page viewport is 393 × 852.
  4. End the Browser Use tool call and return control to the user.
  5. Observe that the visible responsive/device-preview toolbar closes or is no longer visibly pinned.
  6. Repeat without calling browser.tabs.finalize(...); the same behavior occurs.
Expected behavior

The user-selected or agent-set device preview should remain visibly active until the user or agent explicitly resets it.

Actual behavior

The device preview is temporary to the Browser Use control step. Its toolbar is dismissed when control returns, so the agent cannot leave the requested iPhone preview visibly pinned for the user.

Additional context

The first reproduction used tabs.finalize(), which also closed the toolbar. A second reproduction intentionally omitted finalization, but the toolbar still closed after the Browser Use call ended.

I searched existing issues before filing. Issues such as #28062 cover different device-toolbar problems (for example, blank zoom options), not this toolbar-lifecycle/persistence behavior.

Dominant language
Rust
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