[BUG]

Preflight Checklist

• [x] I have searched existing issues and this hasn't been reported yet
• [x] This is a single bug report (please file separate reports for different bugs)
• [x] I am using the latest version of Claude Code

What's Wrong?

Bug Description

Every time the Agent tool is invoked, a visible PowerShell/terminal popup window
appears on screen. This started ~June 9, 2026 and appears to be a regression —
subagents previously ran silently with no visible window.

Environment

• OS: Windows 11
• Claude Code version: latest (as of June 14, 2026)
• Shell: PowerShell

Steps to Reproduce

1. Open Claude Code on Windows 11
2. Trigger any task that internally uses the Agent tool
3. Observe a PowerShell popup window appearing for each subagent spawned

Expected Behavior

Subagents run silently in the background — no visible window.

Actual Behavior

Each Agent tool invocation opens a visible PowerShell popup window on screen.

Additional Context

Windows-specific regression. Started around June 9, 2026 (~5 days before filing).

What Should Happen?

Bug Description

Every time the Agent tool is invoked, a visible PowerShell/terminal popup window
appears on screen. This started ~June 9, 2026 and appears to be a regression —
subagents previously ran silently with no visible window.

Environment

• OS: Windows 11
• Claude Code version: latest (as of June 14, 2026)
• Shell: PowerShell

Steps to Reproduce

1. Open Claude Code on Windows 11
2. Trigger any task that internally uses the Agent tool
3. Observe a PowerShell popup window appearing for each subagent spawned

Expected Behavior

Subagents run silently in the background — no visible window.

Actual Behavior

Each Agent tool invocation opens a visible PowerShell popup window on screen.

Additional Context

Windows-specific regression. Started around June 9, 2026 (~5 days before filing).

Error Messages/Logs

## Bug Description

Every time the Agent tool is invoked, a visible PowerShell/terminal popup window
appears on screen. This started ~June 9, 2026 and appears to be a regression —
subagents previously ran silently with no visible window.

## Environment
- OS: Windows 11
- Claude Code version: latest (as of June 14, 2026)
- Shell: PowerShell

## Steps to Reproduce
1. Open Claude Code on Windows 11
2. Trigger any task that internally uses the Agent tool
3. Observe a PowerShell popup window appearing for each subagent spawned

## Expected Behavior
Subagents run silently in the background — no visible window.

## Actual Behavior
Each Agent tool invocation opens a visible PowerShell popup window on screen.

## Additional Context
Windows-specific regression. Started around June 9, 2026 (~5 days before filing).

Steps to Reproduce

Bug Description

Every time the Agent tool is invoked, a visible PowerShell/terminal popup window
appears on screen. This started ~June 9, 2026 and appears to be a regression —
subagents previously ran silently with no visible window.

Environment

• OS: Windows 11
• Claude Code version: latest (as of June 14, 2026)
• Shell: PowerShell

Steps to Reproduce

1. Open Claude Code on Windows 11
2. Trigger any task that internally uses the Agent tool
3. Observe a PowerShell popup window appearing for each subagent spawned

Expected Behavior

Subagents run silently in the background — no visible window.

Actual Behavior

Each Agent tool invocation opens a visible PowerShell popup window on screen.

Additional Context

Windows-specific regression. Started around June 9, 2026 (~5 days before filing).

Claude Model

Sonnet (default)

Is this a regression?

Yes, this worked in a previous version

Last Working Version

5 days ago, same version

Claude Code Version

current

Platform

Anthropic API

Operating System

Windows

Terminal/Shell

Terminal.app (macOS)

Additional Information

_No response_