[BUG] `claude agents` session attachment causes constant screen flickering on Windows ARM (Parallels) — regular `claude` sessions unaffected

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?

When entering a session from claude agents (agent view), the screen flickers constantly — including while typing in the input area. Regular claude sessions have zero flickering on the same machine. The flickering is isolated to sessions entered via claude agents, which suggests the agent view's rendering path is doing something different (likely more frequent or larger redraws) that triggers the flicker.

What Should Happen?

No flicker

Error Messages/Logs

Steps to Reproduce

1. Run claude agents
2. Enter any session
3. Observe constant flickering, including while typing

Claude Model

Opus

Is this a regression?

I don't know

Last Working Version

_No response_

Claude Code Version

2.1.144

Platform

Anthropic API

Operating System

macOS

Terminal/Shell

Windows Terminal

Additional Information

Tested across six different terminals on Windows — all flicker identically in agent view, none flicker in regular claude sessions. This rules out any terminal-specific rendering cause.

Environment:

• Claude Code: v2.1.144
• macOS host: MacBook Pro M4
• VM: Parallels Desktop (latest), Windows 11 ARM (10.0.26200)
• Parallels Tools: latest, matching host version

Terminals tested (all flicker in agent view, none in regular sessions):

• Windows Terminal
• PowerShell (pwsh)
• Git CMD
• Alacritty
• WezTerm
• Ghostty on macOS — no flicker (only terminal without the issue)

Does NOT reproduce:

• Regular claude sessions on the same Windows VM — no flicker
• claude agents on macOS (Ghostty terminal) — no flicker

Workarounds attempted (none helped):

• "tui": "fullscreen" in settings.json
• CLAUDE_CODE_NO_FLICKER=1 env var
• "prefersReducedMotion": true
• "spinnerTipsEnabled": false
• Windows Terminal: "useAtlasEngine": false, "compatibility.disablePartialInvalidation": true, "compatibility.enableUnfocusedAcrylic": false, "useAcrylic": false, "opacity": 100
• Parallels: switched display from "Best for Retina" to "Scaled"
• Parallels Tools: confirmed latest version