[BUG] Terminal flickering and scrollbar rapid resizing when output exceeds window height

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?

## Terminal flickering and scrollbar rapid resizing when output exceeds window height

Version: 2.0.30 (regression started in 2.0.29)

Environment:

• Terminal: GNOME Terminal 3.52.0
• VTE Library: 0.76.0 (+BIDI +GNUTLS +ICU +SYSTEMD)
• TERM: xterm-256color
• Shell: bash
• OS: Ubuntu Linux (6.8.0 kernel)
• Terminal Window Size: 24 rows × 80 columns
• Locale: C.UTF-8

Critical Trigger Condition:

• Only occurs when Claude output exceeds terminal window height (24 lines)
• Output gets split across multiple screens
• Not related to total session size or conversation history length
• Workaround tested (limiting scrollback to 1000 lines) - no effect

Symptoms:

1. Terminal Scrollbar Flickering:

• Scrollbar rapidly alternates between full height (no scrolling) and normal size
• Creates visible flashing/flickering effect while streaming output
• Suggests terminal buffer being repeatedly cleared and re-rendered

1. Input Lag:

• Keyboard input becomes slow and unresponsive during output streaming
• Noticeable delay between keypress and character appearance

1. Intermittent Behavior:

• Issue comes and goes within the same session
• Not constant - appears to be cyclical

Reproduction Steps:

1. Open GNOME Terminal
2. Start Claude Code session
3. Request a task/prompt that produces output exceeding 24 lines
4. Observe scrollbar flickering while output streams
5. Try typing during output - input lag will be apparent

Expected Behavior:
Terminal should render streaming output smoothly without flickering. Scrollbar should remain stable. Input should stay
responsive.

Root Cause Hypothesis:
Claude Code v2.0.29+ appears to be issuing terminal control sequences that:

• Clear or reset the terminal buffer during streaming output
• Immediately re-render content
• Cause VTE (GNOME Terminal's rendering library) to recalculate the scrollable region
• Only manifests when content spans multiple terminal heights

Additional Notes:

• Issue does not occur with shorter outputs that fit in terminal window
• Scrollbar behavior (expanding to full height, then shrinking back) is the key visual symptom
• Appears to be related to how output buffering/rendering is handled during streaming

What Should Happen?

formulate the lines 1 by 1

Error Messages/Logs

Steps to Reproduce

write a lot of output lines. Session is already very old and use /resume every time

Claude Model

Sonnet (default)

Is this a regression?

Yes, this worked in a previous version

Last Working Version

2.0.28

Claude Code Version

2.0.29/30/31

Platform

Anthropic API

Operating System

Ubuntu/Debian Linux

Terminal/Shell

Xterm

Additional Information

_No response_