UI Bug: Copilot CLI output flickers/stutters constantly during text stream response #1599
Description
Describe the bug
When using the GitHub Copilot CLI in the terminal, the generated response text flickers, jumps, and stutters vertically as the words are being streamed onto the screen. It creates a very harsh visual "trembling" effect that makes it hard to read the text in real-time.
Affected version
GitHub Copilot CLI 0.0.414.
Steps to reproduce the behavior
To Reproduce
- Open the terminal (e.g., [iTerm2]).
- Run a query that generates a multi-line response or a code block (e.g.,
gh copilot suggest "How to truncate Postgres tables"). - Observe the output being streamed. You will notice the text jumping up and down rapidly before the line finishes rendering.
Expected behavior
The text should stream smoothly horizontally onto the screen without repainting conflicts or jumping vertically, similar to how standard tools or other AI CLI wrappers output standard stdout chunks.
Additional context
Environment Details
- OS: macOS [Tahoe 26.3]
- Terminal Emulator: [iTerm2 Build 3.6.6]
- Terminal Size: Standard window size variable.
- CLI Version:
gh copilot --version[CLI 0.0.414]
This seems to be related to how the CLI redraws/repaints the console lines, particularly when handling long outputs or calculating line wraps at the edge of the terminal window. Expanding the terminal window dynamically to full screen sometimes mitigates the issue, implying a line-wrapping math bug during cursor repositioning.
Screen Recording / Evidence
This short video demonstrates exactly the stuttering behavior when returning a large block of text or multi-line output.
[https://github.com/user-attachments/assets/6afa0c0e-c142-423e-9cdd-18bd247d8343]