bug: Terminal renders duplicate content blocks in dashboard

[waleedkadous]

Bug

The dashboard terminal frequently renders content twice — entire blocks of text appear duplicated, overlapping previous content. This is different from the scroll-to-top bug (#630) which was fixed.

Screenshot

See conversation — the same diff output and Claude Code TUI elements render twice on screen.

Symptoms

• Entire content blocks appear duplicated vertically
• Text from different render passes overlaps
• Happens during normal Claude Code usage (processing, displaying diffs)
• Hitting refresh doesn't reliably fix it

Likely Causes

1. Replay buffer duplication: WebSocket replay may be sending content that was already written to xterm.js
2. xterm.js reflow bug: Terminal column mismatch causing content to wrap and appear duplicated when the TUI redraws
3. Claude Code TUI redraw: Program writes content for wrong terminal width, xterm wraps it creating apparent duplicates

Not the cause

• ESC[3J (already blocked in rc.6)
• Scroll-to-top (fixed in Bug: Terminal scroll-to-top caused by xterm parsing errors and WebGL context loss #630)
• Terminal state corruption (soft reset sequences don't help)

Environment

• codev v3.0.0-rc.8
• xterm.js (dashboard)
• macOS