[P0] Terminal resize causes prior assistant output to re-render and duplicate, destroying scrollback

Summary

When I resize my terminal window mid-session, Claude Code re-renders prior assistant output (especially long responses with markdown tables) at the new terminal width. The original output is not retained — instead, multiple re-rendered copies of the same content fill scrollback at progressively different widths, making it impossible to scroll up to recover the original message.

Severity

P0 for me — long sessions with substantive output (tables, code blocks, multi-section answers) become effectively unrecoverable after a single resize. The longer the answer, the more catastrophic the breakage. Each subsequent resize makes scrollback worse.

Steps to reproduce

1. Have Claude produce a long response containing markdown tables (or any wrapped content)
2. Resize the terminal window (drag corner, or change tmux/iTerm pane width)
3. Try to scroll up to read the original response

Expected

Historical output stays statically rendered at its original width. Only the active input prompt area should reflow on resize.

Actual

• Prior assistant output is re-laid-out at the new width and re-emitted into scrollback
• Each subsequent resize emits another copy
• Scrollback fills with duplicated, slightly-different-width versions of the same response
• Tables and other structured content become unreadable
• The original response cannot be recovered for reference

Environment

• Platform: macOS (Darwin 25.4.0)
• Shell: zsh
• Model: Opus 4.7

Why this is high impact

Long-form outputs with tables (e.g. financial reconciliations, audit reports, file listings) are exactly the kind of content users need to scroll back to. This bug specifically punishes the responses where scrollback fidelity matters most.