Scrollback duplication in VS Code integrated terminal (assistant messages and prompt line repeat 2-3×)

Summary

In long-running sessions inside the VS Code integrated terminal, assistant messages plus the input prompt line (>) get re-rendered 2–3 times in the scrollback. The underlying conversation is unaffected — the session JSONL contains the turn only once, so it's a pure rendering artifact.

This looks like a regression (or partial coverage) of the 2.1.116 fix:

Fixed scrollback duplication in inline mode where resizing the terminal or large output bursts would repeat earlier conversation history

Environment

• Claude Code: 2.1.118
• macOS: 26.2 (Darwin 25.2.0)
• VS Code: integrated terminal (latest stable)
• Shell: zsh
• Session: ~3h long, ~68k tokens, Opus 4.7 (1M context), \"bypass permissions\" mode
• Mode indicator showed [Timeout] in the status line at the time

Repro

1. Open VS Code integrated terminal, start claude
2. Run a long session with a few large outputs (Bash with sizable JSON, multi-paragraph assistant replies)
3. Let the session idle past the timeout indicator ([Timeout] appears under the model name)
4. Continue the conversation
5. Earlier assistant messages and the prompt line > re-appear 2–3 times in scrollback above the current turn

Cmd+K (clear terminal scrollback) makes them disappear, confirming the conversation state is correct and only the rendering is duplicated.

Expected

Each turn renders once.

Actual

Same assistant message + prompt line render 2–3× in a row.

Notes

• Not reproducible in non-VS-Code terminals (have not yet verified — will update if I test iTerm/Ghostty)
• Appears to be triggered after [Timeout] re-entry into the session, possibly combined with large output bursts
• Session journal (~/.claude/projects/.../*.jsonl) shows the turn exactly once