Split view display bug: response content duplicated above and below prompt since v2.1.119 — severe productivity impact in WSL Ubuntu

Summary

Since approximately 2 days ago (correlating with version 2.1.119), Claude Code started showing a split-view display where the response content appears duplicated: once in the scrollback area (above the separator line) and again below the > input prompt. This happens consistently across all terminal sessions from the very first message — it is not related to session length.

Environment

• Claude Code version: 2.1.119
• OS: Ubuntu (WSL2 on Windows)
• Terminal: Windows Terminal → WSL
• Install method: global npm
• TERM: xterm-256color

Behavior

After Claude responds, the terminal shows:

[... response content scrolled into history ...]

* Churned for 37s
──────────────────────────────────────────────────
> |
? for shortcuts

[... SAME response content repeated below the prompt ...]

The response is cut at the terminal viewport boundary and the bottom portion appears again below the > input area — even though the same content is already visible in the scrollback above.

Root cause (identified)

Inspecting ~/.claude.json, the GrowthBook feature flag tengu_streaming_tool_execution2 is set to true. This flag appears to have been enabled in a server-side rollout approximately 2 days ago. Before that, this behavior did not occur.

Impact

This is causing severe productivity loss. Every response looks fragmented and repeated — it is extremely confusing to read, especially during long collaborative sessions. The user is seriously considering abandoning Claude Code entirely due to this issue.

The problem persists across all new sessions, all terminal windows, and cannot be worked around via configuration (verbose, showSpinnerTree: false, etc. — all already checked).

Steps to reproduce

1. Run Claude Code 2.1.119 on WSL Ubuntu
2. Start any interactive session
3. Ask any question that produces a response longer than ~10 lines
4. Observe: response content appears both in scrollback AND below the > prompt

Expected behavior

Response content should appear once, in the scrollback area. The input prompt area should remain clean.

Request

• Disable or provide an opt-out for tengu_streaming_tool_execution2 split-view behavior
• Or provide a configuration option to revert to the previous single-stream display

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Reported via Claude Code session by user CadarnDigital