CLAUDE_CODE_NO_FLICKER=1 causes duplicated output and garbled Unicode on Windows

Found 3 possible duplicate issues:

1. https://github.com/anthropics/claude-code/issues/42406
2. https://github.com/anthropics/claude-code/issues/42417
3. https://github.com/anthropics/claude-code/issues/42482

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🤖 Generated with Claude Code

This is not a full duplicate of the three suggested issues. Here's why:

Bug 1 — Duplicated output is completely unique to this issue. None of #42406, #42417, or #42482 mention text appearing twice in a single response. This is a distinct rendering bug.

Bug 2 — Garbled Unicode is related but not identical:

• #42406 and #42417 are Japanese-locale specific (UTF-8 → CP932/Shift-JIS)
• #42482 is Korean-locale specific
• This issue affects box-drawing characters, which is a broader Unicode problem not tied to any specific CJK locale or codepage

All four issues share the same root cause area (NO_FLICKER renderer encoding on Windows), but this one covers a wider scope (non-CJK Unicode corruption) and reports an entirely separate bug (duplicated output) that the others don't.

Seeing the same garbled output on my end. Additional repro details:

Trigger sequence: Run /clear, then immediately run /review — the entire response renders as a wall of repeated àcŕàcŕàcŕ... characters (hundreds of them), ending with \\\\Γ¥. The text is completely unreadable.

This happens with both the POWERSHELL renderer and NO_FLICKER mode enabled. Disabling NO_FLICKER resolves it, consistent with what others are reporting.

Environment:

• Windows 11 Enterprise 10.0.26100
• Shell: bash (Git Bash)
• Terminal: Windows Terminal

The encoding corruption pattern (àcŕ repeating) looks like UTF-8 multi-byte sequences being split or reinterpreted mid-stream, possibly the alt-screen write path flushing partial codepoints when the buffer resets after /clear.

Adding context: I had CLAUDE_CODE_NO_FLICKER=1 set because the flickering/repainting during tool calls Meant that I would have to wait a long time for Claude to finish what he's doing before I could read what was written on the screen. — text jumping around makes it hard to follow what's happening. so the no flicker was much apprecialted.
However, I've now discovered it's causing full conversation re-renders after each tool call, with pre-tool text appearing twice, which doubles token usage in the display. the setup is Windows Terminal on Windows 1o SSH'd into a Linux machine, with Claude Code running on the Linux side. So the rendering/duplication issue is occurring through an SSH session in Windows Terminal, not a native Linux terminal. Might be relevant for diagnosing whether this is a Windows Terminal PTY issue vs a Claude Code rendering issue.

Please let me know when this issue has been resolved so I can put no flicker back on.

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