[BUG] Startup ASCII banner reappears mid-session — conversation appears to disappear then returns (v2.1.89, Windows)

Summary

During active sessions, the conversation window appears to disappear and is replaced momentarily by the Claude Code startup ASCII art banner/header (the ▐▛███▜▌ Claude Code v2.1.89 splash screen), then the conversation content returns. The conversation is NOT lost — it is retained and visible again after the flash. But visually it looks like the session compacted or reset.

What is seen

The conversation scrollback is replaced mid-session by something like:

▐▛███▜▌   Claude Code v2.1.89
▝▜█████▛▘  Opus 4.6 (1M context) with high effort · Claude Max
  ▘▘ ▝▝    ~\Desktop\trading_system

...followed by the conversation resuming. The startup header appears as if the session just launched.

Expected behavior

Conversation scrollback remains visible. The startup banner should only appear once at session start.

Environment

• OS: Windows
• Claude Code: v2.1.89
• Terminal: PowerShell / Windows Terminal
• Observed during: long sessions with active background agents
• Conversation content is retained (not a data loss bug — purely display/rendering)

Related

• #769 — full terminal buffer redraw during thinking (same component, different manifestation)
• #826 — console scrolling to top on long sessions (similar display disruption)
• v2.1.89 added CLAUDE_CODE_NO_FLICKER=1 env var for flicker-free rendering — does not appear to resolve this specific variant