Streaming response renders multiple partial states stacked instead of replacing

Description

During a streaming response, the output is displayed multiple times in partial states — each incremental chunk appears as a new bullet point stacked below the previous one, rather than updating in place. The final complete response is correct, but all intermediate partial renders remain visible above it.

Steps to reproduce

1. Ask a question that produces a multi-sentence response
2. Observe the streaming output in the Claude Code UI

Expected behavior

Streaming response updates in place — each token appended to the current output.

Actual behavior

Each partial state of the response is rendered as a new block. Multiple incomplete copies of the same response appear stacked vertically. The final response at the bottom is correct, but the earlier partial renders are not cleared.

Environment

• Platform: macOS (darwin 25.5.0)
• Shell: zsh
• Claude Code version: unknown (session-based)

Screenshot

User reported the issue with a screenshot showing the stacked partial renders. Pattern visible: same text repeating with progressively more content, with "v30):" and other mid-sentence fragments appearing as standalone lines.