TUI corruption when session name contains a Unicode 16.0 emoji (Ghostty only)

Environment

• Claude Code on macOS (Darwin 25.5.0)
• Terminal: Ghostty
• Model: Opus 4.8 (irrelevant to the bug)

Description

Renaming a session (/rename) to a name containing a very recent emoji corrupts the TUI: the separator line and the right-aligned session-name badge get repainted multiple times at wrong positions instead of once. The screen layout drifts after every redraw. (Screenshot attached.)

Steps to reproduce

1. In Ghostty, run /rename e🫪 — the emoji is U+1FAEA "Face with Bags Under Eyes", introduced in Unicode 16.0 (2024).
2. Send any message.
3. Observe: stacked blue separator lines and duplicated session-name badges; cursor position drifts.

Expected

Single separator line, single badge — same as with older emoji.

Actual

Repeated separator lines + stacked badges; cursor desyncs on every redraw.

Terminal-specific behavior (the key clue)

| Terminal | App | Result |
|---|---|---|
| iTerm2 | Claude Code | OK |
| Kitty | Claude Code | OK |
| Ghostty | Claude Code | Corrupted |
| Ghostty | other TUI | OK |

Only the Ghostty + Claude Code combination breaks.

Likely root cause

Width mismatch. Claude Code's column-width calculation (string-width / wcwidth table) doesn't yet classify U+1FAEA (Unicode 16.0), so it computes a different cell width than Ghostty renders. That disagreement desyncs cursor positioning during redraw. iTerm/Kitty agree with Claude Code's width table and don't corrupt; Ghostty uses different grapheme-width handling and does. Updating the bundled string-width/Unicode tables to 16.0 should fix it.

Related (same root-cause family)

• #30471 — TUI misalignment caused by string-width miscalculating emoji character width (closed/stale)
• #52651 — Country flag emojis render as separate tiles in TUI (macOS, Ghostty) (closed/stale)

This class of bug recurs with each new Unicode emoji block; pinning the width tables to the current Unicode version would address the whole family.