[BUG] theme: "auto": message blocks keep the colors of the theme they were drawn under; a live appearance switch never repaints them

Preflight Checklist

• [x] I have searched existing issues and this hasn't been reported yet
• [x] This is a single bug report
• [x] I am using the latest version of Claude Code

What's Wrong?

With "theme": "auto", switching the system appearance while claude is running leaves every already-rendered user-message block drawn in the previous theme's colors. Content rendered after the switch uses the new theme, so the session ends up mixed.

It is not direction-specific:

• start in light → switch to dark: message blocks stay white against the now-dark UI
• start in dark → switch to light: they stay dark against the now-light UI

Switching the system appearance back makes them look correct again, because the stale color happens to match once more.

Ctrl+L and resizing the terminal — a full alt-screen repaint — do not fix it. /theme → any theme → /theme → auto does.

Detection itself is fine: the terminal supports DEC mode 2031, and Claude Code re-queries the background on every appearance change. The problem is purely that blocks already on screen are never repainted.

What Should Happen?

Already-rendered blocks repaint in the newly detected theme, the same way they do when the theme is changed through /theme.

Error Messages/Logs

Capturing the pty across an appearance flip, the same block is drawn as:

  dark  ->  ESC[48;2;0;0;0m
  light ->  ESC[48;2;240;240;240m

with the foreground palette switching too (153;153;153 -> 102;102;102, 44;122;57),
and exactly one OSC 11 query at startup plus one more per appearance flip.

So both palettes resolve correctly; only previously drawn blocks keep the old ones.

Steps to Reproduce

1. Set "theme": "auto" in ~/.claude/settings.json, in a terminal that supports DEC mode 2031 (Ghostty 1.3.2 here).
2. With the system in light appearance, start claude and send two messages, so two user-message blocks are on screen.
3. Switch the system appearance to dark.
4. The assistant text below them switches to the dark theme, but the two message blocks keep their light background.
5. Ctrl+L and resizing the terminal do not change them. /theme → dark → /theme → auto repaints them correctly.

Claude Model

Opus

Is this a regression?

I don't know

Claude Code Version

2.1.275 (Claude Code)

Platform

Anthropic API

Operating System

macOS

Terminal/Shell

Other — Ghostty 1.3.2-main

Additional Information

• Reproduces in a plain Ghostty window with no multiplexer involved.
• macOS 27.0 (build 26A428), Apple Silicon. "tui": "fullscreen".
• Related but distinct: #86048 (auto resolves to the inverted theme) and #92389 (no resample when mode 2031 is unsupported). Here detection works and resolves correctly; the problem is that blocks already on screen are never repainted.