Feature request: custom themes / appearance customization for the Desktop app (Code tab + Chat)

Feature request: honor custom themes / appearance settings in the Claude Desktop app (Code tab and Chat)

What I'd like

The Claude Desktop app should let users customize its appearance — at minimum text color, ideally the same theme system the CLI already has:

1. Preferred: the Code tab's session view honors ~/.claude/themes/*.json (the existing custom-theme system) and the theme preference, the same way the terminal TUI does.
2. At minimum: appearance settings in the desktop app for text color / accent color / font, beyond the current light/dark toggle.

Current behavior

• The CLI's theming is excellent: ~/.claude/themes/ custom themes with ~70 color tokens, hot reload, statusLine, cosmetic hooks. I built a full brand skin with it and it works great in the terminal.
• The Desktop app (macOS, v1.26832.0) renders both the Chat side and the Code tab with fixed native styling. None of the theme tokens apply, /theme is unavailable in desktop sessions, and there is no appearance setting other than light/dark.
• The app bundle ships with asar integrity validation + onlyLoadAppFromAsar fuses enabled, so there is deliberately no unofficial escape hatch either — which is fine, but that makes first-party support the only path.

Why it matters

• Users who live in Claude Code all day want the same visual identity across CLI and desktop — right now a carefully built theme silently does nothing in the app that many users see most.
• Terminal-native users are exactly the audience that customizes their environment (fonts, palettes, statuslines). Competing agentic coding tools already allow appearance customization of their desktop surfaces.
• The token system already exists; the desktop session view is rendering the same conceptual UI (transcript, diffs, permission prompts, statusline data). Mapping the existing tokens onto it would reuse the design work already done for the TUI.

Environment

• Claude Desktop 1.26832.0, macOS 15 (Darwin 25)
• Claude Code CLI 2.1.226 (theming works as documented there)