Dual light/dark palettes that follow your system appearance, with typography, radii and spacing tuned after the design language of the OpenAI Codex app and ChatGPT.

Highlights

• Light / dark, hands-off — two hand-tuned palettes; the app follows the macOS appearance, or you pin one in Settings
• Graphite on paper — flat surfaces, hairline borders, hierarchy carried by weight (600/500/400); blue is reserved for interaction, never chrome
• 10px radius system — controls, sidebar rows and cards at 10px; message bubbles at 12px; composer at 16px
• 6 / 10 / 16 / 24 spacing rhythm — paragraph, list, block and turn gaps all land on the same scale, so long threads read like a document
• 1.7 line height — the reading rhythm is one notch airier than stock (headings 1.35, code 1.55), painted through the theme's root line-height knob
• 880px reading column — prose wider than ChatGPT's 720–768px, with three presets in Settings: Narrow 768 / Standard 880 / Wide 992px
• Respects your configuration — text size, chat font, interface mode, translucency, session density and every other Hermes setting stay under Hermes' own control; the theme only paints theme-level tokens

Screenshots

Design language

Principle	Practice
Graphite on paper	Near-white canvas (#FFFFFF) / near-black canvas (#181818)
Weight-carried hierarchy	Headings 600, labels 500, body 400 — no decorative colour
Interaction-only blue	#339CFF dark / #0B72D9 light for links, focus rings, selection
Hairline borders	1px strokes instead of shadows; surfaces stay flat
Radius system	10px controls · 12px bubbles · 16px composer
Spacing rhythm	6 / 10 / 16 / 24px increments
Line height	Root 1.7 — a notch airier than stock; headings 1.35, code 1.55
Reading column	880px default · presets 768 / 880 / 992px (ChatGPT: 720–768px)

Palettes

Token	Dark	Light
Canvas	#181818	#FFFFFF
Sidebar	#171717	#F9F9F9
Card	#212121	#F7F7F7
User bubble	#262626	#F4F4F4
Border	#2E2E2E	#E7E7E7
Accent	#339CFF	#0B72D9

Install

Once listed in the plugin catalog:

hermes plugins install codex-theme

Or install straight from GitHub:

hermes plugins install ethanz-code/hermes-codex-theme

Then open Settings → Plugins → Codex Theme and press Reapply (the theme also applies itself once on first load).

[!TIP] Manual / development install: copy desktop/plugin.js to ~/.hermes/desktop-plugins/codex-theme/plugin.js and run Reload desktop plugins from ⌘K.

Settings

Everything lives in Settings → Plugins → Codex Theme, on native settings rows with segmented controls:

Setting	Options	Notes
Appearance	Follow system / Dark / Light	Follows the macOS appearance by default
Reading column	Narrow (768px) / Standard (880px, default) / Wide (992px)	Theme-level knob; Hermes has no built-in width setting

⌘K also carries two quiet rows: Theme: 使用 Codex 主题 and Theme: Codex 主题设置.

What this theme deliberately does not touch

Your Hermes configuration is yours. The theme paints theme-level tokens only (palette, type stack fallback, radii, spacing) and leaves every user-configurable setting alone — text size (Settings → Appearance), chat font (display.chat_font), interface mode, translucency, session-list density, chat background, timestamps, and everything in config.yaml. Two standing rules:

[!IMPORTANT]

• The theme never writes --chat-text-scale — that knob belongs to Settings → Appearance and writing it would create two owners that overwrite each other.
• The theme takes over the palette once on first install. After that, a theme you pick manually always wins; Reapply is opt-in.

Disclosure

Per catalog rule 13, here is everything this plugin does that a user would want to know before installing:

• No network calls. The plugin fetches nothing and phones home nothing.
• No telemetry. No usage reporting of any kind.
• No credentials. It reads and writes none.
• No core patching. Themes, palette commands and the settings page are registered through the Desktop plugin SDK only (THEMES_AREA, PALETTE_AREA, ctx.registerSettingsPage, ctx.i18n).
• Storage: one plugin-scoped record (ctx.storage) for your settings-page choices — appearance mode and reading-column width.
• Styling: the theme's customCSS is injected as a scoped style block by the app's own theme engine, exactly like user skins; it changes visuals, never behavior.

Credits

Design language after the OpenAI Codex app and ChatGPT (graphite-on-paper palette, radius system, spacing rhythm). This is an independent community theme — not affiliated with, endorsed by, or a product of OpenAI.

Built on the Hermes Desktop Plugin SDK. Licensed under the MIT License.