GitHub Dark — Codex app theme

You already know this palette even if you've never installed it — it's the dark mode of github.com, maintained by GitHub's Primer design system team and extracted into a theme. The base #0d1117 is among the darkest in this catalog, and the syntax choices are instantly familiar: that particular soft blue on links and functions, coral keywords, and the exact green and red your merged pull requests have been wearing for years.

The killer feature in an agent context is diff literacy. When your agent proposes a change, the added/removed colors are literally the ones you've reviewed thousands of PRs in, so parsing patches requires zero relearning — your eyes already have the reflexes. Primer's contrast work also holds up in a dark room: text stays crisp at small sizes where softer themes start to smear.

Choose it when your agent window spends the day next to a browser full of GitHub tabs and you'd rather the two feel like one continuous tool. It's the least decorative option here — closer to a uniform than a mood — and on days when the work itself is the mood, that turns out to be exactly what you want.