Codex theme not showing after import? Here's the 1-minute fix.

Why your Codex theme isn't showing

As of the 2026 Codex app builds, the Appearance importer validates the codeThemeId field against a fixed list of built-in themes. If the payload uses an id that isn't on that list — most commonly "custom" — the import fails silently. No error, no change, no theme. This is the single most common reason a codex theme is not showing.

The rest of your payload (accent, surface, ink, diff colors) is perfectly valid — it's only that one gatekeeper field blocking the whole import.

codex-theme-v1:{
  "codeThemeId": "custom",
  "theme": { "accent": "#7c5cff", … }
}

codex-theme-v1:{
  "codeThemeId": "one",
  "theme": { "accent": "#7c5cff", … }
}

Valid built-in ids include one, catppuccin, matrix, solarized, monokai. Setting one of these does not override your custom colors — those still come from the theme object.

The 1-minute fix

1. Open your theme string

   Paste it into any text editor so you can see the JSON after the codex-theme-v1: prefix.

2. Find codeThemeId

   Look for "codeThemeId": "custom" (or any unfamiliar value).

3. Replace with a built-in

   Change it to "codeThemeId": "one". Keep everything else exactly as-is.

4. Re-import

   Back in Codex → Settings → Appearance → Import, paste the corrected string. Your codex theme now shows instantly.

Other reasons a Codex theme won't apply

You're on Apple Terminal (CLI only)

Apple Terminal has weak 24-bit color support. If you're theming the Codex CLI rather than the app, try an ANSI-friendly theme or switch to iTerm2 / Warp / Kitty.

You imported into the wrong mode

Dark and Light themes import separately. If you pasted a dark theme while Codex is in Light mode, switch modes (or import into both) to see it.

Malformed JSON

A stray comma or missing brace makes the whole string invalid. Regenerating from a tool avoids this entirely.

FAQ