This guide takes a new installation to one result: the requested theme has been visibly verified in the current Codex window. You will install the Plugin, check the loaded release, choose a published theme ID, and run one apply transaction.

Before you start

You need:

the ChatGPT desktop app with access to the Codex view on a supported macOS or Windows computer;
a terminal where the codex plugin commands are available; and
a real six-digit theme ID copied from the theme gallery or a theme detail page.

Do not guess a theme ID. The ID connects the gallery, the downloaded package, and the final verification to the same published theme. Free and Pro themes use the same six-digit format.

The gallery can be viewed without signing in. Downloading either a Free or Pro package requires an authorized Plugin device. The first protected operation may open a browser so you can sign in and approve the computer.

Install the Plugin

Run the three public installation commands in a terminal, in this order:

codex plugin marketplace add yuanjohn01-byte/codex-skin-plugin --ref main
codex plugin add codex-skin@codex-skin
codex plugin list --json

The first command adds the Git-backed Marketplace source. The second installs the Plugin from that source. The final JSON must contain exactly one codex-skin@codex-skin entry with both of these fields:

{
  "installed": true,
  "enabled": true
}

Paid Alpha Helper binaries do not yet use commercial Apple Developer ID/notarization or public Windows code signing. Gatekeeper or SmartScreen may therefore show a first-run warning. Keep operating-system protection enabled, use only the release selected by the fixed Bootstrap, and do not follow an undocumented command that disables a protection.

Do not open a Marketplace form, edit Codex configuration, or delete a cache directory. If one of these commands fails, keep the original error and use the non-destructive steps in Plugin installation failure.

Verify the installed version

An installed entry does not prove that the current Codex task has loaded the new Skill. Completely quit Codex, reopen it, and start a new task. Ask Codex to run:

$codex-skin-version

For the current Production Paid Alpha, the version response should identify:

Plugin 0.1.0-paid-alpha;
Helper .17 and Bootstrap .16;
Production origin https://codexskin.ai; and
the Production Paid Alpha GitHub prerelease channel, not stable/latest.

A stale subtitle in the Plugin details screen does not by itself mean the update failed. Use the version Skill in a newly opened task as the release check.

Choose a six-digit theme ID

Open the theme gallery, choose a published theme, and copy its six-digit ID. For example, Ember Dune is a published Free theme with ID 100002. Its detail page is /themes/100002.

The Free or Pro label describes access. It does not change the ID format or the package verification path.

Apply the theme from a Codex task

In the new Codex task, make a normal request that includes the exact ID:

Codex Skin, apply theme 100002.

You should not construct a Helper command, provide a download URL, or paste CSS. The Plugin extracts the ID and uses its fixed platform wrapper.

An ordinary apply or switch usually takes 20–60 seconds. Until Codex reports an explicit success or failure, do not click, type, navigate, or close the current Codex window. If the operation opens a browser authorization or Pricing page, you may use that browser page. Do not submit the apply request a second time.

If browser approval opens

Sign in on the Codex Skin page and approve the computer shown there. Then return to the same Codex task. The original transaction continues with the original ID; you do not need to start another apply.

If the page says the device limit has been reached, approval was canceled, or the request expired, follow the matching step in Troubleshooting instead of changing local files.

If Codex asks to restart once

Some operations need Codex to close and reopen once with the same profile. Codex Skin will ask for an explicit yes or no before that happens. A yes only authorizes the verified Helper to continue this existing transaction; it does not mean the theme is already applied.

After Codex reopens, start or resume a task and check local status. If the restart status is still running, wait briefly and check again for no longer than 60 seconds. Only completed, with the requested public ID and version, is success.

Confirm the visible result

The apply is complete only when the exact theme is visibly verified in the current Codex renderer. These states are not enough on their own:

the package was desired or downloaded;
a browser approval finished;
a restart was accepted;
a command is running; or
an earlier apply succeeded.

A direct apply returns one successful structured result with ok: true, the requested themePublicId, a themeVersion, and an operationId. A restart path finishes with restartStatus: completed and matching applied theme ID and version.

The Helper exits after the bounded operation. If you completely close Codex, restart the computer, or the renderer later reloads, apply the theme again through Codex Skin next time. The Paid Alpha does not run a background repair or auto-reapply service.

Next steps

Questions

Do I need to install Node or Go?

No. The user release uses a self-contained Helper. The fixed wrapper and Bootstrap manage the verified external copy when it is needed. Node and Go are development tools for the public repository, not user prerequisites for applying a theme.

Do I have to apply the theme again after closing Codex?

Yes, after you completely quit Codex, restart the computer, or a later renderer reload ends the visible guarantee. Open Codex and ask the Plugin to apply the theme again. Your last verified operation can help identify the previous theme, but local history is not proof that a new renderer is still themed.