The whole chain of tweets is interesting and it ends with a link to the change log.
It looks like a lot of work went into this update.
Brief summary:
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Codex now available to ChatGPT Plus users.
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Internet access enabled for tasks (opt-in, configurable).
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Supports installs, tests, upgrades during execution.
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Available to Plus, Pro, Team; Enterprise coming soon.
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Usability: follow-up updates PRs; SSO skips MFA.
https://help.openai.com/en/articles/11428266-codex-changelog