In a March 19, 2026 post on X, GitHub Changelog said long-term support models are now available for Copilot Business and Copilot Enterprise, with GPT-5.3-Codex as the first designated model. The linked changelog entry says GitHub will keep designated LTS models available for a full 12 months from launch. For GPT-5.3-Codex, that means availability from its February 5, 2026 launch through February 4, 2027.

GitHub frames the move as a stability measure for enterprises that need time for internal security and safety reviews before adopting newer model options. The same changelog also says GPT-5.3-Codex becomes the newest base model for Copilot when an organization has not yet approved other models through internal review. GitHub plans to automatically enable GPT-5.3-Codex for all Copilot Business and Copilot Enterprise organizations within 60 days of the announcement, which sets May 17, 2026 as the base-model transition date. The company also notes that GPT-5.3-Codex carries a 1x premium request unit multiplier, while GPT-4.1 remains force-enabled at a 0x multiplier for the time being.

GitHub is formalizing model stability for enterprise Copilot adoption

For individual users, model churn is mostly a question of preference. For larger organizations, it changes review windows, compliance checks, and internal rollout plans. By creating an LTS lane, GitHub is trying to make frontier coding models easier to approve and keep in service without constant revalidation. It also establishes GPT-5.3-Codex as the reference model at the center of Copilot's enterprise stack, both as the stability option and as the default path when other models are not yet cleared. Sources: the X post and GitHub's changelog.

#lts

GitHub makes GPT-5.3-Codex the first long-term support model for Copilot Enterprise