GitHub Copilot moves to GPT‑5.3‑Codex

GitHub said on May 17 that GPT-5.3-Codex is now the default model for Copilot Business and Copilot Enterprise, replacing GPT-4.1 for those paid workplace tiers. The change applies only to the enterprise-focused Copilot plans, not to Copilot Pro, Pro+, or Free, according to GitHub’s changelog and documentation. GitHub had previously designated GPT-5.3-Codex as the new base model on March 18, then switched it on automatically after a 60-day upgrade window for supported IDE extensions. ### Which Copilot customers are affected right now? Copilot Business and Copilot Enterprise organizations are the only customers covered by the base-model change, GitHub said. Individual plans, including Copilot Pro, Copilot Pro+ and Copilot Free, are on a separate model-deprecation timeline and do not get this enterprise base-model switch. (github.blog) GitHub’s documentation says a base model is the default model Copilot uses when no other model is enabled. In practice, that means enterprise users who have not manually selected or enabled another model will now be routed to GPT-5.3-Codex as the starting point for Copilot requests. ### Why did this happen on May 17 if GitHub announced it earlier? (github.blog) March 18, 2026 was the date GitHub says it designated GPT-5.3-Codex as both the base model and the long-term support, or LTS, model for enterprise Copilot. GitHub’s docs describe a 60-day upgrade window from “Day 0 to Day 60,” during which customers could update IDE extensions to versions that support the new model before automatic enablement. (docs.github.com) May 17, 2026 was the automatic enablement date. GitHub’s changelog says that as of that date, GPT-5.3-Codex “becomes the base model for all Copilot Business and Copilot Enterprise organizations,” formalizing the replacement of GPT-4.1 in those tiers. ### What does GitHub say is different about GPT-5.3-Codex? (docs.github.com) February 9, 2026 was the first broader Copilot rollout date for GPT-5.3-Codex, which GitHub described as OpenAI’s latest “agentic coding model.” GitHub said at the time that, in early testing, the model reached higher internal scores on coding, agentic and real-world capability benchmarks used by the company. (github.blog) March 18 brought a more specific enterprise claim. GitHub said GPT-5.3-Codex had shown a “significantly high code survival rate” among enterprise customers, the metric it cited when naming the model its first LTS option. GitHub did not publish a numerical survival-rate figure in the changelog excerpt returned by its site search. (github.blog) GitHub’s model docs also show GPT-5.3-Codex as one of several supported Copilot models, alongside newer options such as GPT-5.4 and GPT-5.4 nano in some contexts. That means the May 17 move is about the default enterprise setting, not exclusive availability of one model across all Copilot surfaces. ### What happens to GPT-4.1 for enterprise users? (github.blog) GPT-4.1 is not disappearing immediately from enterprise Copilot setups. GitHub said GPT-4.1 “will remain force-enabled at a 0x multiplier for the time being,” giving teams a temporary path to keep using it while they adjust. June 1, 2026 is the next date GitHub put on the calendar. (docs.github.com) The company said GPT-4.1 will deprecate alongside the launch of usage-based billing on that date, and directed customers needing more time to contact their account teams. ### How long is GitHub committing to this model? February 5, 2026 was the launch date GitHub gave for GPT-5.3-Codex, and February 4, 2027 is the end of its availability window as an LTS model. (github.blog) GitHub said designated LTS models will be available for a full 12 months from launch, making GPT-5.3-Codex the company’s first long-term support model in partnership with OpenAI. GitHub’s next published milestone is June 1, 2026, when usage-based billing begins and GPT-4.1 is scheduled to deprecate for these enterprise Copilot products. After that, February 4, 2027 is the date GitHub lists for the end of the GPT-5.3-Codex LTS window. (github.blog 1) (github.blog 2)