GitHub GPT-5.3-Codex Is Now the Default Model for GitHub Copilot Business and Enterprise
GitHub made GPT-5.3-Codex the base model for all Copilot Business and Enterprise organizations on May 17, replacing GPT-4.1. It's GitHub's first long-term support model, guaranteed available through February 2027.
GitHub flipped the switch on May 17: GPT-5.3-Codex is now the default model for all Copilot Business and Copilot Enterprise organizations, replacing GPT-4.1. The change applies automatically — no admin action required.
The GitHub Changelog entry is brief, but the accompanying context matters. GPT-5.3-Codex is GitHub’s first long-term support (LTS) model in a partnership with OpenAI, meaning it’s guaranteed to remain available through February 4, 2027 — a full 12 months from its February 5 launch date.
Why the LTS designation matters for enterprises
Enterprise software teams move slowly on tooling changes. Security reviews, procurement cycles, compliance sign-offs — these take time. The LTS commitment means a team can evaluate GPT-5.3-Codex for their workflows knowing the model won’t be pulled or swapped under them before they’ve had a chance to properly test it.
The model itself scores 77.3% on Terminal-Bench 2.0, up from 64.0% on the previous base model. It’s described as a “Codex-native agent” designed for long-horizon technical work rather than short single-file completions.
Billing implications
GPT-5.3-Codex carries a 1x premium request unit multiplier in Copilot’s upcoming AI Credits system. GPT-4.1 stays enabled at a 0x multiplier for now, so there’s a grace period if any teams need to fall back. That ends June 1, when GPT-4.1 deprecates alongside the launch of usage-based billing.
From June 1, all Copilot plans shift to AI Credits. Copilot Business and Enterprise both include monthly credit allotments; GPT-5.3-Codex usage counts against those allotments at the 1x rate. Premium models like Opus 4.7 carry higher multipliers.
Who this applies to
The change is scoped specifically to Business and Enterprise plans. Copilot Pro, Pro+, and Free users follow separate model availability timelines and aren’t affected by this transition. Those plans are in the middle of their own separate upheaval around paused sign-ups and tightened usage limits, which is a different story.