GPT-5.3-Codex Long-Term Support in GitHub Copilot
GitHub CopilotGitHub has designated GPT-5.3-Codex as its first long-term support (LTS) model for Copilot Business and Copilot Enterprise, guaranteeing its availability for a full 12 months — from its February 5, 2026 launch through February 4, 2027. Alongside the LTS designation, GPT-5.3-Codex will replace GPT-4.1 as the default base model for all Business and Enterprise organizations, with an automatic rollout scheduled to complete by May 17, 2026. The LTS program is designed to give enterprises the stability they need for internal security and safety reviews before adopting new models.
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GPT-5.3-Codex Becomes GitHub Copilot's First LTS Model
GitHub announced on March 18, 2026 that GPT-5.3-Codex has been designated as the first long-term support (LTS) model for GitHub Copilot, established in partnership with OpenAI. The LTS designation is a new program specifically designed for Copilot Business and Copilot Enterprise subscribers who need predictable model availability — particularly large organizations that require time to conduct internal security and safety reviews before adopting any AI model.
What Long-Term Support Means
Under the LTS program, a designated model is guaranteed to remain available for a full 12 months from its launch date. GPT-5.3-Codex launched on February 5, 2026, meaning its supported window runs through February 4, 2027. During this period, GitHub commits not to deprecate or remove the model from Copilot, giving enterprises a stable, predictable foundation to build internal tooling and processes around.
This is a meaningful commitment for regulated industries and large enterprises where AI model changes can trigger internal compliance reviews. The LTS program gives those organizations a guaranteed window to adopt a model, validate it, and rely on it without worrying about surprise deprecations.
GPT-5.3-Codex Replaces GPT-4.1 as the Base Model
Beyond the LTS designation, this announcement introduces a base model change for Copilot Business and Copilot Enterprise. The base model is the model an organization falls back to when it has not explicitly approved other models through its internal review process. Currently, that default is GPT-4.1 (with a 0x premium request multiplier).
GitHub will automatically roll out GPT-5.3-Codex as the new base model for all Copilot Business and Copilot Enterprise organizations within 60 days of the March 18 announcement, with the cutover date set for May 17, 2026. The new base model carries a 1x premium request unit multiplier, compared to GPT-4.1's current 0x rate.
GitHub notes that GPT-5.3-Codex has a significantly high code survival rate among enterprise customers — meaning code written by the model tends to make it through review and into production at higher rates than its predecessor.
Scope and Plan Availability
The LTS program and base model change apply exclusively to Copilot Business and Copilot Enterprise subscribers. Individual plans — Copilot Pro, Pro+, and Free — are not included in the LTS program and follow standard deprecation timelines.
Timeline Summary
| Date | Event |
|---|---|
| February 5, 2026 | GPT-5.3-Codex launches |
| March 18, 2026 | LTS designation announced |
| May 17, 2026 | GPT-5.3-Codex becomes default base model for all Business/Enterprise orgs |
| February 4, 2027 | LTS support window ends |