Copilot Defaults to GPT-5.3-Codex — LTS Through Feb 2027 for Business/Enterprise
GitHub makes GPT-5.3-Codex the base model for all Copilot Business and Enterprise orgs, replacing GPT-4.1 — OpenAI’s first LTS model, guaranteed through February 4, 2027. The trade is enterprise predictability (review cycles, security) over perpetual latest-model churn.
Enterprise Copilot buyers need predictable model lifetimes as much as smarter completions. Defaulting to an LTS Codex variant is GitHub optimizing for security-review calendars — not for weekly model FOMO.
GitHub (May 17) announced that GPT-5.3-Codex is now the base model for all Copilot Business and Copilot Enterprise organizations, replacing GPT-4.1. The change applies organization-wide unless other models are explicitly approved. GPT-5.3-Codex is designated as OpenAI’s first long-term support (LTS) model, guaranteed available through February 4, 2027 (12 months from its February 5, 2026 launch).
Timeline#
| Date | Event |
|---|---|
| Mar 18, 2026 | LTS and base-model changes announced |
| May 17, 2026 | GPT-5.3-Codex becomes base for all Business/Enterprise orgs |
| Feb 4, 2027 | End of support for the model in these plans |
Orgs can still opt into other approved models; the default shifts to the newer Codex variant.
Claims vs checks#
Rollout dates and LTS designation are GitHub changelog primary. Performance uplift vs GPT-4.1 is implied by model generation, not proven with a published Copilot-specific bench in the changelog. LTS “guaranteed available” is a product-support commitment — not a capability freeze promise.
Limits#
- Base model ≠ only model; org approval lists still matter.
- No independent Copilot coding Elo tied to this default flip.
- LTS end date is hard — migration planning starts now for Feb 2027.
Sources#
- GitHub changelog: “GPT-5.3-Codex is now the base model for Copilot Business and Enterprise” (May 17, 2026).
- Related OpenAI model announcements referenced in the changelog for GPT-5.3-Codex launch context.