# Copilot Defaults to GPT-5.3-Codex — LTS Through Feb 2027 for Business/Enterprise

Times of AI Desk · 2026-05-17 · Products

[https://timesof.ai/2026/05/github-copilot-gpt-5-3-codex-base-model](https://timesof.ai/2026/05/github-copilot-gpt-5-3-codex-base-model)

> 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”](https://github.blog/changelog/2026-05-17-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.