GitHub Copilot May Enterprise Updates — GPT-5.3-Codex Default, Targeted Model Rules, CLI Managed Plugins

Summary

GitHub shipped a cluster of Copilot Business/Enterprise admin controls during May 2026 that collectively reshape what "rolling out Copilot" looks like for a regulated enterprise. On May 17, GPT-5.3-Codex became the default base model for all Copilot Business and Copilot Enterprise organizations, replacing GPT-4.1 — a silent capability jump for any customer who has not overridden defaults. On May 26, GitHub introduced targeted model rules in public preview, letting enterprise admins allow specifi