GitHub Copilot Retires Six AI Models Overnight, Breaking Workflows Built Around Them

GitHub deprecated six AI models across most Copilot experiences — Chat, inline edits, ask and agent modes, and code completions — effective September 1: Claude Opus 4.5, Claude Opus 4.6, Claude Sonnet 4.5, Claude Sonnet 4.6, Gemini 3.1 Pro, and a model referred to as Raptor mini. Claude Sonnet 4.6 remains available only to individual Copilot subscribers on annual plans, a narrower exception than blanket availability. The change lands alongside separate billing and policy updates and a unified Copilot experience relaunch planned no earlier than September 28.

Why a Model Deprecation Is a Real Operational Event, Not a Footnote

Development teams that pinned a specific model in custom instructions, CI pipeline configurations, or documented internal workflows now have those references pointing at a retired option — not a hypothetical risk, an immediate, concrete break for any team that hadn't already moved off the deprecated models. Unlike a typical software update that changes behavior gradually, a hard model retirement changes what a Copilot call actually returns starting on the announced date, with no gradual rollout to catch teams that missed the changelog announcement.

The Broader Set of Changes Landing at the Same Time

• Starting September 1, GitHub resumed sign-ups for new Copilot Business and Copilot Enterprise customers paying by credit card or PayPal, after apparently having paused that path
• Enterprise-managed default model settings, announced September 2, let administrators assign default models across teams — or let teams choose their own — giving organizations a governance lever they didn't previously have over which models their developers' Copilot sessions actually use
• GitHub plans to relaunch Copilot Chat on github.com, Copilot Chat in GitHub Mobile, and the Copilot cloud agent as a single, unified experience no earlier than September 28 — a consolidation of what had been separate surfaces
• Copilot CLI separately added automatic HTTPS proxy mTLS client certificate support and fixed transcript visibility and session-export issues

What Any Engineering Team Using Copilot Should Do Immediately

Audit any custom instructions, prompt templates, CI configurations, or internal documentation that references a specific model by name, and confirm none of them point at one of the six retired models. If your organization is on Enterprise tier, the new default-model management setting is worth configuring deliberately now, rather than leaving it on whatever default GitHub applies — an unreviewed default is itself a decision, just not necessarily the one your organization would have chosen if it had been made intentionally.