Image: GitHub
Why it mattersAny Copilot workflow, script, or agent that pinned one of these five models must be updated to a supported name today, and Copilot Enterprise admins have to enable the replacements in model policies before their teams see them.
GitHub deprecated five Copilot models across Copilot Chat, inline edits, ask and agent modes, and code completions on 1 September 2026. The changelog entry was posted the day before, on 31 August 2026, and states the effective date directly. Anyone whose editor plugin, CI script, or Copilot agent has one of these model names hardcoded needs to switch to a supported name for that surface to keep working.
The models retired and their suggested replacements
GitHub named each retired model and its official alternative in a single table on the changelog page.
- Gemini 3.1 Pro is retired. GitHub suggests Gemini 3.7 Flash as the replacement.
- Claude Opus 4.5 is retired. GitHub suggests Claude Opus 4.7, Claude Opus 4.8, or Claude Opus 5.
- Claude Sonnet 4.5 is retired. GitHub suggests Claude Sonnet 5.
- Claude Sonnet 4.6 is retired across most Copilot surfaces. GitHub suggests Claude Sonnet 5.
- Raptor Mini is retired. GitHub suggests MAI-Code-1.1-Flash.
The one exception for Claude Sonnet 4.6
GitHub states that Claude Sonnet 4.6 stays available to individual GitHub Copilot subscribers on annual plans. Every other seat, including team and enterprise seats, loses access on the deprecation date. A team that standardised on Sonnet 4.6 for a particular workflow cannot keep it by paying for a team plan; the individual annual plan is the only exception.
Enterprise admins have work to do first
The changelog carries a specific note for Copilot Enterprise: administrators may need to enable access to the alternative models through their organisation's model policies before individual developers see them. A developer whose editor no longer offers the retired model but does not yet see the replacement should confirm with an admin that the model policy has been updated. GitHub tells administrators to verify by checking their own individual Copilot settings and confirming the policy is enabled for the specific model.
What actually stops working and where
A model string appears in three places a team is likely to have. Some IDE plugins pin the model in their own settings, and those UIs will now show the deprecated names as unavailable. Copilot Chat sessions and agent-mode workflows pass a model name to the Copilot API; anything scripted or committed with the old names starts failing with a model-not-available response rather than quietly switching to a new model, so any harness or eval loop that logs model output should be checked. GitHub Actions workflows and internal tools that call the Copilot API against one of these five names need the string updated in the same commit that acknowledges the switch.
Model deprecations on a shared surface like Copilot are one of the few AI-tooling events that force a same-day change on a team, because the deadline is set by the vendor rather than chosen. The safe step is to grep the codebase and CI configuration for the five deprecated names in one pass, replace each with the closest suggested alternative, and re-run any evals that care about the choice, since Sonnet 5 does not behave the same as 4.6 and Gemini 3.7 Flash is a different size of model from 3.1 Pro. Enterprise teams should verify the model policy in Copilot settings first, before the developer support tickets begin arriving. The pattern will keep repeating: GitHub retired three model generations in a single changelog entry, and the next set of Copilot deprecations will follow whenever the newer models mature.
Source
Primary source: GitHub Copilot changelog, 31 August 2026.
This item was written by an AI system from the linked source. Reveneau is responsible for what it publishes.
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