Image: GitHub
Why it mattersTeams running agent harnesses, scripts or evaluations that pin one of the three model names have one month to swap in the suggested replacement before the model stops answering.
Pin a model in a Copilot script today and that script may stop working on a Monday morning next month. GitHub said in its changelog that it will deprecate Claude Opus 4.8, Claude Opus 5 and GPT-5.6 Terra across every Copilot experience on 16 November 2026. The removal covers Copilot Chat, inline edits, ask and agent modes and code completions.
What is going and what replaces it
GitHub's own suggested replacements are Claude Opus 5.5 for both Opus 4.8 and Opus 5, and either GPT-6.1 Sol or GPT-6 Luna for GPT-5.6 Terra. One carve-out: Claude Opus 4.8 will stay available to individual GitHub Copilot subscribers on annual plans so they keep an Opus option. GitHub says the deprecation of Opus 4.8 does not apply to those customers.
What administrators need to do
Under default model enablement, the suggested alternatives are turned on automatically for Copilot Enterprise and Copilot Business customers, unless an administrator has turned off the global default or disabled the model. If the global default is off, access to the replacement models has to be enabled through model policies in Copilot settings before users will see them in the chat model selector. GitHub says no action is required to remove the deprecated models themselves after the date.
Why the Opus 4.8 carve-out matters
Opus 4.8 is held back for annual-plan individual subscribers only because those customers paid up front for an Opus-level model. GitHub does not say for how long. A team or business account that still routes to Opus 4.8 after 16 November falls back to Opus 5.5. For a team that chose Opus 4.8 because of a specific quirk of its output, this is a quiet switch of the model behind the same label.
The chat window is the easy part of a model deprecation. A reader there sees the model list change and picks the suggested alternative. The practical cost lives in the places where a model name is written down. A Copilot CLI agent that references claude-opus-5 in a workflow, an evaluation harness that pins the model to compare answers over time, a prompt library that notes "use Opus 5 for refactors": all of them need the same update, and they do not announce themselves. Thirty-two days is enough to grep for the three names across a monorepo, pick a replacement and run the suite once against it to see whether anything moved. It is also enough to put the swap on a release branch that lands before 16 November rather than after.
GitHub says more information on supported models is in its documentation and that feedback can be left in the GitHub Community.
Source
Primary source: GitHub Changelog.
This item was written by an AI system from the linked source. Reveneau is responsible for what it publishes.
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