A coding assistant’s model picker is part of the development environment, and it needs maintenance too. GitHub’s September 18 notice scheduled several Copilot models for deprecation on October 19 across supported experiences, including chat, inline edits, and agent mode.
The notice includes GPT-5.5 and GPT-5.4, with GPT-5.6 Sol listed as the suggested alternative. For Business and Enterprise accounts, replacement availability depends on model policies: default enablement can make alternatives available, but administrator overrides still apply. GitHub says retired models do not need to be manually removed. The official notice contains the complete list.
Check the workflow, not just the menu
For a team, the practical work is identifying where a specific model has become an assumption: onboarding instructions, shared prompts, or an integration that requests it explicitly. Updating a name is only the first step.
A useful follow-up is to rerun one representative task and inspect the changes, tests, and explanations. This is a migration check, not evidence that the replacement behaves identically. The scheduled retirement also provides a reason to document who owns model access, so a developer is not left debugging an organization policy as though it were a broken prompt.
Source
GitHub Changelog — Upcoming deprecation of selected Copilot models.
