GitHub Copilot will retire six AI models on September 1, 2026 across Copilot Chat, inline edits, ask and agent modes, and code completions. The affected models are Gemini 3.1 Pro, Claude Opus 4.5, Claude Opus 4.6, Claude Sonnet 4.5, Claude Sonnet 4.6, and Raptor Mini.
For QA teams, the deadline is a dependency change rather than a cosmetic model-picker update. Saved workflows, team guidance, evaluation baselines, and enterprise model policies may all point to a model that is about to disappear.
Models retiring on September 1
- Gemini 3.1 Pro — GitHub suggests Gemini 3.6 Flash.
- Claude Opus 4.5 and 4.6 — GitHub’s current retirement table suggests Claude Opus 5.
- Claude Sonnet 4.5 and 4.6 — GitHub suggests Claude Sonnet 5.
- Raptor Mini — the July announcement suggests MAI-Code-1-Flash.
There is one documented exception: Claude Sonnet 4.6 remains available to individual Copilot subscribers on annual plans so they retain a Sonnet option. GitHub also says enterprise administrators may need to enable replacement models through Copilot model policies before users can select them.
One replacement deserves extra care. GitHub’s current model-retirement history now schedules MAI-Code-1-Flash itself for retirement on September 10, 2026, with MAI-Code-1.1-Flash as its successor. Teams moving from Raptor Mini should therefore check the current supported-model documentation instead of creating a second near-term migration.
Why this matters for QA engineers
- Behavioral baselines will move: replacement models can change test-generation coverage, defect explanations, tool use, latency, and output structure.
- Agent workflows may fail or silently switch: confirm how each Copilot surface handles a retired explicit selection and how Auto selection behaves under your policies.
- Enterprise access can block migration: a technically supported replacement may still be unavailable until an administrator enables it.
- Documentation can go stale: internal prompts, onboarding pages, screenshots, and test playbooks may still tell engineers to select a retired model.
A practical migration checklist
- Search repository instructions, prompt files, CI configuration, screenshots, and QA playbooks for all six retiring model names.
- Confirm replacement-model policies are enabled for the relevant Copilot plans and clients.
- Replay a small fixed set of test-generation, flaky-test triage, and code-review tasks on the old and replacement models.
- Compare verified task completion, defects found, false positives, latency, AI-credit use, and output-format compatibility.
- Test explicit selection, Auto selection, and fallback behavior after the September 1 cutoff.
- Update team documentation and record the new baseline rather than assuming the replacement is behaviorally identical.
Bottom line
The September 1 Copilot model retirements affect six named models across the product, including agent workflows and completions. QA teams should migrate deliberately: verify access, choose a replacement that will remain supported, and re-run representative evaluations before treating the change as complete.
Sources
- GitHub Changelog: Upcoming August 2026 model deprecations in GitHub Copilot — July 31, 2026
- GitHub Docs: Supported AI models and model retirement history — accessed August 31, 2026
- GitHub Docs: Changing the AI model for GitHub Copilot Chat — accessed August 31, 2026