Six Models Leave GitHub Copilot Tomorrow, Including Claude Sonnet 4.6

TL;DR: GitHub Copilot retires six models on September 1 — including Claude Sonnet 4.6. If any config, extension setting, or CI step pins one of these model IDs, it will fail silently starting tomorrow morning.

The models going away and their replacements:

Retired	Replacement
Claude Opus 4.5	Opus 4.7, 4.8, or 5
Claude Opus 4.6	Opus 4.7, 4.8, or 5
Claude Sonnet 4.5	Sonnet 5
Claude Sonnet 4.6	Sonnet 5 (annual individual subscribers keep access temporarily)
Gemini 3.1 Pro	Gemini 3.6 Flash
Raptor Mini	MAI-Code-1-Flash

Most Copilot users are unaffected — when you haven't pinned a model, Copilot selects one for you and will route to a supported model automatically. The risk is in any place that hardcodes a model ID: .github/copilot.yaml files, IDE extension settings, GitHub Actions steps that call the Copilot API by model name.

A quick text search for claude-opus-4.5, claude-opus-4.6, claude-sonnet-4.5, claude-sonnet-4.6 across your repos and CI configs will surface everything that needs updating before tomorrow.

Why it matters: Deprecated Copilot models return errors, not fallback responses. Pinned workflows break silently on deprecation day — the error doesn't appear until the next time that path runs in production.

Sources: Upcoming August 2026 model deprecations — GitHub Changelog · GitHub Copilot in Visual Studio August 2026 update