Copilot retires GPT-5.5, GPT-5.4, GPT-5 mini, Gemini 3.7 Flash and Grok 4.5
As of Oct 19 these models are gone from most Copilot experiences, including Chat, agent mode and completions. GitHub's suggested swaps: GPT-6.1 Sol for GPT-5.5 and GPT-5.4, GPT-6 Luna for GPT-5.4 mini and GPT-5 mini, Gemini 3.8 Flash and Grok 4.7. Enterprise admins may need to enable the replacements in model policies. Source