GitHub Copilot Makes Gemini 4 Hydrogen Generally Available Across VS Code, CLI, Coding Agent and More at Provider List Pricing; Six Models Including Claude Fable 5, Gemini 3.8 Flash, Grok 4.6 and Kimi K3 Retire December 14

Background

Google pushed Gemini 4 Hydrogen to general availability in mid-November, positioning it as a Flash-class model that is faster and better at agent tasks than Gemini 3.8 Flash. For developers, a new model only becomes practical once it lands in the IDEs and coding assistants they use every day. GitHub Copilot is the default entry point for many teams, so when it adds or retires models, that directly shapes model choices and budgets.

What changed

According to the GitHub Changelog, Gemini 4 Hydrogen is built for fast, efficient agentic coding, tool use and multistep workflows, with better instruction following than Gemini 3.8 Flash. In Copilot it is not just a chat model: it can be selected in Copilot CLI, the Copilot coding agent, the Copilot app and the Copilot SDK, so it can power background agent tasks directly. Business and Enterprise keep the default-enablement policy for new models, and admins can switch it off in the model policy.

Numbers and pricing

Neither GitHub post gives new benchmark numbers; GitHub only says instruction following beats Gemini 3.8 Flash. Billing is usage-based at provider list pricing, and the exact rates are in GitHub's Models and pricing documentation rather than in the announcement. The deprecation list is the most practical part: from December 14, Claude Fable 5, Claude Haiku 4.5, Gemini 3.8 Flash, Gemini 4 Argon, Grok 4.6 and Kimi K3 leave every Copilot experience, including Chat, inline edits, ask and agent modes, and code completions.

What developers should do

Look for Gemini 4 Hydrogen in the model picker in VS Code or Copilot CLI; if it is not there yet, the rollout is gradual. If your workflows, automations or SDK integrations hard-code a retiring model, switch before December 14 to the suggested replacement: Fable 5 to Fable 5.2, Haiku 4.5 to Haiku 5.5, Gemini 3.8 Flash to Gemini 4 Hydrogen, Gemini 4 Argon to Gemini 4 Carbon, and Grok 4.6 to Grok 4.7; a replacement for Kimi K3 has not been announced. Enterprise admins who turned off the global default need to enable the replacement models manually in Copilot settings.