From the source

OpenAI’s GPT-6 Sol and GPT-6 Luna now available

Two new GPT-6 models available in GitHub Copilot

OpenAI's GPT-6 Sol and GPT-6 Luna models are now available in GitHub Copilot alongside the previously released GPT-6 Astra.

GPT-6 Sol is a balanced model for interactive and agentic coding available to Copilot Pro+, Max, Business, and Enterprise plans.

GPT-6 Luna is a lightweight, cost-efficient model for smaller tasks available to Copilot Pro, Pro+, Max, Business, and Enterprise plans.

Both models can be selected through the model picker across multiple IDEs and platforms.

From the source
OpenAI's GPT-6 family is expanding in GitHub Copilot with two additional models: GPT-6 Sol, and GPT-6 Luna. Joining the previously released GPT-6 Astra, these new options let you select the model that best fits your task, whether that's everyday agentic coding or fast, cost-efficient assistance.
github.blog