It's just another step on the timeline.

GPT-5.6-Sol, GPT-5.6-Terra, and GPT-5.6-Luna were released in July of 2026.

The first release from the GPT-6 series was GPT-6-Astra. GPT-6-Astra happened on around September 3, 2026, and the previously-mentioned GPT-5.6-* widgets remained available.

Today, September 22, 2026, we now also have GPT-6-Sol and GPT-6-Luna added into the mix.

As I write this, all of the model identifiers I've mentioned are available to select for use within Codex.