# Codex: GPT-6.1 Sol is the default, GPT-5.5 leaves on October 14

https://aycode.ai/blog/codex-gpt-6-1-sol/ · 2026-10-06 · News

OpenAI made GPT-6.1 Sol the default for complex work in Codex. GPT-5.5 retires from ChatGPT and Codex on 14 October; the API keeps it.

If you open Codex this week, the model under the hood has probably changed. And if you still lean on GPT-5.5, you have eight days.

## The new lineup

OpenAI's Codex model page now recommends three models:

- GPT-6.1 Sol (gpt-6.1-sol): the default for complex work, described as near-Astra performance at a lower cost.
- GPT-6 Luna (gpt-6-luna): the efficient one, for focused, high-volume tasks like summaries, extraction and focused coding.
- Astra (gpt-6-astra): the most capable, for long workflows that mix reasoning, computer use and judgment.

## GPT-5.5 retires on 14 October

GPT-5.5 leaves ChatGPT, ChatGPT Work and Codex on all consumer and enterprise plans on 14 October 2026. The API is not affected. OpenAI points people to Luna or Sol, depending on their plan. It is the third retirement in two months: GPT-5.4 and 5.4-mini went on 31 August, GPT-5.3-Codex-Spark on 14 September.

## Also new in Codex

- Ultrafast mode generates tokens faster in Codex and Work, on Pro $500 and eligible Enterprise and Edu plans.
- Cloud environments are prepared and published once, then reused as isolated workspaces.

## Our take

Watch the names. Coverage in September still called the replacement "GPT-5.6 Sol"; OpenAI's own page now says GPT-6.1 Sol, so scripts and configs that pin a model ID deserve a look. And one developer measured Sol using about 2.25 times the tokens per session of GPT-5.5. That is one person's numbers, not a benchmark, but it is worth checking against your own limits before the switch is forced.

## In AyCode

AyCode talks to the Codex installed on your machine and already lists GPT-6.1 Sol, Luna and Astra in its model menu. The usage view shows each account's limits, which helps when a new default eats tokens faster than the old one.

Sources:
- OpenAI: Codex models (https://learn.chatgpt.com/docs/models)
- OpenAI: What's new in Codex (https://learn.chatgpt.com/docs/whats-new)
- Vincent Schmalbach: GPT-5.5 retirement in Codex (https://www.vincentschmalbach.com/gpt-5-5-retirement-codex/)