ChatGPT users who still rely on GPT-5.5 now have a retirement date to plan around: October 14, 2026. The change covers ChatGPT, ChatGPT Work, and Codex used with ChatGPT sign-in. GPT-5.5 will remain available through the OpenAI API. That distinction matters for anyone using both a ChatGPT subscription and applications built on OpenAI's models. The same model can leave one product without disappearing from another.
As of September 16, GPT-5.6 Sol is already available, GPT-6 Astra has arrived, and a possible GPT-6 Sol remains unconfirmed. The immediate decision for users is which available model can take over their existing work before the retirement deadline.
Prepare saved tasks for the GPT-5.5 retirement
OpenAI's notice covers consumer, Business, Enterprise, and Edu plans. For Codex users signed in through ChatGPT, the documented replacement is GPT-5.6 Sol, using the identifier gpt-5.6-sol.
The practical work extends beyond choosing a different model for a new conversation. A saved task or custom agent may still select GPT-5.5 even after someone changes their everyday preference. OpenAI advises checking workspace defaults, saved model settings, managed configurations, custom agents, scheduled tasks, and scripts that explicitly select the older model. Administrators also need to confirm that affected users can access the replacement.
Consider a team that uses a scheduled task to draft a weekly report. Before changing its model, keep a completed report and its source material as a reference. Run the same assignment with the replacement and check whether it preserves the required sections, distinguishes missing data from zero values, and supports its conclusions with the supplied sources. A fluent answer can still miss one of those requirements. Testing before the deadline leaves time to adjust the instructions.
The Sol model you can use today is GPT-5.6
The names are easy to scramble. OpenAI's documented Sol model is GPT-5.6 Sol. The GPT-5.6 family entered general availability in July, with Sol alongside Terra and Luna. A separate August update adapted Sol for everyday ChatGPT conversations. “GPT-6.5 Sol” is not a confirmed product name in the official materials reviewed for this article.
In its August update to Sol, OpenAI described more focused answers and improved factual reliability, plus a slider for controlling how much thought a response receives. That conversation-focused version was specific to Chat in ChatGPT; the version powering Work and Codex would not change as part of the release. A shared model name therefore does not guarantee identical behavior across every product.
OpenAI's ChatGPT availability guide lists Sol for eligible paid plans and Luna for Free and Go users. On those Free and Go plans, the Think option uses Luna. If two people see different choices, their subscription and workspace settings are worth checking before assuming a model is missing.
Where you can use GPT-6 Astra
OpenAI introduced GPT-6 Astra on September 3. The company describes improvements in computer use, coding, research, and professional tasks involving several steps. Its examples include creating documents, spreadsheets, and presentations that follow existing templates. For teams, that makes the quality of the finished file a useful measure alongside the quality of the conversational answer.
For Plus subscribers, OpenAI's availability guidance includes Astra in ChatGPT Work and Codex. In Chat, Astra powers the GPT-6 Pro option offered to eligible Pro, Business, and Enterprise plans. Enterprise access also depends on workspace permissions. Seeing Astra in Work therefore does not mean the same option must appear in ordinary Chat.
For a shared team workflow, ask a colleague with the intended subscription and workspace role to try the assignment before updating a common template. This checks whether the model choice works for the people who will use it.
Recent changes go beyond the model picker
OpenAI's September 14 release notes announced that Plus and Pro would stop automatically switching from Instant to Thinking globally. Users can still choose reasoning themselves, and automatic switching for safety remains possible. For a difficult request, deliberately selecting more reasoning becomes a useful habit.
Other September updates expand what a conversation can work with. The September 9 notes added deep research to Work and Codex, with access tied to those products' allowances or credits. September 10 brought the Data plugin for connected business analysis and Library integrations for Box, Dropbox, and SharePoint. Existing permissions still apply. These additions can matter as much as a model upgrade when the missing ingredient is access to the right source material.
What about the rumored GPT-6 Sol
Community posts have circulated the name GPT-6 Sol, including a Reddit thread claiming it was staged in the API. The post is evidence of community interest, but it cannot verify public access or a launch schedule.
As of September 16, the official model catalog and announcements reviewed here do not confirm a GPT-6 Sol release date, specifications, or public access. They document GPT-6 Astra and GPT-5.6 Sol. Treat predictions of an imminent Sol launch as speculation until OpenAI publishes the corresponding announcement or documentation.
There is already enough confirmed change to act on. Review GPT-5.5 dependencies before October 14, check which models your plan offers in each product, and test important recurring tasks with an available replacement. A future Sol announcement may change the choices a gain. It does not need to hold up preparation for a retirement that already has a firm date.