GPT-5.5 Retirement Explained: What Changes in ChatGPT on October 14, 2026

OpenAI will switch off GPT-5.5 in ChatGPT on October 14, 2026. Its notice, posted in the ChatGPT documentation changelog on September 14, is short: "GPT-5.5 will retire from ChatGPT, ChatGPT Work, and Codex on all plans, including consumer, Business, Enterprise, and Edu plans. This retirement does not apply to the OpenAI API." For almost everyone who uses ChatGPT, nothing you do day to day changes, because ChatGPT stopped defaulting to GPT-5.5 when GPT-5.6 arrived. The retirement matters only if you still pick GPT-5.5 by hand, or have Codex settings that name it.

Key Takeaways

• The date is October 14, 2026. OpenAI's models page now lists GPT-5.5 as the "Previous-generation flagship model. Retires from ChatGPT, ChatGPT Work, and Codex on October 14, 2026; remains available on the OpenAI API."
• Every plan is affected. Free, Go, Plus, Pro, Business, Enterprise and Edu. There is no plan that keeps it.
• Your default model is already something else. OpenAI's GPT-5.6 help page says Free and Go users' "default model is GPT-5.6 Luna," and GPT-5.6 Sol powers Instant and the reasoning options on eligible paid plans.
• The named replacement is GPT-5.6 Sol. OpenAI tells Codex users to "switch to GPT-5.6 Sol (gpt-5.6-sol) before October 14." See GPT-5.6 Sol explained.
• Developers keep it. The retirement "does not apply to the OpenAI API."
• OpenAI has not said what happens to old GPT-5.5 chats. When GPT-4.5 and GPT-4o were retired earlier in 2026, old conversations continued on newer models. That is a precedent, not a promise for this one.
• GPT-5.5 had a short run. It was ChatGPT's flagship until GPT-5.6 reached general availability on July 9, 2026.

Who Is Affected

The honest answer is: fewer people than the headline suggests. Here is where GPT-5.5 sits for each kind of user, from OpenAI's own pages read on September 16, 2026.

The third row is the only consumer case that needs a decision, and OpenAI's own help page hedges on how many people it covers. Asked "Does GPT-5.6 replace GPT-5.5 Instant?", the page answers that GPT-5.6 Sol is "the updated ChatGPT experience for eligible paid users" and that "earlier models may remain available where supported." If you have never opened a menu to choose an older model, you are not in that row.

What Happens to Your Old GPT-5.5 Conversations

OpenAI has not said. Neither the changelog entry, the models page, nor the workspace model availability page describes what happens to a conversation that was running on GPT-5.5. We checked all three on September 16, 2026. OpenAI's model release notes, in the newest copy we could read (captured September 15), had not yet added a GPT-5.5 retirement entry.

What OpenAI did the last two times is on the record. When GPT-4.5 left ChatGPT on June 26, 2026, the ChatGPT release notes said: "Existing conversations that used GPT-4.5 can continue with GPT-5.5." When it retired GPT-4o and several other models in February 2026, its retirement help article said: "Conversations and projects are defaulted to their GPT-5.3 Instant and GPT-5.4 Thinking and Pro equivalents going forward," and "GPTs using retired models will automatically move to the closest" equivalent. Your chat history was not deleted then. Expect the same pattern, but treat it as what OpenAI did before rather than what it has promised now.

Does It Affect ChatGPT Voice?

Not in a way you need to act on. When OpenAI launched GPT-Live, the voice model behind ChatGPT Voice, it used GPT-5.5 as the model it handed harder questions to. OpenAI's ChatGPT release notes say that since September 9, 2026, ChatGPT Voice "can now use GPT-5.6 or GPT-6 Astra" for that job. So Voice had already moved on before the retirement notice appeared.

Why OpenAI Is Doing This

OpenAI gives no reason in the notice itself. The pattern is familiar: in May 2026 it said it was "continuing to retire older models with limited usage in ChatGPT so we can better serve our newer, most capable models," when it scheduled OpenAI o3 and GPT-4.5 for retirement. GPT-5.5 is now one generation behind GPT-5.6, which covers everyday use, and GPT-6 Astra sitting above it as GPT-6 Pro on the Pro and business plans.

Should You Do Anything

Do nothing if you use ChatGPT without changing models. Your default is already GPT-5.6, on every plan.

Switch now if you deliberately pick GPT-5.5 from the menu because you prefer how it answers. Try GPT-5.6 Sol for a few weeks before October 14 rather than finding out on the day. If you are on Free or Go, the older model is not what you have been using anyway.

Update your settings if you use Codex with your ChatGPT account. OpenAI's instruction is specific: replace gpt-5.5 with gpt-5.6-sol in "saved model settings, managed configurations, custom agents, scheduled tasks, and scripts that select a model."

Do not pay for a higher plan because of this. No plan keeps GPT-5.5. If you are deciding whether a subscription is worth it for other reasons, see whether ChatGPT Plus is worth it and the best free AI chatbot in 2026.