# GPT-5.6 Sol, Terra and Luna: What Changed in ChatGPT?

DevFeed: [GPT-5.6 Sol, Terra and Luna: What Changed in ChatGPT?](<https://devfeed.tech/articles/gpt-5-6-sol-terra-and-luna-what-changed-in-chatgpt-28519.md>)

Original publisher: [Read original article](<https://blog.risingstack.com/gpt-5-6-sol-terra-luna-chatgpt-changes/>)

Author: RisingStack Engineering

Published: 2026-07-16T12:28:01Z

Content type: release

Language: en

Sources: [RisingStack](<https://devfeed.tech/sources/risingstack.md>)

Topics: [ChatGPT](<https://devfeed.tech/topics/chatgpt.md>), [OpenAI](<https://devfeed.tech/topics/openai.md>), [interfaces](<https://devfeed.tech/topics/interfaces.md>), [API](<https://devfeed.tech/topics/api.md>), [Availability](<https://devfeed.tech/topics/availability.md>), [Latency](<https://devfeed.tech/topics/latency.md>)

Tags: [ai](<https://devfeed.tech/tags/ai.md>), [api](<https://devfeed.tech/tags/api.md>), [availability](<https://devfeed.tech/tags/availability.md>), [chatgpt](<https://devfeed.tech/tags/chatgpt.md>), [cost](<https://devfeed.tech/tags/cost.md>), [gpt](<https://devfeed.tech/tags/gpt.md>), [interfaces](<https://devfeed.tech/tags/interfaces.md>), [openai](<https://devfeed.tech/tags/openai.md>), [reasoning](<https://devfeed.tech/tags/reasoning.md>), [release](<https://devfeed.tech/tags/release.md>), [speed](<https://devfeed.tech/tags/speed.md>)

## AI overview

The article explains GPT-5.6 as a family of three models--Sol, Terra and Luna--and describes how ChatGPT combines model selection with reasoning controls, automatic switching, Work mode and context-dependent availability. It also explains that GPT-5.5 Instant remains the default for fast conversations while GPT-5.6 Sol is used for higher-reasoning settings.

## Source excerpt

OpenAI has introduced GPT-5.6, but this release is not just another model replacing the previous one. There are three new models: Sol, Terra and Luna. ChatGPT also has new reasoning controls, a separate Work mode, automatic model switching and different model availability depending on where and how you use the product. This can be confusing [...] The post GPT-5.6 Sol, Terra and Luna: What Changed in ChatGPT? appeared first on RisingStack Engineering.