Today, Tibo (@thsottiaux), an OpenAI engineer working on Codex and ChatGPT, announced on X that the 1 million-token context window for the GPT-5.6 Sol model in Codex, previously available only with API keys, can now also be used through ChatGPT accounts.
Tibo stated explicitly in the post: “GPT-5.6 Sol supports a 1 million-token context length in Codex. This was previously available only with API keys, but we’ve just flipped the switch, and it now works when using a ChatGPT account as well.”
This change means that users with subscription plans such as ChatGPT Plus and Pro can manually configure Codex—OpenAI’s AI coding agent—to enable its full context window of nearly 1.05 million tokens. According to the official GPT-5.6 Sol documentation, the model supports a context length of approximately 1,050,000 tokens.
The larger context window allows Codex to retain more code, tool output, and conversation history before automatically compressing earlier information. It is particularly useful for professional scenarios such as refactoring large codebases, complex debugging, and extended sessions.
Tibo also emphasized that Codex’s current default context length was chosen after balancing performance and cost, rather than set arbitrarily. He warned users: “The current default exists for a reason—we’ve tuned it to near perfection. But you can decide for yourself.”
Many users said the change addresses the context limitations subscribers previously encountered when working on large projects, particularly when maintaining and refactoring production-grade code repositories. Some developers also noted that, combined with Codex’s server-side compression mechanism, the default configuration is already efficient enough for most everyday tasks.
Other users said that enabling the 1 million-token context window significantly accelerates subscription quota consumption. Some reported that a single intensive session could use a large portion of their weekly allowance, so they recommend enabling it only when genuinely necessary rather than making it the everyday default.