Codex reportedly enables a 1M-token context for GPT-5.6 Sol with ChatGPT accounts

CommunityAboutPricing Log inSign up All posts # How to Enable GPT-5.6 Sol’s 1M Context Window in Codex • Published on Aug 18, 2026 • 35min read CodeGlitch proposes testing the same large Codex task under the default and one-million-token context, then comparing compactions, repeated work, and corrections. This is a test plan, not a benchmark result — Source Codex can now run GPT-5.6 Sol with a one-million-token context budget through a simple configuration change. The setting works with Codex sessions authenticated through ChatGPT accounts, not only API-key workflows. The configuration is short: toml ``` model = "gpt-5.6-sol" model_context_window = 1000000 model_auto_compact_token_limit = 900000 ``` [...] ### Does GPT-5.6 Sol support one million tokens? Yes. OpenAI’s current model page lists a 1,050,000-token context window for GPT-5.6 Sol. The Codex configuration shown here sets a one-million-token session budget. ### Where is the Codex configuration file? The user-level

A larger context window lets Codex retain more code, tool output, and conversation history before summarizing older material. You need a model that supports it. GPT-5.6 Sol, for example, has a documented 1,050,000-token context window. Open ~/.codex/config.toml and add or update these settings at the top level, before any [section] headers: `model = "gpt-5.6-sol"` `model_context_window = 1000000` `model_auto_compact_token_limit = 900000` `model = "gpt-5.6-sol"` `model_context_window = 1000000` `model_auto_compact_token_limit = 900000` The first setting selects the model. The second tells Codex to use a one-million-token context budget. The third starts automatic history compaction around 900,000 tokens, leaving some headroom. [...] Restart the Codex client and start a new session after saving. To try the configuration for a single CLI session without changing your defaults: `codex -m gpt-5.6-sol` `-c model_context_window=1000000` `-c model_auto_compact_token_limit=90000

### What issue are you seeing? GPT-5.6's default Codex context configuration appears to allow sessions to enter the higher-usage pricing band without the user explicitly opting into a larger context. The current model metadata reports a 372,000-token context window with a 95% effective-context multiplier, yielding an effective window of approximately 353,400 tokens. OpenAI's GPT-5.6 model pricing documentation states that prompts with more than 272K input tokens are priced at 2x input and 1.5x output for the full request. That means the default effective context can extend roughly 81K tokens into the higher-cost band: Raw context: 372,000 Effective context: 353,400 Higher-cost threshold: 272,000 Exposure above threshold: approximately 81,400 tokens [...] Skip to content ## Navigation Menu Sign in Appearance settings Sign in Sign up Appearance settings You signed in with another tab or window. Reload to refresh your session. You signed out in another tab or window. R

Tibo@thsottiaux GPT-5.6 Sol 1M in Codex. This used to only work for API keys, but we just flipped the switch and works for usage through ChatGPT accounts now too. The same warning applies, there is a reason the current context length is the default, we have tuned it to ~perfection. But you do Tibo @thsottiaux Here is how to enable a 1M-token context window in Codex for GPT-5.6 Sol. Even though we have tuned the context limit in Codex to be set optimally when it comes to performance and cost, this is a common ask, so here it is documented. A larger context window lets Codex retain 12:13 AM · Aug 17, 2026 · 1.57M Views 618 Replies · 253 Reposts · 6.05K Likes The earlier failures, the model catalog, and my long-context tests explain why this guide needs more than one TOML setting. [...] 146 Replies · 5 Reposts · 886 Likes The next day he posted the configuration values for a one-million-token window. They were familiar. I had already tried the same configuration months ago and foun

@thsottiaux Tibo @thsottiaux Aug 16 Here is how to enable a 1M-token context window in Codex for GPT-5.6 Sol. Even though we have tuned the context limit in Codex to be set optimally when it comes to performance and cost, this is a common ask, so here it is documented. A larger context window lets Codex retain 12:13 AM · Aug 17, 20261.6MViews 613 @thsottiaux Tibo @thsottiaux GPT-5.6 Sol 1M in Codex. This used to only work for API keys, but we just flipped the switch and works for usage through ChatGPT accounts now too. The same warning applies, there is a reason the current context length is the default, we have tuned it to ~perfection. But you do you! @thsottiaux Tibo @thsottiaux Aug 16 [...] Log inSign up ## Post # Tibo on X: "GPT-5.6 Sol 1M in Codex. This used to only work for API keys, but we just flipped the switch and works for usage through ChatGPT accounts now too. The same warning applies, there is a reason the current context length is the defau

At the same time, local configuration changes on the client side cannot reliably unlock a larger window in the cloud; large-context operation still requires cloud-side cooperation. Therefore, standalone API-key calls and Codex client sessions through a ChatGPT subscription do not share the same context quota conventions. [...] When using the ChatGPT subscription channel, users do not directly pay for overages, but this still imposes server-side resource and capacity planning pressure, and 272K happens to coincide with the billing boundary. In the issue #19464 discussion, engineering contributor Eric Traut mentioned that supporting a 1M-level context on the client side requires server-side implementation and capacity planning. This reflects backend resource considerations, but cannot be taken as an official explanation of the motive behind this version adjustment. [...] The underlying API model specification is clear and stable. According to the GPT-5.6 Sol API page and the GPT-5.5 API