There is extra cost for >272K:
> For models with a 1.05M context window (GPT-5.4 and GPT-5.4 pro), prompts with >272K input tokens are priced at 2x input and 1.5x output for the full session for standard, batch, and flex.
Taken from https://developers.openai.com/api/docs/models/gpt-5.4
Good find, and that's too small a print for comfort.
It's also in the linked article:
> GPT‑5.4 in Codex includes experimental support for the 1M context window. Developers can try this by configuring model_context_window and model_auto_compact_token_limit. Requests that exceed the standard 272K context window count against usage limits at 2x the normal rate.
Anthropic literally don't allow you to use the 1M context anymore on Sonnet and Opus 4.6 without it being billed as extra usage immediately.
I had 4.5 1M before that so they definitely made it worse.
OpenAI at least gives you the option of using your plan for it. Even if it uses it up more quickly.
Is that why it says rate limit all the time if you switch to a 1M model on Claude now? It kept giving me that so I switched to API account over the weekend for some vibe coding ran up a huuuuge API bill by mistake, whooops.
Wow, that's diametrically the opposite point: the cost is *extra*, not free.
Diametrically opposite to tokens beyond 200K being literally free? As in, you only pay for the first 200K tokens and the remaining 800K cost $0.00?
I don't think that's a fair reading of the original post at all, obviously what they meant by "no cost" was "no increase in the cost".
Which, Claude has the same deal. You can get a 1M context window, but it's gonna cost ya. If you run /model in claude code, you get: