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:

    Switch between Claude models. Applies to this session and future Claude Code sessions. For other/previous model names, specify with --model.
    
       1. Default (recommended)   Opus 4.6 · Most capable for complex work
       2. Opus (1M context)        Opus 4.6 with 1M context · Billed as extra usage · $10/$37.50 per Mtok
       3. Sonnet                   Sonnet 4.6 · Best for everyday tasks
       4. Sonnet (1M context)      Sonnet 4.6 with 1M context · Billed as extra usage · $6/$22.50 per Mtok
       5. Haiku                    Haiku 4.5 · Fastest for quick answers

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.

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.

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".

I can see that's what they mean now that I've read the replies, but when I first read that top comment I too parsed it as meaning 201k would cost the same as 999k (which admittedly did seem strange, hence I read the replies to confirm and sure enough that's not actually the case!)