GPT-5.5 Pro and a million tokens of context: when you need it and what to use in Yenisei

GPT-5.5 Pro is the top model of the GPT lineup. Its main difference from GPT-5 Pro is that the context has grown to about 1M tokens and reasoning quality on long tasks has improved.

There are no closed GPT models in the Yenisei catalog. Our models with a window of about a million tokens and reasoning are DeepSeek V4 Pro (deepseek-pro), Kimi K3 (kimi-k3), GLM 5.3 (glm-5.3), and Yenisei Max (yenisei-max).

What a million tokens gives you

A large window changes how you formulate the task:

• you don't have to build RAG for a document that fits into the context whole;
• the model sees a long conversation without "forgetting" the beginning;
• a large code module is analyzed without slicing into chunks and stitching answers together.

When it is justified

When you need both the volume of context and the depth of reasoning at the same time: analytics on a thick report, working through a long technical dispute, reviewing a large code change in its entirety.

When it is not

If your requests fit into 100-200K tokens, you don't need a million-token window; you will be paying for a flagship with no benefit. GPT-OSS 120B (gpt-oss-120b) or DeepSeek V4 Flash (deepseek-flash) will give you the same result for less.

curl https://api.yenisei.ru/v1/chat/completions \
  -H "Authorization: Bearer $YENISEI_KEY" \
  -H "Content-Type: application/json" \
  -d '{
    "model": "deepseek-pro",
    "messages": [{"role": "user", "content": "Here is a 300-page report. Find contradictions between the conclusions of its sections."}]
  }'

The rule is simple: a million-token context is for a task that actually fills it. Otherwise it turns into an overpayment. Payment is in rubles, 1 credit = 1 ₽.