GPT-5.5, DeepSeek V4 preview and Kimi K2.6 in one week

Three launches this week, and the price tags tell the story as much as the scores.

GPT-5.5

OpenAI released GPT-5.5 on April 23, with an API snapshot dated the same day and a Pro variant for harder problems. The model page lists a context of 1,050,000 tokens, up to 128,000 output tokens, a December 2025 knowledge cutoff, and reasoning levels from none through xhigh, with medium as the default. It takes text and images and returns text. Pricing is $5 per million input tokens, $0.50 cached and $30 output, and prompts over 272K tokens cost double on input and 1.5 times on output for the whole session.

That long-prompt rule is the line I would put in front of anyone planning to stuff a full tender pack into one call. The headline number is cheap enough. The surcharge makes a big file expensive.

DeepSeek V4 and Kimi K2.6

DeepSeek published a V4 preview on April 24. V4-Pro has 1.6T total parameters with 49B active, and V4-Flash has 284B total with 13B active. A one-million-token context is now the default across DeepSeek's services, both models have thinking and non-thinking modes, and the API accepts OpenAI and Anthropic request formats. The old deepseek-chat and deepseek-reasoner names retire after July 24. DeepSeek calls Pro the open-source leader on agentic coding. That is the vendor's claim.

Moonshot's Kimi K2.6 came on April 20, a 1T-parameter mixture-of-experts model with 32B active. The announcement stresses long coding runs, with over 12 hours of continuous execution and 4,000 or more tool calls, and swarms of up to 300 parallel sub-agents. The license is a modified MIT.

Everything else

OpenAI also released GPT Image 2 on April 21, which showed up in ChatGPT as Images 2.0. Xiaomi put MiMo V2.5 and V2.5 Pro out on April 23. Anthropic moved memory for Managed Agents into public beta the same day. Two papers caught my eye on the research side: OpenGame, on agents that write games, and LLaDA2.0-Uni, a diffusion language model aimed at both understanding and generating multimodal content.

What I'd watch next: whether anyone runs V4-Flash on a real set of bid documents and reports cost per page, because that number decides whether it replaces my cheap tier.