Simon Willison’s Weblog·3 weeks ago·
34
● 20 sources
Anthropic released Claude Opus 5.5 and OpenAI released GPT-6 Sol and GPT-6 Luna about an hour later, with the article also describing early impressions from tests. GPT-6 Luna is priced at $0.10 per million input tokens and $0.50 per million output tokens. Model pricing cuts and cache-read discounts expand the ongoing price war, and the author shifts defaults to GPT-6 Sol and Claude Opus 5.5 while noting Opus 5.5 “max” can hit output token limits during an SVG task.
Anthropic released Claude Opus 5.5 while OpenAI launched two cheaper GPT-6 models, Sol and Luna, cutting prices for both vendors’ new systems. Anthropic set Opus 5.5 at $4 per million input tokens and $20 per million output tokens, and also cut cache reads by 60% to 20 cents. Both releases shift model usage toward lower-cost inference and faster/cheaper execution modes for common workloads, with added performance and safety improvements claimed by each company.
Anthropic released Claude Opus 5.5 to complete end-to-end coding tasks, including design specs, debugging, code generation, and testing. It charges $4 per million input tokens and $20 per million output tokens. Developers are expected to shift from starting code snippets to running agents that finish and verify larger project work, with safety rerouting to other Opus models when needed.
Anthropic released Claude Opus 5.5, positioning it as matching Claude Fable 5.1 on most tasks. Running it on typical default workloads costs 40% less than Opus 5. The update is API-only (no weights), comes with changes like thinking no longer being switchable off, added output watermarking for the EU AI Act, and revised pricing plus higher usage limits for paid plans.
llm released version 0.36 with new OpenAI models and related tooling changes. The update adds two new models, gpt-6-sol and gpt-6-luna. Plugin authors can mark models as not supporting conversations, which makes llm raise llm.ConversationNotSupported and prevents chat sessions when conversation history is provided.
GPT-6 Sol and GPT-6 Luna were introduced as two AI models for everyday work with different capability-versus-cost tradeoffs. The article provides no concrete number, date, or price details. As a result, users have two model options tuned for different budgets and performance needs.
Xiaomi released and open-sourced the MiMo-V2.6 series of natively omnimodal generative AI models, including MiMo-V2.6-Pro and a Flash variant. MiMo-V2.6-Pro supports a 1-million-token context window and the Pro-UltraSpeed variant delivers up to 20 times faster output than Pro at the same quality. The update changes availability and deployment by offering the models via Xiaomi’s AI Studio, MiMo Desktop, MiMo Code, and OpenRouter (with listed per-1M-token and cached-token pricing).
TypeSafe AI released the Jev AI model, which generates structured outputs from a predefined schema rather than writing text, and its API briefly stopped serving requests due to high developer demand. Jev reports end-to-end response times of 70 to 500 milliseconds and charges $0.042 per million input tokens with free output tokens. Developers are shifting toward schema-based “model routing” and other agent/tool workflows for faster, more type-safe automation, while independent verification and auditability of confidence and behavior remain open.
Xiaomi released the MiMo-V2.6 model family and published MiMo-V2.6-Pro’s weights on Hugging Face under an MIT license, claiming it as the top open-weight model on the Artificial Analysis Intelligence Index. MiMo-V2.6-Pro scored 46 points, up from 26 points for MiMo-V2.5-Pro. This raises the open-weight ceiling while establishing MiMo’s sparse mixture-of-experts models (plus Flash and UltraSpeed) as lower-cost options with updated availability and pricing for self-hosting and fine-tuning.
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