Introduction
March 2025
Major events
March was the month the frontier models learned to think on request and agents began to act. Claude 3.7 Sonnet offered an extended-thinking mode with a thinking budget developers could set; OpenAI previewed GPT-4.5, built on scaled-up pre-training rather than added reasoning; Google introduced Gemini 2.5 Pro, built to reason before answering; and OpenAI’s native image generation in GPT-4o drew wide attention. Manus previewed an agent that could build a website or plan a trip, and Moderne and Salesforce moved agents into code maintenance and business workflows.
Capital and policy rounded out the month. OpenAI submitted its proposals for the US AI Action Plan, SoftBank agreed to buy the chip designer Ampere for $6.5 billion, Nvidia expanded its Cosmos tools for robotics, and Elon Musk folded X into xAI in an all-stock deal. The Computer History Museum, meanwhile, released the original 2012 source code of AlexNet.
Patterns and trends
Reasoning became something users and developers could switch on and budget, and measurement grew more demanding to keep up. METR estimated that the length of tasks agents could complete was doubling roughly every seven months; ARC-AGI-2 showed how far current systems fell short on abstract puzzles; and a working paper found ChatGPT less swayed than federal judges by legally irrelevant facts. The open-model world kept pace with the closed one: DeepSeek published a week of its infrastructure tools and updated V3, Alibaba opened Wan2.1 for video, Baidu released ERNIE 4.5 and the ERNIE X1 reasoning model, and Skywork extended reasoning to images.
Long-term threads
Reasoning on request spread through the year: o3 and Gemini 2.5 Flash’s adjustable thinking in April, Claude Opus 4 and Sonnet 4 in May, GPT-5’s router between fast and deep answers in August, and GPT-5.1’s adaptive reasoning in November. METR’s doubling estimate gave a yardstick for the agents that followed, from ChatGPT agent in July to coding agents built for long tasks in November. GPT-4o’s image generation reached developers in April, and OpenAI’s policy proposals fed the process that produced America’s AI Action Plan in July.