Microsoft shipped a decision model built on Alibaba’s open weights
Microsoft announced Microsoft-Decision-1 on Friday: a small model that takes a question and a fixed set of options and returns a calibrated probability for each in a single pass, built for routing, classification, verification and workflow control. It is live in Microsoft Foundry and on OpenRouter at $0.042 per million input tokens with output tokens free. Microsoft says it post-trained Alibaba’s open-weight Qwen3.5-9B to build it, and will rebase the model on its own MAI and OpenAI models later.
The claims are all its own. Microsoft says Decision-1 took the highest accuracy in a 36-benchmark comparison of nearly 150,000 questions kept blind from training, and was the fastest measured, 2.5 times quicker than the runner-up H2O-Lightning-4B v1.1 and 35 times quicker than GPT-6 Sol. It arrives days after OpenAI put its own Decisions API into public beta, and Microsoft’s published benchmark set includes Strands-Decider 2B, the open-source decider AWS released on Wednesday.

WHY IT MATTERS
The category the week produced now has a shape: a broad model does the thinking and a cheap single-pass scorer handles the micro-decisions an agent loop makes thousands of times - keep going, retry, hand off, is this grounded in what the user said. That Microsoft built its entry from a Chinese open-weight base rather than training one is the quieter point: the value is moving into the harness around the model, where open weights are good enough and the cost is the product. For anyone running agents, the move is to stop spending a frontier call on every branch. The caveat deserves one line: every number is Microsoft’s own with no third-party evaluation yet, and the weights are not downloadable.













