o3 and tools inside the reasoning
OpenAI opened access to o3 and the smaller o4-mini; for the first time a model could search the web, run code and look at images in the middle of its chain of reasoning.
Why it matters
Deliberation stopped being closed: while thinking, the model could go and fetch a fact it did not have and come back with it.
Until then tools were called before or after reasoning, and the chain worked only with what was already in context. Here the call became a step inside the chain: the model sees what it lacks, searches, reads, computes and continues. Images were handled the same way, with the model able to zoom into part of a drawing mid-thought. That shifted the line between a model and an agent: the difference stopped being architectural and became a matter of how long the system runs without a person.