From the source
OpenAI equipped the Responses API with an agent runtime that uses a shell tool and hosted containers to run secure, scalable agents with files, tools, and state.
From model to agent: Equipping the Responses API with a computer environment
Capability change
From the source
How OpenAI built an agent runtime using the Responses API, shell tool, and hosted containers to run secure, scalable agents with files, tools, and state.
openai.com