Amazon announced what it called a “major expansion” of its partnership with ChatGPT maker OpenAI on Tuesday, a day after the artificial intelligence company said it was loosening its ties to longtime backer Microsoft. OpenAI CEO Sam Altman said the collaboration with Amazon's cloud computing division, Amazon Web Services, would involve co-developing a new platform for AI agents that can do computer-based work on people's behalf. Altman spoke via prerecorded video message to an Amazon event in San Francisco at the same time as he was appearing in federal court across San Francisco Bay in Oakland for a civil trial brought by rival OpenAI co-founder Elon Musk.