OpenAI signed a multiyear agreement with Broadcom Inc. to collaborate on custom chips and networking equipment, marking the latest step in the startup’s ambitious plan to add computing infrastructure. Broadcom shares jumped.

After months of public pressure, OpenAI walked back part of its effort to create a more conventional for-profit company, but its restructuring plans still have not received the blessing of a major stakeholder: Microsoft Corp.

Microsoft Corp. and OpenAI are investigating whether data output from OpenAI’s technology was obtained in an unauthorized manner by a group linked to Chinese artificial intelligence startup DeepSeek, according to people familiar with the matter.