OpenAI and AWS announced a deepened partnership on April 28, 2026—one day after OpenAI's exclusive Microsoft Azure arrangement expired. GPT-5.5 and GPT-5.4 are available in limited preview on Amazon Bedrock alongside Codex, OpenAI's agentic coding system, and a new Bedrock Managed Agents capability. Amazon committed up to $50B in investment in OpenAI ($15B initial, $35B conditional) and a $100B infrastructure expansion including 2 GW of Trainium capacity over eight years. Codex can now run within existing AWS environments using models served from Bedrock, without moving customer data.