April 2026 platform changes: Codex agent, GPT-5.4 family GA, model deprecations, and the Responses API migration timeline. Part of the free OpenAI Academy โ every lesson below is open to everyone, no signup required.
What's New in April 2026 Codex Agent OpenAI expanded Codex from a code-generation model into a full autonomous coding agent rewritten in Rust. Availab...