OpenAI has officially launched the Agents API, which opens up the harness functionality of Codex through a single core REST endpoint, requiring the use of a specified Beta request header. The API divides core concepts into five categories: Agent, Environment, Session, Events, and Items. Its workflow includes creating a session, assigning tasks, following up on tasks, and subsequent operations. Its managed harness has capabilities such as running code, calling tools, context compression, and multi-agent collaboration. The tools it calls are divided into three categories, and the environment can be either self-hosted or hosted in OpenAI's managed sandbox. In terms of pricing, billing is based on model, tool, and sandbox usage. Data is only retained in the United States and does not support zero data retention. The SDK supports multiple languages. The community has discussed the necessity of managed sessions and the ambiguity of pricing, with skeptics arguing that this could lead to vendor lock-in, while supporters value the cost savings from not having to build their own sandbox. Essentially, this API server-sideizes the harness functionality that was originally bundled in CLI and IDE plugins, helping relevant teams avoid the workload of building their own orchestration layer, but requiring session state and execution environments to be managed by OpenAI.