OpenAI Agents API: hosted sandboxes get the Artifact SDK, plus an Ultrafast mode

OpenAI's API changelog for October 16, 2026 (labelled v1/agents) lists two changes:

• OpenAI-hosted sandboxes in the Agents API now include the Artifact SDK and skills for creating and editing spreadsheets, presentations and Word documents.
• A new Ultrafast mode: set agent.service_tier to ultrafast with a supported model to reduce the time between generated tokens.