OpenAI DevDay 2025: AgentKit and the Apps SDK Turn ChatGPT Into a Platform

OpenAI held DevDay 2025 at Fort Mason in San Francisco on October 6, 2025: it shipped AgentKit, a toolchain for building agents, and the Apps SDK that lets developers embed apps inside ChatGPT; Sora 2 and GPT-5 Pro opened via API the same day.

Platformisation: AgentKit and the Apps SDK#

Per ZDNET's live coverage, the throughline was turning ChatGPT from a chat app into something closer to an operating system: services from partners such as Canva and Zillow can be called from inside the chat box. Two launches carry that story:

• AgentKit: ZDNET records Altman saying it has "everything you need to build, deploy and optimize agentic workflows." It builds on the Responses API, adds features for evaluating agent performance, keeps the Connectors registry wiring in data sources, and was available to everyone from launch day. The live demo used the Agent Builder inside OpenAI's platform.
• Apps SDK: OpenAI's official developer blog calls it one of the big launches at DevDay, for building rich app experiences directly within ChatGPT (OpenAI developer blog); the docs entry point is developers.openai.com/plugins. In its year-end roundup, OpenAI describes it as an open-source framework that extends the Model Context Protocol (MCP) so developers can build UIs alongside their MCP servers (OpenAI roundup).

Model and Codex updates from the same stage#

• Models: per ZDNET, GPT-5 Pro went into the API; Sora 2, unveiled to the public the previous week, also launched in the API; gpt-realtime-mini was announced too.
• Codex: per ZDNET, Altman said Codex usage was up 10x since early August and announced it was out of research preview and generally available.

No hardware — but a conversation#

ZDNET's headline states plainly that there was no hardware news; the event schedule included a chat between Sam Altman and Jony Ive.

(Revised October 12, 2026: the original said Spotify and Zillow were callable, while ZDNET's coverage names Canva and Zillow only — corrected; added OpenAI developer-blog and official-docs links.)