ChatKit can use your backend, but its official hosting matrix says OpenAI still hosts the iframe rendering the chat UI. Open SDK repositories do not establish a fully self-hostable renderer. New integrations should also avoid the retiring Agent Builder path.

ChatKit: backend control is not renderer control

Reviewed 2026-09-29.

The JavaScript integration repository and Python server SDK use Apache-2.0 licenses. They provide integration code, not evidence that the entire production ChatGPT interface has been released.

The official ChatKit hosting matrix explicitly places the rendering iframe at OpenAI in both hosted-backend and self-hosted-backend configurations. With your backend, you run the chat server and store messages and attachments. The externally hosted UI remains an architectural dependency.

The custom integration guide describes a Python ChatKitServer, streaming responses, and application-provided storage. Treat this as a server integration route rather than an independently hosted frontend build.

A separate lifecycle warning matters: the current API guide schedules Agent Builder shutdown for November 30, 2026, while retaining ChatKit and directing new work toward a custom server-side agent. Older examples recommending new Agent Builder workflows should not override that notice.

Recommendation: evaluate ChatKit for a convenient embed, not as the default choice for an offline or fully developer-hosted UI. No deployment or network audit was performed.