Apple–OpenAI ChatGPT deal, reported by @markgurman before WWDC — confirmed
@markgurman reported on May 11, 2024 that Apple was finalizing a deal with OpenAI. Apple confirmed ChatGPT integration on June 10, 2024.
Leaked on 11 May 2024

On May 11, 2024, @markgurman posted that Apple was finalizing a deal with OpenAI to power some generative AI features in the next iOS, and that talks with Google about Gemini were ongoing without a deal. (source: Bloomberg)
On June 10, 2024, Apple announced that ChatGPT would be integrated into iOS 18, iPadOS 18 and macOS Sequoia later that year, powered by GPT-4o and usable for free without an account. The Verge covered the announcement the same day.
Confirmed for the OpenAI part. The Google side of the post described talks in progress; the linked sources do not settle it.