iOS 27 shipped the new Siri. Hidden code lets Claude or GPT take its place.

Apple released iOS 27, iPadOS 27, macOS 27 Golden Gate, watchOS 27, visionOS 27, and tvOS 27 on September 14. The Apple newsroom post leads with Siri: a version it calls "more intelligent, knowledgeable, and capable," that understands personal context, answers questions about what is on screen, drafts text under a feature called Write with Siri, and gets its own app that syncs across devices through iCloud. The day before, a developer known as pdfu posted videos of the same release candidate builds running Claude and GPT-5.6 in Siri's place.

What shipped

The Siri AI features ship first in English, in beta, with French, Japanese, Korean, Portuguese, and Spanish due in October, per Apple's post. They are unavailable in China, and on iPhone, iPad, and Apple Watch they are initially limited in the EU; Mac and Vision Pro are excepted. Supported hardware starts at iPhone 15 Pro, M1 or later iPads and Macs, and the A18 Pro MacBook Neo. TechCrunch's Ivan Mehta reports the macOS version answers questions about a window's contents with Command, Shift, and Space.

The newsroom post does not name the model behind Siri, and it does not mention any third-party model.

What the code permits

On September 13, pdfu, posting as @itspdfu on X, showed two private mechanisms in the iOS 27 and macOS Golden Gate release candidates, and MacRumors, Neowin, and iClarified reported them the next day. The first is a Model Delegation API in App Intents. In the video, Claude appears as a Siri extension in the same "Ask..." menu that Apple's built-in ChatGPT option uses, sets reminders, and writes a CSV file, handing system requests back to Siri when it needs to.

The second goes deeper. A protocol called Inference Providing, in a framework named Model Manager Services, lets another model replace Apple's server-side Siri model outright. In pdfu's demonstration, GPT-5.6 receives Apple's own Siri planner prompt and tool definitions, reads the user's email, summarizes it, and sends a message, with Siri presenting the result. iClarified's summary of what is live today: only ChatGPT is exposed in the "Ask..." flow, Claude is not a user-facing option, and Apple has not opened the Model Delegation entitlement to third-party developers. Apple has not commented on either mechanism.

MacRumors ties the design to the EU Digital Markets Act, which requires Apple to give rivals "effective access to iOS hardware and software features available to Apple's own services." That is MacRumors' reading. Apple has not said why the code exists. What no one outside Apple has is a date, or a statement that the entitlement will ever open. A private framework in a release candidate is evidence of intent, not a roadmap.

Why a build studio cares

We build iOS apps and we build agents, and the second mechanism is the one that changes the job. If Siri's planner prompt and tool definitions can be handed to a model the user picks, then an App Intent we ship today is a tool call that a model Apple did not train will make tomorrow. The intent surface becomes the contract, and it has to hold for a planner we cannot test against. That is a concrete reason to keep intents narrow and typed, starting now, rather than a reason to wait for Apple's announcement.

The first mechanism matters less to us and more to clients who ask which assistant their product should integrate with. The answer this week is the same as last week: ChatGPT, because that is the only one Apple has turned on. The difference is that the answer now comes with a question attached, how long it stays true, and nobody outside Cupertino has said.

Next step: read Apple's newsroom post for what shipped, then MacRumors and iClarified for the videos and what is and is not enabled. If your app exposes App Intents and you want them reviewed as a contract rather than a convenience, write to us at hello@gattyworks.com.