Apple's iOS 27 Siri has private frameworks that let Claude and GPT run as the model

MacRumors reports that a developer who publishes on X as pdfu has found two private frameworks in the iOS 27 and macOS Golden Gate release candidates that let a third-party AI model plug into Siri. One framework lets a model such as Claude appear as a Siri extension, the same slot ChatGPT already sits in. The other lets a model such as GPT-5.6 replace Apple's server-side Siri planner outright and receive Apple's own prompt and tool definitions.

Model Delegation, the extension slot

In pdfu's video, embedded by MacRumors from an X post dated 13 September 2026, a macOS user opens the new "Search or Ask" bar, picks Claude from an "Ask..." menu, and asks Siri to "Ask Claude" to set a reminder. Claude reads the natural-language request, then hands the reminder back to Siri, which writes it into the Reminders app. A second clip shows the same Claude extension writing a CSV file inside the Siri app window, a task Siri on its own cannot do. The mechanism is called Model Delegation and is scoped to work like the ChatGPT extension that shipped in earlier Apple Intelligence builds.

Model Manager Services, replacing the Siri planner

The second protocol goes further. According to MacRumors' reading of the frameworks, an "Inference Providing" protocol inside Model Manager Services lets Apple's own server-side Siri model be replaced. In pdfu's demonstration, an app extension routes to GPT-5.6 Terra, which receives Apple's native Siri planner prompt and Apple's tool definitions. GPT-5.6 then plans the tool calls: it reads emails from a chosen topic, summarises them, and sends a message to a contact through the Messages app. The response is logged in the demo user's OpenAI platform account, which is how pdfu was able to show the round trip.

What actually ships today

MacRumors notes two limits that keep this from being a plug-in you can build against tomorrow. The user-facing "Ask..." menu ships in macOS 27 Golden Gate Release Candidate only for the built-in ChatGPT extension, so Claude and other models cannot yet be selected from the Siri UI. Model Delegation entitlements are still closed to third-party developers. What pdfu has surfaced is the shape of the interface Apple has already engineered, well ahead of any public API a team could call from an app store submission this week.

MacRumors links Apple's approach to the European Union's Digital Markets Act, which requires Apple to give third parties effective access to iOS features Apple uses for its own services, and quotes the European Commission on Siri specifically falling under that principle.

For an iOS team, this is a useful preview of what the interface will look like when Apple opens it. The interesting design choice is that Apple keeps its own planner prompt and its own tool definitions on the device, and the third-party model plans against Apple's schema. A team that builds a Siri extension chooses which model reads Apple's prompt and calls Apple's tools; the set of tools stays Apple's to define. The audit path also changes: a request the user makes into Siri may leave the machine and reach an OpenAI or Anthropic account log, so review policies around Siri activity need to widen accordingly.

Source

Reported by MacRumors. Original finding on X: pdfu.