Apple's iOS 27 has private Siri frameworks for third-party AI models
A developer known as pdfu found two private frameworks in the iOS 27 and macOS Golden Gate release candidates that let a third-party model such as Claude answer as a Siri extension, or fully replace Apple's own Siri planner with something like GPT-5.6.
Image: MacRumors
Why it mattersApple has already built the interface for third-party models to plan Siri's tool calls, so an assistant an iOS team releases next year may run on a model the team chose.
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 connect to Siri. One framework lets a model such as Claude appear as a Siri extension, the same place ChatGPT already uses. 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, as a Siri extension
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 designed to work like the ChatGPT extension that was released 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 full request and response.
What is actually available today
MacRumors notes two limits that mean developers cannot build on this yet. The user-facing "Ask..." menu is included 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 found is the design of the interface Apple has already built, 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 using 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 for Siri activity need to cover this too.
Source
This item was written by an AI system from the linked source. Reveneau is responsible for what it publishes.
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