pdfu published two demonstrations on 13 September 2026. In his own words, "iOS 27 and macOS Golden Gate have private hooks that let apps add Siri Extensions and replace Siri AI's server backend with third-party models," with Claude running as a Siri Extension via the Model Delegation API in App Intents, appearing in Siri's "Ask…" menu and supporting the same flow as the built-in ChatGPT extension . He notes this "Requires the private com.apple.developer.model-delegation entitlement."

For the second mechanism, pdfu writes that an app extension replaces Siri AI's server model with GPT-5.6 Terra using the Inference Providing protocol in Model Manager Services, with GPT-5.6 receiving Apple's native Siri planner prompt and tool definitions, making tool calls that perform system actions and receiving tool call results with personal data, and returning "a response through Siri AI's UI and voice, including interactive elements."

He adds that requests can be seen logged on OpenAI's platform and that it uses a private ExtensionKit extension point, com.apple.modelmanager.inferenceprovider.

MacRumors reported the same on 14 September: pdfu "has uncovered iOS 27 and macOS Golden Gate private frameworks that show Apple has designed its new Siri architecture to work with third-party AI models at what appears to be a surprisingly deep level," with Model Delegation allowing Claude to appear as a Siri extension in the same way as the existing built-in ChatGPT extension. In the demo, the user chooses Claude via an "Ask…" contextual menu and asks Siri to "Ask Claude" to set a reminder; Claude interprets the request and Siri creates the reminder, the implication being that if the request requires an Apple system feature, Claude hands the task back to Siri; in another example Claude receives a request to create a CSV file, something Siri itself cannot handle.

On availability, MacRumors states: the "Ask…" implementation is currently limited to the ChatGPT extension in the macOS 27 Golden Gate Release Candidate, so Claude is not yet available, and "Apple has not yet opened up the model delegation entitlement to third parties and it isn't front-facing to users, but it at least shows how extensively Apple has engineered Siri for future model interoperability." iClarified is blunter: "Claude is not available as a user-facing option, and Apple has not opened the Model Delegation entitlement to third-party developers. For now, the frameworks reveal what Apple's new Siri architecture is capable of, not what the company will ultimately make available." 9to5Mac: "You cannot yet activate this – it's visible in the code but not currently enabled."

On the regulatory framing: MacRumors says the EU's Digital Markets Act "may have helped shape Apple's approach here, as it requires Apple to give third parties effective access to iOS hardware and software features available to Apple's own services, and the European Commission has specifically said this principle extends to Siri."

On how the Claude extension was actually built, pdfu's own earlier technical write-up explains that his Claude bridge implements Apple's internal AgentIntent, and because the extension is sandboxed it forwards each request over a framed localhost connection to a companion LaunchAgent, which invokes the authenticated claude CLI with streaming JSON output and a scoped set of MCP tools.