The Foundation Models framework: on-device AI for iPhone Duo apps
iOS 27 gives every app direct Swift access to the same on-device language models behind Apple Intelligence. Here is what the framework actually supports.
What it actually does
According to what we have seen published on Apple's developer site, the framework supports text generation, structured output, and tool-calling, entirely on-device and without requiring a network connection. That last point matters for iPhone Duo specifically — an app that generates or rewrites text inside a Split View pane, for example, does not need to round-trip to a server to do it, which keeps the feature usable offline and keeps user content off the network by default.
Not locked to Apple's own models
The framework is built around a LanguageModel protocol, which means it is not limited to Apple's first-party on-device models. According to the documentation we have seen, the same protocol can integrate cloud-based models such as Gemini or Claude, or open-source alternatives, giving developers a consistent Swift interface regardless of which model actually handles a given request.
Advanced features worth knowing about
A few capabilities go beyond basic text generation:
- Multimodal prompting, letting a single request combine text with other content types
- Dynamic profiles, which adjust model behavior for a given session rather than requiring a fixed configuration for the whole app
- An Evaluations framework specifically for verifying AI output quality and consistency before shipping
Why this matters for iPhone Duo apps specifically
Apps that use Split View well tend to pair a content-creation pane with a reference or control pane — think a writing app paired with research material, or a script editor paired with a teleprompter. On-device generation through the Foundation Models framework is a natural fit for exactly that pattern: summarizing, rewriting, or drafting content in one pane based on material visible in the other, without a network round-trip slowing down the interaction.
Our own PromptSlate Studio app already uses on-device generation for script drafting and rewriting — see our full PromptSlate Studio writeup for how that plays out in a shipped app.
For the rest of what is new across iOS 27, Xcode 27.1 beta, and macOS Tahoe 26.6, see our developer stack overview.
From the maker
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Spotted something to fix, or an app we should cover?
This article is independent research, cross-checked against Apple's developer documentation. If something's out of date, or you know an app that deserves a look, let us know — and if you're building for iPhone Duo yourself, we're happy to talk.
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