---
name: Route work to the right Apple model
description: >-
  Teach an edge engineer to route tasks to SystemLanguageModel,
  PrivateCloudComputeLanguageModel, or CoreAILanguageModel using
  Dynamic Profile modifiers on iOS 27 and macOS 27.
---
# Route work to the right Apple model

Use this course to pick the smallest Apple language path that still does the job. Rules live in your app. Dynamic Profiles apply `.model` and `.reasoningLevel` on the active Profile.

## End-to-end agent recipe

1. Start with [lesson 01](01-three-apple-language-paths.llms.md) for the three LanguageModel paths.
2. Use [lesson 02](02-cost-latency-quality-rules.llms.md) to encode cost, latency, and quality.
3. Use [lesson 03](03-profiles-and-modifiers.llms.md) to apply the route with modifiers.
4. Use [lesson 04](04-build-the-router.llms.md) to build the router object.
5. Use [lesson 05](05-measure-and-fall-back.llms.md) to measure and fall back.
6. Use human HTML for reading and `.llms.md` files for agent execution.

## Constraints

- iOS 27 and macOS 27 only.
- Teach in Swift with SystemLanguageModel, PrivateCloudComputeLanguageModel, CoreAILanguageModel, and Dynamic Profiles. Do not use Python for the router.
- No LiteLLM. No LangChain. Apple models only unless you clearly mark a third-party server path as out of scope.
- One active Profile at a time.
- No Mermaid. No em dashes.
- Cite [WWDC26 241](https://developer.apple.com/videos/play/wwdc2026/241/) and [WWDC26 242](https://developer.apple.com/videos/play/wwdc2026/242/) lightly.

## Key concepts

- Route tasks to `SystemLanguageModel`, `PrivateCloudComputeLanguageModel`, or `CoreAILanguageModel`.
- Rules live in app code. Dynamic Profiles apply `.model` and `.reasoningLevel`.
- Pick the smallest Apple path that still does the job.
- One active Profile at a time on iOS 27 and macOS 27.

## Takeaways

- You can pick the smallest Apple model that still works and fall back without breaking privacy.
- You can write the rule in code and log the route key every request.
- You can switch the model with a Profile modifier instead of rebuilding the chat UI.

## Acceptance checks

- Every human lesson HTML has **Key concepts** and **Takeaways** sections before lesson-nav. The course home has the same two headings for the whole course.
- Five lessons and five briefs exist.
- All three model types are named.
- Course index lists SKILL.md and all briefs.

## Environment setup

Xcode 27. Foundation Models. Core AI if you route to a custom `.aimodel`.