Apple Foundation Models

platform.claude.com · 2026-06-15 · by Long Nguyen ·generic
Use Claude on Apple platforms through the Foundation Models framework with the Claude for Foundation Models Swift package.

Apple Foundation Models

Loading...

Loading...

Loading...

Loading...

Loading...

Loading...

Loading...

Loading...

Loading...

Loading...

Loading...

Loading...

Copy page

Claude for Foundation Models is a Swift package that makes Claude available as a server-side language model in Apple's Foundation Models framework. The package conforms Claude to the framework's `LanguageModel` protocol, so you drive it with the same `LanguageModelSession` API you use for Apple's on-device model: `respond(to:)`, streaming, guided generation, and tool calling all work the same way.

Requests go directly from your app to the Claude API; Apple is not in the request path and does not see prompts or responses. Usage is billed to your Anthropic account at standard API pricing. Your app decides when to use Claude and when to use Apple's on-device model: pass whichever model you want to each session.

Beta. This package targets the Foundation Models server-side language model API introduced in the OS 27 betas. APIs may change before general availability.

Claude for Foundation Models is not a general-purpose Messages API client. Its public surface is the Foundation Models provider conformance plus the configuration types that reach it (`ClaudeLanguageModel`, `ClaudeModel`, `AuthMode`, `ClaudeServerTool`). For direct access to the Messages API in another language, see the Client SDKs.

##

Requirements

  • iOS 27, macOS 27, visionOS 27, or watchOS 27 (all in beta): the OS releases whose Foundation Models framework supports server-side language models
  • Xcode 27 (beta)
  • A Claude API key from the Claude Console for development. See Authentication for production options.

    • ##

    Install the package

    Add the package to your `Package.swift`:

    dependencies: [
  .package(url: "https://github.com/anthropics/ClaudeForFoundationModels.git", from: "0.1.0")
]

    Or in Xcode: File \> Add Package Dependencies… and enter the repository URL.

    Then add `ClaudeForFoundationModels` to your target's dependencies and import it alongside `FoundationModels`:

    import FoundationModels
import ClaudeForFoundationModels

    ##

    Quick start

    `ClaudeLanguageModel` is the entry point. Pass it to `LanguageModelSession` and use the session exactly as you would with any Foundation Models provider:

    import FoundationModels
import ClaudeForFoundationModels
    let model = ClaudeLanguageModel(
  name: .sonnet4_6,
  auth: .apiKey(ProcessInfo.processInfo.environment["ANTHROPIC_API_KEY"] ?? "")
)
    let session = LanguageModelSession(model: model)
let response = try await session.respond(to: "Plan a 4-day trip to Buenos Aires.")
print(response.content)

    The initializer also accepts `baseURL` (default `https://api.anthropic.com`), `timeout`, and `serverTools` (see Server-side tools).

    For a complete working program, the repository includes Examples/ClaudeExample, a runnable command-line target that streams a chat turn to the terminal, with a `--search` flag that enables server-side web search for the turn. Running it requires a macOS 27 host.

    ##

    Choosing a model

    Model identifiers are values of `ClaudeModel`. Use a compiled-in constant, or construct one with explicit capabilities for an ID that isn't compiled in yet (see Capabilities):

    ClaudeLanguageModel(name: .opus4_8, auth: auth)

    Constants mirror API model IDs (`.opus4_8` is `claude-opus-4-8`) and carry each model's capabilities. New models ship as new constants in package releases; check `ClaudeModel` in Xcode for the current list, and the Models overview to compare models.

    ###

    Capabilities

    Each `ClaudeModel` declares what it accepts: sampling parameters, effort levels, adaptive thinking, structured output, and image input. The package uses this to decide which request fields to send, because sending a field a model rejects is a hard error. The constants carry the right capabilities. For an ID that isn't compiled in, declare what the model accepts (there is deliberately no shorthand that guesses):

    let model = ClaudeModel(
  id: "claude-experimental-x",
  capabilities: .init(samplingParams: false, effortLevels: [.low, .high])
)
ClaudeLanguageModel(name: model, auth: auth)

    ###

    Effort

    Pin a Claude effort level for every request with `fixedEffort:`. It takes precedence over the framework's per-request reasoning hints, and it's the only way to request `.xhigh` or `.max`, because the framework's reasoning levels stop at high. The API defaults to `high` when no effort is sent:

    ClaudeLanguageModel(name: .opus4_8, auth: auth, fixedEffort: .xhigh)

    The level must be one the model accepts. Each `ClaudeModel` declares which of the five levels (`low`, `medium`, `high`, `xhigh`, `max`) its model takes, if any: some models don't accept effort at all.

    ###

    When to use Claude versus the on-device model

    Apple's on-device model is fast, private, and works offline, but it is sized for lightweight tasks. Escalate to Claude when you need larger context, frontier reasoning, or server-side tools such as web search and code execution. Because both use the same `LanguageModelSession` API, you can switch by swapping the `model:` argument.

    ##

    Authentication

    Set the credential with the `auth:` parameter.

    ###

    API key (development)

    Pass an API key directly while developing:

    ClaudeLanguageModel(name: .sonnet4_6, auth: .apiKey("YOUR_API_KEY"))

    A key bundled into an app is extractable from the shipping binary, and anyone who extracts it can make requests billed to your account. Use `.apiKey` for development only, and switch to a proxy before release.

    ###

    Proxy (production)

    For production, route requests through your own back end with `.proxied`. The relay at `baseURL` adds the Claude API credential server-side, so the app ships no key. The `headers` you provide are sent on every request so your proxy can authorize the caller. Pass `[:]` if it needs none:

    ClaudeLanguageModel(
  name: .sonnet4_6,
  auth: .proxied(headers: ["X-App-Token": "..."]),
  baseURL: URL(string: "https://api.yourapp.com/claude")!
)

    Your proxy receives standard Messages API requests, attaches the `x-api-key` header, and forwards them to `https://api.anthropic.com`.

    ##

    Streaming

    `streamResponse(to:)` returns the response incrementally. Each element is a cumulative snapshot of the response so far, not a delta:

    let stream = session.streamResponse(to: "Summarize today's top science stories.")
for try await partial in stream {
  print(partial.content)
}

    ##

    Structured output

    Annotate a type with `@Generable` and request it with `generating:`. The model returns a value of that type through structured outputs:

    @Generable
struct Trip {
  @Guide(description: "Destination city") var destination: String
  @Guide(description: "Length in days") var days: Int
}
    let response = try await session.respond(to: "Plan a trip to Tokyo.", generating: Trip.self)
print(response.content.destination)

    Structured output requires a model whose capabilities include it (all compiled-in constants do). If the chosen model does not, the package throws `LanguageModelError.unsupportedGenerationGuide` rather than silently degrading.

    ##

    Tool use

    ###

    Client-side tools

    The framework's `tools:` array works unchanged. Conform your types to `Tool`, pass them to `LanguageModelSession`, and the framework invokes them on the device when Claude calls them. See Tool use with Claude.

    let session = LanguageModelSession(model: model, tools: [FindRestaurantsTool()])

    ###

    Server-side tools

    Server tools (web search, web fetch, and code execution) run on Anthropic's infrastructure within a single round trip, with nothing for the framework to invoke on the device. Configure them per model with `serverTools:`:

    let model = ClaudeLanguageModel(
  name: .sonnet4_6,
  auth: auth,
  serverTools: [
    .webSearch(maxUses: 5),
    .codeExecution,
  ]
)

    `.webSearch` and `.webFetch` accept optional `allowedDomains`, `blockedDomains`, and `maxUses`. Server tool activity surfaces in the transcript as `ClaudeServerToolSegment` custom segments.

    `serverTools` is configured on `ClaudeLanguageModel` rather than on `LanguageModelSession` because the session type is Apple's. To use different server-tool sets per conversation, construct multiple `ClaudeLanguageModel` instances.

    ##

    Images

    Models whose capabilities include image input declare the framework's vision capability. Pass image content through the framework's standard session API; the package converts it to the Claude API's image format. See Vision for image requirements.

    ##

    Error handling

    The package maps Claude API errors onto Apple's `LanguageModelError` cases where one fits: context-window overflow surfaces as `.contextSizeExceeded`, HTTP 429 as `.rateLimited`, a request past the configured timeout as `.timeout`. Provider errors with no framework equivalent surface as `ClaudeError`. Pattern-match to drive product flows:

    do {
  let response = try await session.respond(to: prompt)
  print(response.content)
} catch ClaudeError.missingCredential {
  // Prompt for an API key.
} catch let error as LanguageModelError {
  // Framework-shaped errors (rate limits, guardrails, context length, decoding).
} catch {
  // Transport errors.
}

    A common pattern is to catch `.rateLimited` and fall back to `SystemLanguageModel` for that turn, queue the request, or surface a retry affordance.

    ##

    Feature support

    The package surfaces the Messages API capabilities that the Foundation Models provider protocol can express. Features with no representation in Apple's protocol are not available through it, including:

  • Prompt caching controls (the package applies prompt caching automatically; cache TTL and breakpoint placement are not configurable)
  • Stop sequences
  • Batch processing
  • Files API
  • Token counting
  • Beta headers

##

Additional resources

| Reference | Covers | | --------------------------------------------------------------------------------------------------- | ----------------------------------------------------------------------------------------- | | Apple Foundation Models documentation | LanguageModelSession, @Generable, Transcript, Tool, and the rest of the framework surface | | ClaudeForFoundationModels on GitHub | Source, the runnable example, and the issue tracker | | Claude API reference | The underlying Messages API |

The package is licensed under Apache 2.0. Bug reports are welcome through GitHub issues. External pull requests are not being accepted during the beta period.

Was this page helpful?



platform.claude.com · 78 links

Comments (0)

No comments yet