Claude Opus 5.5

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](#capabilities)):

ClaudeLanguageModel(name: .opus5, auth: auth)

ClaudeLanguageModel(name: .opus5_5, auth: auth)

Constants mirror API model IDs (`.opus5` is `claude-opus-5`) and carry each model's capabilities. New models ship as new constants in package releases.

Constants mirror API model IDs (`.opus5_5` is `claude-opus-5-5`) and carry each model's capabilities. New models ship as new constants in package releases.

Dateless model IDs like `claude-opus-5` (the 4.6 generation onward) are pinned snapshots, not evergreen pointers — the model behind an ID doesn't change underneath you.

Dateless model IDs like `claude-opus-5-5` (the 4.6 generation onward) are pinned snapshots, not evergreen pointers — the model behind an ID doesn't change underneath you.

Pin a Claude effort level for every request with `fixedEffort:`. It takes precedence over the framework's per-request reasoning hints. The API defaults to `high` when no effort is sent:

ClaudeLanguageModel(name: .opus5, auth: auth, fixedEffort: .xhigh)

ClaudeLanguageModel(name: .opus5_5, auth: auth, fixedEffort: .xhigh)

The framework's reasoning levels map to effort per request: `.light` → `low`, `.moderate` → `medium`, `.deep` → `high`, and `.custom` accepts a Claude effort name directly (`"xhigh"`, `"max"`). Levels a model doesn't accept are dropped — a reasoning level is a hint, not a contract.

Some models decline requests in certain policy areas, such as cybersecurity or biology. Name fallback models with `fallbacks:`, and the API retries a declined request on them, in order, within the same request:

ClaudeLanguageModel(name: .opus5, auth: auth, fallbacks: [.opus4_8])

ClaudeLanguageModel(name: .opus5_5, auth: auth, fallbacks: [.opus4_8])

You can name up to three fallbacks, and each one must be a model that the requested model allows as a fallback. To use the requested model's default fallback configuration instead, pass `fallbacks: .serverDefault`. The API then picks the fallback that's recommended for the policy area of the refusal, and for an area with no recommended fallback, the refusal stands.

If your app makes requests on behalf of its users, attribute each request to that user's profile. Your backend creates one profile per user with the API's user profiles endpoints (`/v1/user_profiles`). It stores the profile's ID with the user, and passes that ID to the app. The app then passes the ID when it creates the model:

ClaudeLanguageModel(name: .opus5, auth: auth, userProfileID: profileID)

ClaudeLanguageModel(name: .opus5_5, auth: auth, userProfileID: profileID)

The bridge sends the ID in the `anthropic-user-profile-id` header on every request, along with the `user-profiles-2026-08-18` beta. The API checks the ID, so an unknown ID fails the request. With `.proxied`, the relay has to forward both headers.

/// request on a substitute model, within the same request:

///

/// ```swift

/// ClaudeLanguageModel(name: .opus5, auth: auth, fallbacks: [.opus4_8])

/// ClaudeLanguageModel(name: .opus5_5, auth: auth, fallbacks: [.opus4_8])

/// ```

///

/// A model can decline after it has started to answer. The fallback model

let authMode: AuthMode

/// - Parameters:

/// - name: Claude model identifier. Use a constant (`.sonnet5`, `.opus5`,

/// - name: Claude model identifier. Use a constant (`.sonnet5`, `.opus5_5`,

/// `.haiku4_5`), or construct a ``ClaudeModel`` with explicit capabilities

/// for IDs not yet compiled in.

/// - auth: Credential mode. `.apiKey` for prototyping; `.proxied` with a

// on Sonnet 5 and Opus 4.7+ (Opus 4.6 still accepts them), `.xhigh` exists

// only on Sonnet 5 and Opus 4.7+, and `.max` requires the 4.6 generation

// or newer. Opus 5 and Fable 5 keep the Opus 4.8 request surface. Fable 5.1

// keeps it too, except that it also rejects forced tool use (`tool_choice`

// `any` / `tool`) — a `.required` tool-calling mode is a contract, so it is

// sent as-is and the API error names the field.

// and Opus 5.5 keep it too, except that they also reject forced tool use

// (`tool_choice` `any` / `tool`) — a `.required` tool-calling mode is a

// contract, so it is sent as-is and the API error names the field.

public static let opus5_5 = ClaudeModel(

id: "claude-opus-5-5",

capabilities: .init(

effortLevels: [.low, .medium, .high, .xhigh, .max],

adaptiveThinking: true,

structuredOutput: true,

imageInput: true

)

)

public static let fable5_1 = ClaudeModel(

id: "claude-fable-5-1",

capabilities: .init(

.prompt(.init(segments: [.text(.init(content: "Hi"))]))

])

)

for model: ClaudeModel in [.sonnet5, .opus4_8, .opus4_7, .sonnet4_6, .opus4_6] {

for model: ClaudeModel in [.opus5_5, .sonnet5, .opus4_8, .opus4_7, .sonnet4_6, .opus4_6] {

let built = try RequestBuilder.build(from: request, model: model)

#expect(built.request.thinking == .adaptive(display: .summarized))

}