Reasoning · mobile

Use o3 Pro with Swift (iOS)

Updated 2026-05-21 · By XALEN

How to use o3 Pro (Reasoning, ~1T) with Swift (iOS). Install, authenticate, and make your first API call in minutes. Working code example included.

Model
o3 Pro
~1T · 200K context · $0.15 input
Framework
Swift (iOS)
mobile · SPM: xalen-swift

1. Install

SPM: xalen-swift

2. Code

import Foundation

func chat(_ question: String) async throws -> String {
    var request = URLRequest(url: URL(string: "https://api.xalen.io/v1/chat/completions")!)
    request.httpMethod = "POST"
    request.setValue("Bearer xln_test_YOUR_KEY", forHTTPHeaderField: "Authorization")
    request.setValue("application/json", forHTTPHeaderField: "Content-Type")
    request.httpBody = try JSONSerialization.data(withJSONObject: [
        "model": "o3-pro",
        "messages": [["role": "user", "content": question]]
    ])
    let (data, _) = try await URLSession.shared.data(for: request)
    let json = try JSONSerialization.jsonObject(with: data) as! [String: Any]
    let choices = json["choices"] as! [[String: Any]]
    let message = choices[0]["message"] as! [String: String]
    return message["content"]!
}

o3 Pro with Other Frameworks

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Last updated: 2026-05-21