Sign users in to ChatGPT (OAuth 2.0 + PKCE, Keychain-backed) and call the Codex backend on the user's plan instead of your API key — no per-token billing. Two SwiftPM products — pick CodingPlanAuth alone for OAuth, add CodingPlanCodex when you want plan-bound chat / streaming / image generation / usage.

Install

.package(url: "https://github.com/atom2ueki/CodingPlanKit.git", from: "0.1.1"),

.target(
    name: "MyApp",
    dependencies: [
        .product(name: "CodingPlanAuth", package: "CodingPlanKit"),
        .product(name: "CodingPlanCodex", package: "CodingPlanKit"),
    ]
)

For iOS, register a custom URL scheme in Info.plist (e.g. myapp) so ASWebAuthenticationSession can return cleanly from the OAuth redirect.

Install the skill (let your code agent integrate it for you)

CodingPlanKit ships a Claude Code skill so an AI agent in your editor can integrate the SDK without you having to read the source. Inside Claude Code:

/plugin marketplace add atom2ueki/CodingPlanKit
/plugin install coding-plan-kit@coding-plan-kit

After that, prompts like "add CodingPlanKit auth to this iOS app" or "stream a Codex response with image generation" trigger the skill automatically. The skill reads from llms.txt for the full public surface, so it stays in sync with the source.

Quick start

import SwiftUI
import CodingPlanAuth

@MainActor
@Observable
final class SignIn {
    private let service: AuthService
    private let provider = OpenAIAuthProvider(callbackScheme: "myapp")
    private let browser = BrowserAuthSession()
    var credentials: Credentials?

    init() throws {
        // KeychainTokenStorage() throws when there's no servicePrefix and
        // no Bundle.main.bundleIdentifier (CLI/test contexts). In a normal
        // iOS/macOS app target the bundle id is always present and this
        // never throws — propagating rather than crashing keeps misconfigured
        // hosts (e.g. CLI tools without an explicit servicePrefix) loud.
        service = AuthService(storage: try KeychainTokenStorage())
    }

    func signIn() async throws {
        await service.register(provider)
        let session = try await service.beginLogin(providerId: "openai")
        let callbackURL = try await browser.authenticate(
            url: session.authURL,
            callbackScheme: "myapp"
        )
        credentials = try await service.completeLogin(
            session: session,
            with: callbackURL
        )
    }
}

Then call plan-bound APIs with CodingPlanCodex:

import CodingPlanCodex

let codex = OpenAICodexClient()

// One-shot:
let response = try await codex.createTextResponse(
    prompt: "Refactor this Swift function...",
    credentials: credentials
)

// Stream deltas:
for try await delta in codex.streamTextResponse(prompt: "...", credentials: credentials) {
    print(delta, terminator: "")
}

Documentation

• llms.txt — file-by-file index for AI agents and humans.
• DocC catalogs: CodingPlanAuth, CodingPlanCodex.

Acknowledgements

Built on

• SwiftWebServer — local loopback HTTP listener used for the OAuth callback during sign-in.

Inspired by

• openai/codex
• sugarforever/rn-ai-kit
• Vercel AI SDK
• badlogic/pi-mono

License

MIT © 2026 Tony Li