import BrowserKit

BEAvailability.isEligible(for: .webBrowser) { eligible, error in
    if eligible {
        // Device supports alternative browser engines
    } else {
        // Fall back or show explanation
    }
}

Host App (UI, coordination)
  |
  |-- XPC --> Web Content Extension (HTML parsing, JS, DOM)
  |-- XPC --> Networking Extension (URLSession, sockets)
  |-- XPC --> Rendering Extension (Metal, GPU, media)

import BrowserEngineKit

// Web content (one per tab or iframe)
let contentProcess = try await WebContentProcess(
    bundleIdentifier: nil,
    onInterruption: {
        // Handle crash or OS interruption
    }
)

// Networking (typically one instance)
let networkProcess = try await NetworkingProcess(
    bundleIdentifier: nil,
    onInterruption: {
        // Handle interruption
    }
)

// Rendering / GPU (typically one instance)
let renderingProcess = try await RenderingProcess(
    bundleIdentifier: nil,
    onInterruption: {
        // Handle interruption
    }
)

let connection = try contentProcess.makeLibXPCConnection()
// Use connection for inter-process messaging

contentProcess.invalidate()

import BrowserEngineKit

final class MyWebContentExtension: WebContentExtension {
    override func handle(xpcConnection: xpc_connection_t) {
        // Set up message handlers on the connection
    }
}

import BrowserEngineKit

final class MyNetworkingExtension: NetworkingExtension {
    override func handle(xpcConnection: xpc_connection_t) {
        // Handle network request messages
    }
}

import BrowserEngineKit

final class MyRenderingExtension: RenderingExtension {
    override func handle(xpcConnection: xpc_connection_t) {
        // Handle rendering commands
    }
}

// Enable CoreML in the rendering extension
extension.enableFeature(.coreML)

// Grant foreground priority to an extension
let grant = try contentProcess.grantCapability(.foreground)

// ... extension does foreground work ...

// Relinquish when done
grant.invalidate()

let mediaEnv = MediaEnvironment(webPage: pageURL)
let grant = try contentProcess.grantCapability(
    .mediaPlaybackAndCapture(environment: mediaEnv)
)
try mediaEnv.activate()
let captureSession = try mediaEnv.makeCaptureSession()

// In the web content extension, after setup:
extension.applyRestrictedSandbox(revision: .revision2)

import BrowserEngineCore

// BE_JIT_WRITE_PROTECT_TAG is used with pthread_jit_write_protect_np
// to control JIT memory page permissions

ARCHS[sdk=iphoneos*]=arm64e

// WRONG - content extension has no path to other extensions
let contentProcess = try await WebContentProcess(
    bundleIdentifier: nil, onInterruption: {}
)
// Immediately start sending work without connecting to networking/rendering

// CORRECT - broker connections through the host app
let networkEndpoint = try await networkProxy.getEndpoint()
let renderEndpoint = try await renderProxy.getEndpoint()
try await contentProxy.bootstrap(
    renderingExtension: renderEndpoint,
    networkExtension: networkEndpoint
)

// WRONG - extensions cannot launch other extensions
// (inside a WebContentExtension)
let network = try await NetworkingProcess(...)

// CORRECT - only the host app launches extensions
// Host app creates all processes, then brokers connections

// WRONG
contentProcess.invalidate()
let conn = try contentProcess.makeLibXPCConnection()  // Error

// CORRECT - create a new process if needed
let newProcess = try await WebContentProcess(
    bundleIdentifier: nil, onInterruption: {}
)

// WRONG
if Locale.current.region?.identifier == "DE" {
    useAlternativeEngine()
}

// CORRECT - use the system eligibility API
BEAvailability.isEligible(for: .webBrowser) { eligible, _ in
    if eligible { useAlternativeEngine() }
}