alphax_native 1.0.0-rc.2

Platform transport adapters for AlphaX using Dart IO, Cronet, and URLSession.

alphax_native

Platform transports for the AlphaX API.
Use the platform networking stack where it is supported, with a truthful Dart IO fallback.

Platform matrix · Waypoint example · Apache-2.0

At a glance

Target	Transport supplied
Android API 24+	Cronet/HttpEngine provider with H1/H2/H3 capability where the provider and network permit it
iOS 15+ / macOS 12+	URLSession with platform-negotiated H1/H2/H3 and completion-time metadata
Linux / Windows	Dart IO fallback with H1 support and no authoritative H2/H3 reporting
Web	Not supplied here; use the separate alphax_web Fetch adapter

Start here

1. Add alphax and alphax_native to the application.
2. Follow choose a transport for the platform branch.
3. Keep the request code shared across platforms.
4. Read TLS and proxy behavior before enabling optional security or routing controls.

alphax_native gives an AlphaX application the platform transport selected for each supported target while keeping the same Dart request code everywhere. It supplies Dart IO, Android Cronet/HttpEngine, and Apple URLSession adapters behind the transport-neutral alphax API.

Why use it?

Use alphax_native when you want to:

• use Android's supported Cronet provider for H1/H2/H3-capable networking;
• use Foundation URLSession on iOS and macOS;
• keep an H1 Dart IO fallback for Linux and Windows;
• stream responses and file transfers with cancellation and progress;
• inspect the protocol that actually completed each request;
• keep TLS, proxy, redirect, and error behavior behind AlphaX contracts.

H3 is opportunistic. The selected provider, server, proxy, and network decide whether an individual request uses H3. AlphaX reports the actual result and fails closed when an explicit protocol requirement cannot be met.

When should I choose this package?

Choose alphax_native for a new Flutter application or when an existing AlphaX application needs the platform transport implementations. Use alphax alone for transport contracts and a custom transport, or use alphax_dio if your application already uses Dio.

Install

After the RC is published:

flutter pub add alphax alphax_native

While this RC is unpublished, use the repository dependency block in the root README.

The Android provider is resolved through Gradle and Apple packaging uses CocoaPods. No copied Cronet binary is bundled in the pub package. Swift Package Manager integration is deferred for 1.0.

Choose a transport

This is the only platform-specific decision in your application setup. The rest of your request code can stay the same.

import 'dart:io';

import 'package:alphax/alphax.dart';
import 'package:alphax_native/alphax_native.dart';

Future<AlphaXTransport> createTransport() async {
  if (Platform.isAndroid) {
    return AndroidCronetTransport.create();
  }
  if (Platform.isIOS || Platform.isMacOS) {
    return AppleUrlSessionTransport.create();
  }
  return DartIoTransport();
}

Future<void> main() async {
  final client = AlphaXClient(transport: await createTransport());
  try {
    final response = await client.get(Uri.https('example.com', '/'));
    print('${response.statusCode}: ${await response.readAsString()}');
  } finally {
    await client.close();
  }
}

Platform support

Platform	Adapter	Protocol boundary
Android API 24+	Cronet/HttpEngine provider	H1/H2/H3 where the selected non-fallback provider and network negotiate it
iOS 15+	URLSession	H1/H2/H3 where the OS, server, proxy, and network negotiate it
macOS 12+	URLSession	H1/H2/H3 where the OS, server, proxy, and network negotiate it
Linux	Dart IO	H1 only; H2/H3 are not advertised
Windows	Dart IO	H1 only; H2/H3 are not advertised
Web	Not provided by this native plugin	Add alphax_web for browser Fetch

Common jobs

Stream and cancel a response

final token = AlphaXCancellationToken();
final response = await client.get(
  Uri.https('example.com', '/large-response'),
  cancellationToken: token,
);

await for (final chunk in response.stream) {
  // Process bounded chunks as they arrive.
}

// Call token.cancel('screen closed') when the UI no longer needs the response.

Native adapters use bounded response delivery. Pausing or cancelling a Dart stream does not require the native layer to buffer the entire response.

Download directly to a platform file

final result = await client.download(
  Uri.https('example.com', '/archive.bin'),
  to: AlphaXLocalFileTarget('/tmp/archive.bin'),
  onDownloadProgress: (progress) {
    print('${progress.bytesTransferred} bytes received');
  },
);
print('actual protocol: ${result.protocol.name}');

AlphaXLocalFileSource and AlphaXLocalFileTarget keep platform file paths out of the core alphax package. The Dart IO fallback remains stream-based when native file paths are unavailable.

Inspect the actual protocol

final response = await client.get(
  Uri.https('example.com', '/health'),
  protocolPreference: AlphaXProtocolPreference.http3,
);
final metrics = await response.completionMetrics;
print('negotiated protocol: ${metrics.negotiatedProtocol.name}');

If H3 is mandatory, pass protocolRequirement: AlphaXProtocolRequirement.http3. A preference may fall back to H2 or H1; a requirement fails closed when H3 is not negotiated.

Configure TLS and proxy behavior

The transport constructors use secure, system-managed defaults:

• certificate-chain, hostname, and validity checks are enabled;
• the system proxy policy is used; and
• SPKI pinning, explicit proxy routing, and custom trust anchors are off until you configure them.

Configure these controls when the transport is created, before passing it to AlphaXClient:

final transport = await AppleUrlSessionTransport.create(
  tlsPolicy: AlphaXTlsPolicy(
    pins: <AlphaXSpkiPin>[
      AlphaXSpkiPin(
        host: apiHost,
        sha256SpkiBase64: primarySpkiSha256Base64,
        expiresAt: primaryPinExpiry,
      ),
      AlphaXSpkiPin(
        host: apiHost,
        sha256SpkiBase64: backupSpkiSha256Base64,
        expiresAt: backupPinExpiry,
      ),
    ],
  ),
  proxyPolicy: AlphaXProxyPolicy.http(
    host: proxyHost,
    port: proxyPort,
  ),
);
final client = AlphaXClient(transport: transport);

The pin variables must come from your secure release configuration. A pin is a base64 SHA-256 digest of the certificate's DER SubjectPublicKeyInfo. Keep a primary and backup pin, give both an expiry, and rotate before expiry. Pinning adds to normal certificate validation; it never makes an expired, untrusted, or wrong-host certificate valid.

Check client.capabilities before selecting an optional control. If the selected provider cannot honor a configured TLS or proxy policy, initialization fails with a normalized unsupported-policy error instead of silently changing the route or trust behavior.

Control	Dart IO	Android Cronet	Apple URLSession
Platform trust	Supported by default	Supported by default	Supported by default
SPKI pinning	Unsupported; fails closed	Supported by the selected provider	Supported
Custom trust anchors	Supported where Dart IO can load them	Unsupported by the selected provider	Supported through platform trust APIs
system() proxy	Supported	Provider/system managed	Supported
direct() proxy	Supported	Unsupported by the selected provider	Supported
Explicit http(...) proxy	Supported, including Basic auth	Unsupported by the selected provider	Supported, including HTTPS CONNECT where CFNetwork permits
Explicit https(...) proxy endpoint	Unsupported	Unsupported	Unsupported by the shared 1.0 mapping
mTLS/client identity	Unsupported in 1.0	Unsupported in the selected provider	Unsupported in 1.0

An HTTP proxy endpoint can carry an HTTPS destination through CONNECT; that is different from configuring an HTTPS proxy endpoint. Never use trust-all configuration, log proxy credentials, or put real pin material in examples. For retry, authentication, cookies, caching, resilience, protocol preference, and custom application policies, follow the policy defaults and customization guide.

What this package does not promise

• It does not guarantee H3 on every request or every network.
• It does not provide the browser transport; use the separate alphax_web package for Web.
• It does not expose Cronet, URLSession, Flutter channel, FFI, C++, Rust, or libcurl types through the core API.
• It does not make unsupported TLS or proxy policies silently succeed.
• It makes no universal performance, zero-copy, or “fastest client” claim.

Authentication, cookies, caching, retries, and generic resilience are opt-in pure-Dart middleware from alphax. This package only selects and implements native/Dart IO transports; it does not enable those policies automatically.

Continue learning

• Core AlphaX API
• Dio adapter
• Testing helpers
• Waypoint reference app
• Migration guide
• 1.0 platform and protocol matrix

The 1.0.0-rc.1 candidate is prepared for maintainer review and is not published until naming clearance and release approval are complete.