# Upstream/API research snapshot

Checked 2026-09-22.

## Flet

Current Flet publishing docs describe a generated Flutter shell and support
`[tool.flet.app] path/module`, local developer packages and Flutter user extensions.
The bridge uses a Flet `Service` control and a Dart `FletService`, then a standard
Flutter `MethodChannel` for the Android plugin. It is intentionally not a Python
subprocess bridge.

## Android

Current Android docs require `VpnService.prepare()`, `protect()` for upstream sockets,
`Builder.establish()`, and a foreground service on API 26+. Android 14+ foreground
services require a declared type; this project uses the documented `specialUse` type and
an explanatory property. Android has one active VPN service per user/profile.

`Builder.addDisallowedApplication()` is valid for `DIRECT`, but it makes traffic bypass
the VPN and therefore cannot implement `VOID`. `VOID` needs a UID-aware native packet
path and a fail-closed drop policy; the Python model exists now, while enforcement is a
device-tested native milestone.

`LocalOnlyHotspot` is the public API for an app-created local network. Android 13+
requires `NEARBY_WIFI_DEVICES`; older targets use location permission. The reservation
returns SSID/password but the interface address must be discovered at runtime. The
implementation does not assume a fixed `192.168.43.1` address and does not enable
system tethering.

## FreeTurn

The current `samosvalishe/free-turn-proxy` mobile README documents the gomobile API:
`Start`, `StartTunnel`, `StartDirectTunnel`, `Restart`, `Stop`, `GetState`,
`TunnelStats`, `ParseTunnelConfig`, `SetProtect`, `SetEventSink`, `ValidateConfig` and
`OnCaptcha`. The Android AAR is built with the upstream `task build:android` target.
The Android reference app is GPL-3.0 and is used only as lifecycle/API evidence.

## SignBox / sing-box

The exact public name `signbox` and a public artifact matching the user's VLESS +
AmneziaWG 3.1 claim were not found. Upstream sing-box exposes `libbox.aar` through
gomobile, but its package/API and build tags must be checked against the actual SignBox
artifact before compiling calls. The repo therefore has a real adapter boundary and a
hard `UNSUPPORTED` result rather than a fabricated success.

## Removed scope

iOS and NetworkExtension are not implemented. macOS is omitted from the first build;
desktop target is Linux/Windows proxy-only.