SwiftReckless¶

A Swift Package Manager wrapper around the Reckless chess engine, a UCI engine written in Rust and licensed under AGPL-3.0.

The engine runs in-process via a Rust-to-C FFI bridge; each UCI output line is delivered to the Swift layer as an element of an AsyncStream<String>. The Swift API mirrors StockfishEngine in SwiftStockfish so the existing UCIInfoParser / EngineProbe layer in Fianchetto can be adapted to either engine with minimal changes.

AGPL-3.0

SwiftReckless is distributed under the GNU Affero General Public License, version 3, because it links the Reckless engine's compiled code. See AGPL-3.0 licensing for what that means for your application.

Components¶

Type	Role
`RecklessEngine`	A live engine you talk to in UCI — `send(_:)` commands, read the `output` `AsyncStream`.
`RecklessNetworkLoader`	Downloads and verifies (SHA-256) the required NNUE network at runtime.

Requirements¶

Provision the NNUE net before creating the engine

RecklessEngine.init(networkDirectory:) returns nil if the NNUE net (v54-5478683c.nnue) is not present in networkDirectory. Always await RecklessNetworkLoader().ensure(in:) first.

One engine per process

The Rust engine owns process-global state (lookup tables, NNUE weights). Only one RecklessEngine may be alive in a process at a time. Sequential lifetimes are supported: fully shut down the current engine before creating another one. An overlapping RecklessEngine(networkDirectory:) returns nil.

Quick start¶

import Foundation
import SwiftReckless

// 1. Ensure the NNUE net exists in a writable directory.
let support = FileManager.default.urls(for: .applicationSupportDirectory, in: .userDomainMask)[0]
let dir = support.appendingPathComponent("reckless-nets")
// Progress fires once at completion (not incrementally).
try await RecklessNetworkLoader().ensure(in: dir) { p in
    if let f = p.fractionCompleted { print("net: \(Int(f * 100))%") }
}

// 2. Create the engine.
guard let engine = RecklessEngine(networkDirectory: dir) else {
    fatalError("engine failed to start — net missing or unreadable")
}

// 3. Read UCI output, send commands.
Task {
    for await line in engine.output {
        if line == "uciok"   { engine.isReady() }
        if line == "readyok" { engine.send("go depth 20") }
        if line.hasPrefix("bestmove ") {
            print("best:", line.split(separator: " ").dropFirst().first ?? "?")
            engine.shutdown()
            break
        }
    }
}
engine.uci()
engine.send("position startpos")

Licensing¶

SwiftReckless is distributed under the GNU Affero General Public License, version 3 (AGPL-3.0). Because it links the Reckless engine's compiled code directly into its output, the whole package is an AGPL-3.0 artifact. See AGPL-3.0 licensing for the full implications.