Add SwiftPM and initial linux support for swift

.devcontainer/swift/Dockerfile

@@ -0,0 +1,22 @@
+FROM swift:6.3
+
+ARG GO_VERSION=1.25.5
+ARG TARGETARCH
+
+RUN apt-get update \
+    && apt-get install -y --no-install-recommends \
+        curl \
+        ca-certificates \
+        build-essential \
+        libcurl4-openssl-dev \
+    && rm -rf /var/lib/apt/lists/*
+
+RUN curl -fsSL "https://go.dev/dl/go${GO_VERSION}.linux-${TARGETARCH:-amd64}.tar.gz" -o /tmp/go.tar.gz \
+    && tar -C /usr/local -xzf /tmp/go.tar.gz \
+    && rm /tmp/go.tar.gz
+
+ENV PATH="/usr/local/go/bin:${PATH}"
+ENV GOPATH="/go"
+ENV PATH="${GOPATH}/bin:${PATH}"
+
+RUN go version && swift --version

.devcontainer/swift/devcontainer.json

@@ -0,0 +1,23 @@
+{
+    "name": "swift",
+    "build": {
+        "dockerfile": "Dockerfile",
+        "context": "../.."
+    },
+    "workspaceFolder": "/workspace",
+    "workspaceMount": "source=${localWorkspaceFolder},target=/workspace,type=bind",
+    "customizations": {
+        "vscode": {
+            "extensions": [
+                "swiftlang.swift-vscode",
+                "golang.go"
+            ],
+            "settings": {
+                "[swift]": {
+                    "editor.formatOnSave": false
+                }
+            }
+        }
+    },
+    "postCreateCommand": "go version && swift --version"
+}

.github/workflows/swift.yml

@@ -3,7 +3,7 @@ name: swift
 on: [push]
 
 jobs:
-  build:
+  build-macos:
 
     runs-on: macos-15
     steps:
@@ -17,8 +17,28 @@ jobs:
       - name: Test
         run: cd swift && make test
 
-      - name: iOS 
+      - name: iOS
         run: cd swift && make ios-fat
 
       - name: macos 
         run: cd swift && make macos 
+
+  build-linux:
+
+    runs-on: ubuntu-latest
+    container: swift:6.3
+    steps:
+      - uses: actions/checkout@v3
+
+      - name: Set up Go
+        uses: actions/setup-go@v6
+        with:
+          go-version: "1.25.5"
+
+      - name: Install cross toolchains
+        run: |
+          apt-get update
+          apt-get install -y --no-install-recommends build-essential gcc-x86-64-linux-gnu gcc-aarch64-linux-gnu libc6-dev-amd64-cross libc6-dev-arm64-cross
+
+      - name: Test
+        run: cd swift && make test-spm

.gitignore

@@ -24,3 +24,5 @@ libtailscale.bundle
 /sourcepkg/libtailscale.tar*
 
 /vendor/
+
+.build/

swift/Examples/TailscaleKitCLI/Makefile

@@ -0,0 +1,14 @@
+# Copyright (c) Tailscale Inc & AUTHORS
+# SPDX-License-Identifier: BSD-3-Clause
+
+.PHONY: spm-setup
+spm-setup: ## Build the TailscaleKit artifact bundle this example depends on (Linux and macOS; see swift/README.md)
+	@$(MAKE) -C ../.. spm-setup
+
+.PHONY: help
+help: ## Show this help
+	@echo "\nSpecify a command. The choices are:\n"
+	@grep -hE '^[0-9a-zA-Z_-]+:.*?## .*$$' ${MAKEFILE_LIST} | awk 'BEGIN {FS = ":.*?## "}; {printf "  \033[0;36m%-12s\033[m %s\n", $$1, $$2}'
+	@echo ""
+
+.DEFAULT_GOAL := help

swift/Examples/TailscaleKitCLI/Package.swift

@@ -0,0 +1,19 @@
+// swift-tools-version:6.3
+import PackageDescription
+
+let package = Package(
+    name: "TailscaleKitCLI",
+    dependencies: [
+        .package(name: "TailscaleKit", path: "../.."),
+        .package(url: "https://github.com/apple/swift-argument-parser", from: "1.8.0"),
+    ],
+    targets: [
+        .executableTarget(
+            name: "tsdemo",
+            dependencies: [
+                .product(name: "TailscaleKit", package: "TailscaleKit"),
+                .product(name: "ArgumentParser", package: "swift-argument-parser"),
+            ]
+        )
+    ]
+)

swift/Examples/TailscaleKitCLI/README.md

@@ -0,0 +1,71 @@
+# TailscaleKitCLI
+
+A minimal SwiftPM executable, built with [swift-argument-parser](https://github.com/apple/swift-argument-parser), that joins your tailnet and lists its devices using TailscaleKit. Needs no Xcode project — it exists purely as a proof that TailscaleKit works from plain SwiftPM, including on Linux.
+
+Unlike `TailscaleKitHello` (an Xcode app that links a prebuilt `.xcframework`), this package depends directly on `swift/Package.swift`, exercising the same SwiftPM path covered by `swift test`/`make test-spm`.
+
+## Setup
+
+From this directory, build the artifact bundle this package needs. Run this once:
+
+```sh
+$ make spm-setup
+```
+
+Generate and export an auth key at https://login.tailscale.com/admin/settings/keys.
+
+```sh
+$ export TS_AUTHKEY=tskey-auth-...
+```
+
+## Usage
+
+```sh
+$ swift run tsdemo
+```
+
+Example output:
+
+```
+make spm-setup
+make[1]: Entering directory '/workspace/swift'
+
+::: Building SwiftPM artifact bundle for TailscaleKit :::
+./script/build-artifactbundle.sh
+::: Building libtailscale.a for x86_64-unknown-linux-gnu (GOOS=linux GOARCH=amd64, CC=x86_64-linux-gnu-gcc) :::
+::: Building libtailscale.a for aarch64-unknown-linux-gnu (GOOS=linux GOARCH=arm64, CC=aarch64-linux-gnu-gcc) :::
+::: Skipping macOS variants (not running on a Darwin host) :::
+wrote /workspace/swift/build/TailscaleKit.artifactbundle
+make[1]: Leaving directory '/workspace/swift'
+root@82cf0493d6f1:/workspace/swift/Examples/TailscaleKitCLI# export TS_AUTHKEY=tskey-auth-...
+root@82cf0493d6f1:/workspace/swift/Examples/TailscaleKitCLI# swift run tsdemo
+[1/1] Planning build
+Building for debugging...
+clang: warning: argument unused during compilation: '-F/workspace/swift/Examples/TailscaleKitCLI/.build/aarch64-unknown-linux-gnu/debug' [-Wunused-command-line-argument]
+[40/40] Linking tsdemo
+Build of product 'tsdemo' complete! (2.97s)
+2026/07/11 21:14:20 tsnet running state path /tmp/tsdemo-FF27454D/tailscaled.state
+2026/07/11 21:14:20 tsnet starting with hostname "tsdemo-FF27454D", varRoot "/tmp/tsdemo-FF27454D"
+2026/07/11 21:14:20 LocalBackend state is NeedsLogin; running StartLoginInteractive...
+Bringing up "tsdemo-FF27454D", waiting to associate with the tailnet...
+2026/07/11 21:14:22 localapi tcp serve error: use of closed network connection
+2026/07/11 21:14:22 socks5: SOCKS5 server exited: use of closed network connection
+Backend state: Running
+Devices on this tailnet:
+  [offline] xxx  100.xx.xx.xx  xxx.my-tailnet-name.ts.net.
+  [online ] xxx  100.xx.xx.xx  xxx.my-tailnet-name.ts.net.
+  [online ] xxx  100.xx.xx.xx  xxx.my-tailnet-name.ts.net.
+  [offline] xxx  100.xx.xx.xx  xxx.my-tailnet-name.ts.net.
+  [online ] xxx  100.xx.xx.xx  xxx.my-tailnet-name.ts.net.
+  [online ] xxx  100.xx.xx.xx  xxx.my-tailnet-name.ts.net.
+  [offline] xxx  100.xx.xx.xx  xxx.my-tailnet-name.ts.net.
+```
+
+Brings up a throwaway, ephemeral in-process tsnet node, then prints the tailnet's backend state and every other device currently visible on it. Needs a real Tailscale auth key and network access.
+
+## What this is showing off
+
+- `TailscaleNode` — bringing up an in-process node against the control plane.
+- `LocalAPIClient` — querying the node's own local API for backend/peer status, the same API `tailscale status` itself uses.
+
+For the raw send/receive primitives (`Listener`/`IncomingConnection`/`OutgoingConnection`), see `swift/TailscaleKitXCTests/TailscaleKitTests.swift`.

swift/Examples/TailscaleKitCLI/Sources/tsdemo/TSDemo.swift

@@ -0,0 +1,80 @@
+// Copyright (c) Tailscale Inc & AUTHORS
+// SPDX-License-Identifier: BSD-3-Clause
+
+import ArgumentParser
+import TailscaleKit
+
+#if canImport(FoundationEssentials)
+import FoundationEssentials
+#else
+import Foundation
+#endif
+
+/// A minimal proof that TailscaleKit works via plain SwiftPM (including on Linux)
+@main
+struct TSDemo: AsyncParsableCommand {
+    static let configuration = CommandConfiguration(
+        commandName: "tsdemo",
+        abstract: "Joins a tailnet and lists its devices, using TailscaleKit via SwiftPM.",
+        discussion: """
+            Needs a Tailscale auth key. Generate a reusable one at
+            https://login.tailscale.com/admin/settings/keys and pass it via --auth-key or the
+            TS_AUTHKEY environment variable.
+            """
+    )
+
+    @Option(help: "Tailscale auth key. Defaults to the TS_AUTHKEY environment variable.")
+    var authKey: String?
+
+    @Option(help: "Control plane URL.")
+    var controlURL: String = kDefaultControlURL
+
+    @Flag(help: "Log tsnet's internal activity to stderr instead of discarding it.")
+    var verbose: Bool = false
+
+    func run() async throws {
+        guard let authKey = authKey ?? ProcessInfo.processInfo.environment["TS_AUTHKEY"] else {
+            throw ValidationError(
+                "Provide --auth-key or set TS_AUTHKEY. Generate one at https://login.tailscale.com/admin/settings/keys"
+            )
+        }
+
+        let hostname = "tsdemo-\(UUID().uuidString.prefix(8))"
+        let dir = FileManager.default.temporaryDirectory.appendingPathComponent(hostname).path
+        let config = Configuration(
+            hostName: hostname, 
+            path: dir, 
+            authKey: authKey, 
+            controlURL: controlURL, 
+            ephemeral: true
+        )
+        let logger: LogSink = verbose ? DefaultLogger() : BlackholeLogger()
+        let node = try TailscaleNode(config: config, logger: logger)
+
+        print("Bringing up \"\(hostname)\", waiting to associate with the tailnet...")
+        try await node.up()
+
+        do {
+            let api = LocalAPIClient(localNode: node, logger: logger)
+            let status = try await api.backendStatus()
+
+            print("Backend state: \(status.BackendState)")
+
+            let peers = (status.Peer?.values).map(Array.init)?.sorted { $0.HostName < $1.HostName } ?? []
+            if peers.isEmpty {
+                print("No other devices visible on this tailnet yet.")
+            } else {
+                print("Devices on this tailnet:")
+                for peer in peers {
+                    let ip = peer.TailscaleIPs?.first ?? "?"
+                    let mark = peer.Online ? "online " : "offline"
+                    print("  [\(mark)] \(peer.HostName)  \(ip)  \(peer.DNSName)")
+                }
+            }
+            try await node.close()
+        } catch {
+            try? await node.close()
+            throw error
+        }
+    }
+}

swift/Examples/TailscaleKitHello/HelloFromTailscale/HelloViewModel.swift

@@ -1,13 +1,11 @@
 // Copyright (c) Tailscale Inc & AUTHORS
 // SPDX-License-Identifier: BSD-3-Clause
 
-
 import SwiftUI
-@preconcurrency import Combine
 import TailscaleKit
 
 @Observable
-class HelloViewModel: @unchecked Sendable    {
+class HelloViewModel: @unchecked Sendable {
     var message: String = "Ready to phone home!"
     var peerCountMessage = "Waiting for peers...."
     var stateMessage = "Waiting for state...."
@@ -75,7 +73,7 @@ class HelloViewModel: @unchecked Sendable    {
 
     @MainActor
     func setMessage(_ message: String) {
-        self.message =  message
+        self.message = message
     }
 
     func runRequest(_ dialer: Dialer) {

swift/Makefile

@@ -61,9 +61,11 @@ ios-fat: ios-sim ios ## Builds TailscaleKit.xcframework to swift/build/Build/Pro
 
 .PHONY: test
 test: ## Run tests (macOS)
-	@echo 
+	@echo
 	@echo "::: Running tests for TailscaleKit :::"
+	rm -f ../tstestcontrol/libtstestcontrol.a
 	cd ../tstestcontrol && make all
+	rm -f ../libtailscale.a ../libtailscale.h
 	cd .. && make c-archive
 	mkdir -p build
 	xcodebuild build-for-testing -scheme TailscaleKitXCTests \
@@ -78,6 +80,26 @@ test: ## Run tests (macOS)
 	 -destination 'platform=macOS,arch=arm64' \
 	 CODE_SIGNING_ALLOWED=NO
 
+.PHONY: spm-setup
+spm-setup: ## Build the artifact bundle needed for swift build/swift run. Run once, then swift build/run as many times as you like (cross-platform, incl. Linux)
+	@echo
+	@echo "::: Building SwiftPM artifact bundle for TailscaleKit :::"
+	./script/build-artifactbundle.sh
+
+.PHONY: spm-test-setup
+spm-test-setup: spm-setup ## Additionally build libtstestcontrol.a needed for swift test. Run once, then swift test as many times as you like
+	@echo
+	@echo "::: Building libtstestcontrol.a for TailscaleKit tests :::"
+	rm -f ../tstestcontrol/libtstestcontrol.a
+	cd ../tstestcontrol && make all
+	./script/fix-tstestcontrol-archive.sh
+
+.PHONY: test-spm
+test-spm: spm-test-setup ## Run tests via Swift Package Manager (cross-platform, incl. Linux)
+	@echo
+	@echo "::: Running tests for TailscaleKit via swift test :::"
+	swift test
+
 .PHONY: clean
 clean: ## Clean up build artifacts (including the libtailscale dependencies)
 	cd .. && make clean

swift/Package.swift

@@ -0,0 +1,37 @@
+// swift-tools-version:6.3
+import PackageDescription
+
+let swiftSettings: [SwiftSetting] = [
+    /// https://github.com/apple/swift-evolution/blob/main/proposals/0335-existential-any.md
+    /// Require `any` for existential types.
+    .enableUpcomingFeature("ExistentialAny")
+]
+
+let package = Package(
+    name: "TailscaleKit",
+    platforms: [.macOS(.v15), .iOS(.v18)],  // same as xcodeproj
+    products: [
+        .library(name: "TailscaleKit", targets: ["TailscaleKit"])
+    ],
+    targets: [
+        // No Go toolchain needed to consume it.
+        .binaryTarget(name: "CTailscale", path: "build/TailscaleKit.artifactbundle"),
+        .systemLibrary(name: "CTstestControl", path: "Sources/CTstestControl"),
+        .target(
+            name: "TailscaleKit",
+            dependencies: ["CTailscale"],
+            path: "TailscaleKit",
+            exclude: ["TailscaleKit.h"],
+            swiftSettings: swiftSettings
+        ),
+        .testTarget(
+            name: "TailscaleKitTests",
+            dependencies: ["TailscaleKit", "CTstestControl"],
+            path: "TailscaleKitXCTests",
+            swiftSettings: swiftSettings,
+            // Links against build/libtstestcontrol.a, a copy with its cgo runtime
+            // symbols renamed to avoid colliding with libtailscale.a's copy.
+            linkerSettings: [.unsafeFlags(["-L", "build"])]
+        ),
+    ]
+)