diff --git a/.github/workflows/test.yml b/.github/workflows/test.yml
new file mode 100644
index 0000000..16f93aa
--- /dev/null
+++ b/.github/workflows/test.yml
@@ -0,0 +1,49 @@
+name: Test
+
+on:
+  push:
+    branches:
+      - main
+  pull_request:
+    branches:
+      - "*"
+
+jobs:
+  test-xcode:
+    runs-on: macos-latest
+
+    steps:
+      - uses: actions/checkout@v6
+      - uses: maxim-lobanov/setup-xcode@v1
+        with:
+          xcode-version: latest-stable
+      - name: Build
+        run: swift build -v
+      - name: Build release
+        run: swift build -c release -v
+
+  test-linux:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v6
+      - name: Build
+        run: swift build -v
+      - name: Build release
+        run: swift build -c release -v
+
+  test-template:
+    runs-on: macos-latest
+    steps:
+      - uses: actions/checkout@v6
+      - uses: maxim-lobanov/setup-xcode@v1
+        with:
+          xcode-version: latest-stable
+      - name: Build saga
+        run: swift build -c release
+      - name: Scaffold a site and build it
+        run: |
+          mkdir -p "$RUNNER_TEMP/smoke"
+          cd "$RUNNER_TEMP/smoke"
+          "$GITHUB_WORKSPACE/.build/release/saga" init testsite
+          cd testsite
+          swift build
diff --git a/.swiftformat b/.swiftformat
index bc573ed..d12dc83 100644
--- a/.swiftformat
+++ b/.swiftformat
@@ -2,4 +2,5 @@
 --indentcase true
 --patternlet inline
 --disable unusedArguments
---disable redundantReturn
\ No newline at end of file
+--disable redundantReturn
+--exclude .build,IntegrationTests/Fixture/Sources/Fixture/Generated.swift
\ No newline at end of file
diff --git a/IntegrationTests/Fixture/Package.swift b/IntegrationTests/Fixture/Package.swift
index 60d600c..a3184fb 100644
--- a/IntegrationTests/Fixture/Package.swift
+++ b/IntegrationTests/Fixture/Package.swift
@@ -1,8 +1,8 @@
 // swift-tools-version:6.0
 import PackageDescription
 
-// Stands in for a Saga site so the shutdown tests don't need the real Saga
-// dependency graph. Built and driven by ../run-shutdown-tests.sh.
+/// Stands in for a Saga site so the shutdown tests don't need the real Saga
+/// dependency graph. Built and driven by ../run-shutdown-tests.sh.
 let package = Package(
   name: "fixture",
   products: [.executable(name: "Fixture", targets: ["Fixture"])],
diff --git a/Sources/SagaCLI/DevCommand.swift b/Sources/SagaCLI/DevCommand.swift
index ed8dde2..8b94697 100644
--- a/Sources/SagaCLI/DevCommand.swift
+++ b/Sources/SagaCLI/DevCommand.swift
@@ -1,7 +1,6 @@
 import ArgumentParser
 import Foundation
 import SagaPathKit
-import os
 
 struct Dev: ParsableCommand {
   static let configuration = CommandConfiguration(
@@ -40,7 +39,7 @@ private final class DevCoordinator: @unchecked Sendable {
     var shuttingDown = false
   }
 
-  private let lifecycle = OSAllocatedUnfairLock(initialState: Lifecycle())
+  private let lifecycle = Locked(initialState: Lifecycle())
 
   /// Serializes recompiles. Shutdown never uses this, so Ctrl-C doesn't wait on
   /// an in-flight build.
@@ -60,7 +59,7 @@ private final class DevCoordinator: @unchecked Sendable {
     sigintSrc.setEventHandler { [weak self] in
       print("\nShutting down...")
       guard let self else { Foundation.exit(0) }
-      self.shutdown()
+      shutdown()
     }
     sigintSrc.resume()
 
@@ -97,7 +96,7 @@ private final class DevCoordinator: @unchecked Sendable {
       return (process, false)
     }
     if alreadyShuttingDown {
-      dispatchMain()   // shutdown() is mid-flight and exits the process
+      dispatchMain() // shutdown() is mid-flight and exits the process
     }
     guard let siteProcess else {
       log("Failed to launch site process.")
diff --git a/Sources/SagaCLI/DevServer.swift b/Sources/SagaCLI/DevServer.swift
index 797e1df..f9a48ed 100644
--- a/Sources/SagaCLI/DevServer.swift
+++ b/Sources/SagaCLI/DevServer.swift
@@ -17,8 +17,8 @@ final class DevServer: @unchecked Sendable {
   }
 
   func start() throws {
-    let outputPath = self.outputPath
-    let sseConnections = self.sseConnections
+    let outputPath = outputPath
+    let sseConnections = sseConnections
     let baseDir = FileManager.default.currentDirectoryPath
 
     let bootstrap = ServerBootstrap(group: group)
@@ -111,7 +111,7 @@ private final class HTTPHandler: ChannelInboundHandler, @unchecked Sendable {
     // Static file serving
     let filePath = resolveFilePath(uri: uri)
 
-    guard let filePath = filePath,
+    guard let filePath,
           FileManager.default.fileExists(atPath: filePath),
           let data = FileManager.default.contents(atPath: filePath)
     else {
@@ -122,11 +122,10 @@ private final class HTTPHandler: ChannelInboundHandler, @unchecked Sendable {
     let contentType = mimeType(for: filePath)
     let isHTML = contentType == "text/html"
 
-    var responseData: Data
-    if isHTML, let html = String(data: data, encoding: .utf8) {
-      responseData = Data(injectReloadScript(into: html).utf8)
+    var responseData: Data = if isHTML, let html = String(data: data, encoding: .utf8) {
+      Data(injectReloadScript(into: html).utf8)
     } else {
-      responseData = data
+      data
     }
 
     var headers = HTTPHeaders()
@@ -166,9 +165,8 @@ private final class HTTPHandler: ChannelInboundHandler, @unchecked Sendable {
 
     // Direct file match
     let directPath = outputPath + path
-    if fileManager.fileExists(atPath: directPath) {
-      var isDir: ObjCBool = false
-      fileManager.fileExists(atPath: directPath, isDirectory: &isDir)
+    var isDir: ObjCBool = false
+    if fileManager.fileExists(atPath: directPath, isDirectory: &isDir) {
       if !isDir.boolValue {
         return directPath
       }
@@ -220,11 +218,10 @@ private final class HTTPHandler: ChannelInboundHandler, @unchecked Sendable {
   }
 
   private func mimeType(for path: String) -> String {
-    let ext: String
-    if let dotIndex = path.lastIndex(of: ".") {
-      ext = String(path[path.index(after: dotIndex)...]).lowercased()
+    let ext = if let dotIndex = path.lastIndex(of: ".") {
+      String(path[path.index(after: dotIndex)...]).lowercased()
     } else {
-      ext = ""
+      ""
     }
     switch ext {
       case "html", "htm": return "text/html"
diff --git a/Sources/SagaCLI/Utils.swift b/Sources/SagaCLI/Utils.swift
index 88379e3..0ff1243 100644
--- a/Sources/SagaCLI/Utils.swift
+++ b/Sources/SagaCLI/Utils.swift
@@ -145,3 +145,20 @@ func openBrowser(url: String) {
     try? process.run()
   #endif
 }
+
+/// State that can only be reached while its lock is held. Used instead of
+/// `OSAllocatedUnfairLock`, which doesn't exist on Linux.
+final class Locked<State>: @unchecked Sendable {
+  private var state: State
+  private let lock = NSLock()
+
+  init(initialState: State) {
+    state = initialState
+  }
+
+  func withLock<R>(_ body: (inout State) throws -> R) rethrows -> R {
+    lock.lock()
+    defer { lock.unlock() }
+    return try body(&state)
+  }
+}
diff --git a/justfile b/justfile
index e376b56..b6f2325 100644
--- a/justfile
+++ b/justfile
@@ -1,8 +1,8 @@
 build:
   swift build
 
-build-swift510:
-  docker run --rm -v "$PWD":/src -w /src --tmpfs /src/.build:exec swift:5.10 swift build
+build-linux:
+  docker run --rm -v "$PWD":/src -w /src --tmpfs /src/.build:exec swift:6.2 swift build
 
 format:
-  swiftformat -swift-version 5 .
+  swiftformat -swift-version 6 .