diff --git a/Package.swift b/Package.swift
index 2354a088271..2728c51e315 100644
--- a/Package.swift
+++ b/Package.swift
@@ -3,36 +3,62 @@
 import Foundation
 import PackageDescription
 
+// MARK: - Parse build arguments
+
+func hasEnvironmentVariable(_ name: String) -> Bool {
+  return ProcessInfo.processInfo.environment[name] != nil
+}
+
+/// Set when building swift-syntax using swift-syntax-dev-utils or in Swift CI in general.
+///
+/// Modifies the build in the following ways
+///  - Enables assertions even in release builds
+///  - Removes the dependency of swift-syntax on os_log
+let buildScriptEnvironment = hasEnvironmentVariable("SWIFT_BUILD_SCRIPT_ENVIRONMENT")
+
+/// Check that the layout of the syntax tree is correct.
+///
+/// See CONTRIBUTING.md for more information
+let rawSyntaxValidation = hasEnvironmentVariable("SWIFTSYNTAX_ENABLE_RAWSYNTAX_VALIDATION")
+
+/// Mutate the input of `assertParse` test cases.
+///
+/// See CONTRIBUTING.md for more information
+let alternateTokenIntrospection = hasEnvironmentVariable("SWIFTPARSER_ENABLE_ALTERNATE_TOKEN_INTROSPECTION")
+
+/// Assume that swift-argument-parser is checked out next to swift-syntax and use that instead of fetching a remote dependency.
+let useLocalDependencies = hasEnvironmentVariable("SWIFTCI_USE_LOCAL_DEPS")
+
+// MARK: - Compute custom build settings
+
+// These build settings apply to the target and the corresponding test target.
 var swiftSyntaxSwiftSettings: [SwiftSetting] = []
 var swiftSyntaxBuilderSwiftSettings: [SwiftSetting] = []
 var swiftParserSwiftSettings: [SwiftSetting] = []
 
-/// If we are in a controlled CI environment, we can use internal compiler flags
-/// to speed up the build or improve it.
-if ProcessInfo.processInfo.environment["SWIFT_BUILD_SCRIPT_ENVIRONMENT"] != nil {
+if buildScriptEnvironment {
   swiftSyntaxSwiftSettings += [
     .define("SWIFTSYNTAX_ENABLE_ASSERTIONS")
   ]
   swiftSyntaxBuilderSwiftSettings += [
     .define("SWIFTSYNTAX_NO_OSLOG_DEPENDENCY")
   ]
-  swiftParserSwiftSettings += [
-    .define("SWIFTSYNTAX_NO_OSLOG_DEPENDENCY")
-  ]
 }
 
-if ProcessInfo.processInfo.environment["SWIFTSYNTAX_ENABLE_RAWSYNTAX_VALIDATION"] != nil {
+if rawSyntaxValidation {
   swiftSyntaxSwiftSettings += [
     .define("SWIFTSYNTAX_ENABLE_RAWSYNTAX_VALIDATION")
   ]
 }
 
-if ProcessInfo.processInfo.environment["SWIFTPARSER_ENABLE_ALTERNATE_TOKEN_INTROSPECTION"] != nil {
+if alternateTokenIntrospection {
   swiftParserSwiftSettings += [
     .define("SWIFTPARSER_ENABLE_ALTERNATE_TOKEN_INTROSPECTION")
   ]
 }
 
+// MARK: - Build the package
+
 let package = Package(
   name: "swift-syntax",
   platforms: [
@@ -153,10 +179,11 @@ let package = Package(
 
     .testTarget(
       name: "SwiftSyntaxTest",
-      dependencies: ["_SwiftSyntaxTestSupport", "SwiftSyntax", "SwiftSyntaxBuilder"]
+      dependencies: ["_SwiftSyntaxTestSupport", "SwiftSyntax", "SwiftSyntaxBuilder"],
+      swiftSettings: swiftSyntaxSwiftSettings
     ),
 
-    // MARK: Verison marker modules
+    // MARK: Version marker modules
 
     .target(
       name: "SwiftSyntax509",
@@ -174,7 +201,8 @@ let package = Package(
 
     .testTarget(
       name: "SwiftSyntaxBuilderTest",
-      dependencies: ["_SwiftSyntaxTestSupport", "SwiftSyntaxBuilder"]
+      dependencies: ["_SwiftSyntaxTestSupport", "SwiftSyntaxBuilder"],
+      swiftSettings: swiftSyntaxBuilderSwiftSettings
     ),
 
     // MARK: SwiftSyntaxMacros
@@ -303,7 +331,7 @@ package.targets.append(
   )
 )
 
-if ProcessInfo.processInfo.environment["SWIFTCI_USE_LOCAL_DEPS"] == nil {
+if useLocalDependencies {
   // Building standalone.
   package.dependencies += [
     .package(url: "https://github.com/apple/swift-argument-parser.git", from: "1.2.2")
diff --git a/SwiftSyntaxDevUtils/Sources/swift-syntax-dev-utils/commands/Test.swift b/SwiftSyntaxDevUtils/Sources/swift-syntax-dev-utils/commands/Test.swift
index 6a5c3270cf0..2e1394b42a8 100644
--- a/SwiftSyntaxDevUtils/Sources/swift-syntax-dev-utils/commands/Test.swift
+++ b/SwiftSyntaxDevUtils/Sources/swift-syntax-dev-utils/commands/Test.swift
@@ -32,18 +32,11 @@ struct Test: ParsableCommand, BuildCommand {
 
   private func runTests() throws {
     logSection("Running SwiftSyntax Tests")
-    var swiftpmCallArguments = [
-      "--test-product", "swift-syntaxPackageTests",
-    ]
-
-    if arguments.verbose {
-      swiftpmCallArguments += ["--verbose"]
-    }
 
     try invokeSwiftPM(
       action: "test",
       packageDir: Paths.packageDir,
-      additionalArguments: swiftpmCallArguments,
+      additionalArguments: ["--test-product", "swift-syntaxPackageTests"],
       additionalEnvironment: swiftPMEnvironmentVariables,
       captureStdout: false,
       captureStderr: false
@@ -52,18 +45,10 @@ struct Test: ParsableCommand, BuildCommand {
 
   private func runCodeGenerationTests() throws {
     logSection("Running CodeGeneration Tests")
-    var swiftpmCallArguments = [
-      "--test-product", "CodeGenerationPackageTests",
-    ]
-
-    if arguments.verbose {
-      swiftpmCallArguments += ["--verbose"]
-    }
-
     try invokeSwiftPM(
       action: "test",
       packageDir: Paths.codeGenerationDir,
-      additionalArguments: swiftpmCallArguments,
+      additionalArguments: ["--test-product", "CodeGenerationPackageTests"],
       additionalEnvironment: swiftPMEnvironmentVariables,
       captureStdout: false,
       captureStderr: false
diff --git a/SwiftSyntaxDevUtils/Sources/swift-syntax-dev-utils/common/BuildArguments.swift b/SwiftSyntaxDevUtils/Sources/swift-syntax-dev-utils/common/BuildArguments.swift
index 9d2439a47a9..6dbe6eb9c76 100644
--- a/SwiftSyntaxDevUtils/Sources/swift-syntax-dev-utils/common/BuildArguments.swift
+++ b/SwiftSyntaxDevUtils/Sources/swift-syntax-dev-utils/common/BuildArguments.swift
@@ -39,9 +39,6 @@ struct BuildArguments: ParsableArguments {
   )
   var multirootDataFile: URL?
 
-  @Flag(help: "Disable sandboxes when building with SwiftPM")
-  var disableSandbox: Bool = false
-
   @Flag(help: "Build in release mode.")
   var release: Bool = false
 
diff --git a/SwiftSyntaxDevUtils/Sources/swift-syntax-dev-utils/common/BuildCommand.swift b/SwiftSyntaxDevUtils/Sources/swift-syntax-dev-utils/common/BuildCommand.swift
index 6895ccec838..6a1d4f383f9 100644
--- a/SwiftSyntaxDevUtils/Sources/swift-syntax-dev-utils/common/BuildCommand.swift
+++ b/SwiftSyntaxDevUtils/Sources/swift-syntax-dev-utils/common/BuildCommand.swift
@@ -62,10 +62,6 @@ extension BuildCommand {
       args += ["--multiroot-data-file", multirootDataFile]
     }
 
-    if arguments.disableSandbox {
-      args += ["--disable-sandbox"]
-    }
-
     if arguments.verbose {
       args += ["--verbose"]
     }