diff --git a/Sources/SWBCore/Settings/BuiltinMacros.swift b/Sources/SWBCore/Settings/BuiltinMacros.swift
index 25021fef..7e01b15a 100644
--- a/Sources/SWBCore/Settings/BuiltinMacros.swift
+++ b/Sources/SWBCore/Settings/BuiltinMacros.swift
@@ -1046,6 +1046,7 @@ public final class BuiltinMacros {
     public static let SWIFT_INDEX_STORE_PATH = BuiltinMacros.declarePathMacro("SWIFT_INDEX_STORE_PATH")
     public static let SWIFT_INSTALL_OBJC_HEADER = BuiltinMacros.declareBooleanMacro("SWIFT_INSTALL_OBJC_HEADER")
     public static let SWIFT_INSTALLAPI_LAZY_TYPECHECK = BuiltinMacros.declareBooleanMacro("SWIFT_INSTALLAPI_LAZY_TYPECHECK")
+    public static let SWIFT_DISABLE_PARSE_AS_LIBRARY = BuiltinMacros.declareBooleanMacro("SWIFT_DISABLE_PARSE_AS_LIBRARY")
     public static let SWIFT_LIBRARIES_ONLY = BuiltinMacros.declareBooleanMacro("SWIFT_LIBRARIES_ONLY")
     public static let SWIFT_LIBRARY_LEVEL = BuiltinMacros.declareStringMacro("SWIFT_LIBRARY_LEVEL")
     public static let SWIFT_LIBRARY_PATH = BuiltinMacros.declarePathMacro("SWIFT_LIBRARY_PATH")
@@ -2222,6 +2223,7 @@ public final class BuiltinMacros {
         _SWIFT_EXPLICIT_MODULES_ALLOW_CXX_INTEROP,
         _SWIFT_EXPLICIT_MODULES_ALLOW_BEFORE_SWIFT_5,
         _EXPERIMENTAL_SWIFT_EXPLICIT_MODULES,
+        SWIFT_DISABLE_PARSE_AS_LIBRARY,
         SWIFT_ENABLE_BARE_SLASH_REGEX,
         SWIFT_ENABLE_EMIT_CONST_VALUES,
         SWIFT_ENABLE_OPAQUE_TYPE_ERASURE,
diff --git a/Sources/SWBCore/SpecImplementations/Tools/SwiftCompiler.swift b/Sources/SWBCore/SpecImplementations/Tools/SwiftCompiler.swift
index 9effd838..09d8f08b 100644
--- a/Sources/SWBCore/SpecImplementations/Tools/SwiftCompiler.swift
+++ b/Sources/SWBCore/SpecImplementations/Tools/SwiftCompiler.swift
@@ -1628,7 +1628,7 @@ public final class SwiftCompilerSpec : CompilerSpec, SpecIdentifierType, SwiftDi
             // If there is only a single input, ensure we pass -parse-as-library as appropriate.
             if cbc.inputs.count == 1 {
                 let filename = cbc.inputs[0].absolutePath.basename
-                if filename != SwiftCompilerSpec.mainFileName && !cbc.scope.evaluate(BuiltinMacros.SWIFT_LIBRARIES_ONLY) {
+                if filename != SwiftCompilerSpec.mainFileName && !cbc.scope.evaluate(BuiltinMacros.SWIFT_LIBRARIES_ONLY) && !cbc.scope.evaluate(BuiltinMacros.SWIFT_DISABLE_PARSE_AS_LIBRARY) {
                     // Add -parse-as-library if the only input's file name isn't main.swift and if we didn't already add it due to SWIFT_LIBRARIES_ONLY.
                     args.append("-parse-as-library")
                 }
diff --git a/Sources/SwiftBuild/ProjectModel/BuildSettings.swift b/Sources/SwiftBuild/ProjectModel/BuildSettings.swift
index 9413ac37..12e5523d 100644
--- a/Sources/SwiftBuild/ProjectModel/BuildSettings.swift
+++ b/Sources/SwiftBuild/ProjectModel/BuildSettings.swift
@@ -99,6 +99,7 @@ extension ProjectModel {
             case STRIP_INSTALLED_PRODUCT
             case SUPPORTS_TEXT_BASED_API
             case SUPPRESS_WARNINGS
+            case SWIFT_DISABLE_PARSE_AS_LIBRARY
             case SWIFT_ENABLE_BARE_SLASH_REGEX
             case SWIFT_INDEX_STORE_ENABLE
             case SWIFT_INSTALL_MODULE
diff --git a/Tests/SWBTaskConstructionTests/SwiftTaskConstructionTests.swift b/Tests/SWBTaskConstructionTests/SwiftTaskConstructionTests.swift
index 62d4d887..21313471 100644
--- a/Tests/SWBTaskConstructionTests/SwiftTaskConstructionTests.swift
+++ b/Tests/SWBTaskConstructionTests/SwiftTaskConstructionTests.swift
@@ -4260,6 +4260,64 @@ fileprivate struct SwiftTaskConstructionTests: CoreBasedTests {
         }
     }
 
+    @Test(.requireSDKs(.host))
+    func swiftDisableParseAsLibrarySettings() async throws {
+        let targetName = "targetName"
+        try await withTemporaryDirectory { tmpDir in
+            let testProject = try await TestProject(
+                "ProjectName",
+                sourceRoot: tmpDir.join("srcroot"),
+                groupTree: TestGroup(
+                    "SomeFiles",
+                    children: [
+                        TestFile("File1.swift"),
+                    ]),
+                targets: [
+                    TestStandardTarget(
+                        targetName,
+                        type: .framework,
+                        buildConfigurations: [
+                            TestBuildConfiguration("Debug", buildSettings: [
+                                "PRODUCT_NAME": "$(TARGET_NAME)",
+                                "SWIFT_EXEC": swiftCompilerPath.str,
+                                "CODE_SIGN_IDENTITY": "",
+                                "SWIFT_VERSION": swiftVersion,
+                            ]),
+                        ],
+                        buildPhases: [
+                            TestSourcesBuildPhase([
+                                TestBuildFile("File1.swift"),
+                            ]),
+                        ])
+                ])
+
+            let tester = try await TaskConstructionTester(getCore(), testProject)
+            await tester.checkBuild(
+                BuildParameters(configuration: "Debug", overrides: ["SWIFT_DISABLE_PARSE_AS_LIBRARY": "YES"]),
+                runDestination: .host,
+            ) { results in
+                results.checkTarget(targetName) { target in
+                    results.checkTask(.matchTarget(target), .matchRuleType("SwiftDriver Compilation")) { task in
+                        task.checkCommandLineDoesNotContain("-parse-as-library")
+                    }
+                }
+            }
+
+            await tester.checkBuild(
+                BuildParameters(configuration: "Debug", overrides: ["SWIFT_DISABLE_PARSE_AS_LIBRARY": "NO"]),
+                runDestination: .host,
+            ) { results in
+                results.checkTarget(targetName) { target in
+                    results.checkTask(.matchTarget(target), .matchRuleType("SwiftDriver Compilation")) { task in
+                        task.checkCommandLineContains(["-parse-as-library"])
+                    }
+                }
+            }
+
+
+        }
+    }
+
     @Test(.requireSDKs(.macOS))
     func layoutStringValueWitnesses() async throws {
         try await withTemporaryDirectory { tmpDir in