diff --git a/Sources/SWBTestSupport/CoreTestSupport.swift b/Sources/SWBTestSupport/CoreTestSupport.swift
index e95da70f..1bf280ea 100644
--- a/Sources/SWBTestSupport/CoreTestSupport.swift
+++ b/Sources/SWBTestSupport/CoreTestSupport.swift
@@ -70,6 +70,40 @@ extension Core {
             try POSIX.unsetenv(variable)
         }
 
+        // Handle Xcodes with an unbundled Metal toolchain by querying `xcodebuild` if needed.
+        //
+        // If the given environment already contains `EXTERNAL_TOOLCHAINS_DIR` and `TOOLCHAINS`, we're assuming that we do not have to obtain any toolchain information.
+        var environment = environment
+        if (try? ProcessInfo.processInfo.hostOperatingSystem()) == .macOS, !(environment.contains("EXTERNAL_TOOLCHAINS_DIR") && environment.contains("TOOLCHAINS")) {
+            let activeDeveloperPath: Path
+            if let developerPath {
+                activeDeveloperPath = developerPath.path
+            } else {
+                activeDeveloperPath = try await Xcode.getActiveDeveloperDirectoryPath()
+            }
+            let defaultToolchainPath = activeDeveloperPath.join("Toolchains/XcodeDefault.xctoolchain")
+
+            if !localFS.exists(defaultToolchainPath.join("usr/metal/current")) {
+                struct MetalToolchainInfo: Decodable {
+                    let buildVersion: String
+                    let status: String
+                    let toolchainIdentifier: String
+                    let toolchainSearchPath: String
+                }
+
+                let result = try await Process.getOutput(url: URL(fileURLWithPath: activeDeveloperPath.join("usr/bin/xcodebuild").str), arguments: ["-showComponent", "metalToolchain", "-json"], environment: ["DEVELOPER_DIR": activeDeveloperPath.str])
+                if result.exitStatus != .exit(0) {
+                    throw StubError.error("xcodebuild failed: \(String(data: result.stdout, encoding: .utf8) ?? "")\n\(String(data: result.stderr, encoding: .utf8) ?? "")")
+                }
+
+                let metalToolchainInfo = try JSONDecoder().decode(MetalToolchainInfo.self, from: result.stdout)
+                environment.addContents(of: [
+                    "TOOLCHAINS": "\(metalToolchainInfo.toolchainIdentifier) $(inherited)",
+                    "EXTERNAL_TOOLCHAINS_DIR": metalToolchainInfo.toolchainSearchPath,
+                ])
+            }
+        }
+
         // When this code is being loaded directly via unit tests *and* we detect the products directory we are running in is for Xcode, then we should run using inferior search paths.
         let inferiorProductsPath: Path? = self.inferiorProductsPath()
 
diff --git a/Tests/SWBBuildSystemTests/BuildCommandTests.swift b/Tests/SWBBuildSystemTests/BuildCommandTests.swift
index 2cd6a109..c2aa61af 100644
--- a/Tests/SWBBuildSystemTests/BuildCommandTests.swift
+++ b/Tests/SWBBuildSystemTests/BuildCommandTests.swift
@@ -325,6 +325,7 @@ fileprivate struct BuildCommandTests: CoreBasedTests {
 
     @Test(.requireSDKs(.macOS), .requireXcode16())
     func singleFileCompileMetal() async throws {
+        let core = try await getCore()
         try await withTemporaryDirectory { tmpDirPath async throws -> Void in
             let testWorkspace = try await TestWorkspace(
                 "Test",
@@ -337,6 +338,7 @@ fileprivate struct BuildCommandTests: CoreBasedTests {
                             "Debug",
                             buildSettings: ["PRODUCT_NAME": "$(TARGET_NAME)",
                                             "SWIFT_ENABLE_EXPLICIT_MODULES": "NO",
+                                            "TOOLCHAINS": core.environment["TOOLCHAINS"] ?? "$(inherited)",
                                             "SWIFT_VERSION": swiftVersion])],
                         targets: [
                             TestStandardTarget(
@@ -348,7 +350,7 @@ fileprivate struct BuildCommandTests: CoreBasedTests {
                     )
                 ]
             )
-            let tester = try await BuildOperationTester(getCore(), testWorkspace, simulated: false)
+            let tester = try await BuildOperationTester(core, testWorkspace, simulated: false)
 
             let metalFile = testWorkspace.sourceRoot.join("aProject/Metal.metal")
             try await tester.fs.writeFileContents(metalFile) { stream in }
diff --git a/Tests/SWBBuildSystemTests/BuildOperationTests.swift b/Tests/SWBBuildSystemTests/BuildOperationTests.swift
index 61624fd0..3d5f3dde 100644
--- a/Tests/SWBBuildSystemTests/BuildOperationTests.swift
+++ b/Tests/SWBBuildSystemTests/BuildOperationTests.swift
@@ -5756,6 +5756,7 @@ That command depends on command in Target 'agg2' (project \'aProject\'): script
 
     @Test(.requireSDKs(.macOS))
     func incrementalMetalLinkWithCodeSign() async throws {
+        let core = try await getCore()
         try await withTemporaryDirectory { tmpDirPath async throws -> Void in
             let testWorkspace = try await TestWorkspace(
                 "Test",
@@ -5773,6 +5774,7 @@ That command depends on command in Target 'agg2' (project \'aProject\'): script
                                             "CODE_SIGN_IDENTITY": "-",
                                             "INFOPLIST_FILE": "Info.plist",
                                             "CODESIGN": "/usr/bin/true",
+                                            "TOOLCHAINS": core.environment["TOOLCHAINS"] ?? "$(inherited)",
                                             "SWIFT_VERSION": swiftVersion])],
                         targets: [
                             TestStandardTarget(
@@ -5781,7 +5783,7 @@ That command depends on command in Target 'agg2' (project \'aProject\'): script
                                 buildPhases: [
                                     TestSourcesBuildPhase(["SwiftFile.swift", "Metal.metal"]),
                                 ])])])
-            let tester = try await BuildOperationTester(getCore(), testWorkspace, simulated: false, fileSystem: localFS)
+            let tester = try await BuildOperationTester(core, testWorkspace, simulated: false, fileSystem: localFS)
             let signableTargets: Set<String> = ["aFramework"]
 
             // Create the input files.