diff --git a/Package.swift b/Package.swift
index 6688b6a3..d8896350 100644
--- a/Package.swift
+++ b/Package.swift
@@ -117,6 +117,9 @@ let package = Package(
         .executableTarget(
             name: "build-swiftly-release",
             dependencies: [
+                .target(name: "SwiftlyCore"),
+                .target(name: "LinuxPlatform", condition: .when(platforms: [.linux])),
+                .target(name: "MacOSPlatform", condition: .when(platforms: [.macOS])),
                 .product(name: "ArgumentParser", package: "swift-argument-parser"),
             ],
             path: "Tools/build-swiftly-release"
diff --git a/Sources/MacOSPlatform/MacOS.swift b/Sources/MacOSPlatform/MacOS.swift
index c7a02158..6d289b81 100644
--- a/Sources/MacOSPlatform/MacOS.swift
+++ b/Sources/MacOSPlatform/MacOS.swift
@@ -2,6 +2,7 @@ import Foundation
 import SwiftlyCore
 import SystemPackage
 
+typealias sys = SwiftlyCore.SystemCommand
 typealias fs = SwiftlyCore.FileSystem
 
 public struct SwiftPkgInfo: Codable {
@@ -191,14 +192,8 @@ public struct MacOS: Platform {
     }
 
     public func getShell() async throws -> String {
-        if let directoryInfo = try await runProgramOutput("dscl", ".", "-read", "\(fs.home)") {
-            for line in directoryInfo.components(separatedBy: "\n") {
-                if line.hasPrefix("UserShell: ") {
-                    if case let comps = line.components(separatedBy: ": "), comps.count == 2 {
-                        return comps[1]
-                    }
-                }
-            }
+        for (key, value) in try await sys.dscl(datasource: ".").read(path: fs.home, keys: "UserShell").properties(self) {
+            return value
         }
 
         // Fall back to zsh on macOS
diff --git a/Sources/SwiftlyCore/Commands.swift b/Sources/SwiftlyCore/Commands.swift
new file mode 100644
index 00000000..641fcfbd
--- /dev/null
+++ b/Sources/SwiftlyCore/Commands.swift
@@ -0,0 +1,92 @@
+import Foundation
+import SystemPackage
+
+public enum SystemCommand {}
+
+// This file contains a set of system commands that's used by Swiftly and its related tests and tooling
+
+// Directory Service command line utility for macOS
+// See dscl(1) for details
+extension SystemCommand {
+    public static func dscl(executable: Executable = DsclCommand.defaultExecutable, datasource: String? = nil) -> DsclCommand {
+        DsclCommand(executable: executable, datasource: datasource)
+    }
+
+    public struct DsclCommand {
+        public static var defaultExecutable: Executable { .name("dscl") }
+
+        var executable: Executable
+        var datasource: String?
+
+        internal init(
+            executable: Executable,
+            datasource: String?
+        ) {
+            self.executable = executable
+            self.datasource = datasource
+        }
+
+        func config() -> Configuration {
+            var args: [String] = []
+
+            if let datasource = self.datasource {
+                args += [datasource]
+            }
+
+            return Configuration(
+                executable: self.executable,
+                arguments: Arguments(args),
+                environment: .inherit
+            )
+        }
+
+        public func read(path: FilePath? = nil, keys: [String]) -> ReadCommand {
+            ReadCommand(dscl: self, path: path, keys: keys)
+        }
+
+        public func read(path: FilePath? = nil, keys: String...) -> ReadCommand {
+            self.read(path: path, keys: keys)
+        }
+
+        public struct ReadCommand: Output {
+            var dscl: DsclCommand
+            var path: FilePath?
+            var keys: [String]
+
+            internal init(dscl: DsclCommand, path: FilePath?, keys: [String]) {
+                self.dscl = dscl
+                self.path = path
+                self.keys = keys
+            }
+
+            public func config() -> Configuration {
+                var c = self.dscl.config()
+
+                var args = c.arguments.storage.map(\.description) + ["-read"]
+
+                if let path = self.path {
+                    args += [path.string] + self.keys
+                }
+
+                c.arguments = .init(args)
+
+                return c
+            }
+        }
+    }
+}
+
+extension SystemCommand.DsclCommand.ReadCommand {
+    public func properties(_ p: Platform) async throws -> [(key: String, value: String)] {
+        let output = try await self.output(p)
+        guard let output else { return [] }
+
+        var props: [(key: String, value: String)] = []
+        for line in output.components(separatedBy: "\n") {
+            if case let comps = line.components(separatedBy: ": "), comps.count == 2 {
+                props.append((key: comps[0], value: comps[1]))
+            }
+        }
+        return props
+    }
+}
diff --git a/Sources/SwiftlyCore/ModeledCommandLine.swift b/Sources/SwiftlyCore/ModeledCommandLine.swift
new file mode 100644
index 00000000..a7a21a9b
--- /dev/null
+++ b/Sources/SwiftlyCore/ModeledCommandLine.swift
@@ -0,0 +1,177 @@
+import Foundation
+import SystemPackage
+
+public enum CommandLineError: Error {
+    case invalidArgs
+    case errorExit(exitCode: Int32, program: String)
+    case unknownVersion
+}
+
+// This section is a clone of the Configuration type from the new Subprocess package, until we can depend on that package.
+public struct Configuration: Sendable {
+    /// The executable to run.
+    public var executable: Executable
+    /// The arguments to pass to the executable.
+    public var arguments: Arguments
+    /// The environment to use when running the executable.
+    public var environment: Environment
+}
+
+public struct Executable: Sendable, Hashable {
+    internal enum Storage: Sendable, Hashable {
+        case executable(String)
+        case path(FilePath)
+    }
+
+    internal let storage: Storage
+
+    private init(_config: Storage) {
+        self.storage = _config
+    }
+
+    /// Locate the executable by its name.
+    /// `Subprocess` will use `PATH` value to
+    /// determine the full path to the executable.
+    public static func name(_ executableName: String) -> Self {
+        .init(_config: .executable(executableName))
+    }
+
+    /// Locate the executable by its full path.
+    /// `Subprocess` will use this  path directly.
+    public static func path(_ filePath: FilePath) -> Self {
+        .init(_config: .path(filePath))
+    }
+}
+
+public struct Environment: Sendable, Hashable {
+    internal enum Configuration: Sendable, Hashable {
+        case inherit([String: String])
+        case custom([String: String])
+    }
+
+    internal let config: Configuration
+
+    init(config: Configuration) {
+        self.config = config
+    }
+
+    /// Child process should inherit the same environment
+    /// values from its parent process.
+    public static var inherit: Self {
+        .init(config: .inherit([:]))
+    }
+
+    /// Override the provided `newValue` in the existing `Environment`
+    public func updating(_ newValue: [String: String]) -> Self {
+        .init(config: .inherit(newValue))
+    }
+
+    /// Use custom environment variables
+    public static func custom(_ newValue: [String: String]) -> Self {
+        .init(config: .custom(newValue))
+    }
+}
+
+internal enum StringOrRawBytes: Sendable, Hashable {
+    case string(String)
+
+    var stringValue: String? {
+        switch self {
+        case let .string(string):
+            return string
+        }
+    }
+
+    var description: String {
+        switch self {
+        case let .string(string):
+            return string
+        }
+    }
+
+    var count: Int {
+        switch self {
+        case let .string(string):
+            return string.count
+        }
+    }
+
+    func hash(into hasher: inout Hasher) {
+        // If Raw bytes is valid UTF8, hash it as so
+        switch self {
+        case let .string(string):
+            hasher.combine(string)
+        }
+    }
+}
+
+public struct Arguments: Sendable, ExpressibleByArrayLiteral, Hashable {
+    public typealias ArrayLiteralElement = String
+
+    internal let storage: [StringOrRawBytes]
+
+    /// Create an Arguments object using the given literal values
+    public init(arrayLiteral elements: String...) {
+        self.storage = elements.map { .string($0) }
+    }
+
+    /// Create an Arguments object using the given array
+    public init(_ array: [String]) {
+        self.storage = array.map { .string($0) }
+    }
+}
+
+public protocol Runnable {
+    func config() -> Configuration
+}
+
+extension Runnable {
+    public func run(_ p: Platform, quiet: Bool) async throws {
+        let c = self.config()
+        let executable = switch c.executable.storage {
+        case let .executable(name):
+            name
+        case let .path(p):
+            p.string
+        }
+        let args = c.arguments.storage.map(\.description)
+        var env: [String: String] = ProcessInfo.processInfo.environment
+        switch c.environment.config {
+        case let .inherit(newValue):
+            for (key, value) in newValue {
+                env[key] = value
+            }
+        case let .custom(newValue):
+            env = newValue
+        }
+        try await p.runProgram([executable] + args, quiet: quiet, env: env)
+    }
+}
+
+public protocol Output {
+    func config() -> Configuration
+}
+
+// TODO: look into making this something that can be Decodable (i.e. streamable)
+extension Output {
+    public func output(_ p: Platform) async throws -> String? {
+        let c = self.config()
+        let executable = switch c.executable.storage {
+        case let .executable(name):
+            name
+        case let .path(p):
+            p.string
+        }
+        let args = c.arguments.storage.map(\.description)
+        var env: [String: String] = ProcessInfo.processInfo.environment
+        switch c.environment.config {
+        case let .inherit(newValue):
+            for (key, value) in newValue {
+                env[key] = value
+            }
+        case let .custom(newValue):
+            env = newValue
+        }
+        return try await p.runProgramOutput(executable, args, env: env)
+    }
+}
diff --git a/Tests/SwiftlyTests/CommandLineTests.swift b/Tests/SwiftlyTests/CommandLineTests.swift
new file mode 100644
index 00000000..62e2aecf
--- /dev/null
+++ b/Tests/SwiftlyTests/CommandLineTests.swift
@@ -0,0 +1,31 @@
+@testable import Swiftly
+@testable import SwiftlyCore
+import SystemPackage
+import Testing
+
+public typealias sys = SystemCommand
+
+@Suite
+public struct CommandLineTests {
+    @Test func testDsclModel() {
+        var config = sys.dscl(datasource: ".").read(path: .init("/Users/swiftly"), keys: "UserShell").config()
+        #expect(config.executable == .name("dscl"))
+        #expect(config.arguments.storage.map(\.description) == [".", "-read", "/Users/swiftly", "UserShell"])
+
+        config = sys.dscl(datasource: ".").read(path: .init("/Users/swiftly"), keys: "UserShell", "Picture").config()
+        #expect(config.executable == .name("dscl"))
+        #expect(config.arguments.storage.map(\.description) == [".", "-read", "/Users/swiftly", "UserShell", "Picture"])
+    }
+
+    @Test(
+        .tags(.medium),
+        .enabled {
+            try await sys.DsclCommand.defaultExecutable.exists()
+        }
+    )
+    func testDscl() async throws {
+        let properties = try await sys.dscl(datasource: ".").read(path: fs.home, keys: "UserShell").properties(Swiftly.currentPlatform)
+        #expect(properties.count == 1) // Only one shell for the current user
+        #expect(properties[0].key == "UserShell") // The one property key should be the one that is requested
+    }
+}
diff --git a/Tests/SwiftlyTests/HTTPClientTests.swift b/Tests/SwiftlyTests/HTTPClientTests.swift
index c40235f4..96a0472d 100644
--- a/Tests/SwiftlyTests/HTTPClientTests.swift
+++ b/Tests/SwiftlyTests/HTTPClientTests.swift
@@ -7,7 +7,7 @@ import SystemPackage
 import Testing
 
 @Suite(.serialized) struct HTTPClientTests {
-    @Test func getSwiftOrgGPGKeys() async throws {
+    @Test(.tags(.large)) func getSwiftOrgGPGKeys() async throws {
         let tmpFile = fs.mktemp()
         try await fs.create(file: tmpFile, contents: nil)
 
@@ -24,7 +24,7 @@ import Testing
         }
     }
 
-    @Test func getSwiftToolchain() async throws {
+    @Test(.tags(.large)) func getSwiftToolchain() async throws {
         let tmpFile = fs.mktemp()
         try await fs.create(file: tmpFile, contents: nil)
         let tmpFileSignature = fs.mktemp(ext: ".sig")
@@ -53,7 +53,7 @@ import Testing
         }
     }
 
-    @Test func getSwiftlyRelease() async throws {
+    @Test(.tags(.large)) func getSwiftlyRelease() async throws {
         let tmpFile = fs.mktemp()
         try await fs.create(file: tmpFile, contents: nil)
         let tmpFileSignature = fs.mktemp(ext: ".sig")
@@ -82,7 +82,7 @@ import Testing
         }
     }
 
-    @Test func getSwiftlyReleaseMetadataFromSwiftOrg() async throws {
+    @Test(.tags(.large)) func getSwiftlyReleaseMetadataFromSwiftOrg() async throws {
         let httpClient = SwiftlyHTTPClient(httpRequestExecutor: HTTPRequestExecutorImpl())
         do {
             let currentRelease = try await httpClient.getCurrentSwiftlyRelease()
@@ -94,6 +94,7 @@ import Testing
     }
 
     @Test(
+        .tags(.large),
         arguments:
         [PlatformDefinition.macOS, .ubuntu2404, .ubuntu2204, .rhel9, .fedora39, .amazonlinux2, .debian12],
         [SwiftlyWebsiteAPI.Components.Schemas.Architecture.x8664, .aarch64]
diff --git a/Tests/SwiftlyTests/SwiftlyTests.swift b/Tests/SwiftlyTests/SwiftlyTests.swift
index 1c49e7f5..e74ee1a9 100644
--- a/Tests/SwiftlyTests/SwiftlyTests.swift
+++ b/Tests/SwiftlyTests/SwiftlyTests.swift
@@ -20,6 +20,32 @@ struct SwiftlyTestError: LocalizedError {
     let message: String
 }
 
+extension Tag {
+    @Tag static var medium: Self
+    @Tag static var large: Self
+}
+
+extension Executable {
+    public func exists() async throws -> Bool {
+        switch self.storage {
+        case let .path(p):
+            return (try await FileSystem.exists(atPath: p))
+        case let .executable(e):
+            let path = ProcessInfo.processInfo.environment["PATH"]
+
+            guard let path else { return false }
+
+            for p in path.split(separator: ":") {
+                if try await FileSystem.exists(atPath: FilePath(String(p)) / e) {
+                    return true
+                }
+            }
+
+            return false
+        }
+    }
+}
+
 let unmockedMsg = "All swiftly test case logic must be mocked in order to prevent mutation of the system running the test. This test must either run swiftly components inside a SwiftlyTests.with... closure, or it must have one of the @Test traits, such as @Test(.testHome), or @Test(.mock...)"
 
 actor OutputHandlerFail: OutputHandler {
diff --git a/Tools/build-swiftly-release/BuildSwiftlyRelease.swift b/Tools/build-swiftly-release/BuildSwiftlyRelease.swift
index c4d2bc2c..cf6219b0 100644
--- a/Tools/build-swiftly-release/BuildSwiftlyRelease.swift
+++ b/Tools/build-swiftly-release/BuildSwiftlyRelease.swift
@@ -1,5 +1,18 @@
 import ArgumentParser
 import Foundation
+import SwiftlyCore
+
+#if os(macOS)
+import MacOSPlatform
+#elseif os(Linux)
+import LinuxPlatform
+#endif
+
+#if os(macOS)
+let currentPlatform = MacOS()
+#elseif os(Linux)
+let currentPlatform = Linux()
+#endif
 
 public struct SwiftPlatform: Codable {
     public var name: String?
@@ -110,39 +123,6 @@ public func runProgramOutput(_ program: String, _ args: String...) async throws
     }
 }
 
-#if os(macOS)
-public func getShell() async throws -> String {
-    if let directoryInfo = try await runProgramOutput("dscl", ".", "-read", FileManager.default.homeDirectoryForCurrentUser.path) {
-        for line in directoryInfo.components(separatedBy: "\n") {
-            if line.hasPrefix("UserShell: ") {
-                if case let comps = line.components(separatedBy: ": "), comps.count == 2 {
-                    return comps[1]
-                }
-            }
-        }
-    }
-
-    // Fall back to zsh on macOS
-    return "/bin/zsh"
-}
-
-#elseif os(Linux)
-public func getShell() async throws -> String {
-    if let passwds = try await runProgramOutput("getent", "passwd") {
-        for line in passwds.components(separatedBy: "\n") {
-            if line.hasPrefix("root:") {
-                if case let comps = line.components(separatedBy: ":"), comps.count > 1 {
-                    return comps[comps.count - 1]
-                }
-            }
-        }
-    }
-
-    // Fall back on bash on Linux and other Unixes
-    return "/bin/bash"
-}
-#endif
-
 @main
 struct BuildSwiftlyRelease: AsyncParsableCommand {
     static let configuration = CommandConfiguration(
@@ -183,11 +163,11 @@ struct BuildSwiftlyRelease: AsyncParsableCommand {
     }
 
     func assertTool(_ name: String, message: String) async throws -> String {
-        guard let _ = try? await runProgramOutput(getShell(), "-c", "which which") else {
+        guard let _ = try? await runProgramOutput(currentPlatform.getShell(), "-c", "which which") else {
             throw Error(message: "The which command could not be found. Please install it with your package manager.")
         }
 
-        guard let location = try? await runProgramOutput(getShell(), "-c", "which \(name)") else {
+        guard let location = try? await runProgramOutput(currentPlatform.getShell(), "-c", "which \(name)") else {
             throw Error(message: message)
         }