diff --git a/Sources/System/Errno.swift b/Sources/System/Errno.swift
index 43b46af5..7d22a540 100644
--- a/Sources/System/Errno.swift
+++ b/Sources/System/Errno.swift
@@ -11,7 +11,7 @@
 /// occurred.
 @frozen
 @available(System 0.0.1, *)
-public struct Errno: RawRepresentable, Error, Hashable, Codable {
+public struct Errno: RawRepresentable, Error, Hashable {
   /// The raw C error number.
   @_alwaysEmitIntoClient
   public let rawValue: CInt
@@ -1562,6 +1562,8 @@ extension Errno: CustomStringConvertible, CustomDebugStringConvertible {
   public var debugDescription: String { self.description }
 }
 
+#if !$Embedded
+
 @available(System 0.0.1, *)
 extension Errno {
   @_alwaysEmitIntoClient
@@ -1571,3 +1573,13 @@ extension Errno {
   }
 }
 
+@available(System 0.0.1, *)
+extension Errno: Codable {}
+
+public typealias SystemError = any Error
+
+#else
+
+public typealias SystemError = Errno
+
+#endif // !$Embedded
diff --git a/Sources/System/FileDescriptor.swift b/Sources/System/FileDescriptor.swift
index d5f5883b..31bfdaef 100644
--- a/Sources/System/FileDescriptor.swift
+++ b/Sources/System/FileDescriptor.swift
@@ -15,7 +15,7 @@
 /// in the same way as you manage a raw C file handle.
 @frozen
 @available(System 0.0.1, *)
-public struct FileDescriptor: RawRepresentable, Hashable, Codable {
+public struct FileDescriptor: RawRepresentable, Hashable {
   /// The raw C file handle.
   @_alwaysEmitIntoClient
   public let rawValue: CInt
@@ -46,7 +46,7 @@ extension FileDescriptor {
   /// The desired read and write access for a newly opened file.
   @frozen
   @available(System 0.0.1, *)
-  public struct AccessMode: RawRepresentable, Sendable, Hashable, Codable {
+  public struct AccessMode: RawRepresentable, Sendable, Hashable {
     /// The raw C access mode.
     @_alwaysEmitIntoClient
     public var rawValue: CInt
@@ -89,7 +89,7 @@ extension FileDescriptor {
   /// Options that specify behavior for a newly-opened file.
   @frozen
   @available(System 0.0.1, *)
-  public struct OpenOptions: OptionSet, Sendable, Hashable, Codable {
+  public struct OpenOptions: OptionSet, Sendable, Hashable {
     /// The raw C options.
     @_alwaysEmitIntoClient
     public var rawValue: CInt
@@ -327,7 +327,7 @@ extension FileDescriptor {
   /// Options for specifying what a file descriptor's offset is relative to.
   @frozen
   @available(System 0.0.1, *)
-  public struct SeekOrigin: RawRepresentable, Sendable, Hashable, Codable {
+  public struct SeekOrigin: RawRepresentable, Sendable, Hashable {
     /// The raw C value.
     @_alwaysEmitIntoClient
     public var rawValue: CInt
@@ -402,6 +402,22 @@ extension FileDescriptor {
   }
 }
 
+#if !$Embedded
+
+@available(System 0.0.1, *)
+extension FileDescriptor: Codable {}
+
+@available(System 0.0.1, *)
+extension FileDescriptor.AccessMode: Codable {}
+
+@available(System 0.0.1, *)
+extension FileDescriptor.OpenOptions: Codable {}
+
+@available(System 0.0.1, *)
+extension FileDescriptor.SeekOrigin: Codable {}
+
+#endif // !$Embedded
+
 @available(System 0.0.1, *)
 extension FileDescriptor.AccessMode
   : CustomStringConvertible, CustomDebugStringConvertible
diff --git a/Sources/System/FileOperations.swift b/Sources/System/FileOperations.swift
index 9ddc16c3..d6383e1c 100644
--- a/Sources/System/FileOperations.swift
+++ b/Sources/System/FileOperations.swift
@@ -30,24 +30,24 @@ extension FileDescriptor {
     options: FileDescriptor.OpenOptions = FileDescriptor.OpenOptions(),
     permissions: FilePermissions? = nil,
     retryOnInterrupt: Bool = true
-  ) throws -> FileDescriptor {
+  ) throws(SystemError) -> FileDescriptor {
     #if !os(Windows)
-    return try path.withCString {
+    return try path.withCString { (cString) throws(SystemError) in
       try FileDescriptor.open(
-        $0, mode, options: options, permissions: permissions, retryOnInterrupt: retryOnInterrupt)
+        cString, mode, options: options, permissions: permissions, retryOnInterrupt: retryOnInterrupt)
     }
-    #else 
-    return try path.withPlatformString {
+    #else
+    return try path.withPlatformString { (platformString) throws(SystemError) in
       try FileDescriptor.open(
-        $0, mode, options: options, permissions: permissions, retryOnInterrupt: retryOnInterrupt)
+        platformString, mode, options: options, permissions: permissions, retryOnInterrupt: retryOnInterrupt)
     }
     #endif
   }
 
-  #if !os(Windows) 
-  // On Darwin, `CInterop.PlatformChar` is less available than 
+  #if !os(Windows)
+  // On Darwin, `CInterop.PlatformChar` is less available than
   // `FileDescriptor.open`, so we need to use `CChar` instead.
-  
+
   /// Opens or creates a file for reading or writing.
   ///
   /// - Parameters:
@@ -69,7 +69,7 @@ extension FileDescriptor {
     options: FileDescriptor.OpenOptions = FileDescriptor.OpenOptions(),
     permissions: FilePermissions? = nil,
     retryOnInterrupt: Bool = true
-  ) throws -> FileDescriptor {
+  ) throws(SystemError) -> FileDescriptor {
     try FileDescriptor._open(
       path, mode, options: options, permissions: permissions, retryOnInterrupt: retryOnInterrupt
     ).get()
@@ -116,7 +116,7 @@ extension FileDescriptor {
     options: FileDescriptor.OpenOptions = FileDescriptor.OpenOptions(),
     permissions: FilePermissions? = nil,
     retryOnInterrupt: Bool = true
-  ) throws -> FileDescriptor {
+  ) throws(SystemError) -> FileDescriptor {
     try FileDescriptor._open(
       path, mode, options: options, permissions: permissions, retryOnInterrupt: retryOnInterrupt
     ).get()
@@ -149,7 +149,7 @@ extension FileDescriptor {
   ///
   /// The corresponding C function is `close`.
   @_alwaysEmitIntoClient
-  public func close() throws { try _close().get() }
+  public func close() throws(SystemError) { try _close().get() }
 
   @usableFromInline
   internal func _close() -> Result<(), Errno> {
@@ -169,7 +169,7 @@ extension FileDescriptor {
   @discardableResult
   public func seek(
     offset: Int64, from whence: FileDescriptor.SeekOrigin
-  ) throws -> Int64 {
+  ) throws(SystemError) -> Int64 {
     try _seek(offset: offset, from: whence).get()
   }
 
@@ -187,7 +187,7 @@ extension FileDescriptor {
   @available(*, unavailable, renamed: "seek")
   public func lseek(
     offset: Int64, from whence: FileDescriptor.SeekOrigin
-  ) throws -> Int64 {
+  ) throws(SystemError) -> Int64 {
     try seek(offset: offset, from: whence)
   }
 
@@ -214,7 +214,7 @@ extension FileDescriptor {
   public func read(
     into buffer: UnsafeMutableRawBufferPointer,
     retryOnInterrupt: Bool = true
-  ) throws -> Int {
+  ) throws(SystemError) -> Int {
     try _read(into: buffer, retryOnInterrupt: retryOnInterrupt).get()
   }
 
@@ -222,7 +222,7 @@ extension FileDescriptor {
   internal func _read(
     into buffer: UnsafeMutableRawBufferPointer,
     retryOnInterrupt: Bool
-  ) throws -> Result<Int, Errno> {
+  ) throws(SystemError) -> Result<Int, Errno> {
     valueOrErrno(retryOnInterrupt: retryOnInterrupt) {
       system_read(self.rawValue, buffer.baseAddress, buffer.count)
     }
@@ -251,7 +251,7 @@ extension FileDescriptor {
     fromAbsoluteOffset offset: Int64,
     into buffer: UnsafeMutableRawBufferPointer,
     retryOnInterrupt: Bool = true
-  ) throws -> Int {
+  ) throws(SystemError) -> Int {
     try _read(
       fromAbsoluteOffset: offset,
       into: buffer,
@@ -276,7 +276,7 @@ extension FileDescriptor {
     fromAbsoluteOffset offset: Int64,
     into buffer: UnsafeMutableRawBufferPointer,
     retryOnInterrupt: Bool = true
-  ) throws -> Int {
+  ) throws(SystemError) -> Int {
     try read(
       fromAbsoluteOffset: offset,
       into: buffer,
@@ -303,7 +303,7 @@ extension FileDescriptor {
   public func write(
     _ buffer: UnsafeRawBufferPointer,
     retryOnInterrupt: Bool = true
-  ) throws -> Int {
+  ) throws(SystemError) -> Int {
     try _write(buffer, retryOnInterrupt: retryOnInterrupt).get()
   }
 
@@ -337,7 +337,7 @@ extension FileDescriptor {
     toAbsoluteOffset offset: Int64,
     _ buffer: UnsafeRawBufferPointer,
     retryOnInterrupt: Bool = true
-  ) throws -> Int {
+  ) throws(SystemError) -> Int {
     try _write(toAbsoluteOffset: offset, buffer, retryOnInterrupt: retryOnInterrupt).get()
   }
 
@@ -359,7 +359,7 @@ extension FileDescriptor {
     toAbsoluteOffset offset: Int64,
     into buffer: UnsafeRawBufferPointer,
     retryOnInterrupt: Bool = true
-  ) throws -> Int {
+  ) throws(SystemError) -> Int {
     try write(
       toAbsoluteOffset: offset,
       buffer,
@@ -402,7 +402,7 @@ extension FileDescriptor {
   public func duplicate(
     as target: FileDescriptor? = nil,
     retryOnInterrupt: Bool = true
-  ) throws -> FileDescriptor {
+  ) throws(SystemError) -> FileDescriptor {
     try _duplicate(as: target, retryOnInterrupt: retryOnInterrupt).get()
   }
 
@@ -411,7 +411,7 @@ extension FileDescriptor {
   internal func _duplicate(
     as target: FileDescriptor?,
     retryOnInterrupt: Bool
-  ) throws -> Result<FileDescriptor, Errno> {
+  ) throws(SystemError) -> Result<FileDescriptor, Errno> {
     valueOrErrno(retryOnInterrupt: retryOnInterrupt) {
       if let target = target {
         return system_dup2(self.rawValue, target.rawValue)
@@ -422,13 +422,13 @@ extension FileDescriptor {
 
   @_alwaysEmitIntoClient
   @available(*, unavailable, renamed: "duplicate")
-  public func dup() throws -> FileDescriptor {
+  public func dup() throws(SystemError) -> FileDescriptor {
     fatalError("Not implemented")
   }
 
   @_alwaysEmitIntoClient
   @available(*, unavailable, renamed: "duplicate")
-  public func dup2() throws -> FileDescriptor {
+  public func dup2() throws(SystemError) -> FileDescriptor {
     fatalError("Not implemented")
   }
 }
@@ -444,7 +444,7 @@ extension FileDescriptor {
   /// The corresponding C function is `pipe`.
   @_alwaysEmitIntoClient
   @available(System 1.1.0, *)
-  public static func pipe() throws -> (readEnd: FileDescriptor, writeEnd: FileDescriptor) {
+  public static func pipe() throws(SystemError) -> (readEnd: FileDescriptor, writeEnd: FileDescriptor) {
     try _pipe().get()
   }
 
@@ -490,7 +490,7 @@ extension FileDescriptor {
   public func resize(
     to newSize: Int64,
     retryOnInterrupt: Bool = true
-  ) throws {
+  ) throws(SystemError) {
     try _resize(
       to: newSize,
       retryOnInterrupt: retryOnInterrupt
@@ -537,7 +537,7 @@ extension FilePermissions {
   /// afterwards, because of the way reading the creation mask works.
   internal static func withCreationMask<R>(
     _ permissions: FilePermissions,
-    body: () throws -> R
+    body: () throws(SystemError) -> R
   ) rethrows -> R {
     let oldMask = _umask(permissions.rawValue)
     defer {
diff --git a/Sources/System/FilePath/FilePath.swift b/Sources/System/FilePath/FilePath.swift
index b27d053a..19c244ea 100644
--- a/Sources/System/FilePath/FilePath.swift
+++ b/Sources/System/FilePath/FilePath.swift
@@ -68,6 +68,8 @@ extension FilePath {
 @available(System 0.0.1, *)
 extension FilePath: Hashable {}
 
+#if !$Embedded
+
 @available(System 0.0.1, *)
 extension FilePath: Codable {
   // Encoder is synthesized; it probably should have been explicit and used
@@ -88,3 +90,5 @@ extension FilePath: Codable {
     }
   }
 }
+
+#endif // !$Embedded
diff --git a/Sources/System/FilePath/FilePathComponents.swift b/Sources/System/FilePath/FilePathComponents.swift
index f2352617..8913616c 100644
--- a/Sources/System/FilePath/FilePathComponents.swift
+++ b/Sources/System/FilePath/FilePathComponents.swift
@@ -128,6 +128,8 @@ extension SystemString {
   }
 }
 
+#if !$Embedded
+
 // Unifying protocol for common functionality between roots, components,
 // and views onto SystemString and FilePath.
 internal protocol _StrSlice: _PlatformStringable, Hashable, Codable {
@@ -138,6 +140,20 @@ internal protocol _StrSlice: _PlatformStringable, Hashable, Codable {
 
   func _invariantCheck()
 }
+
+#else
+
+internal protocol _StrSlice: _PlatformStringable, Hashable {
+  var _storage: SystemString { get }
+  var _range: Range<SystemString.Index> { get }
+
+  init?(_ str: SystemString)
+
+  func _invariantCheck()
+}
+
+#endif // !$Embedded
+
 extension _StrSlice {
   internal var _slice: Slice<SystemString> {
     Slice(base: _storage, bounds: _range)
diff --git a/Sources/System/FilePath/FilePathString.swift b/Sources/System/FilePath/FilePathString.swift
index 45f79c8a..d61779ca 100644
--- a/Sources/System/FilePath/FilePathString.swift
+++ b/Sources/System/FilePath/FilePathString.swift
@@ -64,7 +64,7 @@ extension FilePath {
   }
 
 #if !os(Windows)
-  // Note: This function should have been opaque, but it shipped as 
+  // Note: This function should have been opaque, but it shipped as
   // `@_alwaysEmitIntoClient` in macOS 12/iOS 15, and now it is stuck
   // this way forever. (Or until the language provides a way for us
   // to declare separate availability for a function's exported symbol
@@ -84,7 +84,7 @@ extension FilePath {
   /// Don't try to store the pointer for later use.
   @_alwaysEmitIntoClient
   public func withPlatformString<Result>(
-    _ body: (UnsafePointer<CInterop.PlatformChar>) throws -> Result
+    _ body: (UnsafePointer<CInterop.PlatformChar>) throws(SystemError) -> Result
   ) rethrows -> Result {
     return try withCString(body)
   }
@@ -102,7 +102,7 @@ extension FilePath {
   /// only during the execution of this method.
   /// Don't try to store the pointer for later use.
   public func withPlatformString<Result>(
-    _ body: (UnsafePointer<CInterop.PlatformChar>) throws -> Result
+    _ body: (UnsafePointer<CInterop.PlatformChar>) throws(SystemError) -> Result
   ) rethrows -> Result {
     return try _withPlatformString(body)
   }
@@ -595,8 +595,8 @@ extension FilePath {
   /// For backwards compatibility only. This function is equivalent to
   /// the preferred `withPlatformString`.
   public func withCString<Result>(
-    _ body: (UnsafePointer<CChar>) throws -> Result
-  ) rethrows -> Result {
+    _ body: (UnsafePointer<CChar>) throws(SystemError) -> Result
+  ) throws(SystemError) -> Result {
     return try _withPlatformString(body)
   }
 }
diff --git a/Sources/System/FilePath/FilePathTemp.swift b/Sources/System/FilePath/FilePathTemp.swift
index c0edf95d..32587c28 100644
--- a/Sources/System/FilePath/FilePathTemp.swift
+++ b/Sources/System/FilePath/FilePathTemp.swift
@@ -20,8 +20,8 @@
 /// deletes the directory and all of its contents before returning.
 internal func withTemporaryFilePath<R>(
   basename: FilePath.Component,
-  _ body: (FilePath) throws -> R
-) throws -> R {
+  _ body: (FilePath) throws(SystemError) -> R
+) throws(SystemError) -> R {
   let temporaryDir = try createUniqueTemporaryDirectory(basename: basename)
   defer {
     try? _recursiveRemove(at: temporaryDir)
@@ -44,9 +44,9 @@ fileprivate let base64 = Array<UInt8>(
 ///
 /// This function will throw if there is an error, except if the error
 /// is that the directory exists, in which case it returns `false`.
-fileprivate func makeLockedDownDirectory(at path: FilePath) throws -> Bool {
-  return try path.withPlatformString {
-    if system_mkdir($0, 0o700) == 0 {
+fileprivate func makeLockedDownDirectory(at path: FilePath) throws(SystemError) -> Bool {
+  return try path.withPlatformString { (platformString) throws(SystemError) in
+    if system_mkdir(platformString, 0o700) == 0 {
       return true
     }
     let err = system_errno
@@ -83,7 +83,7 @@ fileprivate func createRandomString(length: Int) -> String {
 /// string of characters.
 fileprivate func createUniqueTemporaryDirectory(
   basename: FilePath.Component
-) throws -> FilePath {
+) throws(SystemError) -> FilePath {
   var tempDir = try _getTemporaryDirectory()
   tempDir.append(basename)
 
diff --git a/Sources/System/FilePath/FilePathTempPosix.swift b/Sources/System/FilePath/FilePathTempPosix.swift
index e8713c2b..d779850f 100644
--- a/Sources/System/FilePath/FilePathTempPosix.swift
+++ b/Sources/System/FilePath/FilePathTempPosix.swift
@@ -10,7 +10,7 @@
 #if !os(Windows)
 
 /// Get the path to the system temporary directory.
-internal func _getTemporaryDirectory() throws -> FilePath {
+internal func _getTemporaryDirectory() throws(SystemError) -> FilePath {
   guard let tmp = system_getenv("TMPDIR") else {
     return "/tmp"
   }
@@ -26,22 +26,22 @@ internal func _getTemporaryDirectory() throws -> FilePath {
 /// Removes a directory completely, including all of its contents.
 internal func _recursiveRemove(
   at path: FilePath
-) throws {
+) throws(SystemError) {
   let dirfd = try FileDescriptor.open(path, .readOnly, options: .directory)
   defer {
     try? dirfd.close()
   }
 
   let dot: (CInterop.PlatformChar, CInterop.PlatformChar) = (46, 0)
-  try withUnsafeBytes(of: dot) {
+  try withUnsafeBytes(of: dot) { (bytes) throws(SystemError) in
     try recursiveRemove(
       in: dirfd.rawValue,
-      name: $0.assumingMemoryBound(to: CInterop.PlatformChar.self).baseAddress!
+      name: bytes.assumingMemoryBound(to: CInterop.PlatformChar.self).baseAddress!
     )
   }
 
-  try path.withPlatformString {
-    if system_rmdir($0) != 0 {
+  try path.withPlatformString { (platformString) throws(SystemError) in
+    if system_rmdir(platformString) != 0 {
       throw Errno.current
     }
   }
@@ -81,8 +81,8 @@ fileprivate func impl_opendirat(
 fileprivate func forEachFile(
   in dirfd: CInt,
   subdir: UnsafePointer<CInterop.PlatformChar>,
-  _ body: (system_dirent) throws -> ()
-) throws {
+  _ body: (system_dirent) throws(SystemError) -> ()
+) throws(SystemError) {
   guard let dir = impl_opendirat(dirfd, subdir) else {
     throw Errno.current
   }
@@ -113,7 +113,7 @@ fileprivate func forEachFile(
 fileprivate func recursiveRemove(
   in dirfd: CInt,
   name: UnsafePointer<CInterop.PlatformChar>
-) throws {
+) throws(SystemError) {
   // First, deal with subdirectories
   try forEachFile(in: dirfd, subdir: name) { dirent in
     if dirent.d_type == SYSTEM_DT_DIR {
diff --git a/Sources/System/FilePermissions.swift b/Sources/System/FilePermissions.swift
index f849a997..8cebee0b 100644
--- a/Sources/System/FilePermissions.swift
+++ b/Sources/System/FilePermissions.swift
@@ -18,7 +18,7 @@
 ///     perms == [.ownerReadWrite, .groupRead, .otherRead] // true
 @frozen
 @available(System 0.0.1, *)
-public struct FilePermissions: OptionSet, Sendable, Hashable, Codable {
+public struct FilePermissions: OptionSet, Sendable, Hashable {
   /// The raw C file permissions.
   @_alwaysEmitIntoClient
   public let rawValue: CModeT
@@ -172,3 +172,8 @@ extension FilePermissions
   /// A textual representation of the file permissions, suitable for debugging.
   public var debugDescription: String { self.description }
 }
+
+#if !$Embedded
+@available(System 0.0.1, *)
+extension FilePermissions: Codable {}
+#endif
diff --git a/Sources/System/Internals/Exports.swift b/Sources/System/Internals/Exports.swift
index d18102a2..7f76dc34 100644
--- a/Sources/System/Internals/Exports.swift
+++ b/Sources/System/Internals/Exports.swift
@@ -116,9 +116,9 @@ internal func system_memset(
 
 // Interop between String and platfrom string
 extension String {
-  internal func _withPlatformString<Result>(
-    _ body: (UnsafePointer<CInterop.PlatformChar>) throws -> Result
-  ) rethrows -> Result {
+  internal func _withPlatformString<Success, Failure: Error>(
+    _ body: (UnsafePointer<CInterop.PlatformChar>) throws(Failure) -> Success
+  ) throws(Failure) -> Success {
     // Need to #if because CChar may be signed
     #if os(Windows)
     return try withCString(encodedAs: CInterop.PlatformUnicodeEncoding.self, body)
diff --git a/Sources/System/Internals/Mocking.swift b/Sources/System/Internals/Mocking.swift
index ffdaaa92..7cc09d16 100644
--- a/Sources/System/Internals/Mocking.swift
+++ b/Sources/System/Internals/Mocking.swift
@@ -17,7 +17,7 @@
 // enabled in testing builds of System currently, to minimize runtime overhead of release builds.
 //
 
-#if ENABLE_MOCKING
+#if ENABLE_MOCKING && !$Embedded
 internal struct Trace {
   internal struct Entry {
 
@@ -115,12 +115,12 @@ extension MockingDriver {
   }
 }
 
-#endif // ENABLE_MOCKING
+#endif // ENABLE_MOCKING && !$Embedded
 
 @inline(__always)
 internal var mockingEnabled: Bool {
   // Fast constant-foldable check for release builds
-  #if ENABLE_MOCKING
+  #if ENABLE_MOCKING && !$Embedded
     return contextualMockingEnabled
   #else
     return false
@@ -129,15 +129,15 @@ internal var mockingEnabled: Bool {
 
 @inline(__always)
 internal var forceWindowsPaths: Bool? {
-  #if !ENABLE_MOCKING
-  return nil
-  #else
+  #if ENABLE_MOCKING && !$Embedded
   return MockingDriver.forceWindowsPaths
+  #else
+  return nil
   #endif
 }
 
 
-#if ENABLE_MOCKING
+#if ENABLE_MOCKING && !$Embedded
 // Strip the mock_system prefix and the arg list suffix
 private func originalSyscallName(_ function: String) -> String {
   // `function` must be of format `system_<name>(<parameters>)`
@@ -193,12 +193,12 @@ internal func _mockOffT(
 ) -> _COffT {
   _COffT(mockImpl(name: name, path: path, args))
 }
-#endif // ENABLE_MOCKING
+#endif // ENABLE_MOCKING && !$Embedded
 
 // Force paths to be treated as Windows syntactically if `enabled` is
 // true, and as POSIX syntactically if not.
 internal func _withWindowsPaths(enabled: Bool, _ body: () -> ()) {
-  #if ENABLE_MOCKING
+  #if ENABLE_MOCKING && !$Embedded
   MockingDriver.withMockingEnabled { driver in
     driver.forceWindowsSyntaxForPaths = enabled
     body()
diff --git a/Sources/System/Internals/Syscalls.swift b/Sources/System/Internals/Syscalls.swift
index f6eb5339..23a0a2d4 100644
--- a/Sources/System/Internals/Syscalls.swift
+++ b/Sources/System/Internals/Syscalls.swift
@@ -31,7 +31,7 @@ import Android
 internal func system_open(
   _ path: UnsafePointer<CInterop.PlatformChar>, _ oflag: Int32
 ) -> CInt {
-#if ENABLE_MOCKING
+#if ENABLE_MOCKING && !$Embedded
   if mockingEnabled {
     return _mock(path: path, oflag)
   }
@@ -43,7 +43,7 @@ internal func system_open(
   _ path: UnsafePointer<CInterop.PlatformChar>,
   _ oflag: Int32, _ mode: CInterop.Mode
 ) -> CInt {
-#if ENABLE_MOCKING
+#if ENABLE_MOCKING && !$Embedded
   if mockingEnabled {
     return _mock(path: path, oflag, mode)
   }
@@ -53,7 +53,7 @@ internal func system_open(
 
 // close
 internal func system_close(_ fd: Int32) -> Int32 {
-#if ENABLE_MOCKING
+#if ENABLE_MOCKING && !$Embedded
   if mockingEnabled { return _mock(fd) }
 #endif
   return close(fd)
@@ -63,7 +63,7 @@ internal func system_close(_ fd: Int32) -> Int32 {
 internal func system_read(
   _ fd: Int32, _ buf: UnsafeMutableRawPointer?, _ nbyte: Int
 ) -> Int {
-#if ENABLE_MOCKING
+#if ENABLE_MOCKING && !$Embedded
   if mockingEnabled { return _mockInt(fd, buf, nbyte) }
 #endif
   return read(fd, buf, nbyte)
@@ -73,7 +73,7 @@ internal func system_read(
 internal func system_pread(
   _ fd: Int32, _ buf: UnsafeMutableRawPointer?, _ nbyte: Int, _ offset: off_t
 ) -> Int {
-#if ENABLE_MOCKING
+#if ENABLE_MOCKING && !$Embedded
   if mockingEnabled { return _mockInt(fd, buf, nbyte, offset) }
 #endif
 #if os(Android)
@@ -91,7 +91,7 @@ internal func system_pread(
 internal func system_lseek(
   _ fd: Int32, _ off: off_t, _ whence: Int32
 ) -> off_t {
-#if ENABLE_MOCKING
+#if ENABLE_MOCKING && !$Embedded
   if mockingEnabled { return _mockOffT(fd, off, whence) }
 #endif
   return lseek(fd, off, whence)
@@ -101,7 +101,7 @@ internal func system_lseek(
 internal func system_write(
   _ fd: Int32, _ buf: UnsafeRawPointer?, _ nbyte: Int
 ) -> Int {
-#if ENABLE_MOCKING
+#if ENABLE_MOCKING && !$Embedded
   if mockingEnabled { return _mockInt(fd, buf, nbyte) }
 #endif
   return write(fd, buf, nbyte)
@@ -111,7 +111,7 @@ internal func system_write(
 internal func system_pwrite(
   _ fd: Int32, _ buf: UnsafeRawPointer?, _ nbyte: Int, _ offset: off_t
 ) -> Int {
-#if ENABLE_MOCKING
+#if ENABLE_MOCKING && !$Embedded
   if mockingEnabled { return _mockInt(fd, buf, nbyte, offset) }
 #endif
 #if os(Android)
@@ -127,14 +127,14 @@ internal func system_pwrite(
 
 #if !os(WASI)
 internal func system_dup(_ fd: Int32) -> Int32 {
-  #if ENABLE_MOCKING
+#if ENABLE_MOCKING && !$Embedded
   if mockingEnabled { return _mock(fd) }
   #endif
   return dup(fd)
 }
 
 internal func system_dup2(_ fd: Int32, _ fd2: Int32) -> Int32 {
-  #if ENABLE_MOCKING
+#if ENABLE_MOCKING && !$Embedded
   if mockingEnabled { return _mock(fd, fd2) }
   #endif
   return dup2(fd, fd2)
@@ -143,7 +143,7 @@ internal func system_dup2(_ fd: Int32, _ fd2: Int32) -> Int32 {
 
 #if !os(WASI)
 internal func system_pipe(_ fds: UnsafeMutablePointer<Int32>) -> CInt {
-#if ENABLE_MOCKING
+#if ENABLE_MOCKING && !$Embedded
   if mockingEnabled { return _mock(fds) }
 #endif
   return pipe(fds)
@@ -151,7 +151,7 @@ internal func system_pipe(_ fds: UnsafeMutablePointer<Int32>) -> CInt {
 #endif
 
 internal func system_ftruncate(_ fd: Int32, _ length: off_t) -> Int32 {
-#if ENABLE_MOCKING
+#if ENABLE_MOCKING && !$Embedded
   if mockingEnabled { return _mock(fd, length) }
 #endif
   return ftruncate(fd, length)
@@ -161,7 +161,7 @@ internal func system_mkdir(
     _ path: UnsafePointer<CInterop.PlatformChar>,
     _ mode: CInterop.Mode
 ) -> CInt {
-#if ENABLE_MOCKING
+#if ENABLE_MOCKING && !$Embedded
   if mockingEnabled { return _mock(path: path, mode) }
 #endif
   return mkdir(path, mode)
@@ -170,7 +170,7 @@ internal func system_mkdir(
 internal func system_rmdir(
     _ path: UnsafePointer<CInterop.PlatformChar>
 ) -> CInt {
-#if ENABLE_MOCKING
+#if ENABLE_MOCKING && !$Embedded
   if mockingEnabled { return _mock(path: path) }
 #endif
   return rmdir(path)
@@ -208,7 +208,7 @@ internal func system_unlinkat(
   _ path: UnsafePointer<CInterop.PlatformChar>,
   _ flag: CInt
 ) -> CInt {
-#if ENABLE_MOCKING
+#if ENABLE_MOCKING && !$Embedded
   if mockingEnabled { return _mock(fd, path, flag) }
 #endif
 return unlinkat(fd, path, flag)
@@ -247,7 +247,7 @@ internal func system_openat(
   _ path: UnsafePointer<CInterop.PlatformChar>,
   _ oflag: Int32
 ) -> CInt {
-#if ENABLE_MOCKING
+#if ENABLE_MOCKING && !$Embedded
   if mockingEnabled {
     return _mock(fd, path, oflag)
   }
diff --git a/Sources/System/PlatformString.swift b/Sources/System/PlatformString.swift
index 7b8fd90c..0703c4bd 100644
--- a/Sources/System/PlatformString.swift
+++ b/Sources/System/PlatformString.swift
@@ -158,8 +158,8 @@ extension String {
   /// only during the execution of this method.
   /// Don't try to store the pointer for later use.
   public func withPlatformString<Result>(
-    _ body: (UnsafePointer<CInterop.PlatformChar>) throws -> Result
-  ) rethrows -> Result {
+    _ body: (UnsafePointer<CInterop.PlatformChar>) throws(SystemError) -> Result
+  ) throws(SystemError) -> Result {
     try _withPlatformString(body)
   }
 
@@ -189,8 +189,8 @@ extension CInterop.PlatformUnicodeEncoding.CodeUnit {
 
 internal protocol _PlatformStringable {
   func _withPlatformString<Result>(
-    _ body: (UnsafePointer<CInterop.PlatformChar>) throws -> Result
-  ) rethrows -> Result
+    _ body: (UnsafePointer<CInterop.PlatformChar>) throws(SystemError) -> Result
+  ) throws(SystemError) -> Result
 
   init?(_platformString: UnsafePointer<CInterop.PlatformChar>)
 }
diff --git a/Sources/System/SystemString.swift b/Sources/System/SystemString.swift
index 57abc625..118b99f0 100644
--- a/Sources/System/SystemString.swift
+++ b/Sources/System/SystemString.swift
@@ -9,7 +9,7 @@
 
 // A platform-native character representation, currently used for file paths
 internal struct SystemChar:
-  RawRepresentable, Sendable, Comparable, Hashable, Codable {
+  RawRepresentable, Sendable, Comparable, Hashable {
   internal typealias RawValue = CInterop.PlatformChar
 
   internal var rawValue: RawValue
@@ -23,6 +23,12 @@ internal struct SystemChar:
   }
 }
 
+#if !$Embedded
+
+extension SystemChar: Codable {}
+
+#endif // !$Embedded
+
 extension SystemChar {
   internal init(ascii: Unicode.Scalar) {
     self.init(rawValue: numericCast(UInt8(ascii: ascii)))
@@ -104,7 +110,7 @@ extension SystemString {
     }
     return true
   }
-  
+
   fileprivate func _invariantCheck() {
     #if DEBUG
     precondition(_invariantsSatisfied())
@@ -173,10 +179,14 @@ extension SystemString: RangeReplaceableCollection {
   }
 }
 
-extension SystemString: Hashable, Codable {
+extension SystemString: Hashable {}
+
+#if !$Embedded
+
+extension SystemString: Codable {
   // Encoder is synthesized; it probably should have been explicit and used
   // a single-value container, but making that change now is somewhat risky.
-  
+
   // Decoder is written explicitly to ensure that we validate invariants on
   // untrusted input.
   public init(from decoder: any Decoder) throws {
@@ -195,6 +205,8 @@ extension SystemString: Hashable, Codable {
   }
 }
 
+#endif // !$Embedded
+
 extension SystemString {
 
   internal func withNullTerminatedSystemChars<T>(
diff --git a/Sources/System/Util.swift b/Sources/System/Util.swift
index e4832ac5..c100ac51 100644
--- a/Sources/System/Util.swift
+++ b/Sources/System/Util.swift
@@ -43,6 +43,8 @@ internal func nothingOrErrno<I: FixedWidthInteger>(
   valueOrErrno(retryOnInterrupt: retryOnInterrupt, f).map { _ in () }
 }
 
+#if !$Embedded
+
 // Run a precondition for debug client builds
 internal func _debugPrecondition(
   _ condition: @autoclosure () -> Bool,
@@ -56,6 +58,8 @@ internal func _debugPrecondition(
   }
 }
 
+#endif // !$Embedded
+
 extension OpaquePointer {
   internal var _isNULL: Bool {
     OpaquePointer(bitPattern: Int(bitPattern: self)) == nil