diff --git a/Examples/math/main.swift b/Examples/math/main.swift
index 5e40f684c..acbc500b2 100644
--- a/Examples/math/main.swift
+++ b/Examples/math/main.swift
@@ -21,11 +21,6 @@ struct Math: ParsableCommand {
         // Commands can define a version for automatic '--version' support.
         version: "1.0.0",
 
-        // Pass an array to `subcommands` to set up a nested tree of subcommands.
-        // With language support for type-level introspection, this could be
-        // provided by automatically finding nested `ParsableCommand` types.
-        subcommands: [Add.self, Multiply.self, Statistics.self],
-
         // A default subcommand, when provided, is automatically selected if a
         // subcommand is not given on the command line.
         defaultSubcommand: Add.self)
@@ -82,8 +77,7 @@ extension Math {
             // Command names are automatically generated from the type name
             // by default; you can specify an override here.
             commandName: "stats",
-            abstract: "Calculate descriptive statistics.",
-            subcommands: [Average.self, StandardDeviation.self, Quantiles.self])
+            abstract: "Calculate descriptive statistics.")
     }
 }
 
diff --git a/Package.swift b/Package.swift
index a8caf6ccb..a29fe2a84 100644
--- a/Package.swift
+++ b/Package.swift
@@ -22,8 +22,14 @@ var package = Package(
     dependencies: [],
     targets: [
         .target(
-            name: "ArgumentParser",
+            name: "_CRuntime",
             dependencies: []),
+        .target(
+            name: "_Runtime",
+            dependencies: ["_CRuntime"]),
+        .target(
+            name: "ArgumentParser",
+            dependencies: ["_Runtime"]),
         .target(
             name: "ArgumentParserTestHelpers",
             dependencies: ["ArgumentParser"]),
diff --git a/Sources/ArgumentParser/Completions/BashCompletionsGenerator.swift b/Sources/ArgumentParser/Completions/BashCompletionsGenerator.swift
index 41516c6cc..0a9359b36 100644
--- a/Sources/ArgumentParser/Completions/BashCompletionsGenerator.swift
+++ b/Sources/ArgumentParser/Completions/BashCompletionsGenerator.swift
@@ -34,7 +34,7 @@ struct BashCompletionsGenerator {
     let subcommandArgument = isRootCommand ? "2" : "$(($1+1))"
   
     // Include 'help' in the list of subcommands for the root command.
-    var subcommands = type.configuration.subcommands
+    var subcommands = type.subcommands
     if !subcommands.isEmpty && isRootCommand {
       subcommands.append(HelpCommand.self)
     }
diff --git a/Sources/ArgumentParser/Completions/FishCompletionsGenerator.swift b/Sources/ArgumentParser/Completions/FishCompletionsGenerator.swift
index 05a638916..922882dab 100644
--- a/Sources/ArgumentParser/Completions/FishCompletionsGenerator.swift
+++ b/Sources/ArgumentParser/Completions/FishCompletionsGenerator.swift
@@ -29,7 +29,7 @@ struct FishCompletionsGenerator {
     let type = commands.last!
     let isRootCommand = commands.count == 1
     let programName = commandChain[0]
-    var subcommands = type.configuration.subcommands
+    var subcommands = type.subcommands
 
     if !subcommands.isEmpty {
       if isRootCommand {
diff --git a/Sources/ArgumentParser/Completions/ZshCompletionsGenerator.swift b/Sources/ArgumentParser/Completions/ZshCompletionsGenerator.swift
index ee4c178ad..bd28c2d08 100644
--- a/Sources/ArgumentParser/Completions/ZshCompletionsGenerator.swift
+++ b/Sources/ArgumentParser/Completions/ZshCompletionsGenerator.swift
@@ -37,7 +37,7 @@ struct ZshCompletionsGenerator {
     
     var args = generateCompletionArguments(commands)
     
-    var subcommands = type.configuration.subcommands
+    var subcommands = type.subcommands
     var subcommandHandler = ""
     if !subcommands.isEmpty {
       args.append("'(-): :->command'")
diff --git a/Sources/ArgumentParser/Parsable Types/CommandConfiguration.swift b/Sources/ArgumentParser/Parsable Types/CommandConfiguration.swift
index ea3b8b3af..5dcbb1c78 100644
--- a/Sources/ArgumentParser/Parsable Types/CommandConfiguration.swift	
+++ b/Sources/ArgumentParser/Parsable Types/CommandConfiguration.swift	
@@ -39,7 +39,10 @@ public struct CommandConfiguration {
   public var shouldDisplay: Bool
   
   /// An array of the types that define subcommands for this command.
-  public var subcommands: [ParsableCommand.Type]
+  ///
+  /// If `nil`, the argument parser will automatically discover nested
+  /// types who conform to `ParsableCommand` and use them as subcommands.
+  public var subcommands: [ParsableCommand.Type]?
   
   /// The default command type to run if no subcommand is given.
   public var defaultSubcommand: ParsableCommand.Type?
@@ -74,7 +77,7 @@ public struct CommandConfiguration {
     discussion: String = "",
     version: String = "",
     shouldDisplay: Bool = true,
-    subcommands: [ParsableCommand.Type] = [],
+    subcommands: [ParsableCommand.Type]? = nil,
     defaultSubcommand: ParsableCommand.Type? = nil,
     helpNames: NameSpecification? = nil
   ) {
@@ -97,7 +100,7 @@ public struct CommandConfiguration {
     discussion: String = "",
     version: String = "",
     shouldDisplay: Bool = true,
-    subcommands: [ParsableCommand.Type] = [],
+    subcommands: [ParsableCommand.Type]? = nil,
     defaultSubcommand: ParsableCommand.Type? = nil,
     helpNames: NameSpecification? = nil
   ) {
diff --git a/Sources/ArgumentParser/Parsable Types/ParsableCommand.swift b/Sources/ArgumentParser/Parsable Types/ParsableCommand.swift
index 1042105de..75a49d9c9 100644
--- a/Sources/ArgumentParser/Parsable Types/ParsableCommand.swift	
+++ b/Sources/ArgumentParser/Parsable Types/ParsableCommand.swift	
@@ -44,6 +44,10 @@ extension ParsableCommand {
   public mutating func run() throws {
     throw CleanExit.helpRequest(self)
   }
+  
+  static var subcommands: [ParsableCommand.Type] {
+    configuration.subcommands ?? discoverSubcommands(for: Self.self)
+  }
 }
 
 // MARK: - API
diff --git a/Sources/ArgumentParser/Usage/HelpGenerator.swift b/Sources/ArgumentParser/Usage/HelpGenerator.swift
index 16d997a89..593bfbac5 100644
--- a/Sources/ArgumentParser/Usage/HelpGenerator.swift
+++ b/Sources/ArgumentParser/Usage/HelpGenerator.swift
@@ -117,7 +117,7 @@ internal struct HelpGenerator {
     }
 
     var usageString = UsageGenerator(toolName: toolName, definition: [currentArgSet]).synopsis
-    if !currentCommand.configuration.subcommands.isEmpty {
+    if !currentCommand.subcommands.isEmpty {
       if usageString.last != " " { usageString += " " }
       usageString += "<subcommand>"
     }
@@ -202,9 +202,10 @@ internal struct HelpGenerator {
       }
     }
     
-    let configuration = commandStack.last!.configuration
+    let command = commandStack.last!
+    let configuration = command.configuration
     let subcommandElements: [Section.Element] =
-      configuration.subcommands.compactMap { command in
+      command.subcommands.compactMap { command in
         guard command.configuration.shouldDisplay else { return nil }
         var label = command._commandName
         if command == configuration.defaultSubcommand {
diff --git a/Sources/ArgumentParser/Utilities/SubcommandDiscovery.swift b/Sources/ArgumentParser/Utilities/SubcommandDiscovery.swift
new file mode 100644
index 000000000..b317bb8fb
--- /dev/null
+++ b/Sources/ArgumentParser/Utilities/SubcommandDiscovery.swift
@@ -0,0 +1,106 @@
+//===----------------------------------------------------------*- swift -*-===//
+//
+// This source file is part of the Swift Argument Parser open source project
+//
+// Copyright (c) 2021 Apple Inc. and the Swift project authors
+// Licensed under Apache License v2.0 with Runtime Library Exception
+//
+// See https://swift.org/LICENSE.txt for license information
+//
+//===----------------------------------------------------------------------===//
+
+import _Runtime
+@_implementationOnly import Foundation
+
+let subcommandLock = NSLock()
+var discoveredSubcommands: [UnsafeRawPointer: [ParsableCommand.Type]] = [:]
+
+// Use runtime metadata information to find nested subcommands automatically.
+// When getting the subcommands for a ParsableCommand, we look at all types who
+// conform to ParsableCommand within the same module. If we find one who
+// is nested in the base command that we're looking at now, we add it as a
+// subcommand.
+//
+//      struct Base: ParsableCommand {}
+//
+//      extension Base {
+//        // This is considered an automatic subcommand!
+//        struct Sub: ParsableCommand {}
+//      }
+//
+func discoverSubcommands(for type: Any.Type) -> [ParsableCommand.Type] {
+  // Make sure that only classes, structs, and enums are checked for.
+  guard let selfMetadata = metadata(for: type),
+        selfMetadata.kind != .existential else {
+    return []
+  }
+  
+  subcommandLock.lock()
+  
+  defer {
+    subcommandLock.unlock()
+  }
+  
+  guard !discoveredSubcommands.keys.contains(selfMetadata.pointer) else {
+    return discoveredSubcommands[selfMetadata.pointer]!
+  }
+  
+  let module = getModuleDescriptor(from: selfMetadata.descriptor)
+  
+  let parsableCommand: ContextDescriptor
+  
+  // If the swift_getExistentialTypeConstraints function is available, use that.
+  // Otherwise, fallback to using an earlier existential metadata layout.
+  if #available(macOS 9999, iOS 9999, watchOS 9999, tvOS 9999, *) {
+    // FIXME: Implement this function
+    fatalError("swift_getExistentialTypeConstraints not implemented")
+  } else {
+    let parsableCommandMetadata = metadata(
+      for: ParsableCommand.self
+    ) as! ExistentialMetadata
+    
+    parsableCommand = parsableCommandMetadata.protocols[0]
+  }
+  
+  // Grab all of the conformances to ParsableCommand in the same module that
+  // this ParsableCommand was defined in.
+  let conformances = _Runtime.getConformances(for: parsableCommand, in: module)
+  
+  // FIXME: Maybe we want to reserve some initial space here?
+  var subcommands: [ParsableCommand.Type] = []
+  
+  for conformance in conformances {
+    // If we don't have a context descriptor, then an ObjC class somehow
+    // conformed to a Swift protocol (not sure that's possible).
+    guard let descriptor = conformance.contextDescriptor else {
+      continue
+    }
+    
+    // This is okay because modules can't conform to protocols, so the type
+    // being referenced here is at least a child deep in the declaration context
+    // tree.
+    let parent = descriptor.parent!
+    
+    // We're only interested in conformances where the parent is ourselves
+    // (the parent ParsableCommand).
+    guard parent == selfMetadata.descriptor else {
+      continue
+    }
+    
+    // If a subcommand is generic, we can't add it as a default because we have
+    // no idea what type substitution they want for the generic parameter.
+    guard !descriptor.flags.isGeneric else {
+      continue
+    }
+    
+    // We found a subcommand! Use the access function to get the metadata for
+    // it and add it to the list!
+    let subcommand = descriptor.accessor() as! ParsableCommand.Type
+    subcommands.append(subcommand)
+  }
+  
+  // Remember to cache the results!
+  discoveredSubcommands[selfMetadata.pointer] = subcommands
+  
+  return subcommands
+}
diff --git a/Sources/ArgumentParser/Utilities/Tree.swift b/Sources/ArgumentParser/Utilities/Tree.swift
index fe40fc0a0..da0964ea6 100644
--- a/Sources/ArgumentParser/Utilities/Tree.swift
+++ b/Sources/ArgumentParser/Utilities/Tree.swift
@@ -90,7 +90,7 @@ extension Tree where Element == ParsableCommand.Type {
   
   convenience init(root command: ParsableCommand.Type) throws {
     self.init(command)
-    for subcommand in command.configuration.subcommands {
+    for subcommand in command.subcommands {
       if subcommand == command {
         throw InitializationError.recursiveSubcommand(subcommand)
       }
diff --git a/Sources/_CRuntime/ImageInspection.c b/Sources/_CRuntime/ImageInspection.c
new file mode 100644
index 000000000..348b0c275
--- /dev/null
+++ b/Sources/_CRuntime/ImageInspection.c
@@ -0,0 +1,68 @@
+//===--------------------------------------------------------------*- C -*-===//
+//
+// This source file is part of the Swift Argument Parser open source project
+//
+// Copyright (c) 2021 Apple Inc. and the Swift project authors
+// Licensed under Apache License v2.0 with Runtime Library Exception
+//
+// See https://swift.org/LICENSE.txt for license information
+//
+//===----------------------------------------------------------------------===//
+
+#include "ImageInspection.h"
+
+//===----------------------------------------------------------------------===//
+// MachO Image Inspection
+//===----------------------------------------------------------------------===//
+
+#if defined(__MACH__)
+
+#include <mach-o/dyld.h>
+
+void _loadImageCallback(const struct mach_header *header, intptr_t size) {
+  lookupSection(header, "__TEXT", "__swift5_proto",
+                registerProtocolConformances);
+}
+
+__attribute__((__constructor__))
+void loadImages() {
+  _dyld_register_func_for_add_image(_loadImageCallback);
+}
+
+#endif // defined(__MACH__)
+
+//===----------------------------------------------------------------------===//
+// ELF Image Inspection
+//===----------------------------------------------------------------------===//
+
+#if defined(__ELF__)
+
+#define SWIFT_REGISTER_SECTION(name, handle) \
+  handle(&__start_##name, &__stop_##name - &__start_##name);
+
+__attribute__((__constructor__))
+void loadImages() {
+  SWIFT_REGISTER_SECTION(swift5_protocol_conformances,
+                         registerProtocolConformances)
+}
+
+#undef SWIFT_REGISTER_SECTION
+
+#endif // defined(__ELF__)
+
+//===----------------------------------------------------------------------===//
+// COFF Image Inspection
+//===----------------------------------------------------------------------===//
+
+#if !defined(__MACH__) && !defined(__ELF__)
+
+#define SWIFT_REGISTER_SECTION(name, handle) \
+  handle((const char *)&__start_##name, &__stop_##name - &__start_##name);
+
+void loadImages() {
+  SWIFT_REGISTER_SECTION(sw5prtc, registerProtocolConformances)
+}
+
+#undef SWIFT_REGISTER_SECTION
+
+#endif // !defined(__MACH__) && !defined(__ELF__)
diff --git a/Sources/_CRuntime/MetadataViews.c b/Sources/_CRuntime/MetadataViews.c
new file mode 100644
index 000000000..68e3fb566
--- /dev/null
+++ b/Sources/_CRuntime/MetadataViews.c
@@ -0,0 +1,12 @@
+//===--------------------------------------------------------------*- C -*-===//
+//
+// This source file is part of the Swift Argument Parser open source project
+//
+// Copyright (c) 2021 Apple Inc. and the Swift project authors
+// Licensed under Apache License v2.0 with Runtime Library Exception
+//
+// See https://swift.org/LICENSE.txt for license information
+//
+//===----------------------------------------------------------------------===//
+
+#include "MetadataViews.h"
diff --git a/Sources/_CRuntime/PtrauthStrip.c b/Sources/_CRuntime/PtrauthStrip.c
new file mode 100644
index 000000000..682fc1532
--- /dev/null
+++ b/Sources/_CRuntime/PtrauthStrip.c
@@ -0,0 +1,21 @@
+//===--------------------------------------------------------------*- C -*-===//
+//
+// This source file is part of the Swift Argument Parser open source project
+//
+// Copyright (c) 2021 Apple Inc. and the Swift project authors
+// Licensed under Apache License v2.0 with Runtime Library Exception
+//
+// See https://swift.org/LICENSE.txt for license information
+//
+//===----------------------------------------------------------------------===//
+
+#include "PtrauthStrip.h"
+
+#if defined(__arm64e__)
+#include <ptrauth.h>
+
+const void *__ptrauth_strip_asda(const void *pointer) {
+  return ptrauth_strip(pointer, ptrauth_key_asda);
+}
+
+#endif
diff --git a/Sources/_CRuntime/include/ImageInspection.h b/Sources/_CRuntime/include/ImageInspection.h
new file mode 100644
index 000000000..8fc9e6481
--- /dev/null
+++ b/Sources/_CRuntime/include/ImageInspection.h
@@ -0,0 +1,115 @@
+//===--------------------------------------------------------------*- C -*-===//
+//
+// This source file is part of the Swift Argument Parser open source project
+//
+// Copyright (c) 2021 Apple Inc. and the Swift project authors
+// Licensed under Apache License v2.0 with Runtime Library Exception
+//
+// See https://swift.org/LICENSE.txt for license information
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef IMAGE_INSPECTION_H
+#define IMAGE_INSPECTION_H
+
+#include <stddef.h>
+
+extern void registerProtocolConformances(const char *section, size_t size);
+
+void loadImages();
+
+//===----------------------------------------------------------------------===//
+// MachO Image Inspection
+//===----------------------------------------------------------------------===//
+
+#if defined(__MACH__)
+
+#include <mach-o/dyld.h>
+
+extern void lookupSection(const struct mach_header *header, const char *segment,
+                          const char *section,
+                          void (*registerFunc)(const char *, size_t));
+
+#endif // defined(__MACH__)
+
+//===----------------------------------------------------------------------===//
+// ELF Image Inspection
+//===----------------------------------------------------------------------===//
+
+#if defined(__ELF__)
+
+// Create an empty section here so that we can get legitimate pointers to the
+// actual start and stop of a specific section.
+
+#define DECLARE_SWIFT_SECTION(name) \
+  __asm__("\t.section " #name ", \"a\"\n"); \
+  __attribute__((__visibility__("hidden"), __aligned__(1))) extern const char __start_##name; \
+  __attribute__((__visibility__("hidden"), __aligned__(1))) extern const char __stop_##name;
+
+#if defined(__cplusplus)
+extern "C" {
+#endif
+
+DECLARE_SWIFT_SECTION(swift5_protocol_conformances)
+
+#if defined(__cplusplus)
+} // extern "C"
+#endif
+
+#undef DECLARE_SWIFT_SECTION
+
+#endif // defined(__ELF__)
+
+//===----------------------------------------------------------------------===//
+// COFF Image Inspection
+//===----------------------------------------------------------------------===//
+
+#if !defined(__MACH__) && !defined(__ELF__)
+
+#include "stdint.h"
+
+#define PASTE_EXPANDED(a, b) a##b
+#define PASTE(a, b) PASTE_EXPANDED(a, b)
+
+#define STRING_EXPANDED(string) #string
+#define STRING(string) STRING_EXPANDED(string)
+
+#define C_LABEL(name) PASTE(__USER_LABEL_PREFIX__, name)
+
+#define PRAGMA(pragma) _Pragma(#pragma)
+
+#define DECLARE_SWIFT_SECTION(name) \
+  PRAGMA(section("." #name "$A", long, read)) \
+  __declspec(allocate("." #name "$A")) \
+  __declspec(align(1)) \
+  static uintptr_t __start_##name = 0; \
+                                      \
+  PRAGMA(section("." #name "$C", long, read)) \
+  __declspec(allocate("." #name "$C")) \
+  __declspec(align(1)) \
+  static uintptr_t __stop_##name = 0;
+  
+#if defined(__cplusplus)
+extern "C" {
+#endif
+
+DECLARE_SWIFT_SECTION(sw5prtc)
+
+#if defined(__cplusplus)
+}
+#endif
+
+#undef DECLARE_SWIFT_SECTION
+
+#pragma section(".CRT$XCIS", long, read)
+
+__declspec(allocate(".CRT$XCIS"))
+#if defined(__cplusplus)
+extern "C"
+#endif
+void (*pLoadImages)(void) = &loadImages;
+#pragma comment(linker, "/include:" STRING(C_LABEL(pLoadImages)))
+
+#endif // !defined(__MACH__) && !defined(__ELF__)
+
+#endif /* IMAGE_INSPECTION_H */
diff --git a/Sources/_CRuntime/include/MetadataViews.h b/Sources/_CRuntime/include/MetadataViews.h
new file mode 100644
index 000000000..6e3e4da16
--- /dev/null
+++ b/Sources/_CRuntime/include/MetadataViews.h
@@ -0,0 +1,84 @@
+//===--------------------------------------------------------------*- C -*-===//
+//
+// This source file is part of the Swift Argument Parser open source project
+//
+// Copyright (c) 2021 Apple Inc. and the Swift project authors
+// Licensed under Apache License v2.0 with Runtime Library Exception
+//
+// See https://swift.org/LICENSE.txt for license information
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef METADATA_VIEWS_H
+#define METADATA_VIEWS_H
+
+#include "stdint.h"
+
+// FIXME: Currently, the ClangImporter does not import types who have ptrauth
+// decorators on member pointer types. This means that we could get rid of the
+// whole ptrauth ceremony in Swift by stripping the asda portion and actually
+// sign using the designated type descriptor key.
+
+struct ClassMetadata {
+  intptr_t kind;
+  const void *superclass;
+  uint32_t flags;
+  uint32_t instanceAddressPoint;
+  uint32_t instanceSize;
+  uint16_t instanceAlignmentMask;
+  uint16_t runtimeReserved;
+  uint32_t classSize;
+  uint32_t classAddressPoint;
+  const void *descriptor;
+};
+
+struct ClassMetadataObjC {
+  intptr_t kind;
+  const void *superclass;
+  intptr_t cacheData[2];
+  const void *data;
+  uint32_t flags;
+  uint32_t instanceAddressPoint;
+  uint32_t instanceSize;
+  uint16_t instanceAlignmentMask;
+  uint16_t runtimeReserved;
+  uint32_t classSize;
+  uint32_t classAddressPoint;
+  const void *descriptor;
+};
+
+struct ConformanceDescriptor {
+  int32_t protocol;
+  int32_t typeReference;
+  int32_t witnessTablePattern;
+  uint32_t flags;
+};
+
+struct ContextDescriptor {
+  uint32_t flags;
+  int32_t parent;
+};
+
+struct EnumMetadata {
+  intptr_t kind;
+  const void *descriptor;
+};
+
+struct ExistentialMetadata {
+  intptr_t kind;
+  uint32_t flags;
+  uint32_t numProtocols;
+};
+
+struct StructMetadata {
+  intptr_t kind;
+  const void *descriptor;
+};
+
+struct TypeContextDescriptor {
+  struct ContextDescriptor base;
+  int32_t name;
+  int32_t accessor;
+};
+
+#endif /* METADATA_VIEWS_H */
diff --git a/Sources/_CRuntime/include/PtrauthStrip.h b/Sources/_CRuntime/include/PtrauthStrip.h
new file mode 100644
index 000000000..5498dfadc
--- /dev/null
+++ b/Sources/_CRuntime/include/PtrauthStrip.h
@@ -0,0 +1,19 @@
+//===--------------------------------------------------------------*- C -*-===//
+//
+// This source file is part of the Swift Argument Parser open source project
+//
+// Copyright (c) 2021 Apple Inc. and the Swift project authors
+// Licensed under Apache License v2.0 with Runtime Library Exception
+//
+// See https://swift.org/LICENSE.txt for license information
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef PTRAUTH_H
+#define PTRAUTH_H
+
+#if defined(__arm64e__)
+const void *__ptrauth_strip_asda(const void *pointer);
+#endif
+
+#endif /* PTRAUTH_H */
diff --git a/Sources/_Runtime/Metadata/ClassMetadata.swift b/Sources/_Runtime/Metadata/ClassMetadata.swift
new file mode 100644
index 000000000..d0d4837cf
--- /dev/null
+++ b/Sources/_Runtime/Metadata/ClassMetadata.swift
@@ -0,0 +1,35 @@
+//===----------------------------------------------------------*- swift -*-===//
+//
+// This source file is part of the Swift Argument Parser open source project
+//
+// Copyright (c) 2021 Apple Inc. and the Swift project authors
+// Licensed under Apache License v2.0 with Runtime Library Exception
+//
+// See https://swift.org/LICENSE.txt for license information
+//
+//===----------------------------------------------------------------------===//
+
+import _CRuntime
+
+public struct ClassMetadata: Metadata, PointerView {
+  // The ObjC specific properties of class metadata are always present on
+  // ObjC interopt enabled devices or platforms pre Swift 5.4. In 5.4,
+  // those were removed on platforms who do not provide ObjectiveC.
+  #if canImport(ObjectiveC) || swift(<5.4)
+  typealias View = _CRuntime.ClassMetadataObjC
+  #else
+  typealias View = _CRuntime.ClassMetadata
+  #endif
+
+  public let pointer: UnsafeRawPointer
+
+  var descriptor: ContextDescriptor {
+    // Type descriptors are signed on arm64e using pointer authentication.
+    #if _ptrauth(_arm64e)
+    let signed = __ptrauth_strip_asda(view.descriptor)!
+    return ContextDescriptor(pointer: signed)
+    #else
+    return ContextDescriptor(pointer: view.descriptor)
+    #endif
+  }
+}
diff --git a/Sources/_Runtime/Metadata/ConformanceDescriptor.swift b/Sources/_Runtime/Metadata/ConformanceDescriptor.swift
new file mode 100644
index 000000000..786cf36fc
--- /dev/null
+++ b/Sources/_Runtime/Metadata/ConformanceDescriptor.swift
@@ -0,0 +1,68 @@
+//===----------------------------------------------------------*- swift -*-===//
+//
+// This source file is part of the Swift Argument Parser open source project
+//
+// Copyright (c) 2021 Apple Inc. and the Swift project authors
+// Licensed under Apache License v2.0 with Runtime Library Exception
+//
+// See https://swift.org/LICENSE.txt for license information
+//
+//===----------------------------------------------------------------------===//
+
+import _CRuntime
+
+public struct ConformanceDescriptor: PointerView {
+  typealias View = _CRuntime.ConformanceDescriptor
+  
+  let pointer: UnsafeRawPointer
+  
+  public var `protocol`: ContextDescriptor {
+    let _protocol = RelativeIndirectablePointer<_CRuntime.ContextDescriptor>(
+      offset: view.protocol
+    )
+    
+    return ContextDescriptor(pointer: _protocol.address(from: pointer))
+  }
+  
+  public var contextDescriptor: ContextDescriptor? {
+    let start = pointer + MemoryLayout<Int32>.size
+    let offset = start.load(as: Int32.self)
+    let address = start + Int(offset)
+    let _flags = Flags(value: view.flags)
+    
+    switch _flags.typeReferenceKind {
+    case .directTypeDescriptor:
+      return ContextDescriptor(pointer: address)
+    case .indirectTypeDescriptor:
+      let indirect = address.load(as: ContextDescriptor.self)
+      return indirect
+    default:
+      return nil
+    }
+  }
+}
+
+extension ConformanceDescriptor {
+  public struct Flags {
+    let value: UInt32
+    
+    var typeReferenceKind: TypeReferenceKind {
+      TypeReferenceKind(UInt16(value & (0x7 << 3)) >> 3)
+    }
+  }
+}
+
+enum TypeReferenceKind: UInt16 {
+  case directTypeDescriptor = 0x0
+  case indirectTypeDescriptor = 0x1
+  case other = 0xFFFF
+  
+  init(_ int: UInt16) {
+    guard let kind = TypeReferenceKind(rawValue: int) else {
+      self = .other
+      return
+    }
+    
+    self = kind
+  }
+}
diff --git a/Sources/_Runtime/Metadata/ContextDescriptor.swift b/Sources/_Runtime/Metadata/ContextDescriptor.swift
new file mode 100644
index 000000000..d34e7251e
--- /dev/null
+++ b/Sources/_Runtime/Metadata/ContextDescriptor.swift
@@ -0,0 +1,86 @@
+//===----------------------------------------------------------*- swift -*-===//
+//
+// This source file is part of the Swift Argument Parser open source project
+//
+// Copyright (c) 2021 Apple Inc. and the Swift project authors
+// Licensed under Apache License v2.0 with Runtime Library Exception
+//
+// See https://swift.org/LICENSE.txt for license information
+//
+//===----------------------------------------------------------------------===//
+
+import _CRuntime
+
+// We really don't care about any of the various context descriptor properties,
+// thus this design is a single abstraction for all context descriptors.
+
+public struct ContextDescriptor: PointerView {
+  typealias View = _CRuntime.ContextDescriptor
+
+  let pointer: UnsafeRawPointer
+
+  public var flags: Flags {
+    Flags(value: view.flags)
+  }
+
+  public var parent: ContextDescriptor? {
+    let _parent = RelativeIndirectablePointer<_CRuntime.ContextDescriptor>(
+      offset: view.parent
+    )
+    
+    guard _parent.offset != 0 else {
+      return nil
+    }
+
+    let start = pointer + MemoryLayout<Int32>.size
+    let address = _parent.address(from: start)
+    return ContextDescriptor(pointer: address)
+  }
+
+  public var accessor: MetadataAccessFunction {
+    switch flags.kind {
+    case .class, .struct, .enum:
+      let typeDescriptor = pointer.load(as: _CRuntime.TypeContextDescriptor.self)
+      let start = pointer + MemoryLayout<Int32>.size * 3
+      let _accessor = RelativeDirectPointer<Void>(
+        offset: typeDescriptor.accessor
+      )
+      let address = _accessor.address(from: start)
+      return MetadataAccessFunction(pointer: address)
+    default:
+      fatalError("Context descriptor kind: \(flags.kind), has no type accessor")
+    }
+  }
+}
+
+extension ContextDescriptor: Equatable {}
+extension ContextDescriptor: Hashable {}
+
+extension ContextDescriptor {
+  public struct Flags {
+    let value: UInt32
+
+    var kind: Kind {
+      let raw = UInt8(value & 0x1F)
+
+      guard let kind = Kind(rawValue: raw) else {
+        return .other
+      }
+
+      return kind
+    }
+
+    public var isGeneric: Bool {
+      value & 0x80 != 0
+    }
+  }
+
+  enum Kind: UInt8 {
+    case module = 0x0
+    case `protocol` = 0x3
+    case `class` = 0x11
+    case `struct` = 0x12
+    case `enum` = 0x13
+    case other = 0xFF
+  }
+}
diff --git a/Sources/_Runtime/Metadata/EnumMetadata.swift b/Sources/_Runtime/Metadata/EnumMetadata.swift
new file mode 100644
index 000000000..067209591
--- /dev/null
+++ b/Sources/_Runtime/Metadata/EnumMetadata.swift
@@ -0,0 +1,28 @@
+//===----------------------------------------------------------*- swift -*-===//
+//
+// This source file is part of the Swift Argument Parser open source project
+//
+// Copyright (c) 2021 Apple Inc. and the Swift project authors
+// Licensed under Apache License v2.0 with Runtime Library Exception
+//
+// See https://swift.org/LICENSE.txt for license information
+//
+//===----------------------------------------------------------------------===//
+
+import _CRuntime
+
+public struct EnumMetadata: Metadata, PointerView {
+  typealias View = _CRuntime.EnumMetadata
+
+  public let pointer: UnsafeRawPointer
+
+  var descriptor: ContextDescriptor {
+    // Type descriptors are signed on arm64e using pointer authentication.
+    #if _ptrauth(_arm64e)
+    let signed = __ptrauth_strip_asda(view.descriptor)!
+    return ContextDescriptor(pointer: signed)
+    #else
+    return ContextDescriptor(pointer: view.descriptor)
+    #endif
+  }
+}
diff --git a/Sources/_Runtime/Metadata/ExistentialMetadata.swift b/Sources/_Runtime/Metadata/ExistentialMetadata.swift
new file mode 100644
index 000000000..a126bc8b9
--- /dev/null
+++ b/Sources/_Runtime/Metadata/ExistentialMetadata.swift
@@ -0,0 +1,46 @@
+//===----------------------------------------------------------*- swift -*-===//
+//
+// This source file is part of the Swift Argument Parser open source project
+//
+// Copyright (c) 2021 Apple Inc. and the Swift project authors
+// Licensed under Apache License v2.0 with Runtime Library Exception
+//
+// See https://swift.org/LICENSE.txt for license information
+//
+//===----------------------------------------------------------------------===//
+
+import _CRuntime
+
+public struct ExistentialMetadata: Metadata, PointerView {
+  typealias View = _CRuntime.ExistentialMetadata
+
+  public let pointer: UnsafeRawPointer
+
+  var flags: ExistentialMetadata.Flags {
+    Flags(value: view.flags)
+  }
+  
+  public var protocols: UnsafeBufferPointer<ContextDescriptor> {
+    var start = trailing
+
+    // The first trailing object is the superclass metadata, if there is any.
+    if flags.hasSuperclassConstraint {
+      start += MemoryLayout<Int>.size
+    }
+
+    return UnsafeBufferPointer(
+      start: UnsafePointer<ContextDescriptor>(start._rawValue),
+      count: Int(view.numProtocols)
+    )
+  }
+}
+
+extension ExistentialMetadata {
+  struct Flags {
+    let value: UInt32
+
+    var hasSuperclassConstraint: Bool {
+      value & 0x40000000 != 0
+    }
+  }
+}
diff --git a/Sources/_Runtime/Metadata/Metadata.swift b/Sources/_Runtime/Metadata/Metadata.swift
new file mode 100644
index 000000000..4c779ce73
--- /dev/null
+++ b/Sources/_Runtime/Metadata/Metadata.swift
@@ -0,0 +1,76 @@
+//===----------------------------------------------------------*- swift -*-===//
+//
+// This source file is part of the Swift Argument Parser open source project
+//
+// Copyright (c) 2021 Apple Inc. and the Swift project authors
+// Licensed under Apache License v2.0 with Runtime Library Exception
+//
+// See https://swift.org/LICENSE.txt for license information
+//
+//===----------------------------------------------------------------------===//
+
+public protocol Metadata {
+  var pointer: UnsafeRawPointer { get }
+}
+
+extension Metadata {
+  public var kind: MetadataKind {
+    MetadataKind(pointer)
+  }
+
+  public var descriptor: ContextDescriptor {
+    switch self {
+    case let classMetadata as ClassMetadata:
+      return classMetadata.descriptor
+    case let enumMetadata as EnumMetadata:
+      return enumMetadata.descriptor
+    case let structMetadata as StructMetadata:
+      return structMetadata.descriptor
+    default:
+      fatalError("Metadata kind: \(kind), does not have a context descriptor.")
+    }
+  }
+}
+
+public enum MetadataKind: Int {
+  case `class` = 0
+  case `struct` = 0x200
+  case `enum` = 0x201
+  case optional = 0x202
+  case existential = 0x303
+  case other = 0xFFFF
+}
+
+extension MetadataKind {
+  init(_ ptr: UnsafeRawPointer) {
+    let raw = ptr.load(as: Int.self)
+
+    guard let kind = MetadataKind(rawValue: raw) else {
+      // If we're larger than 2047, then this is a class isa pointer for ObjC,
+      // otherwise we're some other kind of metadata (or unknown) that we don't
+      // care about for autodiscovery.
+      self = raw > 0x7FF ? .class : .other
+      return
+    }
+
+    self = kind
+  }
+}
+
+public func metadata(for type: Any.Type) -> Metadata? {
+  let ptr = unsafeBitCast(type, to: UnsafeRawPointer.self)
+  let kind = MetadataKind(ptr)
+
+  switch kind {
+  case .class:
+    return ClassMetadata(pointer: ptr)
+  case .struct:
+    return StructMetadata(pointer: ptr)
+  case .enum, .optional:
+    return EnumMetadata(pointer: ptr)
+  case .existential:
+    return ExistentialMetadata(pointer: ptr)
+  default:
+    return nil
+  }
+}
diff --git a/Sources/_Runtime/Metadata/MetadataAccessFunction.swift b/Sources/_Runtime/Metadata/MetadataAccessFunction.swift
new file mode 100644
index 000000000..7f3b52db8
--- /dev/null
+++ b/Sources/_Runtime/Metadata/MetadataAccessFunction.swift
@@ -0,0 +1,33 @@
+//===----------------------------------------------------------*- swift -*-===//
+//
+// This source file is part of the Swift Argument Parser open source project
+//
+// Copyright (c) 2021 Apple Inc. and the Swift project authors
+// Licensed under Apache License v2.0 with Runtime Library Exception
+//
+// See https://swift.org/LICENSE.txt for license information
+//
+//===----------------------------------------------------------------------===//
+
+public struct MetadataAccessFunction {
+  let pointer: UnsafeRawPointer
+
+  public func callAsFunction() -> Any.Type {
+    // For the purposes of subcommand autodiscovery, we don't care about types
+    // who are generic or require witness tables, so using the simple access
+    // function is okay because we only ever call it on non-generic types.
+    let fn = unsafeBitCast(
+      pointer,
+      to: (@convention(thin) (Int) -> MetadataResponse).self
+    )
+
+    // We only care about complete blocking metadata, so 0 is correct here.
+    return fn(0).type
+  }
+}
+
+struct MetadataResponse {
+  let type: Any.Type
+
+  let state: Int
+}
diff --git a/Sources/_Runtime/Metadata/StructMetadata.swift b/Sources/_Runtime/Metadata/StructMetadata.swift
new file mode 100644
index 000000000..f2dfd28b4
--- /dev/null
+++ b/Sources/_Runtime/Metadata/StructMetadata.swift
@@ -0,0 +1,28 @@
+//===----------------------------------------------------------*- swift -*-===//
+//
+// This source file is part of the Swift Argument Parser open source project
+//
+// Copyright (c) 2021 Apple Inc. and the Swift project authors
+// Licensed under Apache License v2.0 with Runtime Library Exception
+//
+// See https://swift.org/LICENSE.txt for license information
+//
+//===----------------------------------------------------------------------===//
+
+import _CRuntime
+
+public struct StructMetadata: Metadata, PointerView {
+  typealias View = _CRuntime.StructMetadata
+
+  public let pointer: UnsafeRawPointer
+
+  var descriptor: ContextDescriptor {
+    // Type descriptors are signed on arm64e using pointer authentication.
+    #if _ptrauth(_arm64e)
+    let signed = __ptrauth_strip_asda(view.descriptor)!
+    return ContextDescriptor(pointer: signed)
+    #else
+    return ContextDescriptor(pointer: view.descriptor)
+    #endif
+  }
+}
diff --git a/Sources/_Runtime/Utilities/ImageInspection.swift b/Sources/_Runtime/Utilities/ImageInspection.swift
new file mode 100644
index 000000000..a670a5ac7
--- /dev/null
+++ b/Sources/_Runtime/Utilities/ImageInspection.swift
@@ -0,0 +1,135 @@
+//===----------------------------------------------------------*- swift -*-===//
+//
+// This source file is part of the Swift Argument Parser open source project
+//
+// Copyright (c) 2021 Apple Inc. and the Swift project authors
+// Licensed under Apache License v2.0 with Runtime Library Exception
+//
+// See https://swift.org/LICENSE.txt for license information
+//
+//===----------------------------------------------------------------------===//
+
+import _CRuntime
+@_implementationOnly import Foundation
+
+extension NSLock {
+  func withLock<T>(_ closure: () throws -> T) rethrows -> T {
+    lock()
+    defer { unlock() }
+    return try closure()
+  }
+}
+
+let conformanceLock = NSLock()
+var conformances:
+  [ContextDescriptor: [ContextDescriptor: [ConformanceDescriptor]]] = [:]
+
+@_cdecl("registerProtocolConformances")
+public func registerProtocolConformances(
+  _ section: UnsafeRawPointer,
+  size: Int
+) {
+  // This section is a list of relative pointers.
+  let stride = stride(
+    from: section,
+    to: section + size,
+    by: MemoryLayout<Int32>.stride
+  )
+  
+  for start in stride {
+    let address = start.load(
+      as: RelativeDirectPointer<_CRuntime.ConformanceDescriptor>.self
+    ).address(from: start)
+    let conformance = ConformanceDescriptor(pointer: address)
+    
+    // If we don't have a context descriptor, then the conforming type is an
+    // ObjC class, and we don't care about those.
+    if let descriptor = conformance.contextDescriptor {
+      let module = getModuleDescriptor(from: descriptor)
+      
+      conformanceLock.withLock {
+        conformances[
+          conformance.protocol,
+          default: [:]
+        ][
+          module,
+          default: []
+        ].append(conformance)
+      }
+    }
+  }
+}
+
+// Helper to walk up the context descriptor parent chain to eventually get the
+// module descriptor at the top.
+public func getModuleDescriptor(
+  from descriptor: ContextDescriptor
+) -> ContextDescriptor {
+  var parent = descriptor
+  
+  while let newParent = parent.parent {
+    parent = newParent
+  }
+  
+  return parent
+}
+
+public func getConformances(
+  for protocol: ContextDescriptor,
+  in module: ContextDescriptor
+) -> [ConformanceDescriptor] {
+  return conformanceLock.withLock {
+    guard let protoEntry = conformances[`protocol`] else {
+      return []
+    }
+    
+    guard let moduleEntry = protoEntry[module] else {
+      return []
+    }
+    
+    return moduleEntry
+  }
+}
+
+//===----------------------------------------------------------------------===//
+// MachO Image Inspection
+//===----------------------------------------------------------------------===//
+
+#if canImport(MachO)
+
+import MachO
+
+#if arch(x86_64) || arch(arm64)
+typealias mach_header_platform = mach_header_64
+#else
+typealias mach_header_platform = mach_header
+#endif
+
+@_cdecl("lookupSection")
+public func lookupSection(
+  _ header: UnsafePointer<mach_header>?,
+  segment: UnsafePointer<CChar>?,
+  section: UnsafePointer<CChar>?,
+  do handler: @convention(c) (UnsafeRawPointer, Int) -> ()
+) {
+  guard let header = header else {
+    return
+  }
+  
+  var size: UInt = 0
+  
+  let section = header.withMemoryRebound(
+    to: mach_header_platform.self,
+    capacity: 1
+  ) {
+    getsectiondata($0, segment, section, &size)
+  }
+  
+  guard section != nil else {
+    return
+  }
+  
+  handler(section!, Int(size))
+}
+
+#endif
diff --git a/Sources/_Runtime/Utilities/PointerView.swift b/Sources/_Runtime/Utilities/PointerView.swift
new file mode 100644
index 000000000..53e47d53b
--- /dev/null
+++ b/Sources/_Runtime/Utilities/PointerView.swift
@@ -0,0 +1,26 @@
+//===----------------------------------------------------------*- swift -*-===//
+//
+// This source file is part of the Swift Argument Parser open source project
+//
+// Copyright (c) 2021 Apple Inc. and the Swift project authors
+// Licensed under Apache License v2.0 with Runtime Library Exception
+//
+// See https://swift.org/LICENSE.txt for license information
+//
+//===----------------------------------------------------------------------===//
+
+protocol PointerView {
+  associatedtype View
+
+  var pointer: UnsafeRawPointer { get }
+}
+
+extension PointerView {
+  var view: View {
+    pointer.load(as: View.self)
+  }
+
+  var trailing: UnsafeRawPointer {
+    pointer + MemoryLayout<View>.size
+  }
+}
diff --git a/Sources/_Runtime/Utilities/RelativePointers.swift b/Sources/_Runtime/Utilities/RelativePointers.swift
new file mode 100644
index 000000000..76f0cd384
--- /dev/null
+++ b/Sources/_Runtime/Utilities/RelativePointers.swift
@@ -0,0 +1,34 @@
+//===----------------------------------------------------------*- swift -*-===//
+//
+// This source file is part of the Swift Argument Parser open source project
+//
+// Copyright (c) 2021 Apple Inc. and the Swift project authors
+// Licensed under Apache License v2.0 with Runtime Library Exception
+//
+// See https://swift.org/LICENSE.txt for license information
+//
+//===----------------------------------------------------------------------===//
+
+struct RelativeDirectPointer<Pointee> {
+  let offset: Int32
+
+  func address(from pointer: UnsafeRawPointer) -> UnsafeRawPointer {
+    pointer + Int(offset)
+  }
+}
+
+struct RelativeIndirectablePointer<Pointee> {
+  let offset: Int32
+
+  func address(from pointer: UnsafeRawPointer) -> UnsafeRawPointer {
+    let dest = pointer + Int(offset & ~1)
+
+    // If our low bit is set, then it indicates that we're indirectly pointing
+    // at our desired object. Otherwise, it's directly in front of us.
+    if Int(offset) & 1 == 1 {
+      return dest.load(as: UnsafeRawPointer.self)
+    } else {
+      return dest
+    }
+  }
+}
diff --git a/Tests/ArgumentParserEndToEndTests/DefaultsEndToEndTests.swift b/Tests/ArgumentParserEndToEndTests/DefaultsEndToEndTests.swift
index dd850252f..e450b01ec 100644
--- a/Tests/ArgumentParserEndToEndTests/DefaultsEndToEndTests.swift
+++ b/Tests/ArgumentParserEndToEndTests/DefaultsEndToEndTests.swift
@@ -614,7 +614,6 @@ extension DefaultsEndToEndTests {
 
 fileprivate struct Main: ParsableCommand {
   static var configuration = CommandConfiguration(
-    subcommands: [Sub.self],
     defaultSubcommand: Sub.self
   )
   
diff --git a/Tests/ArgumentParserEndToEndTests/NestedCommandEndToEndTests.swift b/Tests/ArgumentParserEndToEndTests/NestedCommandEndToEndTests.swift
index 1c5c520c5..191f348ae 100644
--- a/Tests/ArgumentParserEndToEndTests/NestedCommandEndToEndTests.swift
+++ b/Tests/ArgumentParserEndToEndTests/NestedCommandEndToEndTests.swift
@@ -19,9 +19,6 @@ final class NestedCommandEndToEndTests: XCTestCase {
 // MARK: Single value String
 
 fileprivate struct Foo: ParsableCommand {
-  static var configuration =
-    CommandConfiguration(subcommands: [Build.self, Package.self])
-
   @Flag(name: .short)
   var verbose: Bool = false
 
@@ -33,9 +30,6 @@ fileprivate struct Foo: ParsableCommand {
   }
 
   struct Package: ParsableCommand {
-    static var configuration =
-      CommandConfiguration(subcommands: [Clean.self, Config.self])
-
     @Flag(name: .short)
     var force: Bool = false
 
@@ -152,10 +146,6 @@ private struct UniqueOptions: ParsableArguments {
 }
 
 private struct Super: ParsableCommand {
-  static var configuration: CommandConfiguration {
-    .init(subcommands: [Sub1.self, Sub2.self])
-  }
-
   @OptionGroup() var options: Options
 
   struct Sub1: ParsableCommand {
diff --git a/Tests/ArgumentParserEndToEndTests/SubcommandEndToEndTests.swift b/Tests/ArgumentParserEndToEndTests/SubcommandEndToEndTests.swift
index ed89a44d3..e15cccb57 100644
--- a/Tests/ArgumentParserEndToEndTests/SubcommandEndToEndTests.swift
+++ b/Tests/ArgumentParserEndToEndTests/SubcommandEndToEndTests.swift
@@ -155,8 +155,7 @@ struct BaseCommand: ParsableCommand {
   static let baseFlagValue = "base"
 
   static var configuration = CommandConfiguration(
-    commandName: "base",
-    subcommands: [SubCommand.self]
+    commandName: "base"
   )
 
   @Option()
@@ -174,8 +173,7 @@ extension BaseCommand {
     static let subFlagValue = "sub"
 
     static var configuration = CommandConfiguration(
-      commandName: "sub",
-      subcommands: [SubSubCommand.self]
+      commandName: "sub"
     )
 
     @Option()
@@ -239,8 +237,7 @@ extension SubcommandEndToEndTests {
 
 private struct A: ParsableCommand {
   static var configuration = CommandConfiguration(
-    version: "1.0.0",
-    subcommands: [HasVersionFlag.self, NoVersionFlag.self])
+    version: "1.0.0")
 
   struct HasVersionFlag: ParsableCommand {
     @Flag var version: Bool = false
@@ -261,3 +258,75 @@ extension SubcommandEndToEndTests {
     }
   }
 }
+
+// MARK: Subcommand Autodiscovery
+
+fileprivate struct Swift: ParsableCommand {
+  // Test Build and Package are treated as automatic subcommands.
+  
+  struct Build: ParsableCommand {
+    // Test that DontBuild is not picked up as a subcommand by explictly using
+    // an empty subcommand array.
+    
+    static var configuration = CommandConfiguration(
+      subcommands: []
+    )
+    
+    struct DontBuild: ParsableCommand {}
+  }
+  
+  struct Package: ParsableCommand {
+    // Test that Init is treated as a subcommand, but Destroy is not.
+    
+    static var configuration = CommandConfiguration(
+      subcommands: [Init.self]
+    )
+    
+    struct Init: ParsableCommand {}
+    
+    struct Destroy: ParsableCommand {}
+  }
+}
+
+extension SubcommandEndToEndTests {
+  func testAutodiscovery() throws {
+    let swiftHelp = Swift.helpMessage()
+    
+    AssertEqualStringsIgnoringTrailingWhitespace("""
+        USAGE: swift <subcommand>
+
+        OPTIONS:
+          -h, --help              Show help information.
+
+        SUBCOMMANDS:
+          package
+          build
+
+          See 'swift help <subcommand>' for detailed help.
+        """, swiftHelp)
+    
+    let buildHelp = Swift.Build.helpMessage()
+    
+    AssertEqualStringsIgnoringTrailingWhitespace("""
+        USAGE: build
+
+        OPTIONS:
+          -h, --help              Show help information.
+
+        """, buildHelp)
+    
+    let packageHelp = Swift.Package.helpMessage()
+    
+    AssertEqualStringsIgnoringTrailingWhitespace("""
+        USAGE: package <subcommand>
+
+        OPTIONS:
+          -h, --help              Show help information.
+
+        SUBCOMMANDS:
+          init
+
+          See 'package help <subcommand>' for detailed help.
+        """, packageHelp)
+  }
+}
diff --git a/Tests/ArgumentParserPackageManagerTests/PackageManager/Config.swift b/Tests/ArgumentParserPackageManagerTests/PackageManager/Config.swift
index 8d19a6d67..6a68e26d8 100644
--- a/Tests/ArgumentParserPackageManagerTests/PackageManager/Config.swift
+++ b/Tests/ArgumentParserPackageManagerTests/PackageManager/Config.swift
@@ -17,9 +17,6 @@ extension Package {
 }
 
 extension Package.Config {
-  public static var configuration = CommandConfiguration(
-    subcommands: [GetMirror.self, SetMirror.self, UnsetMirror.self])
-  
   /// Print mirror configuration for the given package dependency
   struct GetMirror: ParsableCommand {
     @OptionGroup()
diff --git a/Tests/ArgumentParserPackageManagerTests/PackageManager/Options.swift b/Tests/ArgumentParserPackageManagerTests/PackageManager/Options.swift
index ccdbc5a9b..55937777d 100644
--- a/Tests/ArgumentParserPackageManagerTests/PackageManager/Options.swift
+++ b/Tests/ArgumentParserPackageManagerTests/PackageManager/Options.swift
@@ -87,10 +87,7 @@ struct Options: ParsableArguments {
   var swiftCompilerFlags: [String] = []
 }
 
-struct Package: ParsableCommand {
-  static var configuration = CommandConfiguration(
-    subcommands: [Clean.self, Config.self, Describe.self, GenerateXcodeProject.self, Hidden.self])
-}
+struct Package: ParsableCommand {}
 
 extension Package {
   struct Hidden: ParsableCommand {
diff --git a/Tests/ArgumentParserUnitTests/HelpGenerationTests.swift b/Tests/ArgumentParserUnitTests/HelpGenerationTests.swift
index 1334b92b6..12138d054 100644
--- a/Tests/ArgumentParserUnitTests/HelpGenerationTests.swift
+++ b/Tests/ArgumentParserUnitTests/HelpGenerationTests.swift
@@ -264,7 +264,6 @@ extension HelpGenerationTests {
       @Argument
       var argument: String = ""
     }
-    static var configuration = CommandConfiguration(subcommands: [CommandWithVeryLongName.self,ShortCommand.self,AnotherCommandWithVeryLongName.self,AnotherCommand.self])
   }
 
   func testHelpWithSubcommands() {
@@ -512,8 +511,7 @@ extension HelpGenerationTests {
 extension HelpGenerationTests {
   private struct ParserBug: ParsableCommand {
     static let configuration = CommandConfiguration(
-      commandName: "parserBug",
-      subcommands: [Sub.self])
+      commandName: "parserBug")
     
     struct CommonOptions: ParsableCommand {
       @Flag(help: "example flag")