diff --git a/src/xenia/base/delegate.h b/src/xenia/base/delegate.h
index aa0590cd8..8ecc5cf74 100644
--- a/src/xenia/base/delegate.h
+++ b/src/xenia/base/delegate.h
@@ -45,6 +45,33 @@ class Delegate {
   std::vector<Listener> listeners_;
 };
 
+template <>
+class Delegate<void> {
+ public:
+  typedef std::function<void()> Listener;
+
+  void AddListener(Listener const& listener) {
+    std::lock_guard<std::mutex> guard(lock_);
+    listeners_.push_back(listener);
+  }
+
+  void RemoveAllListeners() {
+    std::lock_guard<std::mutex> guard(lock_);
+    listeners_.clear();
+  }
+
+  void operator()() {
+    std::lock_guard<std::mutex> guard(lock_);
+    for (auto& listener : listeners_) {
+      listener();
+    }
+  }
+
+ private:
+  std::mutex lock_;
+  std::vector<Listener> listeners_;
+};
+
 }  // namespace xe
 
 #endif  // XENIA_BASE_DELEGATE_H_
diff --git a/src/xenia/base/socket.h b/src/xenia/base/socket.h
index 85afc0ada..449824bbf 100644
--- a/src/xenia/base/socket.h
+++ b/src/xenia/base/socket.h
@@ -28,7 +28,8 @@ namespace xe {
 // wait handle should be waited on until new data arrives.
 class Socket {
  public:
-  // TODO(benvanik): client socket static Connect method.
+  // Synchronously connects to the given hostname:port.
+  static std::unique_ptr<Socket> Connect(std::string hostname, uint16_t port);
 
   virtual ~Socket() = default;
 
@@ -84,6 +85,12 @@ class Socket {
     auto buffer_list = std::make_pair(buffer.data(), buffer.size());
     return Send(&buffer_list, 1);
   }
+
+  // Asynchronously sends a string buffer.
+  // Returns false if the socket is disconnected or the data cannot be sent.
+  bool Send(const std::string& value) {
+    return Send(value.data(), value.size());
+  }
 };
 
 // Runs a socket server on the specified local port.
diff --git a/src/xenia/base/socket_win.cc b/src/xenia/base/socket_win.cc
index 83efeaf14..a718ed652 100644
--- a/src/xenia/base/socket_win.cc
+++ b/src/xenia/base/socket_win.cc
@@ -36,6 +36,51 @@ class Win32Socket : public Socket {
   Win32Socket() = default;
   ~Win32Socket() override { Close(); }
 
+  bool Connect(std::string hostname, uint16_t port) {
+    addrinfo hints = {0};
+    hints.ai_family = AF_UNSPEC;
+    hints.ai_socktype = SOCK_STREAM;
+    hints.ai_protocol = IPPROTO_TCP;
+
+    // Resolve the server address and port.
+    // May return multiple results, so attempt to connect to an address until
+    // one succeeds.
+    addrinfo* result = nullptr;
+    auto port_string = std::to_string(port);
+    int ret =
+        getaddrinfo(hostname.c_str(), port_string.c_str(), &hints, &result);
+    if (ret != 0) {
+      XELOGE("getaddrinfo failed with error: %d", ret);
+      return false;
+    }
+    SOCKET try_socket = INVALID_SOCKET;
+    for (addrinfo* ptr = result; ptr; ptr = ptr->ai_next) {
+      // Create a SOCKET for connecting to server.
+      try_socket = socket(ptr->ai_family, ptr->ai_socktype, ptr->ai_protocol);
+      if (try_socket == INVALID_SOCKET) {
+        XELOGE("socket failed with error: %ld", WSAGetLastError());
+        freeaddrinfo(result);
+        return false;
+      }
+      // Connect to server.
+      ret = connect(try_socket, ptr->ai_addr, (int)ptr->ai_addrlen);
+      if (ret == SOCKET_ERROR) {
+        closesocket(try_socket);
+        try_socket = INVALID_SOCKET;
+        continue;
+      }
+      break;
+    }
+    freeaddrinfo(result);
+    if (try_socket == INVALID_SOCKET) {
+      XELOGE("Unable to connect to server");
+      return false;
+    }
+
+    // Piggyback to setup the socket.
+    return Accept(try_socket);
+  }
+
   bool Accept(SOCKET socket) {
     std::lock_guard<std::recursive_mutex> lock(mutex_);
 
@@ -142,6 +187,16 @@ class Win32Socket : public Socket {
   std::unique_ptr<xe::threading::Event> event_;
 };
 
+std::unique_ptr<Socket> Socket::Connect(std::string hostname, uint16_t port) {
+  InitializeWinsock();
+
+  auto socket = std::make_unique<Win32Socket>();
+  if (!socket->Connect(std::move(hostname), port)) {
+    return nullptr;
+  }
+  return std::unique_ptr<Socket>(socket.release());
+}
+
 class Win32SocketServer : public SocketServer {
  public:
   Win32SocketServer(
diff --git a/src/xenia/cpu/thread_state.cc b/src/xenia/cpu/thread_state.cc
index 5bc5cc4a0..d0c1f3846 100644
--- a/src/xenia/cpu/thread_state.cc
+++ b/src/xenia/cpu/thread_state.cc
@@ -104,17 +104,9 @@ ThreadState::ThreadState(Processor* processor, uint32_t thread_id,
   // Set initial registers.
   context_->r[1] = stack_base_;
   context_->r[13] = pcr_address_;
-
-  if (processor_->debugger()) {
-    processor_->debugger()->OnThreadCreated(this);
-  }
 }
 
 ThreadState::~ThreadState() {
-  if (processor_->debugger()) {
-    processor_->debugger()->OnThreadDestroyed(this);
-  }
-
   if (backend_data_) {
     processor_->backend()->FreeThreadData(backend_data_);
   }
diff --git a/src/xenia/debug/client/xdp/xdp_client.cc b/src/xenia/debug/client/xdp/xdp_client.cc
new file mode 100644
index 000000000..57a292661
--- /dev/null
+++ b/src/xenia/debug/client/xdp/xdp_client.cc
@@ -0,0 +1,243 @@
+/**
+ ******************************************************************************
+ * Xenia : Xbox 360 Emulator Research Project                                 *
+ ******************************************************************************
+ * Copyright 2015 Ben Vanik. All rights reserved.                             *
+ * Released under the BSD license - see LICENSE in the root for more details. *
+ ******************************************************************************
+ */
+
+#include "xenia/debug/client/xdp/xdp_client.h"
+
+#include "xenia/base/logging.h"
+#include "xenia/debug/debugger.h"
+
+namespace xe {
+namespace debug {
+namespace client {
+namespace xdp {
+
+using namespace xe::debug::proto;
+
+constexpr size_t kReceiveBufferSize = 1 * 1024 * 1024;
+constexpr size_t kTransmitBufferSize = 1 * 1024 * 1024;
+
+XdpClient::XdpClient()
+    : packet_reader_(kReceiveBufferSize), packet_writer_(kTransmitBufferSize) {
+  receive_buffer_.resize(kReceiveBufferSize);
+}
+
+XdpClient::~XdpClient() {
+  socket_->Close();
+  xe::threading::Wait(thread_.get(), true);
+  thread_.reset();
+}
+
+bool XdpClient::Connect(std::string hostname, uint16_t port) {
+  socket_ = Socket::Connect(std::move(hostname), port);
+  if (!socket_) {
+    XELOGE("Unable to connect to remote host");
+    return false;
+  }
+
+  // Create a thread to manage the connection.
+  thread_ = xe::threading::Thread::Create({}, [this]() {
+    // Main loop.
+    bool running = true;
+    while (running) {
+      auto wait_result = xe::threading::Wait(socket_->wait_handle(), true);
+      switch (wait_result) {
+        case xe::threading::WaitResult::kSuccess:
+          // Event (read or close).
+          running = HandleSocketEvent();
+          continue;
+        case xe::threading::WaitResult::kAbandoned:
+        case xe::threading::WaitResult::kFailed:
+          // Error - kill the thread.
+          running = false;
+          continue;
+        default:
+          // Eh. Continue.
+          continue;
+      }
+    }
+
+    // Kill socket (likely already disconnected).
+    socket_.reset();
+  });
+
+  return true;
+}
+
+bool XdpClient::HandleSocketEvent() {
+  if (!socket_->is_connected()) {
+    // Known-disconnected.
+    return false;
+  }
+  // Attempt to read into our buffer.
+  size_t bytes_read =
+      socket_->Receive(receive_buffer_.data(), receive_buffer_.capacity());
+  if (bytes_read == -1) {
+    // Disconnected.
+    return false;
+  } else if (bytes_read == 0) {
+    // No data available. Wait again.
+    return true;
+  }
+
+  // Pass off the command processor to do with it what it wants.
+  if (!ProcessBuffer(receive_buffer_.data(), bytes_read)) {
+    // Error.
+    XELOGE("Error processing incoming XDP command; forcing disconnect");
+    return false;
+  }
+
+  return true;
+}
+
+bool XdpClient::ProcessBuffer(const uint8_t* buffer, size_t buffer_length) {
+  // Grow and append the bytes to the receive buffer.
+  packet_reader_.AppendBuffer(buffer, buffer_length);
+
+  // Process all packets in the buffer.
+  while (true) {
+    auto packet = packet_reader_.Begin();
+    if (!packet) {
+      // Out of packets. Compact any unused space.
+      packet_reader_.Compact();
+      break;
+    }
+
+    // Emit packet.
+    if (!ProcessPacket(packet)) {
+      // Failed to process packet.
+      XELOGE("Failed to process incoming packet");
+      return false;
+    }
+
+    packet_reader_.End();
+  }
+
+  return true;
+}
+
+bool XdpClient::ProcessPacket(const proto::Packet* packet) {
+  // Hold lock during processing.
+  std::lock_guard<std::recursive_mutex> lock(mutex_);
+
+  switch (packet->packet_type) {
+    case PacketType::kGenericResponse: {
+      //
+    } break;
+    case PacketType::kExecutionNotification: {
+      auto body = packet_reader_.Read<ExecutionNotification>();
+      switch (body->current_state) {
+        case ExecutionNotification::State::kStopped: {
+          // body->stop_reason
+          execution_state_ = ExecutionState::kStopped;
+          listener_->OnExecutionStateChanged(execution_state_);
+          BeginUpdateAllState();
+        } break;
+        case ExecutionNotification::State::kRunning: {
+          execution_state_ = ExecutionState::kRunning;
+          listener_->OnExecutionStateChanged(execution_state_);
+        } break;
+        case ExecutionNotification::State::kExited: {
+          execution_state_ = ExecutionState::kExited;
+          listener_->OnExecutionStateChanged(execution_state_);
+          BeginUpdateAllState();
+        } break;
+      }
+    } break;
+    case PacketType::kModuleListResponse: {
+      auto body = packet_reader_.Read<ModuleListResponse>();
+      auto entries = packet_reader_.ReadArray<ModuleListEntry>(body->count);
+      listener_->OnModulesUpdated(entries);
+    } break;
+    case PacketType::kThreadListResponse: {
+      auto body = packet_reader_.Read<ThreadListResponse>();
+      auto entries = packet_reader_.ReadArray<ThreadListEntry>(body->count);
+      listener_->OnThreadsUpdated(entries);
+    } break;
+    default: {
+      XELOGE("Unknown incoming packet type");
+      return false;
+    } break;
+  }
+  return true;
+}
+
+void XdpClient::Flush() {
+  std::lock_guard<std::recursive_mutex> lock(mutex_);
+  if (!packet_writer_.buffer_offset()) {
+    return;
+  }
+  socket_->Send(packet_writer_.buffer(), packet_writer_.buffer_offset());
+  packet_writer_.Reset();
+}
+
+void XdpClient::Continue() {
+  std::lock_guard<std::recursive_mutex> lock(mutex_);
+  packet_writer_.Begin(PacketType::kExecutionRequest);
+  auto body = packet_writer_.Append<ExecutionRequest>();
+  body->action = ExecutionRequest::Action::kContinue;
+  packet_writer_.End();
+  Flush();
+}
+
+void XdpClient::StepOne(uint32_t thread_id) {
+  std::lock_guard<std::recursive_mutex> lock(mutex_);
+  packet_writer_.Begin(PacketType::kExecutionRequest);
+  auto body = packet_writer_.Append<ExecutionRequest>();
+  body->action = ExecutionRequest::Action::kStep;
+  body->step_mode = ExecutionRequest::StepMode::kStepOne;
+  body->thread_id = thread_id;
+  packet_writer_.End();
+  Flush();
+}
+
+void XdpClient::StepTo(uint32_t thread_id, uint32_t target_pc) {
+  std::lock_guard<std::recursive_mutex> lock(mutex_);
+  packet_writer_.Begin(PacketType::kExecutionRequest);
+  auto body = packet_writer_.Append<ExecutionRequest>();
+  body->action = ExecutionRequest::Action::kStep;
+  body->step_mode = ExecutionRequest::StepMode::kStepTo;
+  body->thread_id = thread_id;
+  body->target_pc = target_pc;
+  packet_writer_.End();
+  Flush();
+}
+
+void XdpClient::Interrupt() {
+  std::lock_guard<std::recursive_mutex> lock(mutex_);
+  packet_writer_.Begin(PacketType::kExecutionRequest);
+  auto body = packet_writer_.Append<ExecutionRequest>();
+  body->action = ExecutionRequest::Action::kInterrupt;
+  packet_writer_.End();
+  Flush();
+}
+
+void XdpClient::Exit() {
+  std::lock_guard<std::recursive_mutex> lock(mutex_);
+  packet_writer_.Begin(PacketType::kExecutionRequest);
+  auto body = packet_writer_.Append<ExecutionRequest>();
+  body->action = ExecutionRequest::Action::kExit;
+  packet_writer_.End();
+  Flush();
+}
+
+void XdpClient::BeginUpdateAllState() {
+  std::lock_guard<std::recursive_mutex> lock(mutex_);
+
+  packet_writer_.Begin(PacketType::kModuleListRequest);
+  packet_writer_.End();
+  packet_writer_.Begin(PacketType::kThreadListRequest);
+  packet_writer_.End();
+
+  Flush();
+}
+
+}  // namespace xdp
+}  // namespace client
+}  // namespace debug
+}  // namespace xe
diff --git a/src/xenia/debug/client/xdp/xdp_client.h b/src/xenia/debug/client/xdp/xdp_client.h
new file mode 100644
index 000000000..9d3cbc65a
--- /dev/null
+++ b/src/xenia/debug/client/xdp/xdp_client.h
@@ -0,0 +1,92 @@
+/**
+ ******************************************************************************
+ * Xenia : Xbox 360 Emulator Research Project                                 *
+ ******************************************************************************
+ * Copyright 2015 Ben Vanik. All rights reserved.                             *
+ * Released under the BSD license - see LICENSE in the root for more details. *
+ ******************************************************************************
+ */
+
+#ifndef XENIA_DEBUG_CLIENT_XDP_XDP_CLIENT_H_
+#define XENIA_DEBUG_CLIENT_XDP_XDP_CLIENT_H_
+
+#include <memory>
+#include <mutex>
+
+#include "xenia/base/socket.h"
+#include "xenia/base/threading.h"
+#include "xenia/debug/proto/packet_reader.h"
+#include "xenia/debug/proto/packet_writer.h"
+#include "xenia/debug/proto/xdp_protocol.h"
+
+namespace xe {
+namespace debug {
+namespace client {
+namespace xdp {
+
+using proto::ModuleListEntry;
+using proto::ThreadListEntry;
+
+enum class ExecutionState {
+  kRunning,
+  kStopped,
+  kExited,
+};
+
+// NOTE: all callbacks are issued on the client thread and should be marshalled
+// to the UI thread. All other methods can be called from any thread.
+
+class ClientListener {
+ public:
+  virtual void OnExecutionStateChanged(ExecutionState execution_state) = 0;
+  virtual void OnModulesUpdated(
+      std::vector<const ModuleListEntry*> entries) = 0;
+  virtual void OnThreadsUpdated(
+      std::vector<const ThreadListEntry*> entries) = 0;
+};
+
+class XdpClient {
+ public:
+  XdpClient();
+  ~XdpClient();
+
+  Socket* socket() const { return socket_.get(); }
+  void set_listener(ClientListener* listener) { listener_ = listener; }
+
+  ExecutionState execution_state() const { return execution_state_; }
+
+  bool Connect(std::string hostname, uint16_t port);
+
+  void Continue();
+  void StepOne(uint32_t thread_id);
+  void StepTo(uint32_t thread_id, uint32_t target_pc);
+  void Interrupt();
+  void Exit();
+
+ private:
+  bool HandleSocketEvent();
+  bool ProcessBuffer(const uint8_t* buffer, size_t buffer_length);
+  bool ProcessPacket(const proto::Packet* packet);
+  void Flush();
+
+  void BeginUpdateAllState();
+
+  std::recursive_mutex mutex_;
+  std::unique_ptr<Socket> socket_;
+  std::unique_ptr<xe::threading::Thread> thread_;
+  std::vector<uint8_t> receive_buffer_;
+
+  proto::PacketReader packet_reader_;
+  proto::PacketWriter packet_writer_;
+
+  ClientListener* listener_ = nullptr;
+
+  ExecutionState execution_state_ = ExecutionState::kStopped;
+};
+
+}  // namespace xdp
+}  // namespace client
+}  // namespace debug
+}  // namespace xe
+
+#endif  // XENIA_DEBUG_CLIENT_XDP_XDP_CLIENT_H_
diff --git a/src/xenia/debug/client/xdp/xdp_command_processor.cc b/src/xenia/debug/client/xdp/xdp_command_processor.cc
new file mode 100644
index 000000000..6725a64a7
--- /dev/null
+++ b/src/xenia/debug/client/xdp/xdp_command_processor.cc
@@ -0,0 +1,34 @@
+/**
+ ******************************************************************************
+ * Xenia : Xbox 360 Emulator Research Project                                 *
+ ******************************************************************************
+ * Copyright 2015 Ben Vanik. All rights reserved.                             *
+ * Released under the BSD license - see LICENSE in the root for more details. *
+ ******************************************************************************
+ */
+
+#include "xenia/debug/client/xdp/xdp_command_processor.h"
+
+#include "xenia/base/logging.h"
+#include "xenia/base/string_buffer.h"
+#include "xenia/debug/client/xdp/xdp_client.h"
+
+namespace xe {
+namespace debug {
+namespace client {
+namespace xdp {
+
+using namespace xe::debug::proto;
+
+constexpr size_t kReceiveBufferSize = 1 * 1024 * 1024;
+constexpr size_t kTransmitBufferSize = 1 * 1024 * 1024;
+
+XdpCommandProcessor::XdpCommandProcessor(XdpClient* client)
+    : client_(client),
+      packet_reader_(kReceiveBufferSize),
+      packet_writer_(kTransmitBufferSize) {}
+
+}  // namespace xdp
+}  // namespace client
+}  // namespace debug
+}  // namespace xe
diff --git a/src/xenia/debug/client/xdp/xdp_command_processor.h b/src/xenia/debug/client/xdp/xdp_command_processor.h
new file mode 100644
index 000000000..c7c09bacb
--- /dev/null
+++ b/src/xenia/debug/client/xdp/xdp_command_processor.h
@@ -0,0 +1,46 @@
+/**
+ ******************************************************************************
+ * Xenia : Xbox 360 Emulator Research Project                                 *
+ ******************************************************************************
+ * Copyright 2015 Ben Vanik. All rights reserved.                             *
+ * Released under the BSD license - see LICENSE in the root for more details. *
+ ******************************************************************************
+ */
+
+#ifndef XENIA_DEBUG_CLIENT_XDP_XDP_COMMAND_PROCESSOR_H_
+#define XENIA_DEBUG_CLIENT_XDP_XDP_COMMAND_PROCESSOR_H_
+
+#include <cstdint>
+
+#include "xenia/debug/proto/packet_reader.h"
+#include "xenia/debug/proto/packet_writer.h"
+#include "xenia/debug/proto/xdp_protocol.h"
+
+namespace xe {
+namespace debug {
+namespace client {
+namespace xdp {
+
+class XdpClient;
+
+class XdpCommandProcessor {
+ public:
+  XdpCommandProcessor(XdpClient* client);
+  ~XdpCommandProcessor() = default;
+
+  bool ProcessBuffer(const uint8_t* buffer, size_t buffer_length);
+
+ private:
+  bool ProcessPacket(const proto::Packet* packet);
+
+  void Flush();
+
+  XdpClient* client_ = nullptr;
+};
+
+}  // namespace xdp
+}  // namespace client
+}  // namespace debug
+}  // namespace xe
+
+#endif  // XENIA_DEBUG_CLIENT_XDP_XDP_COMMAND_PROCESSOR_H_
diff --git a/src/xenia/debug/transport.h b/src/xenia/debug/debug_server.h
similarity index 78%
rename from src/xenia/debug/transport.h
rename to src/xenia/debug/debug_server.h
index e4d22542f..07da439eb 100644
--- a/src/xenia/debug/transport.h
+++ b/src/xenia/debug/debug_server.h
@@ -7,8 +7,8 @@
  ******************************************************************************
  */
 
-#ifndef XENIA_DEBUG_TRANSPORT_H_
-#define XENIA_DEBUG_TRANSPORT_H_
+#ifndef XENIA_DEBUG_DEBUG_SERVER_H_
+#define XENIA_DEBUG_DEBUG_SERVER_H_
 
 #include "xenia/cpu/function.h"
 #include "xenia/cpu/processor.h"
@@ -19,25 +19,25 @@ namespace debug {
 
 class Debugger;
 
-class Transport {
+class DebugServer {
  public:
-  virtual ~Transport() = default;
+  virtual ~DebugServer() = default;
 
   Debugger* debugger() const { return debugger_; }
 
   virtual bool Initialize() = 0;
 
-  // break/resume state
-
   // TODO(benvanik): better thread type (XThread?)
   // virtual void OnThreadCreated(ThreadState* thread_state) = 0;
   // virtual void OnThreadDestroyed(ThreadState* thread_state) = 0;
 
+  virtual void OnExecutionContinued() {}
+  virtual void OnExecutionInterrupted() {}
   /*virtual void OnBreakpointHit(xe::cpu::ThreadState* thread_state,
                                Breakpoint* breakpoint) = 0;*/
 
  protected:
-  Transport(Debugger* debugger) : debugger_(debugger) {}
+  DebugServer(Debugger* debugger) : debugger_(debugger) {}
 
   Debugger* debugger_ = nullptr;
 };
@@ -45,4 +45,4 @@ class Transport {
 }  // namespace debug
 }  // namespace xe
 
-#endif  // XENIA_DEBUG_TRANSPORT_H_
+#endif  // XENIA_DEBUG_DEBUG_SERVER_H_
diff --git a/src/xenia/debug/debugger.cc b/src/xenia/debug/debugger.cc
index 54f26b799..6a2bae882 100644
--- a/src/xenia/debug/debugger.cc
+++ b/src/xenia/debug/debugger.cc
@@ -20,7 +20,9 @@
 #include "xenia/cpu/backend/code_cache.h"
 #include "xenia/cpu/function.h"
 #include "xenia/cpu/processor.h"
-#include "xenia/debug/transport/gdb/gdb_transport.h"
+#include "xenia/debug/server/gdb/gdb_server.h"
+#include "xenia/debug/server/mi/mi_server.h"
+#include "xenia/debug/server/xdp/xdp_server.h"
 #include "xenia/emulator.h"
 #include "xenia/kernel/objects/xkernel_module.h"
 #include "xenia/kernel/objects/xmodule.h"
@@ -40,6 +42,8 @@ DEFINE_bool(wait_for_debugger, false,
             "Waits for a debugger to attach before starting the game.");
 DEFINE_bool(exit_with_debugger, true, "Exit whe the debugger disconnects.");
 
+DEFINE_string(debug_server, "xdp", "Debug server protocol [gdb, mi, xdp].");
+
 namespace xe {
 namespace debug {
 
@@ -86,13 +90,24 @@ bool Debugger::StartSession() {
   functions_trace_file_ = ChunkedMappedMemoryWriter::Open(
       functions_trace_path_, 32 * 1024 * 1024, true);
 
-  // Add default transports.
-  auto gdb_transport =
-      std::make_unique<xe::debug::transport::gdb::GdbTransport>(this);
-  if (gdb_transport->Initialize()) {
-    transports_.emplace_back(std::move(gdb_transport));
+  if (FLAGS_debug_server == "gdb") {
+    server_ = std::make_unique<xe::debug::server::gdb::GdbServer>(this);
+    if (!server_->Initialize()) {
+      XELOGE("Unable to initialize GDB debug server");
+      return false;
+    }
+  } else if (FLAGS_debug_server == "gdb") {
+    server_ = std::make_unique<xe::debug::server::mi::MIServer>(this);
+    if (!server_->Initialize()) {
+      XELOGE("Unable to initialize MI debug server");
+      return false;
+    }
   } else {
-    XELOGE("Unable to initialize GDB debugger transport");
+    server_ = std::make_unique<xe::debug::server::xdp::XdpServer>(this);
+    if (!server_->Initialize()) {
+      XELOGE("Unable to initialize XDP debug server");
+      return false;
+    }
   }
 
   return true;
@@ -103,17 +118,24 @@ void Debugger::PreLaunch() {
     // Wait for the first client.
     XELOGI("Waiting for debugger because of --wait_for_debugger...");
     attach_fence_.Wait();
-    XELOGI("Debugger attached, continuing...");
-  }
+    XELOGI("Debugger attached, breaking and waiting for continue...");
 
-  // TODO(benvanik): notify transports?
+    // Start paused.
+    execution_state_ = ExecutionState::kRunning;
+    Interrupt();
+  } else {
+    // Start running.
+    execution_state_ = ExecutionState::kRunning;
+  }
 }
 
 void Debugger::StopSession() {
+  std::lock_guard<std::recursive_mutex> lock(mutex_);
+
   FlushSession();
 
-  // Kill all transports.
-  transports_.clear();
+  // Kill debug server.
+  server_.reset();
 
   functions_file_.reset();
   functions_trace_file_.reset();
@@ -142,6 +164,78 @@ uint8_t* Debugger::AllocateFunctionTraceData(size_t size) {
   return functions_trace_file_->Allocate(size);
 }
 
+int Debugger::AddBreakpoint(Breakpoint* breakpoint) {
+  // Add to breakpoints map.
+  {
+    std::lock_guard<std::recursive_mutex> lock(mutex_);
+    breakpoints_.insert(
+        std::pair<uint32_t, Breakpoint*>(breakpoint->address(), breakpoint));
+  }
+
+  // Find all functions that contain the breakpoint address.
+  auto fns =
+      emulator_->processor()->FindFunctionsWithAddress(breakpoint->address());
+
+  // Add.
+  for (auto fn : fns) {
+    if (fn->AddBreakpoint(breakpoint)) {
+      return 1;
+    }
+  }
+
+  return 0;
+}
+
+int Debugger::RemoveBreakpoint(Breakpoint* breakpoint) {
+  // Remove from breakpoint map.
+  {
+    std::lock_guard<std::recursive_mutex> lock(mutex_);
+    auto range = breakpoints_.equal_range(breakpoint->address());
+    if (range.first == range.second) {
+      return 1;
+    }
+    bool found = false;
+    for (auto it = range.first; it != range.second; ++it) {
+      if (it->second == breakpoint) {
+        breakpoints_.erase(it);
+        found = true;
+        break;
+      }
+    }
+    if (!found) {
+      return 1;
+    }
+  }
+
+  // Find all functions that have the breakpoint set.
+  auto fns =
+      emulator_->processor()->FindFunctionsWithAddress(breakpoint->address());
+
+  // Remove.
+  for (auto fn : fns) {
+    fn->RemoveBreakpoint(breakpoint);
+  }
+
+  return 0;
+}
+
+void Debugger::FindBreakpoints(uint32_t address,
+                               std::vector<Breakpoint*>& out_breakpoints) {
+  std::lock_guard<std::recursive_mutex> lock(mutex_);
+
+  out_breakpoints.clear();
+
+  auto range = breakpoints_.equal_range(address);
+  if (range.first == range.second) {
+    return;
+  }
+
+  for (auto it = range.first; it != range.second; ++it) {
+    Breakpoint* breakpoint = it->second;
+    out_breakpoints.push_back(breakpoint);
+  }
+}
+
 bool Debugger::SuspendAllThreads() {
   auto threads =
       emulator_->kernel_state()->object_table()->GetObjectsByType<XThread>(
@@ -174,83 +268,43 @@ bool Debugger::ResumeAllThreads() {
   return true;
 }
 
-int Debugger::AddBreakpoint(Breakpoint* breakpoint) {
-  // Add to breakpoints map.
-  {
-    std::lock_guard<std::mutex> guard(breakpoints_lock_);
-    breakpoints_.insert(
-        std::pair<uint32_t, Breakpoint*>(breakpoint->address(), breakpoint));
-  }
-
-  // Find all functions that contain the breakpoint address.
-  auto fns =
-      emulator_->processor()->FindFunctionsWithAddress(breakpoint->address());
-
-  // Add.
-  for (auto fn : fns) {
-    if (fn->AddBreakpoint(breakpoint)) {
-      return 1;
-    }
-  }
-
-  return 0;
+void Debugger::Interrupt() {
+  std::lock_guard<std::recursive_mutex> lock(mutex_);
+  assert_true(execution_state_ == ExecutionState::kRunning);
+  SuspendAllThreads();
+  execution_state_ = ExecutionState::kStopped;
+  server_->OnExecutionInterrupted();
 }
 
-int Debugger::RemoveBreakpoint(Breakpoint* breakpoint) {
-  // Remove from breakpoint map.
-  {
-    std::lock_guard<std::mutex> guard(breakpoints_lock_);
-    auto range = breakpoints_.equal_range(breakpoint->address());
-    if (range.first == range.second) {
-      return 1;
-    }
-    bool found = false;
-    for (auto it = range.first; it != range.second; ++it) {
-      if (it->second == breakpoint) {
-        breakpoints_.erase(it);
-        found = true;
-        break;
-      }
-    }
-    if (!found) {
-      return 1;
-    }
-  }
-
-  // Find all functions that have the breakpoint set.
-  auto fns =
-      emulator_->processor()->FindFunctionsWithAddress(breakpoint->address());
-
-  // Remove.
-  for (auto fn : fns) {
-    fn->RemoveBreakpoint(breakpoint);
-  }
-
-  return 0;
+void Debugger::Continue() {
+  std::lock_guard<std::recursive_mutex> lock(mutex_);
+  assert_true(execution_state_ == ExecutionState::kStopped);
+  ResumeAllThreads();
+  execution_state_ = ExecutionState::kRunning;
+  server_->OnExecutionContinued();
 }
 
-void Debugger::FindBreakpoints(uint32_t address,
-                               std::vector<Breakpoint*>& out_breakpoints) {
-  std::lock_guard<std::mutex> guard(breakpoints_lock_);
-
-  out_breakpoints.clear();
-
-  auto range = breakpoints_.equal_range(address);
-  if (range.first == range.second) {
-    return;
-  }
-
-  for (auto it = range.first; it != range.second; ++it) {
-    Breakpoint* breakpoint = it->second;
-    out_breakpoints.push_back(breakpoint);
-  }
+void Debugger::StepOne(uint32_t thread_id) {
+  std::lock_guard<std::recursive_mutex> lock(mutex_);
+  assert_true(execution_state_ == ExecutionState::kStopped);
+  //
 }
 
-void Debugger::OnThreadCreated(ThreadState* thread_state) {
+void Debugger::StepTo(uint32_t thread_id, uint32_t target_pc) {
+  std::lock_guard<std::recursive_mutex> lock(mutex_);
+  assert_true(execution_state_ == ExecutionState::kStopped);
+  //
+}
+
+void Debugger::OnThreadCreated(xe::kernel::XThread* thread) {
   // TODO(benvanik): notify transports.
 }
 
-void Debugger::OnThreadDestroyed(ThreadState* thread_state) {
+void Debugger::OnThreadExit(xe::kernel::XThread* thread) {
+  // TODO(benvanik): notify transports.
+}
+
+void Debugger::OnThreadDestroyed(xe::kernel::XThread* thread) {
   // TODO(benvanik): notify transports.
 }
 
@@ -259,7 +313,7 @@ void Debugger::OnFunctionDefined(cpu::FunctionInfo* symbol_info,
   // Man, I'd love not to take this lock.
   std::vector<Breakpoint*> breakpoints;
   {
-    std::lock_guard<std::mutex> guard(breakpoints_lock_);
+    std::lock_guard<std::recursive_mutex> lock(mutex_);
     for (uint32_t address = symbol_info->address();
          address <= symbol_info->end_address(); address += 4) {
       auto range = breakpoints_.equal_range(address);
@@ -281,7 +335,7 @@ void Debugger::OnFunctionDefined(cpu::FunctionInfo* symbol_info,
   }
 }
 
-void Debugger::OnBreakpointHit(ThreadState* thread_state,
+void Debugger::OnBreakpointHit(xe::kernel::XThread* thread,
                                Breakpoint* breakpoint) {
   // Suspend all threads immediately.
   SuspendAllThreads();
diff --git a/src/xenia/debug/debugger.h b/src/xenia/debug/debugger.h
index 843cc8a5e..82f044e7d 100644
--- a/src/xenia/debug/debugger.h
+++ b/src/xenia/debug/debugger.h
@@ -29,12 +29,20 @@ DECLARE_bool(debug);
 
 namespace xe {
 class Emulator;
+namespace kernel {
+class XThread;
+}  // namespace kernel
 }  // namespace xe
 
 namespace xe {
 namespace debug {
 
-class Transport;
+class DebugServer;
+
+enum class ExecutionState {
+  kRunning,
+  kStopped,
+};
 
 class Debugger {
  public:
@@ -54,9 +62,7 @@ class Debugger {
   bool is_attached() const { return is_attached_; }
   void set_attached(bool attached);
 
-  bool SuspendAllThreads();
-  bool ResumeThread(uint32_t thread_id);
-  bool ResumeAllThreads();
+  ExecutionState execution_state() const { return execution_state_; }
 
   int AddBreakpoint(Breakpoint* breakpoint);
   int RemoveBreakpoint(Breakpoint* breakpoint);
@@ -66,19 +72,28 @@ class Debugger {
   // TODO(benvanik): utility functions for modification (make function ignored,
   // etc).
 
-  void OnThreadCreated(cpu::ThreadState* thread_state);
-  void OnThreadDestroyed(cpu::ThreadState* thread_state);
+  void Interrupt();
+  void Continue();
+  void StepOne(uint32_t thread_id);
+  void StepTo(uint32_t thread_id, uint32_t target_pc);
+
+  void OnThreadCreated(xe::kernel::XThread* thread);
+  void OnThreadExit(xe::kernel::XThread* thread);
+  void OnThreadDestroyed(xe::kernel::XThread* thread);
+
   void OnFunctionDefined(cpu::FunctionInfo* symbol_info,
                          cpu::Function* function);
 
-  void OnBreakpointHit(cpu::ThreadState* thread_state, Breakpoint* breakpoint);
+  void OnBreakpointHit(xe::kernel::XThread* thread, Breakpoint* breakpoint);
 
  private:
-  void OnMessage(std::vector<uint8_t> buffer);
+  bool SuspendAllThreads();
+  bool ResumeThread(uint32_t thread_id);
+  bool ResumeAllThreads();
 
   Emulator* emulator_ = nullptr;
 
-  std::vector<std::unique_ptr<Transport>> transports_;
+  std::unique_ptr<DebugServer> server_;
   bool is_attached_ = false;
   xe::threading::Fence attach_fence_;
 
@@ -87,7 +102,9 @@ class Debugger {
   std::wstring functions_trace_path_;
   std::unique_ptr<ChunkedMappedMemoryWriter> functions_trace_file_;
 
-  std::mutex breakpoints_lock_;
+  std::recursive_mutex mutex_;
+  ExecutionState execution_state_ = ExecutionState::kStopped;
+
   std::multimap<uint32_t, Breakpoint*> breakpoints_;
 };
 
diff --git a/src/xenia/debug/premake5.lua b/src/xenia/debug/premake5.lua
index a1133046d..7fd45380b 100644
--- a/src/xenia/debug/premake5.lua
+++ b/src/xenia/debug/premake5.lua
@@ -16,4 +16,6 @@ project("xenia-debug")
     project_root.."/third_party/flatbuffers/include"
   })
   local_platform_files()
-  recursive_platform_files("transport")
+  recursive_platform_files("client")
+  recursive_platform_files("proto")
+  recursive_platform_files("server")
diff --git a/src/xenia/debug/proto/packet_reader.h b/src/xenia/debug/proto/packet_reader.h
new file mode 100644
index 000000000..97b95703b
--- /dev/null
+++ b/src/xenia/debug/proto/packet_reader.h
@@ -0,0 +1,151 @@
+/**
+ ******************************************************************************
+ * Xenia : Xbox 360 Emulator Research Project                                 *
+ ******************************************************************************
+ * Copyright 2015 Ben Vanik. All rights reserved.                             *
+ * Released under the BSD license - see LICENSE in the root for more details. *
+ ******************************************************************************
+ */
+
+#ifndef XENIA_DEBUG_PROTO_PACKET_READER_H_
+#define XENIA_DEBUG_PROTO_PACKET_READER_H_
+
+#include <algorithm>
+#include <memory>
+#include <string>
+#include <vector>
+
+#include "xenia/base/assert.h"
+#include "xenia/base/math.h"
+#include "xenia/debug/proto/varint.h"
+#include "xenia/debug/proto/xdp_protocol.h"
+
+namespace xe {
+namespace debug {
+namespace proto {
+
+class PacketReader {
+ public:
+  PacketReader(size_t buffer_capacity) : buffer_(buffer_capacity) {}
+
+  const uint8_t* buffer() { return buffer_.data(); }
+  size_t buffer_capacity() const { return buffer_.size(); }
+  size_t buffer_offset() const { return buffer_offset_; }
+
+  void Reset() {
+    buffer_offset_ = 0;
+    buffer_size_ = 0;
+  }
+
+  void AppendBuffer(const uint8_t* buffer, size_t buffer_length) {
+    if (buffer_size_ + buffer_length > buffer_.size()) {
+      size_t new_size =
+          std::max(buffer_.size() * 2,
+                   xe::round_up(buffer_size_ + buffer_length, 16 * 1024));
+      buffer_.resize(new_size);
+    }
+    std::memcpy(buffer_.data() + buffer_size_, buffer, buffer_length);
+    buffer_size_ += buffer_length;
+  }
+
+  void Compact() {
+    assert_null(current_packet_);
+    if (!buffer_offset_) {
+      return;
+    }
+    std::memmove(buffer_.data(), buffer_.data() + buffer_offset_,
+                 buffer_size_ - buffer_offset_);
+    buffer_size_ -= buffer_offset_;
+    buffer_offset_ = 0;
+  }
+
+  const Packet* Begin() {
+    assert_null(current_packet_);
+    size_t bytes_remaining = buffer_size_ - buffer_offset_;
+    if (bytes_remaining < sizeof(Packet)) {
+      return nullptr;
+    }
+    auto packet =
+        reinterpret_cast<const Packet*>(buffer_.data() + buffer_offset_);
+    if (bytes_remaining < sizeof(Packet) + packet->body_length) {
+      return nullptr;
+    }
+    packet_offset_ = buffer_offset_ + sizeof(Packet);
+    buffer_offset_ += sizeof(Packet) + packet->body_length;
+    current_packet_ = packet;
+    return packet;
+  }
+
+  void End() {
+    assert_not_null(current_packet_);
+    current_packet_ = nullptr;
+    packet_offset_ = 0;
+  }
+
+  const uint8_t* Read(size_t length) {
+    // Can't read into next packet/off of end.
+    assert_not_null(current_packet_);
+    assert_true(packet_offset_ + length <= buffer_offset_);
+    auto ptr = buffer_.data() + packet_offset_;
+    packet_offset_ += length;
+    return ptr;
+  }
+
+  template <typename T>
+  const T* Read() {
+    return reinterpret_cast<const T*>(Read(sizeof(T)));
+  }
+
+  template <typename T>
+  std::vector<const T*> ReadArray(size_t count) {
+    std::vector<const T*> entries;
+    for (size_t i = 0; i < count; ++i) {
+      entries.push_back(Read<T>());
+    }
+    return entries;
+  }
+
+  void Read(void* buffer, size_t buffer_length) {
+    assert_not_null(current_packet_);
+    auto src = Read(buffer_length);
+    std::memcpy(buffer, src, buffer_length);
+  }
+
+  void ReadString(char* buffer, size_t buffer_length) {
+    assert_not_null(current_packet_);
+    varint_t length;
+    auto src = length.Read(buffer_.data() + packet_offset_);
+    assert_not_null(src);
+    assert_true(length < buffer_length);
+    assert_true(length.size() + length < (buffer_offset_ - packet_offset_));
+    std::memcpy(buffer, src, length);
+    packet_offset_ += length;
+  }
+
+  std::string ReadString() {
+    assert_not_null(current_packet_);
+    varint_t length;
+    auto src = length.Read(buffer_.data() + packet_offset_);
+    assert_not_null(src);
+    assert_true(length.size() + length < (buffer_offset_ - packet_offset_));
+    std::string value;
+    value.resize(length.value());
+    std::memcpy(const_cast<char*>(value.data()), src, length);
+    packet_offset_ += length;
+    return value;
+  }
+
+ private:
+  std::vector<uint8_t> buffer_;
+  size_t buffer_offset_ = 0;
+  size_t buffer_size_ = 0;
+
+  const Packet* current_packet_ = nullptr;
+  size_t packet_offset_ = 0;
+};
+
+}  // namespace proto
+}  // namespace debug
+}  // namespace xe
+
+#endif  // XENIA_DEBUG_PROTO_PACKET_READER_H_
diff --git a/src/xenia/debug/proto/packet_writer.h b/src/xenia/debug/proto/packet_writer.h
new file mode 100644
index 000000000..c5c854234
--- /dev/null
+++ b/src/xenia/debug/proto/packet_writer.h
@@ -0,0 +1,98 @@
+/**
+ ******************************************************************************
+ * Xenia : Xbox 360 Emulator Research Project                                 *
+ ******************************************************************************
+ * Copyright 2015 Ben Vanik. All rights reserved.                             *
+ * Released under the BSD license - see LICENSE in the root for more details. *
+ ******************************************************************************
+ */
+
+#ifndef XENIA_DEBUG_PROTO_PACKET_WRITER_H_
+#define XENIA_DEBUG_PROTO_PACKET_WRITER_H_
+
+#include <algorithm>
+#include <string>
+#include <vector>
+
+#include "xenia/base/assert.h"
+#include "xenia/base/math.h"
+#include "xenia/debug/proto/varint.h"
+#include "xenia/debug/proto/xdp_protocol.h"
+
+namespace xe {
+namespace debug {
+namespace proto {
+
+class PacketWriter {
+ public:
+  PacketWriter(size_t buffer_capacity) : buffer_(buffer_capacity) {}
+
+  uint8_t* buffer() { return buffer_.data(); }
+  size_t buffer_capacity() const { return buffer_.size(); }
+  size_t buffer_offset() const { return buffer_offset_; }
+
+  void Reset() { buffer_offset_ = 0; }
+
+  void Begin(PacketType packet_type, request_id_t request_id = 0) {
+    assert_null(current_packet_);
+    current_packet_ = Append<Packet>();
+    current_packet_->packet_type = packet_type;
+    current_packet_->request_id = request_id;
+    current_packet_->body_length = 0;
+  }
+
+  void End() {
+    assert_not_null(current_packet_);
+    current_packet_->body_length =
+        uint32_t((buffer_.data() + buffer_offset_) -
+                 reinterpret_cast<uint8_t*>(current_packet_) - sizeof(Packet));
+    current_packet_ = nullptr;
+  }
+
+  uint8_t* Append(size_t length) {
+    if (buffer_offset_ + length > buffer_.size()) {
+      size_t new_size = std::max(
+          xe::round_up(buffer_offset_ + length, 16 * 1024), buffer_.size() * 2);
+      buffer_.resize(new_size);
+    }
+    auto ptr = buffer_.data() + buffer_offset_;
+    buffer_offset_ += length;
+    return ptr;
+  }
+
+  template <typename T>
+  T* Append() {
+    return reinterpret_cast<T*>(Append(sizeof(T)));
+  }
+
+  void Append(const void* buffer, size_t buffer_length) {
+    auto dest = Append(buffer_length);
+    std::memcpy(dest, buffer, buffer_length);
+  }
+
+  void AppendString(const char* value) {
+    size_t value_length = std::strlen(value);
+    varint_t length(value_length);
+    auto dest = Append(length.size() + value_length);
+    dest = length.Write(dest);
+    std::memcpy(dest, value, value_length);
+  }
+  void AppendString(const std::string& value) {
+    varint_t length(value.size());
+    auto dest = Append(length.size() + value.size());
+    dest = length.Write(dest);
+    std::memcpy(dest, value.data(), value.size());
+  }
+
+ private:
+  std::vector<uint8_t> buffer_;
+  size_t buffer_offset_ = 0;
+
+  Packet* current_packet_ = nullptr;
+};
+
+}  // namespace proto
+}  // namespace debug
+}  // namespace xe
+
+#endif  // XENIA_DEBUG_PROTO_PACKET_WRITER_H_
diff --git a/src/xenia/debug/proto/varint.h b/src/xenia/debug/proto/varint.h
new file mode 100644
index 000000000..c6e5658a7
--- /dev/null
+++ b/src/xenia/debug/proto/varint.h
@@ -0,0 +1,74 @@
+/**
+ ******************************************************************************
+ * Xenia : Xbox 360 Emulator Research Project                                 *
+ ******************************************************************************
+ * Copyright 2015 Ben Vanik. All rights reserved.                             *
+ * Released under the BSD license - see LICENSE in the root for more details. *
+ ******************************************************************************
+ */
+
+#ifndef XENIA_DEBUG_PROTO_VARINT_H_
+#define XENIA_DEBUG_PROTO_VARINT_H_
+
+#include <cstdint>
+
+namespace xe {
+namespace debug {
+namespace proto {
+
+struct varint_t {
+  varint_t() = default;
+  varint_t(uint64_t value) : value_(value) {}
+  varint_t(const varint_t& other) : value_(other.value_) {}
+
+  operator uint64_t() const { return value_; }
+  uint64_t value() const { return value_; }
+
+  size_t size() const {
+    uint64_t value = value_;
+    size_t i = 0;
+    do {
+      value >>= 7;
+      ++i;
+    } while (value >= 0x80);
+    return i + 1;
+  }
+
+  const uint8_t* Read(const uint8_t* src) {
+    if (!(src[0] & 0x80)) {
+      value_ = src[0];
+      return src + 1;
+    }
+    uint64_t r = src[0] & 0x7F;
+    size_t i;
+    for (i = 1; i < 10; ++i) {
+      r |= (src[i] & 0x7F) << (7 * i);
+      if (!(src[i] & 0x80)) {
+        break;
+      }
+    }
+    value_ = r;
+    return src + i + 1;
+  }
+
+  uint8_t* Write(uint8_t* dest) {
+    uint64_t value = value_;
+    size_t i = 0;
+    do {
+      dest[i] = uint8_t(value | 0x80);
+      value >>= 7;
+      ++i;
+    } while (value >= 0x80);
+    dest[i] = uint8_t(value);
+    return dest + i + 1;
+  }
+
+ private:
+  uint64_t value_ = 0;
+};
+
+}  // namespace proto
+}  // namespace debug
+}  // namespace xe
+
+#endif  // XENIA_DEBUG_PROTO_VARINT_H_
diff --git a/src/xenia/debug/proto/xdp_protocol.h b/src/xenia/debug/proto/xdp_protocol.h
new file mode 100644
index 000000000..1a5409794
--- /dev/null
+++ b/src/xenia/debug/proto/xdp_protocol.h
@@ -0,0 +1,173 @@
+/**
+ ******************************************************************************
+ * Xenia : Xbox 360 Emulator Research Project                                 *
+ ******************************************************************************
+ * Copyright 2015 Ben Vanik. All rights reserved.                             *
+ * Released under the BSD license - see LICENSE in the root for more details. *
+ ******************************************************************************
+ */
+
+#ifndef XENIA_DEBUG_PROTO_XDP_PROTOCOL_H_
+#define XENIA_DEBUG_PROTO_XDP_PROTOCOL_H_
+
+#include <cstdint>
+
+namespace xe {
+namespace debug {
+namespace proto {
+
+enum class PacketType : uint16_t {
+  kUnknown = 0,
+  kGenericResponse = 1,
+
+  kExecutionRequest = 10,
+  kExecutionNotification = 11,
+
+  kModuleListRequest = 20,
+  kModuleListResponse = 21,
+
+  kThreadListRequest = 30,
+  kThreadListResponse = 31,
+};
+
+using request_id_t = uint16_t;
+
+struct Packet {
+  PacketType packet_type;
+  request_id_t request_id;
+  uint32_t body_length;
+  uint8_t* body() { return reinterpret_cast<uint8_t*>(this) + sizeof(this); }
+};
+static_assert(sizeof(Packet) == 8, "Fixed packet size");
+
+// Generic response to requests (S->C).
+// Used for any request type that doesn't define its own response.
+struct GenericResponse {
+  static const PacketType type = PacketType::kGenericResponse;
+
+  enum class Code : uint32_t {
+    // Command was received and successfully acted upon.
+    // If the request is handled asynchronously this only indicates that the
+    // command was recognized.
+    kSuccess = 0,
+    // Command was invalid or could not be executed.
+    // A string will follow this response containing an error message.
+    kError = 1,
+  };
+
+  Code code;
+
+  bool is_success() const { return code == Code::kSuccess; }
+};
+
+// Requests execution state changes (C->S).
+// Response is a GenericResponse, and as execution changes one or more
+// ExecutionNotification packets will be sent S->C.
+struct ExecutionRequest {
+  static const PacketType type = PacketType::kExecutionRequest;
+
+  enum class Action : uint32_t {
+    // Continues execution until the next breakpoint.
+    kContinue,
+    // Steps execution by the given step_mode.
+    kStep,
+    // Interrupts execution and breaks.
+    kInterrupt,
+    // Stops execution and causes the server to exit.
+    kExit,
+  };
+
+  enum class StepMode : uint32_t {
+    // Steps a single statement, following branches.
+    kStepOne,
+    // Runs until the given target_pc.
+    kStepTo,
+  };
+
+  Action action;
+  StepMode step_mode;
+  uint32_t thread_id;
+  uint32_t target_pc;
+};
+
+// Notifies clients of changes in execution state (S->C).
+// This is fired asynchronously from any request and possibly due to events
+// external to the client requested ones.
+// After stopping clients should query execution state.
+struct ExecutionNotification {
+  static const PacketType type = PacketType::kExecutionNotification;
+
+  enum class State : uint32_t {
+    // Execution has stopped for stop_reason.
+    kStopped,
+    // Execution has resumed and the target is now running.
+    kRunning,
+    // The target has exited.
+    kExited,
+  };
+
+  enum class Reason : uint32_t {
+    // Stopped because the client requested it with Action::kInterrupt.
+    kInterrupt,
+    // Stopped due to a completed step.
+    kStep,
+    // Stopped at a breakpoint.
+    kBreakpoint,
+    // TODO(benvanik): others? catches? library loads? etc?
+  };
+
+  State current_state;
+  Reason stop_reason;
+};
+
+struct ModuleListRequest {
+  static const PacketType type = PacketType::kModuleListRequest;
+};
+struct ModuleListResponse {
+  static const PacketType type = PacketType::kModuleListResponse;
+
+  uint32_t count;
+  // ModuleListEntry[count]
+};
+struct ModuleListEntry {
+  uint32_t module_handle;
+  uint32_t module_ptr;
+  bool is_kernel_module;
+  char path[256];
+  char name[256];
+};
+
+struct ThreadListRequest {
+  static const PacketType type = PacketType::kThreadListRequest;
+};
+struct ThreadListResponse {
+  static const PacketType type = PacketType::kThreadListResponse;
+
+  uint32_t count;
+  // ThreadListEntry[count]
+};
+struct ThreadListEntry {
+  uint32_t thread_handle;
+  uint32_t thread_id;
+  bool is_host_thread;
+  char name[64];
+  uint32_t exit_code;
+  int32_t priority;
+  uint32_t affinity;
+  uint32_t xapi_thread_startup;
+  uint32_t start_address;
+  uint32_t start_context;
+  uint32_t creation_flags;
+  uint32_t stack_address;
+  uint32_t stack_size;
+  uint32_t stack_base;
+  uint32_t stack_limit;
+  uint32_t pcr_address;
+  uint32_t tls_address;
+};
+
+}  // namespace proto
+}  // namespace debug
+}  // namespace xe
+
+#endif  // XENIA_DEBUG_PROTO_XDP_PROTOCOL_H_
diff --git a/src/xenia/debug/proto/xdp_protocol.md b/src/xenia/debug/proto/xdp_protocol.md
new file mode 100644
index 000000000..f8f8b9c4c
--- /dev/null
+++ b/src/xenia/debug/proto/xdp_protocol.md
@@ -0,0 +1,44 @@
+XDP: Xenia Debug Protocol
+--------------------------
+
+## Overview
+
+### General
+
+* Packets flow in both directions (client and server).
+* Each packet is length-prefixed (exclusive) and tagged with a type.
+* The entire protocol is fully asynchronous, and supports both request/response
+  style RPCs as well as notifications.
+* Request/response RPCs are matched on ID and multiple are allowed to be in
+  flight at a time.
+* Notifications may come in any order.
+
+### Server
+
+The debug server is single threaded and processes commands as a FIFO. This
+means that all requests will be responded to in the order they are received.
+
+### Client
+
+TODO
+
+## Packet Structure
+
+Each packet consists of a length, type, and request ID. The length denotes
+the total number of bytes within the packet body, excluding the packet header.
+The request ID is an opaque value sent by the client when making a request and
+the server returns whatever the ID is when it responds to that request. The ID
+is unused for notifications.
+
+```
+struct Packet {
+  uint16_t packet_type;
+  uint16_t request_id;
+  uint32_t body_length;
+  uint8_t body[body_length];
+};
+```
+
+## Packets
+
+TODO(benvanik): document the various types, etc.
diff --git a/src/xenia/debug/server/gdb/gdb_command_processor.cc b/src/xenia/debug/server/gdb/gdb_command_processor.cc
new file mode 100644
index 000000000..1fe486f36
--- /dev/null
+++ b/src/xenia/debug/server/gdb/gdb_command_processor.cc
@@ -0,0 +1,319 @@
+/**
+ ******************************************************************************
+ * Xenia : Xbox 360 Emulator Research Project                                 *
+ ******************************************************************************
+ * Copyright 2015 Ben Vanik. All rights reserved.                             *
+ * Released under the BSD license - see LICENSE in the root for more details. *
+ ******************************************************************************
+ */
+
+#include "xenia/debug/server/gdb/gdb_command_processor.h"
+
+#include "xenia/base/logging.h"
+#include "xenia/base/string_buffer.h"
+#include "xenia/debug/server/gdb/gdb_server.h"
+
+namespace xe {
+namespace debug {
+namespace server {
+namespace gdb {
+
+constexpr size_t kReceiveBufferSize = 1 * 1024 * 1024;
+constexpr size_t kTransmitBufferSize = 1 * 1024 * 1024;
+
+GdbCommandProcessor::GdbCommandProcessor(GdbServer* server, Debugger* debugger)
+    : server_(server), debugger_(debugger) {
+  receive_buffer_.resize(kReceiveBufferSize);
+  transmit_buffer_.resize(kTransmitBufferSize);
+}
+
+bool GdbCommandProcessor::ProcessBuffer(const uint8_t* buffer,
+                                        size_t buffer_length) {
+  // Grow and append the bytes to the receive buffer.
+  while (receive_offset_ + buffer_length > receive_buffer_.capacity()) {
+    receive_buffer_.resize(receive_buffer_.size() * 2);
+  }
+  std::memcpy(receive_buffer_.data() + receive_offset_, buffer, buffer_length);
+  receive_offset_ += buffer_length;
+
+  // While there are bytes pending in the buffer we scan through looking for end
+  // markers. When we find one, we emit the packet and move on.
+  size_t process_offset = 0;
+  while (process_offset < receive_offset_) {
+    // Look for an end marker.
+    size_t end_offset = -1;
+    size_t buffer_end_offset = -1;
+    for (size_t i = process_offset; i < receive_offset_; ++i) {
+      if (receive_buffer_[i] == '#') {
+        end_offset = i - 1;
+        buffer_end_offset = i + 2;
+        break;
+      }
+    }
+    if (end_offset == -1) {
+      // No end marker found - break out for now.
+      break;
+    }
+
+    // Emit packet.
+    if (!ProcessPacket((const char*)(receive_buffer_.data() + process_offset),
+                       end_offset - process_offset)) {
+      // Failed to process line.
+      std::string line(receive_buffer_.data() + process_offset,
+                       receive_buffer_.data() + end_offset);
+      XELOGE("Failed to process incoming GDB line: %s", line.c_str());
+      return false;
+    }
+    process_offset = buffer_end_offset + 1;
+  }
+
+  // If we have leftover unprocessed bytes move them to the front of the buffer.
+  if (process_offset < receive_offset_) {
+    size_t remaining_bytes = receive_offset_ - process_offset;
+    std::memmove(receive_buffer_.data(),
+                 receive_buffer_.data() + process_offset, remaining_bytes);
+    receive_offset_ = remaining_bytes;
+  } else {
+    receive_offset_ = 0;
+  }
+
+  return true;
+}
+
+bool GdbCommandProcessor::ProcessPacket(const char* buffer,
+                                        size_t buffer_length) {
+  // There may be any number of leading +'s or -'s.
+  size_t offset = 0;
+  for (; offset < buffer_length; ++offset) {
+    if (buffer[offset] == '$') {
+      // Command start.
+      ++offset;
+      break;
+    } else if (buffer[offset] == '+') {
+      // Ack.
+    } else if (buffer[offset] == '-') {
+      // No good - means transmission error.
+      XELOGE("GDB client remorted transmission error");
+      return false;
+    }
+  }
+
+  std::string line((const char*)(buffer + offset), buffer_length - 1);
+  XELOGI("GDB -> %s", line.c_str());
+
+  // Immediately send ACK.
+  if (!no_ack_mode_) {
+    server_->client()->Send("+", 1);
+  }
+
+  const char* buffer_ptr = buffer + offset;
+  bool handled = false;
+  switch (buffer[offset]) {
+    case '!':
+      // Enable extended mode.
+      SendResponse("OK");
+      handled = true;
+      break;
+    case 'v':
+      // Verbose packets.
+      if (std::strstr(buffer_ptr, "vRun") == buffer_ptr) {
+        SendResponse("S05");
+        handled = true;
+      } else if (std::strstr(buffer_ptr, "vCont") == buffer_ptr) {
+        SendResponse("S05");
+        handled = true;
+      }
+      break;
+    case 'q':
+      // Query packets.
+      switch (buffer_ptr[1]) {
+        case 'C':
+          // Get current thread ID.
+          SendResponse("QC01");
+          handled = true;
+          break;
+        case 'R':
+          // Command.
+          SendResponse("OK");
+          handled = true;
+          break;
+        default:
+          if (std::strstr(buffer_ptr, "qSupported") == buffer_ptr) {
+            // Get/set feature support.
+            handled = Process_qSupported(line);
+          } else if (std::strstr(buffer_ptr, "qAttached") == buffer_ptr) {
+            // Check attach mode; 0 = new process, 1 = existing process.
+            SendResponse("0");
+            handled = true;
+          } else if (std::strstr(buffer_ptr, "qfThreadInfo") == buffer_ptr) {
+            // Start of thread list request.
+            SendResponse("m01");
+            handled = true;
+          } else if (std::strstr(buffer_ptr, "qsThreadInfo") == buffer_ptr) {
+            // Continuation of thread list request.
+            SendResponse("l");  // l = last.
+            handled = true;
+          }
+          break;
+      }
+      break;
+    case 'Q':
+      // Set packets.
+      switch (buffer_ptr[1]) {
+        default:
+          if (std::strstr(buffer_ptr, "QStartNoAckMode") == buffer_ptr) {
+            no_ack_mode_ = true;
+            SendResponse("OK");
+            handled = true;
+          }
+          break;
+      }
+      break;
+    case 'H':
+      // Set thread for subsequent operations.
+      SendResponse("OK");
+      handled = true;
+      break;
+    case 'g':
+      // Read all registers.
+      handled = ProcessReadRegisters(line);
+      break;
+    case 'G':
+      // Write all registers.
+      handled = true;
+      break;
+    case 'p':
+      // Read register.
+      handled = true;
+      break;
+    case 'P':
+      // Write register.
+      handled = true;
+      break;
+    case 'm':
+      // Read memory.
+      handled = true;
+      break;
+    case 'M':
+      // Write memory.
+      handled = true;
+      break;
+    case 'Z':
+      // Insert breakpoint.
+      handled = true;
+      break;
+    case 'z':
+      // Remove breakpoint.
+      handled = true;
+      break;
+    case '?':
+      // Query halt reason.
+      SendResponse("S05");
+      handled = true;
+      break;
+    case 'c':
+      // Continue (vCont should be used instead).
+      // NOTE: reply is sent on halt, not right now.
+      SendResponse("S05");
+      handled = true;
+      break;
+    case 's':
+      // Single step.
+      // NOTE: reply is sent on halt, not right now.
+      SendResponse("S05");
+      handled = true;
+      break;
+  }
+  if (!handled) {
+    XELOGE("Unknown GDB packet: %s", buffer_ptr);
+    SendResponse("");
+  }
+  return true;
+}
+
+void GdbCommandProcessor::SendResponse(const char* value, size_t length) {
+  XELOGI("GDB <- %s", value);
+  uint8_t checksum = 0;
+  for (size_t i = 0; i < length; ++i) {
+    uint8_t c = uint8_t(value[i]);
+    if (!c) {
+      break;
+    }
+    checksum += c;
+  }
+  char crc[4];
+  sprintf(crc, "#%.2X", checksum);
+  std::pair<const void*, size_t> buffers[] = {
+      {"$", 1}, {value, length}, {crc, 3},
+  };
+  server_->client()->Send(buffers, xe::countof(buffers));
+}
+
+bool GdbCommandProcessor::Process_qSupported(const std::string& line) {
+  StringBuffer response;
+
+  // Read in the features the client supports.
+  // qSupported[:gdbfeature[;gdbfeature]...]
+  size_t feature_offset = line.find(':');
+  while (feature_offset != std::string::npos) {
+    size_t next_offset = line.find(';', feature_offset + 1);
+    std::string feature =
+        line.substr(feature_offset + 1, next_offset - feature_offset - 1);
+    feature_offset = next_offset;
+    if (feature.find("multiprocess") == 0) {
+      bool is_supported = feature[12] == '+';
+    } else if (feature.find("xmlRegisters") == 0) {
+      // xmlRegisters=A,B,C
+    } else if (feature.find("qRelocInsn") == 0) {
+      bool is_supported = feature[10] == '+';
+    } else if (feature.find("swbreak") == 0) {
+      bool is_supported = feature[7] == '+';
+    } else if (feature.find("hwbreak") == 0) {
+      bool is_supported = feature[7] == '+';
+    } else {
+      XELOGW("Unknown GDB client support feature: %s", feature.c_str());
+    }
+  }
+
+  response.Append("PacketSize=4000;");
+  response.Append("QStartNoAckMode+;");
+  response.Append("qRelocInsn-;");
+  response.Append("multiprocess-;");
+  response.Append("ConditionalBreakpoints-;");
+  response.Append("ConditionalTracepoints-;");
+  response.Append("ReverseContinue-;");
+  response.Append("ReverseStep-;");
+  response.Append("swbreak+;");
+  response.Append("hwbreak+;");
+
+  SendResponse(response.GetString());
+  return true;
+}
+
+bool GdbCommandProcessor::ProcessReadRegisters(const std::string& line) {
+  StringBuffer response;
+
+  for (int32_t n = 0; n < 32; n++) {
+    // gpr
+    response.AppendFormat("%08X", n);
+  }
+  for (int64_t n = 0; n < 32; n++) {
+    // fpr
+    response.AppendFormat("%016llX", n);
+  }
+  response.AppendFormat("%08X", 0x8202FB40);  // pc
+  response.AppendFormat("%08X", 65);          // msr
+  response.AppendFormat("%08X", 66);          // cr
+  response.AppendFormat("%08X", 67);          // lr
+  response.AppendFormat("%08X", 68);          // ctr
+  response.AppendFormat("%08X", 69);          // xer
+  response.AppendFormat("%08X", 70);          // fpscr
+
+  SendResponse(response.GetString());
+  return true;
+}
+
+}  // namespace gdb
+}  // namespace server
+}  // namespace debug
+}  // namespace xe
diff --git a/src/xenia/debug/server/gdb/gdb_command_processor.h b/src/xenia/debug/server/gdb/gdb_command_processor.h
new file mode 100644
index 000000000..634e0c8f6
--- /dev/null
+++ b/src/xenia/debug/server/gdb/gdb_command_processor.h
@@ -0,0 +1,59 @@
+/**
+ ******************************************************************************
+ * Xenia : Xbox 360 Emulator Research Project                                 *
+ ******************************************************************************
+ * Copyright 2015 Ben Vanik. All rights reserved.                             *
+ * Released under the BSD license - see LICENSE in the root for more details. *
+ ******************************************************************************
+ */
+
+#ifndef XENIA_DEBUG_SERVER_GDB_GDB_COMMAND_PROCESSOR_H_
+#define XENIA_DEBUG_SERVER_GDB_GDB_COMMAND_PROCESSOR_H_
+
+#include <cstdint>
+#include <vector>
+
+#include "xenia/debug/debugger.h"
+
+namespace xe {
+namespace debug {
+namespace server {
+namespace gdb {
+
+class GdbServer;
+
+class GdbCommandProcessor {
+ public:
+  GdbCommandProcessor(GdbServer* server, Debugger* debugger);
+  ~GdbCommandProcessor() = default;
+
+  bool ProcessBuffer(const uint8_t* buffer, size_t buffer_length);
+
+ private:
+  bool ProcessPacket(const char* buffer, size_t buffer_length);
+  void SendResponse(const char* value, size_t length);
+  void SendResponse(const char* value) {
+    SendResponse(value, std::strlen(value));
+  }
+  void SendResponse(std::string value) {
+    SendResponse(value.data(), value.size());
+  }
+
+  bool Process_qSupported(const std::string& line);
+  bool ProcessReadRegisters(const std::string& line);
+
+  GdbServer* server_ = nullptr;
+  Debugger* debugger_ = nullptr;
+  std::vector<uint8_t> receive_buffer_;
+  size_t receive_offset_ = 0;
+  std::vector<uint8_t> transmit_buffer_;
+
+  bool no_ack_mode_ = false;
+};
+
+}  // namespace gdb
+}  // namespace server
+}  // namespace debug
+}  // namespace xe
+
+#endif  // XENIA_DEBUG_SERVER_GDB_GDB_COMMAND_PROCESSOR_H_
diff --git a/src/xenia/debug/transport/gdb/gdb_transport.cc b/src/xenia/debug/server/gdb/gdb_server.cc
similarity index 74%
rename from src/xenia/debug/transport/gdb/gdb_transport.cc
rename to src/xenia/debug/server/gdb/gdb_server.cc
index bb8313715..d17448242 100644
--- a/src/xenia/debug/transport/gdb/gdb_transport.cc
+++ b/src/xenia/debug/server/gdb/gdb_server.cc
@@ -7,30 +7,32 @@
  ******************************************************************************
  */
 
-#include "xenia/debug/transport/gdb/gdb_transport.h"
+#include "xenia/debug/server/gdb/gdb_server.h"
 
 #include <gflags/gflags.h>
 
 #include "xenia/base/logging.h"
 #include "xenia/debug/debugger.h"
+#include "xenia/debug/server/gdb/gdb_command_processor.h"
 
-DEFINE_int32(gdb_port, 9000, "Debugger gdbserver TCP port.");
+DEFINE_int32(gdb_server_port, 9000, "Debugger gdbserver TCP port.");
 
 namespace xe {
 namespace debug {
-namespace transport {
+namespace server {
 namespace gdb {
 
-constexpr size_t kReceiveBufferSize = 2 * 1024 * 1024;
+constexpr size_t kReceiveBufferSize = 32 * 1024;
 
-GdbTransport::GdbTransport(Debugger* debugger) : Transport(debugger) {
+GdbServer::GdbServer(Debugger* debugger) : DebugServer(debugger) {
   receive_buffer_.resize(kReceiveBufferSize);
+  command_processor_ = std::make_unique<GdbCommandProcessor>(this, debugger);
 }
 
-GdbTransport::~GdbTransport() = default;
+GdbServer::~GdbServer() = default;
 
-bool GdbTransport::Initialize() {
-  socket_server_ = SocketServer::Create(uint16_t(FLAGS_gdb_port),
+bool GdbServer::Initialize() {
+  socket_server_ = SocketServer::Create(uint16_t(FLAGS_gdb_server_port),
                                         [this](std::unique_ptr<Socket> client) {
                                           AcceptClient(std::move(client));
                                         });
@@ -42,7 +44,7 @@ bool GdbTransport::Initialize() {
   return true;
 }
 
-void GdbTransport::AcceptClient(std::unique_ptr<Socket> client) {
+void GdbServer::AcceptClient(std::unique_ptr<Socket> client) {
   // If we have an existing client, kill it and join its thread.
   if (client_) {
     // TODO(benvanik): GDB say goodbye?
@@ -63,6 +65,9 @@ void GdbTransport::AcceptClient(std::unique_ptr<Socket> client) {
     // Let the debugger know we are present.
     debugger_->set_attached(true);
 
+    // Junk just to poke the remote client.
+    client_->Send("(gdb)\n");
+
     // Main loop.
     bool running = true;
     while (running) {
@@ -91,7 +96,7 @@ void GdbTransport::AcceptClient(std::unique_ptr<Socket> client) {
   });
 }
 
-bool GdbTransport::HandleClientEvent() {
+bool GdbServer::HandleClientEvent() {
   if (!client_->is_connected()) {
     // Known-disconnected.
     return false;
@@ -107,12 +112,17 @@ bool GdbTransport::HandleClientEvent() {
     return true;
   }
 
-  // TODO(benvanik): process incoming command.
+  // Pass off the command processor to do with it what it wants.
+  if (!command_processor_->ProcessBuffer(receive_buffer_.data(), bytes_read)) {
+    // Error.
+    XELOGE("Error processing incoming GDB command; forcing disconnect");
+    return false;
+  }
 
   return true;
 }
 
 }  // namespace gdb
-}  // namespace transport
+}  // namespace server
 }  // namespace debug
 }  // namespace xe
diff --git a/src/xenia/debug/transport/gdb/gdb_transport.h b/src/xenia/debug/server/gdb/gdb_server.h
similarity index 68%
rename from src/xenia/debug/transport/gdb/gdb_transport.h
rename to src/xenia/debug/server/gdb/gdb_server.h
index 1dc7f3098..2e6b3019e 100644
--- a/src/xenia/debug/transport/gdb/gdb_transport.h
+++ b/src/xenia/debug/server/gdb/gdb_server.h
@@ -7,24 +7,28 @@
  ******************************************************************************
  */
 
-#ifndef XENIA_DEBUG_TRANSPORT_GDB_GDB_TRANSPORT_H_
-#define XENIA_DEBUG_TRANSPORT_GDB_GDB_TRANSPORT_H_
+#ifndef XENIA_DEBUG_SERVER_GDB_GDB_SERVER_H_
+#define XENIA_DEBUG_SERVER_GDB_GDB_SERVER_H_
 
 #include <memory>
 
 #include "xenia/base/socket.h"
 #include "xenia/base/threading.h"
-#include "xenia/debug/transport.h"
+#include "xenia/debug/debug_server.h"
 
 namespace xe {
 namespace debug {
-namespace transport {
+namespace server {
 namespace gdb {
 
-class GdbTransport : public Transport {
+class GdbCommandProcessor;
+
+class GdbServer : public DebugServer {
  public:
-  GdbTransport(Debugger* debugger);
-  ~GdbTransport() override;
+  GdbServer(Debugger* debugger);
+  ~GdbServer() override;
+
+  Socket* client() const { return client_.get(); }
 
   bool Initialize() override;
 
@@ -37,11 +41,13 @@ class GdbTransport : public Transport {
   std::unique_ptr<Socket> client_;
   std::unique_ptr<xe::threading::Thread> client_thread_;
   std::vector<uint8_t> receive_buffer_;
+
+  std::unique_ptr<GdbCommandProcessor> command_processor_;
 };
 
 }  // namespace gdb
-}  // namespace transport
+}  // namespace server
 }  // namespace debug
 }  // namespace xe
 
-#endif  // XENIA_DEBUG_TRANSPORT_GDB_GDB_TRANSPORT_H_
+#endif  // XENIA_DEBUG_SERVER_GDB_GDB_SERVER_H_
diff --git a/src/xenia/debug/server/mi/mi_command_processor.cc b/src/xenia/debug/server/mi/mi_command_processor.cc
new file mode 100644
index 000000000..0f9326595
--- /dev/null
+++ b/src/xenia/debug/server/mi/mi_command_processor.cc
@@ -0,0 +1,232 @@
+/**
+ ******************************************************************************
+ * Xenia : Xbox 360 Emulator Research Project                                 *
+ ******************************************************************************
+ * Copyright 2015 Ben Vanik. All rights reserved.                             *
+ * Released under the BSD license - see LICENSE in the root for more details. *
+ ******************************************************************************
+ */
+
+#include "xenia/debug/server/mi/mi_command_processor.h"
+
+#include "xenia/base/logging.h"
+#include "xenia/base/string_buffer.h"
+#include "xenia/debug/server/mi/mi_reader.h"
+#include "xenia/debug/server/mi/mi_server.h"
+#include "xenia/debug/server/mi/mi_writer.h"
+
+namespace xe {
+namespace debug {
+namespace server {
+namespace mi {
+
+constexpr size_t kReceiveBufferSize = 1 * 1024 * 1024;
+constexpr size_t kTransmitBufferSize = 1 * 1024 * 1024;
+
+MICommandProcessor::MICommandProcessor(MIServer* server, Debugger* debugger)
+    : server_(server), debugger_(debugger) {
+  receive_buffer_.resize(kReceiveBufferSize);
+  transmit_buffer_.resize(kTransmitBufferSize);
+}
+
+bool MICommandProcessor::ProcessBuffer(const uint8_t* buffer,
+                                       size_t buffer_length) {
+  // Grow and append the bytes to the receive buffer.
+  while (receive_offset_ + buffer_length > receive_buffer_.capacity()) {
+    receive_buffer_.resize(receive_buffer_.size() * 2);
+  }
+  std::memcpy(receive_buffer_.data() + receive_offset_, buffer, buffer_length);
+  receive_offset_ += buffer_length;
+
+  // While there are bytes pending in the buffer we scan through looking for end
+  // markers. When we find one, we emit the packet and move on.
+  size_t process_offset = 0;
+  while (process_offset < receive_offset_) {
+    // Look for an end marker.
+    size_t end_offset = -1;
+    size_t buffer_end_offset = -1;
+    for (size_t i = process_offset; i < receive_offset_; ++i) {
+      if (receive_buffer_[i] == '\r') {
+        end_offset = i - 1;
+        buffer_end_offset = i + 1;
+        break;
+      } else if (receive_buffer_[i] == '\n') {
+        end_offset = i - 1;
+        buffer_end_offset = i;
+      }
+    }
+    if (end_offset == -1) {
+      // No end marker found - break out for now.
+      break;
+    }
+
+    // Emit packet.
+    if (!ProcessPacket((const char*)(receive_buffer_.data() + process_offset),
+                       end_offset - process_offset)) {
+      // Failed to process line.
+      std::string line(receive_buffer_.data() + process_offset,
+                       receive_buffer_.data() + end_offset);
+      XELOGE("Failed to process incoming MI line: %s", line.c_str());
+      return false;
+    }
+    process_offset = buffer_end_offset + 1;
+  }
+
+  // If we have leftover unprocessed bytes move them to the front of the buffer.
+  if (process_offset < receive_offset_) {
+    size_t remaining_bytes = receive_offset_ - process_offset;
+    std::memmove(receive_buffer_.data(),
+                 receive_buffer_.data() + process_offset, remaining_bytes);
+    receive_offset_ = remaining_bytes;
+  } else {
+    receive_offset_ = 0;
+  }
+
+  return true;
+}
+
+bool MICommandProcessor::ProcessPacket(const char* buffer,
+                                       size_t buffer_length) {
+  // Will likely have a request prefix, like '#####-....'.
+  auto buffer_ptr = std::strchr(buffer, '-');
+  if (!buffer_ptr) {
+    XELOGE("Malformed MI command");
+    return false;
+  }
+  std::string token;
+  if (buffer_ptr != buffer) {
+    token = std::string(buffer, buffer_ptr);
+  }
+  ++buffer_ptr;  // Skip leading '-'.
+
+  std::string line((const char*)buffer_ptr,
+                   buffer_length - (buffer_ptr - buffer) + 1);
+  XELOGI("MI -> %s", line.c_str());
+
+  auto command = line.substr(0, line.find(' '));
+  auto args =
+      command.size() == line.size() ? "" : line.substr(command.size() + 1);
+
+  bool handled = false;
+  if (command == "gdb-set") {
+    auto key = args.substr(0, args.find(' '));
+    auto value = args.substr(args.find(' ') + 1);
+    if (key == "mi-async" || key == "target-async") {
+      bool is_enabled = value == "1" || value == "on";
+      SendResult(token, ResultClass::kDone);
+      handled = true;
+    } else if (key == "stop-on-solib-events") {
+      bool is_enabled = value == "1" || value == "on";
+      SendResult(token, ResultClass::kDone);
+      handled = true;
+    }
+  } else if (command == "file-exec-and-symbols") {
+    // args=foo
+    SendResult(token, ResultClass::kDone);
+    handled = true;
+  } else if (command == "break-insert") {
+    // args=main
+    SendResult(token, ResultClass::kDone);
+    handled = true;
+  } else if (command == "exec-run") {
+    exec_token_ = token;
+    SendResult(token, ResultClass::kRunning);
+    handled = true;
+
+    MIWriter writer(transmit_buffer_.data(), transmit_buffer_.size());
+    writer.AppendRaw(exec_token_);
+    writer.BeginAsyncNotifyRecord("library-loaded");
+    writer.AppendString("id=123");
+    writer.AppendString("target-name=\"foo.xex\"");
+    writer.AppendString("host-name=\"foo.xex\"");
+    writer.EndRecord();
+    server_->client()->Send(transmit_buffer_.data(), writer.buffer_offset());
+  } else if (command == "exec-continue") {
+    exec_token_ = token;
+    SendResult(token, ResultClass::kRunning);
+    handled = true;
+  } else if (command == "exec-interrupt") {
+    SendResult(token, ResultClass::kDone);
+    handled = true;
+
+    // later:
+    MIWriter writer(transmit_buffer_.data(), transmit_buffer_.size());
+    writer.AppendRaw(exec_token_);
+    writer.BeginAsyncExecRecord("stopped");
+    writer.AppendString("reason=\"signal-received\"");
+    writer.AppendString("signal-name=\"SIGINT\"");
+    writer.AppendString("signal-meaning=\"Interrupt\"");
+    writer.EndRecord();
+    server_->client()->Send(transmit_buffer_.data(), writer.buffer_offset());
+  } else if (command == "exec-abort") {
+    XELOGI("Debug client requested abort");
+    SendResult(token, ResultClass::kDone);
+    exit(1);
+    handled = true;
+  } else if (command == "gdb-exit") {
+    // TODO(benvanik): die better?
+    XELOGI("Debug client requested exit");
+    exit(1);
+    SendResult(token, ResultClass::kDone);
+    handled = true;
+  }
+  if (!handled) {
+    XELOGE("Unknown GDB packet: %s", buffer_ptr);
+    SendErrorResult(token, "Unknown/unimplemented");
+  }
+  return true;
+}
+
+void MICommandProcessor::SendConsoleStreamOutput(const char* value) {
+  MIWriter writer(transmit_buffer_.data(), transmit_buffer_.size());
+  writer.BeginConsoleStreamOutput();
+  writer.AppendString(value);
+  writer.EndRecord();
+  server_->client()->Send(transmit_buffer_.data(), writer.buffer_offset());
+}
+
+void MICommandProcessor::SendTargetStreamOutput(const char* value) {
+  MIWriter writer(transmit_buffer_.data(), transmit_buffer_.size());
+  writer.BeginTargetStreamOutput();
+  writer.AppendString(value);
+  writer.EndRecord();
+  server_->client()->Send(transmit_buffer_.data(), writer.buffer_offset());
+}
+
+void MICommandProcessor::SendLogStreamOutput(const char* value) {
+  MIWriter writer(transmit_buffer_.data(), transmit_buffer_.size());
+  writer.BeginLogStreamOutput();
+  writer.AppendString(value);
+  writer.EndRecord();
+  server_->client()->Send(transmit_buffer_.data(), writer.buffer_offset());
+}
+
+void MICommandProcessor::SendResult(const std::string& prefix,
+                                    ResultClass result_class) {
+  MIWriter writer(transmit_buffer_.data(), transmit_buffer_.size());
+  writer.AppendRaw(prefix);
+  writer.BeginResultRecord(result_class);
+  writer.EndRecord();
+  server_->client()->Send(transmit_buffer_.data(), writer.buffer_offset());
+}
+
+void MICommandProcessor::SendErrorResult(const std::string& prefix,
+                                         const char* message,
+                                         const char* code) {
+  MIWriter writer(transmit_buffer_.data(), transmit_buffer_.size());
+  writer.AppendRaw(prefix);
+  writer.BeginResultRecord(ResultClass::kError);
+  if (message) {
+    writer.AppendResult("msg", message);
+  }
+  if (code) {
+    writer.AppendResult("code", code);
+  }
+  writer.EndRecord();
+  server_->client()->Send(transmit_buffer_.data(), writer.buffer_offset());
+}
+
+}  // namespace mi
+}  // namespace server
+}  // namespace debug
+}  // namespace xe
diff --git a/src/xenia/debug/server/mi/mi_command_processor.h b/src/xenia/debug/server/mi/mi_command_processor.h
new file mode 100644
index 000000000..8d144d398
--- /dev/null
+++ b/src/xenia/debug/server/mi/mi_command_processor.h
@@ -0,0 +1,57 @@
+/**
+ ******************************************************************************
+ * Xenia : Xbox 360 Emulator Research Project                                 *
+ ******************************************************************************
+ * Copyright 2015 Ben Vanik. All rights reserved.                             *
+ * Released under the BSD license - see LICENSE in the root for more details. *
+ ******************************************************************************
+ */
+
+#ifndef XENIA_DEBUG_SERVER_MI_MI_COMMAND_PROCESSOR_H_
+#define XENIA_DEBUG_SERVER_MI_MI_COMMAND_PROCESSOR_H_
+
+#include <cstdint>
+#include <vector>
+
+#include "xenia/debug/debugger.h"
+#include "xenia/debug/server/mi/mi_protocol.h"
+
+namespace xe {
+namespace debug {
+namespace server {
+namespace mi {
+
+class MIServer;
+
+class MICommandProcessor {
+ public:
+  MICommandProcessor(MIServer* server, Debugger* debugger);
+  ~MICommandProcessor() = default;
+
+  bool ProcessBuffer(const uint8_t* buffer, size_t buffer_length);
+
+ private:
+  bool ProcessPacket(const char* buffer, size_t buffer_length);
+  void SendConsoleStreamOutput(const char* value);
+  void SendTargetStreamOutput(const char* value);
+  void SendLogStreamOutput(const char* value);
+  void SendResult(const std::string& prefix, ResultClass result_class);
+  void SendErrorResult(const std::string& prefix, const char* message = nullptr,
+                       const char* code = nullptr);
+
+  MIServer* server_ = nullptr;
+  Debugger* debugger_ = nullptr;
+  std::vector<uint8_t> receive_buffer_;
+  size_t receive_offset_ = 0;
+  std::vector<uint8_t> transmit_buffer_;
+
+  // Token of the last -exec-* command. Sent back on stops.
+  std::string exec_token_;
+};
+
+}  // namespace mi
+}  // namespace server
+}  // namespace debug
+}  // namespace xe
+
+#endif  // XENIA_DEBUG_SERVER_MI_MI_COMMAND_PROCESSOR_H_
diff --git a/src/xenia/debug/server/mi/mi_protocol.h b/src/xenia/debug/server/mi/mi_protocol.h
new file mode 100644
index 000000000..82a2ad8f8
--- /dev/null
+++ b/src/xenia/debug/server/mi/mi_protocol.h
@@ -0,0 +1,46 @@
+/**
+ ******************************************************************************
+ * Xenia : Xbox 360 Emulator Research Project                                 *
+ ******************************************************************************
+ * Copyright 2015 Ben Vanik. All rights reserved.                             *
+ * Released under the BSD license - see LICENSE in the root for more details. *
+ ******************************************************************************
+ */
+
+#ifndef XENIA_DEBUG_SERVER_MI_MI_PROTOCOL_H_
+#define XENIA_DEBUG_SERVER_MI_MI_PROTOCOL_H_
+
+#include <cstdint>
+
+namespace xe {
+namespace debug {
+namespace server {
+namespace mi {
+
+enum class RecordToken : char {
+  kResult = '^',
+  kAsyncExec = '*',
+  kAsyncStatus = '+',
+  kAsyncNotify = '=',
+};
+
+enum class StreamToken : char {
+  kConsole = '~',
+  kTarget = '@',
+  kLog = '&',
+};
+
+enum class ResultClass {
+  kDone,
+  kRunning,
+  kConnected,
+  kError,
+  kExit,
+};
+
+}  // namespace mi
+}  // namespace server
+}  // namespace debug
+}  // namespace xe
+
+#endif  // XENIA_DEBUG_SERVER_MI_MI_PROTOCOL_H_
diff --git a/src/xenia/debug/server/mi/mi_reader.cc b/src/xenia/debug/server/mi/mi_reader.cc
new file mode 100644
index 000000000..6f8fb76be
--- /dev/null
+++ b/src/xenia/debug/server/mi/mi_reader.cc
@@ -0,0 +1,22 @@
+/**
+ ******************************************************************************
+ * Xenia : Xbox 360 Emulator Research Project                                 *
+ ******************************************************************************
+ * Copyright 2015 Ben Vanik. All rights reserved.                             *
+ * Released under the BSD license - see LICENSE in the root for more details. *
+ ******************************************************************************
+ */
+
+#include "xenia/debug/server/mi/mi_reader.h"
+
+namespace xe {
+namespace debug {
+namespace server {
+namespace mi {
+
+//
+
+}  // namespace mi
+}  // namespace server
+}  // namespace debug
+}  // namespace xe
diff --git a/src/xenia/debug/server/mi/mi_reader.h b/src/xenia/debug/server/mi/mi_reader.h
new file mode 100644
index 000000000..0252f46f9
--- /dev/null
+++ b/src/xenia/debug/server/mi/mi_reader.h
@@ -0,0 +1,31 @@
+/**
+ ******************************************************************************
+ * Xenia : Xbox 360 Emulator Research Project                                 *
+ ******************************************************************************
+ * Copyright 2015 Ben Vanik. All rights reserved.                             *
+ * Released under the BSD license - see LICENSE in the root for more details. *
+ ******************************************************************************
+ */
+
+#ifndef XENIA_DEBUG_SERVER_MI_MI_READER_H_
+#define XENIA_DEBUG_SERVER_MI_MI_READER_H_
+
+#include <cstdint>
+
+#include "xenia/debug/server/mi/mi_protocol.h"
+
+namespace xe {
+namespace debug {
+namespace server {
+namespace mi {
+
+class MIReader {
+ public:
+};
+
+}  // namespace mi
+}  // namespace server
+}  // namespace debug
+}  // namespace xe
+
+#endif  // XENIA_DEBUG_SERVER_MI_MI_READER_H_
diff --git a/src/xenia/debug/server/mi/mi_server.cc b/src/xenia/debug/server/mi/mi_server.cc
new file mode 100644
index 000000000..19e0f5fd6
--- /dev/null
+++ b/src/xenia/debug/server/mi/mi_server.cc
@@ -0,0 +1,130 @@
+/**
+ ******************************************************************************
+ * Xenia : Xbox 360 Emulator Research Project                                 *
+ ******************************************************************************
+ * Copyright 2015 Ben Vanik. All rights reserved.                             *
+ * Released under the BSD license - see LICENSE in the root for more details. *
+ ******************************************************************************
+ */
+
+#include "xenia/debug/server/mi/mi_server.h"
+
+#include <gflags/gflags.h>
+
+#include "xenia/base/logging.h"
+#include "xenia/debug/debugger.h"
+#include "xenia/debug/server/mi/mi_command_processor.h"
+
+DEFINE_int32(mi_server_port, 9001, "Debugger MI server TCP port.");
+
+namespace xe {
+namespace debug {
+namespace server {
+namespace mi {
+
+constexpr size_t kReceiveBufferSize = 32 * 1024;
+
+MIServer::MIServer(Debugger* debugger) : DebugServer(debugger) {
+  receive_buffer_.resize(kReceiveBufferSize);
+  command_processor_ = std::make_unique<MICommandProcessor>(this, debugger);
+}
+
+MIServer::~MIServer() = default;
+
+bool MIServer::Initialize() {
+  socket_server_ = SocketServer::Create(uint16_t(FLAGS_mi_server_port),
+                                        [this](std::unique_ptr<Socket> client) {
+                                          AcceptClient(std::move(client));
+                                        });
+  if (!socket_server_) {
+    XELOGE("Unable to create MI socket server - port in use?");
+    return false;
+  }
+
+  return true;
+}
+
+void MIServer::AcceptClient(std::unique_ptr<Socket> client) {
+  // If we have an existing client, kill it and join its thread.
+  if (client_) {
+    // TODO(benvanik): GDB say goodbye?
+
+    client_->Close();
+    xe::threading::Wait(client_thread_.get(), true);
+    client_thread_.reset();
+  }
+
+  // Take ownership of the new one.
+  client_ = std::move(client);
+
+  // Create a thread to manage the connection.
+  client_thread_ = xe::threading::Thread::Create({}, [this]() {
+    // TODO(benvanik): GDB protocol stuff? Do we say hi?
+    // TODO(benvanik): move hello to thread
+
+    // Let the debugger know we are present.
+    debugger_->set_attached(true);
+
+    // Junk just to poke the remote client.
+    // The Microsoft MI engine seems to wait for *something* to come through on
+    // connection.
+    client_->Send("(gdb)\n");
+
+    // Main loop.
+    bool running = true;
+    while (running) {
+      auto wait_result = xe::threading::Wait(client_->wait_handle(), true);
+      switch (wait_result) {
+        case xe::threading::WaitResult::kSuccess:
+          // Event (read or close).
+          running = HandleClientEvent();
+          continue;
+        case xe::threading::WaitResult::kAbandoned:
+        case xe::threading::WaitResult::kFailed:
+          // Error - kill the thread.
+          running = false;
+          continue;
+        default:
+          // Eh. Continue.
+          continue;
+      }
+    }
+
+    // Kill client (likely already disconnected).
+    client_.reset();
+
+    // Notify debugger we are no longer attached.
+    debugger_->set_attached(false);
+  });
+}
+
+bool MIServer::HandleClientEvent() {
+  if (!client_->is_connected()) {
+    // Known-disconnected.
+    return false;
+  }
+  // Attempt to read into our buffer.
+  size_t bytes_read =
+      client_->Receive(receive_buffer_.data(), receive_buffer_.capacity());
+  if (bytes_read == -1) {
+    // Disconnected.
+    return false;
+  } else if (bytes_read == 0) {
+    // No data available. Wait again.
+    return true;
+  }
+
+  // Pass off the command processor to do with it what it wants.
+  if (!command_processor_->ProcessBuffer(receive_buffer_.data(), bytes_read)) {
+    // Error.
+    XELOGE("Error processing incoming GDB command; forcing disconnect");
+    return false;
+  }
+
+  return true;
+}
+
+}  // namespace mi
+}  // namespace server
+}  // namespace debug
+}  // namespace xe
diff --git a/src/xenia/debug/server/mi/mi_server.h b/src/xenia/debug/server/mi/mi_server.h
new file mode 100644
index 000000000..9d109d1eb
--- /dev/null
+++ b/src/xenia/debug/server/mi/mi_server.h
@@ -0,0 +1,53 @@
+/**
+ ******************************************************************************
+ * Xenia : Xbox 360 Emulator Research Project                                 *
+ ******************************************************************************
+ * Copyright 2015 Ben Vanik. All rights reserved.                             *
+ * Released under the BSD license - see LICENSE in the root for more details. *
+ ******************************************************************************
+ */
+
+#ifndef XENIA_DEBUG_SERVER_MI_MI_SERVER_H_
+#define XENIA_DEBUG_SERVER_MI_MI_SERVER_H_
+
+#include <memory>
+
+#include "xenia/base/socket.h"
+#include "xenia/base/threading.h"
+#include "xenia/debug/debug_server.h"
+
+namespace xe {
+namespace debug {
+namespace server {
+namespace mi {
+
+class MICommandProcessor;
+
+class MIServer : public DebugServer {
+ public:
+  MIServer(Debugger* debugger);
+  ~MIServer() override;
+
+  Socket* client() const { return client_.get(); }
+
+  bool Initialize() override;
+
+ private:
+  void AcceptClient(std::unique_ptr<Socket> client);
+  bool HandleClientEvent();
+
+  std::unique_ptr<SocketServer> socket_server_;
+
+  std::unique_ptr<Socket> client_;
+  std::unique_ptr<xe::threading::Thread> client_thread_;
+  std::vector<uint8_t> receive_buffer_;
+
+  std::unique_ptr<MICommandProcessor> command_processor_;
+};
+
+}  // namespace mi
+}  // namespace server
+}  // namespace debug
+}  // namespace xe
+
+#endif  // XENIA_DEBUG_SERVER_MI_MI_SERVER_H_
diff --git a/src/xenia/debug/server/mi/mi_writer.cc b/src/xenia/debug/server/mi/mi_writer.cc
new file mode 100644
index 000000000..b2b98cd5d
--- /dev/null
+++ b/src/xenia/debug/server/mi/mi_writer.cc
@@ -0,0 +1,137 @@
+/**
+ ******************************************************************************
+ * Xenia : Xbox 360 Emulator Research Project                                 *
+ ******************************************************************************
+ * Copyright 2015 Ben Vanik. All rights reserved.                             *
+ * Released under the BSD license - see LICENSE in the root for more details. *
+ ******************************************************************************
+ */
+
+#include "xenia/debug/server/mi/mi_writer.h"
+
+#include "xenia/base/assert.h"
+
+namespace xe {
+namespace debug {
+namespace server {
+namespace mi {
+
+void MIWriter::AppendRaw(const char* value, size_t length) {
+  assert_true(buffer_offset_ + length < buffer_capacity_);
+  std::memcpy(buffer_ + buffer_offset_, value, length);
+  buffer_offset_ += length;
+}
+
+void MIWriter::BeginRecord(RecordToken token, const char* record_class) {
+  assert_false(in_record_);
+  in_record_ = true;
+  size_t record_class_length = std::strlen(record_class);
+  assert_true(buffer_offset_ + 1 + record_class_length < buffer_capacity_);
+  buffer_[buffer_offset_++] = char(token);
+  std::memcpy(buffer_ + buffer_offset_, record_class, record_class_length);
+  buffer_offset_ += record_class_length;
+}
+
+void MIWriter::BeginResultRecord(ResultClass result_class) {
+  const char* record_class = "error";
+  switch (result_class) {
+    case ResultClass::kDone:
+      record_class = "done";
+      break;
+    case ResultClass::kRunning:
+      record_class = "running";
+      break;
+    case ResultClass::kConnected:
+      record_class = "connected";
+      break;
+    case ResultClass::kError:
+      record_class = "error";
+      break;
+    case ResultClass::kExit:
+      record_class = "exit";
+      break;
+  }
+  BeginRecord(RecordToken::kResult, record_class);
+}
+
+void MIWriter::BeginStreamRecord(StreamToken token) {
+  assert_false(in_record_);
+  in_record_ = true;
+  assert_true(buffer_offset_ + 1 < buffer_capacity_);
+  buffer_[buffer_offset_++] = char(token);
+}
+
+void MIWriter::EndRecord() {
+  assert_true(in_record_);
+  in_record_ = false;
+  assert_true(buffer_offset_ + 1 < buffer_capacity_);
+  buffer_[buffer_offset_++] = '\n';
+}
+
+void MIWriter::AppendArraySeparator() {
+  if (array_depth_) {
+    if (array_count_[array_depth_]) {
+      assert_true(buffer_offset_ + 1 < buffer_capacity_);
+      buffer_[buffer_offset_++] = ',';
+    }
+    ++array_count_[array_depth_];
+  }
+}
+
+void MIWriter::PushTuple() {
+  assert_true(in_record_);
+  AppendArraySeparator();
+  ++array_depth_;
+  assert_true(array_depth_ < kMaxArrayDepth);
+  array_count_[array_depth_] = 0;
+  assert_true(buffer_offset_ + 1 < buffer_capacity_);
+  buffer_[buffer_offset_++] = '{';
+}
+
+void MIWriter::PopTuple() {
+  --array_depth_;
+  assert_true(buffer_offset_ + 1 < buffer_capacity_);
+  buffer_[buffer_offset_++] = '}';
+}
+
+void MIWriter::PushList() {
+  assert_true(in_record_);
+  AppendArraySeparator();
+  ++array_depth_;
+  assert_true(array_depth_ < kMaxArrayDepth);
+  array_count_[array_depth_] = 0;
+  assert_true(buffer_offset_ + 1 < buffer_capacity_);
+  buffer_[buffer_offset_++] = '[';
+}
+
+void MIWriter::PopList() {
+  --array_depth_;
+  assert_true(buffer_offset_ + 1 < buffer_capacity_);
+  buffer_[buffer_offset_++] = ']';
+}
+
+void MIWriter::AppendString(const char* value, size_t length) {
+  assert_true(in_record_);
+  AppendArraySeparator();
+  assert_true(buffer_offset_ + length < buffer_capacity_);
+  std::memcpy(buffer_ + buffer_offset_, value, length);
+  buffer_offset_ += length;
+}
+
+void MIWriter::AppendResult(const char* variable, const char* value,
+                            size_t length) {
+  assert_true(in_record_);
+  AppendArraySeparator();
+  size_t variable_length = std::strlen(variable);
+  assert_true(buffer_offset_ + 1 + variable_length + length < buffer_capacity_);
+  std::memcpy(buffer_ + buffer_offset_, variable, variable_length);
+  buffer_offset_ += variable_length;
+  buffer_[buffer_offset_++] = '=';
+  std::memcpy(buffer_ + buffer_offset_, value, length);
+  buffer_offset_ += length;
+}
+
+}  // namespace mi
+}  // namespace server
+}  // namespace debug
+}  // namespace xe
diff --git a/src/xenia/debug/server/mi/mi_writer.h b/src/xenia/debug/server/mi/mi_writer.h
new file mode 100644
index 000000000..905cf353a
--- /dev/null
+++ b/src/xenia/debug/server/mi/mi_writer.h
@@ -0,0 +1,101 @@
+/**
+ ******************************************************************************
+ * Xenia : Xbox 360 Emulator Research Project                                 *
+ ******************************************************************************
+ * Copyright 2015 Ben Vanik. All rights reserved.                             *
+ * Released under the BSD license - see LICENSE in the root for more details. *
+ ******************************************************************************
+ */
+
+#ifndef XENIA_DEBUG_SERVER_MI_MI_WRITER_H_
+#define XENIA_DEBUG_SERVER_MI_MI_WRITER_H_
+
+#include <cstdint>
+#include <string>
+
+#include "xenia/debug/server/mi/mi_protocol.h"
+
+namespace xe {
+namespace debug {
+namespace server {
+namespace mi {
+
+// https://sourceware.org/gdb/onlinedocs/gdb/GDB_002fMI-Output-Syntax.html#GDB_002fMI-Output-Syntax
+class MIWriter {
+ public:
+  MIWriter(uint8_t* buffer, size_t buffer_capacity)
+      : buffer_(buffer), buffer_capacity_(buffer_capacity) {}
+
+  uint8_t* buffer() const { return buffer_; }
+  size_t buffer_capacity() const { return buffer_capacity_; }
+  size_t buffer_offset() const { return buffer_offset_; }
+
+  void AppendRaw(const char* value, size_t length);
+  void AppendRaw(const char* value) { AppendRaw(value, std::strlen(value)); }
+  void AppendRaw(const std::string& value) {
+    AppendRaw(value.c_str(), value.size());
+  }
+
+  void BeginResultRecord(ResultClass result_class);
+  void BeginAsyncExecRecord(const char* async_class) {
+    BeginRecord(RecordToken::kAsyncExec, async_class);
+    array_depth_ = 1;
+    array_count_[array_depth_] = 1;
+  }
+  void BeginAsyncStatusRecord(const char* async_class) {
+    BeginRecord(RecordToken::kAsyncStatus, async_class);
+    array_depth_ = 1;
+    array_count_[array_depth_] = 1;
+  }
+  void BeginAsyncNotifyRecord(const char* async_class) {
+    BeginRecord(RecordToken::kAsyncNotify, async_class);
+    array_depth_ = 1;
+    array_count_[array_depth_] = 1;
+  }
+  void BeginConsoleStreamOutput() { BeginStreamRecord(StreamToken::kConsole); }
+  void BeginTargetStreamOutput() { BeginStreamRecord(StreamToken::kTarget); }
+  void BeginLogStreamOutput() { BeginStreamRecord(StreamToken::kLog); }
+  void EndRecord();
+
+  void PushTuple();
+  void PopTuple();
+  void PushList();
+  void PopList();
+
+  void AppendString(const char* value, size_t length);
+  void AppendString(const char* value) {
+    AppendString(value, std::strlen(value));
+  }
+  void AppendString(const std::string& value) {
+    AppendString(value.c_str(), value.size());
+  }
+
+  void AppendResult(const char* variable, const char* value, size_t length);
+  void AppendResult(const char* variable, const char* value) {
+    AppendResult(variable, value, std::strlen(value));
+  }
+  void AppendResult(const char* variable, const std::string& value) {
+    AppendResult(variable, value.c_str(), value.size());
+  }
+
+ private:
+  void BeginRecord(RecordToken token, const char* record_class);
+  void BeginStreamRecord(StreamToken token);
+  void AppendArraySeparator();
+
+  uint8_t* buffer_ = nullptr;
+  size_t buffer_capacity_ = 0;
+  size_t buffer_offset_ = 0;
+
+  static const int kMaxArrayDepth = 32;
+  bool in_record_ = false;
+  int array_depth_ = 0;
+  int array_count_[kMaxArrayDepth];
+};
+
+}  // namespace mi
+}  // namespace server
+}  // namespace debug
+}  // namespace xe
+
+#endif  // XENIA_DEBUG_SERVER_MI_MI_WRITER_H_
diff --git a/src/xenia/debug/server/xdp/xdp_server.cc b/src/xenia/debug/server/xdp/xdp_server.cc
new file mode 100644
index 000000000..2b6bc386a
--- /dev/null
+++ b/src/xenia/debug/server/xdp/xdp_server.cc
@@ -0,0 +1,313 @@
+/**
+ ******************************************************************************
+ * Xenia : Xbox 360 Emulator Research Project                                 *
+ ******************************************************************************
+ * Copyright 2015 Ben Vanik. All rights reserved.                             *
+ * Released under the BSD license - see LICENSE in the root for more details. *
+ ******************************************************************************
+ */
+
+#include "xenia/debug/server/xdp/xdp_server.h"
+
+#include <gflags/gflags.h>
+
+#include "xenia/base/logging.h"
+#include "xenia/debug/debugger.h"
+#include "xenia/emulator.h"
+#include "xenia/kernel/kernel_state.h"
+#include "xenia/kernel/objects/xmodule.h"
+#include "xenia/kernel/objects/xthread.h"
+
+DEFINE_int32(xdp_server_port, 9002, "Debugger XDP server TCP port.");
+
+namespace xe {
+namespace debug {
+namespace server {
+namespace xdp {
+
+using namespace xe::debug::proto;
+using namespace xe::kernel;
+
+constexpr size_t kReceiveBufferSize = 32 * 1024;
+constexpr size_t kReadBufferSize = 1 * 1024 * 1024;
+constexpr size_t kWriteBufferSize = 1 * 1024 * 1024;
+
+XdpServer::XdpServer(Debugger* debugger)
+    : DebugServer(debugger),
+      packet_reader_(kReadBufferSize),
+      packet_writer_(kWriteBufferSize) {
+  receive_buffer_.resize(kReceiveBufferSize);
+}
+
+XdpServer::~XdpServer() = default;
+
+bool XdpServer::Initialize() {
+  socket_server_ = SocketServer::Create(uint16_t(FLAGS_xdp_server_port),
+                                        [this](std::unique_ptr<Socket> client) {
+                                          AcceptClient(std::move(client));
+                                        });
+  if (!socket_server_) {
+    XELOGE("Unable to create XDP socket server - port in use?");
+    return false;
+  }
+
+  return true;
+}
+
+void XdpServer::AcceptClient(std::unique_ptr<Socket> client) {
+  // If we have an existing client, kill it and join its thread.
+  if (client_) {
+    // TODO(benvanik): XDP say goodbye?
+
+    client_->Close();
+    xe::threading::Wait(client_thread_.get(), true);
+    client_thread_.reset();
+  }
+
+  // Take ownership of the new one.
+  client_ = std::move(client);
+
+  // Create a thread to manage the connection.
+  client_thread_ = xe::threading::Thread::Create({}, [this]() {
+    // TODO(benvanik): GDB protocol stuff? Do we say hi?
+    // TODO(benvanik): move hello to thread
+
+    // Let the debugger know we are present.
+    debugger_->set_attached(true);
+
+    // Notify the client of the current state.
+    if (debugger_->execution_state() == ExecutionState::kRunning) {
+      OnExecutionContinued();
+    } else {
+      OnExecutionInterrupted();
+    }
+
+    // Main loop.
+    bool running = true;
+    while (running) {
+      auto wait_result = xe::threading::Wait(client_->wait_handle(), true);
+      switch (wait_result) {
+        case xe::threading::WaitResult::kSuccess:
+          // Event (read or close).
+          running = HandleClientEvent();
+          continue;
+        case xe::threading::WaitResult::kAbandoned:
+        case xe::threading::WaitResult::kFailed:
+          // Error - kill the thread.
+          running = false;
+          continue;
+        default:
+          // Eh. Continue.
+          continue;
+      }
+    }
+
+    // Kill client (likely already disconnected).
+    client_.reset();
+
+    // Notify debugger we are no longer attached.
+    debugger_->set_attached(false);
+  });
+}
+
+bool XdpServer::HandleClientEvent() {
+  if (!client_->is_connected()) {
+    // Known-disconnected.
+    return false;
+  }
+  // Attempt to read into our buffer.
+  size_t bytes_read =
+      client_->Receive(receive_buffer_.data(), receive_buffer_.capacity());
+  if (bytes_read == -1) {
+    // Disconnected.
+    return false;
+  } else if (bytes_read == 0) {
+    // No data available. Wait again.
+    return true;
+  }
+
+  // Pass off the command processor to do with it what it wants.
+  if (!ProcessBuffer(receive_buffer_.data(), bytes_read)) {
+    // Error.
+    XELOGE("Error processing incoming XDP command; forcing disconnect");
+    return false;
+  }
+
+  return true;
+}
+bool XdpServer::ProcessBuffer(const uint8_t* buffer, size_t buffer_length) {
+  // Grow and append the bytes to the receive buffer.
+  packet_reader_.AppendBuffer(buffer, buffer_length);
+
+  // Process all packets in the buffer.
+  while (true) {
+    auto packet = packet_reader_.Begin();
+    if (!packet) {
+      // Out of packets. Compact any unused space.
+      packet_reader_.Compact();
+      break;
+    }
+
+    // Emit packet.
+    if (!ProcessPacket(packet)) {
+      // Failed to process packet.
+      XELOGE("Failed to process incoming packet");
+      return false;
+    }
+
+    packet_reader_.End();
+  }
+
+  Flush();
+  return true;
+}
+
+bool XdpServer::ProcessPacket(const proto::Packet* packet) {
+  auto emulator = debugger()->emulator();
+  auto kernel_state = emulator->kernel_state();
+  auto object_table = kernel_state->object_table();
+
+  switch (packet->packet_type) {
+    case PacketType::kExecutionRequest: {
+      auto body = packet_reader_.Read<ExecutionRequest>();
+      switch (body->action) {
+        case ExecutionRequest::Action::kContinue: {
+          debugger_->Continue();
+        } break;
+        case ExecutionRequest::Action::kStep: {
+          switch (body->step_mode) {
+            case ExecutionRequest::StepMode::kStepOne: {
+              debugger_->StepOne(body->thread_id);
+            } break;
+            case ExecutionRequest::StepMode::kStepTo: {
+              debugger_->StepTo(body->thread_id, body->target_pc);
+            } break;
+            default:
+              assert_unhandled_case(body->step_mode);
+              return false;
+          }
+        } break;
+        case ExecutionRequest::Action::kInterrupt: {
+          debugger_->Interrupt();
+        } break;
+        case ExecutionRequest::Action::kExit: {
+          XELOGI("Debug client requested exit");
+          exit(1);
+        } break;
+      }
+      SendSuccess(packet->request_id);
+    } break;
+    case PacketType::kModuleListRequest: {
+      packet_writer_.Begin(PacketType::kModuleListResponse);
+      auto body = packet_writer_.Append<ModuleListResponse>();
+      auto modules =
+          object_table->GetObjectsByType<XModule>(XObject::Type::kTypeModule);
+      body->count = uint32_t(modules.size());
+      for (auto& module : modules) {
+        auto entry = packet_writer_.Append<ModuleListEntry>();
+        entry->module_handle = module->handle();
+        entry->module_ptr = module->hmodule_ptr();
+        entry->is_kernel_module =
+            module->module_type() == XModule::ModuleType::kKernelModule;
+        std::strncpy(entry->path, module->path().c_str(),
+                     xe::countof(entry->path));
+        std::strncpy(entry->name, module->name().c_str(),
+                     xe::countof(entry->name));
+      }
+      packet_writer_.End();
+    } break;
+    case PacketType::kThreadListRequest: {
+      packet_writer_.Begin(PacketType::kThreadListResponse);
+      auto body = packet_writer_.Append<ThreadListResponse>();
+      auto threads =
+          object_table->GetObjectsByType<XThread>(XObject::Type::kTypeThread);
+      body->count = uint32_t(threads.size());
+      for (auto& thread : threads) {
+        auto entry = packet_writer_.Append<ThreadListEntry>();
+        entry->thread_handle = thread->handle();
+        entry->thread_id = thread->thread_id();
+        entry->is_host_thread = !thread->is_guest_thread();
+        std::strncpy(entry->name, thread->name().c_str(),
+                     xe::countof(entry->name));
+        entry->exit_code;
+        entry->priority = thread->priority();
+        entry->xapi_thread_startup =
+            thread->creation_params()->xapi_thread_startup;
+        entry->start_address = thread->creation_params()->start_address;
+        entry->start_context = thread->creation_params()->start_context;
+        entry->creation_flags = thread->creation_params()->creation_flags;
+        entry->stack_address = thread->thread_state()->stack_address();
+        entry->stack_size = thread->thread_state()->stack_size();
+        entry->stack_base = thread->thread_state()->stack_base();
+        entry->stack_limit = thread->thread_state()->stack_limit();
+        entry->pcr_address = thread->pcr_ptr();
+        entry->tls_address = thread->tls_ptr();
+      }
+      packet_writer_.End();
+    } break;
+    default: {
+      XELOGE("Unknown packet type");
+      SendError(packet->request_id, "Unknown packet type");
+      return false;
+    } break;
+  }
+  return true;
+}
+
+void XdpServer::OnExecutionContinued() {
+  packet_writer_.Begin(PacketType::kExecutionNotification);
+  auto body = packet_writer_.Append<ExecutionNotification>();
+  body->current_state = ExecutionNotification::State::kRunning;
+  packet_writer_.End();
+  Flush();
+}
+
+void XdpServer::OnExecutionInterrupted() {
+  packet_writer_.Begin(PacketType::kExecutionNotification);
+  auto body = packet_writer_.Append<ExecutionNotification>();
+  body->current_state = ExecutionNotification::State::kStopped;
+  body->stop_reason = ExecutionNotification::Reason::kInterrupt;
+  packet_writer_.End();
+  Flush();
+}
+
+void XdpServer::Flush() {
+  if (!packet_writer_.buffer_offset()) {
+    return;
+  }
+  client_->Send(packet_writer_.buffer(), packet_writer_.buffer_offset());
+  packet_writer_.Reset();
+}
+
+void XdpServer::SendSuccess(proto::request_id_t request_id) {
+  packet_writer_.Begin(PacketType::kGenericResponse, request_id);
+  auto body = packet_writer_.Append<GenericResponse>();
+  body->code = GenericResponse::Code::kSuccess;
+  packet_writer_.End();
+  Flush();
+}
+
+void XdpServer::SendError(proto::request_id_t request_id,
+                          const char* error_message) {
+  packet_writer_.Begin(PacketType::kGenericResponse, request_id);
+  auto body = packet_writer_.Append<GenericResponse>();
+  body->code = GenericResponse::Code::kError;
+  packet_writer_.AppendString(error_message ? error_message : "");
+  packet_writer_.End();
+  Flush();
+}
+
+void XdpServer::SendError(proto::request_id_t request_id,
+                          const std::string& error_message) {
+  packet_writer_.Begin(PacketType::kGenericResponse, request_id);
+  auto body = packet_writer_.Append<GenericResponse>();
+  body->code = GenericResponse::Code::kError;
+  packet_writer_.AppendString(error_message);
+  packet_writer_.End();
+  Flush();
+}
+
+}  // namespace xdp
+}  // namespace server
+}  // namespace debug
+}  // namespace xe
diff --git a/src/xenia/debug/server/xdp/xdp_server.h b/src/xenia/debug/server/xdp/xdp_server.h
new file mode 100644
index 000000000..c5f5db4da
--- /dev/null
+++ b/src/xenia/debug/server/xdp/xdp_server.h
@@ -0,0 +1,67 @@
+/**
+ ******************************************************************************
+ * Xenia : Xbox 360 Emulator Research Project                                 *
+ ******************************************************************************
+ * Copyright 2015 Ben Vanik. All rights reserved.                             *
+ * Released under the BSD license - see LICENSE in the root for more details. *
+ ******************************************************************************
+ */
+
+#ifndef XENIA_DEBUG_SERVER_XDP_XDP_SERVER_H_
+#define XENIA_DEBUG_SERVER_XDP_XDP_SERVER_H_
+
+#include <memory>
+
+#include "xenia/base/socket.h"
+#include "xenia/base/threading.h"
+#include "xenia/debug/debug_server.h"
+#include "xenia/debug/proto/packet_reader.h"
+#include "xenia/debug/proto/packet_writer.h"
+#include "xenia/debug/proto/xdp_protocol.h"
+
+namespace xe {
+namespace debug {
+namespace server {
+namespace xdp {
+
+class XdpServer : public DebugServer {
+ public:
+  XdpServer(Debugger* debugger);
+  ~XdpServer() override;
+
+  Socket* client() const { return client_.get(); }
+
+  bool Initialize() override;
+
+  void OnExecutionContinued() override;
+  void OnExecutionInterrupted() override;
+
+ private:
+  void AcceptClient(std::unique_ptr<Socket> client);
+  bool HandleClientEvent();
+
+  bool ProcessBuffer(const uint8_t* buffer, size_t buffer_length);
+  bool ProcessPacket(const proto::Packet* packet);
+
+  void Flush();
+  void SendSuccess(proto::request_id_t request_id);
+  void SendError(proto::request_id_t request_id,
+                 const char* error_message = nullptr);
+  void SendError(proto::request_id_t request_id,
+                 const std::string& error_message);
+
+  std::unique_ptr<SocketServer> socket_server_;
+
+  std::unique_ptr<Socket> client_;
+  std::unique_ptr<xe::threading::Thread> client_thread_;
+  std::vector<uint8_t> receive_buffer_;
+  proto::PacketReader packet_reader_;
+  proto::PacketWriter packet_writer_;
+};
+
+}  // namespace xdp
+}  // namespace server
+}  // namespace debug
+}  // namespace xe
+
+#endif  // XENIA_DEBUG_SERVER_XDP_XDP_SERVER_H_
diff --git a/src/xenia/debug/ui/application.cc b/src/xenia/debug/ui/application.cc
index 15ccf21aa..f0b0d1477 100644
--- a/src/xenia/debug/ui/application.cc
+++ b/src/xenia/debug/ui/application.cc
@@ -58,6 +58,15 @@ std::unique_ptr<Application> Application::Create() {
 }
 
 bool Application::Initialize() {
+  // Bind the object model to the client so it'll maintain state.
+  system_ = std::make_unique<model::System>(loop(), &client_);
+  client_.set_listener(system_.get());
+
+  // TODO(benvanik): flags and such.
+  if (!client_.Connect("localhost", 9002)) {
+    return false;
+  }
+
   main_window_ = std::make_unique<MainWindow>(this);
   if (!main_window_->Initialize()) {
     XELOGE("Unable to initialize main window");
diff --git a/src/xenia/debug/ui/application.h b/src/xenia/debug/ui/application.h
index 72b4a3634..0c31f580e 100644
--- a/src/xenia/debug/ui/application.h
+++ b/src/xenia/debug/ui/application.h
@@ -12,6 +12,8 @@
 
 #include <memory>
 
+#include "xenia/debug/client/xdp/xdp_client.h"
+#include "xenia/debug/ui/model/system.h"
 #include "xenia/ui/loop.h"
 
 namespace xe {
@@ -29,6 +31,8 @@ class Application {
 
   xe::ui::Loop* loop() { return loop_.get(); }
   MainWindow* main_window() const { return main_window_.get(); }
+  client::xdp::XdpClient* client() { return &client_; }
+  model::System* system() const { return system_.get(); }
 
   void Quit();
 
@@ -39,6 +43,9 @@ class Application {
 
   std::unique_ptr<xe::ui::Loop> loop_;
   std::unique_ptr<MainWindow> main_window_;
+  client::xdp::XdpClient client_;
+
+  std::unique_ptr<model::System> system_;
 };
 
 }  // namespace ui
diff --git a/src/xenia/debug/ui/main_window.cc b/src/xenia/debug/ui/main_window.cc
index b4aa45ab9..f4ecb5c5a 100644
--- a/src/xenia/debug/ui/main_window.cc
+++ b/src/xenia/debug/ui/main_window.cc
@@ -21,6 +21,8 @@ namespace xe {
 namespace debug {
 namespace ui {
 
+using namespace xe::debug::client::xdp;
+
 using xe::ui::MenuItem;
 
 const std::wstring kBaseTitle = L"xenia debugger";
@@ -30,6 +32,8 @@ MainWindow::MainWindow(Application* app) : app_(app) {}
 MainWindow::~MainWindow() = default;
 
 bool MainWindow::Initialize() {
+  client_ = app_->client();
+
   platform_window_ = xe::ui::Window::Create(app()->loop(), kBaseTitle);
   if (!platform_window_) {
     return false;
@@ -106,11 +110,14 @@ void MainWindow::BuildUI() {
           .gravity(Gravity::kAll)
           .distribution(LayoutDistribution::kAvailable)
           .axis(Axis::kY)
-          .child(LayoutBoxNode()
-                     .id("toolbar_box")
-                     .gravity(Gravity::kTop | Gravity::kLeftRight)
-                     .distribution(LayoutDistribution::kAvailable)
-                     .child(LabelNode("toolbar")))
+          .child(
+              LayoutBoxNode()
+                  .id("toolbar_box")
+                  .gravity(Gravity::kTop | Gravity::kLeftRight)
+                  .distribution(LayoutDistribution::kGravity)
+                  .distribution_position(LayoutDistributionPosition::kLeftTop)
+                  .child(ButtonNode("Pause").id("pause_button"))
+                  .child(ButtonNode("Continue").id("resume_button")))
           .child(
               SplitContainerNode()
                   .id("split_container")
@@ -132,15 +139,50 @@ void MainWindow::BuildUI() {
       {TBIDC("tab_container"), &ui_.tab_container},
   });
 
+  handler_ = std::make_unique<el::EventHandler>(window_.get());
+  handler_->Listen(el::EventType::kClick, TBIDC("pause_button"),
+                   [this](const el::Event& ev) {
+                     client_->Interrupt();
+                     return true;
+                   });
+  handler_->Listen(el::EventType::kClick, TBIDC("resume_button"),
+                   [this](const el::Event& ev) {
+                     client_->Continue();
+                     return true;
+                   });
+
+  system()->on_execution_state_changed.AddListener(
+      [this]() { UpdateElementState(); });
+
   ui_.tab_container->tab_bar()->LoadNodeTree(ButtonNode(cpu_view_.name()));
   ui_.tab_container->content_root()->AddChild(cpu_view_.BuildUI());
+  cpu_view_.Setup(Application::current()->client());
 
   ui_.tab_container->tab_bar()->LoadNodeTree(ButtonNode(gpu_view_.name()));
   ui_.tab_container->content_root()->AddChild(gpu_view_.BuildUI());
+  gpu_view_.Setup(Application::current()->client());
+
+  UpdateElementState();
 
   el::util::ShowDebugInfoSettingsWindow(root_element);
 }
 
+void MainWindow::UpdateElementState() {
+  bool is_running = client_->execution_state() == ExecutionState::kRunning;
+
+  el::TabContainer* tab_container;
+  el::Button* pause_button;
+  el::Button* resume_button;
+  window_->GetElementsById({
+      {TBIDC("tab_container"), &tab_container},
+      {TBIDC("pause_button"), &pause_button},
+      {TBIDC("resume_button"), &resume_button},
+  });
+  tab_container->set_enabled(!is_running);
+  pause_button->set_enabled(is_running);
+  resume_button->set_enabled(!is_running);
+}
+
 void MainWindow::OnClose() { app_->Quit(); }
 
 }  // namespace ui
diff --git a/src/xenia/debug/ui/main_window.h b/src/xenia/debug/ui/main_window.h
index c51117a42..e99bd1e14 100644
--- a/src/xenia/debug/ui/main_window.h
+++ b/src/xenia/debug/ui/main_window.h
@@ -28,6 +28,8 @@ class MainWindow {
   ~MainWindow();
 
   Application* app() const { return app_; }
+  xe::ui::Loop* loop() const { return app_->loop(); }
+  model::System* system() const { return app_->system(); }
 
   bool Initialize();
 
@@ -35,10 +37,12 @@ class MainWindow {
 
  private:
   void BuildUI();
+  void UpdateElementState();
 
   void OnClose();
 
   Application* app_ = nullptr;
+  xe::debug::client::xdp::XdpClient* client_ = nullptr;
 
   std::unique_ptr<xe::ui::Window> platform_window_;
   std::unique_ptr<el::Window> window_;
@@ -47,6 +51,7 @@ class MainWindow {
     el::LayoutBox* toolbar_box;
     el::TabContainer* tab_container;
   } ui_ = {0};
+  std::unique_ptr<el::EventHandler> handler_;
   views::cpu::CpuView cpu_view_;
   views::gpu::GpuView gpu_view_;
 };
diff --git a/src/xenia/debug/ui/model/function.cc b/src/xenia/debug/ui/model/function.cc
new file mode 100644
index 000000000..9808fff1a
--- /dev/null
+++ b/src/xenia/debug/ui/model/function.cc
@@ -0,0 +1,22 @@
+/**
+ ******************************************************************************
+ * Xenia : Xbox 360 Emulator Research Project                                 *
+ ******************************************************************************
+ * Copyright 2015 Ben Vanik. All rights reserved.                             *
+ * Released under the BSD license - see LICENSE in the root for more details. *
+ ******************************************************************************
+ */
+
+#include "xenia/debug/ui/model/function.h"
+
+namespace xe {
+namespace debug {
+namespace ui {
+namespace model {
+
+//
+
+}  // namespace model
+}  // namespace ui
+}  // namespace debug
+}  // namespace xe
diff --git a/src/xenia/debug/ui/model/function.h b/src/xenia/debug/ui/model/function.h
new file mode 100644
index 000000000..a31f7b9ea
--- /dev/null
+++ b/src/xenia/debug/ui/model/function.h
@@ -0,0 +1,29 @@
+/**
+ ******************************************************************************
+ * Xenia : Xbox 360 Emulator Research Project                                 *
+ ******************************************************************************
+ * Copyright 2015 Ben Vanik. All rights reserved.                             *
+ * Released under the BSD license - see LICENSE in the root for more details. *
+ ******************************************************************************
+ */
+
+#ifndef XENIA_DEBUG_UI_MODEL_FUNCTION_H_
+#define XENIA_DEBUG_UI_MODEL_FUNCTION_H_
+
+#include <cstdint>
+
+namespace xe {
+namespace debug {
+namespace ui {
+namespace model {
+
+class Function {
+ public:
+};
+
+}  // namespace model
+}  // namespace ui
+}  // namespace debug
+}  // namespace xe
+
+#endif  // XENIA_DEBUG_UI_MODEL_FUNCTION_H_
diff --git a/src/xenia/debug/ui/model/module.cc b/src/xenia/debug/ui/model/module.cc
new file mode 100644
index 000000000..675df0647
--- /dev/null
+++ b/src/xenia/debug/ui/model/module.cc
@@ -0,0 +1,32 @@
+/**
+ ******************************************************************************
+ * Xenia : Xbox 360 Emulator Research Project                                 *
+ ******************************************************************************
+ * Copyright 2015 Ben Vanik. All rights reserved.                             *
+ * Released under the BSD license - see LICENSE in the root for more details. *
+ ******************************************************************************
+ */
+
+#include "xenia/debug/ui/model/module.h"
+
+#include "xenia/debug/ui/model/system.h"
+
+namespace xe {
+namespace debug {
+namespace ui {
+namespace model {
+
+void Module::Update(const proto::ModuleListEntry* entry) {
+  if (!entry_.module_handle) {
+    std::memcpy(&entry_, entry, sizeof(entry_));
+  } else {
+    std::memcpy(&temp_entry_, entry, sizeof(temp_entry_));
+    system_->loop()->Post(
+        [this]() { std::memcpy(&entry_, &temp_entry_, sizeof(temp_entry_)); });
+  }
+}
+
+}  // namespace model
+}  // namespace ui
+}  // namespace debug
+}  // namespace xe
diff --git a/src/xenia/debug/ui/model/module.h b/src/xenia/debug/ui/model/module.h
new file mode 100644
index 000000000..3ff3dd3a2
--- /dev/null
+++ b/src/xenia/debug/ui/model/module.h
@@ -0,0 +1,51 @@
+/**
+ ******************************************************************************
+ * Xenia : Xbox 360 Emulator Research Project                                 *
+ ******************************************************************************
+ * Copyright 2015 Ben Vanik. All rights reserved.                             *
+ * Released under the BSD license - see LICENSE in the root for more details. *
+ ******************************************************************************
+ */
+
+#ifndef XENIA_DEBUG_UI_MODEL_MODULE_H_
+#define XENIA_DEBUG_UI_MODEL_MODULE_H_
+
+#include <cstdint>
+#include <string>
+
+#include "xenia/debug/proto/xdp_protocol.h"
+
+namespace xe {
+namespace debug {
+namespace ui {
+namespace model {
+
+class System;
+
+class Module {
+ public:
+  Module(System* system) : system_(system) {}
+
+  bool is_dead() const { return is_dead_; }
+  void set_dead(bool is_dead) { is_dead_ = is_dead; }
+
+  uint32_t module_handle() const { return entry_.module_handle; }
+  bool is_kernel_module() const { return entry_.is_kernel_module; }
+  std::string name() const { return entry_.name; }
+  const proto::ModuleListEntry* entry() const { return &entry_; }
+
+  void Update(const proto::ModuleListEntry* entry);
+
+ private:
+  System* system_ = nullptr;
+  bool is_dead_ = false;
+  proto::ModuleListEntry entry_ = {0};
+  proto::ModuleListEntry temp_entry_ = {0};
+};
+
+}  // namespace model
+}  // namespace ui
+}  // namespace debug
+}  // namespace xe
+
+#endif  // XENIA_DEBUG_UI_MODEL_MODULE_H_
diff --git a/src/xenia/debug/ui/model/system.cc b/src/xenia/debug/ui/model/system.cc
new file mode 100644
index 000000000..3d15782cf
--- /dev/null
+++ b/src/xenia/debug/ui/model/system.cc
@@ -0,0 +1,127 @@
+/**
+ ******************************************************************************
+ * Xenia : Xbox 360 Emulator Research Project                                 *
+ ******************************************************************************
+ * Copyright 2015 Ben Vanik. All rights reserved.                             *
+ * Released under the BSD license - see LICENSE in the root for more details. *
+ ******************************************************************************
+ */
+
+#include "xenia/debug/ui/model/system.h"
+
+#include <unordered_set>
+
+namespace xe {
+namespace debug {
+namespace ui {
+namespace model {
+
+using namespace xe::debug::proto;
+
+System::System(xe::ui::Loop* loop, client::xdp::XdpClient* client)
+    : loop_(loop), client_(client) {}
+
+ExecutionState System::execution_state() {
+  std::lock_guard<std::recursive_mutex> lock(mutex_);
+  return client_->execution_state();
+}
+
+std::vector<Module*> System::modules() {
+  std::lock_guard<std::recursive_mutex> lock(mutex_);
+  std::vector<Module*> result;
+  for (auto& module : modules_) {
+    result.push_back(module.get());
+  }
+  return result;
+}
+
+std::vector<Thread*> System::threads() {
+  std::lock_guard<std::recursive_mutex> lock(mutex_);
+  std::vector<Thread*> result;
+  for (auto& thread : threads_) {
+    result.push_back(thread.get());
+  }
+  return result;
+}
+
+Module* System::GetModuleByHandle(uint32_t module_handle) {
+  std::lock_guard<std::recursive_mutex> lock(mutex_);
+  auto it = modules_by_handle_.find(module_handle);
+  return it != modules_by_handle_.end() ? it->second : nullptr;
+}
+
+Thread* System::GetThreadByHandle(uint32_t thread_handle) {
+  std::lock_guard<std::recursive_mutex> lock(mutex_);
+  auto it = threads_by_handle_.find(thread_handle);
+  return it != threads_by_handle_.end() ? it->second : nullptr;
+}
+
+void System::OnExecutionStateChanged(ExecutionState execution_state) {
+  loop_->Post([this]() {
+    std::lock_guard<std::recursive_mutex> lock(mutex_);
+    on_execution_state_changed();
+  });
+}
+
+void System::OnModulesUpdated(std::vector<const ModuleListEntry*> entries) {
+  {
+    std::lock_guard<std::recursive_mutex> lock(mutex_);
+    std::unordered_set<uint32_t> extra_modules;
+    for (size_t i = 0; i < modules_.size(); ++i) {
+      extra_modules.emplace(modules_[i]->module_handle());
+    }
+    for (auto entry : entries) {
+      auto existing_module = modules_by_handle_.find(entry->module_handle);
+      if (existing_module == modules_by_handle_.end()) {
+        auto module = std::make_unique<Module>(this);
+        module->Update(entry);
+        modules_by_handle_.emplace(entry->module_handle, module.get());
+        modules_.emplace_back(std::move(module));
+      } else {
+        existing_module->second->Update(entry);
+        extra_modules.erase(existing_module->first);
+      }
+    }
+    for (auto module_handle : extra_modules) {
+      modules_by_handle_[module_handle]->set_dead(true);
+    }
+  }
+  loop_->Post([this]() {
+    std::lock_guard<std::recursive_mutex> lock(mutex_);
+    on_modules_updated();
+  });
+}
+
+void System::OnThreadsUpdated(std::vector<const ThreadListEntry*> entries) {
+  {
+    std::lock_guard<std::recursive_mutex> lock(mutex_);
+    std::unordered_set<uint32_t> extra_threads;
+    for (size_t i = 0; i < threads_.size(); ++i) {
+      extra_threads.emplace(threads_[i]->thread_handle());
+    }
+    for (auto entry : entries) {
+      auto existing_thread = threads_by_handle_.find(entry->thread_handle);
+      if (existing_thread == threads_by_handle_.end()) {
+        auto thread = std::make_unique<Thread>(this);
+        thread->Update(entry);
+        threads_by_handle_.emplace(entry->thread_handle, thread.get());
+        threads_.emplace_back(std::move(thread));
+      } else {
+        existing_thread->second->Update(entry);
+        extra_threads.erase(existing_thread->first);
+      }
+    }
+    for (auto thread_handle : extra_threads) {
+      modules_by_handle_[thread_handle]->set_dead(true);
+    }
+  }
+  loop_->Post([this]() {
+    std::lock_guard<std::recursive_mutex> lock(mutex_);
+    on_threads_updated();
+  });
+}
+
+}  // namespace model
+}  // namespace ui
+}  // namespace debug
+}  // namespace xe
diff --git a/src/xenia/debug/ui/model/system.h b/src/xenia/debug/ui/model/system.h
new file mode 100644
index 000000000..00c436ac2
--- /dev/null
+++ b/src/xenia/debug/ui/model/system.h
@@ -0,0 +1,74 @@
+/**
+ ******************************************************************************
+ * Xenia : Xbox 360 Emulator Research Project                                 *
+ ******************************************************************************
+ * Copyright 2015 Ben Vanik. All rights reserved.                             *
+ * Released under the BSD license - see LICENSE in the root for more details. *
+ ******************************************************************************
+ */
+
+#ifndef XENIA_DEBUG_UI_MODEL_SYSTEM_H_
+#define XENIA_DEBUG_UI_MODEL_SYSTEM_H_
+
+#include <cstdint>
+#include <memory>
+#include <mutex>
+#include <unordered_map>
+#include <vector>
+
+#include "xenia/base/delegate.h"
+#include "xenia/debug/client/xdp/xdp_client.h"
+#include "xenia/debug/ui/model/function.h"
+#include "xenia/debug/ui/model/module.h"
+#include "xenia/debug/ui/model/thread.h"
+#include "xenia/ui/loop.h"
+
+namespace xe {
+namespace debug {
+namespace ui {
+namespace model {
+
+using xe::debug::client::xdp::ExecutionState;
+
+class System : public client::xdp::ClientListener {
+ public:
+  System(xe::ui::Loop* loop, client::xdp::XdpClient* client);
+
+  xe::ui::Loop* loop() const { return loop_; }
+  client::xdp::XdpClient* client() const { return client_; }
+
+  ExecutionState execution_state();
+
+  std::vector<Module*> modules();
+  std::vector<Thread*> threads();
+
+  Module* GetModuleByHandle(uint32_t module_handle);
+  Thread* GetThreadByHandle(uint32_t thread_handle);
+
+  Delegate<void> on_execution_state_changed;
+  Delegate<void> on_modules_updated;
+  Delegate<void> on_threads_updated;
+
+ private:
+  void OnExecutionStateChanged(ExecutionState execution_state) override;
+  void OnModulesUpdated(
+      std::vector<const proto::ModuleListEntry*> entries) override;
+  void OnThreadsUpdated(
+      std::vector<const proto::ThreadListEntry*> entries) override;
+
+  xe::ui::Loop* loop_ = nullptr;
+  client::xdp::XdpClient* client_ = nullptr;
+
+  std::recursive_mutex mutex_;
+  std::vector<std::unique_ptr<Module>> modules_;
+  std::unordered_map<uint32_t, Module*> modules_by_handle_;
+  std::vector<std::unique_ptr<Thread>> threads_;
+  std::unordered_map<uint32_t, Thread*> threads_by_handle_;
+};
+
+}  // namespace model
+}  // namespace ui
+}  // namespace debug
+}  // namespace xe
+
+#endif  // XENIA_DEBUG_UI_MODEL_SYSTEM_H_
diff --git a/src/xenia/debug/ui/model/thread.cc b/src/xenia/debug/ui/model/thread.cc
new file mode 100644
index 000000000..0635acd0b
--- /dev/null
+++ b/src/xenia/debug/ui/model/thread.cc
@@ -0,0 +1,40 @@
+/**
+ ******************************************************************************
+ * Xenia : Xbox 360 Emulator Research Project                                 *
+ ******************************************************************************
+ * Copyright 2015 Ben Vanik. All rights reserved.                             *
+ * Released under the BSD license - see LICENSE in the root for more details. *
+ ******************************************************************************
+ */
+
+#include "xenia/debug/ui/model/thread.h"
+
+#include "xenia/debug/ui/model/system.h"
+
+namespace xe {
+namespace debug {
+namespace ui {
+namespace model {
+
+std::string Thread::to_string() {
+  std::string value = entry_.name;
+  if (is_host_thread()) {
+    value += " (host)";
+  }
+  return value;
+}
+
+void Thread::Update(const proto::ThreadListEntry* entry) {
+  if (!entry_.thread_handle) {
+    std::memcpy(&entry_, entry, sizeof(entry_));
+  } else {
+    std::memcpy(&temp_entry_, entry, sizeof(temp_entry_));
+    system_->loop()->Post(
+        [this]() { std::memcpy(&entry_, &temp_entry_, sizeof(temp_entry_)); });
+  }
+}
+
+}  // namespace model
+}  // namespace ui
+}  // namespace debug
+}  // namespace xe
diff --git a/src/xenia/debug/ui/model/thread.h b/src/xenia/debug/ui/model/thread.h
new file mode 100644
index 000000000..f60ddd5d6
--- /dev/null
+++ b/src/xenia/debug/ui/model/thread.h
@@ -0,0 +1,54 @@
+/**
+ ******************************************************************************
+ * Xenia : Xbox 360 Emulator Research Project                                 *
+ ******************************************************************************
+ * Copyright 2015 Ben Vanik. All rights reserved.                             *
+ * Released under the BSD license - see LICENSE in the root for more details. *
+ ******************************************************************************
+ */
+
+#ifndef XENIA_DEBUG_UI_MODEL_THREAD_H_
+#define XENIA_DEBUG_UI_MODEL_THREAD_H_
+
+#include <cstdint>
+#include <string>
+
+#include "xenia/debug/proto/xdp_protocol.h"
+
+namespace xe {
+namespace debug {
+namespace ui {
+namespace model {
+
+class System;
+
+class Thread {
+ public:
+  Thread(System* system) : system_(system) {}
+
+  bool is_dead() const { return is_dead_; }
+  void set_dead(bool is_dead) { is_dead_ = is_dead; }
+
+  uint32_t thread_handle() const { return entry_.thread_handle; }
+  uint32_t thread_id() const { return entry_.thread_id; }
+  bool is_host_thread() const { return entry_.is_host_thread; }
+  std::string name() const { return entry_.name; }
+  const proto::ThreadListEntry* entry() const { return &entry_; }
+
+  std::string to_string();
+
+  void Update(const proto::ThreadListEntry* entry);
+
+ private:
+  System* system_ = nullptr;
+  bool is_dead_ = false;
+  proto::ThreadListEntry entry_ = {0};
+  proto::ThreadListEntry temp_entry_ = {0};
+};
+
+}  // namespace model
+}  // namespace ui
+}  // namespace debug
+}  // namespace xe
+
+#endif  // XENIA_DEBUG_UI_MODEL_THREAD_H_
diff --git a/src/xenia/debug/ui/view.h b/src/xenia/debug/ui/view.h
index fb36ae6d3..9105bedb4 100644
--- a/src/xenia/debug/ui/view.h
+++ b/src/xenia/debug/ui/view.h
@@ -14,6 +14,8 @@
 #include <string>
 
 #include "el/elements.h"
+#include "el/event_handler.h"
+#include "xenia/debug/ui/application.h"
 
 namespace xe {
 namespace debug {
@@ -25,14 +27,21 @@ class View {
 
   std::string name() const { return name_; }
   el::LayoutBox* root_element() { return &root_element_; }
+  xe::ui::Loop* loop() const { return Application::current()->loop(); }
+  client::xdp::XdpClient* client() const { return client_; }
+  model::System* system() const { return Application::current()->system(); }
 
   virtual el::Element* BuildUI() = 0;
 
+  virtual void Setup(xe::debug::client::xdp::XdpClient* client) = 0;
+
  protected:
   View(std::string name) : name_(name) {}
 
   std::string name_;
   el::LayoutBox root_element_;
+  std::unique_ptr<el::EventHandler> handler_;
+  xe::debug::client::xdp::XdpClient* client_ = nullptr;
 };
 
 }  // namespace ui
diff --git a/src/xenia/debug/ui/views/cpu/cpu_view.cc b/src/xenia/debug/ui/views/cpu/cpu_view.cc
index cf634ebf3..a8e5169d1 100644
--- a/src/xenia/debug/ui/views/cpu/cpu_view.cc
+++ b/src/xenia/debug/ui/views/cpu/cpu_view.cc
@@ -16,6 +16,8 @@ namespace ui {
 namespace views {
 namespace cpu {
 
+using namespace xe::debug::client::xdp;
+
 CpuView::CpuView() : View("CPU") {}
 
 CpuView::~CpuView() = default;
@@ -29,22 +31,13 @@ el::Element* CpuView::BuildUI() {
           .gravity(Gravity::kAll)
           .distribution(LayoutDistribution::kAvailable)
           .axis(Axis::kY)
-          .child(
-              LayoutBoxNode()
-                  .gravity(Gravity::kTop | Gravity::kLeftRight)
-                  .distribution(LayoutDistribution::kAvailable)
-                  .axis(Axis::kX)
-                  .skin("button_group")
-                  .child(ButtonNode("?"))
-                  .child(
-                      DropDownButtonNode().item("Module").item("Module").item(
-                          "Module")))
-          .child(ListBoxNode()
-                     .gravity(Gravity::kAll)
-                     .item("fn")
-                     .item("fn")
-                     .item("fn")
-                     .item("fn"))
+          .child(LayoutBoxNode()
+                     .gravity(Gravity::kTop | Gravity::kLeftRight)
+                     .distribution(LayoutDistribution::kAvailable)
+                     .axis(Axis::kX)
+                     .skin("button_group")
+                     .child(DropDownButtonNode().id("module_dropdown")))
+          .child(ListBoxNode().id("function_listbox").gravity(Gravity::kAll))
           .child(LayoutBoxNode()
                      .gravity(Gravity::kBottom | Gravity::kLeftRight)
                      .distribution(LayoutDistribution::kAvailable)
@@ -102,10 +95,9 @@ el::Element* CpuView::BuildUI() {
                   .distribution(LayoutDistribution::kGravity)
                   .distribution_position(LayoutDistributionPosition::kLeftTop)
                   .axis(Axis::kX)
-                  .child(ButtonNode("button"))
-                  .child(ButtonNode("button"))
-                  .child(ButtonNode("button")))
+                  .child(DropDownButtonNode().id("thread_dropdown")))
           .child(LayoutBoxNode()
+                     .id("source_content")
                      .gravity(Gravity::kAll)
                      .distribution(LayoutDistribution::kAvailable)
                      .child(SplitContainerNode()
@@ -144,9 +136,91 @@ el::Element* CpuView::BuildUI() {
   root_element_.GetElementsById({
       //
   });
+  handler_ = std::make_unique<el::EventHandler>(&root_element_);
+
+  handler_->Listen(el::EventType::kChanged, TBIDC("module_dropdown"),
+                   [this](const el::Event& ev) {
+                     UpdateFunctionList();
+                     return true;
+                   });
+
   return &root_element_;
 }
 
+void CpuView::Setup(XdpClient* client) {
+  client_ = client;
+
+  system()->on_execution_state_changed.AddListener(
+      [this]() { UpdateElementState(); });
+  system()->on_modules_updated.AddListener([this]() { UpdateModuleList(); });
+  system()->on_threads_updated.AddListener([this]() { UpdateThreadList(); });
+}
+
+void CpuView::UpdateElementState() {
+  root_element_.GetElementsById({
+      //
+  });
+}
+
+void CpuView::UpdateModuleList() {
+  el::DropDownButton* module_dropdown;
+  root_element_.GetElementsById({
+      {TBIDC("module_dropdown"), &module_dropdown},
+  });
+  auto module_items = module_dropdown->default_source();
+  auto modules = system()->modules();
+  bool is_first = module_items->size() == 0;
+  for (size_t i = module_items->size(); i < modules.size(); ++i) {
+    auto module = modules[i];
+    auto item = std::make_unique<el::GenericStringItem>(module->name());
+    item->id = module->module_handle();
+    module_items->push_back(std::move(item));
+  }
+  if (is_first) {
+    module_dropdown->set_value(int(module_items->size() - 1));
+  }
+}
+
+void CpuView::UpdateFunctionList() {
+  el::DropDownButton* module_dropdown;
+  el::ListBox* function_listbox;
+  root_element_.GetElementsById({
+      {TBIDC("module_dropdown"), &module_dropdown},
+      {TBIDC("function_listbox"), &function_listbox},
+  });
+  auto module_handle = module_dropdown->selected_item_id();
+  auto module = system()->GetModuleByHandle(module_handle);
+  if (!module) {
+    function_listbox->default_source()->clear();
+    return;
+  }
+  // TODO(benvanik): fetch list.
+}
+
+void CpuView::UpdateThreadList() {
+  el::DropDownButton* thread_dropdown;
+  root_element_.GetElementsById({
+      {TBIDC("thread_dropdown"), &thread_dropdown},
+  });
+  auto thread_items = thread_dropdown->default_source();
+  auto threads = system()->threads();
+  bool is_first = thread_items->size() == 0;
+  for (size_t i = 0; i < thread_items->size(); ++i) {
+    auto thread = threads[i];
+    auto item = thread_items->at(i);
+    item->str = thread->to_string();
+  }
+  for (size_t i = thread_items->size(); i < threads.size(); ++i) {
+    auto thread = threads[i];
+    auto item = std::make_unique<el::GenericStringItem>(thread->to_string());
+    item->id = thread->thread_handle();
+    thread_items->push_back(std::move(item));
+  }
+  if (is_first) {
+    thread_dropdown->set_value(int(thread_items->size() - 1));
+  }
+}
+
 }  // namespace cpu
 }  // namespace views
 }  // namespace ui
diff --git a/src/xenia/debug/ui/views/cpu/cpu_view.h b/src/xenia/debug/ui/views/cpu/cpu_view.h
index 1962eee77..b727fc492 100644
--- a/src/xenia/debug/ui/views/cpu/cpu_view.h
+++ b/src/xenia/debug/ui/views/cpu/cpu_view.h
@@ -28,7 +28,13 @@ class CpuView : public View {
 
   el::Element* BuildUI() override;
 
+  void Setup(xe::debug::client::xdp::XdpClient* client) override;
+
  protected:
+  void UpdateElementState();
+  void UpdateModuleList();
+  void UpdateFunctionList();
+  void UpdateThreadList();
 };
 
 }  // namespace cpu
diff --git a/src/xenia/debug/ui/views/gpu/gpu_view.cc b/src/xenia/debug/ui/views/gpu/gpu_view.cc
index f91dbbbdb..382478b3d 100644
--- a/src/xenia/debug/ui/views/gpu/gpu_view.cc
+++ b/src/xenia/debug/ui/views/gpu/gpu_view.cc
@@ -32,9 +32,14 @@ el::Element* GpuView::BuildUI() {
   root_element_.GetElementsById({
       //
   });
+  handler_ = std::make_unique<el::EventHandler>(&root_element_);
   return &root_element_;
 }
 
+void GpuView::Setup(xe::debug::client::xdp::XdpClient* client) {
+  //
+}
+
 }  // namespace gpu
 }  // namespace views
 }  // namespace ui
diff --git a/src/xenia/debug/ui/views/gpu/gpu_view.h b/src/xenia/debug/ui/views/gpu/gpu_view.h
index d53263a92..9d4f5c136 100644
--- a/src/xenia/debug/ui/views/gpu/gpu_view.h
+++ b/src/xenia/debug/ui/views/gpu/gpu_view.h
@@ -28,6 +28,8 @@ class GpuView : public View {
 
   el::Element* BuildUI() override;
 
+  void Setup(xe::debug::client::xdp::XdpClient* client) override;
+
  protected:
 };
 
diff --git a/src/xenia/kernel/kernel_state.cc b/src/xenia/kernel/kernel_state.cc
index cb97337da..ee865a423 100644
--- a/src/xenia/kernel/kernel_state.cc
+++ b/src/xenia/kernel/kernel_state.cc
@@ -353,7 +353,7 @@ void KernelState::TerminateTitle(bool from_guest_thread) {
 
   // Second: Kill all guest threads.
   for (auto it = threads_by_id_.begin(); it != threads_by_id_.end();) {
-    if (it->second->guest_thread()) {
+    if (it->second->is_guest_thread()) {
       auto thread = it->second;
 
       if (from_guest_thread && XThread::IsInThread(thread)) {
@@ -362,7 +362,7 @@ void KernelState::TerminateTitle(bool from_guest_thread) {
         continue;
       }
 
-      if (thread->running()) {
+      if (thread->is_running()) {
         thread->Terminate(0);
       }
 
@@ -457,6 +457,10 @@ void KernelState::OnThreadExit(XThread* thread) {
                            xe::countof(args));
     }
   }
+
+  if (emulator()->debugger()) {
+    emulator()->debugger()->OnThreadExit(thread);
+  }
 }
 
 object_ref<XThread> KernelState::GetThreadByID(uint32_t thread_id) {
diff --git a/src/xenia/kernel/objects/xthread.cc b/src/xenia/kernel/objects/xthread.cc
index 0b3828439..4af7524ff 100644
--- a/src/xenia/kernel/objects/xthread.cc
+++ b/src/xenia/kernel/objects/xthread.cc
@@ -19,6 +19,7 @@
 #include "xenia/base/mutex.h"
 #include "xenia/base/threading.h"
 #include "xenia/cpu/processor.h"
+#include "xenia/emulator.h"
 #include "xenia/kernel/kernel_state.h"
 #include "xenia/kernel/native_list.h"
 #include "xenia/kernel/objects/xevent.h"
@@ -70,6 +71,10 @@ XThread::~XThread() {
   // Unregister first to prevent lookups while deleting.
   kernel_state_->UnregisterThread(this);
 
+  if (emulator()->debugger()) {
+    emulator()->debugger()->OnThreadDestroyed(this);
+  }
+
   delete apc_list_;
 
   thread_.reset();
@@ -329,6 +334,10 @@ X_STATUS XThread::Create() {
     thread_->set_priority(creation_params_.creation_flags & 0x20 ? 1 : 0);
   }
 
+  if (emulator()->debugger()) {
+    emulator()->debugger()->OnThreadCreated(this);
+  }
+
   if ((creation_params_.creation_flags & X_CREATE_SUSPENDED) == 0) {
     // Start the thread now that we're all setup.
     thread_->Resume();
@@ -344,17 +353,21 @@ X_STATUS XThread::Exit(int exit_code) {
   // TODO(benvanik); dispatch events? waiters? etc?
   RundownAPCs();
 
+  // Set exit code.
+  X_KTHREAD* thread = guest_object<X_KTHREAD>();
+  thread->header.signal_state = 1;
+  thread->exit_status = exit_code;
+
   kernel_state()->OnThreadExit(this);
 
+  if (emulator()->debugger()) {
+    emulator()->debugger()->OnThreadExit(this);
+  }
+
   // NOTE: unless PlatformExit fails, expect it to never return!
   current_thread_tls = nullptr;
   xe::Profiler::ThreadExit();
 
-  // Set exit code
-  X_KTHREAD* thread = guest_object<X_KTHREAD>();
-  thread->header.signal_state = 1;
-  thread->exit_status = exit_code;
-
   running_ = false;
   Release();
   ReleaseHandle();
@@ -367,11 +380,15 @@ X_STATUS XThread::Exit(int exit_code) {
 X_STATUS XThread::Terminate(int exit_code) {
   // TODO: Inform the profiler that this thread is exiting.
 
-  // Set exit code
+  // Set exit code.
   X_KTHREAD* thread = guest_object<X_KTHREAD>();
   thread->header.signal_state = 1;
   thread->exit_status = exit_code;
 
+  if (emulator()->debugger()) {
+    emulator()->debugger()->OnThreadExit(this);
+  }
+
   running_ = false;
   Release();
   ReleaseHandle();
diff --git a/src/xenia/kernel/objects/xthread.h b/src/xenia/kernel/objects/xthread.h
index d052b53a0..f770501c6 100644
--- a/src/xenia/kernel/objects/xthread.h
+++ b/src/xenia/kernel/objects/xthread.h
@@ -103,6 +103,14 @@ static_assert_size(X_KTHREAD, 0xAB0);
 
 class XThread : public XObject {
  public:
+  struct CreationParams {
+    uint32_t stack_size;
+    uint32_t xapi_thread_startup;
+    uint32_t start_address;
+    uint32_t start_context;
+    uint32_t creation_flags;
+  };
+
   XThread(KernelState* kernel_state, uint32_t stack_size,
           uint32_t xapi_thread_startup, uint32_t start_address,
           uint32_t start_context, uint32_t creation_flags, bool guest_thread);
@@ -114,10 +122,11 @@ class XThread : public XObject {
   static uint32_t GetCurrentThreadHandle();
   static uint32_t GetCurrentThreadId();
 
+  const CreationParams* creation_params() const { return &creation_params_; }
   uint32_t tls_ptr() const { return tls_address_; }
   uint32_t pcr_ptr() const { return pcr_address_; }
-  bool guest_thread() const { return guest_thread_; }
-  bool running() const { return running_; }
+  bool is_guest_thread() const { return guest_thread_; }
+  bool is_running() const { return running_; }
 
   cpu::ThreadState* thread_state() const { return thread_state_; }
   uint32_t thread_id() const { return thread_id_; }
@@ -163,13 +172,7 @@ class XThread : public XObject {
   void DeliverAPCs();
   void RundownAPCs();
 
-  struct {
-    uint32_t stack_size;
-    uint32_t xapi_thread_startup;
-    uint32_t start_address;
-    uint32_t start_context;
-    uint32_t creation_flags;
-  } creation_params_ = {0};
+  CreationParams creation_params_ = {0};
 
   uint32_t thread_id_ = 0;
   std::unique_ptr<xe::threading::Thread> thread_;