diff --git a/CMakeLists.txt b/CMakeLists.txt
index 0244908c..beca46ea 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -17,7 +17,7 @@ add_executable(cquery "")
 ### Compile options
 
 # CMake default compile flags:
-# MSVC + Clang(Windows):  
+# MSVC + Clang(Windows):
 #   debug: /MDd /Zi /Ob0 /Od /RTC1
 #   release: /MD /O2 /Ob2 /DNDEBUG
 # GCC + Clang(Linux):
@@ -32,15 +32,15 @@ set_property(TARGET cquery PROPERTY CXX_EXTENSIONS OFF)
 
 if(${CMAKE_SYSTEM_NAME} STREQUAL Windows)
   # Common MSVC/Clang(Windows) options
-  target_compile_options(cquery PRIVATE 
-                         /nologo 
-                         /EHsc 
+  target_compile_options(cquery PRIVATE
+                         /nologo
+                         /EHsc
                          /W3 # roughly -Wall
                          /wd4996 # disable loguru unsafe warnings
-                         /wd4722 # ignores warning C4722 
+                         /wd4722 # ignores warning C4722
                                  # (destructor never returns) in loguru
-                         /wd4267 # ignores warning C4267 
-                                 # (conversion from 'size_t' to 'type'), 
+                         /wd4267 # ignores warning C4267
+                                 # (conversion from 'size_t' to 'type'),
                                  # roughly -Wno-sign-compare
                          /wd4800
                          $<$<CONFIG:Debug>:/FS>
@@ -48,8 +48,8 @@ if(${CMAKE_SYSTEM_NAME} STREQUAL Windows)
 else()
   # Common GCC/Clang(Linux) options
   target_compile_options(cquery PRIVATE
-                         -Wall 
-                         -Wno-sign-compare 
+                         -Wall
+                         -Wno-sign-compare
                          )
 
   if(${CMAKE_CXX_COMPILER_ID} STREQUAL GNU)
@@ -57,14 +57,14 @@ else()
   endif()
 
   if(${CMAKE_CXX_COMPILER_ID} STREQUAL Clang)
-    target_compile_options(cquery PRIVATE 
+    target_compile_options(cquery PRIVATE
                            $<$<CONFIG:Debug>:-fno-limit-debug-info>)
   endif()
 
   if(CLANG_CXX)
     # -Wno-comment: include/clang/Format/Format.h error: multi-line comment
     # -fno-rtti: # Without -fno-rtti, some Clang C++ functions may report
-    # `undefined references to typeinfo` 
+    # `undefined references to typeinfo`
     target_compile_options(cquery PRIVATE -Wno-comment -fno-rtti)
   endif()
 
@@ -148,21 +148,21 @@ install(TARGETS cquery RUNTIME DESTINATION bin)
 if(NOT SYSTEM_CLANG AND NOT ${CMAKE_SYSTEM_NAME} STREQUAL Windows)
 
   if(${CMAKE_SYSTEM_NAME} MATCHES Linux|FreeBSD)
-    set_property(TARGET cquery APPEND PROPERTY 
+    set_property(TARGET cquery APPEND PROPERTY
                  INSTALL_RPATH $ORIGIN/../lib)
   elseif(${CMAKE_SYSTEM_NAME} STREQUAL Darwin)
-    set_property(TARGET cquery APPEND PROPERTY 
-                 INSTALL_RPATH @loader_path/../lib)  
+    set_property(TARGET cquery APPEND PROPERTY
+                 INSTALL_RPATH @loader_path/../lib)
   endif()
 
-  file(GLOB LIBCLANG_PLUS_SYMLINKS 
+  file(GLOB LIBCLANG_PLUS_SYMLINKS
        ${DOWNLOADED_CLANG_DIR}/lib/libclang.[so,dylib]*)
   install(FILES ${LIBCLANG_PLUS_SYMLINKS} DESTINATION lib)
 endif()
 
 ### Sources
 
-target_sources(cquery PRIVATE third_party/siphash.cc)           
+target_sources(cquery PRIVATE third_party/siphash.cc)
 
 target_sources(cquery PRIVATE
                src/cache_manager.cc
@@ -183,7 +183,7 @@ target_sources(cquery PRIVATE
                src/import_manager.cc
                src/import_pipeline.cc
                src/include_complete.cc
-               src/ipc.cc
+               src/method.cc
                src/lex_utils.cc
                src/lsp_diagnostic.cc
                src/lsp.cc
diff --git a/src/command_line.cc b/src/command_line.cc
index 6229ad33..14bd2c35 100644
--- a/src/command_line.cc
+++ b/src/command_line.cc
@@ -137,7 +137,7 @@ bool QueryDbMainLoop(Config* config,
                      CodeCompleteCache* non_global_code_complete_cache,
                      CodeCompleteCache* signature_cache) {
   auto* queue = QueueManager::instance();
-  std::vector<std::unique_ptr<BaseIpcMessage>> messages =
+  std::vector<std::unique_ptr<InMessage>> messages =
       queue->for_querydb.DequeueAll();
   bool did_work = messages.size();
   for (auto& message : messages) {
@@ -281,7 +281,7 @@ void LaunchStdinLoop(Config* config,
   WorkThread::StartThread("stdin", [request_times]() {
     auto* queue = QueueManager::instance();
     while (true) {
-      std::unique_ptr<BaseIpcMessage> message;
+      std::unique_ptr<InMessage> message;
       optional<std::string> err =
           MessageRegistry::instance()->ReadMessageFromStdin(&message);
 
diff --git a/src/lsp.cc b/src/lsp.cc
index 38fdee6f..07daebe6 100644
--- a/src/lsp.cc
+++ b/src/lsp.cc
@@ -123,7 +123,7 @@ optional<char> ReadCharFromStdinBlocking() {
 }
 
 optional<std::string> MessageRegistry::ReadMessageFromStdin(
-    std::unique_ptr<BaseIpcMessage>* message) {
+    std::unique_ptr<InMessage>* message) {
   optional<std::string> content =
       ReadJsonRpcContentFrom(&ReadCharFromStdinBlocking);
   if (!content) {
@@ -141,7 +141,7 @@ optional<std::string> MessageRegistry::ReadMessageFromStdin(
 
 optional<std::string> MessageRegistry::Parse(
     Reader& visitor,
-    std::unique_ptr<BaseIpcMessage>* message) {
+    std::unique_ptr<InMessage>* message) {
   if (!visitor.HasMember("jsonrpc") ||
       std::string(visitor["jsonrpc"]->GetString()) != "2.0") {
     LOG_S(FATAL) << "Bad or missing jsonrpc version";
diff --git a/src/lsp.h b/src/lsp.h
index e0d70cb5..88e06358 100644
--- a/src/lsp.h
+++ b/src/lsp.h
@@ -1,7 +1,7 @@
 #pragma once
 
 #include "config.h"
-#include "ipc.h"
+#include "method.h"
 #include "serializer.h"
 #include "utils.h"
 
@@ -32,13 +32,13 @@ struct MessageRegistry {
   static MessageRegistry* instance();
 
   using Allocator =
-      std::function<void(Reader& visitor, std::unique_ptr<BaseIpcMessage>*)>;
+      std::function<void(Reader& visitor, std::unique_ptr<InMessage>*)>;
   std::unordered_map<std::string, Allocator> allocators;
 
   optional<std::string> ReadMessageFromStdin(
-      std::unique_ptr<BaseIpcMessage>* message);
+      std::unique_ptr<InMessage>* message);
   optional<std::string> Parse(Reader& visitor,
-                              std::unique_ptr<BaseIpcMessage>* message);
+                              std::unique_ptr<InMessage>* message);
 };
 
 template <typename T>
@@ -47,7 +47,7 @@ struct MessageRegistryRegister {
     T dummy;
     std::string method_name = dummy.GetMethodType();
     MessageRegistry::instance()->allocators[method_name] =
-        [](Reader& visitor, std::unique_ptr<BaseIpcMessage>* message) {
+        [](Reader& visitor, std::unique_ptr<InMessage>* message) {
           *message = std::make_unique<T>();
           // Reflect may throw and *message will be partially deserialized.
           Reflect(visitor, static_cast<T&>(**message));
diff --git a/src/message_handler.h b/src/message_handler.h
index a68990f4..e838bfb1 100644
--- a/src/message_handler.h
+++ b/src/message_handler.h
@@ -1,7 +1,7 @@
 #pragma once
 
-#include "ipc.h"
 #include "lsp.h"
+#include "method.h"
 #include "query.h"
 
 #include <optional.h>
@@ -87,7 +87,7 @@ struct MessageHandler {
   CodeCompleteCache* signature_cache = nullptr;
 
   virtual MethodType GetMethodType() const = 0;
-  virtual void Run(std::unique_ptr<BaseIpcMessage> message) = 0;
+  virtual void Run(std::unique_ptr<InMessage> message) = 0;
 
   static std::vector<MessageHandler*>* message_handlers;
 
@@ -100,7 +100,7 @@ struct BaseMessageHandler : MessageHandler {
   virtual void Run(TMessage* message) = 0;
 
   // MessageHandler:
-  void Run(std::unique_ptr<BaseIpcMessage> message) override {
+  void Run(std::unique_ptr<InMessage> message) override {
     Run(static_cast<TMessage*>(message.get()));
   }
 };
diff --git a/src/messages/cquery_base.cc b/src/messages/cquery_base.cc
index 05963f85..c3831433 100644
--- a/src/messages/cquery_base.cc
+++ b/src/messages/cquery_base.cc
@@ -6,7 +6,7 @@ namespace {
 
 MethodType kMethodType = "$cquery/base";
 
-struct In_CqueryBase : public RequestMessage {
+struct In_CqueryBase : public RequestInMessage {
   MethodType GetMethodType() const override { return kMethodType; }
 
   lsTextDocumentPositionParams params;
diff --git a/src/messages/cquery_call_hierarchy.cc b/src/messages/cquery_call_hierarchy.cc
index 7143680b..9f6e576f 100644
--- a/src/messages/cquery_call_hierarchy.cc
+++ b/src/messages/cquery_call_hierarchy.cc
@@ -20,7 +20,7 @@ bool operator&(CallType lhs, CallType rhs) {
   return uint8_t(lhs) & uint8_t(rhs);
 }
 
-struct In_CqueryCallHierarchy : public RequestMessage {
+struct In_CqueryCallHierarchy : public RequestInMessage {
   MethodType GetMethodType() const override { return kMethodType; }
 
   struct Params {
diff --git a/src/messages/cquery_callers.cc b/src/messages/cquery_callers.cc
index 4214253f..701aefbe 100644
--- a/src/messages/cquery_callers.cc
+++ b/src/messages/cquery_callers.cc
@@ -5,7 +5,7 @@
 namespace {
 MethodType kMethodType = "$cquery/callers";
 
-struct In_CqueryCallers : public RequestMessage {
+struct In_CqueryCallers : public RequestInMessage {
   MethodType GetMethodType() const override { return kMethodType; }
   lsTextDocumentPositionParams params;
 };
diff --git a/src/messages/cquery_derived.cc b/src/messages/cquery_derived.cc
index e43da912..9700e88f 100644
--- a/src/messages/cquery_derived.cc
+++ b/src/messages/cquery_derived.cc
@@ -5,7 +5,7 @@
 namespace {
 MethodType kMethodType = "$cquery/derived";
 
-struct In_CqueryDerived : public RequestMessage {
+struct In_CqueryDerived : public RequestInMessage {
   MethodType GetMethodType() const override { return kMethodType; }
   lsTextDocumentPositionParams params;
 };
diff --git a/src/messages/cquery_did_view.cc b/src/messages/cquery_did_view.cc
index d01f6d95..73da37da 100644
--- a/src/messages/cquery_did_view.cc
+++ b/src/messages/cquery_did_view.cc
@@ -5,7 +5,7 @@
 namespace {
 MethodType kMethodType = "$cquery/textDocumentDidView";
 
-struct In_CqueryTextDocumentDidView : public NotificationMessage {
+struct In_CqueryTextDocumentDidView : public NotificationInMessage {
   MethodType GetMethodType() const override { return kMethodType; }
   struct Params {
     lsDocumentUri textDocumentUri;
diff --git a/src/messages/cquery_file_info.cc b/src/messages/cquery_file_info.cc
index 22db960c..a72612d6 100644
--- a/src/messages/cquery_file_info.cc
+++ b/src/messages/cquery_file_info.cc
@@ -10,7 +10,7 @@ struct lsDocumentSymbolParams {
 };
 MAKE_REFLECT_STRUCT(lsDocumentSymbolParams, textDocument);
 
-struct In_CqueryFileInfo : public RequestMessage {
+struct In_CqueryFileInfo : public RequestInMessage {
   MethodType GetMethodType() const override { return kMethodType; }
   lsDocumentSymbolParams params;
 };
diff --git a/src/messages/cquery_freshen_index.cc b/src/messages/cquery_freshen_index.cc
index 0b7cc073..e52b5236 100644
--- a/src/messages/cquery_freshen_index.cc
+++ b/src/messages/cquery_freshen_index.cc
@@ -15,7 +15,7 @@
 namespace {
 MethodType kMethodType = "$cquery/freshenIndex";
 
-struct In_CqueryFreshenIndex : public NotificationMessage {
+struct In_CqueryFreshenIndex : public NotificationInMessage {
   MethodType GetMethodType() const override { return kMethodType; }
   struct Params {
     bool dependencies = true;
diff --git a/src/messages/cquery_index_file.cc b/src/messages/cquery_index_file.cc
index 0d188ea6..9e106558 100644
--- a/src/messages/cquery_index_file.cc
+++ b/src/messages/cquery_index_file.cc
@@ -8,7 +8,7 @@
 namespace {
 MethodType kMethodType = "$cquery/indexFile";
 
-struct In_CqueryIndexFile : public NotificationMessage {
+struct In_CqueryIndexFile : public NotificationInMessage {
   MethodType GetMethodType() const override { return kMethodType; }
   struct Params {
     std::string path;
diff --git a/src/messages/cquery_inheritance_hierarchy.cc b/src/messages/cquery_inheritance_hierarchy.cc
index 3c024619..17a0b1ba 100644
--- a/src/messages/cquery_inheritance_hierarchy.cc
+++ b/src/messages/cquery_inheritance_hierarchy.cc
@@ -5,7 +5,7 @@
 namespace {
 MethodType kMethodType = "$cquery/inheritanceHierarchy";
 
-struct In_CqueryInheritanceHierarchy : public RequestMessage {
+struct In_CqueryInheritanceHierarchy : public RequestInMessage {
   MethodType GetMethodType() const override { return kMethodType; }
   struct Params {
     // If id+kind are specified, expand a node; otherwise textDocument+position
diff --git a/src/messages/cquery_member_hierarchy.cc b/src/messages/cquery_member_hierarchy.cc
index b4f03763..e98e53d5 100644
--- a/src/messages/cquery_member_hierarchy.cc
+++ b/src/messages/cquery_member_hierarchy.cc
@@ -5,7 +5,7 @@
 namespace {
 MethodType kMethodType = "$cquery/memberHierarchy";
 
-struct In_CqueryMemberHierarchy : public RequestMessage {
+struct In_CqueryMemberHierarchy : public RequestInMessage {
   MethodType GetMethodType() const override { return kMethodType; }
 
   struct Params {
diff --git a/src/messages/cquery_random.cc b/src/messages/cquery_random.cc
index bf7c4668..7bbf0761 100644
--- a/src/messages/cquery_random.cc
+++ b/src/messages/cquery_random.cc
@@ -9,7 +9,7 @@
 namespace {
 MethodType kMethodType = "$cquery/random";
 
-struct In_CqueryRandom : public RequestMessage {
+struct In_CqueryRandom : public RequestInMessage {
   MethodType GetMethodType() const override { return kMethodType; }
 };
 MAKE_REFLECT_STRUCT(In_CqueryRandom, id);
diff --git a/src/messages/cquery_vars.cc b/src/messages/cquery_vars.cc
index 812ec6f0..8ac9816f 100644
--- a/src/messages/cquery_vars.cc
+++ b/src/messages/cquery_vars.cc
@@ -5,7 +5,7 @@
 namespace {
 MethodType kMethodType = "$cquery/vars";
 
-struct In_CqueryVars : public RequestMessage {
+struct In_CqueryVars : public RequestInMessage {
   MethodType GetMethodType() const override { return kMethodType; }
 
   lsTextDocumentPositionParams params;
diff --git a/src/messages/cquery_wait.cc b/src/messages/cquery_wait.cc
index c9109729..3a05df75 100644
--- a/src/messages/cquery_wait.cc
+++ b/src/messages/cquery_wait.cc
@@ -8,7 +8,7 @@
 namespace {
 MethodType kMethodType = "$cquery/wait";
 
-struct In_CqueryWait : public NotificationMessage {
+struct In_CqueryWait : public NotificationInMessage {
   MethodType GetMethodType() const override { return kMethodType; }
 };
 MAKE_REFLECT_EMPTY_STRUCT(In_CqueryWait);
@@ -17,7 +17,7 @@ REGISTER_IN_MESSAGE(In_CqueryWait);
 struct Handler_CqueryWait : MessageHandler {
   MethodType GetMethodType() const override { return kMethodType; }
 
-  void Run(std::unique_ptr<BaseIpcMessage> request) override {
+  void Run(std::unique_ptr<InMessage> request) override {
     // TODO: use status message system here, then run querydb as normal? Maybe
     // this cannot be a normal message, ie, it needs to be re-entrant.
 
diff --git a/src/messages/exit.cc b/src/messages/exit.cc
index d90d80ed..2722dca5 100644
--- a/src/messages/exit.cc
+++ b/src/messages/exit.cc
@@ -3,7 +3,7 @@
 #include <loguru.hpp>
 
 namespace {
-struct In_Exit : public NotificationMessage {
+struct In_Exit : public NotificationInMessage {
   MethodType GetMethodType() const override { return kMethodType_Exit; }
 };
 MAKE_REFLECT_EMPTY_STRUCT(In_Exit);
@@ -12,7 +12,7 @@ REGISTER_IN_MESSAGE(In_Exit);
 struct Handler_Exit : MessageHandler {
   MethodType GetMethodType() const override { return kMethodType_Exit; }
 
-  void Run(std::unique_ptr<BaseIpcMessage> request) override {
+  void Run(std::unique_ptr<InMessage> request) override {
     LOG_S(INFO) << "Exiting; got exit message";
     exit(0);
   }
diff --git a/src/messages/initialize.cc b/src/messages/initialize.cc
index ffbc6115..2edd6ff0 100644
--- a/src/messages/initialize.cc
+++ b/src/messages/initialize.cc
@@ -462,7 +462,7 @@ struct lsInitializeError {
 };
 MAKE_REFLECT_STRUCT(lsInitializeError, retry);
 
-struct In_InitializeRequest : public RequestMessage {
+struct In_InitializeRequest : public RequestInMessage {
   MethodType GetMethodType() const override { return kMethodType; }
 
   lsInitializeParams params;
diff --git a/src/messages/shutdown.cc b/src/messages/shutdown.cc
index f93f4320..5967e239 100644
--- a/src/messages/shutdown.cc
+++ b/src/messages/shutdown.cc
@@ -4,7 +4,7 @@
 namespace {
 MethodType kMethodType = "shutdown";
 
-struct In_Shutdown : public RequestMessage {
+struct In_Shutdown : public RequestInMessage {
   MethodType GetMethodType() const override { return kMethodType; }
 };
 MAKE_REFLECT_STRUCT(In_Shutdown, id);
diff --git a/src/messages/text_document_code_action.cc b/src/messages/text_document_code_action.cc
index 487fbca3..e3913a2f 100644
--- a/src/messages/text_document_code_action.cc
+++ b/src/messages/text_document_code_action.cc
@@ -257,7 +257,7 @@ optional<lsTextEdit> BuildAutoImplementForFunction(QueryDatabase* db,
   return nullopt;
 }
 
-struct In_TextDocumentCodeAction : public RequestMessage {
+struct In_TextDocumentCodeAction : public RequestInMessage {
   MethodType GetMethodType() const override { return kMethodType; }
 
   // Contains additional diagnostic information about the context in which
diff --git a/src/messages/text_document_code_lens.cc b/src/messages/text_document_code_lens.cc
index f735f1bb..903abf11 100644
--- a/src/messages/text_document_code_lens.cc
+++ b/src/messages/text_document_code_lens.cc
@@ -13,7 +13,7 @@ struct lsDocumentCodeLensParams {
 MAKE_REFLECT_STRUCT(lsDocumentCodeLensParams, textDocument);
 
 using TCodeLens = lsCodeLens<lsCodeLensUserData, lsCodeLensCommandArguments>;
-struct In_TextDocumentCodeLens : public RequestMessage {
+struct In_TextDocumentCodeLens : public RequestInMessage {
   MethodType GetMethodType() const override { return kMethodType; }
   lsDocumentCodeLensParams params;
 };
diff --git a/src/messages/text_document_completion.cc b/src/messages/text_document_completion.cc
index 43dc6c8c..d6db3107 100644
--- a/src/messages/text_document_completion.cc
+++ b/src/messages/text_document_completion.cc
@@ -48,7 +48,7 @@ struct lsCompletionParams : lsTextDocumentPositionParams {
 };
 MAKE_REFLECT_STRUCT(lsCompletionParams, textDocument, position, context);
 
-struct In_TextDocumentComplete : public RequestMessage {
+struct In_TextDocumentComplete : public RequestInMessage {
   MethodType GetMethodType() const override { return kMethodType; }
   lsCompletionParams params;
 };
@@ -219,7 +219,7 @@ void FilterAndSortCompletionResponse(
 struct Handler_TextDocumentCompletion : MessageHandler {
   MethodType GetMethodType() const override { return kMethodType; }
 
-  void Run(std::unique_ptr<BaseIpcMessage> message) override {
+  void Run(std::unique_ptr<InMessage> message) override {
     auto request = std::shared_ptr<In_TextDocumentComplete>(
         static_cast<In_TextDocumentComplete*>(message.release()));
 
diff --git a/src/messages/text_document_definition.cc b/src/messages/text_document_definition.cc
index 95410f0e..d7fc869a 100644
--- a/src/messages/text_document_definition.cc
+++ b/src/messages/text_document_definition.cc
@@ -10,7 +10,7 @@
 namespace {
 MethodType kMethodType = "textDocument/definition";
 
-struct In_TextDocumentDefinition : public RequestMessage {
+struct In_TextDocumentDefinition : public RequestInMessage {
   MethodType GetMethodType() const override { return kMethodType; }
   lsTextDocumentPositionParams params;
 };
diff --git a/src/messages/text_document_did_change.cc b/src/messages/text_document_did_change.cc
index fb16e3c3..cf887adb 100644
--- a/src/messages/text_document_did_change.cc
+++ b/src/messages/text_document_did_change.cc
@@ -10,7 +10,7 @@
 namespace {
 MethodType kMethodType = "textDocument/didChange";
 
-struct In_TextDocumentDidChange : public NotificationMessage {
+struct In_TextDocumentDidChange : public NotificationInMessage {
   MethodType GetMethodType() const override { return kMethodType; }
   lsTextDocumentDidChangeParams params;
 };
diff --git a/src/messages/text_document_did_close.cc b/src/messages/text_document_did_close.cc
index e76ee52f..6cf1d3fb 100644
--- a/src/messages/text_document_did_close.cc
+++ b/src/messages/text_document_did_close.cc
@@ -6,7 +6,7 @@
 namespace {
 MethodType kMethodType = "textDocument/didClose";
 
-struct In_TextDocumentDidClose : public NotificationMessage {
+struct In_TextDocumentDidClose : public NotificationInMessage {
   MethodType GetMethodType() const override { return kMethodType; }
   struct Params {
     lsTextDocumentIdentifier textDocument;
diff --git a/src/messages/text_document_did_open.cc b/src/messages/text_document_did_open.cc
index 2b2562d8..770c9bcb 100644
--- a/src/messages/text_document_did_open.cc
+++ b/src/messages/text_document_did_open.cc
@@ -13,7 +13,7 @@ namespace {
 MethodType kMethodType = "textDocument/didOpen";
 
 // Open, view, change, close file
-struct In_TextDocumentDidOpen : public NotificationMessage {
+struct In_TextDocumentDidOpen : public NotificationInMessage {
   MethodType GetMethodType() const override { return kMethodType; }
   
   struct Params {
diff --git a/src/messages/text_document_did_save.cc b/src/messages/text_document_did_save.cc
index 7eec5dd0..f187f018 100644
--- a/src/messages/text_document_did_save.cc
+++ b/src/messages/text_document_did_save.cc
@@ -9,7 +9,7 @@
 namespace {
 MethodType kMethodType = "textDocument/didSave";
 
-struct In_TextDocumentDidSave : public NotificationMessage {
+struct In_TextDocumentDidSave : public NotificationInMessage {
   MethodType GetMethodType() const override { return kMethodType; }
 
   struct Params {
diff --git a/src/messages/text_document_document_highlight.cc b/src/messages/text_document_document_highlight.cc
index b01bc7a6..42e74cdb 100644
--- a/src/messages/text_document_document_highlight.cc
+++ b/src/messages/text_document_document_highlight.cc
@@ -6,7 +6,7 @@
 namespace {
 MethodType kMethodType = "textDocument/documentHighlight";
 
-struct In_TextDocumentDocumentHighlight : public RequestMessage {
+struct In_TextDocumentDocumentHighlight : public RequestInMessage {
   MethodType GetMethodType() const override { return kMethodType; }
   lsTextDocumentPositionParams params;
 };
diff --git a/src/messages/text_document_document_link.cc b/src/messages/text_document_document_link.cc
index fc6994fa..9a05365a 100644
--- a/src/messages/text_document_document_link.cc
+++ b/src/messages/text_document_document_link.cc
@@ -8,7 +8,7 @@
 namespace {
 MethodType kMethodType = "textDocument/documentLink";
 
-struct In_TextDocumentDocumentLink : public RequestMessage {
+struct In_TextDocumentDocumentLink : public RequestInMessage {
   MethodType GetMethodType() const override { return kMethodType; }
   struct Params {
     // The document to provide document links for.
diff --git a/src/messages/text_document_document_symbol.cc b/src/messages/text_document_document_symbol.cc
index 4a48a2d3..2ec07533 100644
--- a/src/messages/text_document_document_symbol.cc
+++ b/src/messages/text_document_document_symbol.cc
@@ -10,7 +10,7 @@ struct lsDocumentSymbolParams {
 };
 MAKE_REFLECT_STRUCT(lsDocumentSymbolParams, textDocument);
 
-struct In_TextDocumentDocumentSymbol : public RequestMessage {
+struct In_TextDocumentDocumentSymbol : public RequestInMessage {
   MethodType GetMethodType() const override { return kMethodType; }
   lsDocumentSymbolParams params;
 };
diff --git a/src/messages/text_document_formatting.cc b/src/messages/text_document_formatting.cc
index 55c8f487..793c86d6 100644
--- a/src/messages/text_document_formatting.cc
+++ b/src/messages/text_document_formatting.cc
@@ -8,7 +8,7 @@
 namespace {
 MethodType kMethodType = "textDocument/formatting";
 
-struct In_TextDocumentFormatting : public RequestMessage {
+struct In_TextDocumentFormatting : public RequestInMessage {
   MethodType GetMethodType() const override { return kMethodType; }
   struct Params {
     lsTextDocumentIdentifier textDocument;
diff --git a/src/messages/text_document_hover.cc b/src/messages/text_document_hover.cc
index 2dbf26a1..6a852d8f 100644
--- a/src/messages/text_document_hover.cc
+++ b/src/messages/text_document_hover.cc
@@ -42,7 +42,7 @@ std::pair<std::string_view, std::string_view> GetCommentsAndHover(
   return {"", ""};
 }
 
-struct In_TextDocumentHover : public RequestMessage {
+struct In_TextDocumentHover : public RequestInMessage {
   MethodType GetMethodType() const override { return kMethodType; }
   lsTextDocumentPositionParams params;
 };
diff --git a/src/messages/text_document_range_formatting.cc b/src/messages/text_document_range_formatting.cc
index 29605e50..175dbb2a 100644
--- a/src/messages/text_document_range_formatting.cc
+++ b/src/messages/text_document_range_formatting.cc
@@ -19,7 +19,7 @@ MAKE_REFLECT_STRUCT(lsTextDocumentRangeFormattingParams,
                     range,
                     options);
 
-struct In_TextDocumentRangeFormatting : public RequestMessage {
+struct In_TextDocumentRangeFormatting : public RequestInMessage {
   MethodType GetMethodType() const override { return kMethodType; }
   lsTextDocumentRangeFormattingParams params;
 };
diff --git a/src/messages/text_document_references.cc b/src/messages/text_document_references.cc
index bd6896d7..19684cdb 100644
--- a/src/messages/text_document_references.cc
+++ b/src/messages/text_document_references.cc
@@ -7,7 +7,7 @@
 namespace {
 MethodType kMethodType = "textDocument/references";
 
-struct In_TextDocumentReferences : public RequestMessage {
+struct In_TextDocumentReferences : public RequestInMessage {
   MethodType GetMethodType() const override { return kMethodType; }
   struct lsReferenceContext {
     // Include the declaration of the current symbol.
diff --git a/src/messages/text_document_rename.cc b/src/messages/text_document_rename.cc
index b44048ad..b8dcc9d9 100644
--- a/src/messages/text_document_rename.cc
+++ b/src/messages/text_document_rename.cc
@@ -48,7 +48,7 @@ lsWorkspaceEdit BuildWorkspaceEdit(QueryDatabase* db,
   return edit;
 }
 
-struct In_TextDocumentRename : public RequestMessage {
+struct In_TextDocumentRename : public RequestInMessage {
   MethodType GetMethodType() const override { return kMethodType; }
   struct Params {
     // The document to format.
diff --git a/src/messages/text_document_signature_help.cc b/src/messages/text_document_signature_help.cc
index c4e74029..8f23e5be 100644
--- a/src/messages/text_document_signature_help.cc
+++ b/src/messages/text_document_signature_help.cc
@@ -9,7 +9,7 @@
 namespace {
 MethodType kMethodType = "textDocument/signatureHelp";
 
-struct In_TextDocumentSignatureHelp : public RequestMessage {
+struct In_TextDocumentSignatureHelp : public RequestInMessage {
   MethodType GetMethodType() const override { return kMethodType; }
   lsTextDocumentPositionParams params;
 };
@@ -86,7 +86,7 @@ MAKE_REFLECT_STRUCT(Out_TextDocumentSignatureHelp, jsonrpc, id, result);
 struct Handler_TextDocumentSignatureHelp : MessageHandler {
   MethodType GetMethodType() const override { return kMethodType; }
 
-  void Run(std::unique_ptr<BaseIpcMessage> message) override {
+  void Run(std::unique_ptr<InMessage> message) override {
     auto request = static_cast<In_TextDocumentSignatureHelp*>(message.get());
     lsTextDocumentPositionParams& params = request->params;
     WorkingFile* file =
@@ -103,7 +103,7 @@ struct Handler_TextDocumentSignatureHelp : MessageHandler {
       return;
 
     ClangCompleteManager::OnComplete callback = std::bind(
-        [this](BaseIpcMessage* message, std::string search, int active_param,
+        [this](InMessage* message, std::string search, int active_param,
                const std::vector<lsCompletionItem>& results,
                bool is_cached_result) {
           auto msg = static_cast<In_TextDocumentSignatureHelp*>(message);
diff --git a/src/messages/text_document_type_definition.cc b/src/messages/text_document_type_definition.cc
index 9797af8a..4226c558 100644
--- a/src/messages/text_document_type_definition.cc
+++ b/src/messages/text_document_type_definition.cc
@@ -5,7 +5,7 @@
 namespace {
 MethodType kMethodType = "textDocument/typeDefinition";
 
-struct In_TextDocumentTypeDefinition : public RequestMessage {
+struct In_TextDocumentTypeDefinition : public RequestInMessage {
   MethodType GetMethodType() const override { return kMethodType; }
   lsTextDocumentPositionParams params;
 };
diff --git a/src/messages/workspace_did_change_configuration.cc b/src/messages/workspace_did_change_configuration.cc
index 8714217a..c2ad85cb 100644
--- a/src/messages/workspace_did_change_configuration.cc
+++ b/src/messages/workspace_did_change_configuration.cc
@@ -16,7 +16,7 @@ struct lsDidChangeConfigurationParams {
 };
 MAKE_REFLECT_STRUCT(lsDidChangeConfigurationParams, placeholder);
 
-struct In_WorkspaceDidChangeConfiguration : public NotificationMessage {
+struct In_WorkspaceDidChangeConfiguration : public NotificationInMessage {
   MethodType GetMethodType() const override { return kMethodType; }
   lsDidChangeConfigurationParams params;
 };
diff --git a/src/messages/workspace_did_change_watched_files.cc b/src/messages/workspace_did_change_watched_files.cc
index 88471b94..d44081e7 100644
--- a/src/messages/workspace_did_change_watched_files.cc
+++ b/src/messages/workspace_did_change_watched_files.cc
@@ -28,7 +28,7 @@ struct lsDidChangeWatchedFilesParams {
 };
 MAKE_REFLECT_STRUCT(lsDidChangeWatchedFilesParams, changes);
 
-struct In_WorkspaceDidChangeWatchedFiles : public NotificationMessage {
+struct In_WorkspaceDidChangeWatchedFiles : public NotificationInMessage {
   MethodType GetMethodType() const override { return kMethodType; }
   lsDidChangeWatchedFilesParams params;
 };
diff --git a/src/messages/workspace_execute_command.cc b/src/messages/workspace_execute_command.cc
index f1600d89..e8f66f25 100644
--- a/src/messages/workspace_execute_command.cc
+++ b/src/messages/workspace_execute_command.cc
@@ -6,7 +6,7 @@
 namespace {
 MethodType kMethodType = "workspace/executeCommand";
 
-struct In_WorkspaceExecuteCommand : public RequestMessage {
+struct In_WorkspaceExecuteCommand : public RequestInMessage {
   MethodType GetMethodType() const override { return kMethodType; }
   lsCommand<lsCodeLensCommandArguments> params;
 };
diff --git a/src/messages/workspace_symbol.cc b/src/messages/workspace_symbol.cc
index 68d0abca..b069ec84 100644
--- a/src/messages/workspace_symbol.cc
+++ b/src/messages/workspace_symbol.cc
@@ -43,7 +43,7 @@ bool InsertSymbolIntoResult(QueryDatabase* db,
   return true;
 }
 
-struct In_WorkspaceSymbol : public RequestMessage {
+struct In_WorkspaceSymbol : public RequestInMessage {
   MethodType GetMethodType() const override { return kMethodType; }
   struct Params {
     std::string query;
diff --git a/src/ipc.cc b/src/method.cc
similarity index 68%
rename from src/ipc.cc
rename to src/method.cc
index 81139319..43e136fb 100644
--- a/src/ipc.cc
+++ b/src/method.cc
@@ -1,4 +1,4 @@
-#include "ipc.h"
+#include "method.h"
 
 const char* kMethodType_Unknown = "$unknown";
 const char* kMethodType_Exit = "exit";
@@ -6,8 +6,12 @@ const char* kMethodType_TextDocumentPublishDiagnostics = "textDocument/publishDi
 const char* kMethodType_CqueryPublishInactiveRegions = "$cquery/publishInactiveRegions";
 const char* kMethodType_CqueryPublishSemanticHighlighting = "$cquery/publishSemanticHighlighting";
 
-BaseIpcMessage::~BaseIpcMessage() = default;
+InMessage::~InMessage() = default;
 
-lsRequestId BaseIpcMessage::GetRequestId() {
-  return std::monostate();
+lsRequestId RequestInMessage::GetRequestId() const {
+  return id;
 }
+
+lsRequestId NotificationInMessage::GetRequestId() const {
+  return std::monostate();
+}
\ No newline at end of file
diff --git a/src/ipc.h b/src/method.h
similarity index 63%
rename from src/ipc.h
rename to src/method.h
index 0718d7fe..2a329866 100644
--- a/src/ipc.h
+++ b/src/method.h
@@ -5,28 +5,29 @@
 
 #include <string>
 
-using lsRequestId = std::variant<std::monostate, int64_t, std::string>;
-
 using MethodType = std::string;
-
 extern const char* kMethodType_Unknown;
 extern const char* kMethodType_Exit;
 extern const char* kMethodType_TextDocumentPublishDiagnostics;
 extern const char* kMethodType_CqueryPublishInactiveRegions;
 extern const char* kMethodType_CqueryPublishSemanticHighlighting;
 
-struct BaseIpcMessage {
-  virtual ~BaseIpcMessage();
+using lsRequestId = std::variant<std::monostate, int64_t, std::string>;
+
+struct InMessage {
+  virtual ~InMessage();
 
   virtual MethodType GetMethodType() const = 0;
-  virtual lsRequestId GetRequestId();
+  virtual lsRequestId GetRequestId() const = 0;
 };
 
-struct RequestMessage : public BaseIpcMessage {
+struct RequestInMessage : public InMessage {
   // number or string, actually no null
   lsRequestId id;
-  lsRequestId GetRequestId() override { return id; }
+  lsRequestId GetRequestId() const override;
 };
 
-// NotificationMessage does not have |id|.
-struct NotificationMessage : public BaseIpcMessage {};
+// NotificationInMessage does not have |id|.
+struct NotificationInMessage : public InMessage {
+  lsRequestId GetRequestId() const override;
+};
diff --git a/src/project.h b/src/project.h
index c3acdf22..2e2a9253 100644
--- a/src/project.h
+++ b/src/project.h
@@ -1,6 +1,7 @@
 #pragma once
 
 #include "config.h"
+#include "method.h"
 
 #include <optional.h>
 #include <sparsepp/spp.h>
@@ -11,8 +12,6 @@
 #include <string>
 #include <vector>
 
-// FIXME ipc.h
-using lsRequestId = std::variant<std::monostate, int64_t, std::string>;
 class QueueManager;
 struct WorkingFiles;
 
diff --git a/src/queue_manager.h b/src/queue_manager.h
index 34cc3b00..86478a36 100644
--- a/src/queue_manager.h
+++ b/src/queue_manager.h
@@ -1,6 +1,6 @@
 #pragma once
 
-#include "ipc.h"
+#include "method.h"
 #include "performance.h"
 #include "query.h"
 #include "threaded_queue.h"
@@ -94,7 +94,7 @@ class QueueManager {
   ThreadedQueue<Stdout_Request> for_stdout;
 
   // Runs on querydb thread.
-  ThreadedQueue<std::unique_ptr<BaseIpcMessage>> for_querydb;
+  ThreadedQueue<std::unique_ptr<InMessage>> for_querydb;
   ThreadedQueue<Index_DoIdMap> do_id_map;
 
   // Runs on indexer threads.