Index: clangd/ClangdLSPServer.cpp
===================================================================
--- clangd/ClangdLSPServer.cpp
+++ clangd/ClangdLSPServer.cpp
@@ -71,6 +71,8 @@
                     JSONOutput &Out) override;
   void onGoToDefinition(TextDocumentPositionParams Params, StringRef ID,
                             JSONOutput &Out) override;
+  void onSwitchSourceHeader(TextDocumentIdentifier Params, StringRef ID,
+                    JSONOutput &Out) override;                          
 
 private:
   ClangdLSPServer &LangServer;
@@ -216,6 +218,16 @@
       R"(,"result":[)" + Locations + R"(]})");
 }
 
+void ClangdLSPServer::LSPProtocolCallbacks::onSwitchSourceHeader(
+    TextDocumentIdentifier Params, StringRef ID, JSONOutput &Out) {
+
+  std::string result = LangServer.Server.switchSourceHeader(Params.uri.uri);
+
+    Out.writeMessage(
+        R"({"jsonrpc":"2.0","id":)" + ID.str() +
+        R"(,"result":)" + result + R"(})");
+}
+
 ClangdLSPServer::ClangdLSPServer(JSONOutput &Out, bool RunSynchronously)
     : Out(Out), DiagConsumer(*this),
       Server(CDB, DiagConsumer, FSProvider, RunSynchronously) {}
Index: clangd/ClangdServer.h
===================================================================
--- clangd/ClangdServer.h
+++ clangd/ClangdServer.h
@@ -182,6 +182,8 @@
   /// Get definition of symbol at a specified \p Line and \p Column in \p File.
   Tagged<std::vector<Location>> findDefinitions(PathRef File, Position Pos);
 
+  std::string switchSourceHeader(std::string path);
+
   /// Run formatting for \p Rng inside \p File.
   std::vector<tooling::Replacement> formatRange(PathRef File, Range Rng);
   /// Run formatting for the whole \p File.
Index: clangd/ClangdServer.cpp
===================================================================
--- clangd/ClangdServer.cpp
+++ clangd/ClangdServer.cpp
@@ -286,3 +286,18 @@
       });
   return make_tagged(std::move(Result), TaggedFS.Tag);
 }
+
+std::string ClangdServer::switchSourceHeader(std::string path) {
+
+  if (path.compare(path.length() - 4, 4, ".cpp") == 0) {
+    path = path.substr(0, (path.length() - 4));
+    path.append(".h");
+    return "\"" + path + "\"";
+  } else if (path.compare(path.length() - 2, 2, ".h") == 0) {
+    path = path.substr(0, (path.length() - 2));
+    path.append(".cpp");
+    return "\"" + path + "\"";
+  } else {
+    return "";
+  }
+}
Index: clangd/ProtocolHandlers.h
===================================================================
--- clangd/ProtocolHandlers.h
+++ clangd/ProtocolHandlers.h
@@ -48,6 +48,8 @@
                             JSONOutput &Out) = 0;
   virtual void onGoToDefinition(TextDocumentPositionParams Params, StringRef ID,
                             JSONOutput &Out) = 0;
+  virtual void onSwitchSourceHeader(TextDocumentIdentifier Params, StringRef ID,
+                            JSONOutput &Out) = 0;
 };
 
 void regiterCallbackHandlers(JSONRPCDispatcher &Dispatcher, JSONOutput &Out,
Index: clangd/ProtocolHandlers.cpp
===================================================================
--- clangd/ProtocolHandlers.cpp
+++ clangd/ProtocolHandlers.cpp
@@ -204,6 +204,23 @@
   ProtocolCallbacks &Callbacks;
 };
 
+struct SwitchSourceHeaderHandler : Handler {
+  SwitchSourceHeaderHandler(JSONOutput &Output, ProtocolCallbacks &Callbacks)
+      : Handler(Output), Callbacks(Callbacks) {}
+
+  void handleMethod(llvm::yaml::MappingNode *Params, StringRef ID) override {
+    auto TDPP = TextDocumentIdentifier::parse(Params);
+    if (!TDPP) {
+      return;
+    }
+
+    Callbacks.onSwitchSourceHeader(*TDPP, ID, Output);
+  }
+
+private:
+  ProtocolCallbacks &Callbacks;
+};
+
 } // namespace
 
 void clangd::regiterCallbackHandlers(JSONRPCDispatcher &Dispatcher,
@@ -239,4 +256,7 @@
       llvm::make_unique<CompletionHandler>(Out, Callbacks));
   Dispatcher.registerHandler("textDocument/definition",
       llvm::make_unique<GotoDefinitionHandler>(Out, Callbacks));
+  Dispatcher.registerHandler(
+      "textDocument/switchSourceHeader",
+      llvm::make_unique<SwitchSourceHeaderHandler>(Out, Callbacks));
 }
Index: test/clangd/hover.test
===================================================================
--- /dev/null
+++ test/clangd/hover.test
@@ -0,0 +1,26 @@
+# RUN: clangd -run-synchronously < %s | FileCheck %s
+# It is absolutely vital that this file has CRLF line endings.
+#
+Content-Length: 125
+
+{"jsonrpc":"2.0","id":0,"method":"initialize","params":{"processId":123,"rootPath":"clangd","capabilities":{},"trace":"off"}}
+
+Content-Length: 172
+
+{"jsonrpc":"2.0","method":"textDocument/didOpen","params":{"textDocument":{"uri":"file:///main.cpp","languageId":"cpp","version":1,"text":"int main() {\nint a;\na;\n}\n"}}}
+
+Content-Length: 143
+
+{"jsonrpc":"2.0","id":1,"method":"textDocument/hover","params":{"textDocument":{"uri":"file:///main.cpp"},"position":{"line":0,"character":5}}}
+# Go to local variable
+# CHECK: {"jsonrpc":"2.0","id":1,"result":{"contents": {"language": "C++", "value": "int main() {\nint a;\na;\n}"}, "range": {"start": {"line": 0, "character": 0}, "end": {"line": 3, "character": 1}}}}
+
+Content-Length: 143
+
+{"jsonrpc":"2.0","id":1,"method":"textDocument/hover","params":{"textDocument":{"uri":"file:///main.cpp"},"position":{"line":1,"character":5}}}
+# Go to local variable
+# CHECK: {"jsonrpc":"2.0","id":1,"result":{"contents": {"language": "C++", "value": "int a"}, "range": {"start": {"line": 1, "character": 0}, "end": {"line": 1, "character": 5}}}}
+
+Content-Length: 44
+
+{"jsonrpc":"2.0","id":3,"method":"shutdown"}