diff --git a/src/main.cc b/src/main.cc
index 7bd17552..74fd89c0 100644
--- a/src/main.cc
+++ b/src/main.cc
@@ -23,6 +23,7 @@ limitations under the License.
 
 #include <llvm/Support/CommandLine.h>
 #include <llvm/Support/CrashRecoveryContext.h>
+#include <llvm/Support/FileSystem.h>
 #include <llvm/Support/Process.h>
 #include <llvm/Support/Program.h>
 #include <llvm/Support/Signals.h>
@@ -49,6 +50,9 @@ opt<int> opt_verbose("v", desc("verbosity"), init(0), cat(C));
 opt<std::string> opt_test_index("test-index", ValueOptional, init("!"),
                                 desc("run index tests"), cat(C));
 
+opt<std::string> opt_index("index",
+                           desc("standalone mode: index a project and exit"),
+                           value_desc("root"), cat(C));
 opt<std::string> opt_init("init", desc("extra initialization options in JSON"),
                           cat(C));
 opt<std::string> opt_log_file("log-file", desc("log"), value_desc("filename"),
@@ -130,14 +134,20 @@ int main(int argc, char **argv) {
 
     sys::ChangeStdinToBinary();
     sys::ChangeStdoutToBinary();
-    // The thread that reads from stdin and dispatchs commands to the main
-    // thread.
-    pipeline::LaunchStdin();
-    // The thread that writes responses from the main thread to stdout.
-    pipeline::LaunchStdout();
-    // Main thread which also spawns indexer threads upon the "initialize"
-    // request.
-    pipeline::MainLoop();
+    if (opt_index.size()) {
+      SmallString<256> Root(opt_index);
+      sys::fs::make_absolute(Root);
+      pipeline::Standalone(Root.str());
+    } else {
+      // The thread that reads from stdin and dispatchs commands to the main
+      // thread.
+      pipeline::LaunchStdin();
+      // The thread that writes responses from the main thread to stdout.
+      pipeline::LaunchStdout();
+      // Main thread which also spawns indexer threads upon the "initialize"
+      // request.
+      pipeline::MainLoop();
+    }
   }
 
   return 0;
diff --git a/src/messages/initialize.cc b/src/messages/initialize.cc
index 810ffb85..402a635b 100644
--- a/src/messages/initialize.cc
+++ b/src/messages/initialize.cc
@@ -322,25 +322,13 @@ struct lsClientCapabilities {
 MAKE_REFLECT_STRUCT(lsClientCapabilities, workspace, textDocument);
 
 struct lsInitializeParams {
-  // The process Id of the parent process that started
-  // the server. Is null if the process has not been started by another process.
-  // If the parent process is not alive then the server should exit (see exit
-  // notification) its process.
-  std::optional<int> processId;
-
-  // The rootPath of the workspace. Is null
-  // if no folder is open.
-  //
-  // @deprecated in favour of rootUri.
-  std::optional<std::string> rootPath;
-
   // The rootUri of the workspace. Is null if no
   // folder is open. If both `rootPath` and `rootUri` are set
   // `rootUri` wins.
   std::optional<lsDocumentUri> rootUri;
 
   // User provided initialization options.
-  std::optional<Config> initializationOptions;
+  Config initializationOptions;
 
   // The capabilities provided by the client (editor or tool)
   lsClientCapabilities capabilities;
@@ -372,33 +360,8 @@ void Reflect(Reader &reader, lsInitializeParams::lsTrace &value) {
     value = lsInitializeParams::lsTrace::Verbose;
 }
 
-#if 0 // unused
-void Reflect(Writer& writer, lsInitializeParams::lsTrace& value) {
-  switch (value) {
-    case lsInitializeParams::lsTrace::Off:
-      writer.String("off");
-      break;
-    case lsInitializeParams::lsTrace::Messages:
-      writer.String("messages");
-      break;
-    case lsInitializeParams::lsTrace::Verbose:
-      writer.String("verbose");
-      break;
-  }
-}
-#endif
-
-MAKE_REFLECT_STRUCT(lsInitializeParams, processId, rootPath, rootUri,
-                    initializationOptions, capabilities, trace,
-                    workspaceFolders);
-
-struct lsInitializeError {
-  // Indicates whether the client should retry to send the
-  // initilize request after showing the message provided
-  // in the ResponseError.
-  bool retry;
-};
-MAKE_REFLECT_STRUCT(lsInitializeError, retry);
+MAKE_REFLECT_STRUCT(lsInitializeParams, rootUri, initializationOptions,
+                    capabilities, trace, workspaceFolders);
 
 struct In_InitializeRequest : public RequestMessage {
   MethodType GetMethodType() const override { return kMethodType; }
@@ -438,10 +401,7 @@ struct Handler_Initialize : BaseMessageHandler<In_InitializeRequest> {
                 << params.rootUri->raw_uri;
 
     {
-      if (params.initializationOptions)
-        g_config = new Config(*params.initializationOptions);
-      else
-        g_config = new Config;
+      g_config = new Config(params.initializationOptions);
       rapidjson::Document reader;
       reader.Parse(g_init_options.c_str());
       if (!reader.HasParseError()) {
@@ -531,3 +491,17 @@ struct Handler_Initialize : BaseMessageHandler<In_InitializeRequest> {
 };
 REGISTER_MESSAGE_HANDLER(Handler_Initialize);
 } // namespace
+
+void StandaloneInitialize(const std::string &root, Project &project,
+                          WorkingFiles &wfiles, VFS &vfs,
+                          IncludeComplete &complete) {
+  Handler_Initialize handler;
+  handler.project = &project;
+  handler.working_files = &wfiles;
+  handler.vfs = &vfs;
+  handler.include_complete = &complete;
+
+  In_InitializeRequest request;
+  request.params.rootUri = lsDocumentUri::FromPath(root);
+  handler.Run(&request);
+}
diff --git a/src/pipeline.cc b/src/pipeline.cc
index 62fd4d21..ed674646 100644
--- a/src/pipeline.cc
+++ b/src/pipeline.cc
@@ -30,6 +30,7 @@ limitations under the License.
 
 #include <rapidjson/writer.h>
 
+#include <llvm/Support/Process.h>
 #include <llvm/Support/Threading.h>
 #include <llvm/Support/Timer.h>
 using namespace llvm;
@@ -42,6 +43,9 @@ using namespace llvm;
 #include <unistd.h>
 #endif
 
+void StandaloneInitialize(const std::string &, Project &, WorkingFiles &, VFS &,
+                          IncludeComplete &);
+
 void VFS::Clear() {
   std::lock_guard lock(mutex);
   state.clear();
@@ -535,6 +539,35 @@ void MainLoop() {
   }
 }
 
+void Standalone(const std::string &root) {
+  Project project;
+  WorkingFiles wfiles;
+  VFS vfs;
+  IncludeComplete complete(&project);
+  StandaloneInitialize(root, project, wfiles, vfs, complete);
+  bool tty = sys::Process::StandardOutIsDisplayed();
+
+  if (tty) {
+    int entries = 0;
+    for (auto &[_, folder] : project.root2folder)
+      entries += folder.entries.size();
+      printf("entries: %5d\n", entries);
+  }
+  while (1) {
+    (void)on_indexed->DequeueAll();
+    int pending = pending_index_requests;
+    if (tty) {
+      printf("\rpending: %5d", pending);
+      fflush(stdout);
+    }
+    if (!pending)
+      break;
+    std::this_thread::sleep_for(std::chrono::milliseconds(100));
+  }
+  if (tty)
+    puts("");
+}
+
 void Index(const std::string &path, const std::vector<const char *> &args,
            IndexMode mode, lsRequestId id) {
   pending_index_requests++;
diff --git a/src/pipeline.hh b/src/pipeline.hh
index e0adc969..112e8bb9 100644
--- a/src/pipeline.hh
+++ b/src/pipeline.hh
@@ -45,6 +45,7 @@ void LaunchStdout();
 void Indexer_Main(CompletionManager *completion, VFS *vfs, Project *project,
                   WorkingFiles *wfiles);
 void MainLoop();
+void Standalone(const std::string &root);
 
 void Index(const std::string &path, const std::vector<const char *> &args,
            IndexMode mode, lsRequestId id = {});