diff --git a/clang-tools-extra/clangd/ClangdLSPServer.cpp b/clang-tools-extra/clangd/ClangdLSPServer.cpp
--- a/clang-tools-extra/clangd/ClangdLSPServer.cpp
+++ b/clang-tools-extra/clangd/ClangdLSPServer.cpp
@@ -467,11 +467,10 @@
   if (Server)
     return Reply(llvm::make_error<LSPError>("server already initialized",
                                             ErrorCode::InvalidRequest));
-  if (const auto &Dir = Params.initializationOptions.compilationDatabasePath)
-    Opts.CompileCommandsDir = Dir;
   if (Opts.UseDirBasedCDB) {
     DirectoryBasedGlobalCompilationDatabase::Options CDBOpts(TFS);
-    CDBOpts.CompileCommandsDir = Opts.CompileCommandsDir;
+    if (const auto &Dir = Params.initializationOptions.compilationDatabasePath)
+      CDBOpts.CompileCommandsDir = Dir;
     CDBOpts.ContextProvider = Opts.ContextProvider;
     BaseCDB =
         std::make_unique<DirectoryBasedGlobalCompilationDatabase>(CDBOpts);
diff --git a/clang-tools-extra/clangd/test/log.test b/clang-tools-extra/clangd/test/log.test
--- a/clang-tools-extra/clangd/test/log.test
+++ b/clang-tools-extra/clangd/test/log.test
@@ -1,9 +1,9 @@
-# RUN: env CLANGD_FLAGS=-index-file=no-such-index not clangd -lit-test </dev/null 2>&1 >/dev/null | FileCheck %s
+# RUN: env CLANGD_FLAGS=-compile-commands-dir=no-such-dir not clangd -lit-test </dev/null 2>&1 >/dev/null | FileCheck %s
 CHECK: I[{{.*}}]{{.*}} clangd version {{.*}}
 CHECK: Working directory: {{.*}}
 CHECK: argv[0]: clangd
 CHECK: argv[1]: -lit-test
-CHECK: CLANGD_FLAGS: -index-file=no-such-index
-CHECK: E[{{.*}}] Can't open no-such-index
+CHECK: CLANGD_FLAGS: -compile-commands-dir=no-such-dir
+CHECK: E[{{.*}}] Path specified by --compile-commands-dir does not exist.
 CHECK: Starting LSP over stdin/stdout
 
diff --git a/clang-tools-extra/clangd/tool/ClangdMain.cpp b/clang-tools-extra/clangd/tool/ClangdMain.cpp
--- a/clang-tools-extra/clangd/tool/ClangdMain.cpp
+++ b/clang-tools-extra/clangd/tool/ClangdMain.cpp
@@ -8,6 +8,8 @@
 
 #include "ClangdLSPServer.h"
 #include "CodeComplete.h"
+#include "Config.h"
+#include "ConfigProvider.h"
 #include "Features.inc"
 #include "PathMapping.h"
 #include "Protocol.h"
@@ -43,6 +45,7 @@
 #include <mutex>
 #include <string>
 #include <thread>
+#include <utility>
 #include <vector>
 
 #ifndef _WIN32
@@ -544,15 +547,55 @@
     log("Associating {0} with monolithic index at {1}.", External.MountPoint,
         External.Location);
     auto NewIndex = std::make_unique<SwapIndex>(std::make_unique<MemIndex>());
-    Tasks.runAsync("Load-index:" + External.Location,
-                   [File = External.Location, PlaceHolder = NewIndex.get()] {
-                     if (auto Idx = loadIndex(File, /*UseDex=*/true))
-                       PlaceHolder->reset(std::move(Idx));
-                   });
+    auto IndexLoadTask = [File = External.Location,
+                          PlaceHolder = NewIndex.get()] {
+      if (auto Idx = loadIndex(File, /*UseDex=*/true))
+        PlaceHolder->reset(std::move(Idx));
+    };
+    if (Sync) {
+      IndexLoadTask();
+    } else {
+      Tasks.runAsync("Load-index:" + External.Location,
+                     std::move(IndexLoadTask));
+    }
     return std::move(NewIndex);
   }
   llvm_unreachable("Invalid ExternalIndexKind.");
 }
+
+class CommandLineFlagsConfigProvider : public config::Provider {
+  std::vector<config::CompiledFragment>
+  getFragments(const config::Params &,
+               config::DiagnosticCallback) const override {
+    config::CompiledFragment Frag = [](const config::Params &, Config &C) {
+      if (!CompileCommandsDir.empty()) {
+        C.CompileFlags.CDBSearch = {Config::CDBSearchSpec::FixedDir,
+                                    CompileCommandsDir.getValue()};
+      }
+      if (!IndexFile.empty()) {
+        Config::ExternalIndexSpec Spec;
+        Spec.Kind = Spec.File;
+        Spec.Location = IndexFile;
+        Spec.MountPoint = "";
+        C.Index.External = std::move(Spec);
+      }
+      if (!RemoteIndexAddress.empty()) {
+        assert(!ProjectRoot.empty() && IndexFile.empty());
+        Config::ExternalIndexSpec Spec;
+        Spec.Kind = Spec.Server;
+        Spec.Location = RemoteIndexAddress;
+        Spec.MountPoint = ProjectRoot;
+        C.Index.External = std::move(Spec);
+        C.Index.Background = Config::BackgroundPolicy::Skip;
+      }
+      if (!EnableBackgroundIndex) {
+        C.Index.Background = Config::BackgroundPolicy::Skip;
+      }
+      return true;
+    };
+    return {Frag};
+  }
+};
 } // namespace
 } // namespace clangd
 } // namespace clang
@@ -707,12 +750,17 @@
              "--compile-commands-dir to an absolute path: {0}. The argument "
              "will be ignored.",
              EC.message());
+        CompileCommandsDir.clear();
       } else {
-        Opts.CompileCommandsDir = std::string(Path.str());
+        CompileCommandsDir = Path.str().str();
+        // FIXME: Still set for clangd --check. Use config in --check workflow
+        // and get rid of these options?
+        Opts.CompileCommandsDir = CompileCommandsDir;
       }
     } else {
       elog("Path specified by --compile-commands-dir does not exist. The "
            "argument will be ignored.");
+      CompileCommandsDir.clear();
     }
   }
 
@@ -729,18 +777,6 @@
   Opts.BuildDynamicSymbolIndex = true;
   std::vector<std::unique_ptr<SymbolIndex>> IdxStack;
   std::unique_ptr<SymbolIndex> StaticIdx;
-  std::future<void> AsyncIndexLoad; // Block exit while loading the index.
-  if (!IndexFile.empty()) {
-    // Load the index asynchronously. Meanwhile SwapIndex returns no results.
-    SwapIndex *Placeholder;
-    StaticIdx.reset(Placeholder = new SwapIndex(std::make_unique<MemIndex>()));
-    AsyncIndexLoad = runAsync<void>([Placeholder] {
-      if (auto Idx = loadIndex(IndexFile, /*UseDex=*/true))
-        Placeholder->reset(std::move(Idx));
-    });
-    if (Sync)
-      AsyncIndexLoad.wait();
-  }
 #if CLANGD_ENABLE_REMOTE
   if (RemoteIndexAddress.empty() != ProjectRoot.empty()) {
     llvm::errs() << "remote-index-address and project-path have to be "
@@ -750,8 +786,6 @@
   if (!RemoteIndexAddress.empty()) {
     if (IndexFile.empty()) {
       log("Connecting to remote index at {0}", RemoteIndexAddress);
-      StaticIdx = remote::getClient(RemoteIndexAddress, ProjectRoot);
-      EnableBackgroundIndex = false;
     } else {
       elog("When enabling remote index, IndexFile should not be specified. "
            "Only one can be used at time. Remote index will ignored.");
@@ -802,12 +836,13 @@
     } else {
       elog("Couldn't determine user config file, not loading");
     }
-    std::vector<const config::Provider *> ProviderPointers;
-    for (const auto &P : ProviderStack)
-      ProviderPointers.push_back(P.get());
-    Config = config::Provider::combine(std::move(ProviderPointers));
-    Opts.ConfigProvider = Config.get();
   }
+  ProviderStack.push_back(std::make_unique<CommandLineFlagsConfigProvider>());
+  std::vector<const config::Provider *> ProviderPointers;
+  for (const auto &P : ProviderStack)
+    ProviderPointers.push_back(P.get());
+  Config = config::Provider::combine(std::move(ProviderPointers));
+  Opts.ConfigProvider = Config.get();
 
   // Create an empty clang-tidy option.
   TidyProvider ClangTidyOptProvider;