diff --git a/clang-tools-extra/clangd/ParsedAST.cpp b/clang-tools-extra/clangd/ParsedAST.cpp
--- a/clang-tools-extra/clangd/ParsedAST.cpp
+++ b/clang-tools-extra/clangd/ParsedAST.cpp
@@ -9,6 +9,7 @@
 #include "ParsedAST.h"
 #include "../clang-tidy/ClangTidyCheck.h"
 #include "../clang-tidy/ClangTidyDiagnosticConsumer.h"
+#include "../clang-tidy/ClangTidyModule.h"
 #include "../clang-tidy/ClangTidyModuleRegistry.h"
 #include "AST.h"
 #include "Compiler.h"
@@ -25,7 +26,6 @@
 #include "TidyProvider.h"
 #include "clang-include-cleaner/Record.h"
 #include "index/CanonicalIncludes.h"
-#include "index/Index.h"
 #include "index/Symbol.h"
 #include "support/Logger.h"
 #include "support/Trace.h"
@@ -50,7 +50,6 @@
 #include "llvm/ADT/STLExtras.h"
 #include "llvm/ADT/SmallVector.h"
 #include "llvm/ADT/StringRef.h"
-#include <algorithm>
 #include <memory>
 #include <optional>
 #include <vector>
@@ -476,9 +475,12 @@
   // diagnostics.
   if (PreserveDiags) {
     trace::Span Tracer("ClangTidyInit");
-    tidy::ClangTidyCheckFactories CTFactories;
-    for (const auto &E : tidy::ClangTidyModuleRegistry::entries())
-      E.instantiate()->addCheckFactories(CTFactories);
+    static const tidy::ClangTidyCheckFactories CTFactories = [] {
+      tidy::ClangTidyCheckFactories CTFactories;
+      for (const auto &E : tidy::ClangTidyModuleRegistry::entries())
+        E.instantiate()->addCheckFactories(CTFactories);
+      return CTFactories;
+    }();
     CTContext.emplace(std::make_unique<tidy::DefaultOptionsProvider>(
         tidy::ClangTidyGlobalOptions(), ClangTidyOpts));
     CTContext->setDiagnosticsEngine(&Clang->getDiagnostics());
@@ -610,10 +612,8 @@
     Macros = Patch->mainFileMacros();
     Marks = Patch->marks();
   }
-  auto& PP = Clang->getPreprocessor();
-  PP.addPPCallbacks(
-      std::make_unique<CollectMainFileMacros>(
-          PP, Macros));
+  auto &PP = Clang->getPreprocessor();
+  PP.addPPCallbacks(std::make_unique<CollectMainFileMacros>(PP, Macros));
 
   PP.addPPCallbacks(
       collectPragmaMarksCallback(Clang->getSourceManager(), Marks));
diff --git a/clang-tools-extra/clangd/TidyProvider.cpp b/clang-tools-extra/clangd/TidyProvider.cpp
--- a/clang-tools-extra/clangd/TidyProvider.cpp
+++ b/clang-tools-extra/clangd/TidyProvider.cpp
@@ -8,6 +8,7 @@
 
 #include "TidyProvider.h"
 #include "../clang-tidy/ClangTidyModuleRegistry.h"
+#include "../clang-tidy/ClangTidyOptions.h"
 #include "Config.h"
 #include "support/FileCache.h"
 #include "support/Logger.h"
@@ -283,11 +284,18 @@
 
 tidy::ClangTidyOptions getTidyOptionsForFile(TidyProviderRef Provider,
                                              llvm::StringRef Filename) {
-  tidy::ClangTidyOptions Opts = tidy::ClangTidyOptions::getDefaults();
-  Opts.Checks->clear();
-  if (Provider)
-    Provider(Opts, Filename);
-  return Opts;
+  // getDefaults instantiates all check factories, which are registered at link
+  // time. So cache the results once.
+  static const auto Opts = [] {
+    auto Opts = tidy::ClangTidyOptions::getDefaults();
+    Opts.Checks->clear();
+    return Opts;
+  }();
+  if (!Provider)
+    return Opts;
+  auto NewOpts = Opts;
+  Provider(NewOpts, Filename);
+  return NewOpts;
 }
 
 bool isRegisteredTidyCheck(llvm::StringRef Check) {