diff --git a/clang-tools-extra/clangd/ClangdServer.h b/clang-tools-extra/clangd/ClangdServer.h
--- a/clang-tools-extra/clangd/ClangdServer.h
+++ b/clang-tools-extra/clangd/ClangdServer.h
@@ -100,7 +100,7 @@
     bool StorePreamblesInMemory = true;
     /// Reuse even stale preambles, and rebuild them in the background.
     /// This improves latency at the cost of accuracy.
-    bool AsyncPreambleBuilds = false;
+    bool AsyncPreambleBuilds = true;
 
     /// If true, ClangdServer builds a dynamic in-memory index for symbols in
     /// opened files and uses the index to augment code completion results.
diff --git a/clang-tools-extra/clangd/TUScheduler.h b/clang-tools-extra/clangd/TUScheduler.h
--- a/clang-tools-extra/clangd/TUScheduler.h
+++ b/clang-tools-extra/clangd/TUScheduler.h
@@ -194,7 +194,7 @@
 
     /// Whether to run PreamblePeer asynchronously.
     /// No-op if AsyncThreadsCount is 0.
-    bool AsyncPreambleBuilds = false;
+    bool AsyncPreambleBuilds = true;
 
     /// Used to create a context that wraps each single operation.
     /// Typically to inject per-file configuration.