diff --git a/clang-tools-extra/clangd/CodeComplete.h b/clang-tools-extra/clangd/CodeComplete.h
--- a/clang-tools-extra/clangd/CodeComplete.h
+++ b/clang-tools-extra/clangd/CodeComplete.h
@@ -19,6 +19,7 @@
 #include "Logger.h"
 #include "Path.h"
 #include "Protocol.h"
+#include "Quality.h"
 #include "index/Index.h"
 #include "index/Symbol.h"
 #include "index/SymbolOrigin.h"
@@ -29,12 +30,15 @@
 #include "llvm/ADT/SmallVector.h"
 #include "llvm/ADT/StringRef.h"
 #include "llvm/Support/Error.h"
+#include <functional>
 #include <future>
+#include <memory>
 
 namespace clang {
 class NamedDecl;
 namespace clangd {
 struct PreambleData;
+struct CodeCompleteResult;
 
 struct CodeCompleteOptions {
   /// Returns options that can be passed to clang's completion engine.
@@ -129,6 +133,13 @@
     /// Always use text-based completion.
     NeverParse,
   } RunParser = ParseIfReady;
+
+  /// Enables special instrumentation mode that allows capturing various
+  /// internal structures used by clangd during code completion. Eg: Symbol
+  /// quality and relevance signals of all the candidates in the output.
+  /// Ideally this must be disabled when being used by ClangdLSPServer.
+  bool EnableInstrumentationMode = false;
+  std::function<void(const CodeCompleteResult &)> *RecordCCResults;
 };
 
 // Semi-structured representation of a code-complete suggestion for our C++ API.
@@ -202,6 +213,10 @@
     // Relevance describes how well this candidate matched the query.
     // e.g. symbols from nearby files have higher relevance.
     float Relevance = 0.f;
+
+    // Signals captured when instrumentation is enabled during code completion.
+    std::shared_ptr<SymbolQualitySignals> QualitySignals;
+    std::shared_ptr<SymbolRelevanceSignals> RelevanceSignals;
   };
   Scores Score;
 
diff --git a/clang-tools-extra/clangd/CodeComplete.cpp b/clang-tools-extra/clangd/CodeComplete.cpp
--- a/clang-tools-extra/clangd/CodeComplete.cpp
+++ b/clang-tools-extra/clangd/CodeComplete.cpp
@@ -65,7 +65,9 @@
 #include "llvm/Support/FormatVariadic.h"
 #include "llvm/Support/ScopedPrinter.h"
 #include <algorithm>
+#include <iostream>
 #include <iterator>
+#include <memory>
 
 // We log detailed candidate here if you run with -debug-only=codecomplete.
 #define DEBUG_TYPE "CodeComplete"
@@ -1458,6 +1460,10 @@
     // Merge Sema and Index results, score them, and pick the winners.
     auto Top =
         mergeResults(Recorder->Results, IndexResults, /*Identifiers*/ {});
+
+    if (Opts.EnableInstrumentationMode)
+      (*Opts.RecordCCResults)(toCodeCompleteResult(Top));
+
     return toCodeCompleteResult(Top);
   }
 
@@ -1660,6 +1666,12 @@
                                ? Scores.Total / Relevance.NameMatch
                                : Scores.Quality;
 
+    if (Opts.EnableInstrumentationMode) {
+      Scores.QualitySignals = std::make_shared<SymbolQualitySignals>(Quality);
+      Scores.RelevanceSignals =
+          std::make_shared<SymbolRelevanceSignals>(Relevance);
+    }
+
     dlog("CodeComplete: {0} ({1}) = {2}\n{3}{4}\n", First.Name,
          llvm::to_string(Origin), Scores.Total, llvm::to_string(Quality),
          llvm::to_string(Relevance));
diff --git a/clang-tools-extra/clangd/unittests/CodeCompleteTests.cpp b/clang-tools-extra/clangd/unittests/CodeCompleteTests.cpp
--- a/clang-tools-extra/clangd/unittests/CodeCompleteTests.cpp
+++ b/clang-tools-extra/clangd/unittests/CodeCompleteTests.cpp
@@ -29,6 +29,7 @@
 #include "gmock/gmock.h"
 #include "gtest/gtest.h"
 #include <condition_variable>
+#include <functional>
 #include <mutex>
 
 namespace clang {
@@ -1041,6 +1042,31 @@
   EXPECT_THAT(Completions, Contains(Named("TT")));
 }
 
+TEST(CompletionTest, EnableInstrumentationMode) {
+  CodeCompleteResult CapturedResult;
+  std::function<void(const CodeCompleteResult &)> ResultRecorder =
+      [&CapturedResult](const CodeCompleteResult &Result) -> void {
+    CapturedResult = Result;
+  };
+  CodeCompleteOptions Opts;
+  Opts.EnableInstrumentationMode = true;
+  Opts.RecordCCResults = &ResultRecorder;
+
+  auto Results =
+      completions("int xyz; int a = xy^", /*IndexSymbols=*/{}, Opts);
+  EXPECT_EQ(Results.Completions.size(), CapturedResult.Completions.size());
+  ASSERT_GT(CapturedResult.Completions.size(), 0);
+  EXPECT_TRUE(CapturedResult.Completions.front().Score.QualitySignals);
+  EXPECT_TRUE(CapturedResult.Completions.front().Score.RelevanceSignals);
+}
+
+TEST(CompletionTest, DisableInstrumentationModeByDefault) {
+  auto Results = completions("int xyz; int a = xy^");
+  ASSERT_GT(Results.Completions.size(), 0);
+  EXPECT_FALSE(Results.Completions.front().Score.QualitySignals);
+  EXPECT_FALSE(Results.Completions.front().Score.RelevanceSignals);
+}
+
 SignatureHelp signatures(llvm::StringRef Text, Position Point,
                          std::vector<Symbol> IndexSymbols = {}) {
   std::unique_ptr<SymbolIndex> Index;