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 +30,14 @@
 #include "llvm/ADT/SmallVector.h"
 #include "llvm/ADT/StringRef.h"
 #include "llvm/Support/Error.h"
+#include <functional>
 #include <future>
 
 namespace clang {
 class NamedDecl;
 namespace clangd {
 struct PreambleData;
+struct CodeCompletion;
 
 struct CodeCompleteOptions {
   /// Returns options that can be passed to clang's completion engine.
@@ -129,6 +132,16 @@
     /// Always use text-based completion.
     NeverParse,
   } RunParser = ParseIfReady;
+
+  /// Callback invoked on all CompletionCandidate after they are scored and
+  /// before they are ranked (by -Score). Thus the results are yielded in
+  /// arbitrary order. CodeCompletion also contains the computed Score.
+  ///
+  /// This callbacks allows capturing various internal structures used by clangd
+  /// during code completion. Eg: Symbol quality and relevance signals.
+  std::function<void(const CodeCompletion &, const SymbolQualitySignals &,
+                     const SymbolRelevanceSignals &)>
+      RecordCCResult;
 };
 
 // Semi-structured representation of a code-complete suggestion for our C++ API.
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
@@ -1660,6 +1660,13 @@
                                ? Scores.Total / Relevance.NameMatch
                                : Scores.Quality;
 
+    if (Opts.RecordCCResult) {
+      CodeCompletion Completion = toCodeCompletion(Bundle);
+      Completion.Score = Scores;
+      Completion.CompletionTokenRange = ReplacedRange;
+      Opts.RecordCCResult(Completion, Quality, 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
@@ -29,7 +29,9 @@
 #include "gmock/gmock.h"
 #include "gtest/gtest.h"
 #include <condition_variable>
+#include <functional>
 #include <mutex>
+#include <vector>
 
 namespace clang {
 namespace clangd {
@@ -69,6 +71,7 @@
 MATCHER(InsertInclude, "") {
   return !arg.Includes.empty() && bool(arg.Includes[0].Insertion);
 }
+MATCHER(Scored, "") { return arg.Score.Total > 0; }
 MATCHER_P(SnippetSuffix, Text, "") { return arg.SnippetSuffix == Text; }
 MATCHER_P(Origin, OriginSet, "") { return arg.Origin == OriginSet; }
 MATCHER_P(Signature, S, "") { return arg.Signature == S; }
@@ -1041,6 +1044,21 @@
   EXPECT_THAT(Completions, Contains(Named("TT")));
 }
 
+TEST(CompletionTest, EnableInstrumentationMode) {
+  std::vector<CodeCompletion> RecordedCompletions;
+  CodeCompleteOptions Opts;
+  Opts.RecordCCResult = [&RecordedCompletions](const CodeCompletion &CC,
+                                               const SymbolQualitySignals &,
+                                               const SymbolRelevanceSignals &) {
+    RecordedCompletions.push_back(CC);
+  };
+
+  completions("int xy1, xy2; int a = xy^", /*IndexSymbols=*/{}, Opts);
+  EXPECT_THAT(RecordedCompletions,
+              UnorderedElementsAre(AllOf(Named("xy1"), Scored()),
+                                   AllOf(Named("xy2"), Scored())));
+}
+
 SignatureHelp signatures(llvm::StringRef Text, Position Point,
                          std::vector<Symbol> IndexSymbols = {}) {
   std::unique_ptr<SymbolIndex> Index;