Index: clangd/ClangdServer.cpp
===================================================================
--- clangd/ClangdServer.cpp
+++ clangd/ClangdServer.cpp
@@ -159,6 +159,7 @@
 
     auto PreambleData = IP->Preamble;
 
+    WithContextValue WithFileName(kActiveFile, File);
     // FIXME(ibiryukov): even if Preamble is non-null, we may want to check
     // both the old and the new version in case only one of them matches.
     CodeCompleteResult Result = clangd::codeComplete(
@@ -297,10 +298,13 @@
 
 void ClangdServer::findDefinitions(PathRef File, Position Pos,
                                    Callback<std::vector<Location>> CB) {
-  auto Action = [Pos, this](Callback<std::vector<Location>> CB,
-                            llvm::Expected<InputsAndAST> InpAST) {
+  std::string ActiveFile = File;
+  auto Action = [Pos, ActiveFile, this](Callback<std::vector<Location>> CB,
+                                        llvm::Expected<InputsAndAST> InpAST) {
     if (!InpAST)
       return CB(InpAST.takeError());
+
+    WithContextValue WithFileName(kActiveFile, ActiveFile);
     CB(clangd::findDefinitions(InpAST->AST, Pos, Index));
   };
 
Index: clangd/Context.h
===================================================================
--- clangd/Context.h
+++ clangd/Context.h
@@ -217,6 +217,11 @@
   WithContext Restore;
 };
 
+// The active file in a clangd request (e.g. file in which code completion or
+// go-to-definition is triggered). This is not always set and has to be set in
+// individual requests.
+extern const clang::clangd::Key<llvm::StringRef> kActiveFile;
+
 } // namespace clangd
 } // namespace clang
 
Index: clangd/Context.cpp
===================================================================
--- clangd/Context.cpp
+++ clangd/Context.cpp
@@ -32,5 +32,7 @@
   return Replacement;
 }
 
+const clang::clangd::Key<llvm::StringRef> kActiveFile;
+
 } // namespace clangd
 } // namespace clang