Index: clang/docs/StandardCPlusPlusModules.rst
===================================================================
--- clang/docs/StandardCPlusPlusModules.rst
+++ clang/docs/StandardCPlusPlusModules.rst
@@ -821,6 +821,63 @@
 there are some differences between header units and Clang modules and that ignoring those
 differences now would likely become a problem in the future.
 
+Interoperability with tool chains
+=================================
+
+The modules change the traditional header based C++ project structures drastically.
+So the interoperability of many tool chains is broken. Here we track the status quo
+and the interoperability with clang for different tools.
+
+clangd
+======
+
+The clangd is a language server that can work with many editors via a plugin.
+The clangd can show diagnostics of errors and warnings in-place, suggest fixes,
+show extra hints about code problems and suggest code completion.
+
+Since clangd will invoke clang to parse the files according to flags from the
+`compilation database <https://clang.llvm.org/docs/JSONCompilationDatabase.html>`_,
+so as long as the clang can compile the files by these flags in the compilation database,
+the clangd should be able to handle the files in some level.
+
+So given clang can compile some modules codes now,
+the clangd can work for modules in some degree. The following is an simple example to show
+how to use clangd for modules:
+
+.. code-block:: c++
+
+  // A.cppm
+  export module A;
+  export void printA() {}
+
+  // Use.cpp
+  import A;
+  void foo() {
+  }
+
+  // compile_commands.json
+  [
+    {
+      "directory": "DIR",
+      "command": "clang++  -fprebuilt-module-path=DIR -std=c++20 -o DIR/main.cpp.o -c DIR/Use.cpp",
+      "file": "DIR/Use.cpp"
+    }
+  ]
+
+Now the important part is that we need to compile module A to BMI first:
+
+.. code-block:: console
+  
+  clang++  -fprebuilt-module-path=DIR -std=c++20 -o DIR/main.cpp.o -c DIR/Use.cpp
+
+Then in ``Use.cpp``, when we type `pr`, we can find the suggestion to `printA`.
+And if we require to find the definition for `printA`, we can go to the definition corretly.
+
+However, since modules bring completely new relationship to the C++ projects and
+clangd doesn't do special corresponding changes. It is natural that the interactions
+are not friendly, there are a lot of defects and even crashes. We can track the newest status
+in https://github.com/clangd/clangd/issues/1293.
+
 Possible Questions
 ==================