Index: clangd/ClangdLSPServer.h
===================================================================
--- clangd/ClangdLSPServer.h
+++ clangd/ClangdLSPServer.h
@@ -155,6 +155,8 @@
   RealFileSystemProvider FSProvider;
   /// Options used for code completion
   clangd::CodeCompleteOptions CCOpts;
+  /// Options used for diagnostics.
+  ClangdDiagnosticOptions DiagOpts;
   /// The supported kinds of the client.
   SymbolKindBitset SupportedSymbolKinds;
 
Index: clangd/ClangdLSPServer.cpp
===================================================================
--- clangd/ClangdLSPServer.cpp
+++ clangd/ClangdLSPServer.cpp
@@ -82,6 +82,8 @@
 
   CCOpts.EnableSnippets =
       Params.capabilities.textDocument.completion.completionItem.snippetSupport;
+  DiagOpts.EmbedFixesInDiagnostics =
+      Params.capabilities.textDocument.publishDiagnostics.clangdFixSupport;
 
   if (Params.capabilities.workspace && Params.capabilities.workspace->symbol &&
       Params.capabilities.workspace->symbol->symbolKind) {
@@ -486,11 +488,25 @@
   DiagnosticToReplacementMap LocalFixIts; // Temporary storage
   for (auto &Diag : Diagnostics) {
     toLSPDiags(Diag, [&](clangd::Diagnostic Diag, llvm::ArrayRef<Fix> Fixes) {
-      DiagnosticsJSON.push_back(json::Object{
+      json::Object LSPDiag({
           {"range", Diag.range},
           {"severity", Diag.severity},
           {"message", Diag.message},
       });
+      // LSP extension: embed the fixes in the diagnostic.
+      if (DiagOpts.EmbedFixesInDiagnostics && !Fixes.empty()) {
+        json::Array ClangdFixes;
+        for (const auto &Fix : Fixes) {
+          WorkspaceEdit WE;
+          URIForFile URI{File};
+          WE.changes = {{URI.uri(), std::vector<TextEdit>(Fix.Edits.begin(),
+                                                          Fix.Edits.end())}};
+          ClangdFixes.push_back(
+              json::Object{{"edit", toJSON(WE)}, {"title", Fix.Message}});
+        }
+        LSPDiag["clangd.fixes"] = std::move(ClangdFixes);
+      }
+      DiagnosticsJSON.push_back(std::move(LSPDiag));
 
       auto &FixItsForDiagnostic = LocalFixIts[Diag];
       std::copy(Fixes.begin(), Fixes.end(),
Index: clangd/Diagnostics.h
===================================================================
--- clangd/Diagnostics.h
+++ clangd/Diagnostics.h
@@ -23,6 +23,12 @@
 namespace clang {
 namespace clangd {
 
+struct ClangdDiagnosticOptions {
+  /// If true, Clangd uses an LSP extension to embed the fixes with the
+  /// diagnostics that are sent to the client.
+  bool EmbedFixesInDiagnostics = false;
+};
+
 /// Contains basic information about a diagnostic.
 struct DiagBase {
   std::string Message;
Index: clangd/Protocol.h
===================================================================
--- clangd/Protocol.h
+++ clangd/Protocol.h
@@ -247,6 +247,18 @@
 };
 bool fromJSON(const llvm::json::Value &, CompletionClientCapabilities &);
 
+struct PublishDiagnosticsClientCapabilities {
+  // Whether the client accepts diagnostics with related information.
+  // NOTE: not used by clangd at the moment.
+  // bool relatedInformation;
+
+  /// Whether the client accepts diagnostics with fixes attached using the
+  /// "clangd.fixes" extension.
+  bool clangdFixSupport = false;
+};
+bool fromJSON(const llvm::json::Value &,
+              PublishDiagnosticsClientCapabilities &);
+
 /// A symbol kind.
 enum class SymbolKind {
   File = 1,
@@ -313,6 +325,9 @@
 struct TextDocumentClientCapabilities {
   /// Capabilities specific to the `textDocument/completion`
   CompletionClientCapabilities completion;
+
+  /// Capabilities specific to the 'textDocument/publishDiagnostics'
+  PublishDiagnosticsClientCapabilities publishDiagnostics;
 };
 bool fromJSON(const llvm::json::Value &, TextDocumentClientCapabilities &);
 
Index: clangd/Protocol.cpp
===================================================================
--- clangd/Protocol.cpp
+++ clangd/Protocol.cpp
@@ -178,6 +178,15 @@
   return true;
 }
 
+bool fromJSON(const llvm::json::Value &Params,
+              PublishDiagnosticsClientCapabilities &R) {
+  json::ObjectMapper O(Params);
+  if (!O)
+    return false;
+  O.map("clangdFixSupport", R.clangdFixSupport);
+  return true;
+}
+
 bool fromJSON(const json::Value &E, SymbolKind &Out) {
   if (auto T = E.getAsInteger()) {
     if (*T < static_cast<int>(SymbolKind::File) ||
@@ -240,6 +249,7 @@
   if (!O)
     return false;
   O.map("completion", R.completion);
+  O.map("publishDiagnostics", R.publishDiagnostics);
   return true;
 }
 
Index: test/clangd/fixits-embed-in-diagnostic.test
===================================================================
--- /dev/null
+++ test/clangd/fixits-embed-in-diagnostic.test
@@ -0,0 +1,66 @@
+# RUN: clangd -lit-test < %s | FileCheck -strict-whitespace %s
+{"jsonrpc":"2.0","id":0,"method":"initialize","params":{"processId":123,"rootPath":"clangd","capabilities":{"textDocument":{"publishDiagnostics":{"clangdFixSupport":true}}},"trace":"off"}}
+---
+{"jsonrpc":"2.0","method":"textDocument/didOpen","params":{"textDocument":{"uri":"test:///foo.c","languageId":"c","version":1,"text":"struct Point {}; union Point p;"}}}
+#      CHECK:    "method": "textDocument/publishDiagnostics",
+# CHECK-NEXT:    "params": {
+# CHECK-NEXT:     "diagnostics": [
+# CHECK-NEXT:      {
+# CHECK-NEXT:        "clangd.fixes": [
+# CHECK-NEXT:          {
+# CHECK-NEXT:            "edit": {
+# CHECK-NEXT:              "changes": {
+# CHECK-NEXT:                "file://{{.*}}/foo.c": [
+# CHECK-NEXT:                  {
+# CHECK-NEXT:                    "newText": "struct",
+# CHECK-NEXT:                    "range": {
+# CHECK-NEXT:                      "end": {
+# CHECK-NEXT:                        "character": 22,
+# CHECK-NEXT:                        "line": 0
+# CHECK-NEXT:                      },
+# CHECK-NEXT:                      "start": {
+# CHECK-NEXT:                        "character": 17,
+# CHECK-NEXT:                        "line": 0
+# CHECK-NEXT:                      }
+# CHECK-NEXT:                    }
+# CHECK-NEXT:                  }
+# CHECK-NEXT:                ]
+# CHECK-NEXT:              }
+# CHECK-NEXT:            },
+# CHECK-NEXT:            "title": "change 'union' to 'struct'"
+# CHECK-NEXT:          }
+# CHECK-NEXT:        ],
+# CHECK-NEXT:        "message": "Use of 'Point' with tag type that does not match previous declaration\n\nfoo.c:1:8: note: previous use is here",
+# CHECK-NEXT:        "range": {
+# CHECK-NEXT:          "end": {
+# CHECK-NEXT:            "character": 22,
+# CHECK-NEXT:            "line": 0
+# CHECK-NEXT:          },
+# CHECK-NEXT:          "start": {
+# CHECK-NEXT:            "character": 17,
+# CHECK-NEXT:            "line": 0
+# CHECK-NEXT:          }
+# CHECK-NEXT:        },
+# CHECK-NEXT:        "severity": 1
+# CHECK-NEXT:      },
+# CHECK-NEXT:      {
+# CHECK-NEXT:        "message": "Previous use is here\n\nfoo.c:1:18: error: use of 'Point' with tag type that does not match previous declaration",
+# CHECK-NEXT:        "range": {
+# CHECK-NEXT:          "end": {
+# CHECK-NEXT:            "character": 12,
+# CHECK-NEXT:            "line": 0
+# CHECK-NEXT:          },
+# CHECK-NEXT:          "start": {
+# CHECK-NEXT:            "character": 7,
+# CHECK-NEXT:            "line": 0
+# CHECK-NEXT:          }
+# CHECK-NEXT:        },
+# CHECK-NEXT:        "severity": 3
+# CHECK-NEXT:      }
+# CHECK-NEXT:    ],
+# CHECK-NEXT:    "uri": "file://{{.*}}/foo.c"
+# CHECK-NEXT:  }
+---
+{"jsonrpc":"2.0","id":4,"method":"shutdown"}
+---
+{"jsonrpc":"2.0","method":"exit"}