diff --git a/lldb/tools/lldb-dap/Handler/RequestHandler.h b/lldb/tools/lldb-dap/Handler/RequestHandler.h
index 50795f8252de3..7e56c258ad78a 100644
--- a/lldb/tools/lldb-dap/Handler/RequestHandler.h
+++ b/lldb/tools/lldb-dap/Handler/RequestHandler.h
@@ -120,11 +120,13 @@ class RequestHandler : public BaseRequestHandler {
     }
 
     Args arguments;
-    llvm::json::Path::Root root;
-    if (request.arguments && !fromJSON(request.arguments, arguments, root)) {
+    llvm::json::Path::Root root("arguments");
+    if (request.arguments && !fromJSON(*request.arguments, arguments, root)) {
       std::string parse_failure;
       llvm::raw_string_ostream OS(parse_failure);
-      root.printErrorContext(request.arguments, OS);
+      OS << "invalid arguments for request '" << request.command
+         << "': " << llvm::toString(root.getError()) << "\n";
+      root.printErrorContext(*request.arguments, OS);
 
       protocol::ErrorMessage error_message;
       error_message.format = parse_failure;
diff --git a/lldb/tools/lldb-dap/Protocol/ProtocolBase.cpp b/lldb/tools/lldb-dap/Protocol/ProtocolBase.cpp
index af63cc803e545..bfd68448fb483 100644
--- a/lldb/tools/lldb-dap/Protocol/ProtocolBase.cpp
+++ b/lldb/tools/lldb-dap/Protocol/ProtocolBase.cpp
@@ -178,7 +178,7 @@ bool fromJSON(json::Value const &Params, Response &R, json::Path P) {
     return false;
   }
 
-  return O.map("success", R.success) && O.mapOptional("message", R.message) &&
+  return O.map("success", R.success) && O.map("message", R.message) &&
          mapRaw(Params, "body", R.body, P);
 }
 
diff --git a/lldb/tools/lldb-dap/Protocol/ProtocolRequests.cpp b/lldb/tools/lldb-dap/Protocol/ProtocolRequests.cpp
index 7163399899f7e..3523f8ac87ec9 100644
--- a/lldb/tools/lldb-dap/Protocol/ProtocolRequests.cpp
+++ b/lldb/tools/lldb-dap/Protocol/ProtocolRequests.cpp
@@ -20,16 +20,16 @@ namespace lldb_dap::protocol {
 bool fromJSON(const llvm::json::Value &Params, CancelArguments &CA,
               llvm::json::Path P) {
   llvm::json::ObjectMapper O(Params, P);
-  return O && O.mapOptional("requestId", CA.requestId) &&
-         O.mapOptional("progressId", CA.progressId);
+  return O && O.map("requestId", CA.requestId) &&
+         O.map("progressId", CA.progressId);
 }
 
 bool fromJSON(const json::Value &Params, DisconnectArguments &DA,
               json::Path P) {
   json::ObjectMapper O(Params, P);
-  return O && O.mapOptional("restart", DA.restart) &&
-         O.mapOptional("terminateDebuggee", DA.terminateDebuggee) &&
-         O.mapOptional("suspendDebuggee", DA.suspendDebuggee);
+  return O && O.map("restart", DA.restart) &&
+         O.map("terminateDebuggee", DA.terminateDebuggee) &&
+         O.map("suspendDebuggee", DA.suspendDebuggee);
 }
 
 bool fromJSON(const llvm::json::Value &Params, PathFormat &PF,
@@ -75,23 +75,33 @@ bool fromJSON(const llvm::json::Value &Params, InitializeRequestArguments &IRA,
 
   const json::Object *O = Params.getAsObject();
 
-  for (auto &kv : ClientFeatureByKey)
-    if (std::optional<bool> v = O->getBoolean(kv.first()); v && *v)
+  for (auto &kv : ClientFeatureByKey) {
+    const json::Value *value_ref = O->get(kv.first());
+    if (!value_ref)
+      continue;
+
+    const std::optional<bool> value = value_ref->getAsBoolean();
+    if (!value) {
+      P.field(kv.first()).report("expected bool");
+      return false;
+    }
+
+    if (*value)
       IRA.supportedFeatures.insert(kv.second);
+  }
 
-  return OM.mapOptional("adatperID", IRA.adatperID) &&
-         OM.mapOptional("clientID", IRA.clientID) &&
-         OM.mapOptional("clientName", IRA.clientName) &&
-         OM.mapOptional("locale", IRA.locale) &&
-         OM.mapOptional("linesStartAt1", IRA.linesStartAt1) &&
-         OM.mapOptional("columnsStartAt1", IRA.columnsStartAt1) &&
-         OM.mapOptional("pathFormat", IRA.pathFormat) &&
-         OM.mapOptional("$__lldb_sourceInitFile", IRA.lldbExtSourceInitFile);
+  return OM.map("adapterID", IRA.adapterID) &&
+         OM.map("clientID", IRA.clientID) &&
+         OM.map("clientName", IRA.clientName) && OM.map("locale", IRA.locale) &&
+         OM.map("linesStartAt1", IRA.linesStartAt1) &&
+         OM.map("columnsStartAt1", IRA.columnsStartAt1) &&
+         OM.map("pathFormat", IRA.pathFormat) &&
+         OM.map("$__lldb_sourceInitFile", IRA.lldbExtSourceInitFile);
 }
 
 bool fromJSON(const json::Value &Params, SourceArguments &SA, json::Path P) {
   json::ObjectMapper O(Params, P);
-  return O && O.mapOptional("source", SA.source) &&
+  return O && O.map("source", SA.source) &&
          O.map("sourceReference", SA.sourceReference);
 }
 
diff --git a/lldb/tools/lldb-dap/Protocol/ProtocolRequests.h b/lldb/tools/lldb-dap/Protocol/ProtocolRequests.h
index 22d400fd494a5..6623dfa0db05c 100644
--- a/lldb/tools/lldb-dap/Protocol/ProtocolRequests.h
+++ b/lldb/tools/lldb-dap/Protocol/ProtocolRequests.h
@@ -100,7 +100,7 @@ enum PathFormat : unsigned { ePatFormatPath, ePathFormatURI };
 /// Arguments for `initialize` request.
 struct InitializeRequestArguments {
   /// The ID of the debug adapter.
-  std::string adatperID;
+  std::string adapterID;
 
   /// The ID of the client using this adapter.
   std::optional<std::string> clientID;
@@ -113,7 +113,7 @@ struct InitializeRequestArguments {
 
   /// Determines in what format paths are specified. The default is `path`,
   /// which is the native format.
-  std::optional<PathFormat> pathFormat = ePatFormatPath;
+  PathFormat pathFormat = ePatFormatPath;
 
   /// If true all line numbers are 1-based (default).
   std::optional<bool> linesStartAt1;
diff --git a/lldb/tools/lldb-dap/Protocol/ProtocolTypes.cpp b/lldb/tools/lldb-dap/Protocol/ProtocolTypes.cpp
index f4f0bf8dcea84..4d1e90215bbb4 100644
--- a/lldb/tools/lldb-dap/Protocol/ProtocolTypes.cpp
+++ b/lldb/tools/lldb-dap/Protocol/ProtocolTypes.cpp
@@ -38,9 +38,9 @@ bool fromJSON(const json::Value &Params, PresentationHint &PH, json::Path P) {
 
 bool fromJSON(const json::Value &Params, Source &S, json::Path P) {
   json::ObjectMapper O(Params, P);
-  return O && O.mapOptional("name", S.name) && O.mapOptional("path", S.path) &&
-         O.mapOptional("presentationHint", S.presentationHint) &&
-         O.mapOptional("sourceReference", S.sourceReference);
+  return O && O.map("name", S.name) && O.map("path", S.path) &&
+         O.map("presentationHint", S.presentationHint) &&
+         O.map("sourceReference", S.sourceReference);
 }
 
 json::Value toJSON(const ExceptionBreakpointsFilter &EBF) {