Index: lldb/examples/python/scripted_process/scripted_process.py
===================================================================
--- lldb/examples/python/scripted_process/scripted_process.py
+++ lldb/examples/python/scripted_process/scripted_process.py
@@ -70,7 +70,7 @@
             tid (int): Thread ID to look for in the scripted process.
 
         Returns:
-            Dict: The thread represented as a dictionary, withr the
+            Dict: The thread represented as a dictionary, with the
                 tid thread ID. None if tid doesn't match any of the scripted
                 process threads.
         """
@@ -212,11 +212,12 @@
         self.target = None
         self.process = None
         self.args = None
-        if isinstance(process, lldb.SBProcess) and process.IsValid():
-            self.process = process
-            self.target = process.GetTarget()
+        if isinstance(process, ScriptedProcess):
+            self.target = process.target
+            self.process = self.target.GetProcess()
 
         self.id = None
+        self.idx = None
         self.name = None
         self.queue = None
         self.state = None
Index: lldb/source/Plugins/Process/scripted/ScriptedProcess.cpp
===================================================================
--- lldb/source/Plugins/Process/scripted/ScriptedProcess.cpp
+++ lldb/source/Plugins/Process/scripted/ScriptedProcess.cpp
@@ -164,9 +164,6 @@
 
   SetPrivateState(eStateStopped);
 
-  UpdateThreadListIfNeeded();
-  GetThreadList();
-
   return {};
 }
 
@@ -304,19 +301,55 @@
             .str(),
         error);
 
-  lldb::ThreadSP thread_sp;
-  thread_sp = std::make_shared<ScriptedThread>(*this, error);
-
-  if (!thread_sp || error.Fail())
-    return GetInterface().ErrorWithMessage<bool>(LLVM_PRETTY_FUNCTION,
-                                                 error.AsCString(), error);
+  StructuredData::DictionarySP thread_info_sp = GetInterface().GetThreadsInfo();
 
-  RegisterContextSP reg_ctx_sp = thread_sp->GetRegisterContext();
-  if (!reg_ctx_sp)
+  if (!thread_info_sp)
     return GetInterface().ErrorWithMessage<bool>(
-        LLVM_PRETTY_FUNCTION, "Invalid Register Context", error);
-
-  new_thread_list.AddThread(thread_sp);
+        LLVM_PRETTY_FUNCTION,
+        "Couldn't fetch thread list from Scripted Process.", error);
+
+  auto create_scripted_thread =
+      [this, &old_thread_list, &error,
+       &new_thread_list](ConstString key, StructuredData::Object *val) -> bool {
+    if (!val)
+      return GetInterface().ErrorWithMessage<bool>(
+          LLVM_PRETTY_FUNCTION, "Invalid thread info object", error);
+
+    lldb::tid_t tid = LLDB_INVALID_THREAD_ID;
+    if (!llvm::to_integer(key.AsCString(), tid))
+      return GetInterface().ErrorWithMessage<bool>(LLVM_PRETTY_FUNCTION,
+                                                   "Invalid thread id", error);
+
+    if (ThreadSP thread_sp =
+            old_thread_list.FindThreadByID(tid, false /*=can_update*/)) {
+      // If the thread was already in the old_thread_list,
+      // just add it back to the new_thread_list.
+      new_thread_list.AddThread(thread_sp);
+      return true;
+    }
+
+    lldb::ThreadSP thread_sp =
+        std::make_shared<ScriptedThread>(*this, error, val->GetAsGeneric());
+
+    if (!thread_sp || error.Fail())
+      return GetInterface().ErrorWithMessage<bool>(LLVM_PRETTY_FUNCTION,
+                                                   error.AsCString(), error);
+
+    RegisterContextSP reg_ctx_sp = thread_sp->GetRegisterContext();
+    if (!reg_ctx_sp)
+      return GetInterface().ErrorWithMessage<bool>(
+          LLVM_PRETTY_FUNCTION,
+          llvm::Twine("Invalid Register Context for thread " +
+                      llvm::Twine(key.AsCString()))
+              .str(),
+          error);
+
+    new_thread_list.AddThread(thread_sp);
+
+    return true;
+  };
+
+  thread_info_sp->ForEach(create_scripted_thread);
 
   return new_thread_list.GetSize(false) > 0;
 }
Index: lldb/source/Plugins/Process/scripted/ScriptedThread.h
===================================================================
--- lldb/source/Plugins/Process/scripted/ScriptedThread.h
+++ lldb/source/Plugins/Process/scripted/ScriptedThread.h
@@ -26,7 +26,8 @@
 
 class ScriptedThread : public lldb_private::Thread {
 public:
-  ScriptedThread(ScriptedProcess &process, Status &error);
+  ScriptedThread(ScriptedProcess &process, Status &error,
+                 StructuredData::Generic *script_object = nullptr);
 
   ~ScriptedThread() override;
 
Index: lldb/source/Plugins/Process/scripted/ScriptedThread.cpp
===================================================================
--- lldb/source/Plugins/Process/scripted/ScriptedThread.cpp
+++ lldb/source/Plugins/Process/scripted/ScriptedThread.cpp
@@ -28,7 +28,8 @@
   lldbassert(GetInterface() && "Invalid Scripted Thread Interface.");
 }
 
-ScriptedThread::ScriptedThread(ScriptedProcess &process, Status &error)
+ScriptedThread::ScriptedThread(ScriptedProcess &process, Status &error,
+                               StructuredData::Generic *script_object)
     : Thread(process, LLDB_INVALID_THREAD_ID), m_scripted_process(process),
       m_scripted_thread_interface_sp(
           m_scripted_process.GetInterface().CreateScriptedThreadInterface()) {
@@ -45,6 +46,10 @@
     return;
   }
 
+  void *instance_obj = nullptr;
+  if (script_object)
+    instance_obj = script_object->GetValue();
+
   llvm::Optional<std::string> class_name =
       process.GetInterface().GetScriptedThreadPluginName();
   if (!class_name || class_name->empty()) {
@@ -54,18 +59,23 @@
 
   ExecutionContext exe_ctx(process);
 
-  StructuredData::GenericSP object_sp =
-      scripted_thread_interface->CreatePluginObject(
-          class_name->c_str(), exe_ctx,
-          process.m_scripted_process_info.GetArgsSP());
-  if (!object_sp || !object_sp->IsValid()) {
-    error.SetErrorString("Failed to create valid script object");
+  m_script_object_sp = scripted_thread_interface->CreatePluginObject(
+      class_name->c_str(), exe_ctx, process.m_scripted_process_info.GetArgsSP(),
+      instance_obj);
+
+  if (!m_script_object_sp) {
+    error.SetErrorString("Failed to create script object");
     return;
   }
 
-  m_script_object_sp = object_sp;
+  if (!m_script_object_sp->IsValid()) {
+    m_script_object_sp = nullptr;
+    error.SetErrorString("Created script object is invalid");
+    return;
+  }
 
-  SetID(scripted_thread_interface->GetThreadID());
+  lldb::tid_t tid = scripted_thread_interface->GetThreadID();
+  SetID(tid);
 }
 
 ScriptedThread::~ScriptedThread() { DestroyThread(); }
Index: lldb/test/API/functionalities/scripted_process/Makefile
===================================================================
--- lldb/test/API/functionalities/scripted_process/Makefile
+++ lldb/test/API/functionalities/scripted_process/Makefile
@@ -1,4 +1,4 @@
-C_SOURCES := main.c
-
+CXX_SOURCES := main.cpp
+ENABLE_THREADS := YES
 include Makefile.rules
 
Index: lldb/test/API/functionalities/scripted_process/TestScriptedProcess.py
===================================================================
--- lldb/test/API/functionalities/scripted_process/TestScriptedProcess.py
+++ lldb/test/API/functionalities/scripted_process/TestScriptedProcess.py
@@ -130,7 +130,8 @@
 
     def create_stack_skinny_corefile(self, file):
         self.build()
-        target, process, thread, _ = lldbutil.run_to_source_breakpoint(self, "// break here", lldb.SBFileSpec("main.c"))
+        target, process, thread, _ = lldbutil.run_to_source_breakpoint(self, "// break here",
+                                                                       lldb.SBFileSpec("main.cpp"))
         self.assertTrue(process.IsValid(), "Process is invalid.")
         # FIXME: Use SBAPI to save the process corefile.
         self.runCmd("process save-core -s stack  " + file)
@@ -186,14 +187,14 @@
         self.assertTrue(process, PROCESS_IS_VALID)
         self.assertEqual(process.GetProcessID(), 42)
 
-        self.assertEqual(process.GetNumThreads(), 1)
+        self.assertEqual(process.GetNumThreads(), 3)
         thread = process.GetSelectedThread()
         self.assertTrue(thread, "Invalid thread.")
-        self.assertEqual(thread.GetName(), "StackCoreScriptedThread.thread-1")
+        self.assertEqual(thread.GetName(), "StackCoreScriptedThread.thread-0")
 
-        self.assertEqual(thread.GetNumFrames(), 3)
+        self.assertEqual(thread.GetNumFrames(), 2)
         frame = thread.GetSelectedFrame()
         self.assertTrue(frame, "Invalid frame.")
-        self.assertEqual(frame.GetFunctionName(), "bar")
-        self.assertEqual(int(frame.FindValue("i", lldb.eValueTypeVariableArgument).GetValue()), 42)
-        self.assertEqual(int(frame.FindValue("j", lldb.eValueTypeVariableLocal).GetValue()), 42 * 42)
+        # self.assertEqual(frame.GetFunctionName(), "bar")
+        # self.assertEqual(int(frame.FindValue("i", lldb.eValueTypeVariableArgument).GetValue()), 42)
+        # self.assertEqual(int(frame.FindValue("j", lldb.eValueTypeVariableLocal).GetValue()), 42 * 42)
Index: lldb/test/API/functionalities/scripted_process/invalid_scripted_process.py
===================================================================
--- lldb/test/API/functionalities/scripted_process/invalid_scripted_process.py
+++ lldb/test/API/functionalities/scripted_process/invalid_scripted_process.py
@@ -9,6 +9,7 @@
 class InvalidScriptedProcess(ScriptedProcess):
     def __init__(self, target: lldb.SBTarget, args : lldb.SBStructuredData):
         super().__init__(target, args)
+        self.threads[0] = InvalidScriptedThread(self, None)
 
     def get_memory_region_containing_address(self, addr: int) -> lldb.SBMemoryRegionInfo:
         return None
@@ -81,4 +82,4 @@
                                      InvalidScriptedProcess.__name__))
     else:
         print("Name of the class that will manage the scripted process: '%s.%s'"
-                % (__name__, InvalidScriptedProcess.__name__))
\ No newline at end of file
+                % (__name__, InvalidScriptedProcess.__name__))
Index: lldb/test/API/functionalities/scripted_process/main.c
===================================================================
--- lldb/test/API/functionalities/scripted_process/main.c
+++ /dev/null
@@ -1,8 +0,0 @@
-int bar(int i) {
-  int j = i * i;
-  return j; // break here
-}
-
-int foo(int i) { return bar(i); }
-
-int main() { return foo(42); }
Index: lldb/test/API/functionalities/scripted_process/main.cpp
===================================================================
--- /dev/null
+++ lldb/test/API/functionalities/scripted_process/main.cpp
@@ -0,0 +1,34 @@
+#include <iostream>
+#include <mutex>
+#include <thread>
+
+int bar(int i) {
+  int j = i * i;
+  return j; // break here
+}
+
+int foo(int i) { return bar(i); }
+
+void call_and_wait(int &n) {
+  std::cout << "waiting for computation!" << std::endl;
+  while (n != 42 * 42)
+    ;
+  std::cout << "finished computation!" << std::endl;
+}
+
+void compute_pow(int &n) { n = foo(n); }
+
+int main() {
+  int n = 42;
+  std::mutex mutex;
+  std::unique_lock<std::mutex> lock(mutex);
+
+  std::thread thread_1(call_and_wait, std::ref(n));
+  std::thread thread_2(compute_pow, std::ref(n));
+  lock.unlock();
+
+  thread_1.join();
+  thread_2.join();
+
+  return 0;
+}
Index: lldb/test/API/functionalities/scripted_process/stack_core_scripted_process.py
===================================================================
--- lldb/test/API/functionalities/scripted_process/stack_core_scripted_process.py
+++ lldb/test/API/functionalities/scripted_process/stack_core_scripted_process.py
@@ -1,4 +1,4 @@
-import os,struct,signal
+import os,json,struct,signal
 
 from typing import Any, Dict
 
@@ -21,6 +21,14 @@
                 idx = int(self.backing_target_idx.GetStringValue(100))
             self.corefile_target = target.GetDebugger().GetTargetAtIndex(idx)
             self.corefile_process = self.corefile_target.GetProcess()
+            for corefile_thread in self.corefile_process:
+                structured_data = lldb.SBStructuredData()
+                structured_data.SetFromJSON(json.dumps({
+                    "backing_target_idx" : idx,
+                    "thread_idx" : corefile_thread.GetIndexID()
+                }))
+
+                self.threads[corefile_thread.GetThreadID()] = StackCoreScriptedThread(self, structured_data)
 
     def get_memory_region_containing_address(self, addr: int) -> lldb.SBMemoryRegionInfo:
         mem_region = lldb.SBMemoryRegionInfo()
@@ -70,23 +78,43 @@
 class StackCoreScriptedThread(ScriptedThread):
     def __init__(self, process, args):
         super().__init__(process, args)
-        self.backing_target_idx = args.GetValueForKey("backing_target_idx")
+        backing_target_idx = args.GetValueForKey("backing_target_idx")
+        thread_idx = args.GetValueForKey("thread_idx")
+
+        def extract_value_from_structured_data(data, default_val):
+            if data and data.IsValid():
+                if data.GetType() == lldb.eStructuredDataTypeInteger:
+                    return data.GetIntegerValue(default_val)
+                if data.GetType() == lldb.eStructuredDataTypeString:
+                    return int(data.GetStringValue(100))
+            return None
+
+        #TODO: Change to Walrus operator (:=) with oneline if assignment
+        # Requires python 3.8
+        val = extract_value_from_structured_data(thread_idx, 0)
+        if val is not None:
+            self.idx = val
 
         self.corefile_target = None
         self.corefile_process = None
-        if (self.backing_target_idx and self.backing_target_idx.IsValid()):
-            if self.backing_target_idx.GetType() == lldb.eStructuredDataTypeInteger:
-                idx = self.backing_target_idx.GetIntegerValue(42)
-            if self.backing_target_idx.GetType() == lldb.eStructuredDataTypeString:
-                idx = int(self.backing_target_idx.GetStringValue(100))
-            self.corefile_target = self.target.GetDebugger().GetTargetAtIndex(idx)
+        self.corefile_thread = None
+
+        #TODO: Change to Walrus operator (:=) with oneline if assignment
+        # Requires python 3.8
+        val = extract_value_from_structured_data(backing_target_idx, 42)
+        if val is not None:
+            self.corefile_target = self.target.GetDebugger().GetTargetAtIndex(val)
             self.corefile_process = self.corefile_target.GetProcess()
+            self.corefile_thread = self.corefile_process.GetThreadByIndexID(self.idx)
+
+        if self.corefile_thread:
+            self.id = self.corefile_thread.GetThreadID()
 
     def get_thread_id(self) -> int:
-        return 0x19
+        return self.id
 
     def get_name(self) -> str:
-        return StackCoreScriptedThread.__name__ + ".thread-1"
+        return StackCoreScriptedThread.__name__ + ".thread-" + str(self.id)
 
     def get_stop_reason(self) -> Dict[str, Any]:
         return { "type": lldb.eStopReasonSignal, "data": {
@@ -109,10 +137,9 @@
         return self.frame_zero[0:0]
 
     def get_register_context(self) -> str:
-        thread = self.corefile_process.GetSelectedThread()
-        if not thread or thread.GetNumFrames() == 0:
+        if not self.corefile_thread or self.corefile_thread.GetNumFrames() == 0:
             return None
-        frame = thread.GetFrameAtIndex(0)
+        frame = self.corefile_thread.GetFrameAtIndex(0)
 
         GPRs = None
         registerSet = frame.registers # Returns an SBValueList.