diff --git a/luprex/core/cpp/world-accessor.cpp b/luprex/core/cpp/world-accessor.cpp
index f7a31194..79e2e8dd 100644
--- a/luprex/core/cpp/world-accessor.cpp
+++ b/luprex/core/cpp/world-accessor.cpp
@@ -153,6 +153,21 @@ LuaDefine(tangible_id, "c") {
     return LS.result();
 }
 
+LuaDefine(tangible_getactor, "c") {
+    LuaRet actor;
+    LuaStack LS(L, actor);
+    LS.rawget(actor, LuaRegistry, "actor");
+    return LS.result();
+}
+
+LuaDefine(tangible_getplace, "c") {
+    LuaRet place;
+    LuaStack LS(L, place);
+    LS.rawget(place, LuaRegistry, "place");
+    return LS.result();
+}
+
+
 LuaDefine(world_wait, "f") {
     if ((lua_gettop(L) != 1) || (lua_type(L, -1) != LUA_TNUMBER)) {
         luaL_error(L, "Argument to wait must be a number.");
diff --git a/luprex/core/cpp/world-core.cpp b/luprex/core/cpp/world-core.cpp
index 93fb7310..82c60eb0 100644
--- a/luprex/core/cpp/world-core.cpp
+++ b/luprex/core/cpp/world-core.cpp
@@ -302,7 +302,11 @@ void World::update_gui(int64_t actor_id, int64_t place_id, Gui *gui) {
     lua_pushvalue(L, actor.index());
     lua_pushvalue(L, place.index());
     Gui::store_global_pointer(L, gui);
+    LS.rawset(LuaRegistry, "actor", actor);
+    LS.rawset(LuaRegistry, "place", place);
     int status = traceback_pcall(L, 2, 0);
+    LS.rawset(LuaRegistry, "actor", LuaNil);
+    LS.rawset(LuaRegistry, "place", LuaNil);
     Gui::store_global_pointer(L, nullptr);
     if (status != 0) {
         gui->clear();
@@ -361,8 +365,8 @@ void World::invoke_plan(int64_t actor_id, int64_t place_id, const std::string &a
 
     // Set up for Lua manipulation.
     lua_State *L = state();
-    LuaVar actor, place, func, tangibles, mt, index, actions, thread, threads, message, invdata;
-    LuaStack LS(L, actor, place, func, tangibles, mt, index, actions, thread, threads, message, invdata);
+    LuaVar actor, place, func, tangibles, mt, index, actions, thread, threads, thinfo, message, invdata;
+    LuaStack LS(L, actor, place, func, tangibles, mt, index, actions, thread, threads, thinfo, message, invdata);
 
     // Get the actor and place.
     LS.rawget(tangibles, LuaRegistry, "tangibles");
@@ -404,22 +408,26 @@ void World::invoke_plan(int64_t actor_id, int64_t place_id, const std::string &a
     // Create a new thread, set up function and parameters.
     lua_State *CO = LS.newthread(thread);
     
-    // Push the function to be invoked and its arguments.
+    // Move function and args to new thread.
     lua_pushvalue(L, func.index());
     lua_pushvalue(L, actor.index());
     lua_pushvalue(L, place.index());
     lua_pushvalue(L, invdata.index());
-
-    // Move actor, place, function and args to new thread.
     lua_xmove(L, CO, 4);
 
+    // Create the thread info table.
+    LS.newtable(thinfo);
+    LS.rawset(thinfo, "thread", thread);
+    LS.rawset(thinfo, "actor", actor);
+    LS.rawset(thinfo, "isnew", true);
+    
     // Store the thread into place's thread table.
     LS.rawget(threads, mt, "threads");
     if (!LS.istable(threads)) {
         LS.result();
         return;
     }
-    LS.rawset(threads, tid, thread);
+    LS.rawset(threads, tid, thinfo);
     LS.result();
     
     // Push the thread's ID into the runnable thread queue,
@@ -432,8 +440,8 @@ void World::invoke_plan(int64_t actor_id, int64_t place_id, const std::string &a
 void World::run_scheduled_threads(int64_t clk) {
     assert(stack_is_clear());
     lua_State *L = state();
-    LuaVar tangibles, place, mt, threads, thread;
-    LuaStack LS(L, tangibles, place, mt, threads, thread);
+    LuaVar tangibles, actor, place, mt, threads, thinfo, isnew, thread;
+    LuaStack LS(L, tangibles, actor, place, mt, threads, thinfo, isnew, thread);
     LS.rawget(tangibles, LuaRegistry, "tangibles");
 
     while (thread_sched_.ready(clk)) {
@@ -450,15 +458,31 @@ void World::run_scheduled_threads(int64_t clk) {
         if (!LS.istable(threads)) {
             continue;
         }
-        LS.rawget(thread, threads, sched.thread_id());
+        LS.rawget(thinfo, threads, sched.thread_id());
+        if (!LS.istable(thinfo)) {
+            continue;
+        }
+        LS.rawget(actor, thinfo, "actor");
+        if (!LS.istable(actor)) {
+            continue;
+        }
+        LS.rawget(isnew, thinfo, "isnew");
+        if (!LS.isboolean(isnew)) {
+            continue;
+        }
+        LS.rawget(thread, thinfo, "thread");
         if (!LS.isthread(thread)) {
             continue;
         }
 
         // Resume the coroutine.
+        LS.rawset(thinfo, "isnew", false);
         lua_State *CO = LS.ckthread(thread);
-        int top = lua_gettop(CO);
-        int status = lua_resume(CO, nullptr, (top >= 4) ? 3 : 0);
+        LS.rawset(LuaRegistry, "actor", actor);
+        LS.rawset(LuaRegistry, "place", place);
+        int status = lua_resume(CO, nullptr, LS.ckboolean(isnew) ? 3 : 0);
+        LS.rawset(LuaRegistry, "actor", LuaNil);
+        LS.rawset(LuaRegistry, "place", LuaNil);
 
         // Three possible outcomes: finished, yielded, or errored.
         if (status == LUA_YIELD) {