diff --git a/4ed.cpp b/4ed.cpp
index d52c7a56..096c7f01 100644
--- a/4ed.cpp
+++ b/4ed.cpp
@@ -10,14 +10,14 @@
 // TOP
 
 internal void
-output_file_append(Models *models, Editing_File *file, String_Const_u8 value){
+output_file_append(Thread_Context *tctx, Models *models, Editing_File *file, String_Const_u8 value){
     i64 end = buffer_size(&file->state.buffer);
     Edit_Behaviors behaviors = {};
-    edit_single(models, file, Ii64(end), value, behaviors);
+    edit_single(tctx, models, file, Ii64(end), value, behaviors);
 }
 
 internal void
-file_cursor_to_end(Models *models, Editing_File *file){
+file_cursor_to_end(Thread_Context *tctx, Models *models, Editing_File *file){
     Assert(file != 0);
     i64 pos = buffer_size(&file->state.buffer);
     Layout *layout = &models->layout;
@@ -28,7 +28,7 @@ file_cursor_to_end(Models *models, Editing_File *file){
         if (view->file != file){
             continue;
         }
-        view_set_cursor(models, view, pos);
+        view_set_cursor(tctx, models, view, pos);
         view->mark = pos;
     }
 }
@@ -281,12 +281,12 @@ init_command_line_settings(App_Settings *settings, Plat_Settings *plat_settings,
 ////////////////////////////////
 
 internal Models*
-models_init(Thread_Context *tctx){
-    Arena *arena = reserve_arena(tctx);
-    Models *models = push_array_zero(arena, Models, 1);
-    models->tctx = tctx;
-    models->arena = arena;
-    heap_init(&models->heap, tctx->allocator);
+models_init(void){
+    Arena arena = make_arena_system();
+    Models *models = push_array_zero(&arena, Models, 1);
+    models->arena_ = arena;
+    models->arena = &models->arena_;
+    heap_init(&models->heap, get_base_allocator_system());
     return(models);
 }
 
@@ -306,7 +306,7 @@ app_get_logger(void){
 }
 
 App_Read_Command_Line_Sig(app_read_command_line){
-    Models *models = models_init(tctx);
+    Models *models = models_init();
     App_Settings *settings = &models->settings;
     block_zero_struct(settings);
     if (argc > 1){
@@ -322,7 +322,6 @@ App_Init_Sig(app_init){
     models->keep_playing = true;
     
     models->config_api = api;
-    models->app_links.cmd_context = models;
     
     API_VTable_custom custom_vtable = {};
     custom_api_fill_vtable(&custom_vtable);
@@ -330,7 +329,11 @@ App_Init_Sig(app_init){
     system_api_fill_vtable(&system_vtable);
     Custom_Layer_Init_Type *custom_init = api.init_apis(&custom_vtable, &system_vtable);
     Assert(custom_init != 0);
-    custom_init(&models->app_links);
+    
+    Application_Links app = {};
+    app.tctx = tctx;
+    app.cmd_context = models;
+    custom_init(&app);
     
     // NOTE(allen): coroutines
     coroutine_system_init(&models->coroutines);
@@ -360,8 +363,8 @@ App_Init_Sig(app_init){
         }
     }
     
-    managed_ids_init(models->tctx->allocator, &models->managed_id_set);
-    lifetime_allocator_init(models->tctx->allocator, &models->lifetime_allocator);
+    managed_ids_init(tctx->allocator, &models->managed_id_set);
+    lifetime_allocator_init(tctx->allocator, &models->lifetime_allocator);
     dynamic_workspace_init(&models->lifetime_allocator, DynamicWorkspace_Global, 0, &models->dynamic_workspace);
     
     // NOTE(allen): file setup
@@ -371,7 +374,7 @@ App_Init_Sig(app_init){
     
     // NOTE(allen): 
     global_history_init(&models->global_history);
-    text_layout_init(models, &models->text_layouts);
+    text_layout_init(tctx, &models->text_layouts);
     
     // NOTE(allen): clipboard setup
     models->working_set.clipboard_max_size = ArrayCount(models->working_set.clipboards);
@@ -412,17 +415,17 @@ App_Init_Sig(app_init){
     Heap *heap = &models->heap;
     for (i32 i = 0; i < ArrayCount(init_files); ++i){
         Editing_File *file = working_set_allocate_file(&models->working_set, &models->lifetime_allocator);
-        buffer_bind_name(models, arena, &models->working_set, file, init_files[i].name);
+        buffer_bind_name(tctx, models, arena, &models->working_set, file, init_files[i].name);
         
         if (init_files[i].ptr != 0){
             *init_files[i].ptr = file;
         }
         
         File_Attributes attributes = {};
-        file_create_from_string(models, file, SCu8(), attributes);
+        file_create_from_string(tctx, models, file, SCu8(), attributes);
         if (init_files[i].read_only){
             file->settings.read_only = true;
-            history_free(models, &file->state.history);
+            history_free(tctx, &file->state.history);
         }
         
         file->settings.never_kill = true;
@@ -433,12 +436,12 @@ App_Init_Sig(app_init){
     {
         Panel *panel = layout_initialize(arena, &models->layout);
         View *new_view = live_set_alloc_view(&models->lifetime_allocator, &models->live_set, panel);
-        view_init(models, new_view, models->scratch_buffer, models->view_event_handler);
+        view_init(tctx, models, new_view, models->scratch_buffer, models->view_event_handler);
     }
     
     // NOTE(allen): miscellaneous init
     hot_directory_init(arena, &models->hot_directory, current_directory);
-    child_process_container_init(models->tctx->allocator, &models->child_processes);
+    child_process_container_init(tctx->allocator, &models->child_processes);
     models->period_wakeup_timer = system_wake_up_timer_create();
 }
 
@@ -446,7 +449,7 @@ App_Step_Sig(app_step){
     Models *models = (Models*)base_ptr;
     
     Mutex_Lock file_order_lock(models->working_set.mutex);
-    Scratch_Block scratch(models->tctx, Scratch_Share);
+    Scratch_Block scratch(tctx, Scratch_Share);
     
     models->next_animate_delay = max_u32;
     models->animate_next_frame = false;
@@ -462,7 +465,7 @@ App_Step_Sig(app_step){
         String_Const_u8 *dest = working_set_next_clipboard_string(&models->heap, &models->working_set, clipboard.size);
         dest->size = eol_convert_in((char*)dest->str, (char*)clipboard.str, (i32)clipboard.size);
         if (input->clipboard_changed){
-            co_send_core_event(models, CoreCode_NewClipboardContents, *dest);
+            co_send_core_event(tctx, models, CoreCode_NewClipboardContents, *dest);
         }
     }
     
@@ -499,7 +502,7 @@ App_Step_Sig(app_step){
             if (system_cli_update_step(cli, dest, max, &amount)){
                 if (file != 0 && amount > 0){
                     amount = eol_in_place_convert_in(dest, amount);
-                    output_file_append(models, file, SCu8(dest, amount));
+                    output_file_append(tctx, models, file, SCu8(dest, amount));
                     edited_file = true;
                 }
             }
@@ -507,7 +510,7 @@ App_Step_Sig(app_step){
             if (system_cli_end_update(cli)){
                 if (file != 0){
                     String_Const_u8 str = push_u8_stringf(scratch, "exited with code %d", cli->exit);
-                    output_file_append(models, file, str);
+                    output_file_append(tctx, models, file, str);
                     edited_file = true;
                 }
                 processes_to_free[processes_to_free_count++] = child_process;
@@ -515,7 +518,7 @@ App_Step_Sig(app_step){
             }
             
             if (child_process->cursor_at_end && file != 0){
-                file_cursor_to_end(models, file);
+                file_cursor_to_end(tctx, models, file);
             }
         }
         
@@ -639,7 +642,7 @@ App_Step_Sig(app_step){
         event.core.code = CoreCode_Startup;
         event.core.flag_strings = flags;
         event.core.file_names = file_names;
-        co_send_event(models, &event);
+        co_send_event(tctx, models, &event);
     }
     
     // NOTE(allen): consume event stream
@@ -689,7 +692,7 @@ App_Step_Sig(app_step){
                     case EventConsume_ClickChangeView:
                     {
                         // NOTE(allen): run deactivate command
-                        co_send_core_event(models, view, CoreCode_ClickDeactivateView);
+                        co_send_core_event(tctx, models, view, CoreCode_ClickDeactivateView);
                         
                         layout->active_panel = mouse_panel;
                         models->animate_next_frame = true;
@@ -697,14 +700,14 @@ App_Step_Sig(app_step){
                         view = active_panel->view;
                         
                         // NOTE(allen): run activate command
-                        co_send_core_event(models, view, CoreCode_ClickActivateView);
+                        co_send_core_event(tctx, models, view, CoreCode_ClickActivateView);
                         
                         event_was_handled = true;
                     }break;
                     
                     case EventConsume_CustomCommand:
                     {
-                        event_was_handled = co_send_event(models, view, event);
+                        event_was_handled = co_send_event(tctx, models, view, event);
                     }break;
                 }
             }break;
@@ -745,7 +748,10 @@ App_Step_Sig(app_step){
     if (models->layout.panel_state_dirty){
         models->layout.panel_state_dirty = false;
         if (models->buffer_viewer_update != 0){
-            models->buffer_viewer_update(&models->app_links);
+            Application_Links app = {};
+            app.tctx = tctx;
+            app.cmd_context = models;
+            models->buffer_viewer_update(&app);
         }
     }
     
@@ -769,7 +775,7 @@ App_Step_Sig(app_step){
              panel = layout_get_next_open_panel(layout, panel)){
             View *view = panel->view;
             File_Edit_Positions edit_pos = view_get_edit_pos(view);
-            edit_pos.scroll.position = view_normalize_buffer_point(models, view, edit_pos.scroll.target);
+            edit_pos.scroll.position = view_normalize_buffer_point(tctx, models, view, edit_pos.scroll.target);
             block_zero_struct(&edit_pos.scroll.target);
             view_set_edit_pos(view, edit_pos);
         }
@@ -787,7 +793,7 @@ App_Step_Sig(app_step){
                 Editing_File *file = CastFromMember(Editing_File, external_mod_node, node);
                 dll_remove(node);
                 block_zero_struct(node);
-                co_send_core_event(models, CoreCode_FileExternallyModified, file->id);
+                co_send_core_event(tctx, models, CoreCode_FileExternallyModified, file->id);
             }
         }
     }
@@ -797,7 +803,7 @@ App_Step_Sig(app_step){
         models->keep_playing = false;
     }
     if (!models->keep_playing){
-        if (co_send_core_event(models, CoreCode_TryExit)){
+        if (co_send_core_event(tctx, models, CoreCode_TryExit)){
             models->keep_playing = true;
         }
     }
@@ -836,7 +842,10 @@ App_Step_Sig(app_step){
             if (ctx != 0){
                 Render_Caller_Function *render_caller = ctx->ctx.render_caller;
                 if (render_caller != 0){
-                    render_caller(&models->app_links, frame, view_get_id(live_views, view));
+                    Application_Links app = {};
+                    app.tctx = tctx;
+                    app.cmd_context = models;
+                    render_caller(&app, frame, view_get_id(live_views, view));
                 }
             }
         }
@@ -846,7 +855,7 @@ App_Step_Sig(app_step){
     }
     
     // NOTE(allen): flush the log
-    log_flush(models);
+    log_flush(tctx, models);
     
     // NOTE(allen): set the app_result
     Application_Step_Result app_result = {};
diff --git a/4ed.h b/4ed.h
index ff546206..705a11e2 100644
--- a/4ed.h
+++ b/4ed.h
@@ -47,7 +47,8 @@ struct Custom_API{
 };
 
 #define App_Init_Sig(name) \
-void name(Render_Target *target,    \
+void name(Thread_Context *tctx,     \
+Render_Target *target,    \
 void *base_ptr,           \
 String_Const_u8 clipboard,\
 String_Const_u8 current_directory,\
@@ -77,7 +78,8 @@ struct Application_Step_Input{
 };
 
 #define App_Step_Sig(name) Application_Step_Result \
-name(Render_Target *target,                \
+name(Thread_Context *tctx,                 \
+Render_Target *target,                \
 void *base_ptr,                       \
 Application_Step_Input *input)
 
diff --git a/4ed_allocator_models.cpp b/4ed_allocator_models.cpp
deleted file mode 100644
index fe74d240..00000000
--- a/4ed_allocator_models.cpp
+++ /dev/null
@@ -1,37 +0,0 @@
-/*
- * Mr. 4th Dimention - Allen Webster
- *
- * 27.08.2019
- *
- * Models based arena constructors
- *
- */
-
-// TOP
-
-internal Arena*
-reserve_arena(Models *models, umem chunk_size, umem align){
-    Thread_Context *tctx = models->tctx;
-    return(reserve_arena(tctx, chunk_size, align));
-}
-
-internal Arena*
-reserve_arena(Models *models, umem chunk_size){
-    Thread_Context *tctx = models->tctx;
-    return(reserve_arena(tctx, chunk_size));
-}
-
-internal Arena*
-reserve_arena(Models *models){
-    Thread_Context *tctx = models->tctx;
-    return(reserve_arena(tctx));
-}
-
-internal void
-release_arena(Models *models, Arena *arena){
-    Thread_Context *tctx = models->tctx;
-    release_arena(tctx, arena);
-}
-
-// BOTTOM
-
diff --git a/4ed_api_implementation.cpp b/4ed_api_implementation.cpp
index f82a0a7e..c2ef5986 100644
--- a/4ed_api_implementation.cpp
+++ b/4ed_api_implementation.cpp
@@ -45,7 +45,9 @@ api_check_view(View *view, Access_Flag access){
 
 function b32
 is_running_coroutine(Application_Links *app){
-    return(app->current_coroutine != 0);
+    Thread_Context *tctx = app->tctx;
+    Thread_Context_Extra_Info *info = (Thread_Context_Extra_Info*)tctx->user_data;
+    return(info->coroutine != 0);
 }
 
 api(custom) function b32
@@ -73,25 +75,13 @@ global_get_screen_rectangle(Application_Links *app){
 
 api(custom) function Thread_Context*
 get_thread_context(Application_Links *app){
-    Thread_Context *tctx = 0;
-    if (app->current_coroutine == 0){
-        Models *models = (Models*)app->cmd_context;
-        tctx = models->tctx;
-    }
-    else if (app->current_thread != 0){
-        tctx = (Thread_Context*)app->current_thread;
-    }
-    else{
-        Coroutine *coroutine = (Coroutine*)app->current_coroutine;
-        tctx = coroutine->tctx;
-    }
-    return(tctx);
+    return(app->tctx);
 }
 
 api(custom) function b32
 create_child_process(Application_Links *app, String_Const_u8 path, String_Const_u8 command, Child_Process_ID *child_process_id_out){
     Models *models = (Models*)app->cmd_context;
-    return(child_process_call(models, path, command, child_process_id_out));
+    return(child_process_call(app->tctx, models, path, command, child_process_id_out));
 }
 
 api(custom) function b32
@@ -246,7 +236,7 @@ buffer_replace_range(Application_Links *app, Buffer_ID buffer_id, Range_i64 rang
         i64 size = buffer_size(&file->state.buffer);
         if (0 <= range.first && range.first <= range.one_past_last && range.one_past_last <= size){
             Edit_Behaviors behaviors = {};
-            edit_single(models, file, range, string, behaviors);
+            edit_single(app->tctx, models, file, range, string, behaviors);
             result = true;
         }
     }
@@ -261,7 +251,7 @@ buffer_batch_edit(Application_Links *app, Buffer_ID buffer_id, Batch_Edit *batch
     b32 result = false;
     if (api_check_buffer(file)){
         Edit_Behaviors behaviors = {};
-        result = edit_batch(models, file, batch, behaviors);
+        result = edit_batch(app->tctx, models, file, batch, behaviors);
     }
     return(result);
 }
@@ -373,7 +363,7 @@ buffer_line_y_difference(Application_Links *app, Buffer_ID buffer_id, f32 width,
     if (api_check_buffer(file)){
         Face *face = font_set_face_from_id(&models->font_set, face_id);
         if (face != 0){
-            result = file_line_y_difference(models, file, width, face, line_a, line_b);
+            result = file_line_y_difference(app->tctx, models, file, width, face, line_a, line_b);
         }
     }
     return(result);
@@ -387,7 +377,7 @@ buffer_line_shift_y(Application_Links *app, Buffer_ID buffer_id, f32 width, Face
     if (api_check_buffer(file)){
         Face *face = font_set_face_from_id(&models->font_set, face_id);
         if (face != 0){
-            result = file_line_shift_y(models, file, width, face, line, y_shift);
+            result = file_line_shift_y(app->tctx, models, file, width, face, line, y_shift);
         }
     }
     return(result);
@@ -401,7 +391,7 @@ buffer_pos_at_relative_xy(Application_Links *app, Buffer_ID buffer_id, f32 width
     if (api_check_buffer(file)){
         Face *face = font_set_face_from_id(&models->font_set, face_id);
         if (face != 0){
-            result = file_pos_at_relative_xy(models, file, width, face, base_line, relative_xy);
+            result = file_pos_at_relative_xy(app->tctx, models, file, width, face, base_line, relative_xy);
         }
     }
     return(result);
@@ -416,7 +406,7 @@ buffer_relative_xy_of_pos(Application_Links *app, Buffer_ID buffer_id, f32 width
     if (api_check_buffer(file)){
         Face *face = font_set_face_from_id(&models->font_set, face_id);
         if (face != 0){
-            result = file_relative_xy_of_pos(models, file, width, face, base_line, pos);
+            result = file_relative_xy_of_pos(app->tctx, models, file, width, face, base_line, pos);
         }
     }
     return(result);
@@ -431,7 +421,7 @@ buffer_relative_character_from_pos(Application_Links *app, Buffer_ID buffer_id,
     if (api_check_buffer(file)){
         Face *face = font_set_face_from_id(&models->font_set, face_id);
         if (face != 0){
-            result = file_relative_character_from_pos(models, file, width, face, base_line, pos);
+            result = file_relative_character_from_pos(app->tctx, models, file, width, face, base_line, pos);
         }
     }
     return(result);
@@ -446,7 +436,7 @@ buffer_pos_from_relative_character(Application_Links *app,  Buffer_ID buffer_id,
     if (api_check_buffer(file)){
         Face *face = font_set_face_from_id(&models->font_set, face_id);
         if (face != 0){
-            result = file_pos_from_relative_character(models, file, width, face, base_line, relative_character);
+            result = file_pos_from_relative_character(app->tctx, models, file, width, face, base_line, relative_character);
         }
     }
     return(result);
@@ -460,7 +450,7 @@ view_line_y_difference(Application_Links *app, View_ID view_id, i64 line_a, i64
     View *view = imp_get_view(models, view_id);
     f32 result = {};
     if (api_check_view(view)){
-        result = view_line_y_difference(models, view, line_a, line_b);
+        result = view_line_y_difference(app->tctx, models, view, line_a, line_b);
     }
     return(result);
 }
@@ -471,7 +461,7 @@ view_line_shift_y(Application_Links *app, View_ID view_id, i64 line, f32 y_shift
     View *view = imp_get_view(models, view_id);
     Line_Shift_Vertical result = {};
     if (api_check_view(view)){
-        result = view_line_shift_y(models, view, line, y_shift);
+        result = view_line_shift_y(app->tctx, models, view, line, y_shift);
     }
     return(result);
 }
@@ -482,7 +472,7 @@ view_pos_at_relative_xy(Application_Links *app, View_ID view_id, i64 base_line,
     View *view = imp_get_view(models, view_id);
     i64 result = -1;
     if (api_check_view(view)){
-        result = view_pos_at_relative_xy(models, view, base_line, relative_xy);
+        result = view_pos_at_relative_xy(app->tctx, models, view, base_line, relative_xy);
     }
     return(result);
 }
@@ -493,7 +483,7 @@ view_relative_xy_of_pos(Application_Links *app, View_ID view_id, i64 base_line,
     View *view = imp_get_view(models, view_id);
     Vec2_f32 result = {};
     if (api_check_view(view)){
-        result = view_relative_xy_of_pos(models, view, base_line, pos);
+        result = view_relative_xy_of_pos(app->tctx, models, view, base_line, pos);
     }
     return(result);
 }
@@ -504,7 +494,7 @@ view_relative_character_from_pos(Application_Links *app,  View_ID view_id, i64 b
     View *view = imp_get_view(models, view_id);
     i64 result = {};
     if (api_check_view(view)){
-        result = view_relative_character_from_pos(models, view, base_line, pos);
+        result = view_relative_character_from_pos(app->tctx, models, view, base_line, pos);
     }
     return(result);
 }
@@ -515,7 +505,7 @@ view_pos_from_relative_character(Application_Links *app,  View_ID view_id, i64 b
     View *view = imp_get_view(models, view_id);
     i64 result = {};
     if (api_check_view(view)){
-        result = view_pos_from_relative_character(models, view, base_line, character);
+        result = view_pos_from_relative_character(app->tctx, models, view, base_line, character);
     }
     return(result);
 }
@@ -693,12 +683,12 @@ buffer_set_setting(Application_Links *app, Buffer_ID buffer_id, Buffer_Setting_I
             {
                 if (value){
                     if (!history_is_activated(&file->state.history)){
-                        history_init(models, &file->state.history);
+                        history_init(app->tctx, models, &file->state.history);
                     }
                 }
                 else{
                     if (history_is_activated(&file->state.history)){
-                        history_free(models, &file->state.history);
+                        history_free(app->tctx, &file->state.history);
                     }
                 }
             }break;
@@ -732,7 +722,7 @@ buffer_send_end_signal(Application_Links *app, Buffer_ID buffer_id)
     Editing_File *file = imp_get_file(models, buffer_id);
     b32 result = false;
     if (api_check_buffer(file)){
-        file_end_file(models, file);
+        file_end_file(app->tctx, models, file);
         result = true;
     }
     return(result);
@@ -742,7 +732,7 @@ api(custom) function Buffer_ID
 create_buffer(Application_Links *app, String_Const_u8 file_name, Buffer_Create_Flag flags)
 {
     Models *models = (Models*)app->cmd_context;
-    Editing_File *new_file = create_file(models, file_name, flags);
+    Editing_File *new_file = create_file(app->tctx, models, file_name, flags);
     Buffer_ID result = 0;
     if (new_file != 0){
         result = new_file->id;
@@ -766,9 +756,10 @@ buffer_save(Application_Links *app, Buffer_ID buffer_id, String_Const_u8 file_na
         }
         
         if (!skip_save){
-            Scratch_Block scratch(models->tctx, Scratch_Share);
+            Thread_Context *tctx = app->tctx;
+            Scratch_Block scratch(app->tctx, Scratch_Share);
             String_Const_u8 name = push_string_copy(scratch, file_name);
-            save_file_to_name(models, file, name.str);
+            save_file_to_name(tctx, models, file, name.str);
             result = true;
         }
     }
@@ -787,15 +778,16 @@ buffer_kill(Application_Links *app, Buffer_ID buffer_id, Buffer_Kill_Flag flags)
         if (!file->settings.never_kill){
             b32 needs_to_save = file_needs_save(file);
             if (!needs_to_save || (flags & BufferKill_AlwaysKill) != 0){
+                Thread_Context *tctx = app->tctx;
                 if (models->end_buffer != 0){
-                    models->end_buffer(&models->app_links, file->id);
+                    models->end_buffer(app, file->id);
                 }
                 
                 buffer_unbind_name_low_level(working_set, file);
                 if (file->canon.name_size != 0){
                     buffer_unbind_file(working_set, file);
                 }
-                file_free(models, file);
+                file_free(tctx, models, file);
                 working_set_free_file(&models->heap, working_set, file);
                 
                 Layout *layout = &models->layout;
@@ -810,7 +802,7 @@ buffer_kill(Application_Links *app, Buffer_ID buffer_id, Buffer_Kill_Flag flags)
                         Assert(file_node != order);
                         view->file = 0;
                         Editing_File *new_file = CastFromMember(Editing_File, touch_node, file_node);
-                        view_set_file(models, view, new_file);
+                        view_set_file(tctx, models, view, new_file);
                         file_node = file_node->next;
                         if (file_node == order){
                             file_node = file_node->next;
@@ -836,7 +828,8 @@ api(custom) function Buffer_Reopen_Result
 buffer_reopen(Application_Links *app, Buffer_ID buffer_id, Buffer_Reopen_Flag flags)
 {
     Models *models = (Models*)app->cmd_context;
-    Scratch_Block scratch(models->tctx, Scratch_Share);
+    Thread_Context *tctx = app->tctx;
+    Scratch_Block scratch(tctx, Scratch_Share);
     Editing_File *file = imp_get_file(models, buffer_id);
     Buffer_Reopen_Result result = BufferReopenResult_Failed;
     if (api_check_buffer(file)){
@@ -875,18 +868,18 @@ buffer_reopen(Application_Links *app, Buffer_ID buffer_id, Buffer_Reopen_Flag fl
                         }
                         
                         Working_Set *working_set = &models->working_set;
-                        file_free(models, file);
+                        file_free(tctx, models, file);
                         working_set_file_default_settings(working_set, file);
-                        file_create_from_string(models, file, SCu8(file_memory, attributes.size), attributes);
+                        file_create_from_string(tctx, models, file, SCu8(file_memory, attributes.size), attributes);
                         
                         for (i32 i = 0; i < vptr_count; ++i){
-                            view_set_file(models, vptrs[i], file);
+                            view_set_file(tctx, models, vptrs[i], file);
                             
                             vptrs[i]->file = file;
                             i64 line = line_numbers[i];
                             i64 col = column_numbers[i];
                             Buffer_Cursor cursor = file_compute_cursor(file, seek_line_col(line, col));
-                            view_set_cursor(models, vptrs[i], cursor.pos);
+                            view_set_cursor(tctx, models, vptrs[i], cursor.pos);
                         }
                         result = BufferReopenResult_Reopened;
                     }
@@ -919,7 +912,7 @@ api(custom) function File_Attributes
 get_file_attributes(Application_Links *app, String_Const_u8 file_name)
 {
     Models *models = (Models*)app->cmd_context;
-    Scratch_Block scratch(models->tctx, Scratch_Share);
+    Scratch_Block scratch(app->tctx, Scratch_Share);
     return(system_quick_file_attributes(scratch, file_name));
 }
 
@@ -1172,7 +1165,7 @@ panel_split(Application_Links *app, Panel_ID panel_id, Dimension split_dim){
             Live_Views *live_set = &models->live_set;
             View *new_view = live_set_alloc_view(&models->lifetime_allocator,
                                                  live_set, new_panel);
-            view_init(models, new_view, models->scratch_buffer,
+            view_init(app->tctx, models, new_view, models->scratch_buffer,
                       models->view_event_handler);
             result = true;
         }
@@ -1321,7 +1314,7 @@ view_get_buffer_region(Application_Links *app, View_ID view_id){
     View *view = imp_get_view(models, view_id);
     Rect_f32 result = {};
     if (api_check_view(view)){
-        result = view_get_buffer_rect(models, view);
+        result = view_get_buffer_rect(app->tctx, models, view);
     }
     return(result);
 }
@@ -1466,7 +1459,7 @@ view_set_cursor(Application_Links *app, View_ID view_id, Buffer_Seek seek)
         Assert(file != 0);
         if (api_check_buffer(file)){
             Buffer_Cursor cursor = file_compute_cursor(file, seek);
-            view_set_cursor(models, view, cursor.pos);
+            view_set_cursor(app->tctx, models, view, cursor.pos);
             result = true;
         }
     }
@@ -1481,15 +1474,16 @@ view_set_buffer_scroll(Application_Links *app, View_ID view_id, Buffer_Scroll sc
     b32 result = false;
     View *view = imp_get_view(models, view_id);
     if (api_check_view(view)){
-        scroll.position = view_normalize_buffer_point(models, view, scroll.position);
-        scroll.target = view_normalize_buffer_point(models, view, scroll.target);
+        Thread_Context *tctx = app->tctx;
+        scroll.position = view_normalize_buffer_point(tctx, models, view, scroll.position);
+        scroll.target = view_normalize_buffer_point(tctx, models, view, scroll.target);
         scroll.target.pixel_shift.x = f32_round32(scroll.target.pixel_shift.x);
         scroll.target.pixel_shift.y = f32_round32(scroll.target.pixel_shift.y);
         scroll.target.pixel_shift.x = clamp_bot(0.f, scroll.target.pixel_shift.x);
-        Buffer_Layout_Item_List line = view_get_line_layout(models, view, scroll.target.line_number);
+        Buffer_Layout_Item_List line = view_get_line_layout(tctx, models, view, scroll.target.line_number);
         scroll.target.pixel_shift.y = clamp(0.f, scroll.target.pixel_shift.y, line.height);
         if (rule == SetBufferScroll_SnapCursorIntoView){
-            view_set_scroll(models, view, scroll);
+            view_set_scroll(tctx, models, view, scroll);
         }
         else{
             File_Edit_Positions edit_pos = view_get_edit_pos(view);
@@ -1536,7 +1530,7 @@ view_set_buffer(Application_Links *app, View_ID view_id, Buffer_ID buffer_id, Se
         Editing_File *file = working_set_get_file(&models->working_set, buffer_id);
         if (api_check_buffer(file)){
             if (file != view->file){
-                view_set_file(models, view, file);
+                view_set_file(app->tctx, models, view, file);
                 if (!(flags & SetBuffer_KeepOriginalGUI)){
                     //view_quit_ui(models, view);
                     // TODO(allen): back to base context
@@ -1707,7 +1701,7 @@ get_managed_scope_with_multiple_dependencies(Application_Links *app, Managed_Sco
     Models *models = (Models*)app->cmd_context;
     Lifetime_Allocator *lifetime_allocator = &models->lifetime_allocator;
     
-    Scratch_Block scratch(models->tctx, Scratch_Share);
+    Scratch_Block scratch(app->tctx, Scratch_Share);
     
     // TODO(allen): revisit this
     struct Node_Ptr{
@@ -2029,9 +2023,11 @@ api(custom) function User_Input
 get_next_input(Application_Links *app, Event_Property get_properties, Event_Property abort_properties)
 {
     Models *models = (Models*)app->cmd_context;
+    Thread_Context *tctx = app->tctx;
+    Thread_Context_Extra_Info *tctx_info = (Thread_Context_Extra_Info*)tctx->user_data;
     User_Input result = {};
-    if (app->type_coroutine == Co_View){
-        Coroutine *coroutine = (Coroutine*)app->current_coroutine;
+    if (tctx_info->coroutine != 0){
+        Coroutine *coroutine = (Coroutine*)tctx_info->coroutine;
         if (coroutine != 0){
             Co_Out *out = (Co_Out*)coroutine->out;
             out->request = CoRequest_None;
@@ -2213,8 +2209,8 @@ print_message(Application_Links *app, String_Const_u8 message)
     Editing_File *file = models->message_buffer;
     b32 result = false;
     if (file != 0){
-        output_file_append(models, file, message);
-        file_cursor_to_end(models, file);
+        output_file_append(app->tctx, models, file, message);
+        file_cursor_to_end(app->tctx, models, file);
         result = true;
     }
     return(result);
@@ -2385,7 +2381,7 @@ buffer_history_set_current_state_index(Application_Links *app, Buffer_ID buffer_
     if (api_check_buffer(file) && history_is_activated(&file->state.history)){
         i32 max_index = history_get_record_count(&file->state.history);
         if (0 <= index && index <= max_index){
-            edit_change_current_history_state(models, file, index);
+            edit_change_current_history_state(app->tctx, models, file, index);
             result = true;
         }
     }
@@ -2398,7 +2394,7 @@ buffer_history_merge_record_range(Application_Links *app, Buffer_ID buffer_id, H
     Editing_File *file = imp_get_file(models, buffer_id);
     b32 result = false;
     if (api_check_buffer(file)){
-        result = edit_merge_history_range(models, file, first_index, last_index, flags);
+        result = edit_merge_history_range(app->tctx, models, file, first_index, last_index, flags);
     }
     return(result);
 }
@@ -2502,9 +2498,11 @@ api(custom) function Face_ID
 try_create_new_face(Application_Links *app, Face_Description *description)
 {
     Models *models = (Models*)app->cmd_context;
+    Thread_Context *tctx = app->tctx;
+    Thread_Context_Extra_Info *tctx_info = (Thread_Context_Extra_Info*)tctx->user_data;
     Face_ID result = 0;
-    if (is_running_coroutine(app)){
-        Coroutine *coroutine = (Coroutine*)app->current_coroutine;
+    if (tctx_info != 0 && tctx_info->coroutine != 0){
+        Coroutine *coroutine = (Coroutine*)tctx_info->coroutine;
         Assert(coroutine != 0);
         Co_Out *out = (Co_Out*)coroutine->out;
         out->request = CoRequest_NewFontFace;
@@ -2513,6 +2511,9 @@ try_create_new_face(Application_Links *app, Face_Description *description)
         Co_In *in = (Co_In*)coroutine->in;
         result = in->face_id;
     }
+    else if (tctx_info != 0){
+        // This API does nothing when called from an async thread.
+    }
     else{
         Face *new_face = font_set_new_face(&models->font_set, description);
         result = new_face->id;
@@ -2524,9 +2525,11 @@ api(custom) function b32
 try_modify_face(Application_Links *app, Face_ID id, Face_Description *description)
 {
     Models *models = (Models*)app->cmd_context;
+    Thread_Context *tctx = app->tctx;
+    Thread_Context_Extra_Info *tctx_info = (Thread_Context_Extra_Info*)tctx->user_data;
     b32 result = false;
-    if (is_running_coroutine(app)){
-        Coroutine *coroutine = (Coroutine*)app->current_coroutine;
+    if (tctx_info != 0 && tctx_info->coroutine != 0){
+        Coroutine *coroutine = (Coroutine*)tctx_info->coroutine;
         Assert(coroutine != 0);
         Co_Out *out = (Co_Out*)coroutine->out;
         out->request = CoRequest_ModifyFace;
@@ -2536,6 +2539,9 @@ try_modify_face(Application_Links *app, Face_ID id, Face_Description *descriptio
         Co_In *in = (Co_In*)coroutine->in;
         result = in->success;
     }
+    else if (tctx_info != 0){
+        // This API does nothing when called from an async thread.
+    }
     else{
         result = font_set_modify_face(&models->font_set, id, description);
     }
@@ -2689,8 +2695,9 @@ text_layout_create(Application_Links *app, Buffer_ID buffer_id, Rect_f32 rect, B
     Editing_File *file = imp_get_file(models, buffer_id);
     Text_Layout_ID result = {};
     if (api_check_buffer(file)){
-        Scratch_Block scratch(app);
-        Arena *arena = reserve_arena(models->tctx);
+        Thread_Context *tctx = app->tctx;
+        Scratch_Block scratch(tctx);
+        Arena *arena = reserve_arena(tctx);
         Face *face = file_get_face(models, file);
         
         Gap_Buffer *buffer = &file->state.buffer;
@@ -2702,7 +2709,7 @@ text_layout_create(Application_Links *app, Buffer_ID buffer_id, Rect_f32 rect, B
         f32 y = -buffer_point.pixel_shift.y;
         for (;line_number <= line_count;
              line_number += 1){
-            Buffer_Layout_Item_List line = file_get_line_layout(models, file, dim.x, face, line_number);
+            Buffer_Layout_Item_List line = file_get_line_layout(tctx, models, file, dim.x, face, line_number);
             f32 next_y = y + line.height;
             if (next_y >= dim.y){
                 break;
@@ -2775,7 +2782,7 @@ text_layout_line_on_screen(Application_Links *app, Text_Layout_ID layout_id, i64
             
             for (i64 line_number_it = layout->visible_line_number_range.first;;
                  line_number_it += 1){
-                Buffer_Layout_Item_List line = file_get_line_layout(models, file, width, face, line_number_it);
+                Buffer_Layout_Item_List line = file_get_line_layout(app->tctx, models, file, width, face, line_number_it);
                 result.max += line.height;
                 if (line_number_it == line_number){
                     break;
@@ -2816,7 +2823,7 @@ text_layout_character_on_screen(Application_Links *app, Text_Layout_ID layout_id
                 Buffer_Layout_Item_List line = {};
                 for (i64 line_number_it = layout->visible_line_number_range.first;;
                      line_number_it += 1){
-                    line = file_get_line_layout(models, file, width, face, line_number_it);
+                    line = file_get_line_layout(app->tctx, models, file, width, face, line_number_it);
                     if (line_number_it == line_number){
                         break;
                     }
@@ -2874,7 +2881,7 @@ paint_text_color(Application_Links *app, Text_Layout_ID layout_id, Interval_i64
 api(custom) function b32
 text_layout_free(Application_Links *app, Text_Layout_ID text_layout_id){
     Models *models = (Models*)app->cmd_context;
-    return(text_layout_erase(models, &models->text_layouts, text_layout_id));
+    return(text_layout_erase(app->tctx, models, &models->text_layouts, text_layout_id));
 }
 
 api(custom) function void
@@ -2882,7 +2889,7 @@ draw_text_layout(Application_Links *app, Text_Layout_ID layout_id){
     Models *models = (Models*)app->cmd_context;
     Text_Layout *layout = text_layout_get(&models->text_layouts, layout_id);
     if (layout != 0 && models->target != 0){
-        text_layout_render(models, layout);
+        text_layout_render(app->tctx, models, layout);
     }
 }
 
diff --git a/4ed_app_models.h b/4ed_app_models.h
index 472d406b..cdf8b1d1 100644
--- a/4ed_app_models.h
+++ b/4ed_app_models.h
@@ -35,8 +35,7 @@ enum App_State{
 };
 
 struct Models{
-    Thread_Context *tctx;
-    
+    Arena arena_;
     Arena *arena;
     Heap heap;
     
@@ -50,8 +49,6 @@ struct Models{
     Child_Process_Container child_processes;
     Custom_API config_api;
     
-    Application_Links app_links;
-    
     Render_Caller_Function *render_caller;
     Delta_Rule_Function *delta_rule;
     umem delta_rule_memory_size;
@@ -141,15 +138,6 @@ struct Consumption_Record{
     char consumer[32];
 };
 
-typedef i32 App_Coroutine_Purpose;
-enum{
-    Co_View,
-};
-struct App_Coroutine_State{
-    void *co;
-    i32 type;
-};
-
 struct File_Init{
     String_Const_u8 name;
     Editing_File **ptr;
diff --git a/4ed_app_target.cpp b/4ed_app_target.cpp
index 99dea7e6..ff1dbf0f 100644
--- a/4ed_app_target.cpp
+++ b/4ed_app_target.cpp
@@ -79,7 +79,6 @@
 #define DYNAMIC_LINK_API
 #include "generated/font_api.cpp"
 
-#include "4ed_allocator_models.cpp"
 #include "4ed_log.cpp"
 #include "4ed_coroutine.cpp"
 #include "4ed_mem.cpp"
diff --git a/4ed_cli.cpp b/4ed_cli.cpp
index 72cc8b5e..3c219ef8 100644
--- a/4ed_cli.cpp
+++ b/4ed_cli.cpp
@@ -98,9 +98,9 @@ child_process_lookup_return_code(Child_Process_Container *container, Child_Proce
 ////////////////////////////////
 
 internal b32
-child_process_call(Models *models, String_Const_u8 path, String_Const_u8 command, Child_Process_ID *id_out){
+child_process_call(Thread_Context *tctx, Models *models, String_Const_u8 path, String_Const_u8 command, Child_Process_ID *id_out){
     b32 result = false;
-    Scratch_Block scratch(&models->app_links);
+    Scratch_Block scratch(tctx);
     String_Const_u8 path_n = push_string_copy(scratch, path);
     String_Const_u8 command_n = push_string_copy(scratch, command);
     CLI_Handles cli_handles = {};
diff --git a/4ed_coroutine.cpp b/4ed_coroutine.cpp
index d14823a5..10224a9d 100644
--- a/4ed_coroutine.cpp
+++ b/4ed_coroutine.cpp
@@ -30,9 +30,13 @@ internal void
 coroutine_main(void *ptr){
     Coroutine *me = (Coroutine*)ptr;
     
+    Thread_Context_Extra_Info tctx_info = {};
+    tctx_info.coroutine = me;
+    
     Thread_Context tctx_ = {};
     thread_ctx_init(&tctx_, ThreadKind_MainCoroutine,
                     get_base_allocator_system(), get_base_allocator_system());
+    tctx_.user_data = &tctx_info;
     me->tctx = &tctx_;
     
     // NOTE(allen): Init handshake
diff --git a/4ed_dynamic_variables.cpp b/4ed_dynamic_variables.cpp
index 5dad2e76..48779479 100644
--- a/4ed_dynamic_variables.cpp
+++ b/4ed_dynamic_variables.cpp
@@ -67,6 +67,7 @@ internal void
 lifetime_allocator_init(Base_Allocator *base_allocator, Lifetime_Allocator *lifetime_allocator){
     block_zero_struct(lifetime_allocator);
     lifetime_allocator->allocator = base_allocator;
+    lifetime_allocator->node_arena = make_arena(base_allocator, KB(4));
     lifetime_allocator->key_table = make_table_Data_u64(base_allocator, 100);
     lifetime_allocator->key_check_table = make_table_u64_u64(base_allocator, 100);
     lifetime_allocator->scope_id_to_scope_ptr_table = make_table_u64_u64(base_allocator, 100);
@@ -250,26 +251,15 @@ lifetime__object_add_key(Lifetime_Allocator *lifetime_allocator, Lifetime_Object
 
 internal Lifetime_Object*
 lifetime_alloc_object(Lifetime_Allocator *lifetime_allocator, i32 user_type, void *user_back_ptr){
-    Lifetime_Object *object = lifetime_allocator->free_objects.first;
+    Lifetime_Object *object = lifetime_allocator->free_objects;
     if (object == 0){
-        i32 new_object_count = 256;
-        umem new_memory_size = new_object_count*sizeof(Lifetime_Object);
-        Data new_memory = base_allocate(lifetime_allocator->allocator, new_memory_size);
-        Lifetime_Object *new_objects = (Lifetime_Object*)new_memory.data;
-        Lifetime_Object *new_object_ptr = new_objects;
-        for (i32 i = 0; i < new_object_count; i += 1, new_object_ptr += 1){
-            zdll_push_back(lifetime_allocator->free_objects.first, lifetime_allocator->free_objects.last, new_object_ptr);
-        }
-        lifetime_allocator->free_objects.count += new_object_count;
-        object = lifetime_allocator->free_objects.first;
+        object = push_array(&lifetime_allocator->node_arena, Lifetime_Object, 1);
+    }
+    else{
+        sll_stack_pop(lifetime_allocator->free_objects);
     }
-    
-    zdll_remove(lifetime_allocator->free_objects.first, lifetime_allocator->free_objects.last, object);
-    lifetime_allocator->free_objects.count -= 1;
-    
     block_zero_struct(object);
     dynamic_workspace_init(lifetime_allocator, user_type, user_back_ptr, &object->workspace);
-    
     return(object);
 }
 
@@ -313,7 +303,7 @@ internal void
 lifetime_free_object(Lifetime_Allocator *lifetime_allocator, Lifetime_Object *lifetime_object){
     lifetime__object_free_all_keys(lifetime_allocator, lifetime_object);
     dynamic_workspace_free(lifetime_allocator, &lifetime_object->workspace);
-    zdll_push_back(lifetime_allocator->free_objects.first, lifetime_allocator->free_objects.last, lifetime_object);
+    sll_stack_push(lifetime_allocator->free_objects, lifetime_object);
 }
 
 internal void
diff --git a/4ed_dynamic_variables.h b/4ed_dynamic_variables.h
index 5cb2e4db..1f8352ae 100644
--- a/4ed_dynamic_variables.h
+++ b/4ed_dynamic_variables.h
@@ -98,18 +98,13 @@ struct Lifetime_Key_Ref_Node{
     struct Lifetime_Key *keys[lifetime_key_reference_per_node];
 };
 
-struct Lifetime_Object{
-    union{
-        struct{
-            Lifetime_Object *next;
-            Lifetime_Object *prev;
-        };
-        struct{
-            Lifetime_Key_Ref_Node *key_node_first;
-            Lifetime_Key_Ref_Node *key_node_last;
-            i32 key_count;
-            Dynamic_Workspace workspace;
-        };
+union Lifetime_Object{
+    Lifetime_Object *next;
+    struct{
+        Lifetime_Key_Ref_Node *key_node_first;
+        Lifetime_Key_Ref_Node *key_node_last;
+        i32 key_count;
+        Dynamic_Workspace workspace;
     };
 };
 
@@ -120,7 +115,7 @@ struct Lifetime_Key{
             Lifetime_Key *prev;
         };
         struct{
-            struct Lifetime_Object **members;
+            Lifetime_Object **members;
             i32 count;
             Dynamic_Workspace dynamic_workspace;
         };
@@ -136,12 +131,6 @@ struct Lifetime_Key_Ref_Node_List{
     i32 count;
 };
 
-struct Lifetime_Object_List{
-    Lifetime_Object *first;
-    Lifetime_Object *last;
-    i32 count;
-};
-
 struct Lifetime_Key_List{
     Lifetime_Key *first;
     Lifetime_Key *last;
@@ -150,8 +139,9 @@ struct Lifetime_Key_List{
 
 struct Lifetime_Allocator{
     Base_Allocator *allocator;
+    Arena node_arena;
     Lifetime_Key_Ref_Node_List free_key_references;
-    Lifetime_Object_List free_objects;
+    Lifetime_Object *free_objects;
     Lifetime_Key_List free_keys;
     Table_Data_u64 key_table;
     Table_u64_u64 key_check_table;
diff --git a/4ed_edit.cpp b/4ed_edit.cpp
index 558d891c..1d9a28d1 100644
--- a/4ed_edit.cpp
+++ b/4ed_edit.cpp
@@ -70,7 +70,7 @@ edit_fix_markers__compute_scroll_y(i32 line_height, i32 old_y_val, f32 new_y_val
 }
 
 internal void
-edit_fix_markers(Models *models, Editing_File *file, Edit edit){
+edit_fix_markers(Thread_Context *tctx, Models *models, Editing_File *file, Edit edit){
     Layout *layout = &models->layout;
     
     Lifetime_Object *file_lifetime_object = file->lifetime_object;
@@ -97,7 +97,7 @@ edit_fix_markers(Models *models, Editing_File *file, Edit edit){
     }
     cursor_max += total_marker_count;
     
-    Scratch_Block scratch(models->tctx, Scratch_Share);
+    Scratch_Block scratch(tctx, Scratch_Share);
     
     Cursor_With_Index *cursors = push_array(scratch, Cursor_With_Index, cursor_max);
     Cursor_With_Index *r_cursors = push_array(scratch, Cursor_With_Index, cursor_max);
@@ -155,7 +155,7 @@ edit_fix_markers(Models *models, Editing_File *file, Edit edit){
                 i64 cursor_pos = cursors[cursor_count++].pos;
                 view->mark = cursors[cursor_count++].pos;
                 File_Edit_Positions edit_pos = view_get_edit_pos(view);
-                view_set_cursor_and_scroll(models, view, cursor_pos, edit_pos.scroll);
+                view_set_cursor_and_scroll(tctx, models, view, cursor_pos, edit_pos.scroll);
                 // TODO(allen): read a cursor for the current scroll line
             }
         }
@@ -178,7 +178,7 @@ edit_fix_markers(Models *models, Editing_File *file, Edit edit){
 }
 
 internal void
-edit_single(Models *models, Editing_File *file, Interval_i64 range, String_Const_u8 string, Edit_Behaviors behaviors){
+edit_single(Thread_Context *tctx, Models *models, Editing_File *file, Interval_i64 range, String_Const_u8 string, Edit_Behaviors behaviors){
     Edit edit = {};
     edit.text = string;
     edit.range = range;
@@ -188,7 +188,7 @@ edit_single(Models *models, Editing_File *file, Interval_i64 range, String_Const
     Assert(edit.range.first <= edit.range.one_past_last);
     Assert(edit.range.one_past_last <= buffer_size(buffer));
     
-    Scratch_Block scratch(models->tctx, Scratch_Share);
+    Scratch_Block scratch(tctx, Scratch_Share);
     
     // NOTE(allen): history update
     if (!behaviors.do_not_post_to_history){
@@ -223,19 +223,25 @@ edit_single(Models *models, Editing_File *file, Interval_i64 range, String_Const
     buffer_remeasure_starts(scratch, buffer, Ii64(line_start, line_end + 1), line_shift, shift_amount);
     
     // NOTE(allen): cursor fixing
-    edit_fix_markers(models, file, edit);
+    edit_fix_markers(tctx, models, file, edit);
     
     // NOTE(allen): edit range hook
     if (models->buffer_edit_range != 0){
         Interval_i64 new_range = Ii64(edit.range.first, edit.range.first + edit.text.size);
-        models->buffer_edit_range(&models->app_links, file->id, new_range, original_text);
+        Application_Links app = {};
+        app.tctx = tctx;;
+        app.cmd_context = models;
+        models->buffer_edit_range(&app, file->id, new_range, original_text);
     }
 }
 
 internal void
-file_end_file(Models *models, Editing_File *file){
+file_end_file(Thread_Context *tctx, Models *models, Editing_File *file){
     if (models->end_buffer != 0){
-        models->end_buffer(&models->app_links, file->id);
+        Application_Links app = {};
+        app.tctx = tctx;
+        app.cmd_context = models;
+        models->end_buffer(&app, file->id);
     }
     Lifetime_Allocator *lifetime_allocator = &models->lifetime_allocator;
     lifetime_free_object(lifetime_allocator, file->lifetime_object);
@@ -243,7 +249,7 @@ file_end_file(Models *models, Editing_File *file){
 }
 
 internal void
-edit__apply_record_forward(Models *models, Editing_File *file, Record *record, Edit_Behaviors behaviors_prototype){
+edit__apply_record_forward(Thread_Context *tctx, Models *models, Editing_File *file, Record *record, Edit_Behaviors behaviors_prototype){
     // NOTE(allen): // NOTE(allen): // NOTE(allen): // NOTE(allen): // NOTE(allen): 
     // Whenever you change this also change the backward version!
     
@@ -252,7 +258,7 @@ edit__apply_record_forward(Models *models, Editing_File *file, Record *record, E
         {
             String_Const_u8 str = record->single.forward_text;
             Interval_i64 range = Ii64(record->single.first, record->single.first + record->single.backward_text.size);
-            edit_single(models, file, range, str, behaviors_prototype);
+            edit_single(tctx, models, file, range, str, behaviors_prototype);
         }break;
         
         case RecordKind_Group:
@@ -262,7 +268,7 @@ edit__apply_record_forward(Models *models, Editing_File *file, Record *record, E
                  node != sentinel;
                  node = node->next){
                 Record *sub_record = CastFromMember(Record, node, node);
-                edit__apply_record_forward(models, file, sub_record, behaviors_prototype);
+                edit__apply_record_forward(tctx, models, file, sub_record, behaviors_prototype);
             }
         }break;
         
@@ -274,7 +280,7 @@ edit__apply_record_forward(Models *models, Editing_File *file, Record *record, E
 }
 
 internal void
-edit__apply_record_backward(Models *models, Editing_File *file, Record *record, Edit_Behaviors behaviors_prototype){
+edit__apply_record_backward(Thread_Context *tctx, Models *models, Editing_File *file, Record *record, Edit_Behaviors behaviors_prototype){
     // NOTE(allen): // NOTE(allen): // NOTE(allen): // NOTE(allen): // NOTE(allen): 
     // Whenever you change this also change the forward version!
     
@@ -283,7 +289,7 @@ edit__apply_record_backward(Models *models, Editing_File *file, Record *record,
         {
             String_Const_u8 str = record->single.backward_text;
             Interval_i64 range = Ii64(record->single.first, record->single.first + record->single.forward_text.size);
-            edit_single(models, file, range, str, behaviors_prototype);
+            edit_single(tctx, models, file, range, str, behaviors_prototype);
         }break;
         
         case RecordKind_Group:
@@ -293,7 +299,7 @@ edit__apply_record_backward(Models *models, Editing_File *file, Record *record,
                  node != sentinel;
                  node = node->prev){
                 Record *sub_record = CastFromMember(Record, node, node);
-                edit__apply_record_backward(models, file, sub_record, behaviors_prototype);
+                edit__apply_record_backward(tctx, models, file, sub_record, behaviors_prototype);
             }
         }break;
         
@@ -305,7 +311,7 @@ edit__apply_record_backward(Models *models, Editing_File *file, Record *record,
 }
 
 internal void
-edit_change_current_history_state(Models *models, Editing_File *file, i32 target_index){
+edit_change_current_history_state(Thread_Context *tctx, Models *models, Editing_File *file, i32 target_index){
     History *history = &file->state.history;
     if (history->activated && file->state.current_record_index != target_index){
         Assert(0 <= target_index && target_index <= history->record_count);
@@ -323,13 +329,13 @@ edit_change_current_history_state(Models *models, Editing_File *file, i32 target
                 current += 1;
                 record = CastFromMember(Record, node, record->node.next);
                 Assert(record != dummy_record);
-                edit__apply_record_forward(models, file, record, behaviors_prototype);
+                edit__apply_record_forward(tctx, models, file, record, behaviors_prototype);
             } while (current != target_index);
         }
         else{
             do{
                 Assert(record != dummy_record);
-                edit__apply_record_backward(models, file, record, behaviors_prototype);
+                edit__apply_record_backward(tctx, models, file, record, behaviors_prototype);
                 current -= 1;
                 record = CastFromMember(Record, node, record->node.prev);
             } while (current != target_index);
@@ -340,7 +346,7 @@ edit_change_current_history_state(Models *models, Editing_File *file, i32 target
 }
 
 internal b32
-edit_merge_history_range(Models *models, Editing_File *file, History_Record_Index first_index, History_Record_Index last_index, Record_Merge_Flag flags){
+edit_merge_history_range(Thread_Context *tctx, Models *models, Editing_File *file, History_Record_Index first_index, History_Record_Index last_index, Record_Merge_Flag flags){
     b32 result = false;
     History *history = &file->state.history;
     if (history_is_activated(history)){
@@ -354,13 +360,13 @@ edit_merge_history_range(Models *models, Editing_File *file, History_Record_Inde
                     switch (in_range_handler){
                         case RecordMergeFlag_StateInRange_MoveStateForward:
                         {
-                            edit_change_current_history_state(models, file, last_index);
+                            edit_change_current_history_state(tctx, models, file, last_index);
                             current_index = last_index;
                         }break;
                         
                         case RecordMergeFlag_StateInRange_MoveStateBackward:
                         {
-                            edit_change_current_history_state(models, file, first_index);
+                            edit_change_current_history_state(tctx, models, file, first_index);
                             current_index = first_index;
                         }break;
                         
@@ -370,7 +376,7 @@ edit_merge_history_range(Models *models, Editing_File *file, History_Record_Inde
                         }break;
                     }
                 }
-                Scratch_Block scratch(models->tctx, Scratch_Share);
+                Scratch_Block scratch(tctx, Scratch_Share);
                 history_merge_records(scratch, history, first_index, last_index);
                 if (current_index >= last_index){
                     current_index -= (last_index - first_index);
@@ -385,7 +391,7 @@ edit_merge_history_range(Models *models, Editing_File *file, History_Record_Inde
 }
 
 internal b32
-edit_batch(Models *models, Editing_File *file, Batch_Edit *batch, Edit_Behaviors behaviors){
+edit_batch(Thread_Context *tctx, Models *models, Editing_File *file, Batch_Edit *batch, Edit_Behaviors behaviors){
     b32 result = true;
     if (batch != 0){
         History_Record_Index start_index = 0;
@@ -405,7 +411,7 @@ edit_batch(Models *models, Editing_File *file, Batch_Edit *batch, Edit_Behaviors
             if (0 <= edit_range.first &&
                 edit_range.first <= edit_range.one_past_last &&
                 edit_range.one_past_last <= size){
-                edit_single(models, file, edit_range, insert_string, behaviors);
+                edit_single(tctx, models, file, edit_range, insert_string, behaviors);
                 shift += replace_range_shift(edit_range, insert_string.size);
             }
             else{
@@ -417,7 +423,7 @@ edit_batch(Models *models, Editing_File *file, Batch_Edit *batch, Edit_Behaviors
         if (history_is_activated(&file->state.history)){
             History_Record_Index last_index = file->state.current_record_index;
             if (start_index + 1 < last_index){
-                edit_merge_history_range(models, file, start_index + 1, last_index, RecordMergeFlag_StateInRange_ErrorOut);
+                edit_merge_history_range(tctx, models, file, start_index + 1, last_index, RecordMergeFlag_StateInRange_ErrorOut);
             }
         }
     }
@@ -427,14 +433,14 @@ edit_batch(Models *models, Editing_File *file, Batch_Edit *batch, Edit_Behaviors
 ////////////////////////////////
 
 internal Editing_File*
-create_file(Models *models, String_Const_u8 file_name, Buffer_Create_Flag flags){
+create_file(Thread_Context *tctx, Models *models, String_Const_u8 file_name, Buffer_Create_Flag flags){
     Editing_File *result = 0;
     
     if (file_name.size > 0){
         Working_Set *working_set = &models->working_set;
         Heap *heap = &models->heap;
         
-        Scratch_Block scratch(models->tctx);
+        Scratch_Block scratch(tctx);
         
         Editing_File *file = 0;
         b32 do_empty_buffer = false;
@@ -487,9 +493,9 @@ create_file(Models *models, String_Const_u8 file_name, Buffer_Create_Flag flags)
                             file_bind_file_name(working_set, file, string_from_file_name(&canon));
                         }
                         String_Const_u8 front = string_front_of_path(file_name);
-                        buffer_bind_name(models, scratch, working_set, file, front);
+                        buffer_bind_name(tctx, models, scratch, working_set, file, front);
                         File_Attributes attributes = {};
-                        file_create_from_string(models, file, SCu8(""), attributes);
+                        file_create_from_string(tctx, models, file, SCu8(""), attributes);
                         result = file;
                     }
                 }
@@ -511,8 +517,8 @@ create_file(Models *models, String_Const_u8 file_name, Buffer_Create_Flag flags)
                     if (file != 0){
                         file_bind_file_name(working_set, file, string_from_file_name(&canon));
                         String_Const_u8 front = string_front_of_path(file_name);
-                        buffer_bind_name(models, scratch, working_set, file, front);
-                        file_create_from_string(models, file, SCu8(buffer, (i32)attributes.size), attributes);
+                        buffer_bind_name(tctx, models, scratch, working_set, file, front);
+                        file_create_from_string(tctx, models, file, SCu8(buffer, (i32)attributes.size), attributes);
                         result = file;
                     }
                 }
@@ -537,7 +543,7 @@ create_file(Models *models, String_Const_u8 file_name, Buffer_Create_Flag flags)
             i64 size = buffer_size(&file->state.buffer);
             if (size > 0){
                 Edit_Behaviors behaviors = {};
-                edit_single(models, file, Ii64(0, size), string_u8_litexpr(""), behaviors);
+                edit_single(tctx, models, file, Ii64(0, size), string_u8_litexpr(""), behaviors);
                 if (has_canon_name){
                     buffer_is_for_new_file = true;
                 }
@@ -547,7 +553,10 @@ create_file(Models *models, String_Const_u8 file_name, Buffer_Create_Flag flags)
         if (file != 0 && buffer_is_for_new_file &&
             !HasFlag(flags, BufferCreate_SuppressNewFileHook) &&
             models->new_file != 0){
-            models->new_file(&models->app_links, file->id);
+            Application_Links app = {};
+            app.tctx = tctx;
+            app.cmd_context = models;
+            models->new_file(&app, file->id);
         }
     }
     
diff --git a/4ed_file.cpp b/4ed_file.cpp
index 43b436bb..825904cd 100644
--- a/4ed_file.cpp
+++ b/4ed_file.cpp
@@ -137,7 +137,7 @@ file_name_terminate(Editing_File_Name *name){
 
 // TODO(allen): file_name should be String_Const_u8
 internal b32
-save_file_to_name(Models *models, Editing_File *file, u8 *file_name){
+save_file_to_name(Thread_Context *tctx, Models *models, Editing_File *file, u8 *file_name){
     b32 result = false;
     b32 using_actual_file_name = false;
     
@@ -149,13 +149,16 @@ save_file_to_name(Models *models, Editing_File *file, u8 *file_name){
     
     if (file_name != 0){
         if (models->save_file != 0){
-            models->save_file(&models->app_links, file->id);
+            Application_Links app = {};
+            app.tctx = tctx;
+            app.cmd_context = models;
+            models->save_file(&app, file->id);
         }
         
         Gap_Buffer *buffer = &file->state.buffer;
         b32 dos_write_mode = file->settings.dos_write_mode;
         
-        Scratch_Block scratch(models->tctx, Scratch_Share);
+        Scratch_Block scratch(tctx, Scratch_Share);
         
         if (!using_actual_file_name){
             String_Const_u8 s_file_name = SCu8(file_name);
@@ -181,8 +184,8 @@ save_file_to_name(Models *models, Editing_File *file, u8 *file_name){
 }
 
 internal b32
-save_file(Models *models, Editing_File *file){
-    return(save_file_to_name(models, file, 0));
+save_file(Thread_Context *tctx, Models *models, Editing_File *file){
+    return(save_file_to_name(tctx, models, file, 0));
 }
 
 ////////////////////////////////
@@ -206,8 +209,7 @@ file_compute_cursor(Editing_File *file, Buffer_Seek seek){
 ////////////////////////////////
 
 internal void
-file_create_from_string(Models *models, Editing_File *file, String_Const_u8 val, File_Attributes attributes){
-    Thread_Context *tctx = models->tctx;
+file_create_from_string(Thread_Context *tctx, Models *models, Editing_File *file, String_Const_u8 val, File_Attributes attributes){
     Scratch_Block scratch(tctx, Scratch_Share);
     
     Base_Allocator *allocator = tctx->allocator;
@@ -225,7 +227,7 @@ file_create_from_string(Models *models, Editing_File *file, String_Const_u8 val,
     buffer_measure_starts(scratch, &file->state.buffer);
     
     file->lifetime_object = lifetime_alloc_object(&models->lifetime_allocator, DynamicWorkspace_Buffer, file);
-    history_init(models, &file->state.history);
+    history_init(tctx, models, &file->state.history);
     
     file->state.cached_layouts_arena = make_arena(allocator);
     file->state.line_layout_table = make_table_Data_u64(allocator, 500);
@@ -245,12 +247,15 @@ file_create_from_string(Models *models, Editing_File *file, String_Const_u8 val,
     ////////////////////////////////
     
     if (models->begin_buffer != 0){
-        models->begin_buffer(&models->app_links, file->id);
+        Application_Links app = {};
+        app.tctx = tctx;
+        app.cmd_context = models;
+        models->begin_buffer(&app, file->id);
     }
 }
 
 internal void
-file_free(Models *models, Editing_File *file){
+file_free(Thread_Context *tctx, Models *models, Editing_File *file){
     Lifetime_Allocator *lifetime_allocator = &models->lifetime_allocator;
     Working_Set *working_set = &models->working_set;
     
@@ -262,7 +267,7 @@ file_free(Models *models, Editing_File *file){
         base_free(buffer->allocator, buffer->line_starts);
     }
     
-    history_free(models, &file->state.history);
+    history_free(tctx, &file->state.history);
     
     linalloc_clear(&file->state.cached_layouts_arena);
     table_free(&file->state.line_layout_table);
@@ -288,7 +293,7 @@ file_get_managed_scope(Editing_File *file){
 ////////////////////////////////
 
 internal Buffer_Layout_Item_List
-file_get_line_layout(Models *models, Editing_File *file, f32 width, Face *face, i64 line_number){
+file_get_line_layout(Thread_Context *tctx, Models *models, Editing_File *file, f32 width, Face *face, i64 line_number){
     Buffer_Layout_Item_List result = {};
     
     i64 line_count = buffer_line_count(&file->state.buffer);
@@ -312,7 +317,7 @@ file_get_line_layout(Models *models, Editing_File *file, f32 width, Face *face,
         else{
             list = push_array(&file->state.cached_layouts_arena, Buffer_Layout_Item_List, 1);
             Interval_i64 line_range = buffer_get_pos_range_from_line_number(&file->state.buffer, line_number);
-            *list = buffer_layout(models->tctx, &file->state.cached_layouts_arena,
+            *list = buffer_layout(tctx, &file->state.cached_layouts_arena,
                                   &file->state.buffer, line_range, face, width);
             key_data = push_data_copy(&file->state.cached_layouts_arena, key_data);
             table_insert(&file->state.line_layout_table, key_data, (u64)PtrAsInt(list));
@@ -330,7 +335,7 @@ file_clear_layout_cache(Editing_File *file){
 }
 
 internal Line_Shift_Vertical
-file_line_shift_y(Models *models, Editing_File *file, f32 width, Face *face, i64 line_number, f32 y_delta){
+file_line_shift_y(Thread_Context *tctx, Models *models, Editing_File *file, f32 width, Face *face, i64 line_number, f32 y_delta){
     Line_Shift_Vertical result = {};
     
     f32 line_y = 0.f;
@@ -350,7 +355,7 @@ file_line_shift_y(Models *models, Editing_File *file, f32 width, Face *face, i64
                 line_number = 1;
                 break;
             }
-            Buffer_Layout_Item_List line = file_get_line_layout(models, file, width, face, line_number);
+            Buffer_Layout_Item_List line = file_get_line_layout(tctx, models, file, width, face, line_number);
             line_y -= line.height;
         }
         if (!has_result){
@@ -363,7 +368,7 @@ file_line_shift_y(Models *models, Editing_File *file, f32 width, Face *face, i64
         b32 has_result = false;
         i64 line_count = buffer_line_count(&file->state.buffer);
         for (;;line_number += 1){
-            Buffer_Layout_Item_List line = file_get_line_layout(models, file, width, face, line_number);
+            Buffer_Layout_Item_List line = file_get_line_layout(tctx, models, file, width, face, line_number);
             f32 next_y = line_y + line.height;
             if (y_delta < next_y){
                 has_result = true;
@@ -386,12 +391,12 @@ file_line_shift_y(Models *models, Editing_File *file, f32 width, Face *face, i64
 }
 
 internal f32
-file_line_y_difference(Models *models, Editing_File *file, f32 width, Face *face, i64 line_a, i64 line_b){
+file_line_y_difference(Thread_Context *tctx, Models *models, Editing_File *file, f32 width, Face *face, i64 line_a, i64 line_b){
     f32 result = 0.f;
     if (line_a != line_b){
         Interval_i64 line_range = Ii64(line_a, line_b);
         for (i64 i = line_range.min; i < line_range.max; i += 1){
-            Buffer_Layout_Item_List line = file_get_line_layout(models, file, width, face, i);
+            Buffer_Layout_Item_List line = file_get_line_layout(tctx, models, file, width, face, i);
             result += line.height;
         }
         if (line_a < line_b){
@@ -402,25 +407,25 @@ file_line_y_difference(Models *models, Editing_File *file, f32 width, Face *face
 }
 
 internal i64
-file_pos_at_relative_xy(Models *models, Editing_File *file, f32 width, Face *face, i64 base_line, Vec2_f32 relative_xy){
-    Line_Shift_Vertical shift = file_line_shift_y(models, file, width, face, base_line, relative_xy.y);
+file_pos_at_relative_xy(Thread_Context *tctx, Models *models, Editing_File *file, f32 width, Face *face, i64 base_line, Vec2_f32 relative_xy){
+    Line_Shift_Vertical shift = file_line_shift_y(tctx, models, file, width, face, base_line, relative_xy.y);
     relative_xy.y -= shift.y_delta;
-    Buffer_Layout_Item_List line = file_get_line_layout(models, file, width, face, shift.line);
+    Buffer_Layout_Item_List line = file_get_line_layout(tctx, models, file, width, face, shift.line);
     return(buffer_layout_nearest_pos_to_xy(line, relative_xy));
 }
 
 internal Vec2_f32
-file_relative_xy_of_pos(Models *models, Editing_File *file, f32 width, Face *face, i64 base_line, i64 pos){
+file_relative_xy_of_pos(Thread_Context *tctx, Models *models, Editing_File *file, f32 width, Face *face, i64 base_line, i64 pos){
     i64 line_number = buffer_get_line_index(&file->state.buffer, pos) + 1;
-    Buffer_Layout_Item_List line = file_get_line_layout(models, file, width, face, line_number);
+    Buffer_Layout_Item_List line = file_get_line_layout(tctx, models, file, width, face, line_number);
     Vec2_f32 result = buffer_layout_xy_center_of_pos(line, pos);
-    result.y += file_line_y_difference(models, file, width, face, line_number, base_line);
+    result.y += file_line_y_difference(tctx, models, file, width, face, line_number, base_line);
     return(result);
 }
 
 internal Buffer_Point
-file_normalize_buffer_point(Models *models, Editing_File *file, f32 width, Face *face, Buffer_Point point){
-    Line_Shift_Vertical shift = file_line_shift_y(models, file, width, face, point.line_number, point.pixel_shift.y);
+file_normalize_buffer_point(Thread_Context *tctx, Models *models, Editing_File *file, f32 width, Face *face, Buffer_Point point){
+    Line_Shift_Vertical shift = file_line_shift_y(tctx, models, file, width, face, point.line_number, point.pixel_shift.y);
     point.line_number = shift.line;
     point.pixel_shift.y -= shift.y_delta;
     point.pixel_shift.x = clamp_bot(0.f, point.pixel_shift.x);
@@ -429,15 +434,15 @@ file_normalize_buffer_point(Models *models, Editing_File *file, f32 width, Face
 }
 
 internal Vec2_f32
-file_buffer_point_difference(Models *models, Editing_File *file, f32 width, Face *face, Buffer_Point a, Buffer_Point b){
-    f32 y_difference = file_line_y_difference(models, file, width, face, a.line_number, b.line_number);
+file_buffer_point_difference(Thread_Context *tctx, Models *models, Editing_File *file, f32 width, Face *face, Buffer_Point a, Buffer_Point b){
+    f32 y_difference = file_line_y_difference(tctx, models, file, width, face, a.line_number, b.line_number);
     Vec2_f32 result = a.pixel_shift - b.pixel_shift;
     result.y += y_difference;
     return(result);
 }
 
 internal Line_Shift_Character
-file_line_shift_characters(Models *models, Editing_File *file, f32 width, Face *face, i64 line_number, i64 character_delta){
+file_line_shift_characters(Thread_Context *tctx, Models *models, Editing_File *file, f32 width, Face *face, i64 line_number, i64 character_delta){
     Line_Shift_Character result = {};
     
     i64 line_character = 0;
@@ -457,7 +462,7 @@ file_line_shift_characters(Models *models, Editing_File *file, f32 width, Face *
                 line_number = 1;
                 break;
             }
-            Buffer_Layout_Item_List line = file_get_line_layout(models, file, width, face, line_number);
+            Buffer_Layout_Item_List line = file_get_line_layout(tctx, models, file, width, face, line_number);
             line_character -= line.character_count;
         }
         if (!has_result){
@@ -470,7 +475,7 @@ file_line_shift_characters(Models *models, Editing_File *file, f32 width, Face *
         b32 has_result = false;
         i64 line_count = buffer_line_count(&file->state.buffer);
         for (;;line_number += 1){
-            Buffer_Layout_Item_List line = file_get_line_layout(models, file, width, face, line_number);
+            Buffer_Layout_Item_List line = file_get_line_layout(tctx, models, file, width, face, line_number);
             i64 next_character = line_character + line.character_count;
             if (character_delta < next_character){
                 has_result = true;
@@ -493,12 +498,12 @@ file_line_shift_characters(Models *models, Editing_File *file, f32 width, Face *
 }
 
 internal i64
-file_line_character_difference(Models *models, Editing_File *file, f32 width, Face *face, i64 line_a, i64 line_b){
+file_line_character_difference(Thread_Context *tctx, Models *models, Editing_File *file, f32 width, Face *face, i64 line_a, i64 line_b){
     i64 result = 0;
     if (line_a != line_b){
         Interval_i64 line_range = Ii64(line_a, line_b);
         for (i64 i = line_range.min; i < line_range.max; i += 1){
-            Buffer_Layout_Item_List line = file_get_line_layout(models, file, width, face, i);
+            Buffer_Layout_Item_List line = file_get_line_layout(tctx, models, file, width, face, i);
             result += line.character_count;
         }
         if (line_a < line_b){
@@ -509,19 +514,19 @@ file_line_character_difference(Models *models, Editing_File *file, f32 width, Fa
 }
 
 internal i64
-file_pos_from_relative_character(Models *models, Editing_File *file, f32 width, Face *face, i64 base_line, i64 relative_character){
-    Line_Shift_Character shift = file_line_shift_characters(models, file, width, face, base_line, relative_character);
+file_pos_from_relative_character(Thread_Context *tctx, Models *models, Editing_File *file, f32 width, Face *face, i64 base_line, i64 relative_character){
+    Line_Shift_Character shift = file_line_shift_characters(tctx, models, file, width, face, base_line, relative_character);
     relative_character -= shift.character_delta;
-    Buffer_Layout_Item_List line = file_get_line_layout(models, file, width, face, shift.line);
+    Buffer_Layout_Item_List line = file_get_line_layout(tctx, models, file, width, face, shift.line);
     return(buffer_layout_get_pos_at_character(line, relative_character));
 }
 
 internal i64
-file_relative_character_from_pos(Models *models, Editing_File *file, f32 width, Face *face, i64 base_line, i64 pos){
+file_relative_character_from_pos(Thread_Context *tctx, Models *models, Editing_File *file, f32 width, Face *face, i64 base_line, i64 pos){
     i64 line_number = buffer_get_line_index(&file->state.buffer, pos) + 1;
-    Buffer_Layout_Item_List line = file_get_line_layout(models, file, width, face, line_number);
+    Buffer_Layout_Item_List line = file_get_line_layout(tctx, models, file, width, face, line_number);
     i64 result = buffer_layout_character_from_pos(line, pos);
-    result += file_line_character_difference(models, file, width, face, line_number, base_line);
+    result += file_line_character_difference(tctx, models, file, width, face, line_number, base_line);
     return(result);
 }
 
diff --git a/4ed_history.cpp b/4ed_history.cpp
index 1cceeaf4..d18e84b1 100644
--- a/4ed_history.cpp
+++ b/4ed_history.cpp
@@ -129,9 +129,8 @@ global_history_adjust_edit_grouping_counter(Global_History *global_history, i32
 }
 
 internal void
-history_init(Models *models, History *history){
+history_init(Thread_Context *tctx, Models *models, History *history){
     history->activated = true;
-    Thread_Context *tctx = models->tctx;
     history->arena = reserve_arena(tctx, KB(32));
     heap_init(&history->heap, tctx->allocator);
     history->heap_wrapper = base_allocator_on_heap(&history->heap);
@@ -147,9 +146,9 @@ history_is_activated(History *history){
 }
 
 internal void
-history_free(Models *models, History *history){
+history_free(Thread_Context *tctx, History *history){
     if (history->activated){
-        release_arena(models, history->arena);
+        release_arena(tctx, history->arena);
         heap_free_all(&history->heap);
         block_zero_struct(history);
     }
diff --git a/4ed_log.cpp b/4ed_log.cpp
index 51f3d45c..de9eee94 100644
--- a/4ed_log.cpp
+++ b/4ed_log.cpp
@@ -31,10 +31,10 @@ log_string(String_Const_u8 str){
 }
 
 internal void
-output_file_append(Models *models, Editing_File *file, String_Const_u8 value);
+output_file_append(Thread_Context *tctx, Models *models, Editing_File *file, String_Const_u8 value);
 
 internal b32
-log_flush(Models *models){
+log_flush(Thread_Context *tctx, Models *models){
     b32 result = false;
     
     system_mutex_acquire(global_log.mutex);
@@ -42,7 +42,7 @@ log_flush(Models *models){
     
     if (global_log.list.total_size > 0){
         String_Const_u8 text = string_list_flatten(&global_log.arena, global_log.list);
-        output_file_append(models, models->log_buffer, text);
+        output_file_append(tctx, models, models->log_buffer, text);
         result = true;
     }
     linalloc_clear(&global_log.arena);
diff --git a/4ed_text_layout.cpp b/4ed_text_layout.cpp
index 1e72bd8b..1057d534 100644
--- a/4ed_text_layout.cpp
+++ b/4ed_text_layout.cpp
@@ -10,10 +10,10 @@
 // TOP
 
 internal void
-text_layout_init(Models *models, Text_Layout_Container *container){
+text_layout_init(Thread_Context *tctx, Text_Layout_Container *container){
     block_zero_struct(container);
-    container->node_arena = reserve_arena(models->tctx);
-    container->table = make_table_u64_u64(models->tctx->allocator, 20);
+    container->node_arena = reserve_arena(tctx);
+    container->table = make_table_u64_u64(tctx->allocator, 20);
 }
 
 internal Text_Layout*
@@ -29,8 +29,8 @@ text_layout_new__alloc_layout(Text_Layout_Container *container){
 }
 
 internal void
-text_layout_release(Models *models, Text_Layout_Container *container, Text_Layout *layout){
-    release_arena(models->tctx, layout->arena);
+text_layout_release(Thread_Context *tctx, Models *models, Text_Layout_Container *container, Text_Layout *layout){
+    release_arena(tctx, layout->arena);
     sll_stack_push(container->free_nodes, layout);
 }
 
@@ -65,14 +65,14 @@ text_layout_get(Text_Layout_Container *container, Text_Layout_ID id){
 }
 
 internal b32
-text_layout_erase(Models *models, Text_Layout_Container *container, Text_Layout_ID id){
+text_layout_erase(Thread_Context *tctx, Models *models, Text_Layout_Container *container, Text_Layout_ID id){
     b32 result = false;
     Table_Lookup lookup = table_lookup(&container->table, id);
     if (lookup.found_match){
         u64 ptr_val = 0;
         table_read(&container->table, lookup, &ptr_val);
         Text_Layout *ptr = (Text_Layout*)IntAsPtr(ptr_val);
-        text_layout_release(models, container, ptr);
+        text_layout_release(tctx, models, container, ptr);
         table_erase(&container->table, lookup);
         result = true;
     }
@@ -82,7 +82,7 @@ text_layout_erase(Models *models, Text_Layout_Container *container, Text_Layout_
 ////////////////////////////////
 
 internal void
-text_layout_render(Models *models, Text_Layout *layout){
+text_layout_render(Thread_Context *tctx, Models *models, Text_Layout *layout){
     Editing_File *file = imp_get_file(models, layout->buffer_id);
     if (file != 0){
         Render_Target *target = models->target;
@@ -98,7 +98,7 @@ text_layout_render(Models *models, Text_Layout *layout){
         i64 line_number = layout->visible_line_number_range.min;
         i64 line_number_last = layout->visible_line_number_range.max;
         for (;line_number <= line_number_last; line_number += 1){
-            Buffer_Layout_Item_List line = file_get_line_layout(models, file, width, face, line_number);
+            Buffer_Layout_Item_List line = file_get_line_layout(tctx, models, file, width, face, line_number);
             for (Buffer_Layout_Item_Block *block = line.first;
                  block != 0;
                  block = block->next){
diff --git a/4ed_view.cpp b/4ed_view.cpp
index abfe0973..c3a98040 100644
--- a/4ed_view.cpp
+++ b/4ed_view.cpp
@@ -148,12 +148,15 @@ view_set_edit_pos(View *view, File_Edit_Positions edit_pos){
 ////////////////////////////////
 
 internal Rect_f32
-view_get_buffer_rect(Models *models, View *view){
+view_get_buffer_rect(Thread_Context *tctx, Models *models, View *view){
     Rect_f32 region = Rf32(view->panel->rect_full);
     if (models->buffer_region != 0){
         Rect_f32 rect = region;
         Rect_f32 sub_region = Rf32(V2(0, 0), rect_dim(rect));
-        sub_region = models->buffer_region(&models->app_links, view_get_id(&models->live_set, view), sub_region);
+        Application_Links app = {};
+        app.tctx = tctx;
+        app.cmd_context = models;
+        sub_region = models->buffer_region(&app, view_get_id(&models->live_set, view), sub_region);
         region.p0 = rect.p0 + sub_region.p0;
         region.p1 = rect.p0 + sub_region.p1;
         region.x1 = clamp_top(region.x1, rect.x1);
@@ -165,112 +168,112 @@ view_get_buffer_rect(Models *models, View *view){
 }
 
 internal f32
-view_width(Models *models, View *view){
-    return(rect_width(view_get_buffer_rect(models, view)));
+view_width(Thread_Context *tctx, Models *models, View *view){
+    return(rect_width(view_get_buffer_rect(tctx, models, view)));
 }
 
 internal f32
-view_height(Models *models, View *view){
-    return(rect_height(view_get_buffer_rect(models, view)));
+view_height(Thread_Context *tctx, Models *models, View *view){
+    return(rect_height(view_get_buffer_rect(tctx, models, view)));
 }
 
 ////////////////////////////////
 
 internal Buffer_Layout_Item_List
-view_get_line_layout(Models *models, View *view, i64 line_number){
+view_get_line_layout(Thread_Context *tctx, Models *models, View *view, i64 line_number){
     Editing_File *file = view->file;
     Face *face = file_get_face(models, file);
-    f32 width = view_width(models, view);
-    return(file_get_line_layout(models, file, width, face, line_number));
+    f32 width = view_width(tctx, models, view);
+    return(file_get_line_layout(tctx, models, file, width, face, line_number));
 }
 
 internal Line_Shift_Vertical
-view_line_shift_y(Models *models, View *view, i64 line_number, f32 y_delta){
+view_line_shift_y(Thread_Context *tctx, Models *models, View *view, i64 line_number, f32 y_delta){
     Editing_File *file = view->file;
     Face *face = file_get_face(models, file);
-    f32 width = view_width(models, view);
-    return(file_line_shift_y(models, file, width, face, line_number, y_delta));
+    f32 width = view_width(tctx, models, view);
+    return(file_line_shift_y(tctx, models, file, width, face, line_number, y_delta));
 }
 
 internal f32
-view_line_y_difference(Models *models, View *view, i64 line_a, i64 line_b){
+view_line_y_difference(Thread_Context *tctx, Models *models, View *view, i64 line_a, i64 line_b){
     Editing_File *file = view->file;
     Face *face = file_get_face(models, file);
-    f32 width = view_width(models, view);
-    return(file_line_y_difference(models, file, width, face, line_a, line_b));
+    f32 width = view_width(tctx, models, view);
+    return(file_line_y_difference(tctx, models, file, width, face, line_a, line_b));
 }
 
 internal i64
-view_pos_at_relative_xy(Models *models, View *view, i64 base_line, Vec2_f32 relative_xy){
+view_pos_at_relative_xy(Thread_Context *tctx, Models *models, View *view, i64 base_line, Vec2_f32 relative_xy){
     Editing_File *file = view->file;
     Face *face = file_get_face(models, file);
-    f32 width = view_width(models, view);
-    return(file_pos_at_relative_xy(models, file, width, face, base_line, relative_xy));
+    f32 width = view_width(tctx, models, view);
+    return(file_pos_at_relative_xy(tctx, models, file, width, face, base_line, relative_xy));
 }
 
 internal Vec2_f32
-view_relative_xy_of_pos(Models *models, View *view, i64 base_line, i64 pos){
+view_relative_xy_of_pos(Thread_Context *tctx, Models *models, View *view, i64 base_line, i64 pos){
     Editing_File *file = view->file;
     Face *face = file_get_face(models, file);
-    f32 width = view_width(models, view);
-    return(file_relative_xy_of_pos(models, file, width, face, base_line, pos));
+    f32 width = view_width(tctx, models, view);
+    return(file_relative_xy_of_pos(tctx, models, file, width, face, base_line, pos));
 }
 
 internal Buffer_Point
-view_normalize_buffer_point(Models *models, View *view, Buffer_Point point){
+view_normalize_buffer_point(Thread_Context *tctx, Models *models, View *view, Buffer_Point point){
     Editing_File *file = view->file;
     Face *face = file_get_face(models, file);
-    f32 width = view_width(models, view);
-    return(file_normalize_buffer_point(models, file, width, face, point));
+    f32 width = view_width(tctx, models, view);
+    return(file_normalize_buffer_point(tctx, models, file, width, face, point));
 }
 
 internal Vec2_f32
-view_buffer_point_difference(Models *models, View *view, Buffer_Point a, Buffer_Point b){
+view_buffer_point_difference(Thread_Context *tctx, Models *models, View *view, Buffer_Point a, Buffer_Point b){
     Editing_File *file = view->file;
     Face *face = file_get_face(models, file);
-    f32 width = view_width(models, view);
-    return(file_buffer_point_difference(models, file, width, face, a, b));
+    f32 width = view_width(tctx, models, view);
+    return(file_buffer_point_difference(tctx, models, file, width, face, a, b));
 }
 
 internal Buffer_Point
-view_move_buffer_point(Models *models, View *view, Buffer_Point buffer_point, Vec2_f32 delta){
+view_move_buffer_point(Thread_Context *tctx, Models *models, View *view, Buffer_Point buffer_point, Vec2_f32 delta){
     delta += buffer_point.pixel_shift;
-    Line_Shift_Vertical shift = view_line_shift_y(models, view, buffer_point.line_number, delta.y);
+    Line_Shift_Vertical shift = view_line_shift_y(tctx, models, view, buffer_point.line_number, delta.y);
     buffer_point.line_number = shift.line;
     buffer_point.pixel_shift = V2f32(delta.x, delta.y - shift.y_delta);
     return(buffer_point);
 }
 
 internal Line_Shift_Character
-view_line_shift_characters(Models *models, View *view, i64 line_number, i64 character_delta){
+view_line_shift_characters(Thread_Context *tctx, Models *models, View *view, i64 line_number, i64 character_delta){
     Editing_File *file = view->file;
     Face *face = file_get_face(models, file);
-    f32 width = view_width(models, view);
-    return(file_line_shift_characters(models, file, width, face, line_number, character_delta));
+    f32 width = view_width(tctx, models, view);
+    return(file_line_shift_characters(tctx, models, file, width, face, line_number, character_delta));
 }
 
 internal i64
-view_line_character_difference(Models *models, View *view, i64 line_a, i64 line_b){
+view_line_character_difference(Thread_Context *tctx, Models *models, View *view, i64 line_a, i64 line_b){
     Editing_File *file = view->file;
     Face *face = file_get_face(models, file);
-    f32 width = view_width(models, view);
-    return(file_line_character_difference(models, file, width, face, line_a, line_b));
+    f32 width = view_width(tctx, models, view);
+    return(file_line_character_difference(tctx, models, file, width, face, line_a, line_b));
 }
 
 internal i64
-view_pos_from_relative_character(Models *models, View *view, i64 base_line, i64 relative_character){
+view_pos_from_relative_character(Thread_Context *tctx, Models *models, View *view, i64 base_line, i64 relative_character){
     Editing_File *file = view->file;
     Face *face = file_get_face(models, file);
-    f32 width = view_width(models, view);
-    return(file_pos_from_relative_character(models, file, width, face, base_line, relative_character));
+    f32 width = view_width(tctx, models, view);
+    return(file_pos_from_relative_character(tctx, models, file, width, face, base_line, relative_character));
 }
 
 internal i64
-view_relative_character_from_pos(Models *models, View *view, i64 base_line, i64 pos){
+view_relative_character_from_pos(Thread_Context *tctx, Models *models, View *view, i64 base_line, i64 pos){
     Editing_File *file = view->file;
     Face *face = file_get_face(models, file);
-    f32 width = view_width(models, view);
-    return(file_relative_character_from_pos(models, file, width, face, base_line, pos));
+    f32 width = view_width(tctx, models, view);
+    return(file_relative_character_from_pos(tctx, models, file, width, face, base_line, pos));
 }
 
 internal Buffer_Cursor
@@ -282,14 +285,14 @@ view_compute_cursor(View *view, Buffer_Seek seek){
 ////////////////////////////////
 
 internal b32
-view_move_view_to_cursor(Models *models, View *view, Buffer_Scroll *scroll){
+view_move_view_to_cursor(Thread_Context *tctx, Models *models, View *view, Buffer_Scroll *scroll){
     Editing_File *file = view->file;
     Face *face = file_get_face(models, file);
-    Rect_f32 rect = view_get_buffer_rect(models, view);
+    Rect_f32 rect = view_get_buffer_rect(tctx, models, view);
     Vec2_f32 view_dim = rect_dim(rect);
     
     File_Edit_Positions edit_pos = view_get_edit_pos(view);
-    Vec2_f32 p = file_relative_xy_of_pos(models, file, view_dim.x, face, scroll->target.line_number, 
+    Vec2_f32 p = file_relative_xy_of_pos(tctx, models, file, view_dim.x, face, scroll->target.line_number, 
                                          edit_pos.cursor_pos);
     p -= scroll->target.pixel_shift;
     
@@ -310,7 +313,7 @@ view_move_view_to_cursor(Models *models, View *view, Buffer_Scroll *scroll){
         target_p_relative.x = (p.x + typical_advance*1.5f) - view_dim.x;
     }
     scroll->target.pixel_shift += target_p_relative;
-    scroll->target = view_normalize_buffer_point(models, view, scroll->target);
+    scroll->target = view_normalize_buffer_point(tctx, models, view, scroll->target);
     scroll->target.pixel_shift.x = f32_round32(scroll->target.pixel_shift.x);
     scroll->target.pixel_shift.y = f32_round32(scroll->target.pixel_shift.y);
     
@@ -318,13 +321,13 @@ view_move_view_to_cursor(Models *models, View *view, Buffer_Scroll *scroll){
 }
 
 internal b32
-view_move_cursor_to_view(Models *models, View *view, Buffer_Scroll scroll, i64 *pos_in_out, f32 preferred_x){
+view_move_cursor_to_view(Thread_Context *tctx, Models *models, View *view, Buffer_Scroll scroll, i64 *pos_in_out, f32 preferred_x){
     Editing_File *file = view->file;
     Face *face = file_get_face(models, file);
-    Rect_f32 rect = view_get_buffer_rect(models, view);
+    Rect_f32 rect = view_get_buffer_rect(tctx, models, view);
     Vec2_f32 view_dim = rect_dim(rect);
     
-    Vec2_f32 p = file_relative_xy_of_pos(models, file, view_dim.x, face, scroll.target.line_number, *pos_in_out);
+    Vec2_f32 p = file_relative_xy_of_pos(tctx, models, file, view_dim.x, face, scroll.target.line_number, *pos_in_out);
     p -= scroll.target.pixel_shift;
     
     f32 line_height = face->line_height;
@@ -343,7 +346,7 @@ view_move_cursor_to_view(Models *models, View *view, Buffer_Scroll scroll, i64 *
     b32 result = false;
     if (adjusted_y){
         p += scroll.target.pixel_shift;
-        *pos_in_out = file_pos_at_relative_xy(models, file, view_dim.x, face, scroll.target.line_number, p);
+        *pos_in_out = file_pos_at_relative_xy(tctx, models, file, view_dim.x, face, scroll.target.line_number, p);
         result = true;
     }
     
@@ -351,33 +354,33 @@ view_move_cursor_to_view(Models *models, View *view, Buffer_Scroll scroll, i64 *
 }
 
 internal void
-view_set_cursor(Models *models, View *view, i64 pos){
+view_set_cursor(Thread_Context *tctx, Models *models, View *view, i64 pos){
     File_Edit_Positions edit_pos = view_get_edit_pos(view);
     file_edit_positions_set_cursor(&edit_pos, pos);
     view_set_edit_pos(view, edit_pos);
     Buffer_Scroll scroll = edit_pos.scroll;
-    if (view_move_view_to_cursor(models, view, &scroll)){
+    if (view_move_view_to_cursor(tctx, models, view, &scroll)){
         edit_pos.scroll = scroll;
         view_set_edit_pos(view, edit_pos);
     }
 }
 
 internal void
-view_set_scroll(Models *models, View *view, Buffer_Scroll scroll){
+view_set_scroll(Thread_Context *tctx, Models *models, View *view, Buffer_Scroll scroll){
     File_Edit_Positions edit_pos = view_get_edit_pos(view);
     file_edit_positions_set_scroll(&edit_pos, scroll);
     view_set_edit_pos(view, edit_pos);
-    if (view_move_cursor_to_view(models, view, edit_pos.scroll, &edit_pos.cursor_pos, view->preferred_x)){
+    if (view_move_cursor_to_view(tctx, models, view, edit_pos.scroll, &edit_pos.cursor_pos, view->preferred_x)){
         view_set_edit_pos(view, edit_pos);
     }
 }
 
 internal void
-view_set_cursor_and_scroll(Models *models, View *view, i64 pos, Buffer_Scroll scroll){
+view_set_cursor_and_scroll(Thread_Context *tctx, Models *models, View *view, i64 pos, Buffer_Scroll scroll){
     File_Edit_Positions edit_pos = view_get_edit_pos(view);
     file_edit_positions_set_cursor(&edit_pos, pos);
     Buffer_Cursor cursor = view_compute_cursor(view, seek_pos(pos));
-    Vec2_f32 p = view_relative_xy_of_pos(models, view, cursor.line, pos);
+    Vec2_f32 p = view_relative_xy_of_pos(tctx, models, view, cursor.line, pos);
     view->preferred_x = p.x;
     file_edit_positions_set_scroll(&edit_pos, scroll);
     edit_pos.last_set_type = EditPos_None;
@@ -397,7 +400,7 @@ view_post_paste_effect(View *view, f32 seconds, i64 start, i64 size, u32 color){
 ////////////////////////////////
 
 internal void
-view_set_file(Models *models, View *view, Editing_File *file){
+view_set_file(Thread_Context *tctx, Models *models, View *view, Editing_File *file){
     Assert(file != 0);
     
     Editing_File *old_file = view->file;
@@ -412,7 +415,7 @@ view_set_file(Models *models, View *view, Editing_File *file){
     view_set_edit_pos(view, edit_pos);
     view->mark = edit_pos.cursor_pos;
     Buffer_Cursor cursor = view_compute_cursor(view, seek_pos(edit_pos.cursor_pos));
-    Vec2_f32 p = view_relative_xy_of_pos(models, view, cursor.line, edit_pos.cursor_pos);
+    Vec2_f32 p = view_relative_xy_of_pos(tctx, models, view, cursor.line, edit_pos.cursor_pos);
     view->preferred_x = p.x;
     
     models->layout.panel_state_dirty = true;
@@ -463,20 +466,6 @@ view_current_context(View *view){
 
 ////////////////////////////////
 
-internal App_Coroutine_State
-get_co_state(Application_Links *app){
-    App_Coroutine_State state = {};
-    state.co = app->current_coroutine;
-    state.type = app->type_coroutine;
-    return(state);
-}
-
-internal void
-restore_co_state(Application_Links *app, App_Coroutine_State state){
-    app->current_coroutine = state.co;
-    app->type_coroutine = state.type;
-}
-
 internal Coroutine*
 co_handle_request(Models *models, Coroutine *co, Co_Out *out){
     Coroutine *result = 0;
@@ -503,17 +492,11 @@ co_handle_request(Models *models, Coroutine *co, Co_Out *out){
 }
 
 internal Coroutine*
-co_run(Models *models, App_Coroutine_Purpose purpose, Coroutine *co,
-       Co_In *in, Co_Out *out){
-    Application_Links *app = &models->app_links;
-    App_Coroutine_State prev_state = get_co_state(app);
-    app->current_coroutine = co;
-    app->type_coroutine = purpose;
+co_run(Thread_Context *tctx, Models *models, Coroutine *co, Co_In *in, Co_Out *out){
     Coroutine *result = coroutine_run(&models->coroutines, co, in, out);
     for (;result != 0 && out->request != CoRequest_None;){
         result = co_handle_request(models, result, out);
     }
-    restore_co_state(app, prev_state);
     return(result);
 }
 
@@ -523,15 +506,18 @@ view_event_context_base__inner(Coroutine *coroutine){
     Models *models = in->models;
     Custom_Command_Function *event_context_base = in->event_context_base;
     Assert(event_context_base != 0);
-    event_context_base(&models->app_links);
+    Application_Links app = {};
+    app.tctx = coroutine->tctx;
+    app.cmd_context = models;
+    event_context_base(&app);
 }
 
 function void
-view_init(Models *models, View *view, Editing_File *initial_buffer,
+view_init(Thread_Context *tctx, Models *models, View *view, Editing_File *initial_buffer,
           Custom_Command_Function *event_context_base){
-    view_set_file(models, view, initial_buffer);
+    view_set_file(tctx, models, view, initial_buffer);
     
-    view->node_arena = reserve_arena(models->tctx);
+    view->node_arena = reserve_arena(tctx);
     
     View_Context first_ctx = {};
     first_ctx.render_caller = models->render_caller;
@@ -543,7 +529,7 @@ view_init(Models *models, View *view, Editing_File *initial_buffer,
     Co_In in = {};
     in.models = models;
     in.event_context_base = event_context_base;
-    view->co = co_run(models, Co_View, view->co, &in, &view->co_out);
+    view->co = co_run(tctx, models, view->co, &in, &view->co_out);
     // TODO(allen): deal with this kind of problem!
     Assert(view->co != 0);
 }
@@ -572,25 +558,28 @@ view_check_co_exited(Models *models, View *view){
 }
 
 internal void
-co_single_abort(Models *models, View *view){
+co_single_abort(Thread_Context *tctx, Models *models, View *view){
     Coroutine *co = view->co;
     Co_In in = {};
     in.user_input.abort = true;
-    view->co = co_run(models, Co_View, co, &in, &view->co_out);
+    view->co = co_run(tctx, models, co, &in, &view->co_out);
     view_check_co_exited(models, view);
 }
 
 internal void
-co_full_abort(Models *models, View *view){
+co_full_abort(Thread_Context *tctx, Models *models, View *view){
     Coroutine *co = view->co;
     Co_In in = {};
     in.user_input.abort = true;
     for (u32 j = 0; j < 100 && co != 0; ++j){
-        co  = co_run(models, Co_View, co, &in, &view->co_out);
+        co  = co_run(tctx, models, co, &in, &view->co_out);
     }
     if (co != 0){
 #define M "SERIOUS ERROR: full stack abort did not complete"
-        print_message(&models->app_links, string_u8_litexpr(M));
+        Application_Links app = {};
+        app.tctx = tctx;
+        app.cmd_context = models;
+        print_message(&app, string_u8_litexpr(M));
 #undef M
     }
     view->co = 0;
@@ -598,7 +587,7 @@ co_full_abort(Models *models, View *view){
 }
 
 function b32
-co_send_event(Models *models, View *view, Input_Event *event){
+co_send_event(Thread_Context *tctx, Models *models, View *view, Input_Event *event){
     b32 event_was_handled = false;
     
     Coroutine *co = view->co;
@@ -613,7 +602,7 @@ co_send_event(Models *models, View *view, Input_Event *event){
         in.user_input.event = *event;
         in.user_input.abort = ((abort_flags & event_flags) != 0);
         begin_handling_input(models, &in.user_input);
-        view->co = co_run(models, Co_View, view->co, &in, &view->co_out);
+        view->co = co_run(tctx, models, view->co, &in, &view->co_out);
         view_check_co_exited(models, view);
         if (!HasFlag(event_flags, EventProperty_Animate)){
             models->animate_next_frame = true;
@@ -625,52 +614,52 @@ co_send_event(Models *models, View *view, Input_Event *event){
 }
 
 function b32
-co_send_core_event(Models *models, View *view, Core_Code code, String_Const_u8 string){
+co_send_core_event(Thread_Context *tctx, Models *models, View *view, Core_Code code, String_Const_u8 string){
     Input_Event event = {};
     event.kind = InputEventKind_Core;
     event.core.code = code;
     event.core.string = string;
-    return(co_send_event(models, view, &event));
+    return(co_send_event(tctx, models, view, &event));
 }
 
 function b32
-co_send_core_event(Models *models, View *view, Core_Code code, Buffer_ID id){
+co_send_core_event(Thread_Context *tctx, Models *models, View *view, Core_Code code, Buffer_ID id){
     Input_Event event = {};
     event.kind = InputEventKind_Core;
     event.core.code = code;
     event.core.id = id;
-    return(co_send_event(models, view, &event));
+    return(co_send_event(tctx, models, view, &event));
 }
 
 function b32
-co_send_core_event(Models *models, View *view, Core_Code code){
-    return(co_send_core_event(models, view, code, SCu8()));
+co_send_core_event(Thread_Context *tctx, Models *models, View *view, Core_Code code){
+    return(co_send_core_event(tctx, models, view, code, SCu8()));
 }
 
 function b32
-co_send_event(Models *models, Input_Event *event){
+co_send_event(Thread_Context *tctx, Models *models, Input_Event *event){
     Panel *active_panel = models->layout.active_panel;
     View *view = active_panel->view;
-    return(co_send_event(models, view, event));
+    return(co_send_event(tctx, models, view, event));
 }
 
 function b32
-co_send_core_event(Models *models, Core_Code code, String_Const_u8 string){
+co_send_core_event(Thread_Context *tctx, Models *models, Core_Code code, String_Const_u8 string){
     Panel *active_panel = models->layout.active_panel;
     View *view = active_panel->view;
-    return(co_send_core_event(models, view, code, string));
+    return(co_send_core_event(tctx, models, view, code, string));
 }
 
 function b32
-co_send_core_event(Models *models, Core_Code code, Buffer_ID buffer_id){
+co_send_core_event(Thread_Context *tctx, Models *models, Core_Code code, Buffer_ID buffer_id){
     Panel *active_panel = models->layout.active_panel;
     View *view = active_panel->view;
-    return(co_send_core_event(models, view, code, buffer_id));
+    return(co_send_core_event(tctx, models, view, code, buffer_id));
 }
 
 function b32
-co_send_core_event(Models *models, Core_Code code){
-    return(co_send_core_event(models, code, SCu8()));
+co_send_core_event(Thread_Context *tctx, Models *models, Core_Code code){
+    return(co_send_core_event(tctx, models, code, SCu8()));
 }
 
 ////////////////////////////////
@@ -691,7 +680,7 @@ file_is_viewed(Layout *layout, Editing_File *file){
 }
 
 internal void
-adjust_views_looking_at_file_to_new_cursor(Models *models, Editing_File *file){
+adjust_views_looking_at_file_to_new_cursor(Thread_Context *tctx, Models *models, Editing_File *file){
     Layout *layout = &models->layout;
     for (Panel *panel = layout_get_first_open_panel(layout);
          panel != 0;
@@ -699,7 +688,7 @@ adjust_views_looking_at_file_to_new_cursor(Models *models, Editing_File *file){
         View *view = panel->view;
         if (view->file == file){
             File_Edit_Positions edit_pos = view_get_edit_pos(view);
-            view_set_cursor(models, view, edit_pos.cursor_pos);
+            view_set_cursor(tctx, models, view, edit_pos.cursor_pos);
         }
     }
 }
diff --git a/4ed_working_set.cpp b/4ed_working_set.cpp
index ed9ed573..cb5adcfd 100644
--- a/4ed_working_set.cpp
+++ b/4ed_working_set.cpp
@@ -381,7 +381,7 @@ buffer_unbind_name_low_level(Working_Set *working_set, Editing_File *file){
 }
 
 internal void
-buffer_bind_name(Models *models, Arena *scratch, Working_Set *working_set, Editing_File *file, String_Const_u8 base_name){
+buffer_bind_name(Thread_Context *tctx, Models *models, Arena *scratch, Working_Set *working_set, Editing_File *file, String_Const_u8 base_name){
     Temp_Memory temp = begin_temp(scratch);
     
     // List of conflict files.
@@ -445,7 +445,10 @@ buffer_bind_name(Models *models, Arena *scratch, Working_Set *working_set, Editi
     
     // Get user's resolution data.
     if (models->buffer_name_resolver != 0){
-        models->buffer_name_resolver(&models->app_links, conflicts, conflict_count);
+        Application_Links app = {};
+        app.tctx = tctx;
+        app.cmd_context = models;
+        models->buffer_name_resolver(&app, conflicts, conflict_count);
     }
     
     // Re-bind all of the files
diff --git a/custom/4coder_async_tasks.cpp b/custom/4coder_async_tasks.cpp
index 9ae53ece..b4f88b09 100644
--- a/custom/4coder_async_tasks.cpp
+++ b/custom/4coder_async_tasks.cpp
@@ -4,19 +4,126 @@
 
 // TOP
 
-Application_Links *dummy_async_app = 0;
+global Async_System async_system = {};
+
+function Async_Node*
+async_pop_node(void){
+    system_mutex_acquire(async_system.mutex);
+    for (;async_system.task_count == 0;){
+        system_condition_variable_wait(async_system.cv, async_system.mutex);
+    }
+    Async_Node *node = async_system.task_first;
+    sll_queue_pop(async_system.task_first, async_system.task_last);
+    async_system.task_count -= 1;
+    system_mutex_release(async_system.mutex);
+    node->next = 0;
+    return(node);
+}
+
+function Async_Task
+async_push_node(Async_Task_Function_Type *func, Data data){
+    Async_Task result = async_system.task_id_counter;
+    async_system.task_id_counter += 1;
+    
+    system_mutex_acquire(async_system.mutex);
+    Async_Node *node = async_system.free_nodes;
+    if (node == 0){
+        node = push_array(&async_system.node_arena, Async_Node, 1);
+    }
+    else{
+        sll_stack_pop(async_system.free_nodes);
+    }
+    node->task = result;
+    node->thread = 0;
+    node->func = func;
+    node->data.data = (u8*)heap_allocate(&async_system.node_heap, data.size);
+    block_copy(node->data.data, data.data, data.size);
+    node->data.size = data.size;
+    sll_queue_push(async_system.task_first, async_system.task_last, node);
+    async_system.task_count += 1;
+    system_condition_variable_signal(async_system.cv);
+    system_mutex_release(async_system.mutex);
+    
+    return(result);
+}
+
+function void
+async_free_node(Async_Node *node){
+    system_mutex_acquire(async_system.mutex);
+    heap_free(&async_system.node_heap, node->data.data);
+    sll_stack_push(async_system.free_nodes, node);
+    system_mutex_release(async_system.mutex);
+}
+
+function void
+async_task_thread(void *thread_ptr){
+    Base_Allocator *allocator = get_base_allocator_system();
+    
+    Thread_Context_Extra_Info tctx_info = {};
+    tctx_info.async_thread = thread_ptr;
+    
+    Thread_Context tctx_ = {};
+    Thread_Context *tctx = &tctx_;
+    thread_ctx_init(tctx, ThreadKind_AsyncTasks, allocator, allocator);
+    
+    Async_Thread *thread = (Async_Thread*)thread_ptr;
+    
+    Application_Links app = {};
+    app.tctx = tctx;
+    app.cmd_context = async_system.cmd_context;
+    Async_Context ctx = {&app, thread};
+    
+    for (;;){
+        Async_Node *node = async_pop_node();
+        node->thread = thread;
+        thread->node = node;
+        thread->task = node->task;
+        node->func(&ctx, node->data);
+        thread->node = 0;
+        thread->task = 0;
+        async_free_node(node);
+    }
+}
+
+function Async_Node*
+async_get_pending_node(Async_Task task){
+    Async_Node *result = 0;
+    for (Async_Node *node = async_system.task_first;
+         node != 0;
+         node = node->next){
+        if (node->task == task){
+            result = node;
+            break;
+        }
+    }
+    return(result);
+}
+
+function Async_Node*
+async_get_running_node(Async_Task task){
+    Async_Node *result = 0;
+    if (async_system.thread.task == task){
+        
+    }
+    return(result);
+}
+
+////////////////////////////////
 
 function void
 async_task_handler_init(Application_Links *app){
-    //NotImplemented;
-    dummy_async_app = app;
+    block_zero_struct(&async_system);
+    async_system.cmd_context = app->cmd_context;
+    async_system.node_arena = make_arena_system(KB(4));
+    heap_init(&async_system.node_heap, &async_system.node_arena);
+    async_system.mutex = system_mutex_make();
+    async_system.cv = system_condition_variable_make();
+    async_system.thread.thread = system_thread_launch(async_task_thread, &async_system.thread);
 }
 
 function Async_Task
 async_task_no_dep(Async_Task_Function_Type *func, Data data){
-    //NotImplemented;
-    func(dummy_async_app, data);
-    return(0);
+    return(async_push_node(func, data));
 }
 
 function Async_Task
@@ -26,22 +133,36 @@ async_task_single_dep(Async_Task_Function_Type *func, Data data, Async_Task depe
 
 function b32
 async_task_is_pending(Async_Task task){
-    NotImplemented;
+    system_mutex_acquire(async_system.mutex);
+    Async_Node *node = async_get_pending_node(task);
+    system_mutex_release(async_system.mutex);
+    return(node != 0);
 }
 
 function b32
 async_task_is_running(Async_Task task){
-    NotImplemented;
+    system_mutex_acquire(async_system.mutex);
+    Async_Node *node = async_get_running_node(task);
+    system_mutex_release(async_system.mutex);
+    return(node != 0);
 }
 
 function b32
 async_task_is_running_or_pending(Async_Task task){
-    NotImplemented;
+    system_mutex_acquire(async_system.mutex);
+    Async_Node *node = async_get_pending_node(task);
+    if (node != 0){
+        node = async_get_running_node(task);
+    }
+    system_mutex_release(async_system.mutex);
+    return(node != 0);
 }
 
 function void
 async_task_cancel(Async_Task task){
+    system_mutex_acquire(async_system.mutex);
     NotImplemented;
+    system_mutex_release(async_system.mutex);
 }
 
 function void
diff --git a/custom/4coder_async_tasks.h b/custom/4coder_async_tasks.h
index 8dae24f8..ab1d4ac9 100644
--- a/custom/4coder_async_tasks.h
+++ b/custom/4coder_async_tasks.h
@@ -7,10 +7,44 @@
 #if !defined(FCODER_ASYNC_TASKS_H)
 #define FCODER_ASYNC_TASKS_H
 
-typedef void Async_Task_Function_Type(Application_Links *app, Data data);
-
+typedef void Async_Task_Function_Type(struct Async_Context *actx, Data data);
 typedef u64 Async_Task;
 
+struct Async_Thread{
+    System_Thread thread;
+    struct Async_Node *node;
+    Async_Task task;
+};
+
+struct Async_Node{
+    Async_Node *next;
+    Async_Task task;
+    Async_Thread *thread;
+    Async_Task_Function_Type *func;
+    Data data;
+};
+
+struct Async_System{
+    void *cmd_context;
+    
+    Heap node_heap;
+    Arena node_arena;
+    System_Mutex mutex;
+    System_Condition_Variable cv;
+    Async_Task task_id_counter;
+    Async_Node *free_nodes;
+    Async_Node *task_first;
+    Async_Node *task_last;
+    i32 task_count;
+    
+    Async_Thread thread;
+};
+
+struct Async_Context{
+    Application_Links *app;
+    Async_Thread *thread;
+};
+
 #endif
 
 // BOTTOM
diff --git a/custom/4coder_base_types.h b/custom/4coder_base_types.h
index 6b3ae3af..4e5f83a0 100644
--- a/custom/4coder_base_types.h
+++ b/custom/4coder_base_types.h
@@ -478,7 +478,7 @@ union SNode{
 #define sll_stack_pop_(h) h=h=h->next
 #define sll_queue_push_multiple_(f,l,ff,ll) if(ll){if(f){l->next=ff;}else{f=ff;}l=ll;l->next=0;}
 #define sll_queue_push_(f,l,n) sll_queue_push_multiple_(f,l,n,n)
-#define sll_queue_pop_(f,l) if (f==l) { f=l=0; } else { f->next=0;f=f->next; }
+#define sll_queue_pop_(f,l) if (f==l) { f=l=0; } else { f=f->next; }
 
 #define sll_stack_push(h,n) (sll_stack_push_((h),(n)))
 #define sll_stack_pop(h) (sll_stack_pop_((h)))
@@ -1188,6 +1188,8 @@ struct Thread_Context{
     Profile_Record *prof_first;
     Profile_Record *prof_last;
     i32 prof_record_count;
+    
+    void *user_data;
 };
 
 typedef i32 Scratch_Share_Code;
diff --git a/custom/4coder_default_hooks.cpp b/custom/4coder_default_hooks.cpp
index bc883130..8ba19564 100644
--- a/custom/4coder_default_hooks.cpp
+++ b/custom/4coder_default_hooks.cpp
@@ -539,7 +539,8 @@ BUFFER_NAME_RESOLVER_SIG(default_buffer_name_resolution){
 }
 
 function void
-do_full_lex_async__inner(Application_Links *app, Buffer_ID buffer_id){
+do_full_lex_async__inner(Async_Context *actx, Buffer_ID buffer_id){
+    Application_Links *app = actx->app;
     Thread_Context *tctx = get_thread_context(app);
     Scratch_Block scratch(tctx);
     
@@ -564,10 +565,10 @@ do_full_lex_async__inner(Application_Links *app, Buffer_ID buffer_id){
 }
 
 function void
-do_full_lex_async(Application_Links *app, Data data){
+do_full_lex_async(Async_Context *actx, Data data){
     if (data.size == sizeof(Buffer_ID)){
         Buffer_ID buffer = *(Buffer_ID*)data.data;
-        do_full_lex_async__inner(app, buffer);
+        do_full_lex_async__inner(actx, buffer);
     }
 }
 
diff --git a/custom/4coder_types.h b/custom/4coder_types.h
index 07403dae..a063dd4e 100644
--- a/custom/4coder_types.h
+++ b/custom/4coder_types.h
@@ -13,11 +13,13 @@
 
 #endif
 
+struct Thread_Context_Extra_Info{
+    void *coroutine;
+    void *async_thread;
+};
 struct Application_Links{
+    Thread_Context *tctx;
     void *cmd_context;
-    void *current_thread;
-    void *current_coroutine;
-    i32 type_coroutine;
 };
 typedef void Custom_Layer_Init_Type(Application_Links *app);
 void custom_layer_init(Application_Links *app);
diff --git a/platform_win32/win32_4ed.cpp b/platform_win32/win32_4ed.cpp
index 803ecf07..933185d8 100644
--- a/platform_win32/win32_4ed.cpp
+++ b/platform_win32/win32_4ed.cpp
@@ -1681,7 +1681,7 @@ WinMain(HINSTANCE hInstance, HINSTANCE hPrevInstance, LPSTR lpCmdLine, int nCmdS
         Scratch_Block scratch(win32vars.tctx, Scratch_Share);
         String_Const_u8 curdir = system_get_path(scratch, SystemPath_CurrentDirectory);
         curdir = string_mod_replace_character(curdir, '\\', '/');
-        app.init(&target, base_ptr, win32vars.clipboard_contents, curdir, custom);
+        app.init(win32vars.tctx, &target, base_ptr, win32vars.clipboard_contents, curdir, custom);
     }
     
     //
@@ -1871,7 +1871,7 @@ WinMain(HINSTANCE hInstance, HINSTANCE hPrevInstance, LPSTR lpCmdLine, int nCmdS
         // NOTE(allen): Application Core Update
         Application_Step_Result result = {};
         if (app.step != 0){
-            result = app.step(&target, base_ptr, &input);
+            result = app.step(win32vars.tctx, &target, base_ptr, &input);
         }
         else{
             //LOG("app.step == 0 -- skipping\n");