diff --git a/client/src/game_state.cpp b/client/src/game_state.cpp
index 4d7b79f..52e8b73 100644
--- a/client/src/game_state.cpp
+++ b/client/src/game_state.cpp
@@ -13,7 +13,6 @@
 #include "game_state.h"
 #include "terminal.h"
 #include "ui/desktop.h"
-#include "ui/i_window_content.h"
 #include "ui/ui_window.h"
 #include "ui/editor.h"
 #include "ui/login_screen.h"
@@ -23,12 +22,13 @@
 #include "debug/debug_overlay.h"
 
 void GameState::_init_desktop(void) {
-  _desktop = std::make_unique<Desktop>(_screen_width, _screen_height, this); 
+  _desktop = std::make_unique<Desktop>(_screen_width, _screen_height, this, _initial_session_id);
 
   auto term = std::make_unique<Terminal>(this);
   term->set_session_id(_initial_session_id);
 
   auto term_window = std::make_unique<UIWindow>("Terminal", 100, 100, 800, 500);
+  term_window->set_session_id(_initial_session_id);
   UIWindow* window_ptr = term_window.get();
   term_window->set_content(std::move(term));
   _desktop->add_window(std::move(term_window));
@@ -229,6 +229,7 @@ void GameState::update(float dt, int draw_calls, int shape_verts, int text_verts
             if(new_term) {
               Terminal* term = dynamic_cast<Terminal*>(new_term->get_content());
               if(term) {
+                new_term->set_session_id(session_id);
                 term->set_session_id(session_id);
                 _desktop->register_session(session_id, new_term);
               }
@@ -242,6 +243,7 @@ void GameState::update(float dt, int draw_calls, int shape_verts, int text_verts
             editor->set_buffer_content(args[2]);
             auto editor_window = std::make_unique<UIWindow>(args[1].c_str(),
                                                             200, 200, 600, 400);
+            editor_window->set_session_id(session_id);
             editor_window->set_content(std::move(editor));
             _desktop->add_window(std::move(editor_window));
           }
diff --git a/client/src/ui/desktop.cpp b/client/src/ui/desktop.cpp
index 2e66ff0..19cd4a2 100644
--- a/client/src/ui/desktop.cpp
+++ b/client/src/ui/desktop.cpp
@@ -26,8 +26,10 @@ static const std::string& get_random_snippet(const std::vector<std::string>& sni
   return snippets[rand() % snippets.size()];
 }
 
-Desktop::Desktop(int screen_width, int screen_height, GameState* game_state) {
+Desktop::Desktop(int screen_width, int screen_height, GameState* game_state,
+                 uint32_t initial_session_id) {
   _taskbar = std::make_unique<Taskbar>(screen_width, screen_height);
+  _initial_session_id = initial_session_id;
   _game_state= game_state;
   _focused_window = nullptr;
   _window_awaiting_session_id = nullptr;
@@ -144,6 +146,7 @@ void Desktop::handle_event(SDL_Event* event, int screen_width, int screen_height
       } else if(app_to_launch == "Editor") {
         auto editor = std::make_unique<Editor>();
         auto editor_window = std::make_unique<UIWindow>("Editor", 200, 200, 600, 400);
+        editor_window->set_session_id(_initial_session_id);
         editor_window->set_content(std::move(editor));
         add_window(std::move(editor_window));
         _launcher_is_open = false;
@@ -183,10 +186,7 @@ void Desktop::update(float dt, int screen_width, int screen_height) {
     IWindowContent* content = _focused_window->get_content();
     if(content) {
       WindowAction action = content->get_pending_action();
-      uint32_t session_id = 0;
-      if(auto term = dynamic_cast<Terminal*>(content)) {
-        session_id = term->get_session_id();
-      }
+      uint32_t session_id = _focused_window->get_session_id();
       switch(action.type) {
         case ActionType::WRITE_FILE: {
           if(session_id != 0) {
diff --git a/client/src/ui/desktop.h b/client/src/ui/desktop.h
index fced735..c22370e 100644
--- a/client/src/ui/desktop.h
+++ b/client/src/ui/desktop.h
@@ -24,7 +24,8 @@ struct ScrollingText {
 
 class Desktop {
 public:
-  Desktop(int screen_width, int screen_height, GameState* game_state);
+  Desktop(int screen_width, int screen_height, GameState* game_state,
+          uint32_t initial_session_id);
   ~Desktop(void);
 
   void add_window(std::unique_ptr<UIWindow> window);
@@ -52,4 +53,5 @@ private:
   std::vector<ScrollingText>    _background_text;
   std::vector<std::string>      _snippets;
   bool                          _launcher_is_open;
+  uint32_t                      _initial_session_id;
 };
diff --git a/client/src/ui/ui_window.h b/client/src/ui/ui_window.h
index d2e3de7..ca06328 100644
--- a/client/src/ui/ui_window.h
+++ b/client/src/ui/ui_window.h
@@ -45,6 +45,8 @@ public:
   bool is_mouse_over_resize_handle(int mouse_x, int mouse_y) const;
   const std::string& get_title(void) const;
   Rect get_rect(void) const;
+  void set_session_id(uint32_t id) { _session_id = id; }
+  uint32_t get_session_id(void) const { return _session_id; }
 
 private:
   friend class Taskbar; /* Allow taskbar to access private members. */
@@ -64,4 +66,6 @@ private:
 
   bool _is_resizing;
   int _resize_margin;
+
+  uint32_t _session_id;
 };
diff --git a/common/src/lua_api.cpp b/common/src/lua_api.cpp
index 8fcaa48..b37e880 100644
--- a/common/src/lua_api.cpp
+++ b/common/src/lua_api.cpp
@@ -30,22 +30,50 @@ std::string rm(Session& context, const std::string& filename) {
   return "";
 }
 
-std::string write_file(Session& context, const std::string& filename,
+std::string write_file(Session& context, const std::string& path,
                        const std::string& content) {
-  vfs_node* current_dir = context.get_current_dir();
-  auto it = current_dir->children.find(filename);
+  vfs_node* parent_dir = nullptr;
+  std::string filename;
 
-  if(it != current_dir->children.end()) {
-    /* File exists, update content. */
+  if(path[0] == '/') {
+    Machine* session_machine = context.get_session_machine();
+    vfs_node* root = session_machine->vfs_root;
+
+    size_t last_slash = path.find_last_of('/');
+    if(last_slash == 0) {
+      /* File in root. */
+      parent_dir = root;
+      filename = path.substr(1);
+    } else {
+      std::string parent_path = path.substr(0, last_slash);
+      parent_dir = find_node_by_path(root, parent_path);
+      filename = path.substr(last_slash+1);
+    }
+  } else {
+    /* Relative path. */
+    parent_dir = context.get_current_dir();
+    filename = path;
+  }
+
+  if(!parent_dir) {
+    return "write: cannot create file '" + path + "': No such file or directory";
+  }
+
+  if(parent_dir->type != DIR_NODE) {
+    return "write: cannot create file in '" + get_full_path(parent_dir) + "': Not a directory";
+  }
+
+  auto it = parent_dir->children.find(filename);
+  if(it != parent_dir->children.end()) {
     if(it->second->type == DIR_NODE) {
-      return "write: " + filename + ": Is a directory.";
+      return "write: " + path + ": Is a directory";
     }
     it->second->content = content;
   } else {
     /* File does not exist, create it. */
-    vfs_node* new_file = new_node(filename, FILE_NODE, current_dir);
+    vfs_node* new_file = new_node(filename, FILE_NODE, parent_dir);
     new_file->content = content;
-    current_dir->children[filename] = new_file;
+    parent_dir->children[filename] = new_file;
   }
   return "";
 }
diff --git a/common/src/lua_api.h b/common/src/lua_api.h
index 57e7a9c..6d685df 100644
--- a/common/src/lua_api.h
+++ b/common/src/lua_api.h
@@ -11,7 +11,7 @@ namespace api {
 /* FILESYSTEM ACTIONS. */
 vfs_node* get_current_dir(Session& context);
 std::string rm(Session& context, const std::string& filename);
-std::string write_file(Session& context, const std::string& filename,
+std::string write_file(Session& context, const std::string& path,
                        const std::string& content);
 std::string ls(Session& context);
 std::string cd(Session& context, const std::string& path);