diff --git a/src/request_tab_widget.py b/src/request_tab_widget.py
index 00c3a4f..e418e45 100644
--- a/src/request_tab_widget.py
+++ b/src/request_tab_widget.py
@@ -20,6 +20,7 @@
 import gi
 gi.require_version('GtkSource', '5')
 from gi.repository import Adw, Gtk, GLib, GtkSource, GObject
+from typing import Optional, Set, Dict, List
 from .models import HttpRequest, HttpResponse
 from .widgets.header_row import HeaderRow
 import json
@@ -32,20 +33,20 @@ class RequestTabWidget(Gtk.Box):
     def __init__(self, tab_id, request=None, response=None, project_id=None, selected_environment_id=None, scripts=None, **kwargs):
         super().__init__(orientation=Gtk.Orientation.VERTICAL, **kwargs)
 
-        self.tab_id = tab_id
-        self.request = request or HttpRequest(method="GET", url="", headers={}, body="", syntax="RAW")
-        self.response = response
-        self.modified = False
-        self.original_request = None
+        self.tab_id: str = tab_id
+        self.request: HttpRequest = request or HttpRequest(method="GET", url="", headers={}, body="", syntax="RAW")
+        self.response: Optional[HttpResponse] = response
+        self.modified: bool = False
+        self.original_request: Optional[HttpRequest] = None
         self.original_scripts = None
-        self.project_id = project_id
-        self.selected_environment_id = selected_environment_id
+        self.project_id: Optional[str] = project_id
+        self.selected_environment_id: Optional[str] = selected_environment_id
         self.scripts = scripts
         self.project_manager = None  # Will be injected from window
-        self.environment_dropdown = None  # Will be created if project_id is set
-        self.env_separator = None  # Visual separator after environment dropdown
-        self.undefined_variables = set()  # Track undefined variables for visual feedback
-        self._update_indicators_timeout_id = None  # Debounce timer for indicator updates
+        self.environment_dropdown: Optional[Gtk.DropDown] = None
+        self.env_separator: Optional[Gtk.Separator] = None
+        self.undefined_variables: Set[str] = set()
+        self._update_indicators_timeout_id: Optional[int] = None
 
         # Build the UI
         self._build_ui()
@@ -61,7 +62,7 @@ class RequestTabWidget(Gtk.Box):
         # Setup change tracking
         self._setup_change_tracking()
 
-    def _build_ui(self):
+    def _build_ui(self) -> None:
         """Build the complete UI for this tab."""
 
         # URL Input Section - outer container (store as instance var for dynamic updates)
@@ -366,7 +367,7 @@ class RequestTabWidget(Gtk.Box):
 
         self.append(split_pane)
 
-    def _build_headers_tab(self):
+    def _build_headers_tab(self) -> None:
         """Build the headers tab."""
         headers_scroll = Gtk.ScrolledWindow()
         headers_scroll.set_vexpand(True)
@@ -392,7 +393,7 @@ class RequestTabWidget(Gtk.Box):
         # Add initial empty header row
         self._add_header_row()
 
-    def _build_body_tab(self):
+    def _build_body_tab(self) -> None:
         """Build the body tab."""
         body_box = Gtk.Box(orientation=Gtk.Orientation.VERTICAL, spacing=0)
 
@@ -706,7 +707,7 @@ class RequestTabWidget(Gtk.Box):
             self.headers_listbox.remove(parent)
             self._on_request_changed(None)
 
-    def _setup_change_tracking(self):
+    def _setup_change_tracking(self) -> None:
         """Setup change tracking for this tab."""
         self.url_entry.connect("changed", self._on_request_changed)
         self.method_dropdown.connect("notify::selected", self._on_request_changed)
@@ -745,7 +746,7 @@ class RequestTabWidget(Gtk.Box):
         'modified-changed': (GObject.SignalFlags.RUN_FIRST, None, (bool,))
     }
 
-    def _is_different_from_original(self, request):
+    def _is_different_from_original(self, request: HttpRequest) -> bool:
         """Check if current request differs from original."""
         if not self.original_request:
             return False
@@ -776,7 +777,7 @@ class RequestTabWidget(Gtk.Box):
 
         return request_changed or scripts_changed
 
-    def _load_request(self, request):
+    def _load_request(self, request: HttpRequest) -> None:
         """Load a request into this tab's UI."""
         # Set method
         methods = ["GET", "POST", "PUT", "DELETE"]
@@ -805,7 +806,7 @@ class RequestTabWidget(Gtk.Box):
         if request.syntax in syntax_options:
             self.body_language_dropdown.set_selected(syntax_options.index(request.syntax))
 
-    def get_request(self):
+    def get_request(self) -> HttpRequest:
         """Build and return HttpRequest from current UI state."""
         method = self.method_dropdown.get_selected_item().get_string()
         url = self.url_entry.get_text().strip()
@@ -868,7 +869,7 @@ class RequestTabWidget(Gtk.Box):
         postprocessing_buffer = self.postprocessing_sourceview.get_buffer()
         postprocessing_buffer.set_text(scripts.postprocessing)
 
-    def display_response(self, response):
+    def display_response(self, response: HttpResponse) -> None:
         """Display response in this tab's UI."""
         self.response = response
 
@@ -896,7 +897,7 @@ class RequestTabWidget(Gtk.Box):
         language = self._get_language_from_content_type(content_type)
         source_buffer.set_language(language)
 
-    def display_error(self, error):
+    def display_error(self, error: str) -> None:
         """Display error in this tab's UI."""
         self.status_label.set_text("Error")
         self.time_label.set_text("")