diff --git a/genesis/ext/pyrender/viewer.py b/genesis/ext/pyrender/viewer.py
index fbbf92bbb1..fa29be1551 100644
--- a/genesis/ext/pyrender/viewer.py
+++ b/genesis/ext/pyrender/viewer.py
@@ -19,16 +19,21 @@
 
 # Importing tkinter and creating a first context before importing pyglet is necessary to avoid later segfault on MacOS.
 # Note that destroying the window will cause segfault at exit.
+# On macOS 26+ (Darwin 25, Tahoe), system Tk 8.5 crashes on init due to a Darwin/product version mismatch.
+# The pyglet segfault workaround is not needed on macOS 26+.
 root = None
 if sys.platform.startswith("darwin"):
-    try:
-        from tkinter import Tk
+    import platform as _platform
+    _mac_major = int(_platform.mac_ver()[0].split(".")[0]) if _platform.mac_ver()[0] else 0
+    if _mac_major < 26:
+        try:
+            from tkinter import Tk
 
-        root = Tk()
-        root.withdraw()
-    except Exception:
-        # Some minimal Python install may not provide a working tkinter interface even if it is a standard library
-        pass
+            root = Tk()
+            root.withdraw()
+        except Exception:
+            # Some minimal Python install may not provide a working tkinter interface even if it is a standard library
+            pass
 
 import pyglet
 
@@ -1212,6 +1217,16 @@ def start(self, auto_refresh=True):
         self.set_caption(self.viewer_flags["window_title"])
         self.activate()
 
+        # On macOS, we need to explicitly activate the app to bring the window to focus
+        # when running from terminal (not as a bundled .app)
+        if sys.platform.startswith("darwin"):
+            try:
+                from AppKit import NSApp, NSApplication
+                NSApplication.sharedApplication()
+                NSApp.activateIgnoringOtherApps_(True)
+            except ImportError:
+                gs.logger.debug("PyObjC not available, window may not come to focus automatically")
+
         # The viewer can be considered as fully initialized at this point
         if not self._initialized_event.is_set():
             self._initialized_event.set()
@@ -1240,6 +1255,18 @@ def run(self):
         elif threading.main_thread() != threading.current_thread():
             raise RuntimeError("'Viewer.run' can only be called manually from main thread on MacOS.")
 
+        # On macOS, we need to explicitly activate the app to bring the window to focus
+        # when running from terminal (not as a bundled .app)
+        if sys.platform.startswith("darwin"):
+            try:
+                from AppKit import NSApp, NSApplication
+                NSApplication.sharedApplication()
+                NSApp.activateIgnoringOtherApps_(True)
+                # Also request the window to be frontmost
+                self.activate()
+            except ImportError:
+                gs.logger.debug("PyObjC not available, window may not come to focus automatically")
+
         while self._is_active:
             try:
                 self.refresh()
diff --git a/genesis/vis/visualizer.py b/genesis/vis/visualizer.py
index 51524abbf1..b539d866c5 100644
--- a/genesis/vis/visualizer.py
+++ b/genesis/vis/visualizer.py
@@ -66,9 +66,9 @@ def __init__(self, scene, show_viewer, vis_options, viewer_options, renderer_opt
             if viewer_options.run_in_thread is None:
                 if sys.platform == "linux":
                     viewer_options.run_in_thread = True
-                elif sys.platform == "darwin":
+                elif sys.platform == "darwin" or gs.platform == "macOS":
                     viewer_options.run_in_thread = False
-                elif sys.platform == "win32":
+                elif sys.platform == "win32" or  gs.platform == "Windows":
                     viewer_options.run_in_thread = True
             if sys.platform == "darwin" and viewer_options.run_in_thread:
                 gs.raise_exception("Running viewer in background thread is not supported on MacOS.")
diff --git a/pyproject.toml b/pyproject.toml
index 0f5ff142f5..682c9fb783 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -66,6 +66,8 @@ dependencies = [
     "fast_simplification>=0.1.12",
     # Surface reconstruction library for particle data from SPH simulations
     "pysplashsurf==0.14.*",
+     # Used on macOS to properly bring the viewer window to focus when running from terminal
+    "pyobjc-framework-Cocoa; sys_platform == 'darwin'",
 ]
 
 [project.optional-dependencies]