Fix lmnr import crash when package raises TypeError (#4046)

When lmnr is installed but broken (e.g., on Python 3.13 with certain
package states), importing it raises TypeError instead of ImportError.
Since only ImportError was caught, the TypeError escaped and crashed
the entire application on startup.

Broaden the except clause to catch (ImportError, TypeError) so the
no-op fallback is used in both failure modes.

browser_use/observability.py

@@ -49,7 +49,7 @@ try:
 	if os.environ.get('BROWSER_USE_VERBOSE_OBSERVABILITY', 'false').lower() == 'true':
 		logger.debug('Lmnr is available for observability')
 	_LMNR_AVAILABLE = True
-except ImportError:
+except (ImportError, TypeError):
 	if os.environ.get('BROWSER_USE_VERBOSE_OBSERVABILITY', 'false').lower() == 'true':
 		logger.debug('Lmnr is not available for observability')
 	_LMNR_AVAILABLE = False

tests/ci/test_observability.py

@@ -0,0 +1,102 @@
+"""Tests for observability module's lmnr import error handling.
+
+Regression tests for https://github.com/browser-use/browser-use/issues/4046
+"""
+
+import importlib
+import sys
+from unittest.mock import MagicMock, patch
+
+
+class TestLmnrImportFallback:
+	"""Test that observability gracefully handles lmnr import failures."""
+
+	def _reload_observability(self):
+		"""Reload the observability module to re-trigger import logic."""
+		if 'browser_use.observability' in sys.modules:
+			del sys.modules['browser_use.observability']
+		import browser_use.observability
+
+		return browser_use.observability
+
+	def test_fallback_when_lmnr_not_installed(self):
+		"""Test that observability works when lmnr is not installed (ImportError)."""
+		original_import = __builtins__.__import__ if hasattr(__builtins__, '__import__') else __import__
+
+		def mock_import(name, *args, **kwargs):
+			if name == 'lmnr':
+				raise ImportError('No module named lmnr')
+			return original_import(name, *args, **kwargs)
+
+		with patch('builtins.__import__', side_effect=mock_import):
+			mod = self._reload_observability()
+
+		assert mod._LMNR_AVAILABLE is False
+		assert mod._lmnr_observe is None
+
+		# observe should return a working no-op decorator
+		decorator = mod.observe(name='test')
+		assert callable(decorator)
+
+	def test_fallback_when_lmnr_raises_type_error(self):
+		"""Test that observability works when lmnr raises TypeError on import.
+
+		Regression test for #4046: On some setups (e.g., Python 3.13 with certain
+		package states), lmnr is installed but internally raises TypeError instead
+		of ImportError, crashing the entire application on startup.
+		"""
+		original_import = __builtins__.__import__ if hasattr(__builtins__, '__import__') else __import__
+
+		def mock_import(name, *args, **kwargs):
+			if name == 'lmnr':
+				raise TypeError('unsupported callable')
+			return original_import(name, *args, **kwargs)
+
+		with patch('builtins.__import__', side_effect=mock_import):
+			mod = self._reload_observability()
+
+		assert mod._LMNR_AVAILABLE is False
+		assert mod._lmnr_observe is None
+
+		# observe should return a working no-op decorator
+		decorator = mod.observe(name='test')
+		assert callable(decorator)
+
+	def test_observe_noop_decorator_works_on_sync_function(self):
+		"""Test that the no-op decorator correctly wraps sync functions."""
+		original_import = __builtins__.__import__ if hasattr(__builtins__, '__import__') else __import__
+
+		def mock_import(name, *args, **kwargs):
+			if name == 'lmnr':
+				raise ImportError('No module named lmnr')
+			return original_import(name, *args, **kwargs)
+
+		with patch('builtins.__import__', side_effect=mock_import):
+			mod = self._reload_observability()
+
+		@mod.observe(name='test_func')
+		def my_func(x, y):
+			return x + y
+
+		assert my_func(1, 2) == 3
+
+	def test_observe_noop_decorator_works_on_async_function(self):
+		"""Test that the no-op decorator correctly wraps async functions."""
+		import asyncio
+
+		original_import = __builtins__.__import__ if hasattr(__builtins__, '__import__') else __import__
+
+		def mock_import(name, *args, **kwargs):
+			if name == 'lmnr':
+				raise ImportError('No module named lmnr')
+			return original_import(name, *args, **kwargs)
+
+		with patch('builtins.__import__', side_effect=mock_import):
+			mod = self._reload_observability()
+
+		@mod.observe(name='test_async_func')
+		async def my_async_func(x, y):
+			return x + y
+
+		result = asyncio.get_event_loop().run_until_complete(my_async_func(3, 4))
+		assert result == 7