diff --git a/workflowai/core/domain/run_test.py b/workflowai/core/domain/run_test.py
index ac0aae7..25d4f94 100644
--- a/workflowai/core/domain/run_test.py
+++ b/workflowai/core/domain/run_test.py
@@ -137,8 +137,16 @@ def test_format_output_no_cost_latency():
 
 
 class TestRunURL:
+    # The @patch decorator from unittest.mock temporarily replaces the value of an attribute
+    # during the execution of the decorated test function. The original value is restored
+    # after the test completes.
+
+    # To check what happens in different environemnt configurations, see env_test.py
+
+    # Here we patch WORKFLOWAI_APP_URL to test the direct app URL case
     @patch("workflowai.env.WORKFLOWAI_APP_URL", "https://workflowai.hello")
     def test_run_url(self, run1: Run[_TestOutput]):
+        # The patched value is only active during this test method
         assert run1.run_url == "https://workflowai.hello/_/agents/agent-id/runs/run-id"
 
 
diff --git a/workflowai/env.py b/workflowai/env.py
index 46cfc4b..4aa7591 100644
--- a/workflowai/env.py
+++ b/workflowai/env.py
@@ -4,7 +4,7 @@
 
 WORKFLOWAI_DEFAULT_MODEL = os.getenv("WORKFLOWAI_DEFAULT_MODEL", "gemini-1.5-pro-latest")
 
-WORKFLOWAI_API_URL = os.getenv("WORKFLOWAI_API_URL")
+WORKFLOWAI_API_URL = os.getenv("WORKFLOWAI_API_URL", "https://run.workflowai.com")
 
 
 def _default_app_url():
diff --git a/workflowai/env_test.py b/workflowai/env_test.py
index c20824b..a1878f8 100644
--- a/workflowai/env_test.py
+++ b/workflowai/env_test.py
@@ -1,9 +1,40 @@
+import importlib
+import os
 from typing import Optional
 from unittest.mock import patch
 
 import pytest
 
-from .env import _default_app_url  # pyright: ignore[reportPrivateUsage]
+from workflowai import env
+
+
+# Check what happens when the environment is fully empty
+@patch.dict(os.environ, clear=True)
+def test_default_app_url_clear_env():
+    # We need to reload the env module so that the environment variables are read again
+    importlib.reload(env)
+    assert env.WORKFLOWAI_API_URL == "https://run.workflowai.com"
+    assert env.WORKFLOWAI_APP_URL == "https://workflowai.com"
+
+
+# Check with the default app url when an api url is provided
+@patch.dict(os.environ, {"WORKFLOWAI_API_URL": "https://run.workflowai.dev"}, clear=True)
+def test_default_app_url_dev_url():
+    importlib.reload(env)
+    assert env.WORKFLOWAI_API_URL == "https://run.workflowai.dev"
+    assert env.WORKFLOWAI_APP_URL == "https://workflowai.dev"
+
+
+# Check the app url when both api url and app url are provided
+@patch.dict(
+    os.environ,
+    {"WORKFLOWAI_API_URL": "https://run.workflowai.dev", "WORKFLOWAI_APP_URL": "https://workflowai.app"},
+    clear=True,
+)
+def test_with_app_url():
+    importlib.reload(env)
+    assert env.WORKFLOWAI_API_URL == "https://run.workflowai.dev"
+    assert env.WORKFLOWAI_APP_URL == "https://workflowai.app"
 
 
 @pytest.mark.parametrize(
@@ -16,5 +47,6 @@
     ],
 )
 def test_default_app_url(api_url: Optional[str], expected: str):
+    # Importing here to avoid setting the environment variables before the test
     with patch("workflowai.env.WORKFLOWAI_API_URL", api_url):
-        assert _default_app_url() == expected
+        assert env._default_app_url() == expected  # pyright: ignore[reportPrivateUsage]