feat: centralized environment handling, ensures ZEN_MCP_FORCE_ENV_OVERRIDE is honored correctly

fix: updated tests to override env variables they need instead of relying on the current values from .env

tests/conftest.py

@@ -15,6 +15,11 @@ parent_dir = Path(__file__).resolve().parent.parent
 if str(parent_dir) not in sys.path:
     sys.path.insert(0, str(parent_dir))
 
+import utils.env as env_config  # noqa: E402
+
+# Ensure tests operate with runtime environment rather than .env overrides during imports
+env_config.reload_env({"ZEN_MCP_FORCE_ENV_OVERRIDE": "false"})
+
 # Set default model to a specific value for tests to avoid auto mode
 # This prevents all tests from failing due to missing model parameter
 os.environ["DEFAULT_MODEL"] = "gemini-2.5-flash"
@@ -176,3 +181,26 @@ def clear_model_restriction_env(monkeypatch):
 
     for var in restriction_vars:
         monkeypatch.delenv(var, raising=False)
+
+
+@pytest.fixture(autouse=True)
+def disable_force_env_override(monkeypatch):
+    """Default tests to runtime environment visibility unless they explicitly opt in."""
+
+    monkeypatch.setenv("ZEN_MCP_FORCE_ENV_OVERRIDE", "false")
+    env_config.reload_env({"ZEN_MCP_FORCE_ENV_OVERRIDE": "false"})
+    monkeypatch.setenv("DEFAULT_MODEL", "gemini-2.5-flash")
+    monkeypatch.setenv("MAX_CONVERSATION_TURNS", "50")
+
+    import importlib
+
+    import config
+    import utils.conversation_memory as conversation_memory
+
+    importlib.reload(config)
+    importlib.reload(conversation_memory)
+
+    try:
+        yield
+    finally:
+        env_config.reload_env()