diff --git a/tests/conftest.py b/tests/conftest.py
index c134581fe..ffd70a3c3 100644
--- a/tests/conftest.py
+++ b/tests/conftest.py
@@ -27,9 +27,33 @@ def _blank_settings_overlay():
 _blank_settings_overlay()
 
 
+def _own_file_locations():
+    """Keep the suite's results, cache and memory log in a directory of its own.
+
+    Set before the package is imported, whose defaults put them in the user's
+    home: a test reading the user's cache would see what their runs fetched.
+    """
+    import tempfile
+
+    home = tempfile.mkdtemp(prefix="tradingagents-tests-")
+    os.environ["TRADINGAGENTS_RESULTS_DIR"] = os.path.join(home, "logs")
+    os.environ["TRADINGAGENTS_CACHE_DIR"] = os.path.join(home, "cache")
+    os.environ["TRADINGAGENTS_MEMORY_LOG_PATH"] = os.path.join(home, "memory", "trading_memory.md")
+
+
+_own_file_locations()
+
+
 def pytest_configure(config):
     for marker in ("unit", "integration", "smoke"):
         config.addinivalue_line("markers", f"{marker}: {marker}-level tests")
+    # yfinance caches each symbol's time zone on disk, in the home directory
+    # by default; the suite keeps it in a directory of its own.
+    import tempfile
+
+    import yfinance
+
+    yfinance.set_tz_cache_location(tempfile.mkdtemp(prefix="tradingagents-tests-yf-"))
 
 
 @pytest.fixture(autouse=True)
@@ -38,11 +62,17 @@ def _no_network(request, monkeypatch):
     if request.node.get_closest_marker("integration"):
         return
 
-    def refuse(self, address):
-        raise OSError(f"test tried to reach the network: {address}")
+    def refuse(*args, **kwargs):
+        raise OSError(f"test tried to reach the network: {args[1:] or kwargs}")
 
     monkeypatch.setattr(socket.socket, "connect", refuse)
     monkeypatch.setattr(socket.socket, "connect_ex", refuse)
+    monkeypatch.setattr(socket, "getaddrinfo", lambda *a, **k: refuse(None, *a))
+    # yfinance's HTTP client is libcurl, which never touches Python's sockets.
+    from curl_cffi import requests as curl_requests
+
+    monkeypatch.setattr(curl_requests.Session, "request", refuse)
+    monkeypatch.setattr(curl_requests.AsyncSession, "request", refuse)
 
 
 @pytest.fixture(autouse=True)
diff --git a/tests/test_suite_isolation.py b/tests/test_suite_isolation.py
index 7337e232e..a14590d43 100644
--- a/tests/test_suite_isolation.py
+++ b/tests/test_suite_isolation.py
@@ -9,7 +9,10 @@ import pytest
 @pytest.mark.parametrize("connect", [
     lambda: socket.create_connection(("192.0.2.1", 80), timeout=1),
     lambda: socket.socket().connect_ex(("192.0.2.1", 80)),
-], ids=["connect", "connect_ex"])
+    lambda: socket.getaddrinfo("example.com", 443),
+    # yfinance's HTTP client is libcurl, which never touches Python's sockets.
+    lambda: __import__("curl_cffi.requests").requests.Session().get("http://192.0.2.1", timeout=1),
+], ids=["connect", "connect_ex", "dns", "curl_cffi"])
 def test_a_test_cannot_reach_the_network(connect):
     """A test that silently depends on a live vendor passes or fails with the
     machine it runs on; conftest refuses the connection instead."""
@@ -27,3 +30,25 @@ def test_a_test_saves_cli_selections_to_its_own_directory(tmp_path):
 
     assert prefs._PREFS_PATH.is_relative_to(tmp_path)
     assert prefs._PREFS_PATH.exists()
+
+
+@pytest.mark.unit
+def test_yfinance_keeps_its_cache_out_of_the_users_home():
+    """yfinance caches each symbol's time zone on disk, in the home directory by default."""
+    from pathlib import Path
+
+    from yfinance.cache import _TzDBManager
+
+    assert not Path(_TzDBManager.get_location()).is_relative_to(Path.home())
+
+
+@pytest.mark.unit
+@pytest.mark.parametrize("key", ["results_dir", "data_cache_dir", "memory_log_path"])
+def test_the_suite_keeps_its_files_out_of_the_users_home(key):
+    """A test that reads the user's cache sees what their runs fetched, and passes
+    or fails with it; one that writes there changes their data."""
+    from pathlib import Path
+
+    from tradingagents.default_config import DEFAULT_CONFIG
+
+    assert not Path(DEFAULT_CONFIG[key]).is_relative_to(Path.home() / ".tradingagents")