diff --git a/tests/__init__.py b/tests/__init__.py
index ccccefe..a393c18 100644
--- a/tests/__init__.py
+++ b/tests/__init__.py
@@ -1 +1,39 @@
-"""Tests for the sp CLI (sp_cli)."""
+"""Tests for the sp CLI (sp_cli).
+
+Redirect the saved-session location before any test touches it.
+
+``sp auth login`` writes a bearer token to ``$XDG_CONFIG_HOME/sp/config.json``,
+so a test reaching that code path writes to the developer's *real* config. The
+plaintext token is returned only at creation, so an overwritten session is
+unrecoverable -- and this has now cost a live token twice.
+
+``tests/conftest.py`` already guards this, but only under pytest: conftest is a
+pytest mechanism, and the suite is also run with ``unittest`` and ``nose2``,
+where the fixture is never loaded and the guard silently does nothing.
+
+Putting the redirect in the package ``__init__`` covers pytest, ``nose2``, and
+``python -m unittest discover`` from the repository root. It does *not* cover
+``python -m unittest discover -s tests``, which imports test modules top-level
+and never imports this package -- which is why every test module imports
+``SESSION_SANDBOX`` below explicitly. ``conftest.py`` still narrows this to a
+per-test directory under pytest; overriding an already-redirected variable is
+harmless.
+"""
+
+import atexit
+import os
+import shutil
+import tempfile
+
+#: Throwaway root standing in for the developer's home during tests. Test
+#: modules import this name so that importing them runs the redirect below,
+#: whichever runner collected them.
+SESSION_SANDBOX = tempfile.mkdtemp(prefix='sp-cli-tests-')
+
+# HOME as well as XDG_CONFIG_HOME: config_path() falls back to ~/.config when
+# XDG_CONFIG_HOME is unset, so redirecting only the latter leaves a gap.
+os.environ['XDG_CONFIG_HOME'] = os.path.join(SESSION_SANDBOX, 'config')
+os.environ['HOME'] = os.path.join(SESSION_SANDBOX, 'home')
+os.makedirs(os.environ['HOME'], exist_ok=True)
+
+atexit.register(shutil.rmtree, SESSION_SANDBOX, True)
diff --git a/tests/test_classifier.py b/tests/test_classifier.py
index 34df46c..d9d3f05 100644
--- a/tests/test_classifier.py
+++ b/tests/test_classifier.py
@@ -3,6 +3,7 @@
 import unittest
 
 from sp_cli import classifier
+from tests import SESSION_SANDBOX  # noqa: F401
 
 
 class ClassifierTests(unittest.TestCase):
diff --git a/tests/test_cli.py b/tests/test_cli.py
index e299358..55b6915 100644
--- a/tests/test_cli.py
+++ b/tests/test_cli.py
@@ -8,6 +8,7 @@
 
 from sp_cli.client import ApiError
 from sp_cli.main import cli
+from tests import SESSION_SANDBOX  # noqa: F401
 
 RUNS_PAGE = {
     'data': [{'run_id': 9299, 'status': 'fail', 'platform': 'windows', 'commit_sha': 'e6cd34e'}],
diff --git a/tests/test_client.py b/tests/test_client.py
index 90acb7f..67ffce4 100644
--- a/tests/test_client.py
+++ b/tests/test_client.py
@@ -6,6 +6,7 @@
 import requests  # type: ignore[import-untyped]
 
 from sp_cli.client import ApiClient, ApiError
+from tests import SESSION_SANDBOX  # noqa: F401
 
 
 class FakeResponse:
diff --git a/tests/test_compare.py b/tests/test_compare.py
index ce8ff1c..c14ae8d 100644
--- a/tests/test_compare.py
+++ b/tests/test_compare.py
@@ -3,6 +3,7 @@
 import unittest
 
 from sp_cli import compare
+from tests import SESSION_SANDBOX  # noqa: F401
 
 
 def sample(test_id, status, exit_code=0, expected_rc=0, outputs=None):
diff --git a/tests/test_history.py b/tests/test_history.py
index 5f63204..347cc48 100644
--- a/tests/test_history.py
+++ b/tests/test_history.py
@@ -5,6 +5,7 @@
 from sp_cli.history import (FLAKY, NEVER_PASSED, NEW_REGRESSION, NO_HISTORY,
                             STILL_FAILING, UNKNOWN, classify_history,
                             group_by_verdict, split_history, unknown_history)
+from tests import SESSION_SANDBOX  # noqa: F401
 
 
 def entry(run_id, status, regression_test_id=137, signature=None):
diff --git a/tests/test_triage.py b/tests/test_triage.py
index 5a570c9..0f28da9 100644
--- a/tests/test_triage.py
+++ b/tests/test_triage.py
@@ -3,6 +3,7 @@
 import unittest
 
 from sp_cli import triage
+from tests import SESSION_SANDBOX  # noqa: F401
 
 
 class IsFailureTests(unittest.TestCase):
diff --git a/tests/test_ux.py b/tests/test_ux.py
index 1f493cd..c3c1f35 100644
--- a/tests/test_ux.py
+++ b/tests/test_ux.py
@@ -16,6 +16,7 @@
 from sp_cli import config
 from sp_cli.main import cli
 from sp_cli.output import render
+from tests import SESSION_SANDBOX  # noqa: F401
 
 CLASSIFIED_ROWS = {
     'data': [