diff --git a/pyproject.toml b/pyproject.toml
index 3ad4b05..773e87b 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -37,6 +37,9 @@ Repository = "https://github.com/milla-jovovich/mempalace"
 [project.scripts]
 mempalace = "mempalace:main"
 
+[project.optional-dependencies]
+dev = ["pytest>=7.0", "ruff>=0.4.0"]
+
 [dependency-groups]
 dev = ["pytest>=7.0", "ruff>=0.4.0"]
 
diff --git a/tests/conftest.py b/tests/conftest.py
index acb9170..757ca51 100644
--- a/tests/conftest.py
+++ b/tests/conftest.py
@@ -3,12 +3,30 @@ conftest.py — Shared fixtures for MemPalace tests.
 
 Provides isolated palace and knowledge graph instances so tests never
 touch the user's real data or leak temp files on failure.
+
+HOME is redirected to a temp directory at module load time — before any
+mempalace imports — so that module-level initialisations (e.g.
+``_kg = KnowledgeGraph()`` in mcp_server) write to a throwaway location
+instead of the real user profile.
 """
 
 import os
 import shutil
 import tempfile
 
+# ── Isolate HOME before any mempalace imports ──────────────────────────
+_original_env = {}
+_session_tmp = tempfile.mkdtemp(prefix="mempalace_session_")
+
+for _var in ("HOME", "USERPROFILE", "HOMEDRIVE", "HOMEPATH"):
+    _original_env[_var] = os.environ.get(_var)
+
+os.environ["HOME"] = _session_tmp
+os.environ["USERPROFILE"] = _session_tmp
+os.environ["HOMEDRIVE"] = os.path.splitdrive(_session_tmp)[0] or "C:"
+os.environ["HOMEPATH"] = os.path.splitdrive(_session_tmp)[1] or _session_tmp
+
+# Now it is safe to import mempalace modules that trigger initialisation.
 import chromadb
 import pytest
 
@@ -16,6 +34,23 @@ from mempalace.config import MempalaceConfig
 from mempalace.knowledge_graph import KnowledgeGraph
 
 
+@pytest.fixture(scope="session", autouse=True)
+def _isolate_home(tmp_path_factory):
+    """Ensure HOME points to a temp dir for the entire test session.
+
+    The env vars were already set at module level (above) so that
+    module-level initialisations are captured.  This fixture simply
+    restores the originals on teardown and cleans up the temp dir.
+    """
+    yield
+    for var, orig in _original_env.items():
+        if orig is None:
+            os.environ.pop(var, None)
+        else:
+            os.environ[var] = orig
+    shutil.rmtree(_session_tmp, ignore_errors=True)
+
+
 @pytest.fixture
 def tmp_dir():
     """Create and auto-cleanup a temporary directory."""
diff --git a/tests/test_mcp_server.py b/tests/test_mcp_server.py
index af72410..c6d8a3a 100644
--- a/tests/test_mcp_server.py
+++ b/tests/test_mcp_server.py
@@ -8,13 +8,10 @@ via monkeypatch to avoid touching real data.
 
 import json
 
-import pytest
-
 
 def _patch_mcp_server(monkeypatch, config, palace_path, kg):
     """Patch the mcp_server module globals to use test fixtures."""
     from mempalace import mcp_server
-    import chromadb
 
     monkeypatch.setattr(mcp_server, "_config", config)
     monkeypatch.setattr(mcp_server, "_kg", kg)
diff --git a/tests/test_searcher.py b/tests/test_searcher.py
index 06dcb5c..6750162 100644
--- a/tests/test_searcher.py
+++ b/tests/test_searcher.py
@@ -4,8 +4,6 @@ test_searcher.py — Tests for the programmatic search_memories API.
 Tests the library-facing search interface (not the CLI print variant).
 """
 
-import chromadb
-
 from mempalace.searcher import search_memories