diff --git a/tests/conftest.py b/tests/conftest.py
index 835ff5e5..33dc81a0 100644
--- a/tests/conftest.py
+++ b/tests/conftest.py
@@ -1,9 +1,28 @@
 from __future__ import annotations
 
+from pathlib import Path
 from typing import Any
 
 import pytest
 
+
+@pytest.fixture(autouse=True)
+def _sandbox_home(tmp_path_factory, monkeypatch):
+    """Every test gets a throwaway HOME so installers/uninstallers can never
+    touch the developer's real ~/.claude, ~/.gemini, ~/.codebuddy, ~/.copilot,
+    ~/.config, ~/.agents (issue #2168).
+
+    Allocated via tmp_path_factory (not inside tmp_path) so tests that assert
+    the exact contents of their own tmp_path are unaffected."""
+    home = tmp_path_factory.mktemp("sandbox-home")
+    monkeypatch.setenv("HOME", str(home))
+    monkeypatch.setenv("USERPROFILE", str(home))              # Windows ntpath.expanduser
+    monkeypatch.setenv("LOCALAPPDATA", str(home / "AppData" / "Local"))
+    monkeypatch.delenv("CLAUDE_CONFIG_DIR", raising=False)     # escape hatch that bypasses Path.home
+    monkeypatch.delenv("XDG_CONFIG_HOME", raising=False)
+    monkeypatch.setattr(Path, "home", classmethod(lambda cls: home))
+    return home
+
 _ANALYZE_WARNING_FILTERS = (
     "ignore:Tensorflow not installed; ParametricUMAP will be unavailable:ImportWarning:umap",
     "ignore:Please import `random` from the `scipy\\.sparse` namespace.*:"
diff --git a/tests/test_home_sandbox.py b/tests/test_home_sandbox.py
new file mode 100644
index 00000000..fc388adc
--- /dev/null
+++ b/tests/test_home_sandbox.py
@@ -0,0 +1,58 @@
+"""Regression tests for the repo-wide HOME sandbox (issue #2168).
+
+The autouse ``_sandbox_home`` fixture in conftest.py must point every
+home-resolution mechanism at a throwaway directory, so installers and
+uninstallers exercised by the suite can never delete or rewrite the
+developer's real ~/.claude, ~/.gemini, ~/.codebuddy, ~/.copilot, etc.
+"""
+from __future__ import annotations
+
+import os
+from pathlib import Path
+
+from graphify.__main__ import claude_uninstall
+
+# Module import happens during collection, before any fixture runs, so this
+# captures the developer's actual home directory for comparison below.
+_REAL_HOME = Path(os.path.realpath(os.path.expanduser("~")))
+
+
+def test_path_home_is_sandboxed(tmp_path_factory):
+    home = Path(os.path.realpath(Path.home()))
+    assert home != _REAL_HOME
+    assert not home.is_relative_to(_REAL_HOME / ".claude")
+    assert home.name.startswith("sandbox-home")
+    basetemp = Path(os.path.realpath(tmp_path_factory.getbasetemp()))
+    assert home.is_relative_to(basetemp)
+
+
+def test_expanduser_is_sandboxed(tmp_path_factory):
+    expanded = Path(os.path.realpath(os.path.expanduser("~")))
+    assert expanded != _REAL_HOME
+    basetemp = Path(os.path.realpath(tmp_path_factory.getbasetemp()))
+    assert expanded.is_relative_to(basetemp)
+
+
+def test_claude_config_dir_escape_hatch_is_cleared():
+    assert "CLAUDE_CONFIG_DIR" not in os.environ
+    assert "XDG_CONFIG_HOME" not in os.environ
+
+
+def test_global_uninstall_is_captured_by_sandbox(tmp_path, tmp_path_factory):
+    """claude_uninstall deletes the *global* ~/.claude/skills/graphify tree.
+
+    Plant that tree inside the sandbox home, run uninstall against an
+    unrelated project dir, and prove the delete landed in the sandbox
+    (and therefore not in the developer's real home).
+    """
+    skill = Path.home() / ".claude" / "skills" / "graphify" / "SKILL.md"
+    skill.parent.mkdir(parents=True)
+    skill.write_text("# graphify skill (sandbox copy)\n", encoding="utf-8")
+
+    project_dir = tmp_path / "some-project"
+    project_dir.mkdir()
+    claude_uninstall(project_dir)
+
+    assert not skill.exists(), "global skill delete was not captured by the sandbox"
+    # And the sandbox home itself is still inside pytest's tmp area.
+    assert Path.home().is_relative_to(tmp_path_factory.getbasetemp())