diff --git a/tests/test_agent_loop.py b/tests/test_agent_loop.py
index 3726991..e30a87b 100644
--- a/tests/test_agent_loop.py
+++ b/tests/test_agent_loop.py
@@ -4,22 +4,57 @@ and _append_tool_results. Uses mock imports to avoid loading the full app stack.
 import sys
 from unittest.mock import MagicMock
 
-# Mock heavy dependencies before importing
-for mod in [
+_MOCKED_IMPORTS = [
     'sqlalchemy', 'sqlalchemy.orm', 'sqlalchemy.ext', 'sqlalchemy.ext.declarative',
     'sqlalchemy.ext.hybrid', 'sqlalchemy.sql', 'sqlalchemy.sql.expression',
     'src.database',
     'src.agent_tools',
     'core.models', 'core.database',
-]:
-    if mod not in sys.modules:
-        sys.modules[mod] = MagicMock()
+]
+_INJECTED_IMPORT_STUBS = {}
+_PREEXISTING_AGENT_LOOP = sys.modules.get("src.agent_loop")
 
-from src.agent_loop import (
-    _detect_admin_intent,
-    _compute_final_metrics,
-    _append_tool_results,
-)
+
+def _drop_module_if_same(name, expected):
+    if sys.modules.get(name) is expected:
+        sys.modules.pop(name, None)
+    parent_name, _, attr = name.rpartition(".")
+    parent = sys.modules.get(parent_name)
+    if parent is not None and getattr(parent, "__dict__", {}).get(attr) is expected:
+        delattr(parent, attr)
+
+
+# Mock heavy dependencies before importing. Only clean up stubs this file
+# created so pre-existing conftest/pytest modules keep their intended state.
+for mod in _MOCKED_IMPORTS:
+    if mod not in sys.modules:
+        stub = MagicMock()
+        sys.modules[mod] = stub
+        _INJECTED_IMPORT_STUBS[mod] = stub
+
+_IMPORTED_AGENT_LOOP = None
+try:
+    from src.agent_loop import (
+        _detect_admin_intent,
+        _compute_final_metrics,
+        _append_tool_results,
+    )
+    _IMPORTED_AGENT_LOOP = sys.modules.get("src.agent_loop")
+finally:
+    if _PREEXISTING_AGENT_LOOP is None and _IMPORTED_AGENT_LOOP is not None:
+        _drop_module_if_same("src.agent_loop", _IMPORTED_AGENT_LOOP)
+    for _mod, _stub in _INJECTED_IMPORT_STUBS.items():
+        _drop_module_if_same(_mod, _stub)
+
+
+def test_import_stubs_do_not_leak_into_later_tests():
+    leaked = [
+        mod for mod, stub in _INJECTED_IMPORT_STUBS.items()
+        if sys.modules.get(mod) is stub
+    ]
+    assert leaked == []
+    if _PREEXISTING_AGENT_LOOP is None:
+        assert sys.modules.get("src.agent_loop") is not _IMPORTED_AGENT_LOOP
 
 
 # ---------------------------------------------------------------------------