diff --git a/api/tests/test_containers_integration_tests/conftest.py b/api/tests/test_containers_integration_tests/conftest.py
index ee953fcbfe..dd742f99d0 100644
--- a/api/tests/test_containers_integration_tests/conftest.py
+++ b/api/tests/test_containers_integration_tests/conftest.py
@@ -505,7 +505,7 @@ def _truncate_container_database(app: Flask) -> None:
     session_factory-created sessions. Truncating after each test gives the suite
     a central DB isolation contract that does not depend on which session a test used.
     This only covers SQLAlchemy application tables in db.metadata for now;
-    Redis, object storage, and custom ad hoc metadata still need their own cleanup.
+    object storage and custom ad hoc metadata still need their own cleanup.
     """
     with app.app_context():
         db.session.remove()
@@ -524,13 +524,27 @@ def _truncate_container_database(app: Flask) -> None:
         db.session.remove()
 
 
+def _flush_container_redis(app: Flask) -> None:
+    """
+    Reset Redis after a container integration test.
+
+    Tests in this package share one Redis container for performance. Application
+    code stores temporary tokens, rate-limit counters, locks, and cache entries
+    there, so flushing after each test gives Redis-backed state the same
+    isolation contract as the PostgreSQL container.
+    """
+    with app.app_context():
+        app.extensions["redis"].flushdb()
+
+
 @pytest.fixture(autouse=True)
 def isolate_container_database(request: pytest.FixtureRequest) -> Generator[None, None, None]:
     """
-    Clean DB state after tests that use the containerized Flask app.
+    Clean DB and Redis state after tests that use the containerized Flask app.
 
     This fixture intentionally does not depend on flask_app_with_containers so
-    non-DB tests under this package do not start the full app/container stack.
+    tests under this package do not start the full app/container stack just to
+    run state cleanup.
     """
     yield
 
@@ -538,7 +552,10 @@ def isolate_container_database(request: pytest.FixtureRequest) -> Generator[None
         return
 
     app = request.getfixturevalue("flask_app_with_containers")
-    _truncate_container_database(app)
+    try:
+        _truncate_container_database(app)
+    finally:
+        _flush_container_redis(app)
 
 
 @pytest.fixture(scope="package", autouse=True)
diff --git a/api/tests/test_containers_integration_tests/test_container_state_isolation.py b/api/tests/test_containers_integration_tests/test_container_state_isolation.py
new file mode 100644
index 0000000000..702460c5ad
--- /dev/null
+++ b/api/tests/test_containers_integration_tests/test_container_state_isolation.py
@@ -0,0 +1,39 @@
+from __future__ import annotations
+
+from uuid import uuid4
+
+from extensions.ext_redis import redis_client
+from models.account import Account
+
+ACCOUNT_EMAIL = f"container-state-isolation-{uuid4()}@example.com"
+REDIS_KEY = f"container-state-isolation:{uuid4()}"
+
+
+def test_1_container_state_can_be_written(
+    flask_app_with_containers,
+    db_session_with_containers,
+) -> None:
+    account = Account(
+        name="Container State Isolation",
+        email=ACCOUNT_EMAIL,
+        password="hashed-password",
+        password_salt="salt",
+        interface_language="en-US",
+        timezone="UTC",
+    )
+    db_session_with_containers.add(account)
+    db_session_with_containers.commit()
+
+    with flask_app_with_containers.app_context():
+        redis_client.set(REDIS_KEY, "leaked")
+        assert redis_client.get(REDIS_KEY) == b"leaked"
+
+
+def test_2_container_state_is_flushed_between_tests(
+    flask_app_with_containers,
+    db_session_with_containers,
+) -> None:
+    assert db_session_with_containers.query(Account).filter_by(email=ACCOUNT_EMAIL).one_or_none() is None
+
+    with flask_app_with_containers.app_context():
+        assert redis_client.get(REDIS_KEY) is None