test: cover product delete cascade (group + own sessions) keeping other-org sessions

Proves DELETE /api/groups/<gid> removes the product, its personas (stored on the
group), its own sessions, and uploads, while sessions of an unrelated product/
org survive. Guards the cascade against future regressions.

backend/tests/test_security_review_blockers.py

@@ -1285,3 +1285,82 @@ def test_malformed_visibility_legacy_syntax_not_migrated(client, user_store, log
     from app.services.groups import resolved_visibility
 
     assert resolved_visibility({"visibility": "evil", "owner_user_id": "x"}) is None
+
+
+def test_delete_group_cascades_sessions_and_keeps_other_org_sessions(
+    client, user_store, login
+):
+    """Deleting a product removes the group, its personas (stored in the group),
+    its own sessions, and uploaded filenames — but not sessions of another group."""
+    # Admin in org-default
+    admin_token = _setup_admin(user_store, login)
+    _create_user(user_store, login, username="trainee-delete-cascade", org_id="org-default")
+
+    groups = client.application.extensions["group_store"]
+    sess = client.application.extensions["session_store"]
+
+    # Build a ready product (group) directly with one persona.
+    g = groups.create(
+        org_id="org-default",
+        creator_id="admin",
+        title="Cascade test product",
+        status="ready",
+        input_data={"files": ["upload-a.pdf"]},
+        sales_kit={"productName": "Cascade product"},
+        report={"summary": "Cascade report"},
+        personas=[{"id": "p-1", "name": "Persona One", "tier": "A"}],
+    )
+    gid = g["id"]
+
+    # A real session (chat) bound to this product + same org.
+    sess.sessions.create({
+        "id": "sess-p1",
+        "org_id": "org-default",
+        "user_id": "trainee-delete-cascade",
+        "group_id": gid,
+        "persona_id": "p-1",
+        "persona_name": "Persona One",
+        "mode": "trainee",
+        "status": "finished",
+        "outcome": "won",
+        "debrief": {"score": 80},
+    }, key="sess-p1")
+
+    # A session of ANOTHER (different) group that must survive.
+    g2 = groups.create(
+        org_id="org-default",
+        creator_id="admin",
+        title="Other product",
+        status="ready",
+        sales_kit={"productName": "Other"},
+        report={"summary": "R"},
+        personas=[{"id": "p-x", "name": "Persona X", "tier": "B"}],
+    )
+    sess.sessions.create({
+        "id": "sess-x",
+        "org_id": "org-default",
+        "user_id": "trainee-delete-cascade",
+        "group_id": g2["id"],
+        "persona_id": "p-x",
+        "persona_name": "Persona X",
+        "mode": "trainee",
+        "status": "finished",
+        "outcome": "lost",
+    }, key="sess-x")
+
+    # Sanity: product + its session + other session exist before delete.
+    assert groups.get_or_none(gid) is not None
+    assert sess.sessions.get_or_none("sess-p1") is not None
+    assert sess.sessions.get_or_none("sess-x") is not None
+
+    # Delete the product via the API (admin).
+    resp = client.delete(f"/api/groups/{gid}", headers=_headers(admin_token))
+    assert resp.status_code == 200, resp.get_json()
+
+    # Product + its personas (group) and its own session are gone.
+    assert groups.get_or_none(gid) is None
+    assert sess.sessions.get_or_none("sess-p1") is None
+    # An unrelated session survives.
+    assert sess.sessions.get_or_none("sess-x") is not None
+    # Other product survives.
+    assert groups.get_or_none(g2["id"]) is not None