diff --git a/backend/tests/test_products_invariants.py b/backend/tests/test_products_invariants.py
index 3f9db0f..7e045cb 100644
--- a/backend/tests/test_products_invariants.py
+++ b/backend/tests/test_products_invariants.py
@@ -77,3 +77,25 @@ def test_apply_failure_rolls_back_whole_transaction_tel6(migrated_conn, monkeypa
     assert migrated_conn.execute("SELECT count(*) FROM import_draft").fetchone()[0] == 1
     events = [json.loads(r.message) for r in caplog.records if r.name == "ecomm.telemetry"]
     assert any(e["event"] == "import_apply_failed" and e["error_class"] == "RuntimeError" for e in events)
+
+
+# A partial Shopify export (signature: Body (HTML) + Variant Grams) naming only one
+# of the two existing products — INV-10 must hold across the dialect boundary.
+SHOPIFY_PARTIAL = (
+    b"Handle,Title,Body (HTML),Variant Price,Variant Grams\n"
+    b"mug,Mug,<p>x</p>,12.00,180\n"
+)
+
+
+def test_inv10_shopify_partial_never_deletes(migrated_conn):
+    acct, sf = _merchant(migrated_conn)
+    _import(migrated_conn, acct, sf, CSV_A)
+    before = migrated_conn.execute("SELECT count(*) FROM product").fetchone()[0]
+    d = products.import_validate(migrated_conn, sf, acct, "shopify.csv", SHOPIFY_PARTIAL)
+    assert d["dialect"] == "shopify"
+    products.confirm_draft(migrated_conn, sf, acct, d["id"])
+    after = migrated_conn.execute("SELECT count(*) FROM product").fetchone()[0]
+    # INV-10: nothing deleted; the unmentioned 'tee' is untouched.
+    assert after >= before == 2
+    handles = {r[0] for r in migrated_conn.execute("SELECT handle FROM product").fetchall()}
+    assert {"mug", "tee"} <= handles