diff --git a/core/tests/test_modifiers_provided.py b/core/tests/test_modifiers_provided.py
new file mode 100644
index 00000000..9844ce82
--- /dev/null
+++ b/core/tests/test_modifiers_provided.py
@@ -0,0 +1,23 @@
+"""A module with an `install(patcher, values, key)` that never lists it in PROVIDES is never installed (the
+Load Modifiers node only calls what is provided), and its own tests still pass because they call it directly."""
+
+import importlib
+import pkgutil
+
+import modules
+
+
+def test_every_modifier_install_is_provided():
+    missing = []
+    for info in pkgutil.walk_packages(modules.__path__, "modules."):
+        if not info.ispkg or info.name.rsplit(".", 1)[-1] in ("tests", "_core"):
+            continue
+        try:
+            mod = importlib.import_module(info.name)
+        except Exception:                               # noqa: BLE001 -- a missing dependency is not this test's business
+            continue
+        fn = getattr(mod, "install", None)
+        if fn is not None and getattr(mod, "__file__", "").endswith("__init__.py") and hasattr(mod, "ID"):
+            if getattr(mod, "PROVIDES", {}).get("modifier") is not fn:
+                missing.append(info.name)
+    assert not missing, f"install() not provided as a modifier: {missing}"
diff --git a/modules/sampling/two_stage/__init__.py b/modules/sampling/two_stage/__init__.py
index 5df64895..b7d0dfad 100644
--- a/modules/sampling/two_stage/__init__.py
+++ b/modules/sampling/two_stage/__init__.py
@@ -52,3 +52,6 @@ def install(patcher, values, key):
     size, steps = float(values.get("size", 0.7)), int(values.get("steps", 2))
     patcher.add_wrapper_with_key(WrappersMP.OUTER_SAMPLE, key, make_wrapper(size, steps))
     return f"first {steps} step(s) at {size:.0%} of the size"
+
+
+PROVIDES = {"modifier": install}