From 386fe8ca52ba9def121e050993cdb5317f37c184 Mon Sep 17 00:00:00 2001
From: Seongho Bae <me@seonghobae.me>
Date: Wed, 12 Aug 2026 02:42:06 +0900
Subject: [PATCH] test(jmle): require Rust-owned optimizer loops on current
 main

---
 tests/test_jmle_rust_optimizer_ownership.py | 66 +++++++++++++++++++++
 1 file changed, 66 insertions(+)
 create mode 100644 tests/test_jmle_rust_optimizer_ownership.py

diff --git a/tests/test_jmle_rust_optimizer_ownership.py b/tests/test_jmle_rust_optimizer_ownership.py
new file mode 100644
index 000000000..5f4512d6e
--- /dev/null
+++ b/tests/test_jmle_rust_optimizer_ownership.py
@@ -0,0 +1,66 @@
+"""Fail-first production ownership contract for JMLE optimization.
+
+The public JMLE path may validate, initialize, marshal, and report in Python,
+but Adam/L-BFGS optimizer state updates and convergence control are production
+psychometric numerical work and must not execute through the legacy Python
+optimizer loops.
+"""
+
+from __future__ import annotations
+
+import importlib
+
+import pytest
+
+from fast_mlsirm import FitConfig, MLS2PLMConfig, simulate
+
+
+fit_module = importlib.import_module("fast_mlsirm.fit")
+
+
+@pytest.mark.parametrize("optimizer", ["adam", "lbfgs", "adam_lbfgs"])
+def test_public_jmle_optimization_does_not_execute_python_optimizer_loops(
+    monkeypatch: pytest.MonkeyPatch,
+    optimizer: str,
+) -> None:
+    """Installed Rust-backed JMLE must not delegate optimizer arithmetic to Python."""
+    pytest.importorskip("fast_mlsirm._core")
+    data = simulate(
+        MLS2PLMConfig(
+            n_persons=12,
+            n_dims=1,
+            items_per_dim=3,
+            latent_dim=1,
+            seed=626,
+        )
+    )
+    python_optimizer_calls: list[str] = []
+
+    def forbidden_python_adam(*_args: object, **_kwargs: object) -> object:
+        python_optimizer_calls.append("adam")
+        raise AssertionError("public JMLE executed Python Adam arithmetic")
+
+    def forbidden_python_lbfgs(*_args: object, **_kwargs: object) -> object:
+        python_optimizer_calls.append("lbfgs")
+        raise AssertionError("public JMLE executed Python L-BFGS arithmetic")
+
+    monkeypatch.setattr(fit_module, "_adam", forbidden_python_adam)
+    monkeypatch.setattr(fit_module, "_lbfgs", forbidden_python_lbfgs)
+
+    result = fit_module.fit(
+        data.Y,
+        data.factor_id,
+        config=FitConfig(
+            model="MLS2PLM",
+            estimator="jmle",
+            optimizer=optimizer,
+            max_iter=2,
+            n_restarts=1,
+            seed=626,
+            backend="rust",
+        ),
+    )
+
+    assert python_optimizer_calls == []
+    assert result.backend == "rust"
+    assert result.optimizer == optimizer