diff --git a/tests/test_no_assessment_backed_proposal_synthesis.py b/tests/test_no_assessment_backed_proposal_synthesis.py
new file mode 100644
index 00000000..754b669e
--- /dev/null
+++ b/tests/test_no_assessment_backed_proposal_synthesis.py
@@ -0,0 +1,48 @@
+from __future__ import annotations
+
+import dataclasses
+
+import generate.construction_affordances as construction_affordances
+from generate.problem_frame_builder import build_problem_frame
+from generate.problem_frame_contracts import assess_contracts
+
+
+def test_builder_does_not_synthesize_proposals_from_assessments(monkeypatch) -> None:
+    """Construction proposals must originate before ContractAssessment.
+
+    This pins the proposal-first boundary against the stale assessment-backed
+    synthesis path: even when ``make_proposal`` is monkeypatched to fail loudly,
+    a normal proposal-backed frame must build without consulting it.
+    """
+
+    calls: list[dict[str, object]] = []
+
+    def forbidden_make_proposal(**kwargs):  # type: ignore[no-untyped-def]
+        calls.append(dict(kwargs))
+        raise AssertionError(
+            "build_problem_frame must not synthesize ConstructionProposal "
+            "objects from ContractAssessment output"
+        )
+
+    monkeypatch.setattr(
+        construction_affordances,
+        "make_proposal",
+        forbidden_make_proposal,
+    )
+
+    frame = build_problem_frame("Mia has 7 apples. How many apples does Mia have?")
+
+    assert calls == []
+    assert tuple(proposal.family_id for proposal in frame.proposals) == (
+        "binding.quantity_entity",
+    )
+    assert all(proposal.status == "proposed" for proposal in frame.proposals)
+
+
+def test_contract_assessments_do_not_create_proposal_free_fallback_source() -> None:
+    """A proposal-free frame must not produce assessments for backfill synthesis."""
+
+    frame = build_problem_frame("Mia has 7 apples. How many apples does Mia have?")
+    proposal_free_frame = dataclasses.replace(frame, proposals=())
+
+    assert assess_contracts(proposal_free_frame) == ()