diff --git a/backend/pipeline/constructability.py b/backend/pipeline/constructability.py
index ed1c735..e8265e1 100644
--- a/backend/pipeline/constructability.py
+++ b/backend/pipeline/constructability.py
@@ -27,6 +27,10 @@ def constructability_review(sheets: List[Dict], clusters: List[Dict],
             "assertions": dumps(slim_sheets(sheets)),
             "clusters": dumps(slim_clusters(clusters)),
             "conflicts": dumps(conflicts),
+            "disputes": dumps([
+                d for cluster in clusters
+                for d in (cluster.get("disputed_attributes") or [])
+            ]),
         },
         max_tokens=config.CONSTRUCT_MAX_TOKENS,
     )
diff --git a/backend/pipeline/runner.py b/backend/pipeline/runner.py
index 519733d..47d2164 100644
--- a/backend/pipeline/runner.py
+++ b/backend/pipeline/runner.py
@@ -33,6 +33,7 @@ from backend.pipeline.normalizer import normalize_assertions, build_project_inte
 from backend.pipeline.clusterer import cluster_by_location
 from backend.pipeline.llm_clusterer import cluster_by_location_llm
 from backend import config
+from backend.agents.disputes import annotate_clusters
 from backend.pipeline.conflict_checker import check_conflicts
 from backend.pipeline.qaqc_review import senior_review
 from backend.pipeline.code_review import code_review
@@ -129,6 +130,10 @@ def _run_stages(
     else:
         clusters = cluster_by_location(sheets)
 
+    disputed_count = annotate_clusters(clusters)
+    if disputed_count:
+        print(f"[Cluster] {disputed_count} cluster(s) carry disputed extracted values")
+
     stage("Reason over clusters (conflicts)")
     conflicts = check_conflicts(clusters, pages)
 
diff --git a/tests/agents/test_classic_constructability_disputes.py b/tests/agents/test_classic_constructability_disputes.py
new file mode 100644
index 0000000..6181e1c
--- /dev/null
+++ b/tests/agents/test_classic_constructability_disputes.py
@@ -0,0 +1,51 @@
+"""Classic pipeline path must also satisfy the {disputes} placeholder added to
+CONSTRUCTABILITY_USER_INSTRUCTION (agent path substitutes it in construct_agent.py;
+the classic stage builds its own subs dict)."""
+
+from unittest.mock import patch
+
+from backend.pipeline._stage import render
+from backend.pipeline.constructability import constructability_review
+from backend.prompts import CONSTRUCTABILITY_USER_INSTRUCTION
+
+
+def _cluster_with_dispute():
+    return {
+        "key": "c1",
+        "assertions": [],
+        "disputed_attributes": [{
+            "attribute": "stud_pack_size",
+            "values": ["(2) 2x6 STUD PACK", "(5) 2x6 STUD PACK"],
+            "assertion_ids": ["a1", "a2"],
+        }],
+    }
+
+
+def test_classic_constructability_supplies_disputes_sub():
+    captured = {}
+
+    def fake_call_stage(system_prompt, user_instruction, subs=None, **kwargs):
+        captured["subs"] = subs or {}
+        return {"issues": []}
+
+    with patch("backend.pipeline.constructability.call_stage", fake_call_stage):
+        constructability_review([], [_cluster_with_dispute()], [])
+
+    assert "disputes" in captured["subs"], "classic path must substitute {disputes}"
+    rendered = render(CONSTRUCTABILITY_USER_INSTRUCTION, captured["subs"])
+    assert "{disputes}" not in rendered
+    assert "(5) 2x6 STUD PACK" in rendered
+
+
+def test_classic_constructability_disputes_defaults_empty():
+    captured = {}
+
+    def fake_call_stage(system_prompt, user_instruction, subs=None, **kwargs):
+        captured["subs"] = subs or {}
+        return {"issues": []}
+
+    with patch("backend.pipeline.constructability.call_stage", fake_call_stage):
+        constructability_review([], [{"key": "c2", "assertions": []}], [])
+
+    rendered = render(CONSTRUCTABILITY_USER_INSTRUCTION, captured["subs"])
+    assert "{disputes}" not in rendered