diff --git a/benchmark/core/model_runner.py b/benchmark/core/model_runner.py
index 1bf54a9..96f8d30 100644
--- a/benchmark/core/model_runner.py
+++ b/benchmark/core/model_runner.py
@@ -931,7 +931,9 @@ def _retry_validation_prompt_suffix(output_contract: str) -> str:
             " Before returning, check every leaf: full credit requires "
             "deduction_trace=null; every non-full score requires a non-empty "
             "deduction_trace whose points_deducted values sum exactly to "
-            "max_score minus score."
+            "max_score minus score. For an execution-contract rubric, use only "
+            "declared criterion IDs and copy their atomic point values exactly; "
+            "do not split or rescale points to force a total."
         )
     return suffix
 
@@ -966,7 +968,11 @@ def _execution_contract_prompt_note(rubric: dict[str, Any] | None) -> str:
         "\nExecution-contract rule: score only the declared criteria. Ignore "
         "unrelated extra content unless it directly contradicts a declared "
         "criterion. For every deduction_trace, rubric_criterion must be the "
-        "exact applicable criterion ID from this rubric."
+        "exact applicable criterion ID from this rubric. Criterion points are "
+        "atomic: copy each selected criterion's declared points exactly; never "
+        "split, rescale, or invent a deduction amount just to make a trace add "
+        "up. Select a score only when max_score minus score equals the exact "
+        "sum of the withheld declared criteria."
     )
 
 
diff --git a/tests/benchmark/core/test_model_runner.py b/tests/benchmark/core/test_model_runner.py
index d19bd82..ea0f5ac 100644
--- a/tests/benchmark/core/test_model_runner.py
+++ b/tests/benchmark/core/test_model_runner.py
@@ -179,8 +179,28 @@ def test_deduction_trace_retry_feedback_repeats_exact_deduction_invariant(self):
 
         self.assertIn("deduction_trace=null", suffix)
         self.assertIn("sum exactly to max_score minus score", suffix)
+        self.assertIn("copy their atomic point values exactly", suffix)
         self.assertNotIn("student_id", suffix)
 
+    def test_execution_contract_prompt_requires_atomic_trace_bookkeeping(self):
+        course = CourseSpec.from_dict(
+            json.loads((FIXTURES / "course_dsaa3073_hw1.json").read_text(encoding="utf-8"))
+        )
+
+        prompt = _compose_student_prompt(
+            "Return JSON.",
+            "S001",
+            course,
+            rubric={"rubric_format": "execution_contract_v1"},
+            inputs=[],
+            task="grade",
+            output_contract=GRADING_OUTPUT_CONTRACT_DEDUCTION_TRACE_V1,
+        )
+
+        self.assertIn("Criterion points are atomic", prompt)
+        self.assertIn("never split, rescale, or invent a deduction amount", prompt)
+        self.assertIn("exact sum of the withheld declared criteria", prompt)
+
     def test_multimodal_prompt_repeats_page_locator_rule(self):
         course = CourseSpec.from_dict(
             json.loads((FIXTURES / "course_dsaa3073_hw1.json").read_text(encoding="utf-8"))