diff --git a/eval/chat_benchmarks/GPQADiamond/eval_instruct.py b/eval/chat_benchmarks/GPQADiamond/eval_instruct.py
index dab52fd0..c413a1d1 100644
--- a/eval/chat_benchmarks/GPQADiamond/eval_instruct.py
+++ b/eval/chat_benchmarks/GPQADiamond/eval_instruct.py
@@ -1,3 +1,4 @@
+import hashlib
 import logging
 import os
 import random
@@ -177,7 +178,7 @@ def generate_multiple_choice_answers(self, data: Dict[str, Any]) -> tuple[str, s
             data["Incorrect Answer 2"],
             data["Incorrect Answer 3"],
         ]
-        rnd = random.Random(42)
+        rnd = random.Random(42 + int(hashlib.md5(data["Question"].encode()).hexdigest(), 16))
         rnd.shuffle(answers)
 
         options = ["A", "B", "C", "D"]
diff --git a/tests/gpqa/test_answer_shuffle.py b/tests/gpqa/test_answer_shuffle.py
new file mode 100644
index 00000000..1c65b27b
--- /dev/null
+++ b/tests/gpqa/test_answer_shuffle.py
@@ -0,0 +1,31 @@
+"""Regression tests for GPQA-Diamond answer placement."""
+
+import sys
+from pathlib import Path
+
+_REPO_ROOT = Path(__file__).resolve().parents[2]
+if str(_REPO_ROOT) not in sys.path:
+    sys.path.insert(0, str(_REPO_ROOT))
+
+from eval.chat_benchmarks.GPQADiamond.eval_instruct import GPQADiamondBenchmark
+
+
+def _question(index: int) -> dict[str, str]:
+    return {
+        "Question": f"Question {index}",
+        "Correct Answer": "correct",
+        "Incorrect Answer 1": "wrong one",
+        "Incorrect Answer 2": "wrong two",
+        "Incorrect Answer 3": "wrong three",
+    }
+
+
+def test_answer_positions_vary_reproducibly_across_questions():
+    benchmark = GPQADiamondBenchmark.__new__(GPQADiamondBenchmark)
+    questions = [_question(index) for index in range(32)]
+
+    first = [benchmark.generate_multiple_choice_answers(question)[1] for question in questions]
+    second = [benchmark.generate_multiple_choice_answers(question)[1] for question in questions]
+
+    assert set(first) == {"A", "B", "C", "D"}
+    assert first == second