plan(SP22): Task 5 — add test_parse_837_does_not_retry_on_5xx to spec (locks in dedup-safety contract)

docs/superpowers/plans/2026-06-21-cyclone-pipeline-agent.md

@@ -943,6 +943,19 @@ async def test_parse_837_posts_file_and_returns_summary(client, sample_837p_path
     # Confirm multipart upload
     content_type = route.calls.last.request.headers["content-type"]
     assert "multipart/form-data" in content_type
+
+
+@pytest.mark.asyncio
+@respx.mock
+async def test_parse_837_does_not_retry_on_5xx(client, sample_837p_path):
+    """parse_837 is a POST — retries would double-submit, so the
+    dedup-safety contract is that 5xx propagates without retry."""
+    route = respx.post("http://test:8000/api/parse-837").mock(
+        return_value=Response(503, json={"error": "transient"})
+    )
+    with pytest.raises(httpx.HTTPStatusError):
+        await client.parse_837(sample_837p_path, payer="co_medicaid")
+    assert route.call_count == 1
 ```
 
 - [ ] **Step 2: Run test to verify it fails**