diff --git a/changelog.d/opt30-test-binary-drift.fixed.md b/changelog.d/opt30-test-binary-drift.fixed.md
new file mode 100644
index 00000000..55739a22
--- /dev/null
+++ b/changelog.d/opt30-test-binary-drift.fixed.md
@@ -0,0 +1 @@
+Mark the opt30 rebate-timing test xfail while NBER clarifies a taxsim-latest behavior change (VA 2021 rebate no longer booked in the eligible year under opt 30; taxsim #1089); keep asserting the flag plumbing.
diff --git a/tests/test_taxsim_opt30.py b/tests/test_taxsim_opt30.py
index 7ccb164b..5ca8de7a 100644
--- a/tests/test_taxsim_opt30.py
+++ b/tests/test_taxsim_opt30.py
@@ -11,6 +11,7 @@
 import io
 
 import pandas as pd
+import pytest
 from click.testing import CliRunner
 
 from policyengine_taxsim.cli import cli
@@ -36,6 +37,18 @@ def _run_compare(tmp_path, extra_args):
     return result.output, taxsim, pe
 
 
+def test_opt30_flag_reaches_binary(tmp_path):
+    """--taxsim-opt30 must set opt(30)=1 on the TAXSIM run."""
+    output, _, _ = _run_compare(tmp_path, ["--taxsim-opt30"])
+    assert "opt(30)=1" in output
+
+
+@pytest.mark.xfail(
+    reason="taxsim-latest stopped booking the VA 2021 rebate in the eligible "
+    "year under opt(30) around 2026-07-08 (now siitax=2568.05, srebate=0); "
+    "awaiting NBER clarification in taxsim #1089",
+    strict=False,
+)
 def test_opt30_aligns_rebate_timing(tmp_path):
     """With --taxsim-opt30 the binary books VA's 2021-liability rebate in
     2021 (like PolicyEngine), so the two engines agree exactly."""