diff --git a/tests/test_leftover_axis_report_singular_only_contract.py b/tests/test_leftover_axis_report_singular_only_contract.py
new file mode 100644
index 000000000..c02a27f3c
--- /dev/null
+++ b/tests/test_leftover_axis_report_singular_only_contract.py
@@ -0,0 +1,33 @@
+"""Executable contract for the report-axis singular-only state."""
+
+from pathlib import Path
+
+
+ROOT = Path(__file__).resolve().parents[1]
+BADGE_SOURCE = ROOT / "frontend" / "src" / "leftoverMapAxisBadge.ts"
+
+
+def test_report_axis_badge_preserves_singular_when_share_is_missing() -> None:
+    """A valid persisted σ remains visible when axis share is absent."""
+    assert BADGE_SOURCE.exists(), "report-axis singular-value badge helper is missing"
+    source = BADGE_SOURCE.read_text(encoding="utf-8")
+
+    assert (
+        'LEFTOVER_MAP_AXIS_BADGE_SINGULAR_ONLY = "leftover axis {axis} σ {value}"'
+        in source
+    )
+    assert "leftoverMapAxisBadge(" in source
+    assert "LEFTOVER_MAP_AXIS_BADGE_SINGULAR_ONLY" in source
+
+
+def test_report_axis_badge_keeps_sigma_and_share_missingness_independent() -> None:
+    """σ-only, share-only, combined, and empty states must remain data-driven."""
+    assert BADGE_SOURCE.exists(), "report-axis singular-value badge helper is missing"
+    source = BADGE_SOURCE.read_text(encoding="utf-8")
+
+    assert "formatLeftoverMapPlotAxisSingular" in source
+    assert "leftoverMapAxisBadgeShare" in source
+    assert "LEFTOVER_MAP_AXIS_BADGE_SINGULAR" in source
+    assert "LEFTOVER_MAP_AXIS_BADGE_SHARE" in source
+    assert "LEFTOVER_MAP_AXIS_BADGE_SINGULAR_ONLY" in source
+    assert "Math.sqrt" not in source