diff --git a/frontend/src/leftoverMapAxisBadge.ts b/frontend/src/leftoverMapAxisBadge.ts
index 84941caa9..8f1a44e87 100644
--- a/frontend/src/leftoverMapAxisBadge.ts
+++ b/frontend/src/leftoverMapAxisBadge.ts
@@ -16,6 +16,12 @@ export const LEFTOVER_MAP_AXIS_BADGE_SINGULAR_ONLY = "leftover axis {axis} σ {v
 export const LEFTOVER_MAP_AXIS_TICK_SINGULAR =
   "leftover axis {axis} tick {value} σ {singular}";
 
+export const LEFTOVER_MAP_AXIS_TICK_SHARE =
+  "leftover axis {axis} tick {value} {share}%";
+
+export const LEFTOVER_MAP_AXIS_TICK_SINGULAR_SHARE =
+  "leftover axis {axis} tick {value} σ {singular} {share}%";
+
 export type LeftoverMapAxisBadge = {
   template: string;
   values: Record<string, string | number>;
@@ -74,18 +80,32 @@ export function leftoverMapAxisBadge(
   };
 }
 
-/** Project finite persisted σ onto one report-axis tick without inventing share evidence. */
+/** Compose persisted report-axis tick σ/share without deriving either field. */
 export function leftoverMapAxisTickBadge(
   axisIndex: number,
   tickLabel: string,
   leftoverSingular: number | null | undefined,
+  leftoverShare?: LeftoverMapAxis["leftover_share"] | null,
 ): LeftoverMapAxisBadge | null {
   const singular = formatLeftoverMapPlotAxisSingular(leftoverSingular);
-  if (singular === null) {
+  const share = formatLeftoverMapPlotAxisShare(leftoverShare);
+  if (singular === null && share === null) {
     return null;
   }
+  if (singular === null) {
+    return {
+      template: LEFTOVER_MAP_AXIS_TICK_SHARE,
+      values: { axis: axisIndex, value: tickLabel, share: share as string },
+    };
+  }
+  if (share === null) {
+    return {
+      template: LEFTOVER_MAP_AXIS_TICK_SINGULAR,
+      values: { axis: axisIndex, value: tickLabel, singular },
+    };
+  }
   return {
-    template: LEFTOVER_MAP_AXIS_TICK_SINGULAR,
-    values: { axis: axisIndex, value: tickLabel, singular },
+    template: LEFTOVER_MAP_AXIS_TICK_SINGULAR_SHARE,
+    values: { axis: axisIndex, value: tickLabel, singular, share },
   };
 }
diff --git a/frontend/src/leftoverMapAxisTickBadge.test.ts b/frontend/src/leftoverMapAxisTickBadge.test.ts
new file mode 100644
index 000000000..b17e5a643
--- /dev/null
+++ b/frontend/src/leftoverMapAxisTickBadge.test.ts
@@ -0,0 +1,31 @@
+import { describe, expect, it } from "vitest";
+import {
+  LEFTOVER_MAP_AXIS_TICK_SHARE,
+  LEFTOVER_MAP_AXIS_TICK_SINGULAR,
+  LEFTOVER_MAP_AXIS_TICK_SINGULAR_SHARE,
+  leftoverMapAxisTickBadge,
+} from "./leftoverMapAxisBadge";
+
+describe("leftoverMapAxisTickBadge", () => {
+  it("keeps persisted singular and share evidence independently observable", () => {
+    expect(leftoverMapAxisTickBadge(1, "0.25", 0.5, 0.4)).toEqual({
+      template: LEFTOVER_MAP_AXIS_TICK_SINGULAR_SHARE,
+      values: { axis: 1, value: "0.25", singular: "0.50", share: "40" },
+    });
+    expect(leftoverMapAxisTickBadge(1, "0.00", 0, null)).toEqual({
+      template: LEFTOVER_MAP_AXIS_TICK_SINGULAR,
+      values: { axis: 1, value: "0.00", singular: "0.00" },
+    });
+    expect(leftoverMapAxisTickBadge(2, "−0.25", null, 0.4)).toEqual({
+      template: LEFTOVER_MAP_AXIS_TICK_SHARE,
+      values: { axis: 2, value: "−0.25", share: "40" },
+    });
+  });
+
+  it("fails closed when neither persisted evidence value is usable", () => {
+    expect(
+      leftoverMapAxisTickBadge(1, "0.25", Number.NaN, Number.POSITIVE_INFINITY),
+    ).toBeNull();
+    expect(leftoverMapAxisTickBadge(1, "0.25", null, undefined)).toBeNull();
+  });
+});
diff --git a/tests/test_leftover_axis_tick_share_contract.py b/tests/test_leftover_axis_tick_share_contract.py
new file mode 100644
index 000000000..f6ddcf8d7
--- /dev/null
+++ b/tests/test_leftover_axis_tick_share_contract.py
@@ -0,0 +1,40 @@
+"""Executable contract for report leftover-axis tick share captions."""
+
+from pathlib import Path
+
+
+ROOT = Path(__file__).resolve().parents[1]
+BADGE_SOURCE = ROOT / "frontend" / "src" / "leftoverMapAxisBadge.ts"
+BADGE_TEST_SOURCE = ROOT / "frontend" / "src" / "leftoverMapAxisTickBadge.test.ts"
+
+
+def test_report_axis_tick_keeps_axis_share_independent_of_singular() -> None:
+    """A report leftover-axis tick may name persisted share when singular evidence is absent."""
+    assert BADGE_SOURCE.exists(), "report-axis badge helper is missing"
+    source = BADGE_SOURCE.read_text(encoding="utf-8")
+
+    assert "leftoverMapAxisTickBadge" in source
+    assert "leftover axis {axis} tick {value} {share}%" in source
+    assert "leftover axis {axis} tick {value} σ {singular} {share}%" in source
+
+
+def test_report_axis_tick_never_infers_share_from_singular() -> None:
+    """Share is formatted from its persisted field rather than inferred from σ."""
+    assert BADGE_SOURCE.exists(), "report-axis badge helper is missing"
+    source = BADGE_SOURCE.read_text(encoding="utf-8")
+    tick_badge = source.split("export function leftoverMapAxisTickBadge", 1)[1]
+
+    assert "formatLeftoverMapPlotAxisShare(leftoverShare)" in tick_badge
+    assert "formatLeftoverMapPlotAxisSingular(leftoverSingular)" in tick_badge
+    assert "Math.sqrt(" not in tick_badge
+    assert "Math.max(" not in tick_badge
+
+
+def test_report_axis_tick_share_states_are_executable() -> None:
+    """Frontend tests execute combined, share-only, and invalid persisted-share states."""
+    assert BADGE_TEST_SOURCE.exists(), "report-axis tick badge behavior test is missing"
+    test_source = BADGE_TEST_SOURCE.read_text(encoding="utf-8")
+
+    assert 'leftoverMapAxisTickBadge(1, "0.25", 0.5, 0.4)' in test_source
+    assert 'leftoverMapAxisTickBadge(2, "−0.25", null, 0.4)' in test_source
+    assert "Number.POSITIVE_INFINITY" in test_source
diff --git a/tests/test_leftover_axis_tick_singular_contract.py b/tests/test_leftover_axis_tick_singular_contract.py
index e13c8f657..e806cb1d6 100644
--- a/tests/test_leftover_axis_tick_singular_contract.py
+++ b/tests/test_leftover_axis_tick_singular_contract.py
@@ -5,6 +5,7 @@
 
 ROOT = Path(__file__).resolve().parents[1]
 BADGE_SOURCE = ROOT / "frontend" / "src" / "leftoverMapAxisBadge.ts"
+BADGE_TEST_SOURCE = ROOT / "frontend" / "src" / "leftoverMapAxisTickBadge.test.ts"
 
 
 def test_report_leftover_axis_tick_keeps_persisted_singular_without_share() -> None:
@@ -17,11 +18,22 @@ def test_report_leftover_axis_tick_keeps_persisted_singular_without_share() -> N
 
 
 def test_report_leftover_axis_tick_never_infers_sigma_or_share() -> None:
-    """Invalid σ falls back to an ordinary leftover-axis tick; share is never synthesized."""
+    """Tick σ/share are delegated to their persisted-value formatters without derivation."""
     assert BADGE_SOURCE.exists(), "report-axis badge helper is missing"
     source = BADGE_SOURCE.read_text(encoding="utf-8")
+    tick_badge = source.split("export function leftoverMapAxisTickBadge", 1)[1]
 
-    assert "formatLeftoverMapPlotAxisSingular" in source
-    assert "Math.sqrt" not in source
-    tail = source.split("leftoverMapAxisTickBadge", 1)[-1][:1600]
-    assert "leftover_share" not in tail
+    assert "formatLeftoverMapPlotAxisSingular(leftoverSingular)" in tick_badge
+    assert "formatLeftoverMapPlotAxisShare(leftoverShare)" in tick_badge
+    assert "Math.sqrt(" not in tick_badge
+    assert "Math.max(" not in tick_badge
+
+
+def test_report_leftover_axis_tick_singular_states_are_executable() -> None:
+    """Frontend tests execute singular-only zero and fail-closed invalid evidence states."""
+    assert BADGE_TEST_SOURCE.exists(), "report-axis tick badge behavior test is missing"
+    test_source = BADGE_TEST_SOURCE.read_text(encoding="utf-8")
+
+    assert 'leftoverMapAxisTickBadge(1, "0.00", 0, null)' in test_source
+    assert 'singular: "0.00"' in test_source
+    assert "Number.NaN" in test_source