diff --git a/frontend/src/v2/__tests__/v2-layout-invariants.test.ts b/frontend/src/v2/__tests__/v2-layout-invariants.test.ts
index 5214c436c..76cac0e42 100644
--- a/frontend/src/v2/__tests__/v2-layout-invariants.test.ts
+++ b/frontend/src/v2/__tests__/v2-layout-invariants.test.ts
@@ -334,7 +334,14 @@ describe('v2 layout invariants (CSS rule presence)', () => {
     const brand = ruleBody(v2, '.v2-rail__brand-icon');
     const item = ruleBody(v2, '.v2-root button.v2-rail__item');
     const active = ruleBody(v2, '.v2-root button.v2-rail__item--active');
-    expect(rail).toContain('padding: 6px 10px');
+    expect(rail).toContain('padding: 6px 8px');
+    // The nav glyph must fit the rail's content box or the nav scrolls
+    // sideways (staging smoke, "rail no h-scroll @1440px"): rail width, less
+    // the pane's 1px border, less both side paddings.
+    const railW = Number(/--v2-rail-w:\s*(\d+)px/.exec(v2)?.[1]);
+    const padX = Number(/padding: \d+px (\d+)px/.exec(rail)?.[1]);
+    const itemW = Number(/(?:^|\s)width: (\d+)px/.exec(item)?.[1]);
+    expect(railW - 1 - 2 * padX).toBeGreaterThanOrEqual(itemW);
     expect(brand).toContain('width: 36px');
     expect(brand).toContain('height: 36px');
     expect(item).toContain('width: 38px');
@@ -458,6 +465,20 @@ describe('v2 layout invariants (CSS rule presence)', () => {
 
   test('phone tab labels keep text contrast while the glyphs take the artboard grey (D223)', () => {
     expect(v2).toContain('.v2-root button.v2-mobile-tabs__item:not(.v2-mobile-tabs__item--active) .v2-mobile-tabs__label { color: var(--v2-text-muted); }');
+    // The glyph half: inactive tabs take the artboard's placeholder grey.
+    const phone = blockContaining(v2, '@media (max-width: 760px)', '.v2-mobile-tabs__label {');
+    // Icons are controls, so they take the rail's 3:1 grey, not the artboard's placeholder.
+    expect(ruleBody(v2, '.v2-root button.v2-mobile-tabs__item', { within: phone })).toContain('color: var(--v2-rail-icon)');
+    // D223 ruling: the artboard's sans family at the 12px sans floor.
+    expect(ruleBody(v2, '.v2-mobile-tabs__label', { within: phone })).toContain('font: 500 12px/14px var(--v2-font)');
+  });
+
+  test('rail glyphs at rest are the nearest grey to the artboard that clears 3:1 (D223 ruling)', () => {
+    // Measured on the rail's own surface, --v2-shell-bg #eef0f4: the
+    // artboard's #98a2b3 is 2.26:1 and #828a99 is 3.05:1.
+    expect(v2).toContain('--v2-shell-bg: #eef0f4;');
+    expect(v2).toContain('--v2-rail-icon: #828a99;');
+    expect(v2.match(/--v2-rail-icon: #5f6979;/g) || []).toHaveLength(2);
   });
 
   test('the phone pods page leads with the artboard title bar, search behind an icon (D223)', () => {
diff --git a/frontend/src/v2/v2.css b/frontend/src/v2/v2.css
index 687c308d1..d0c0d9192 100644
--- a/frontend/src/v2/v2.css
+++ b/frontend/src/v2/v2.css
@@ -32,7 +32,11 @@ body.modern-ui.v2-canvas {
   /* TASK-701: inactive rail glyphs, join-radio outlines (3:1 on white and
      #f2f4f7) and the neutral selected pod row. Dark values sit in both dark
      sets below. */
-  --v2-rail-icon: #374151;
+  /* D223 ruling (Cofounder, 11-01): the artboard's --ph (#98a2b3) is under
+     3:1 on the rail's own surface, --v2-shell-bg #eef0f4 (2.26:1), so this is
+     the nearest grey that passes there: 3.05:1, and 3.47:1 on the white tab
+     bar. Dark #5f6979 is 3.48:1 on the dark shell and 3.17:1 on its surface. */
+  --v2-rail-icon: #828a99;
   --v2-control-outline: #667085;
   /* D223 (TASK-735): the artboard's .pod.on in both themes, a neutral tint
      row whose mark alone turns cobalt. */
@@ -273,7 +277,7 @@ body.modern-ui.v2-canvas {
     --v2-status-blocked-edge: #f97066;
     --v2-text-primary: #e8ebf1;
     --v2-message-text: #e8ebf1;
-    --v2-rail-icon: #aeb6c4;
+    --v2-rail-icon: #5f6979;
     --v2-control-outline: #737e92;
     --v2-row-active: #1e2531;
     --v2-row-active-text: #e8ebf1;
@@ -347,7 +351,7 @@ body.modern-ui.v2-canvas {
       --v2-status-blocked-edge: #f97066;
       --v2-text-primary: #e8ebf1;
       --v2-message-text: #e8ebf1;
-      --v2-rail-icon: #aeb6c4;
+      --v2-rail-icon: #5f6979;
       --v2-control-outline: #737e92;
       --v2-row-active: #1e2531;
       --v2-row-active-text: #e8ebf1;
@@ -803,7 +807,10 @@ body.modern-ui.v2-canvas {
 
 .v2-rail {
   height: 100%;
-  padding: 6px 10px;
+  /* 56px rail - 1px pane border - 2 x 8px = 39px, room for the 38px nav glyph.
+     At 10px the nav was 35px wide and scrolled sideways by 2px, which the
+     staging smoke's "rail no h-scroll @1440px" check caught after #3139. */
+  padding: 6px 8px;
   display: flex;
   flex-direction: column;
   gap: 8px;
@@ -892,8 +899,9 @@ body.modern-ui.v2-canvas {
   align-items: center;
   justify-content: center;
   gap: 0;
-  /* D223 (TASK-735): the artboard's .nav, a bare 38px glyph at rest. The
-     glyph colour stays the TASK-701 token, so dark keeps its lift. */
+  /* D223 (TASK-735): the artboard's .nav, a bare 38px glyph at rest, coloured
+     by --v2-rail-icon: the nearest grey to the artboard's that clears 3:1 on
+     the shell (values and ratios at the token). */
   width: 38px;
   min-height: 38px;
   height: 38px;
@@ -12798,7 +12806,9 @@ body.modern-ui.v2-canvas {
     gap: 3px;
     padding: 0 6px;
     background: transparent;
-    color: var(--v2-text-placeholder);
+    /* Icons are controls: the rail's 3:1 grey, not the artboard's 2.58:1
+       placeholder (D223 standing rule, 11-01). The label sets its own colour. */
+    color: var(--v2-rail-icon);
   }
 
   .v2-root button.v2-mobile-tabs__item--active,
@@ -12816,8 +12826,10 @@ body.modern-ui.v2-canvas {
 
   .v2-root button.v2-mobile-tabs__item--active .v2-mobile-tabs__icon { color: var(--v2-ink); }
 
+  /* D223 ruling (Cofounder, 11-01): the artboard's sans family, at the
+     12px sans floor rather than its 10px. */
   .v2-mobile-tabs__label {
-    font: 500 11px/12px var(--v2-font-mono);
+    font: 500 12px/14px var(--v2-font);
     white-space: nowrap;
   }