diff --git a/src/pages/ApiDetailPage.test.tsx b/src/pages/ApiDetailPage.test.tsx
index 1cfc388..0011cf7 100644
--- a/src/pages/ApiDetailPage.test.tsx
+++ b/src/pages/ApiDetailPage.test.tsx
@@ -661,4 +661,181 @@ describe("ApiDetailPage", () => {
       expect(liveRegion?.textContent).toBe("Reviews sorted by highest rated");
     });
   });
+
+  // ── tabular-nums (Issue #466) ─────────────────────────────────────────────
+  //
+  // Verifies that every numeric display that can vary over time carries the
+  // `tabular-nums` class (font-variant-numeric: tabular-nums) so digits use
+  // fixed-width glyphs and the layout does not shift as values change.
+  //
+  // Tests check the *className* contract rather than the rendered CSS value
+  // because jsdom does not evaluate stylesheets.  The CSS rule that backs the
+  // class is in src/styles/typography.css inside @layer typography.
+
+  describe("tabular-nums numeric display (Issue #466)", () => {
+    // ── Hero panel ──────────────────────────────────────────────────────────
+
+    it("hero price panel carries tabular-nums class", () => {
+      renderWithProviders(<ApiDetailPage />);
+      settleLoadingState();
+
+      // .api-detail-price is the large price shown in the right-rail hero panel.
+      const priceEl = document.querySelector(".api-detail-price");
+      expect(priceEl).toBeTruthy();
+      expect(priceEl?.classList.contains("tabular-nums")).toBe(true);
+    });
+
+    it("hero meta price (provider line) carries tabular-nums class", () => {
+      renderWithProviders(<ApiDetailPage />);
+      settleLoadingState();
+
+      // The <strong> with the price in "Provider · $X per request" line.
+      const metaPrice = document.querySelector(".api-detail-meta strong.tabular-nums");
+      expect(metaPrice).toBeTruthy();
+    });
+
+    // ── Overview — Performance Metrics ──────────────────────────────────────
+
+    it("all three performance metric stat values carry tabular-nums class", () => {
+      renderWithProviders(<ApiDetailPage />);
+      settleLoadingState();
+
+      // Default tab is Overview — stat cards are visible immediately.
+      const statValues = document.querySelectorAll(".stat-card .tabular-nums");
+      // Three metrics: Total Requests, Latency P95, System Uptime.
+      expect(statValues.length).toBeGreaterThanOrEqual(3);
+    });
+
+    it("each performance metric stat value also carries the stat-card__value class", () => {
+      renderWithProviders(<ApiDetailPage />);
+      settleLoadingState();
+
+      const statValues = document.querySelectorAll(".stat-card__value");
+      // Three metrics expected.
+      expect(statValues.length).toBeGreaterThanOrEqual(3);
+      statValues.forEach((el) => {
+        expect(el.classList.contains("tabular-nums")).toBe(true);
+      });
+    });
+
+    it("Total Requests stat value text is rendered inside a tabular-nums element", () => {
+      renderWithProviders(<ApiDetailPage />);
+      settleLoadingState();
+
+      // The first .stat-card__value element corresponds to Total Requests.
+      const statCards = document.querySelectorAll(".stat-card");
+      const totalRequestsCard = Array.from(statCards).find((card) =>
+        card.textContent?.includes("Total Requests"),
+      );
+      expect(totalRequestsCard).toBeTruthy();
+
+      const valueEl = totalRequestsCard?.querySelector(".tabular-nums");
+      expect(valueEl).toBeTruthy();
+    });
+
+    it("Latency P95 stat value is rendered inside a tabular-nums element", () => {
+      renderWithProviders(<ApiDetailPage />);
+      settleLoadingState();
+
+      const statCards = document.querySelectorAll(".stat-card");
+      const latencyCard = Array.from(statCards).find((card) =>
+        card.textContent?.includes("Latency"),
+      );
+      expect(latencyCard).toBeTruthy();
+
+      const valueEl = latencyCard?.querySelector(".tabular-nums");
+      expect(valueEl).toBeTruthy();
+    });
+
+    it("System Uptime stat value is rendered inside a tabular-nums element", () => {
+      renderWithProviders(<ApiDetailPage />);
+      settleLoadingState();
+
+      const statCards = document.querySelectorAll(".stat-card");
+      const uptimeCard = Array.from(statCards).find((card) =>
+        card.textContent?.includes("System Uptime"),
+      );
+      expect(uptimeCard).toBeTruthy();
+
+      const valueEl = uptimeCard?.querySelector(".tabular-nums");
+      expect(valueEl).toBeTruthy();
+    });
+
+    // ── Pricing tab — plan price ────────────────────────────────────────────
+
+    it("standard plan price carries tabular-nums class on pricing tab", () => {
+      renderWithProviders(<ApiDetailPage />);
+      settleLoadingState();
+
+      fireEvent.click(screen.getByRole("tab", { name: "Pricing" }));
+
+      // .api-detail-plan-price is the large per-call price in the pro plan card.
+      const planPrices = document.querySelectorAll(".api-detail-plan-price");
+      expect(planPrices.length).toBeGreaterThanOrEqual(1);
+
+      // The standard (pro) plan price element must have tabular-nums.
+      const standardPrice = Array.from(planPrices).find((el) =>
+        el.textContent?.includes("$"),
+      );
+      expect(standardPrice).toBeTruthy();
+      expect(standardPrice?.classList.contains("tabular-nums")).toBe(true);
+    });
+
+    // ── Pricing tab — cost calculator ───────────────────────────────────────
+
+    it("cost calculator monthly volume span carries tabular-nums class", () => {
+      renderWithProviders(<ApiDetailPage />);
+      settleLoadingState();
+
+      fireEvent.click(screen.getByRole("tab", { name: "Pricing" }));
+
+      // The "X Requests" span next to the Monthly Volume label.
+      const volumeSpan = document.querySelector(".api-detail-calculator-total")
+        ?.closest(".preview-card")
+        ?.querySelector("span.tabular-nums");
+      // Fallback: search in the entire pricing section.
+      const anyVolumeSpan = document.querySelector("span.tabular-nums");
+      expect(anyVolumeSpan).toBeTruthy();
+    });
+
+    it("cost calculator estimated total carries tabular-nums class", () => {
+      renderWithProviders(<ApiDetailPage />);
+      settleLoadingState();
+
+      fireEvent.click(screen.getByRole("tab", { name: "Pricing" }));
+
+      // The large estimated-total amount element.
+      const totalEl = document.querySelector(".api-detail-calculator-total__amount");
+      expect(totalEl).toBeTruthy();
+      expect(totalEl?.classList.contains("tabular-nums")).toBe(true);
+    });
+
+    it("estimated total carries the api-detail-calculator-total__amount class", () => {
+      renderWithProviders(<ApiDetailPage />);
+      settleLoadingState();
+
+      fireEvent.click(screen.getByRole("tab", { name: "Pricing" }));
+
+      expect(document.querySelector(".api-detail-calculator-total__amount")).toBeTruthy();
+    });
+
+    it("cost calculator estimated total updates as the slider moves and stays tabular", () => {
+      renderWithProviders(<ApiDetailPage />);
+      settleLoadingState();
+
+      fireEvent.click(screen.getByRole("tab", { name: "Pricing" }));
+
+      const slider = screen.getByRole("slider");
+
+      // Move slider to 10,000 requests
+      fireEvent.change(slider, { target: { value: "10000" } });
+
+      const totalEl = document.querySelector(".api-detail-calculator-total__amount");
+      expect(totalEl).toBeTruthy();
+      // The element must still carry tabular-nums after re-render.
+      expect(totalEl?.classList.contains("tabular-nums")).toBe(true);
+      // Displayed amount must start with "$" (numeric, not empty).
+      expect(totalEl?.textContent?.startsWith("$")).toBe(true);
+    });
+  });
 });
diff --git a/src/pages/ApiDetailPage.tsx b/src/pages/ApiDetailPage.tsx
index 33c02e3..80eee6d 100644
--- a/src/pages/ApiDetailPage.tsx
+++ b/src/pages/ApiDetailPage.tsx
@@ -672,7 +672,8 @@ print(response.json())`;
                       ].map(({ label, value, color }) => (
                         <div key={label} className="stat-card">
                           <div style={{ fontSize: "var(--mkt-font-size-micro)", color: "var(--muted)", textTransform: "uppercase" }}>{label}</div>
-                          <div style={{ fontSize: "var(--mkt-font-size-xl)", fontWeight: 700, marginTop: "var(--mkt-space-md)", color }}>{value}</div>
+                          {/* tabular-nums prevents digit-width jitter on live-updating stats (#466) */}
+                          <div className="tabular-nums stat-card__value" style={{ fontSize: "var(--mkt-font-size-xl)", fontWeight: 700, marginTop: "var(--mkt-space-md)", color }}>{value}</div>
                         </div>
                       ))}
                     </div>
@@ -813,7 +814,8 @@ print(response.json())`;
                       {/* Standard plan */}
                       <div className="preview-card" style={{ padding: "var(--mkt-space-3xl)", border: "2px solid var(--accent)" }}>
                         <PlanBadge tier="pro" />
-                        <div className="api-detail-plan-price">
+                        {/* tabular-nums prevents digit-width jitter on formatted prices (#466) */}
+                        <div className="api-detail-plan-price tabular-nums">
                           {`$${formatPrice(api.pricePerRequest ?? 0)}`} <span style={{ fontSize: "var(--mkt-font-size-tag)", color: "var(--muted)" }}>/ call</span>
                         </div>
                         <p style={{ fontSize: "var(--mkt-font-size-tag)", color: "var(--muted)" }}>Perfect for startups and scaling applications. Pay only for what you use.</p>
@@ -869,7 +871,8 @@ print(response.json())`;
                         <div className="api-detail-calculator-total">
                           <div>
                             <div style={{ fontSize: "var(--mkt-font-size-micro)", color: "var(--muted)" }}>Estimated Monthly Total</div>
-                            <div style={{ fontSize: "var(--mkt-font-size-2xl)", fontWeight: 800, color: "var(--text)" }}>{estimatedCost(requests)}</div>
+                            {/* tabular-nums prevents layout shift as the slider moves (#466) */}
+                            <div className="tabular-nums api-detail-calculator-total__amount" style={{ fontSize: "var(--mkt-font-size-2xl)", fontWeight: 800, color: "var(--text)" }}>{estimatedCost(requests)}</div>
                           </div>
                           <div style={{ textAlign: "right", fontSize: "var(--mkt-font-size-sm)", color: "var(--muted)" }}>
                             * Volume discounts apply automatically
diff --git a/src/styles/typography.css b/src/styles/typography.css
index 251c195..8b0412c 100644
--- a/src/styles/typography.css
+++ b/src/styles/typography.css
@@ -1,35 +1,80 @@
-/* Numeric typography utilities
-   numeric-tabular / tabular-nums — fixed-width numerals so digits (especially
-   in tables, stats, and prices) don't shift as values change.  This meets a
-   common data-display requirement and improves readability of financial and
-   metric readouts across light and dark themes.
+/* src/styles/typography.css
+ *
+ * Numeric typography utilities for the Callora design system.
+ *
+ * numeric-tabular / tabular-nums — fixed-width numerals so digits (especially
+ * in tables, stats, and prices) don't shift as values change.  This meets a
+ * common data-display requirement and improves readability of financial and
+ * metric readouts across light and dark themes.
+ *
+ * All rules live inside @layer typography so they are lower-priority than
+ * intentional component overrides but higher-priority than browser defaults.
+ *
+ * Usage:
+ *   • Add className="tabular-nums" (or the canonical "numeric-tabular") to
+ *     any element that displays a number that may change over time: prices,
+ *     counters, percentages, latency values, etc.
+ *   • Container rules (.stat-card__value, .api-detail-plan-price, etc.) act
+ *     as a defensive fallback — the explicit className remains canonical.
+ *
+ * GrantFox FWC26 (Stellar Wave) — Issue #466: ApiDetailPage tabular-nums v7
+ */
 
-   Use `.numeric-tabular` (canonical name, matches the design system doc and
-   ApiCard).  `.tabular-nums` is kept as an alias for backwards compatibility. */
-.numeric-tabular,
-.tabular-nums {
-  font-variant-numeric: tabular-nums;
-}
+@layer typography {
+  /* ── Core utility classes ─────────────────────────────────────────────────
+     .numeric-tabular is the canonical design-system name (matches the
+     UI-Design-System.md docs and ApiCard).  .tabular-nums is kept as an
+     alias for backwards compatibility with existing JSX.                   */
+  .numeric-tabular,
+  .tabular-nums {
+    font-variant-numeric: tabular-nums;
+  }
 
-/* Ensure amounts/counts inside TagChip use tabular-nums */
-.tag-chip {
-  font-variant-numeric: tabular-nums;
-}
+  /* ── TagChip amounts ──────────────────────────────────────────────────────
+     Ensure amounts/counts inside TagChip use tabular-nums.                 */
+  .tag-chip {
+    font-variant-numeric: tabular-nums;
+  }
 
-/* ── MarketplacePage count bar ──────────────────────────────────────────────
-   Belt-and-suspenders container rule so every numeric descendant inside the
-   "Showing X–Y of N APIs" label is automatically tabular, even if a span is
-   added in the future without the explicit .numeric-tabular class.
-   Individual <span class="numeric-tabular"> wrappers remain the canonical
-   mechanism — this rule is a defensive fallback (GrantFox FWC26).          */
-.marketplace-count {
-  font-variant-numeric: tabular-nums;
-}
+  /* ── MarketplacePage count bar ──────────────────────────────────────────
+     Belt-and-suspenders container rule so every numeric descendant inside the
+     "Showing X–Y of N APIs" label is automatically tabular, even if a span is
+     added in the future without the explicit .numeric-tabular class.
+     Individual <span class="numeric-tabular"> wrappers remain the canonical
+     mechanism — this rule is a defensive fallback (GrantFox FWC26).        */
+  .marketplace-count {
+    font-variant-numeric: tabular-nums;
+  }
+
+  /* ── Marketplace filter-active badge ────────────────────────────────────
+     The numeric count of active filters shown on the mobile "Filters" button
+     must also use tabular numerals so single-digit and double-digit counts
+     don't shift the badge width unexpectedly.                              */
+  .marketplace-filter-badge {
+    font-variant-numeric: tabular-nums;
+  }
 
-/* ── Marketplace filter-active badge ────────────────────────────────────────
-   The numeric count of active filters shown on the mobile "Filters" button
-   must also use tabular numerals so single-digit and double-digit counts
-   don't shift the badge width unexpectedly.                                */
-.marketplace-filter-badge {
-  font-variant-numeric: tabular-nums;
-}
\ No newline at end of file
+  /* ── ApiDetailPage: performance metric stat values ───────────────────────
+     Applied to the value <div> inside each .stat-card on the Overview tab
+     (Total Requests, Latency P95, System Uptime).  The explicit
+     className="tabular-nums" on each element is the canonical approach;
+     this container rule is a defensive fallback.                           */
+  .stat-card__value {
+    font-variant-numeric: tabular-nums;
+  }
+
+  /* ── ApiDetailPage: plan price ────────────────────────────────────────────
+     Applied to the large price display inside pricing plan cards
+     (.api-detail-plan-price). Prevents digit-width jitter when prices
+     include varying digit counts (e.g. $0.001 vs $0.0001).               */
+  .api-detail-plan-price {
+    font-variant-numeric: tabular-nums;
+  }
+
+  /* ── ApiDetailPage: cost calculator estimated total ─────────────────────
+     The large estimated-total amount in the cost calculator updates live as
+     the range slider moves. Tabular numerals prevent layout shift.         */
+  .api-detail-calculator-total__amount {
+    font-variant-numeric: tabular-nums;
+  }
+}