Extract shared BackLink and adopt on detail pages

The workout, values, score, and medication detail pages each hand-rolled
the same ghost Button + Link + ArrowLeft back-nav block. Fold it into a
single BackLink (href + label + optional data-slot) so the affordance
reads identically — same hit area, icon, and left-bleed alignment — on
every page and lives in one place. Each page passes its existing label
translation, so no new i18n keys are introduced and the markup stays
byte-identical.

src/app/insights/scores/[metric]/page.tsx

@@ -1,11 +1,9 @@
 "use client";
 
-import Link from "next/link";
 import { useParams } from "next/navigation";
-import { ArrowLeft } from "lucide-react";
 
 import { useTranslations } from "@/lib/i18n/context";
-import { Button } from "@/components/ui/button";
+import { BackLink } from "@/components/ui/back-link";
 import { SubPageShell } from "@/components/insights/sub-page-shell";
 import {
   CompositeScoreAnatomy,
@@ -88,18 +86,11 @@ export default function CompositeScorePage() {
       description={t(header.description)}
       explainerMetric={EXPLAINER_METRIC[metric]}
       backLink={
-        <Button
-          asChild
-          variant="ghost"
-          size="sm"
-          data-slot="composite-score-back"
-          className="-ml-2 w-fit"
-        >
-          <Link href="/insights">
-            <ArrowLeft className="size-4" aria-hidden="true" />
-            {t("insights.subPage.scoresBack")}
-          </Link>
-        </Button>
+        <BackLink
+          href="/insights"
+          label={t("insights.subPage.scoresBack")}
+          dataSlot="composite-score-back"
+        />
       }
       coachLaunch
     >

src/app/insights/values/[type]/page.tsx

@@ -1,9 +1,7 @@
 "use client";
 
 import { use } from "react";
-import Link from "next/link";
 import { notFound, useSearchParams } from "next/navigation";
-import { ArrowLeft } from "lucide-react";
 
 import { useTranslations } from "@/lib/i18n/context";
 import {
@@ -12,7 +10,7 @@ import {
 } from "@/lib/insights/values-back-link";
 import { measurementTypeEnum } from "@/lib/validations/measurement";
 import { MEASUREMENT_TYPE_LABEL_KEYS } from "@/components/measurements/measurement-list-meta";
-import { Button } from "@/components/ui/button";
+import { BackLink } from "@/components/ui/back-link";
 import { MeasurementList } from "@/components/measurements/measurement-list";
 import { SubPageShell } from "@/components/insights/sub-page-shell";
 
@@ -63,22 +61,17 @@ export default function InsightsMetricValuesPage({
       title={t("insights.subPage.valuesPageTitle", { metric: metricLabel })}
       description={t("insights.subPage.valuesPageDescription")}
       backLink={
-        <Button
-          asChild
-          variant="ghost"
-          size="sm"
-          data-slot="metric-values-back"
-          className="-ml-2 w-fit"
-        >
-          <Link href={backHref}>
-            <ArrowLeft className="size-4" aria-hidden="true" />
-            {backToOrigin
+        <BackLink
+          href={backHref}
+          label={
+            backToOrigin
               ? t("insights.subPage.valuesBackToMetric", {
                   metric: metricLabel,
                 })
-              : t("insights.subPage.valuesBack")}
-          </Link>
-        </Button>
+              : t("insights.subPage.valuesBack")
+          }
+          dataSlot="metric-values-back"
+        />
       }
     >
       <MeasurementList lockedType={type} />

src/app/insights/workouts/[id]/page.tsx

@@ -1,12 +1,10 @@
 "use client";
 
 import { use } from "react";
-import Link from "next/link";
-import { ArrowLeft } from "lucide-react";
 
 import { useTranslations } from "@/lib/i18n/context";
 import { useWorkoutDetail } from "@/hooks/use-workouts";
-import { Button } from "@/components/ui/button";
+import { BackLink } from "@/components/ui/back-link";
 import { CoachLaunchButton } from "@/components/insights/coach-launch-button";
 import { SubPageShell } from "@/components/insights/sub-page-shell";
 import { Skeleton } from "@/components/ui/skeleton";
@@ -41,18 +39,11 @@ export default function InsightsWorkoutDetailPage({
       title={t("insights.workouts.title")}
       description={t("insights.workouts.description")}
       backLink={
-        <Button
-          asChild
-          variant="ghost"
-          size="sm"
-          data-slot="workout-detail-back"
-          className="-ml-2 w-fit"
-        >
-          <Link href="/insights/workouts">
-            <ArrowLeft className="size-4" aria-hidden="true" />
-            {t("insights.workouts.detail.backToList")}
-          </Link>
-        </Button>
+        <BackLink
+          href="/insights/workouts"
+          label={t("insights.workouts.detail.backToList")}
+          dataSlot="workout-detail-back"
+        />
       }
     >
       {isLoading ? (

src/app/medications/[id]/page.tsx

@@ -13,16 +13,15 @@
  */
 
 import { use, useEffect } from "react";
-import Link from "next/link";
 import { useQuery } from "@tanstack/react-query";
 import { useRouter } from "next/navigation";
-import { ArrowLeft, Loader2 } from "lucide-react";
+import { Loader2 } from "lucide-react";
 
 import { useAuth } from "@/hooks/use-auth";
 import { useTranslations } from "@/lib/i18n/context";
 import { queryKeys } from "@/lib/query-keys";
 
-import { Button } from "@/components/ui/button";
+import { BackLink } from "@/components/ui/back-link";
 import { Card } from "@/components/ui/card";
 import {
   MedicationDetailTabs,
@@ -87,12 +86,7 @@ export default function MedicationDetailPage({
   if (isError || !medication) {
     return (
       <div className="space-y-6">
-        <Button variant="ghost" size="sm" className="-ml-2 w-fit" asChild>
-          <Link href="/medications">
-            <ArrowLeft className="size-4" aria-hidden="true" />
-            {t("medications.back")}
-          </Link>
-        </Button>
+        <BackLink href="/medications" label={t("medications.back")} />
         <Card
           className="p-6"
           role="alert"

src/components/ui/__tests__/back-link.test.tsx

@@ -0,0 +1,38 @@
+import { describe, expect, it } from "vitest";
+import { renderToStaticMarkup } from "react-dom/server";
+
+import { BackLink } from "../back-link";
+
+describe("<BackLink>", () => {
+  it("renders an anchor to the href carrying the label", () => {
+    const html = renderToStaticMarkup(
+      <BackLink href="/insights/workouts" label="Back to workouts" />,
+    );
+    expect(html).toContain('href="/insights/workouts"');
+    expect(html).toContain("Back to workouts");
+    // The decorative chevron is hidden from screen readers; the label
+    // carries the meaning.
+    expect(html).toContain('aria-hidden="true"');
+  });
+
+  it("keeps the shared left-bleed alignment on the control", () => {
+    const html = renderToStaticMarkup(
+      <BackLink href="/medications" label="Back" />,
+    );
+    // The `-ml-2 w-fit` left-bleed is the standard back-nav placement; it
+    // must survive on every adopting page.
+    expect(html).toContain("-ml-2");
+    expect(html).toContain("w-fit");
+  });
+
+  it("threads the optional data-slot for e2e/visual targeting", () => {
+    const html = renderToStaticMarkup(
+      <BackLink
+        href="/insights"
+        label="Back"
+        dataSlot="composite-score-back"
+      />,
+    );
+    expect(html).toContain('data-slot="composite-score-back"');
+  });
+});

src/components/ui/back-link.tsx

@@ -0,0 +1,47 @@
+import Link from "next/link";
+import { ArrowLeft } from "lucide-react";
+
+import { Button } from "@/components/ui/button";
+import { cn } from "@/lib/utils";
+
+/**
+ * v1.16.16 — shared back-navigation control.
+ *
+ * The detail / sub-page surfaces (`/insights/workouts/[id]`,
+ * `/insights/values/[type]`, `/insights/scores/[metric]`,
+ * `/medications/[id]`) each hand-rolled the identical
+ * `Button(ghost, sm, -ml-2 w-fit) > Link > ArrowLeft + label` block. This
+ * folds that into one component so the back-nav reads the same — same hit
+ * area, same icon, same left-bleed alignment — on every page, and a future
+ * change to the affordance lives in one place.
+ *
+ * The label travels in from the caller (each page already owns its own
+ * translation key, e.g. `insights.workouts.detail.backToList`), so this
+ * component adds no new i18n surface.
+ */
+export interface BackLinkProps {
+  /** Internal href the back-nav points at. */
+  href: string;
+  /** Already-translated label text. */
+  label: string;
+  /** Optional per-surface `data-slot` for e2e/visual targeting. */
+  dataSlot?: string;
+  className?: string;
+}
+
+export function BackLink({ href, label, dataSlot, className }: BackLinkProps) {
+  return (
+    <Button
+      asChild
+      variant="ghost"
+      size="sm"
+      data-slot={dataSlot}
+      className={cn("-ml-2 w-fit", className)}
+    >
+      <Link href={href}>
+        <ArrowLeft className="size-4" aria-hidden="true" />
+        {label}
+      </Link>
+    </Button>
+  );
+}