diff --git a/messages/de.json b/messages/de.json
index d7655e6fd..951aa164c 100644
--- a/messages/de.json
+++ b/messages/de.json
@@ -2860,6 +2860,13 @@
       "scoresBack": "Zurück zu Insights",
       "ecgDescription": "Einkanal-EKG-Aufzeichnungen deines Geräts, jeweils mit dem Ergebnis des Geräts. HealthLog zeigt die Kurve und die Aufzeichnung – die Kurve wird nicht interpretiert."
     },
+    "units": {
+      "steps": "Schritte",
+      "flights": "Etagen",
+      "falls": "Stürze",
+      "years": "Jahre",
+      "breathingEvents": "Ereignisse"
+    },
     "sleep": {
       "title": "Schlaf",
       "description": "Phasen-Aufschlüsselung und nächtliche Dauer – gezogen aus Apple Health.",
diff --git a/messages/en.json b/messages/en.json
index 3d7a6aea7..ead59de68 100644
--- a/messages/en.json
+++ b/messages/en.json
@@ -2860,6 +2860,13 @@
       "scoresBack": "Back to insights",
       "ecgDescription": "Single-lead ECG recordings from your device, each with the device's own result. HealthLog shows the trace and the recording — it does not interpret the waveform."
     },
+    "units": {
+      "steps": "steps",
+      "flights": "flights",
+      "falls": "falls",
+      "years": "years",
+      "breathingEvents": "events"
+    },
     "sleep": {
       "title": "Sleep",
       "description": "Stage breakdown and nightly duration, drawn from Apple Health.",
diff --git a/messages/es.json b/messages/es.json
index cd4c91f63..088243721 100644
--- a/messages/es.json
+++ b/messages/es.json
@@ -2860,6 +2860,13 @@
       "scoresBack": "Volver a Insights",
       "ecgDescription": "Registros de ECG de una derivación de tu dispositivo, cada uno con el resultado del propio dispositivo. HealthLog muestra el trazado y el registro, pero no interpreta la onda."
     },
+    "units": {
+      "steps": "pasos",
+      "flights": "pisos",
+      "falls": "caídas",
+      "years": "años",
+      "breathingEvents": "eventos"
+    },
     "sleep": {
       "title": "Sueño",
       "description": "Desglose por fases y duración nocturna, tomados de Apple Health.",
diff --git a/messages/fr.json b/messages/fr.json
index edcb3446b..ac626a5e9 100644
--- a/messages/fr.json
+++ b/messages/fr.json
@@ -2860,6 +2860,13 @@
       "scoresBack": "Retour aux Insights",
       "ecgDescription": "Enregistrements ECG à dérivation unique de votre appareil, chacun accompagné du résultat de l'appareil. HealthLog affiche le tracé et l'enregistrement, mais n'interprète pas la courbe."
     },
+    "units": {
+      "steps": "pas",
+      "flights": "étages",
+      "falls": "chutes",
+      "years": "ans",
+      "breathingEvents": "événements"
+    },
     "sleep": {
       "title": "Sommeil",
       "description": "Répartition des phases et durée nocturne, issues d’Apple Health.",
diff --git a/messages/it.json b/messages/it.json
index 87f9dfc30..882ca79f3 100644
--- a/messages/it.json
+++ b/messages/it.json
@@ -2860,6 +2860,13 @@
       "scoresBack": "Torna a Insights",
       "ecgDescription": "Registrazioni ECG a singola derivazione dal tuo dispositivo, ciascuna con il risultato del dispositivo. HealthLog mostra il tracciato e la registrazione, ma non interpreta l'onda."
     },
+    "units": {
+      "steps": "passi",
+      "flights": "piani",
+      "falls": "cadute",
+      "years": "anni",
+      "breathingEvents": "eventi"
+    },
     "sleep": {
       "title": "Sonno",
       "description": "Suddivisione per fasi e durata notturna, da Apple Health.",
diff --git a/messages/pl.json b/messages/pl.json
index 5c64b542d..1e1f83bcc 100644
--- a/messages/pl.json
+++ b/messages/pl.json
@@ -2860,6 +2860,13 @@
       "scoresBack": "Powrót do Insights",
       "ecgDescription": "Zapisy EKG jednoodprowadzeniowe z Twojego urządzenia, każdy z wynikiem samego urządzenia. HealthLog pokazuje przebieg i zapis — nie interpretuje krzywej."
     },
+    "units": {
+      "steps": "kroki",
+      "flights": "piętra",
+      "falls": "upadki",
+      "years": "lata",
+      "breathingEvents": "zdarzenia"
+    },
     "sleep": {
       "title": "Sen",
       "description": "Podział na fazy i nocna długość snu, dane z Apple Health.",
diff --git a/src/__tests__/insights-unit-literal-guard.test.ts b/src/__tests__/insights-unit-literal-guard.test.ts
new file mode 100644
index 000000000..d65de1b44
--- /dev/null
+++ b/src/__tests__/insights-unit-literal-guard.test.ts
@@ -0,0 +1,142 @@
+import { describe, it, expect } from "vitest";
+import { readFileSync, readdirSync, statSync } from "node:fs";
+import { join } from "node:path";
+
+/**
+ * GUARD — no insights page passes an English word as a unit.
+ *
+ * A German reader was shown "13,387.6 steps" because `/insights/steps`
+ * handed the scaffold the literal string `steps`. Five of the eighteen unit
+ * literals under `src/app/insights` were English words: steps, years,
+ * flights, falls, and a "count" that was a poor label in any language. The
+ * other thirteen are language-neutral symbols — bpm, %, mmHg, m/s and their
+ * kin read the same in every locale, and "translating" one would be the
+ * opposite mistake.
+ *
+ * So the rule is not "route every unit through i18n", it is: a unit literal
+ * on an insights page must be a SYMBOL. A word travels as an i18n key
+ * (`unitKey`) and is resolved by the scaffold — and that key must resolve in
+ * every locale, which the `t()`-call-site coverage sweep cannot see because
+ * the key is a prop, not a call argument. Both halves are asserted here.
+ */
+
+const LOCALES = ["en", "de", "es", "fr", "it", "pl"] as const;
+const INSIGHTS_PAGES_DIR = join(process.cwd(), "src/app/insights");
+
+/**
+ * Unit strings that are language-neutral and therefore legitimately appear
+ * as literals. Every entry is a symbol, an SI abbreviation, or a composed
+ * one — nothing here changes when the reader's locale does. The empty string
+ * is the "this metric has no unit" case (pain score, waist-to-height ratio).
+ */
+const LANGUAGE_NEUTRAL_UNITS = new Set([
+  "",
+  "%",
+  "/10",
+  "bpm",
+  "breaths/min",
+  "dBA",
+  "kcal",
+  "kg/m²",
+  "m",
+  "m/s",
+  "mL/(kg·min)",
+  "min",
+  "mmHg",
+  "ms",
+]);
+
+/** Every `page.tsx` beneath `src/app/insights`, recursively. */
+function insightsPageFiles(dir: string): string[] {
+  const out: string[] = [];
+  for (const entry of readdirSync(dir)) {
+    const full = join(dir, entry);
+    if (statSync(full).isDirectory()) {
+      out.push(...insightsPageFiles(full));
+    } else if (entry === "page.tsx") {
+      out.push(full);
+    }
+  }
+  return out;
+}
+
+/**
+ * Every `unit="…"` / `yAxisUnit="…"` STRING literal in a source file.
+ * Expression props (`unit={glucoseUnit}`) resolve at runtime from a unit
+ * preference or an i18n call and are out of scope by construction.
+ */
+function unitLiterals(source: string): string[] {
+  return [...source.matchAll(/\b(?:yAxisUnit|unit)="([^"]*)"/g)].map(
+    (match) => match[1],
+  );
+}
+
+/** Every `unitKey="…"` literal in a source file. */
+function unitKeys(source: string): string[] {
+  return [...source.matchAll(/\bunitKey="([^"]*)"/g)].map((match) => match[1]);
+}
+
+/** Resolve a dotted key against a loaded message bundle. */
+function resolve(bundle: unknown, key: string): unknown {
+  let node = bundle;
+  for (const segment of key.split(".")) {
+    if (typeof node !== "object" || node === null) return undefined;
+    node = (node as Record<string, unknown>)[segment];
+  }
+  return node;
+}
+
+describe("insights unit-literal guard", () => {
+  const files = insightsPageFiles(INSIGHTS_PAGES_DIR);
+  const sources = files.map((file) => ({
+    path: file.slice(file.indexOf("src/")),
+    source: readFileSync(file, "utf8"),
+  }));
+
+  it("finds the insights pages to scan", () => {
+    // A broken walk would make every assertion below vacuously true.
+    expect(files.length).toBeGreaterThan(30);
+  });
+
+  it("scans real content — the known symbols are actually present", () => {
+    const seen = new Set(sources.flatMap((f) => unitLiterals(f.source)));
+    // If the matcher silently stopped matching, this fails rather than the
+    // offender list below going quietly empty.
+    for (const symbol of ["bpm", "mmHg", "%", "m/s"]) {
+      expect(seen.has(symbol), `expected to see unit="${symbol}"`).toBe(true);
+    }
+  });
+
+  it("passes only language-neutral unit symbols as literals", () => {
+    const offenders: string[] = [];
+    for (const { path, source } of sources) {
+      for (const literal of unitLiterals(source)) {
+        if (!LANGUAGE_NEUTRAL_UNITS.has(literal)) {
+          // A word-shaped unit belongs in `messages/*.json` behind `unitKey`.
+          offenders.push(`${path}: unit="${literal}"`);
+        }
+      }
+    }
+    expect(offenders).toEqual([]);
+  });
+
+  it("resolves every unitKey in all six locales", () => {
+    const keys = [...new Set(sources.flatMap((f) => unitKeys(f.source)))];
+    // The five words the pages actually carry.
+    expect(keys.length).toBeGreaterThanOrEqual(5);
+
+    const missing: string[] = [];
+    for (const locale of LOCALES) {
+      const bundle = JSON.parse(
+        readFileSync(join(process.cwd(), `messages/${locale}.json`), "utf8"),
+      );
+      for (const key of keys) {
+        const value = resolve(bundle, key);
+        if (typeof value !== "string" || value.trim() === "") {
+          missing.push(`${locale}: ${key}`);
+        }
+      }
+    }
+    expect(missing).toEqual([]);
+  });
+});
diff --git a/src/app/insights/breathing-disturbances/page.tsx b/src/app/insights/breathing-disturbances/page.tsx
index 51324fe2a..c9d62cb30 100644
--- a/src/app/insights/breathing-disturbances/page.tsx
+++ b/src/app/insights/breathing-disturbances/page.tsx
@@ -21,8 +21,7 @@ export default function InsightsBreathingDisturbancesPage() {
       i18nPrefix="insights.breathingDisturbances"
       explainerMetric="breathingDisturbances"
       color="var(--info)"
-      unit="count"
-      yAxisUnit="count"
+      unitKey="insights.units.breathingEvents"
       emptyStateIcon={<Wind className="size-6" />}
       emptyStateCtaType={null}
       coachPrefill="I haven't logged any sleep-breathing-disturbance data yet — what does this metric tell me about my health, and how do I improve it?"
diff --git a/src/app/insights/falls/page.tsx b/src/app/insights/falls/page.tsx
index 9cd6ff193..157383c52 100644
--- a/src/app/insights/falls/page.tsx
+++ b/src/app/insights/falls/page.tsx
@@ -20,8 +20,7 @@ export default function InsightsFallsPage() {
       i18nPrefix="insights.falls"
       explainerMetric="falls"
       color="var(--destructive)"
-      unit="falls"
-      yAxisUnit="falls"
+      unitKey="insights.units.falls"
       emptyStateIcon={<PersonStanding className="size-6" />}
       emptyStateCtaType={null}
       coachPrefill="I haven't logged any fall data yet — what does this metric tell me about my health, and how do I lower my fall risk?"
diff --git a/src/app/insights/flights-climbed/page.tsx b/src/app/insights/flights-climbed/page.tsx
index 8486cfbf3..c76a259f0 100644
--- a/src/app/insights/flights-climbed/page.tsx
+++ b/src/app/insights/flights-climbed/page.tsx
@@ -22,8 +22,7 @@ export default function InsightsStockwerkePage() {
       i18nPrefix="insights.flightsClimbed"
       explainerMetric="flightsClimbed"
       color="var(--success)"
-      unit="flights"
-      yAxisUnit="flights"
+      unitKey="insights.units.flights"
       emptyStateIcon={<TrendingUp className="size-6" />}
       emptyStateCtaType={null}
       coachPrefill="I haven't logged any flights climbed yet — what does this metric tell me about my health, and how do I improve it?"
diff --git a/src/app/insights/steps/page.tsx b/src/app/insights/steps/page.tsx
index 134694d32..cbd8015d3 100644
--- a/src/app/insights/steps/page.tsx
+++ b/src/app/insights/steps/page.tsx
@@ -27,8 +27,7 @@ export default function InsightsStepsPage() {
       explainerMetric="steps"
       statIcon={Footprints}
       color="var(--success)"
-      unit="steps"
-      yAxisUnit="steps"
+      unitKey="insights.units.steps"
       emptyStateIcon={<Footprints className="size-6" />}
       emptyStateCtaType={null}
       captureType="ACTIVITY_STEPS"
diff --git a/src/app/insights/vascular-age/page.tsx b/src/app/insights/vascular-age/page.tsx
index dfc04b043..82edd06fc 100644
--- a/src/app/insights/vascular-age/page.tsx
+++ b/src/app/insights/vascular-age/page.tsx
@@ -22,8 +22,7 @@ export default function InsightsGefaessalterPage() {
       i18nPrefix="insights.vascularAge"
       explainerMetric="vascularAge"
       color="var(--chart-3)"
-      unit="years"
-      yAxisUnit="years"
+      unitKey="insights.units.years"
       emptyStateIcon={<HeartPulse className="size-6" />}
       emptyStateCtaType={null}
       coachPrefill="I haven't logged any vascular age yet — what does this metric tell me about my health, and how do I improve it?"
diff --git a/src/components/charts/health-chart.tsx b/src/components/charts/health-chart.tsx
index 26958e593..ea6df35be 100644
--- a/src/components/charts/health-chart.tsx
+++ b/src/components/charts/health-chart.tsx
@@ -1337,7 +1337,7 @@ export function HealthChart({
       .filter((value): value is number => typeof value === "number")
       .filter((value) => Number.isFinite(value));
 
-    return computePaddedYDomain(values);
+    return computePaddedYDomain(values, types);
   }, [
     chartDataWithCompare,
     effectiveCompareBaseline,
diff --git a/src/components/insights/__tests__/integer-metric-precision-guard.test.tsx b/src/components/insights/__tests__/integer-metric-precision-guard.test.tsx
new file mode 100644
index 000000000..a6da4062a
--- /dev/null
+++ b/src/components/insights/__tests__/integer-metric-precision-guard.test.tsx
@@ -0,0 +1,174 @@
+import { describe, it, expect, vi, beforeEach } from "vitest";
+import { renderToStaticMarkup } from "react-dom/server";
+import { QueryClient, QueryClientProvider } from "@tanstack/react-query";
+
+import { I18nProvider } from "@/lib/i18n/context";
+import {
+  INTEGER_VALUED_MEASUREMENT_TYPES,
+  metricFractionDigits,
+  DEFAULT_METRIC_FRACTION_DIGITS,
+} from "@/lib/measurements/value-domain";
+import type { CoachReadStripData } from "@/lib/insights/derived/coach-read-shape";
+
+/**
+ * GUARD — an integer-valued metric never renders a fractional part.
+ *
+ * The step sub-page read "MIN 104.0 steps" and "your usual range is
+ * …–13,387.6 steps". Precision was a per-page prop defaulting to one
+ * decimal: the pulse page remembered to pass 0, the step page did not, and
+ * a tenth of a step was rendered. Every page remembering this individually
+ * IS the defect — so the assertions below pin that the METRIC answers, and
+ * that a page which passes nothing still renders a count as a count.
+ *
+ * Both surfaces on the reported card are covered: the Min/Max stat strip and
+ * the coach-read strip underneath it.
+ */
+
+vi.mock("next/dynamic", () => ({
+  default: () => {
+    const Stub = () => <div data-slot="healthkit-chart-stub" />;
+    Stub.displayName = "HealthChartStub";
+    return Stub;
+  },
+}));
+
+vi.mock("next/navigation", () => ({
+  usePathname: () => "/insights/steps",
+}));
+
+vi.mock("@/hooks/use-auth", () => ({
+  useAuth: () => ({
+    user: { timezone: "UTC", dateOfBirth: null, gender: null },
+    isAuthenticated: true,
+  }),
+}));
+
+vi.mock("@/hooks/use-insights-layout-prefs", () => ({
+  useInsightsLayoutPrefs: () => ({ layout: null, compareBaseline: false }),
+}));
+
+// The coach-read strip paints nothing until it is client-mounted (React
+// #418). Force the mounted branch so the band sentence reaches the markup.
+vi.mock("@/hooks/use-mounted", () => ({ useMounted: () => true }));
+
+const analyticsMock = vi.fn();
+vi.mock("@/hooks/use-insights-analytics", () => ({
+  useInsightsAnalytics: () => analyticsMock(),
+}));
+
+const coachReadMock = vi.fn();
+vi.mock("@tanstack/react-query", async (importOriginal) => {
+  const actual = await importOriginal<typeof import("@tanstack/react-query")>();
+  return { ...actual, useQuery: () => coachReadMock() };
+});
+
+import { CoachReadStrip } from "../derived/coach-read-strip";
+import InsightsStepsPage from "@/app/insights/steps/page";
+
+function render(node: React.ReactNode, locale: "en" | "de" = "de") {
+  const queryClient = new QueryClient({
+    defaultOptions: { queries: { retry: false, staleTime: Infinity } },
+  });
+  return renderToStaticMarkup(
+    <QueryClientProvider client={queryClient}>
+      <I18nProvider initialLocale={locale}>{node}</I18nProvider>
+    </QueryClientProvider>,
+  );
+}
+
+/** The band and the reading the reporter saw, to the digit. */
+const REPORTED_BAND: CoachReadStripData = {
+  learning: false,
+  baseline: {
+    low: 104,
+    high: 13387.6,
+    latest: 8213.4,
+    placement: "within",
+  },
+  driver: null,
+} as unknown as CoachReadStripData;
+
+/**
+ * A German-locale decimal on a count: "104,0", "13.387,6". The Latin-1
+ * comma-decimal shape is what the reporter photographed.
+ */
+const FRACTIONAL_GERMAN = /\d,\d/;
+
+beforeEach(() => {
+  analyticsMock.mockReset();
+  coachReadMock.mockReset();
+});
+
+describe("integer-metric precision guard", () => {
+  it("resolves zero decimals for every discrete metric", () => {
+    expect(INTEGER_VALUED_MEASUREMENT_TYPES.size).toBeGreaterThan(10);
+    for (const type of INTEGER_VALUED_MEASUREMENT_TYPES) {
+      expect(metricFractionDigits(type), type).toBe(0);
+    }
+    // A continuous metric keeps the shared default; an unknown one too.
+    expect(metricFractionDigits("PULSE")).toBe(DEFAULT_METRIC_FRACTION_DIGITS);
+    expect(metricFractionDigits("WEIGHT")).toBe(DEFAULT_METRIC_FRACTION_DIGITS);
+    expect(metricFractionDigits(null)).toBe(DEFAULT_METRIC_FRACTION_DIGITS);
+  });
+
+  it("renders the coach-read band without a fractional step", () => {
+    coachReadMock.mockReturnValue({ data: REPORTED_BAND });
+
+    const html = render(
+      <CoachReadStrip metricType="ACTIVITY_STEPS" unit="Schritte" />,
+    );
+
+    expect(html).toContain('data-slot="coach-read-baseline"');
+    expect(html).not.toMatch(FRACTIONAL_GERMAN);
+    // The band edges are still there, rounded to whole steps.
+    expect(html).toContain("13.388");
+    expect(html).toContain("104");
+  });
+
+  it("keeps the decimal for a metric that is not a count", () => {
+    coachReadMock.mockReturnValue({
+      data: {
+        learning: false,
+        baseline: { low: 71.4, high: 84.2, latest: 78.6, placement: "within" },
+        driver: null,
+      } as unknown as CoachReadStripData,
+    });
+
+    const html = render(<CoachReadStrip metricType="WEIGHT" unit="kg" />);
+    expect(html).toMatch(FRACTIONAL_GERMAN);
+  });
+
+  it("renders the step page stat strip without a fractional step", () => {
+    // The page passes no precision prop at all — that is the point.
+    analyticsMock.mockReturnValue({
+      data: {
+        summaries: {
+          ACTIVITY_STEPS: {
+            count: 214,
+            latest: 8213,
+            min: 104,
+            max: 11762,
+            mean: 6431.72,
+            median: 6802.5,
+          },
+        },
+      },
+      isEmpty: false,
+      isLoading: false,
+    });
+    coachReadMock.mockReturnValue({ data: undefined });
+
+    const html = render(<InsightsStepsPage />);
+
+    expect(html).toContain('data-slot="metric-stat-strip"');
+    expect(html).not.toMatch(FRACTIONAL_GERMAN);
+    // The numbers themselves survive, thousands-grouped and whole.
+    expect(html).toContain("11.762");
+    expect(html).toContain("104");
+    // …and the unit reads in German, not as the English word. (The route
+    // slug `/insights/steps` legitimately appears in the header links, so
+    // match the unit in its rendered position: right after a number.)
+    expect(html).toContain("104 Schritte");
+    expect(html).not.toMatch(/\d\s*steps\b/);
+  });
+});
diff --git a/src/components/insights/derived/coach-read-strip.tsx b/src/components/insights/derived/coach-read-strip.tsx
index 10c5bf57e..8dfad52fe 100644
--- a/src/components/insights/derived/coach-read-strip.tsx
+++ b/src/components/insights/derived/coach-read-strip.tsx
@@ -8,6 +8,7 @@ import { useUnitDisplay } from "@/hooks/use-unit-display";
 import { useMounted } from "@/hooks/use-mounted";
 import { useTranslations } from "@/lib/i18n/context";
 import { queryKeys } from "@/lib/query-keys";
+import { metricFractionDigits } from "@/lib/measurements/value-domain";
 import { apiGet } from "@/lib/api/api-fetch";
 import { Card, CardContent, CardHeader } from "@/components/ui/card";
 import { TileHeader } from "@/components/insights/tile-header";
@@ -38,9 +39,12 @@ export interface CoachReadStripProps {
   /** Unit suffix rendered next to the band edges + today's value. */
   unit: string;
   /**
-   * Decimal precision for the formatted numbers. Defaults to 1 — enough for
-   * weight (78.4) / HRV (41.5); integer metrics drop the trailing zero via
-   * `Intl.NumberFormat`. Pages pass 0 for integer-only metrics (BP, steps).
+   * Decimal precision for the formatted numbers. Optional: when omitted the
+   * precision follows the METRIC (`metricFractionDigits`) — a discrete metric
+   * resolves 0, everything else the shared default of 1. It used to default
+   * to a flat 1 and rely on each page remembering to pass 0, which is how a
+   * step page came to print "104.0 steps". Pass it only to override the
+   * metric's own answer.
    */
   fractionDigits?: number;
   /**
@@ -55,9 +59,10 @@ export interface CoachReadStripProps {
 export function CoachReadStrip({
   metricType,
   unit,
-  fractionDigits = 1,
+  fractionDigits,
   valueScale = 1,
 }: CoachReadStripProps) {
+  const digits = fractionDigits ?? metricFractionDigits(metricType);
   const { isAuthenticated } = useAuth();
   const { t, locale } = useTranslations();
   const mounted = useMounted();
@@ -89,7 +94,7 @@ export function CoachReadStrip({
   const fmt = (value: number): string =>
     new Intl.NumberFormat(locale, {
       minimumFractionDigits: 0,
-      maximumFractionDigits: fractionDigits,
+      maximumFractionDigits: digits,
     }).format(
       transformed
         ? unitDisplay.toDisplay(metricType, value)
diff --git a/src/components/insights/healthkit-metric-page.tsx b/src/components/insights/healthkit-metric-page.tsx
index e4c0519b4..c8ccf4cad 100644
--- a/src/components/insights/healthkit-metric-page.tsx
+++ b/src/components/insights/healthkit-metric-page.tsx
@@ -14,6 +14,7 @@ import { useTranslations } from "@/lib/i18n/context";
 import type { InsightMetric } from "@/lib/insights/metric-availability";
 import type { MetricStatusMetricId } from "@/lib/insights/metric-status-registry";
 import type { ChartOverlayKey } from "@/lib/dashboard-layout";
+import { metricFractionDigits } from "@/lib/measurements/value-domain";
 import { Button } from "@/components/ui/button";
 import { QueryErrorRow } from "@/components/ui/query-error-row";
 import { Card, CardContent } from "@/components/ui/card";
@@ -98,6 +99,17 @@ export interface HealthKitMetricPageProps {
    * transformed types omit these props; everything else still passes `unit`.
    */
   unit?: string;
+  /**
+   * i18n key for a unit that is a WORD rather than a symbol — `steps`,
+   * `flights`, `falls`, `years`, `events`. Resolved through `t()` so it
+   * renders in the reader's language; a German user was shown "13.387,6
+   * steps". Symbols (`bpm`, `mmHg`, `%`, `m/s`, `kg/m²`, …) are language-
+   * neutral and stay literals in `unit` — translating a symbol would be the
+   * opposite mistake. Wins over `unit` / `yAxisUnit` for both the chart and
+   * the axis label; a type with a registered display transform still
+   * overrides everything.
+   */
+  unitKey?: string;
   /** Optional y-axis label shown above the unit. */
   yAxisUnit?: string;
   /** Optional value bands (Apple-Health-style target zone shading). */
@@ -206,6 +218,7 @@ export function HealthKitMetricPage({
   i18nPrefix,
   color,
   unit,
+  unitKey,
   yAxisUnit,
   valueBands,
   emptyStateCtaType,
@@ -264,13 +277,24 @@ export function HealthKitMetricPage({
   const transform = unitDisplay.isTransformed(effectiveType)
     ? unitDisplay.transformFor(effectiveType)
     : null;
-  const resolvedUnit = transform ? transform.displayUnit : unit;
-  const resolvedYAxisUnit = transform ? transform.displayUnit : yAxisUnit;
+  // A word-shaped unit arrives as an i18n key and is resolved here, once, for
+  // the chart line, the axis label, the stat strip and the coach-read strip.
+  const localisedUnit = unitKey ? t(unitKey) : undefined;
+  const resolvedUnit = transform
+    ? transform.displayUnit
+    : (localisedUnit ?? unit);
+  const resolvedYAxisUnit = transform
+    ? transform.displayUnit
+    : (localisedUnit ?? yAxisUnit);
   const resolvedScale = transform ? transform.factor : (valueScale ?? 1);
   const resolvedOffset = transform ? (transform.offset ?? 0) : 0;
+  // Precision follows the METRIC, not the page. A discrete metric renders no
+  // fractional part even when the page says nothing — the steps page said
+  // nothing and its Min read "104.0 steps". An explicit `statFractionDigits`
+  // still wins for the metrics that genuinely need one (mmol/L, skin temp).
   const resolvedFractionDigits = transform
     ? transform.decimals
-    : statFractionDigits;
+    : (statFractionDigits ?? metricFractionDigits(effectiveType));
   // Value bands are absolute bounds → affine-convert (factor + offset) so the
   // shaded zone tracks the converted line. Metric users get the identity.
   const resolvedBands =
diff --git a/src/lib/ai/coach/snapshot-blocks/core-metrics-block.ts b/src/lib/ai/coach/snapshot-blocks/core-metrics-block.ts
index c4a5f377d..6049a5986 100644
--- a/src/lib/ai/coach/snapshot-blocks/core-metrics-block.ts
+++ b/src/lib/ai/coach/snapshot-blocks/core-metrics-block.ts
@@ -59,8 +59,8 @@ export function buildCoreMetricsBlocks(
     );
     const olderSys = sysRows.filter((row) => row.measuredAt < ctx.recentCutoff);
     const olderDia = diaRows.filter((row) => row.measuredAt < ctx.recentCutoff);
-    const sysBand = bpBandFromRows(sysRows);
-    const diaBand = bpBandFromRows(diaRows);
+    const sysBand = bpBandFromRows(sysRows, "BLOOD_PRESSURE_SYS");
+    const diaBand = bpBandFromRows(diaRows, "BLOOD_PRESSURE_DIA");
     const usualRange =
       sysBand || diaBand
         ? {
diff --git a/src/lib/ai/coach/snapshot-series.ts b/src/lib/ai/coach/snapshot-series.ts
index 636b9f5bc..9357b0716 100644
--- a/src/lib/ai/coach/snapshot-series.ts
+++ b/src/lib/ai/coach/snapshot-series.ts
@@ -293,6 +293,7 @@ export function buildDailyBpRows(
  */
 export function bpBandFromRows(
   rows: ReadonlyArray<{ measuredAt: Date; value: number }>,
+  type: "BLOOD_PRESSURE_SYS" | "BLOOD_PRESSURE_DIA",
 ): { low: number; high: number } | null {
   const byDay = new Map<string, { sum: number; count: number }>();
   for (const r of rows) {
@@ -304,7 +305,7 @@ export function bpBandFromRows(
   }
   const dayMeans = [...byDay.values()].map((a) => a.sum / a.count);
   if (dayMeans.length < 7) return null;
-  const band = buildBaselineBand(dayMeans);
+  const band = buildBaselineBand(dayMeans, type);
   if (!band) return null;
   return { low: Math.round(band.low), high: Math.round(band.high) };
 }
diff --git a/src/lib/illness/correlation.ts b/src/lib/illness/correlation.ts
index e9edbe04c..7dd52abcc 100644
--- a/src/lib/illness/correlation.ts
+++ b/src/lib/illness/correlation.ts
@@ -425,7 +425,10 @@ function bandFor(series: VitalSeries): {
   spread: number;
 } | null {
   if (series.baselineDays.length < MIN_BASELINE_DAYS) return null;
-  const band = buildBaselineBand(series.baselineDays.map((p) => p.mean));
+  const band = buildBaselineBand(
+    series.baselineDays.map((p) => p.mean),
+    series.type,
+  );
   if (!band || band.spread <= 0) return null;
   return { center: band.center, spread: band.spread };
 }
diff --git a/src/lib/insights/chart-y-domain.ts b/src/lib/insights/chart-y-domain.ts
index 4b278992b..53b2ee018 100644
--- a/src/lib/insights/chart-y-domain.ts
+++ b/src/lib/insights/chart-y-domain.ts
@@ -8,14 +8,25 @@
  *   (at least 1 unit), with a little extra headroom on top.
  * - Otherwise: pad the bottom by 8% of the span (min 0.5) and the top by
  *   16% of the span (min 1).
- * - Zero clamp: when the series contains no negative values the lower
- *   bound never dips below 0 — padding only extends upward or down to 0.
- *   Counts, steps, weights etc. must not render a negative axis. Series
- *   with genuine negative values (deltas, differences) keep the full
- *   downward padding.
+ * - Zero clamp: the lower bound never dips below 0 when the charted metrics
+ *   cannot be negative — padding only extends upward or down to 0. Counts,
+ *   steps, weights etc. must not render a negative axis. Series with genuine
+ *   negative values (deltas, differences) keep the full downward padding.
+ *
+ *   "Cannot be negative" is answered by `areAllNonNegativeMetrics` off the
+ *   metric's own declared plausibility domain — the SAME fact the personal
+ *   baseline band floors against, so the axis and the sentence printed under
+ *   it can no longer disagree. It also covers the derived overlays: a trend
+ *   line extrapolating a step count below zero now clips at the axis floor
+ *   instead of dragging the whole chart into negative territory. The observed
+ *   minimum stays a second, weaker trigger, so a caller that names no type
+ *   (a mini chart over an anonymous series) keeps the data-derived behaviour.
  */
+import { areAllNonNegativeMetrics } from "@/lib/measurements/value-domain";
+
 export function computePaddedYDomain(
   values: readonly number[],
+  types: readonly (string | null | undefined)[] = [],
 ): [number, number] | undefined {
   const finite = values.filter(
     (value): value is number =>
@@ -26,7 +37,9 @@ export function computePaddedYDomain(
   const min = Math.min(...finite);
   const max = Math.max(...finite);
   // Non-negative series never get a negative lower bound.
-  const clampLower = (lower: number) => (min >= 0 ? Math.max(0, lower) : lower);
+  const nonNegative = min >= 0 || areAllNonNegativeMetrics(types);
+  const clampLower = (lower: number) =>
+    nonNegative ? Math.max(0, lower) : lower;
 
   if (min === max) {
     const delta = Math.max(Math.abs(min) * 0.05, 1);
diff --git a/src/lib/insights/derived/__tests__/baseline.test.ts b/src/lib/insights/derived/__tests__/baseline.test.ts
index 2c13ab12b..a4742a89a 100644
--- a/src/lib/insights/derived/__tests__/baseline.test.ts
+++ b/src/lib/insights/derived/__tests__/baseline.test.ts
@@ -53,7 +53,7 @@ describe("pure statistics", () => {
   });
 
   it("buildBaselineBand returns a symmetric MAD band", () => {
-    const band = buildBaselineBand([50, 52, 54, 56, 58], 3);
+    const band = buildBaselineBand([50, 52, 54, 56, 58], "PULSE", 3);
     expect(band).not.toBeNull();
     expect(band!.center).toBe(54);
     expect(band!.low).toBeLessThan(band!.center);
@@ -65,8 +65,8 @@ describe("pure statistics", () => {
   it("parity: a composed-DAY-bucket series and the raw-DAY series yield the same band", () => {
     // Same per-day means whether they arrive as raw rows or DAY rollups.
     const perDayMeans = [60, 61, 62, 59, 63, 58, 64];
-    const fromRaw = buildBaselineBand(perDayMeans, 3);
-    const fromRollup = buildBaselineBand([...perDayMeans], 3);
+    const fromRaw = buildBaselineBand(perDayMeans, "PULSE", 3);
+    const fromRollup = buildBaselineBand([...perDayMeans], "PULSE", 3);
     expect(fromRollup).toEqual(fromRaw);
   });
 });
diff --git a/src/lib/insights/derived/baseline.ts b/src/lib/insights/derived/baseline.ts
index 83c090e8f..8ae06c775 100644
--- a/src/lib/insights/derived/baseline.ts
+++ b/src/lib/insights/derived/baseline.ts
@@ -32,6 +32,7 @@ import type { MeasurementType, PrismaClient } from "@/generated/prisma/client";
 import { prisma } from "@/lib/db";
 import { getAgeFromDateOfBirth } from "@/lib/analytics/pulse-targets";
 import { toProfileSex } from "@/lib/profile/sex";
+import { clampDerivedLowerBound } from "@/lib/measurements/value-domain";
 import type { ProfileSex } from "@/lib/profile/sex";
 import {
   probeRollupCoverage,
@@ -63,7 +64,11 @@ export interface VitalsBaselineValue {
   type: MeasurementType;
   /** Robust center (median of the per-day means). */
   center: number;
-  /** Band lower edge (center − k·MAD·scale). */
+  /**
+   * Band lower edge (center − k·MAD·scale), floored at 0 for a metric whose
+   * plausibility domain forbids negative values. `spread` below stays the
+   * unclamped dispersion, so a deviation-in-σ calculation is unaffected.
+   */
   low: number;
   /** Band upper edge (center + k·MAD·scale). */
   high: number;
@@ -173,9 +178,20 @@ export function medianAbsoluteDeviation(values: number[]): number {
  * caller supplies the already-resolved DAY-native series so this can be
  * unit-tested against both a raw-DAY series and a rollup-composed series
  * (they must agree: DAY rollup `mean` equals the per-day raw mean).
+ *
+ * `type` names the metric the series belongs to and is REQUIRED, not
+ * optional: `center − spread` is arithmetic, and arithmetic does not know
+ * that a step, a flight, or a kilocalorie cannot be owed. On a metric with a
+ * wide relative spread the lower edge crosses zero and the strip underneath
+ * the chart reads "your usual range is −5,595.6–13,387.6 steps". The floor
+ * comes from `clampDerivedLowerBound`, which reads the metric's declared
+ * plausibility domain — the same fact the chart's y-axis clamps against, now
+ * answered in one place instead of two. Pass `null` only for a series with no
+ * metric identity; the band then keeps the raw arithmetic edge.
  */
 export function buildBaselineBand(
   dayMeans: number[],
+  type: MeasurementType | null,
   k: number = DEFAULT_MAD_K,
 ): Omit<VitalsBaselineValue, "type" | "series"> | null {
   if (dayMeans.length === 0) return null;
@@ -185,7 +201,7 @@ export function buildBaselineBand(
   const spread = k * mad * MAD_SIGMA_SCALE;
   return {
     center,
-    low: center - spread,
+    low: clampDerivedLowerBound(type, center - spread),
     high: center + spread,
     spread,
     sampleDays: dayMeans.length,
@@ -334,6 +350,7 @@ export async function computeVitalsBaseline(
 
   const band = buildBaselineBand(
     points.map((p) => p.mean),
+    type,
     k,
   );
   if (!band) {
diff --git a/src/lib/insights/narrative/period-narrative.ts b/src/lib/insights/narrative/period-narrative.ts
index 1740c81dc..66ddcd8f9 100644
--- a/src/lib/insights/narrative/period-narrative.ts
+++ b/src/lib/insights/narrative/period-narrative.ts
@@ -363,7 +363,7 @@ export function assemblePeriodNarrativeContext(
     const { current, prior } = splitByPeriod(points, currentFrom, priorFrom);
     if (prior.length < MIN_BASELINE_DAYS) continue;
     if (current.length < MIN_COVERED_DAYS_PER_METRIC) continue;
-    const band = buildBaselineBand(prior);
+    const band = buildBaselineBand(prior, type);
     if (!band) continue;
     const center = median(current);
     const above = center > band.high;
@@ -454,7 +454,7 @@ function computeCoincidentFlags(
       }
     }
     if (prior.length < MIN_BASELINE_DAYS) continue;
-    const band = buildBaselineBand(prior);
+    const band = buildBaselineBand(prior, type);
     if (band) bands.set(type, { low: band.low, high: band.high });
   }
 
diff --git a/src/lib/insights/streak-detector.ts b/src/lib/insights/streak-detector.ts
index 9484b3a02..bb21c1ffb 100644
--- a/src/lib/insights/streak-detector.ts
+++ b/src/lib/insights/streak-detector.ts
@@ -28,6 +28,7 @@
  *
  * Pure: no DB, no clock, no network. Fully unit-testable over injected series.
  */
+import type { MeasurementType } from "@/generated/prisma/client";
 import { buildBaselineBand } from "@/lib/insights/derived/baseline";
 
 /** One DAY-bucket point: a calendar day key (YYYY-MM-DD) + that day's mean. */
@@ -103,10 +104,15 @@ function placeValue(value: number, band: StreakBand): BandPlacement {
  * `band` may be supplied (e.g. a prior-period band) — when omitted it is built
  * from the whole series via `buildBaselineBand`. A gap day (a calendar day with
  * no point between two present days) BREAKS any streak that would span it.
+ *
+ * `metricType` names the metric the series belongs to so a self-built band
+ * floors at zero on a metric that cannot go negative. Omit it only when the
+ * series genuinely has no metric identity, or when the caller supplies `band`.
  */
 export function detectStreak(
   series: StreakPoint[],
   band?: StreakBand | null,
+  metricType?: string | null,
 ): StreakResult {
   const empty: StreakResult = {
     latestPlacement: null,
@@ -127,7 +133,12 @@ export function detectStreak(
 
   // Resolve the personal band: caller-supplied, else median ± k·MAD over the
   // whole series. Null (too little history) → omit rather than guess.
-  const resolvedBand = band ?? buildBandFromSeries(points.map((p) => p.value));
+  const resolvedBand =
+    band ??
+    buildBandFromSeries(
+      points.map((p) => p.value),
+      metricType,
+    );
   if (!resolvedBand) return empty;
 
   // Per-day placement, ascending. A gap day inserts an explicit break marker so
@@ -194,8 +205,14 @@ export function detectStreak(
 }
 
 /** Build the personal band from a value series; null when too little data. */
-function buildBandFromSeries(values: number[]): StreakBand | null {
-  const band = buildBaselineBand(values);
+function buildBandFromSeries(
+  values: number[],
+  metricType: string | null | undefined,
+): StreakBand | null {
+  const band = buildBaselineBand(
+    values,
+    (metricType ?? null) as MeasurementType | null,
+  );
   if (!band) return null;
   if (!Number.isFinite(band.low) || !Number.isFinite(band.high)) return null;
   return { low: band.low, high: band.high };
diff --git a/src/lib/measurements/__tests__/non-negative-metric-guard.test.ts b/src/lib/measurements/__tests__/non-negative-metric-guard.test.ts
new file mode 100644
index 000000000..98a6e1e4a
--- /dev/null
+++ b/src/lib/measurements/__tests__/non-negative-metric-guard.test.ts
@@ -0,0 +1,116 @@
+import { describe, it, expect } from "vitest";
+
+import {
+  VALUE_RANGES,
+  measurementTypeEnum,
+} from "@/lib/validations/measurement";
+import {
+  areAllNonNegativeMetrics,
+  isNonNegativeMetric,
+} from "@/lib/measurements/value-domain";
+import { buildBaselineBand } from "@/lib/insights/derived/baseline";
+import { computePaddedYDomain } from "@/lib/insights/chart-y-domain";
+
+/**
+ * GUARD — a non-negative metric's baseline `low` is never below zero.
+ *
+ * The step sub-page printed "your usual range is −5,595.6–13,387.6 steps"
+ * because the band's lower edge is `median − k·MAD·scale` and nothing said a
+ * step cannot be owed. The chart above it already refused a negative axis, so
+ * the app held both answers at once.
+ *
+ * These assertions pin the fixed shape end to end: the fact is declared once
+ * (the metric's plausibility floor), the band reads it, and the axis reads the
+ * same one. A series engineered so the spread exceeds the median is the exact
+ * condition that produced the reported sentence.
+ */
+
+/**
+ * Median 10, MAD 10 → spread = 3 · 10 · 1.4826 ≈ 44.5, i.e. well past the
+ * centre. The raw arithmetic edge is ≈ −34.5.
+ */
+const SPREAD_EXCEEDS_CENTRE = [0, 0, 0, 10, 20, 30, 40];
+
+/** The two types whose declared floor is genuinely signed. */
+const SIGNED_TYPES = ["ANS_CHARGE", "BODY_TEMPERATURE_DEVIATION"] as const;
+
+describe("non-negative metric guard", () => {
+  it("every MeasurementType declares a plausibility range", () => {
+    // The range map is the home of the "can this be negative" fact. A type
+    // missing from it answers "unknown" and silently loses the floor — and,
+    // separately, passes any number at all through ingest validation.
+    const missing = measurementTypeEnum.options.filter(
+      (type) => VALUE_RANGES[type] === undefined,
+    );
+    expect(missing).toEqual([]);
+  });
+
+  it("classifies every type from its own declared floor", () => {
+    for (const type of measurementTypeEnum.options) {
+      expect(isNonNegativeMetric(type)).toBe(VALUE_RANGES[type].min >= 0);
+    }
+    for (const type of SIGNED_TYPES) {
+      expect(isNonNegativeMetric(type)).toBe(false);
+    }
+    // An unnamed or unknown metric is "unknown", never "non-negative".
+    expect(isNonNegativeMetric(null)).toBe(false);
+    expect(isNonNegativeMetric("NOT_A_METRIC")).toBe(false);
+    expect(areAllNonNegativeMetrics([])).toBe(false);
+    expect(areAllNonNegativeMetrics(["ACTIVITY_STEPS", "ANS_CHARGE"])).toBe(
+      false,
+    );
+  });
+
+  it("never floors the baseline band below zero for a non-negative metric", () => {
+    const nonNegative = measurementTypeEnum.options.filter((type) =>
+      isNonNegativeMetric(type),
+    );
+    // Sanity: the sweep must actually cover the bulk of the catalogue.
+    expect(nonNegative.length).toBeGreaterThan(60);
+
+    for (const type of nonNegative) {
+      const band = buildBaselineBand(SPREAD_EXCEEDS_CENTRE, type);
+      expect(band, type).not.toBeNull();
+      expect(band!.low, `${type} band low`).toBeGreaterThanOrEqual(0);
+      // The dispersion itself stays unclamped — a deviation-in-σ calculation
+      // reads `spread`, and flooring it would understate every excursion.
+      expect(band!.spread, `${type} spread`).toBeGreaterThan(band!.center);
+    }
+  });
+
+  it("reproduces the reported step sentence with a non-negative lower edge", () => {
+    // Roughly the reported shape: a median around 4,000 steps with days near
+    // zero, which is what pushed the MAD band past the origin.
+    const dayMeans = [0, 120, 900, 4000, 6200, 9800, 11762];
+    const band = buildBaselineBand(dayMeans, "ACTIVITY_STEPS");
+    expect(band!.low).toBe(0);
+    expect(band!.high).toBeGreaterThan(band!.center);
+  });
+
+  it("keeps the real lower edge for a metric that can genuinely be negative", () => {
+    for (const type of SIGNED_TYPES) {
+      const band = buildBaselineBand(SPREAD_EXCEEDS_CENTRE, type);
+      expect(band!.low, type).toBeLessThan(0);
+    }
+    // No metric identity → no invented floor either.
+    expect(buildBaselineBand(SPREAD_EXCEEDS_CENTRE, null)!.low).toBeLessThan(0);
+  });
+
+  it("gives the chart axis the same answer as the band", () => {
+    // A derived overlay (trend line, moving average) can extrapolate a step
+    // count below zero even though no observation ever was. The axis floors
+    // it because the METRIC cannot be negative, not because the data was.
+    const domain = computePaddedYDomain([-320, 1200, 8400], ["ACTIVITY_STEPS"]);
+    expect(domain![0]).toBe(0);
+
+    // A signed metric keeps its downward padding.
+    const signed = computePaddedYDomain([-40, 5, 60], ["ANS_CHARGE"]);
+    expect(signed![0]).toBeLessThan(0);
+
+    // An anonymous series keeps the older data-derived behaviour: padding
+    // that would dip under an all-positive series stops at 0, a series with
+    // real negative values keeps the full downward padding.
+    expect(computePaddedYDomain([0.2, 0.5])![0]).toBe(0);
+    expect(computePaddedYDomain([-5, 3, 10])![0]).toBeLessThan(0);
+  });
+});
diff --git a/src/lib/measurements/value-domain.ts b/src/lib/measurements/value-domain.ts
new file mode 100644
index 000000000..33e913f27
--- /dev/null
+++ b/src/lib/measurements/value-domain.ts
@@ -0,0 +1,115 @@
+/**
+ * Per-metric numeric-domain facts — the ONE home for the two questions the
+ * derivation and render layers kept answering independently, and therefore
+ * kept answering differently:
+ *
+ *   1. **Can this metric be negative?** The chart's y-axis already refused a
+ *      negative lower bound (`chart-y-domain.ts`) while the personal-baseline
+ *      band underneath the same chart happily printed one, so a step page
+ *      could read "your usual range is −5,595.6–13,387.6 steps". Same app,
+ *      same question, two answers. The fact is a property of the METRIC, not
+ *      of the surface that renders it, so it belongs beside the metric — and
+ *      it is already declared there: `VALUE_RANGES` in
+ *      `@/lib/validations/measurement` is the app-wide plausibility domain
+ *      every ingest path validates against, and its `min` IS the metric's
+ *      floor. Nothing new to maintain; this module only reads it. Two types
+ *      declare a genuinely signed floor (`ANS_CHARGE`,
+ *      `BODY_TEMPERATURE_DEVIATION`) and are correctly excluded.
+ *
+ *   2. **Is this metric integer-valued?** A step count has no fractional
+ *      part, so "104.0 steps" is not a rounding preference, it is wrong. This
+ *      one had no home at all — every sub-page passed (or forgot) its own
+ *      `fractionDigits` prop, and the pages that forgot rendered a fraction
+ *      of a step. The set below is the metrics whose values are discrete by
+ *      construction: tallies of events, category flags pinned to 1, closed
+ *      integer instrument scores, and integer ordinal levels.
+ *
+ * Deliberately NOT in the integer set: rates and continuous quantities that
+ * merely tend to be logged as whole numbers (bpm, mmHg, kcal, minutes,
+ * metres). A mean of 68.4 bpm is a real quantity; a mean of 104.3 steps is a
+ * real quantity too, but a step is indivisible, so the metric is read as a
+ * count and rendered as one.
+ */
+import { VALUE_RANGES } from "@/lib/validations/measurement";
+
+/**
+ * Decimal places used for a metric with no discreteness constraint — the
+ * long-standing default of the stat strip and the coach-read strip.
+ */
+export const DEFAULT_METRIC_FRACTION_DIGITS = 1;
+
+/**
+ * Metrics whose stored values are whole numbers by construction. Keys are
+ * `MeasurementType` values; typed as strings so client components can ask
+ * without importing the Prisma client into the browser bundle.
+ */
+export const INTEGER_VALUED_MEASUREMENT_TYPES: ReadonlySet<string> = new Set([
+  // Tallies — a fraction of one of these does not exist.
+  "ACTIVITY_STEPS",
+  "FLIGHTS_CLIMBED",
+  "FALL_COUNT",
+  "BREATHING_DISTURBANCES",
+  "SLEEP_DISTURBANCE_COUNT",
+  // Category events — the row carries a fixed `value = 1` (one fired event).
+  "AUDIO_EXPOSURE_EVENT",
+  "BREATHING_DISTURBANCE_EVENT",
+  "HIGH_HEART_RATE_EVENT",
+  "IRREGULAR_RHYTHM_NOTIFICATION",
+  "LOW_HEART_RATE_EVENT",
+  "WALKING_STEADINESS_EVENT",
+  // Closed integer instrument scores — the questionnaire sums whole items.
+  "PAIN_NRS",
+  "PHQ9_SCORE",
+  "GAD7_SCORE",
+  "WHO5_SCORE",
+  "SCI_SCORE",
+  // Integer ordinal / rating scales.
+  "RESILIENCE",
+  "VISCERAL_FAT",
+  // Whole years, as the device reports it.
+  "VASCULAR_AGE",
+]);
+
+/**
+ * True when the metric's own plausibility floor forbids a negative value.
+ * Unknown types answer `false` — an absent range is an absent fact, never a
+ * guessed one.
+ */
+export function isNonNegativeMetric(type: string | null | undefined): boolean {
+  if (!type) return false;
+  const range = VALUE_RANGES[type];
+  return range !== undefined && range.min >= 0;
+}
+
+/**
+ * True when EVERY named metric forbids negative values (and at least one was
+ * named). Used by the chart, which can paint several series in one axis: a
+ * single signed series keeps the full downward padding for all of them.
+ */
+export function areAllNonNegativeMetrics(
+  types: readonly (string | null | undefined)[],
+): boolean {
+  return types.length > 0 && types.every((type) => isNonNegativeMetric(type));
+}
+
+/**
+ * Clamp a DERIVED lower edge (a baseline band edge, a padded axis bound) to
+ * the metric's zero floor. Derived edges are arithmetic — median − k·MAD, a
+ * padded minimum — and arithmetic does not know that a step cannot be owed.
+ */
+export function clampDerivedLowerBound(
+  type: string | null | undefined,
+  lower: number,
+): number {
+  return isNonNegativeMetric(type) ? Math.max(0, lower) : lower;
+}
+
+/**
+ * Decimal places a metric's values are read at. Zero for a discrete metric,
+ * the shared default otherwise. Surfaces call this instead of hard-coding a
+ * default, so a page that says nothing still renders the metric correctly.
+ */
+export function metricFractionDigits(type: string | null | undefined): number {
+  if (type && INTEGER_VALUED_MEASUREMENT_TYPES.has(type)) return 0;
+  return DEFAULT_METRIC_FRACTION_DIGITS;
+}
diff --git a/src/lib/validations/measurement.ts b/src/lib/validations/measurement.ts
index 32dbc045f..3cd8ac1bd 100644
--- a/src/lib/validations/measurement.ts
+++ b/src/lib/validations/measurement.ts
@@ -495,6 +495,11 @@ export const VALUE_RANGES: Record<string, { min: number; max: number }> = {
   // the ×100 server-side scaling the canonical band is 0..100.
   WALKING_ASYMMETRY: { min: 0, max: 100 },
   WALKING_DOUBLE_SUPPORT: { min: 0, max: 100 },
+  // Same ×100-scaled 0..100 percent as its two gait siblings above. The
+  // entry was simply missing; the map is the app's plausibility domain AND
+  // (via `value-domain.ts`) the answer to "can this metric be negative",
+  // so an omission reads as "unknown" on both questions.
+  WALKING_STEADINESS: { min: 0, max: 100 },
   // ── v1.5.5 iOS-coord follow-up — raw-SI gait pair ──
   // Step length (metres) — adult walking sits around 0.5–0.8 m; the
   // 0.1 floor captures shuffling gait and the 2.0 ceiling covers
@@ -541,6 +546,14 @@ export const VALUE_RANGES: Record<string, { min: number; max: number }> = {
   LOW_HEART_RATE_EVENT: { min: 1, max: 1 },
   WALKING_STEADINESS_EVENT: { min: 1, max: 1 },
   BREATHING_DISTURBANCE_EVENT: { min: 1, max: 1 },
+  // Loud-listening event flag (env + headphone). One fired event per row, so
+  // the floor is 1 — a non-event is not stored. The entry was missing from
+  // the map entirely, which let ANY number through ingest, including a
+  // negative one. The ceiling stays generous rather than pinned at 1 like the
+  // five events above: this type is written only by the iOS client and
+  // nothing in this repo asserts the exact value, so the floor is the part
+  // that is certain.
+  AUDIO_EXPOSURE_EVENT: { min: 1, max: 1000 },
   // ── v1.10.0 — computed scores (WX-C) ──
   // Server-derived 0–100 scores. The plausibility band pins them to the
   // score range so a malformed store (a stray negative or > 100) is rejected.