fix(cycle): read basal temperature and the unit-bearing chart titles in the reader's units

The basal body temperature field, its chart and its tooltip were fixed to degrees Celsius whatever the reader had chosen: the placeholder said °C, the field accepted only 30-45, the chart plotted Celsius and the tooltip printed "{temp} °C". Two chart titles carried a fixed unit as well ("Wrist temperature (°C)", "Walking speed (km/h)") above an axis already in the reader's unit. The field now reads and writes in the reader's unit and stores Celsius; a reading the person did not touch is saved back unchanged rather than through a round trip of rounding. The chart plots, pads and labels in the reader's unit, the two titles drop the unit the axis already names, and the cycle contrast's fixed kg, °C and mg/dL labels, which the transform had already replaced, leave the bundles. Refs #1067
2026-11-12 14:16:12 +00:00 · 2026-10-01 13:23:17 +02:00
1 parent 43be8ebd43
commit 0028290117
@@ -3739,7 +3739,7 @@
    "walkingSpeed": {
      "title": "Gehgeschwindigkeit",
      "description": "Deine durchschnittliche Gehgeschwindigkeit im Zeitverlauf, in km/h.",
-      "chartTitle": "Gehgeschwindigkeit (km/h)",
+      "chartTitle": "Gehgeschwindigkeit",
      "emptyState": {
        "title": "Noch keine Gehgeschwindigkeitsdaten",
        "description": "Werte erscheinen hier, sobald Apple Health synchronisiert."
@@ -4142,7 +4142,7 @@
    "wristTemperature": {
      "title": "Handgelenktemperatur",
      "description": "Deine nächtliche Handgelenktemperatur, gemessen an deinem eigenen Ausgangswert.",
-      "chartTitle": "Handgelenktemperatur (°C)",
+      "chartTitle": "Handgelenktemperatur",
      "emptyState": {
        "title": "Noch keine Handgelenktemperatur-Daten",
        "description": "Werte erscheinen hier, sobald Apple Health das nächtliche Tragen synchronisiert."
@@ -8286,9 +8286,6 @@
        "unitSteps": "Schritte",
        "unitBpm": "S/min",
        "unitMs": "ms",
-        "unitKg": "kg",
-        "unitCelsius": "°C",
-        "unitGlucose": "mg/dL",
        "unitMood": "Pkt.",
        "confidenceLow": "Geringe Sicherheit",
        "confidenceMedium": "Mittlere Sicherheit",
@@ -8463,7 +8460,6 @@
      "flow": "Stärke",
      "symptoms": "Symptome",
      "temperature": "Basaltemperatur",
-      "temperaturePlaceholder": "°C",
      "temperatureDisturbed": "Messwert als gestört markieren",
      "temperatureDisturbedHint": "Fieber, Krankheit, Alkohol oder eine späte Messung — wird von der Temperaturauswertung ausgeschlossen.",
      "ovulationTest": "Ovulationstest",
@@ -8555,7 +8551,7 @@
      "empty": "Noch keine Temperaturwerte",
      "emptyHint": "Miss deine Basaltemperatur jeden Morgen, um den Temperaturanstieg deines Zyklus zu sehen.",
      "ovulationEstimate": "Gesch. Eisprung",
-      "tooltipTemp": "{temp} °C",
+      "tooltipTemp": "{temp} {unit}",
      "ovulationConfirmed": "Bestätigter Eisprung"
    },
    "fieldInfo": {
@@ -3739,7 +3739,7 @@
    "walkingSpeed": {
      "title": "Walking Speed",
      "description": "Your average walking speed over time, in km/h.",
-      "chartTitle": "Walking speed (km/h)",
+      "chartTitle": "Walking speed",
      "emptyState": {
        "title": "No walking-speed data yet",
        "description": "Walking-speed readings appear here once Apple Health syncs."
@@ -4142,7 +4142,7 @@
    "wristTemperature": {
      "title": "Wrist Temperature",
      "description": "Your overnight wrist temperature, tracked against your own baseline.",
-      "chartTitle": "Wrist temperature (°C)",
+      "chartTitle": "Wrist temperature",
      "emptyState": {
        "title": "No wrist-temperature data yet",
        "description": "Wrist-temperature readings appear here once Apple Health syncs overnight wear."
@@ -8286,9 +8286,6 @@
        "unitSteps": "steps",
        "unitBpm": "bpm",
        "unitMs": "ms",
-        "unitKg": "kg",
-        "unitCelsius": "°C",
-        "unitGlucose": "mg/dL",
        "unitMood": "pts",
        "confidenceLow": "Low confidence",
        "confidenceMedium": "Medium confidence",
@@ -8463,7 +8460,6 @@
      "flow": "Flow",
      "symptoms": "Symptoms",
      "temperature": "Basal body temperature",
-      "temperaturePlaceholder": "°C",
      "temperatureDisturbed": "Mark reading as disturbed",
      "temperatureDisturbedHint": "Fever, illness, alcohol or a late measurement — excluded from the temperature evaluation.",
      "ovulationTest": "Ovulation test",
@@ -8555,7 +8551,7 @@
      "empty": "No temperature readings yet",
      "emptyHint": "Log your basal body temperature each morning to see your cycle's temperature shift.",
      "ovulationEstimate": "Est. ovulation",
-      "tooltipTemp": "{temp} °C",
+      "tooltipTemp": "{temp} {unit}",
      "ovulationConfirmed": "Confirmed ovulation"
    },
    "fieldInfo": {
@@ -3739,7 +3739,7 @@
    "walkingSpeed": {
      "title": "Velocidad al andar",
      "description": "Tu velocidad media al andar en el tiempo, en km/h.",
-      "chartTitle": "Velocidad al andar (km/h)",
+      "chartTitle": "Velocidad al andar",
      "emptyState": {
        "title": "Aún no hay datos",
        "description": "Las lecturas aparecen aquí cuando Apple Health sincroniza."
@@ -4142,7 +4142,7 @@
    "wristTemperature": {
      "title": "Temperatura de muñeca",
      "description": "Tu temperatura de muñeca durante la noche, comparada con tu valor de referencia.",
-      "chartTitle": "Temperatura de muñeca (°C)",
+      "chartTitle": "Temperatura de muñeca",
      "emptyState": {
        "title": "Aún no hay datos de temperatura de muñeca",
        "description": "Los valores aparecen aquí cuando Apple Health sincroniza el uso nocturno."
@@ -8286,9 +8286,6 @@
        "unitSteps": "pasos",
        "unitBpm": "lpm",
        "unitMs": "ms",
-        "unitKg": "kg",
-        "unitCelsius": "°C",
-        "unitGlucose": "mg/dL",
        "unitMood": "pts",
        "confidenceLow": "Confianza baja",
        "confidenceMedium": "Confianza media",
@@ -8463,7 +8460,6 @@
      "flow": "Flujo",
      "symptoms": "Síntomas",
      "temperature": "Temperatura basal",
-      "temperaturePlaceholder": "°C",
      "temperatureDisturbed": "Marcar la medición como alterada",
      "temperatureDisturbedHint": "Fiebre, enfermedad, alcohol o una medición tardía: se excluye de la evaluación de temperatura.",
      "ovulationTest": "Test de ovulación",
@@ -8555,7 +8551,7 @@
      "empty": "Aún no hay mediciones de temperatura",
      "emptyHint": "Registra tu temperatura basal cada mañana para ver el cambio de temperatura de tu ciclo.",
      "ovulationEstimate": "Ovulación est.",
-      "tooltipTemp": "{temp} °C",
+      "tooltipTemp": "{temp} {unit}",
      "ovulationConfirmed": "Ovulación confirmada"
    },
    "fieldInfo": {
@@ -3739,7 +3739,7 @@
    "walkingSpeed": {
      "title": "Vitesse de marche",
      "description": "Votre vitesse de marche moyenne au fil du temps, en km/h.",
-      "chartTitle": "Vitesse de marche (km/h)",
+      "chartTitle": "Vitesse de marche",
      "emptyState": {
        "title": "Aucune donnée",
        "description": "Les relevés apparaissent ici dès qu’Apple Health se synchronise."
@@ -4142,7 +4142,7 @@
    "wristTemperature": {
      "title": "Température du poignet",
      "description": "Votre température du poignet pendant la nuit, comparée à votre valeur de référence.",
-      "chartTitle": "Température du poignet (°C)",
+      "chartTitle": "Température du poignet",
      "emptyState": {
        "title": "Pas encore de données de température du poignet",
        "description": "Les valeurs apparaissent ici dès qu'Apple Santé synchronise le port nocturne."
@@ -8286,9 +8286,6 @@
        "unitSteps": "pas",
        "unitBpm": "bpm",
        "unitMs": "ms",
-        "unitKg": "kg",
-        "unitCelsius": "°C",
-        "unitGlucose": "mg/dL",
        "unitMood": "pts",
        "confidenceLow": "Confiance faible",
        "confidenceMedium": "Confiance moyenne",
@@ -8463,7 +8460,6 @@
      "flow": "Flux",
      "symptoms": "Symptômes",
      "temperature": "Température basale",
-      "temperaturePlaceholder": "°C",
      "temperatureDisturbed": "Marquer la mesure comme perturbée",
      "temperatureDisturbedHint": "Fièvre, maladie, alcool ou mesure tardive — exclue de l'évaluation de la température.",
      "ovulationTest": "Test d'ovulation",
@@ -8555,7 +8551,7 @@
      "empty": "Pas encore de relevés de température",
      "emptyHint": "Notez votre température basale chaque matin pour voir le décalage de température de votre cycle.",
      "ovulationEstimate": "Ovulation est.",
-      "tooltipTemp": "{temp} °C",
+      "tooltipTemp": "{temp} {unit}",
      "ovulationConfirmed": "Ovulation confirmée"
    },
    "fieldInfo": {
@@ -3739,7 +3739,7 @@
    "walkingSpeed": {
      "title": "Velocità di cammino",
      "description": "La tua velocità media di cammino nel tempo, in km/h.",
-      "chartTitle": "Velocità di cammino (km/h)",
+      "chartTitle": "Velocità di cammino",
      "emptyState": {
        "title": "Nessun dato",
        "description": "Le letture appaiono qui quando Apple Health si sincronizza."
@@ -4142,7 +4142,7 @@
    "wristTemperature": {
      "title": "Temperatura del polso",
      "description": "La temperatura del polso durante la notte, rispetto al tuo valore di riferimento.",
-      "chartTitle": "Temperatura del polso (°C)",
+      "chartTitle": "Temperatura del polso",
      "emptyState": {
        "title": "Nessun dato sulla temperatura del polso",
        "description": "I valori compaiono qui quando Apple Health sincronizza l'uso notturno."
@@ -8286,9 +8286,6 @@
        "unitSteps": "passi",
        "unitBpm": "bpm",
        "unitMs": "ms",
-        "unitKg": "kg",
-        "unitCelsius": "°C",
-        "unitGlucose": "mg/dL",
        "unitMood": "pts",
        "confidenceLow": "Affidabilità bassa",
        "confidenceMedium": "Affidabilità media",
@@ -8463,7 +8460,6 @@
      "flow": "Flusso",
      "symptoms": "Sintomi",
      "temperature": "Temperatura basale",
-      "temperaturePlaceholder": "°C",
      "temperatureDisturbed": "Segna la misurazione come disturbata",
      "temperatureDisturbedHint": "Febbre, malattia, alcol o una misurazione tardiva: esclusa dalla valutazione della temperatura.",
      "ovulationTest": "Test di ovulazione",
@@ -8555,7 +8551,7 @@
      "empty": "Ancora nessuna misurazione della temperatura",
      "emptyHint": "Registra la temperatura basale ogni mattina per vedere il rialzo termico del tuo ciclo.",
      "ovulationEstimate": "Ovulazione stim.",
-      "tooltipTemp": "{temp} °C",
+      "tooltipTemp": "{temp} {unit}",
      "ovulationConfirmed": "Ovulazione confermata"
    },
    "fieldInfo": {
@@ -3739,7 +3739,7 @@
    "walkingSpeed": {
      "title": "보행 속도",
      "description": "시간에 따른 평균 보행 속도예요(km/h).",
-      "chartTitle": "보행 속도(km/h)",
+      "chartTitle": "보행 속도",
      "emptyState": {
        "title": "아직 보행 속도 데이터가 없어요",
        "description": "Apple Health가 동기화되면 보행 속도 측정값이 여기에 나타나요."
@@ -4142,7 +4142,7 @@
    "wristTemperature": {
      "title": "손목 온도",
      "description": "내 기준값과 비교한 밤사이 손목 온도예요.",
-      "chartTitle": "손목 온도 (°C)",
+      "chartTitle": "손목 온도",
      "emptyState": {
        "title": "아직 손목 온도 데이터가 없어요",
        "description": "Apple Health가 밤사이 착용 기록을 동기화하면 손목 온도 측정값이 여기에 표시돼요."
@@ -8286,9 +8286,6 @@
        "unitSteps": "걸음",
        "unitBpm": "bpm",
        "unitMs": "ms",
-        "unitKg": "kg",
-        "unitCelsius": "°C",
-        "unitGlucose": "mg/dL",
        "unitMood": "점",
        "confidenceLow": "신뢰도 낮음",
        "confidenceMedium": "신뢰도 보통",
@@ -8463,7 +8460,6 @@
      "flow": "생리량",
      "symptoms": "증상",
      "temperature": "기초 체온",
-      "temperaturePlaceholder": "°C",
      "temperatureDisturbed": "측정값을 방해받음으로 표시",
      "temperatureDisturbedHint": "발열, 아픈 날, 음주, 늦은 측정 — 체온 평가에서 제외돼요.",
      "ovulationTest": "배란 테스트",
@@ -8555,7 +8551,7 @@
      "empty": "아직 체온 기록이 없어요",
      "emptyHint": "매일 아침 기초 체온을 기록하면 주기의 체온 변화를 볼 수 있어요.",
      "ovulationEstimate": "예상 배란",
-      "tooltipTemp": "{temp}°C",
+      "tooltipTemp": "{temp}{unit}",
      "ovulationConfirmed": "확인된 배란"
    },
    "fieldInfo": {
@@ -3739,7 +3739,7 @@
    "walkingSpeed": {
      "title": "Prędkość chodu",
      "description": "Twoja średnia prędkość chodu w czasie, w km/h.",
-      "chartTitle": "Prędkość chodu (km/h)",
+      "chartTitle": "Prędkość chodu",
      "emptyState": {
        "title": "Brak danych",
        "description": "Odczyty pojawią się tutaj po synchronizacji Apple Health."
@@ -4142,7 +4142,7 @@
    "wristTemperature": {
      "title": "Temperatura nadgarstka",
      "description": "Nocna temperatura nadgarstka, odniesiona do Twojej wartości bazowej.",
-      "chartTitle": "Temperatura nadgarstka (°C)",
+      "chartTitle": "Temperatura nadgarstka",
      "emptyState": {
        "title": "Brak danych o temperaturze nadgarstka",
        "description": "Wartości pojawią się tutaj, gdy Apple Health zsynchronizuje nocne noszenie."
@@ -8286,9 +8286,6 @@
        "unitSteps": "kroki",
        "unitBpm": "ud./min",
        "unitMs": "ms",
-        "unitKg": "kg",
-        "unitCelsius": "°C",
-        "unitGlucose": "mg/dL",
        "unitMood": "pkt",
        "confidenceLow": "Niska pewność",
        "confidenceMedium": "Średnia pewność",
@@ -8463,7 +8460,6 @@
      "flow": "Krwawienie",
      "symptoms": "Objawy",
      "temperature": "Podstawowa temperatura ciała",
-      "temperaturePlaceholder": "°C",
      "temperatureDisturbed": "Oznacz pomiar jako zakłócony",
      "temperatureDisturbedHint": "Gorączka, choroba, alkohol lub spóźniony pomiar — wykluczony z oceny temperatury.",
      "ovulationTest": "Test owulacyjny",
@@ -8555,7 +8551,7 @@
      "empty": "Brak pomiarów temperatury",
      "emptyHint": "Zapisuj podstawową temperaturę ciała każdego ranka, aby zobaczyć przesunięcie temperatury w cyklu.",
      "ovulationEstimate": "Szac. owulacja",
-      "tooltipTemp": "{temp} °C",
+      "tooltipTemp": "{temp} {unit}",
      "ovulationConfirmed": "Potwierdzona owulacja"
    },
    "fieldInfo": {
@@ -0,0 +1,42 @@
+/**
+ * A real `UnitDisplay` for one fixed preference, for component tests that
+ * render without a QueryClient (`useUnitDisplay` reads the account through
+ * react-query). Built on the production transforms, so a test asserts the
+ * same numbers and symbols the hook would give.
+ *
+ *   vi.mock("@/hooks/use-unit-display", async () => {
+ *     const { unitDisplayFor } = await import("@/__tests__/helpers/unit-display-mock");
+ *     return { useUnitDisplay: () => unitDisplayFor("metric") };
+ *   });
+ */
+import type { UnitDisplay } from "@/hooks/use-unit-display";
+import type { GlucoseUnit } from "@/lib/glucose";
+import {
+  applyDisplayTransform,
+  applyDisplayTransformDelta,
+  getDisplayTransform,
+  hasDisplayTransform,
+  invertDisplayTransform,
+  type UnitPreference,
+} from "@/lib/measurements/display-transform";
+
+export function unitDisplayFor(
+  preference: UnitPreference,
+  glucoseUnit: GlucoseUnit = "mg/dL",
+): UnitDisplay {
+  // The hook resolves mass, length and temperature through the
+  // metric/imperial branch alone; glucose is converted where it renders.
+  const forType = (type: string) => getDisplayTransform(type, preference);
+  return {
+    preference,
+    glucoseUnit,
+    transformFor: forType,
+    toDisplay: (type, value) => applyDisplayTransform(value, forType(type)),
+    fromDisplay: (type, value) => invertDisplayTransform(value, forType(type)),
+    toDisplayDelta: (type, value) =>
+      applyDisplayTransformDelta(value, forType(type)),
+    unitFor: (type) => forType(type).displayUnit,
+    decimalsFor: (type) => forType(type).decimals,
+    isTransformed: (type) => hasDisplayTransform(type),
+  };
+}
@@ -87,7 +87,6 @@ const LEGIT_IDENTICAL = new Set<string>([
  "common.period",
  // Clinical abbreviations / SI units — identical across locales.
  "charts.vo2Max",
-  "cycle.insights.crosstab.unitGlucose",
  "dashboard.metric.unit.bmi",
  "dashboard.metric.unit.mood",
  "dashboard.metric.unit.glucose",
@@ -1,7 +1,20 @@
-import { describe, it, expect } from "vitest";
+import { describe, it, expect, vi } from "vitest";
 import { renderToStaticMarkup } from "react-dom/server";

-import { BbtChart } from "../bbt-chart";
+// `useUnitDisplay` reads the account through react-query; these static
+// renders have no QueryClient, so the hook is a real display for a fixed
+// preference the test sets.
+const reader = vi.hoisted(() => ({
+  preference: "metric" as "metric" | "imperial",
+}));
+vi.mock("@/hooks/use-unit-display", async () => {
+  const { unitDisplayFor } =
+    await import("@/__tests__/helpers/unit-display-mock");
+  return { useUnitDisplay: () => unitDisplayFor(reader.preference) };
+});
+
+import { BbtChart, BbtTooltip, bbtPoints } from "../bbt-chart";
+import { unitDisplayFor } from "@/__tests__/helpers/unit-display-mock";
 import { I18nProvider } from "@/lib/i18n/context";
 import type { CalendarDay } from "../types";

@@ -82,3 +95,46 @@ describe("<BbtChart>", () => {
    expect(html).toContain('data-slot="cycle-bbt-caption"');
  });
 });
+
+describe("<BbtChart> — the reader's temperature unit", () => {
+  it("plots each reading in °F for an imperial reader", () => {
+    const display = unitDisplayFor("imperial");
+    const points = bbtPoints({
+      days: [
+        day("2026-06-05", { basalBodyTempC: 36.5 }),
+        day("2026-06-09", { basalBodyTempC: 36.9 }),
+      ],
+      fromDate: "2026-06-01",
+      today: "2026-06-10",
+      rawChartMode: false,
+      toDisplay: (c) => display.toDisplay("BODY_TEMPERATURE", c),
+    });
+    expect(points.map((p) => p.temp)).toEqual([97.7, 98.4]);
+  });
+
+  it("labels the tooltip with the reader's unit", () => {
+    reader.preference = "imperial";
+    try {
+      const html = render(
+        <BbtTooltip
+          active
+          payload={[
+            {
+              payload: {
+                t: Date.parse("2026-06-09T12:00:00Z"),
+                temp: 98.4,
+                phaseHue: "red",
+                mucus: null,
+                ovulationTest: null,
+              },
+            },
+          ]}
+        />,
+      );
+      expect(html).toContain("98.4 °F");
+      expect(html).not.toContain("°C");
+    } finally {
+      reader.preference = "metric";
+    }
+  });
+});
@@ -7,6 +7,14 @@
 import { describe, it, expect, vi } from "vitest";
 import { renderToStaticMarkup } from "react-dom/server";

+// The BBT chart reads the unit preference through react-query; no
+// QueryClient here, so a fixed metric display stands in.
+vi.mock("@/hooks/use-unit-display", async () => {
+  const { unitDisplayFor } =
+    await import("@/__tests__/helpers/unit-display-mock");
+  return { useUnitDisplay: () => unitDisplayFor("metric") };
+});
+
 vi.mock("next/navigation", () => ({
  useSearchParams: () => new URLSearchParams(),
 }));
@@ -3,6 +3,7 @@ import { describe, it, expect } from "vitest";
 import {
  buildDayLogPatch,
  buildDayLogInput,
+  bbtTextToCelsius,
  symptomsCount,
  temperatureCount,
  intimacyCount,
@@ -330,3 +331,30 @@ describe("sheetDayContext (#1004)", () => {
    expect(ctx.periodEndable).toBe(true);
  });
 });
+
+describe("bbtTextToCelsius — the field reads in the reader's unit", () => {
+  const fromFahrenheit = (f: number) => (f - 32) / 1.8;
+
+  it("stores a typed Fahrenheit reading as Celsius", () => {
+    expect(bbtTextToCelsius("98.2", null, fromFahrenheit)).toBe(36.78);
+  });
+
+  it("returns the stored value for text the sheet seeded, so a save never drifts it", () => {
+    const seed = { text: "98.2", celsius: 36.75 };
+    expect(bbtTextToCelsius("98.2", seed, fromFahrenheit)).toBe(36.75);
+    expect(bbtTextToCelsius("98.4", seed, fromFahrenheit)).toBe(36.89);
+  });
+
+  it("is null for an empty or unreadable field", () => {
+    expect(bbtTextToCelsius("", null, fromFahrenheit)).toBeNull();
+    expect(bbtTextToCelsius("abc", null, fromFahrenheit)).toBeNull();
+  });
+
+  it("feeds the payload through the converter it is given", () => {
+    const patch = buildDayLogPatch({ ...blank(), bbt: "98.2" }, (text) =>
+      bbtTextToCelsius(text, null, fromFahrenheit),
+    );
+    expect(patch.basalBodyTempC).toBe(36.78);
+    expect(patch.temperatureExcluded).toBe(false);
+  });
+});
@@ -40,6 +40,7 @@ import {
 import { Card, CardContent, CardHeader } from "@/components/ui/card";
 import { TileHeader } from "@/components/insights/tile-header";
 import { useTranslations, useFormatters } from "@/lib/i18n/context";
+import { useUnitDisplay } from "@/hooks/use-unit-display";
 import { prefersReducedMotion } from "@/lib/charts/reduced-motion";
 import { cn } from "@/lib/utils";
 import type { CalendarDay, CervicalMucus, OvulationTest } from "./types";
@@ -81,6 +82,39 @@ function ymdToMs(d: string): number {
  return Date.parse(`${d}T12:00:00Z`);
 }

+/**
+ * The plotted readings of the window, oldest first, each temperature in the
+ * reader's unit (`toDisplay` converts the stored degrees Celsius).
+ */
+export function bbtPoints(args: {
+  days: CalendarDay[];
+  fromDate: string;
+  today: string;
+  rawChartMode: boolean;
+  toDisplay: (celsius: number) => number;
+}): BbtPoint[] {
+  const { days, fromDate, today, rawChartMode, toDisplay } = args;
+  const fromMs = ymdToMs(fromDate);
+  const todayMs = ymdToMs(today);
+  return days
+    .filter((d) => {
+      if (d.basalBodyTempC == null || !Number.isFinite(d.basalBodyTempC)) {
+        return false;
+      }
+      const ms = ymdToMs(d.date);
+      return ms >= fromMs && ms <= todayMs;
+    })
+    .map((d) => ({
+      t: ymdToMs(d.date),
+      temp: toDisplay(d.basalBodyTempC as number),
+      phaseHue:
+        rawChartMode || d.phase == null ? LINE_COLOR : PHASE_HUE[d.phase],
+      mucus: d.cervicalMucus,
+      ovulationTest: d.ovulationTest,
+    }))
+    .sort((a, b) => a.t - b.t);
+}
+
 export function BbtChart({
  days,
  today,
@@ -91,6 +125,9 @@ export function BbtChart({
 }: BbtChartProps) {
  const { t } = useTranslations();
  const fmt = useFormatters();
+  // Stored in °C, read in the reader's unit: every point, the padding and
+  // the empty-state domain go through the same transform.
+  const unitDisplay = useUnitDisplay();
  const animationsEnabled = !prefersReducedMotion();

  // Scope to the current cycle using the server's resolved start; fall back to
@@ -101,27 +138,18 @@ export function BbtChart({
    return shiftDateKey(today, -FALLBACK_WINDOW_DAYS);
  }, [cycleStartDate, today]);

-  const points = useMemo<BbtPoint[]>(() => {
-    const fromMs = ymdToMs(fromDate);
-    const todayMs = ymdToMs(today);
-    return days
-      .filter((d) => {
-        if (d.basalBodyTempC == null || !Number.isFinite(d.basalBodyTempC)) {
-          return false;
-        }
-        const ms = ymdToMs(d.date);
-        return ms >= fromMs && ms <= todayMs;
-      })
-      .map((d) => ({
-        t: ymdToMs(d.date),
-        temp: d.basalBodyTempC as number,
-        phaseHue:
-          rawChartMode || d.phase == null ? LINE_COLOR : PHASE_HUE[d.phase],
-        mucus: d.cervicalMucus,
-        ovulationTest: d.ovulationTest,
-      }))
-      .sort((a, b) => a.t - b.t);
-  }, [days, fromDate, today, rawChartMode]);
+  const points = useMemo(
+    () =>
+      bbtPoints({
+        days,
+        fromDate,
+        today,
+        rawChartMode,
+        toDisplay: (celsius) =>
+          unitDisplay.toDisplay("BODY_TEMPERATURE", celsius),
+      }),
+    [days, fromDate, today, rawChartMode, unitDisplay],
+  );

  const ovulationMs = useMemo(() => {
    if (rawChartMode || !predictedOvulation) return null;
@@ -133,16 +161,23 @@ export function BbtChart({
  }, [predictedOvulation, points, rawChartMode]);

  const yDomain = useMemo<[number, number]>(() => {
-    if (points.length === 0) return [36, 37.5];
+    if (points.length === 0) {
+      return [
+        unitDisplay.toDisplay("BODY_TEMPERATURE", 36),
+        unitDisplay.toDisplay("BODY_TEMPERATURE", 37.5),
+      ];
+    }
    const temps = points.map((p) => p.temp);
    const min = Math.min(...temps);
    const max = Math.max(...temps);
-    // Pad ±0.15 °C so the shift is legible and the line never hugs an edge.
+    // Pad by 0.15 °C (in the reader's unit) so the shift is legible and the
+    // line never hugs an edge.
+    const pad = unitDisplay.toDisplayDelta("BODY_TEMPERATURE", 0.15);
    return [
-      Math.floor((min - 0.15) * 10) / 10,
-      Math.ceil((max + 0.15) * 10) / 10,
+      Math.floor((min - pad) * 10) / 10,
+      Math.ceil((max + pad) * 10) / 10,
    ];
-  }, [points]);
+  }, [points, unitDisplay]);

  const ticks = useMemo(() => {
    if (points.length < 2) return [];
@@ -279,12 +314,13 @@ function PhaseDot(props: { cx?: number; cy?: number; payload?: BbtPoint }) {
 }

 /** Tooltip restating the temperature + any fertility signs logged that day. */
-function BbtTooltip(props: {
+export function BbtTooltip(props: {
  active?: boolean;
  payload?: { payload: BbtPoint }[];
 }) {
  const { t } = useTranslations();
  const fmt = useFormatters();
+  const unitDisplay = useUnitDisplay();
  if (!props.active || !props.payload || props.payload.length === 0)
    return null;
  const p = props.payload[0].payload;
@@ -298,7 +334,10 @@ function BbtTooltip(props: {
        {fmt.dateShortSmart(new Date(p.t))}
      </p>
      <p className="text-foreground font-medium tabular-nums">
-        {t("cycle.bbt.tooltipTemp", { temp: fmt.number(p.temp) })}
+        {t("cycle.bbt.tooltipTemp", {
+          temp: fmt.number(p.temp),
+          unit: unitDisplay.unitFor("BODY_TEMPERATURE"),
+        })}
      </p>
      {p.mucus ? (
        <p className="text-muted-foreground mt-0.5">
@@ -55,14 +55,16 @@ const METRIC_LABEL_KEY: Record<string, string> = {
  mood: "cycle.insights.crosstab.metricMood",
 };

-const UNIT_KEY: Record<CyclePhaseCrosstabDisplay, string> = {
+/**
+ * Bundle labels for the displays no preference changes. Weight, the
+ * temperatures and glucose take their symbol from the reader's transform
+ * (`DISPLAY_TO_TYPE` below) and have no bundle label to fall back on.
+ */
+const UNIT_KEY: Partial<Record<CyclePhaseCrosstabDisplay, string>> = {
  hours: "cycle.insights.crosstab.unitHours",
  steps: "cycle.insights.crosstab.unitSteps",
  bpm: "cycle.insights.crosstab.unitBpm",
  ms: "cycle.insights.crosstab.unitMs",
-  kg: "cycle.insights.crosstab.unitKg",
-  celsius: "cycle.insights.crosstab.unitCelsius",
-  glucose: "cycle.insights.crosstab.unitGlucose",
  mood: "cycle.insights.crosstab.unitMood",
 };

@@ -45,6 +45,7 @@ import {
 import { ResponsiveSheet } from "@/components/ui/responsive-sheet";
 import { SheetSection, SheetSectionCount } from "@/components/ui/sheet-section";
 import { useTranslations } from "@/lib/i18n/context";
+import { useUnitDisplay } from "@/hooks/use-unit-display";
 import { resolveIntlLocale } from "@/lib/format-locale";
 import type { Locale } from "@/lib/i18n/config";
 import { CUSTOM_SYMPTOM_ICON_ALLOWLIST } from "@/lib/cycle/custom-symptoms-shared";
@@ -188,6 +189,23 @@ function resolveBbt(bbt: string): number | null {
  return n != null && Number.isFinite(n) ? n : null;
 }

+/**
+ * The temperature field's text, typed in the reader's unit, as the stored
+ * degrees Celsius (two decimals, the field's own step). Text equal to what
+ * the sheet seeded returns the stored value untouched: converting it there
+ * and back would move a reading the person never edited.
+ */
+export function bbtTextToCelsius(
+  text: string,
+  seed: { text: string; celsius: number } | null,
+  toCelsius: (typed: number) => number,
+): number | null {
+  const typed = resolveBbt(text);
+  if (typed == null) return null;
+  if (seed && text === seed.text) return seed.celsius;
+  return Math.round(toCelsius(typed) * 100) / 100;
+}
+
 function symptomList(
  symptoms: Map<string, number | null>,
 ): CycleSymptomSelection[] {
@@ -202,13 +220,22 @@ function symptomList(
 * deselected so the server clears it (the POST merge can only add/keep — QA
 * W-2). Pure + exported for the unit test.
 */
-export function buildDayLogPatch(s: DayLogFormState): CycleDayLogPatch {
+export function buildDayLogPatch(
+  s: DayLogFormState,
+  /**
+   * The typed temperature (in the reader's unit) as stored degrees Celsius.
+   * The sheet passes the preference-bound conversion; the default reads the
+   * field as Celsius.
+   */
+  bbtToCelsius: (bbt: string) => number | null = resolveBbt,
+): CycleDayLogPatch {
+  const bbtC = bbtToCelsius(s.bbt);
  return {
    flow: s.flow ?? null,
    intermenstrualBleeding: s.intermenstrual,
-    basalBodyTempC: resolveBbt(s.bbt),
+    basalBodyTempC: bbtC,
    // Only meaningful with a BBT present; a cleared reading resets the flag.
-    temperatureExcluded: resolveBbt(s.bbt) != null ? s.bbtDisturbed : false,
+    temperatureExcluded: bbtC != null ? s.bbtDisturbed : false,
    ovulationTest: s.opk ?? null,
    cervicalMucus: s.mucus ?? null,
    cervixPosition: s.cervixPosition ?? null,
@@ -229,8 +256,10 @@ export function buildDayLogPatch(s: DayLogFormState): CycleDayLogPatch {
 export function buildDayLogInput(
  s: DayLogFormState,
  date: string,
+  /** See `buildDayLogPatch`. */
+  bbtToCelsius: (bbt: string) => number | null = resolveBbt,
 ): CycleDayLogInput {
-  const bbtVal = resolveBbt(s.bbt);
+  const bbtVal = bbtToCelsius(s.bbt);
  return {
    date,
    loggedAt: new Date().toISOString(),
@@ -619,6 +648,18 @@ export function LogDaySheet({
    new Map(),
  );
  const [bbt, setBbt] = useState<string>("");
+  // The temperature field reads and writes in the reader's unit; storage is
+  // degrees Celsius. The seeded text keeps its stored value, so saving an
+  // untouched reading never drifts it through a round trip of rounding.
+  const unitDisplay = useUnitDisplay();
+  const [bbtSeed, setBbtSeed] = useState<{
+    text: string;
+    celsius: number;
+  } | null>(null);
+  const bbtToCelsius = (text: string): number | null =>
+    bbtTextToCelsius(text, bbtSeed, (typed) =>
+      unitDisplay.fromDisplay("BODY_TEMPERATURE", typed),
+    );
  const [bbtDisturbed, setBbtDisturbed] = useState(false);
  const [opk, setOpk] = useState<OvulationTest | null>(null);
  const [mucus, setMucus] = useState<CervicalMucus | null>(null);
@@ -666,7 +707,16 @@ export function LogDaySheet({
    setFlow((dto?.flow ?? null) as FlowLevel | null);
    setIntermenstrual(dto?.intermenstrualBleeding ?? false);
    setSymptoms(new Map((dto?.symptoms ?? []).map((s) => [s.key, s.severity])));
-    setBbt(dto?.basalBodyTempC != null ? String(dto.basalBodyTempC) : "");
+    const seededBbt =
+      dto?.basalBodyTempC != null
+        ? String(unitDisplay.toDisplay("BODY_TEMPERATURE", dto.basalBodyTempC))
+        : "";
+    setBbt(seededBbt);
+    setBbtSeed(
+      dto?.basalBodyTempC != null
+        ? { text: seededBbt, celsius: dto.basalBodyTempC }
+        : null,
+    );
    setBbtDisturbed(dto?.temperatureExcluded ?? false);
    setOpk((dto?.ovulationTest ?? null) as OvulationTest | null);
    setMucus((dto?.cervicalMucus ?? null) as CervicalMucus | null);
@@ -753,10 +803,12 @@ export function LogDaySheet({
        // chip actually CLEARS (the POST merge can only add/keep — QA W-2).
        await patchDay.mutateAsync({
          id: currentRowId,
-          patch: buildDayLogPatch(formState),
+          patch: buildDayLogPatch(formState, bbtToCelsius),
        });
      } else {
-        await logDay.mutateAsync(buildDayLogInput(formState, date));
+        await logDay.mutateAsync(
+          buildDayLogInput(formState, date, bbtToCelsius),
+        );
      }
      onOpenChange(false);
    } catch {
@@ -1041,11 +1093,11 @@ export function LogDaySheet({
            type="number"
            inputMode="decimal"
            step="0.01"
-            min={30}
-            max={45}
+            min={unitDisplay.toDisplay("BODY_TEMPERATURE", 30)}
+            max={unitDisplay.toDisplay("BODY_TEMPERATURE", 45)}
            value={bbt}
            onChange={(e) => setBbt(e.target.value)}
-            placeholder={t("cycle.sheet.temperaturePlaceholder")}
+            placeholder={unitDisplay.unitFor("BODY_TEMPERATURE")}
            className="w-32"
            aria-label={t("cycle.sheet.temperature")}
          />