feat(insights): derived framing for additive HealthKit metrics

Register four new derived metrics for the additive HealthKit signals:

- WRIST_TEMPERATURE_BASELINE, STAIR_ASCENT_SPEED_BASELINE,
  STAIR_DESCENT_SPEED_BASELINE — any-user-baseline personal bands reusing
  the type-generic median +/- k*MAD engine via a new BASELINE_CAPABLE_TYPES
  allowlist. Wrist temperature is a personal-deviation band only (no illness
  or cycle inference); stair speeds are personal trend bands (no population
  cutoff, geometry-confounded).
- SIX_MINUTE_WALK_BAND — passthrough re-frame placing the device-estimated
  distance against the Enright & Sherrill 1998 predicted 6MWD (ATS 2002
  test standard), as percent-of-predicted with a green/yellow/red band;
  band null when age/height/weight/sex are incomplete.

Fall count and the breathing-disturbance index stay trend-only by design,
documented in the registry: fall count is a zero-inflated discrete safety
event, the breathing index is a regulated screening signal where a derived
band would imply a diagnosis.

Note wrist temperature as a deferred correlation outcome channel held
pending a privacy review (cycle-phase inference risk), mirroring the
medication-compliance omission note.

Add provenance + standards entries, method/caveat copy across all six
locales, and tests for the engine routing, the Enright equation, and the
percent-of-predicted band.

messages/de.json

@@ -2621,6 +2621,22 @@
           "method": "Ein nächtlicher 0–100-Belastungs-Proxy aus deiner herzfrequenzgewichteten Aktivitätslast (ein TRIMP-ähnliches Trainingsimpuls-Modell). Höher heißt ein anstrengenderer Tag.",
           "caveat": "Ein beschreibender Aktivitätslast-Proxy, kein klinisches oder trainingsgerechtes Lastmaß.",
           "description": "Ein nächtlicher Aktivitätslast-Proxy aus deiner herzfrequenzgewichteten Anstrengung."
+        },
+        "WRIST_TEMPERATURE_BASELINE": {
+          "method": "Deine typische nächtliche Handgelenkstemperatur ist der Median deiner nächtlichen Messwerte im Zeitraum, ± einer robusten Streuung (skalierte mittlere absolute Abweichung). Sie folgt DEINEN Werten — letzte Nacht wird als Abweichung von deiner eigenen Baseline gezeigt, nicht von einer Bevölkerungsnorm.",
+          "caveat": "Nur ein persönliches Abweichungsband — beschreibend, kein Anzeichen für Krankheit, Fieber oder Zyklusphase. Du interpretierst es selbst."
+        },
+        "STAIR_ASCENT_SPEED_BASELINE": {
+          "method": "Dein typisches Treppensteig-Tempo ist der Median deiner Tageswerte im Zeitraum, ± einer robusten Streuung (skalierte mittlere absolute Abweichung). Das Band wird aus deinen Daten gebildet — es gibt keinen Bevölkerungs-Grenzwert für Treppentempo, da es von Treppengeometrie und Beinlänge abhängt.",
+          "caveat": "Ein persönliches Mobilitäts-Trendband — beschreibend, keine Gebrechlichkeits- oder Sturzrisiko-Bewertung."
+        },
+        "STAIR_DESCENT_SPEED_BASELINE": {
+          "method": "Dein typisches Treppen-Abstiegstempo ist der Median deiner Tageswerte im Zeitraum, ± einer robusten Streuung (skalierte mittlere absolute Abweichung). Das Band wird aus deinen Daten gebildet — es gibt keinen Bevölkerungs-Grenzwert für Treppentempo, da es von Treppengeometrie und Beinlänge abhängt.",
+          "caveat": "Ein persönliches Mobilitäts-Trendband — beschreibend, keine Gebrechlichkeits- oder Sturzrisiko-Bewertung."
+        },
+        "SIX_MINUTE_WALK_BAND": {
+          "method": "Die von deinem Gerät GESCHÄTZTE 6-Minuten-Gehstrecke, eingeordnet gegen die Referenz von Enright & Sherrill für Alter, Größe, Gewicht und Geschlecht, als Prozent des Vorhersagewerts. Die Strecke ist die Schätzung des Geräts — hier nie neu berechnet. Ohne Alter, Größe, Gewicht und Geschlecht wird der Prozentwert ausgeblendet und nur Strecke und Trend gezeigt.",
+          "caveat": "Eine gegen eine veröffentlichte Referenz neu eingeordnete Schätzung — ein Hinweis zur funktionellen Kapazität, kein klinischer 6-Minuten-Gehtest und keine Diagnose."
         }
       },
       "scores": {

messages/en.json

@@ -2621,6 +2621,22 @@
           "method": "A nightly 0–100 strain proxy from your heart-rate-weighted activity load (a TRIMP-style training-impulse model). Higher means a harder day.",
           "caveat": "A descriptive activity-load proxy, not a clinical or training-grade load measure.",
           "description": "A nightly activity-load proxy from your heart-rate-weighted effort."
+        },
+        "WRIST_TEMPERATURE_BASELINE": {
+          "method": "Your typical overnight wrist temperature is the median of your nightly readings over the window, ± a robust spread (median absolute deviation, scaled). It tracks YOUR readings — last night is shown as a deviation from your own baseline, not a population norm.",
+          "caveat": "A personal-deviation band only — descriptive, not an illness, fever or cycle-phase signal. Interpret it yourself."
+        },
+        "STAIR_ASCENT_SPEED_BASELINE": {
+          "method": "Your typical stair-climbing pace is the median of your daily values over the window, ± a robust spread (median absolute deviation, scaled). The band is built from your data — there is no population stair-speed cut-off, because pace depends on stair geometry and leg length.",
+          "caveat": "A personal mobility-trend band — descriptive, not a frailty or fall-risk assessment."
+        },
+        "STAIR_DESCENT_SPEED_BASELINE": {
+          "method": "Your typical stair-descent pace is the median of your daily values over the window, ± a robust spread (median absolute deviation, scaled). The band is built from your data — there is no population stair-speed cut-off, because pace depends on stair geometry and leg length.",
+          "caveat": "A personal mobility-trend band — descriptive, not a frailty or fall-risk assessment."
+        },
+        "SIX_MINUTE_WALK_BAND": {
+          "method": "Your device's ESTIMATED six-minute-walk distance placed against the Enright & Sherrill reference for your age, height, weight and sex, as a percent of predicted. The distance is the device's estimate — never recomputed here. Without your age, height, weight and sex the percent is hidden and only the distance and trend are shown.",
+          "caveat": "An estimate re-framed against a published reference — a functional-capacity awareness signal, not a clinical 6-minute-walk test or a diagnosis."
         }
       },
       "scores": {

messages/es.json

@@ -2621,6 +2621,22 @@
           "method": "Un indicador nocturno de esfuerzo de 0 a 100 a partir de tu carga de actividad ponderada por frecuencia cardíaca (un modelo de impulso de entrenamiento tipo TRIMP). Más alto significa un día más exigente.",
           "caveat": "Un indicador descriptivo de carga de actividad, no una medida de carga clínica ni de nivel de entrenamiento.",
           "description": "Un indicador nocturno de carga de actividad a partir de tu esfuerzo ponderado por frecuencia cardíaca."
+        },
+        "WRIST_TEMPERATURE_BASELINE": {
+          "method": "Tu temperatura típica de muñeca durante la noche es la mediana de tus lecturas nocturnas en el periodo, ± una dispersión robusta (desviación absoluta de la mediana, escalada). Sigue TUS lecturas: la noche pasada se muestra como una desviación respecto a tu propia base, no a una norma poblacional.",
+          "caveat": "Solo una banda de desviación personal: descriptiva, no una señal de enfermedad, fiebre ni fase del ciclo. Tú la interpretas."
+        },
+        "STAIR_ASCENT_SPEED_BASELINE": {
+          "method": "Tu ritmo típico al subir escaleras es la mediana de tus valores diarios en el periodo, ± una dispersión robusta (desviación absoluta de la mediana, escalada). La banda se construye con tus datos: no hay un umbral poblacional de velocidad en escaleras, porque el ritmo depende de la geometría de la escalera y la longitud de las piernas.",
+          "caveat": "Una banda personal de tendencia de movilidad: descriptiva, no una evaluación de fragilidad ni de riesgo de caídas."
+        },
+        "STAIR_DESCENT_SPEED_BASELINE": {
+          "method": "Tu ritmo típico al bajar escaleras es la mediana de tus valores diarios en el periodo, ± una dispersión robusta (desviación absoluta de la mediana, escalada). La banda se construye con tus datos: no hay un umbral poblacional de velocidad en escaleras, porque el ritmo depende de la geometría de la escalera y la longitud de las piernas.",
+          "caveat": "Una banda personal de tendencia de movilidad: descriptiva, no una evaluación de fragilidad ni de riesgo de caídas."
+        },
+        "SIX_MINUTE_WALK_BAND": {
+          "method": "La distancia ESTIMADA de marcha de seis minutos de tu dispositivo situada frente a la referencia de Enright y Sherrill para tu edad, estatura, peso y sexo, como porcentaje de lo previsto. La distancia es la estimación del dispositivo: nunca se recalcula aquí. Sin tu edad, estatura, peso y sexo se oculta el porcentaje y solo se muestran la distancia y la tendencia.",
+          "caveat": "Una estimación reformulada frente a una referencia publicada: una señal de capacidad funcional, no una prueba clínica de marcha de seis minutos ni un diagnóstico."
         }
       },
       "scores": {

messages/fr.json

@@ -2621,6 +2621,22 @@
           "method": "Un indice d’effort nocturne de 0 à 100 à partir de votre charge d’activité pondérée par la fréquence cardiaque (un modèle d’impulsion d’entraînement de type TRIMP). Plus élevé signifie une journée plus exigeante.",
           "caveat": "Un indicateur descriptif de charge d’activité, pas une mesure de charge clinique ou de niveau d’entraînement.",
           "description": "Un indice de charge d’activité nocturne à partir de votre effort pondéré par la fréquence cardiaque."
+        },
+        "WRIST_TEMPERATURE_BASELINE": {
+          "method": "Votre température nocturne typique au poignet est la médiane de vos relevés nocturnes sur la période, ± une dispersion robuste (écart absolu médian, mis à l’échelle). Elle suit VOS relevés — la nuit dernière est affichée comme un écart par rapport à votre propre référence, pas à une norme de population.",
+          "caveat": "Une simple bande d’écart personnel — descriptive, ni un signe de maladie, de fièvre ou de phase du cycle. À vous de l’interpréter."
+        },
+        "STAIR_ASCENT_SPEED_BASELINE": {
+          "method": "Votre allure typique en montant les escaliers est la médiane de vos valeurs quotidiennes sur la période, ± une dispersion robuste (écart absolu médian, mis à l’échelle). La bande est construite à partir de vos données — il n’existe pas de seuil de population pour l’allure dans les escaliers, car elle dépend de la géométrie des marches et de la longueur des jambes.",
+          "caveat": "Une bande personnelle de tendance de mobilité — descriptive, ni une évaluation de fragilité ni de risque de chute."
+        },
+        "STAIR_DESCENT_SPEED_BASELINE": {
+          "method": "Votre allure typique en descendant les escaliers est la médiane de vos valeurs quotidiennes sur la période, ± une dispersion robuste (écart absolu médian, mis à l’échelle). La bande est construite à partir de vos données — il n’existe pas de seuil de population pour l’allure dans les escaliers, car elle dépend de la géométrie des marches et de la longueur des jambes.",
+          "caveat": "Une bande personnelle de tendance de mobilité — descriptive, ni une évaluation de fragilité ni de risque de chute."
+        },
+        "SIX_MINUTE_WALK_BAND": {
+          "method": "La distance de marche de six minutes ESTIMÉE par votre appareil, située par rapport à la référence d’Enright et Sherrill pour votre âge, votre taille, votre poids et votre sexe, en pourcentage de la valeur prédite. La distance est l’estimation de l’appareil — jamais recalculée ici. Sans votre âge, taille, poids et sexe, le pourcentage est masqué et seules la distance et la tendance sont affichées.",
+          "caveat": "Une estimation reformulée par rapport à une référence publiée — un indicateur de capacité fonctionnelle, ni un test de marche de six minutes clinique ni un diagnostic."
         }
       },
       "scores": {

messages/it.json

@@ -2621,6 +2621,22 @@
           "method": "Un indicatore notturno di sforzo da 0 a 100 dal tuo carico di attività pesato sulla frequenza cardiaca (un modello di impulso d’allenamento tipo TRIMP). Più alto significa una giornata più impegnativa.",
           "caveat": "Un indicatore descrittivo di carico di attività, non una misura di carico clinica o da allenamento.",
           "description": "Un indicatore notturno di carico di attività dal tuo sforzo pesato sulla frequenza cardiaca."
+        },
+        "WRIST_TEMPERATURE_BASELINE": {
+          "method": "La tua tipica temperatura notturna al polso è la mediana delle tue letture notturne nel periodo, ± una dispersione robusta (deviazione assoluta mediana, scalata). Segue le TUE letture — la notte scorsa è mostrata come scostamento dalla tua baseline, non da una norma di popolazione.",
+          "caveat": "Solo una banda di scostamento personale — descrittiva, non un segnale di malattia, febbre o fase del ciclo. Sei tu a interpretarla."
+        },
+        "STAIR_ASCENT_SPEED_BASELINE": {
+          "method": "Il tuo passo tipico in salita sulle scale è la mediana dei tuoi valori giornalieri nel periodo, ± una dispersione robusta (deviazione assoluta mediana, scalata). La banda è costruita sui tuoi dati — non esiste una soglia di popolazione per la velocità sulle scale, perché il passo dipende dalla geometria dei gradini e dalla lunghezza delle gambe.",
+          "caveat": "Una banda personale di tendenza della mobilità — descrittiva, non una valutazione di fragilità o di rischio di caduta."
+        },
+        "STAIR_DESCENT_SPEED_BASELINE": {
+          "method": "Il tuo passo tipico in discesa sulle scale è la mediana dei tuoi valori giornalieri nel periodo, ± una dispersione robusta (deviazione assoluta mediana, scalata). La banda è costruita sui tuoi dati — non esiste una soglia di popolazione per la velocità sulle scale, perché il passo dipende dalla geometria dei gradini e dalla lunghezza delle gambe.",
+          "caveat": "Una banda personale di tendenza della mobilità — descrittiva, non una valutazione di fragilità o di rischio di caduta."
+        },
+        "SIX_MINUTE_WALK_BAND": {
+          "method": "La distanza di cammino di sei minuti STIMATA dal tuo dispositivo, collocata rispetto al riferimento di Enright e Sherrill per la tua età, altezza, peso e sesso, come percentuale del previsto. La distanza è la stima del dispositivo — mai ricalcolata qui. Senza età, altezza, peso e sesso la percentuale è nascosta e vengono mostrate solo distanza e tendenza.",
+          "caveat": "Una stima riformulata rispetto a un riferimento pubblicato — un segnale di capacità funzionale, non un test del cammino di sei minuti clinico né una diagnosi."
         }
       },
       "scores": {

messages/pl.json

@@ -2621,6 +2621,22 @@
           "method": "Nocny wskaźnik obciążenia 0–100 na podstawie Twojego obciążenia aktywnością ważonego tętnem (model impulsu treningowego typu TRIMP). Wyższy oznacza cięższy dzień.",
           "caveat": "Opisowy wskaźnik obciążenia aktywnością, nie kliniczna ani treningowa miara obciążenia.",
           "description": "Nocny wskaźnik obciążenia aktywnością z Twojego wysiłku ważonego tętnem."
+        },
+        "WRIST_TEMPERATURE_BASELINE": {
+          "method": "Twoja typowa nocna temperatura nadgarstka to mediana Twoich nocnych odczytów w danym okresie, ± solidny rozrzut (przeskalowane medianowe odchylenie bezwzględne). Śledzi TWOJE odczyty — ostatnia noc jest pokazana jako odchylenie od Twojej własnej bazy, a nie od normy populacyjnej.",
+          "caveat": "Tylko osobiste pasmo odchylenia — opisowe, nie sygnał choroby, gorączki ani fazy cyklu. Interpretujesz je samodzielnie."
+        },
+        "STAIR_ASCENT_SPEED_BASELINE": {
+          "method": "Twoje typowe tempo wchodzenia po schodach to mediana Twoich dziennych wartości w danym okresie, ± solidny rozrzut (przeskalowane medianowe odchylenie bezwzględne). Pasmo jest budowane z Twoich danych — nie ma populacyjnego progu prędkości na schodach, bo tempo zależy od geometrii schodów i długości nóg.",
+          "caveat": "Osobiste pasmo trendu mobilności — opisowe, nie ocena kruchości ani ryzyka upadku."
+        },
+        "STAIR_DESCENT_SPEED_BASELINE": {
+          "method": "Twoje typowe tempo schodzenia po schodach to mediana Twoich dziennych wartości w danym okresie, ± solidny rozrzut (przeskalowane medianowe odchylenie bezwzględne). Pasmo jest budowane z Twoich danych — nie ma populacyjnego progu prędkości na schodach, bo tempo zależy od geometrii schodów i długości nóg.",
+          "caveat": "Osobiste pasmo trendu mobilności — opisowe, nie ocena kruchości ani ryzyka upadku."
+        },
+        "SIX_MINUTE_WALK_BAND": {
+          "method": "SZACOWANY przez Twoje urządzenie dystans sześciominutowego marszu odniesiony do wzorca Enrighta i Sherrilla dla Twojego wieku, wzrostu, wagi i płci, jako procent wartości przewidywanej. Dystans to szacunek urządzenia — nigdy nie jest tu przeliczany. Bez Twojego wieku, wzrostu, wagi i płci procent jest ukryty i pokazywane są tylko dystans i trend.",
+          "caveat": "Szacunek odniesiony do opublikowanego wzorca — sygnał wydolności funkcjonalnej, nie kliniczny test sześciominutowego marszu ani diagnoza."
         }
       },
       "scores": {

src/components/insights/derived/standards.ts

@@ -128,4 +128,40 @@ export const METRIC_PROVENANCE: Record<DerivedMetricId, MetricProvenanceMeta> =
     },
     caveatKey: "insights.derived.composite.STRAIN_SCORE.caveat",
   },
+  WRIST_TEMPERATURE_BASELINE: {
+    methodKey: "insights.derived.composite.WRIST_TEMPERATURE_BASELINE.method",
+    standard: {
+      // Robust personal-deviation band via the median ± k·MAD.
+      name: "Leys et al. 2013, J. Exp. Soc. Psychol.",
+      url: "https://doi.org/10.1016/j.jesp.2013.03.013",
+    },
+    caveatKey: "insights.derived.composite.WRIST_TEMPERATURE_BASELINE.caveat",
+  },
+  STAIR_ASCENT_SPEED_BASELINE: {
+    methodKey: "insights.derived.composite.STAIR_ASCENT_SPEED_BASELINE.method",
+    standard: {
+      // Robust personal-trend band via the median ± k·MAD.
+      name: "Leys et al. 2013, J. Exp. Soc. Psychol.",
+      url: "https://doi.org/10.1016/j.jesp.2013.03.013",
+    },
+    caveatKey: "insights.derived.composite.STAIR_ASCENT_SPEED_BASELINE.caveat",
+  },
+  STAIR_DESCENT_SPEED_BASELINE: {
+    methodKey: "insights.derived.composite.STAIR_DESCENT_SPEED_BASELINE.method",
+    standard: {
+      // Robust personal-trend band via the median ± k·MAD.
+      name: "Leys et al. 2013, J. Exp. Soc. Psychol.",
+      url: "https://doi.org/10.1016/j.jesp.2013.03.013",
+    },
+    caveatKey: "insights.derived.composite.STAIR_DESCENT_SPEED_BASELINE.caveat",
+  },
+  SIX_MINUTE_WALK_BAND: {
+    methodKey: "insights.derived.composite.SIX_MINUTE_WALK_BAND.method",
+    standard: {
+      // Enright & Sherrill 1998 reference equations (ATS 2002 test standard).
+      name: "Enright & Sherrill 1998, Am. J. Respir. Crit. Care Med.",
+      url: "https://doi.org/10.1164/ajrccm.158.5.9710086",
+    },
+    caveatKey: "insights.derived.composite.SIX_MINUTE_WALK_BAND.caveat",
+  },
 };

src/lib/insights/correlation-discovery.ts

@@ -249,4 +249,12 @@ export const DISCOVERY_OUTCOMES = [
   "HEART_RATE_VARIABILITY",
   "RESTING_HEART_RATE",
   "WEIGHT",
+  // Wrist temperature is a credible future OUTCOME channel (near-daily, so
+  // n ≥ 20 is reachable; "did a hard workout / late alcohol raise next-night
+  // temperature?"), but it is deliberately NOT a channel yet: it is
+  // privacy-sensitive and deviation-framed, and folding it into the FDR
+  // matrix risks surfacing a cycle-phase correlation that strays into
+  // reproductive inference. Held pending a deliberate privacy review —
+  // documented here so the omission is intentional, not a gap (same posture
+  // as the medication-compliance omission above).
 ] as const;

src/lib/insights/derived/__tests__/dispatch.test.ts

@@ -39,6 +39,16 @@ describe("registry", () => {
     expect(getDerivedMetricMeta("RECOVERY_SCORE")?.implemented).toBe(true);
     expect(getDerivedMetricMeta("STRESS_SCORE")?.implemented).toBe(true);
     expect(getDerivedMetricMeta("STRAIN_SCORE")?.implemented).toBe(true);
+    expect(
+      getDerivedMetricMeta("WRIST_TEMPERATURE_BASELINE")?.implemented,
+    ).toBe(true);
+    expect(
+      getDerivedMetricMeta("STAIR_ASCENT_SPEED_BASELINE")?.implemented,
+    ).toBe(true);
+    expect(
+      getDerivedMetricMeta("STAIR_DESCENT_SPEED_BASELINE")?.implemented,
+    ).toBe(true);
+    expect(getDerivedMetricMeta("SIX_MINUTE_WALK_BAND")?.implemented).toBe(true);
   });
 
   it("isDerivedMetricId rejects unknown ids", () => {
@@ -59,7 +69,11 @@ describe("registry", () => {
     expect(DERIVED_METRIC_IDS).toContain("RECOVERY_SCORE");
     expect(DERIVED_METRIC_IDS).toContain("STRESS_SCORE");
     expect(DERIVED_METRIC_IDS).toContain("STRAIN_SCORE");
-    expect(DERIVED_METRIC_IDS.length).toBe(11);
+    expect(DERIVED_METRIC_IDS).toContain("WRIST_TEMPERATURE_BASELINE");
+    expect(DERIVED_METRIC_IDS).toContain("STAIR_ASCENT_SPEED_BASELINE");
+    expect(DERIVED_METRIC_IDS).toContain("STAIR_DESCENT_SPEED_BASELINE");
+    expect(DERIVED_METRIC_IDS).toContain("SIX_MINUTE_WALK_BAND");
+    expect(DERIVED_METRIC_IDS.length).toBe(15);
   });
 });
 
@@ -127,6 +141,43 @@ describe("computeDerivedMetric dispatch", () => {
     }
   });
 
+  it.each([
+    "WRIST_TEMPERATURE_BASELINE",
+    "STAIR_ASCENT_SPEED_BASELINE",
+    "STAIR_DESCENT_SPEED_BASELINE",
+  ] as const)(
+    "routes %s through the baseline engine (no data → insufficient, not not_implemented)",
+    async (metric) => {
+      const result = await computeDerivedMetric({
+        metric,
+        userId: "u1",
+        profile: PROFILE,
+        now: NOW,
+      });
+      expect(result.status).toBe("insufficient");
+      if (result.status === "insufficient") {
+        expect(result.reason).not.toBe("not_implemented");
+        // The baseline engine names its fixed type as the missing input.
+        expect(result.provenance.inputs).toContain(
+          metric.replace("_BASELINE", ""),
+        );
+      }
+    },
+  );
+
+  it("routes SIX_MINUTE_WALK_BAND to its engine (no data → insufficient, not not_implemented)", async () => {
+    const result = await computeDerivedMetric({
+      metric: "SIX_MINUTE_WALK_BAND",
+      userId: "u1",
+      profile: PROFILE,
+      now: NOW,
+    });
+    expect(result.status).toBe("insufficient");
+    if (result.status === "insufficient") {
+      expect(result.reason).toBe("no_readings_in_window");
+    }
+  });
+
   it("returns unsupported_baseline_type for a bad VITALS_BASELINE type", async () => {
     const result = await computeDerivedMetric({
       metric: "VITALS_BASELINE",

src/lib/insights/derived/__tests__/norms.test.ts

@@ -1,5 +1,9 @@
 import { describe, it, expect } from "vitest";
-import { lookupNormalRange, hasSharpenedNorm } from "../norms";
+import {
+  lookupNormalRange,
+  hasSharpenedNorm,
+  predictSixMinuteWalkDistance,
+} from "../norms";
 
 describe("lookupNormalRange — the age/sex reference-range enabler", () => {
   it("returns a sex-specific VO2max band for a registered metric", () => {
@@ -59,3 +63,39 @@ describe("hasSharpenedNorm", () => {
     expect(hasSharpenedNorm("STEPS", 35, "MALE")).toBe(false);
   });
 });
+
+describe("predictSixMinuteWalkDistance — Enright & Sherrill 1998", () => {
+  it("matches the published male equation", () => {
+    // 7.57·180 − 5.02·40 − 1.76·80 − 309 = 712 m
+    expect(predictSixMinuteWalkDistance(40, 180, 80, "MALE")).toBeCloseTo(
+      712,
+      6,
+    );
+  });
+
+  it("matches the published female equation", () => {
+    // 2.11·165 − 2.29·65 − 5.78·40 + 667 = 635.1 m
+    expect(predictSixMinuteWalkDistance(40, 165, 65, "FEMALE")).toBeCloseTo(
+      635.1,
+      6,
+    );
+  });
+
+  it("returns null without a usable sex (the equations differ by sex)", () => {
+    expect(predictSixMinuteWalkDistance(40, 180, 80, null)).toBeNull();
+  });
+
+  it("returns null when weight is absent (no silently-dropped term)", () => {
+    expect(predictSixMinuteWalkDistance(40, 180, null, "MALE")).toBeNull();
+  });
+
+  it("returns null without height", () => {
+    expect(predictSixMinuteWalkDistance(40, null, 80, "MALE")).toBeNull();
+  });
+
+  it("returns null for non-adult / non-finite ages", () => {
+    expect(predictSixMinuteWalkDistance(12, 150, 45, "MALE")).toBeNull();
+    expect(predictSixMinuteWalkDistance(Number.NaN, 180, 80, "MALE")).toBeNull();
+    expect(predictSixMinuteWalkDistance(null, 180, 80, "MALE")).toBeNull();
+  });
+});

src/lib/insights/derived/__tests__/six-minute-walk.test.ts

@@ -0,0 +1,117 @@
+import { describe, it, expect, vi, beforeEach } from "vitest";
+
+const findMany = vi.fn();
+const findFirst = vi.fn();
+vi.mock("@/lib/db", () => ({
+  prisma: {
+    measurement: {
+      findMany: (...a: unknown[]) => findMany(...a),
+      findFirst: (...a: unknown[]) => findFirst(...a),
+    },
+  },
+}));
+
+import {
+  computeSixMinuteWalkBand,
+  placeSixMinuteWalkBand,
+} from "../six-minute-walk";
+
+const NOW = new Date("2026-06-02T07:00:00Z");
+// Enright male, 40 yr, 180 cm, 80 kg →
+//   7.57·180 − 5.02·40 − 1.76·80 − 309 = 712 m predicted.
+const MALE_40 = { ageYears: 40, sex: "MALE" as const, heightCm: 180 };
+const NO_DEMO = { ageYears: null, sex: null, heightCm: null };
+const NO_WEIGHT_PROFILE = MALE_40;
+
+beforeEach(() => vi.clearAllMocks());
+
+describe("placeSixMinuteWalkBand", () => {
+  it("green at/above 80% of predicted", () => {
+    expect(placeSixMinuteWalkBand(80)).toBe("green");
+    expect(placeSixMinuteWalkBand(100)).toBe("green");
+  });
+  it("yellow between 60 and 80%", () => {
+    expect(placeSixMinuteWalkBand(60)).toBe("yellow");
+    expect(placeSixMinuteWalkBand(79)).toBe("yellow");
+  });
+  it("red below 60%", () => {
+    expect(placeSixMinuteWalkBand(59)).toBe("red");
+  });
+  it("null without a percent", () => {
+    expect(placeSixMinuteWalkBand(null)).toBeNull();
+  });
+});
+
+describe("computeSixMinuteWalkBand", () => {
+  it("insufficient when no 6MWT reading exists", async () => {
+    findMany.mockResolvedValueOnce([]);
+    const r = await computeSixMinuteWalkBand("u1", MALE_40, { now: NOW });
+    expect(r.status).toBe("insufficient");
+    if (r.status === "insufficient") {
+      expect(r.reason).toBe("no_readings_in_window");
+    }
+    // No reading → never reach the weight read.
+    expect(findFirst).not.toHaveBeenCalled();
+  });
+
+  it("ok with a band + percent-of-predicted when full demographics + weight exist", async () => {
+    // 3 readings → trend = 712 - 700 = 12; distance 712 vs predicted 712 → 100%.
+    findMany.mockResolvedValueOnce([
+      { value: 712 },
+      { value: 700 },
+      { value: 690 },
+    ]);
+    findFirst.mockResolvedValueOnce({ value: 80 });
+    const r = await computeSixMinuteWalkBand("u1", MALE_40, { now: NOW });
+    expect(r.status).toBe("ok");
+    if (r.status === "ok") {
+      expect(r.value.distanceM).toBe(712);
+      expect(r.value.predictedM).toBe(712);
+      expect(r.value.percentOfPredicted).toBe(100);
+      expect(r.value.band).toBe("green");
+      expect(r.value.trendDelta).toBe(12);
+    }
+  });
+
+  it("bands red on a low percent of predicted", async () => {
+    // 400 / 712 = 56% → red.
+    findMany.mockResolvedValueOnce([{ value: 400 }]);
+    findFirst.mockResolvedValueOnce({ value: 80 });
+    const r = await computeSixMinuteWalkBand("u1", MALE_40, { now: NOW });
+    expect(r.status).toBe("ok");
+    if (r.status === "ok") {
+      expect(r.value.percentOfPredicted).toBe(56);
+      expect(r.value.band).toBe("red");
+    }
+  });
+
+  it("ok but band/percent null without demographics", async () => {
+    findMany.mockResolvedValueOnce([{ value: 500 }]);
+    findFirst.mockResolvedValueOnce({ value: 80 });
+    const r = await computeSixMinuteWalkBand("u1", NO_DEMO, { now: NOW });
+    expect(r.status).toBe("ok");
+    if (r.status === "ok") {
+      expect(r.value.distanceM).toBe(500);
+      expect(r.value.predictedM).toBeNull();
+      expect(r.value.percentOfPredicted).toBeNull();
+      expect(r.value.band).toBeNull();
+      // Single reading → trend suppressed.
+      expect(r.value.trendDelta).toBeNull();
+    }
+  });
+
+  it("ok but band null when weight is absent (no fabricated placement)", async () => {
+    findMany.mockResolvedValueOnce([{ value: 600 }]);
+    findFirst.mockResolvedValueOnce(null); // no recent weight
+    const r = await computeSixMinuteWalkBand("u1", NO_WEIGHT_PROFILE, {
+      now: NOW,
+    });
+    expect(r.status).toBe("ok");
+    if (r.status === "ok") {
+      expect(r.value.distanceM).toBe(600);
+      expect(r.value.predictedM).toBeNull();
+      expect(r.value.percentOfPredicted).toBeNull();
+      expect(r.value.band).toBeNull();
+    }
+  });
+});

src/lib/insights/derived/dispatch.ts

@@ -23,6 +23,7 @@ import {
   type BaselineProfile,
 } from "./baseline";
 import { computeFitnessAge } from "./fitness-age";
+import { computeSixMinuteWalkBand } from "./six-minute-walk";
 import { computeVascularAgeDelta } from "./vascular-age";
 import { computeHrvBalance } from "./hrv-balance";
 import { computeBmi } from "./bmi";
@@ -146,6 +147,36 @@ export async function computeDerivedMetric(
         windowDays: args.windowDays,
         now,
       }) as Promise<Derived<unknown>>;
+    case "WRIST_TEMPERATURE_BASELINE":
+    case "STAIR_ASCENT_SPEED_BASELINE":
+    case "STAIR_DESCENT_SPEED_BASELINE": {
+      // v1.10.3 additive HealthKit baselines — each pins ONE fixed type and
+      // reuses the type-generic baseline engine unchanged (median ± k·MAD).
+      // Wrist temperature is a personal-DEVIATION band (no illness/cycle
+      // inference); stair ascent/descent are personal trend bands (no
+      // population cutoff — stair pace is geometry-confounded). The fixed
+      // type is the metric's single registered input.
+      const baselineType: Record<
+        | "WRIST_TEMPERATURE_BASELINE"
+        | "STAIR_ASCENT_SPEED_BASELINE"
+        | "STAIR_DESCENT_SPEED_BASELINE",
+        MeasurementType
+      > = {
+        WRIST_TEMPERATURE_BASELINE: "WRIST_TEMPERATURE",
+        STAIR_ASCENT_SPEED_BASELINE: "STAIR_ASCENT_SPEED",
+        STAIR_DESCENT_SPEED_BASELINE: "STAIR_DESCENT_SPEED",
+      };
+      return computeVitalsBaseline(args.userId, args.profile, {
+        type: baselineType[args.metric],
+        windowDays: args.windowDays,
+        now,
+      }) as Promise<Derived<unknown>>;
+    }
+    case "SIX_MINUTE_WALK_BAND":
+      return computeSixMinuteWalkBand(args.userId, args.profile, {
+        windowDays: args.windowDays,
+        now,
+      }) as Promise<Derived<unknown>>;
     case "RECOVERY_SCORE":
     case "STRESS_SCORE":
     case "STRAIN_SCORE":

src/lib/insights/derived/index.ts

@@ -39,9 +39,11 @@ export type { DeriveCoverageArgs } from "./coverage";
 export {
   DERIVED_METRIC_IDS,
   VITALS_BASELINE_TYPES,
+  BASELINE_CAPABLE_TYPES,
   isDerivedMetricId,
   getDerivedMetricMeta,
   isVitalsBaselineType,
+  isBaselineCapableType,
 } from "./registry";
 export type {
   DerivedMetricId,
@@ -49,7 +51,11 @@ export type {
   DerivedArchetype,
 } from "./registry";
 
-export { lookupNormalRange, hasSharpenedNorm } from "./norms";
+export {
+  lookupNormalRange,
+  hasSharpenedNorm,
+  predictSixMinuteWalkDistance,
+} from "./norms";
 export type { NormRange, NormSex } from "./norms";
 
 // ── server-only compute engines (do NOT value-import from a client component) ──
@@ -77,6 +83,15 @@ export {
 } from "./fitness-age";
 export type { FitnessAgeValue, FitnessBand } from "./fitness-age";
 
+export {
+  computeSixMinuteWalkBand,
+  placeSixMinuteWalkBand,
+} from "./six-minute-walk";
+export type {
+  SixMinuteWalkValue,
+  SixMinuteWalkBand,
+} from "./six-minute-walk";
+
 export { computeVascularAgeDelta, placeVascularBand } from "./vascular-age";
 export type { VascularAgeDeltaValue, VascularBand } from "./vascular-age";
 

src/lib/insights/derived/norms.ts

@@ -24,6 +24,13 @@
  *     377(9770):1011–1018, normal-range HR centiles by age).
  *   - Respiratory rate by age — clinical reference (WHO/PALS adult vs
  *     paediatric ranges).
+ *   - Six-minute-walk distance — a published REGRESSION (not a bracket
+ *     table): Enright & Sherrill 1998, "Reference Equations for the
+ *     Six-Minute Walk in Healthy Adults", Am J Respir Crit Care Med
+ *     158(5):1384–1387; the test itself standardised by ATS 2002,
+ *     "ATS Statement: Guidelines for the Six-Minute Walk Test",
+ *     Am J Respir Crit Care Med 166(1):111–117. Surfaced as a
+ *     percent-of-predicted re-frame, never a HealthLog-derived equation.
  *
  * Client-safe — pure data + a pure lookup, no server imports.
  */
@@ -145,6 +152,53 @@ export function lookupNormalRange(
   return null;
 }
 
+/**
+ * Enright & Sherrill 1998 predicted six-minute-walk distance (metres) for a
+ * healthy adult. A published linear regression on age, height, weight, sex —
+ * NOT a HealthLog-derived model:
+ *   - Men:   6MWD = 7.57·height_cm − 5.02·age − 1.76·weight_kg − 309
+ *   - Women: 6MWD = 2.11·height_cm − 2.29·weight_kg − 5.78·age + 667
+ *
+ * Returns `null` when the inputs the equation needs are absent, so the caller
+ * surfaces the raw distance + trend without a fabricated placement (the
+ * `fitness-age.ts` `band: null` discipline). Sex is required (the two
+ * coefficient sets differ); height is required (the dominant term). Weight is
+ * required for the published full equation — when it is missing we return
+ * `null` rather than silently dropping the weight term, since the omission
+ * would inflate the predicted distance.
+ *
+ * Pure. The equation is for adults; for ages below 18 the reference does not
+ * apply and we return `null`.
+ */
+export function predictSixMinuteWalkDistance(
+  ageYears: number | null | undefined,
+  heightCm: number | null | undefined,
+  weightKg: number | null | undefined,
+  sex: NormSex,
+): number | null {
+  if (sex !== "MALE" && sex !== "FEMALE") return null;
+  if (
+    ageYears == null ||
+    !Number.isFinite(ageYears) ||
+    ageYears < 18 ||
+    ageYears > 120
+  ) {
+    return null;
+  }
+  if (heightCm == null || !Number.isFinite(heightCm) || heightCm <= 0) {
+    return null;
+  }
+  if (weightKg == null || !Number.isFinite(weightKg) || weightKg <= 0) {
+    return null;
+  }
+  const predicted =
+    sex === "MALE"
+      ? 7.57 * heightCm - 5.02 * ageYears - 1.76 * weightKg - 309
+      : 2.11 * heightCm - 2.29 * weightKg - 5.78 * ageYears + 667;
+  // A non-positive prediction is physically meaningless — treat as no band.
+  return predicted > 0 ? predicted : null;
+}
+
 /** `true` when an age/sex-sharpened band exists for the metric+profile. */
 export function hasSharpenedNorm(
   metricId: MetricStatusMetricId,

src/lib/insights/derived/registry.ts

@@ -46,7 +46,27 @@ export type DerivedMetricId =
   /** Persisted nightly stress composite (passthrough read of COMPUTED rows). */
   | "STRESS_SCORE"
   /** Persisted nightly strain composite (passthrough read of COMPUTED rows). */
-  | "STRAIN_SCORE";
+  | "STRAIN_SCORE"
+  /** v1.10.3: overnight wrist-temperature personal-deviation band (baseline engine). */
+  | "WRIST_TEMPERATURE_BASELINE"
+  /** v1.10.3: stair-ascent-speed personal trend band (baseline engine). */
+  | "STAIR_ASCENT_SPEED_BASELINE"
+  /** v1.10.3: stair-descent-speed personal trend band (baseline engine). */
+  | "STAIR_DESCENT_SPEED_BASELINE"
+  /** v1.10.3: estimated 6-minute-walk distance vs Enright-predicted (passthrough re-frame). */
+  | "SIX_MINUTE_WALK_BAND";
+
+// Documented-as-omitted (v1.10.3): two additive HealthKit signals stay
+// trend-only with NO derived band, on purpose —
+//   - FALL_COUNT is a zero-inflated discrete safety EVENT (target = zero); a
+//     median ± k·MAD band on a near-constant-zero series is meaningless and a
+//     band would imply a smooth metric where there is none.
+//   - BREATHING_DISTURBANCES is a regulated sleep-apnea SCREENING signal (Apple
+//     publishes only NotElevated/Elevated, no numeric cutoff); a self-derived
+//     band would read as a HealthLog verdict on a screening signal and imply a
+//     diagnosis. The fired BREATHING_DISTURBANCE_EVENT carries the device's own
+//     classification in the awareness card; the continuous index stays a plain
+//     trend with the generic assessment.
 
 /** Archetype of a derived metric — drives shaping + the QA inventory. */
 export type DerivedArchetype =
@@ -104,6 +124,25 @@ export const VITALS_BASELINE_TYPES: MeasurementType[] = [
   "WEIGHT",
 ];
 
+/**
+ * The full set of measurement types the type-generic baseline engine
+ * (`computeVitalsBaseline`, median ± k·MAD) can produce a personal band
+ * for. A superset of `VITALS_BASELINE_TYPES`: it adds the v1.10.3
+ * additive HealthKit signals that get an `any-user-baseline` derived
+ * metric of their own (wrist temperature as a personal-deviation band;
+ * stair ascent/descent speed as a personal trend band — NO population
+ * cutoff, since stair pace is geometry-confounded). The engine is
+ * type-generic; this allowlist is the gate, kept distinct from
+ * `VITALS_BASELINE_TYPES` so a stair-speed baseline is never mislabelled a
+ * "vital".
+ */
+export const BASELINE_CAPABLE_TYPES: MeasurementType[] = [
+  ...VITALS_BASELINE_TYPES,
+  "WRIST_TEMPERATURE",
+  "STAIR_ASCENT_SPEED",
+  "STAIR_DESCENT_SPEED",
+];
+
 const REGISTRY: Record<DerivedMetricId, DerivedMetricMeta> = {
   VITALS_BASELINE: {
     id: "VITALS_BASELINE",
@@ -210,6 +249,42 @@ const REGISTRY: Record<DerivedMetricId, DerivedMetricMeta> = {
     minInputs: 1,
     implemented: true,
   },
+  WRIST_TEMPERATURE_BASELINE: {
+    id: "WRIST_TEMPERATURE_BASELINE",
+    displayName: "Wrist-temperature baseline",
+    archetype: "any-user-baseline",
+    inputs: ["WRIST_TEMPERATURE"],
+    minHistoryDays: 7,
+    minInputs: 1,
+    implemented: true,
+  },
+  STAIR_ASCENT_SPEED_BASELINE: {
+    id: "STAIR_ASCENT_SPEED_BASELINE",
+    displayName: "Stair-ascent-speed baseline",
+    archetype: "any-user-baseline",
+    inputs: ["STAIR_ASCENT_SPEED"],
+    minHistoryDays: 7,
+    minInputs: 1,
+    implemented: true,
+  },
+  STAIR_DESCENT_SPEED_BASELINE: {
+    id: "STAIR_DESCENT_SPEED_BASELINE",
+    displayName: "Stair-descent-speed baseline",
+    archetype: "any-user-baseline",
+    inputs: ["STAIR_DESCENT_SPEED"],
+    minHistoryDays: 7,
+    minInputs: 1,
+    implemented: true,
+  },
+  SIX_MINUTE_WALK_BAND: {
+    id: "SIX_MINUTE_WALK_BAND",
+    displayName: "Estimated 6-minute-walk band",
+    archetype: "passthrough-reframe",
+    inputs: ["SIX_MINUTE_WALK_DISTANCE"],
+    minHistoryDays: 1,
+    minInputs: 1,
+    implemented: true,
+  },
 };
 
 /** Closed set of ids the generic route accepts (Zod enum source). */
@@ -231,3 +306,8 @@ export function getDerivedMetricMeta(
 export function isVitalsBaselineType(type: string): boolean {
   return (VITALS_BASELINE_TYPES as string[]).includes(type);
 }
+
+/** `true` when the type-generic baseline engine can band this type. */
+export function isBaselineCapableType(type: string): boolean {
+  return (BASELINE_CAPABLE_TYPES as string[]).includes(type);
+}

src/lib/insights/derived/six-minute-walk.ts

@@ -0,0 +1,199 @@
+/**
+ * v1.10.3 — additive HealthKit signal: estimated six-minute-walk distance,
+ * re-framed against a published reference equation.
+ *
+ * `computeSixMinuteWalkBand(userId, profile, opts)` takes the device's
+ * ESTIMATED 6-minute-walk distance (HealthKit `sixMinuteWalkTestDistance` —
+ * an estimate, NOT a supervised in-clinic 6MWT) and re-frames it as a
+ * percent-of-predicted against the Enright & Sherrill 1998 reference
+ * equation for healthy adults. It NEVER recomputes the distance and NEVER
+ * derives its own equation — this is the `passthrough-reframe` archetype,
+ * the same posture `fitness-age.ts` takes against VO₂max.
+ *
+ *   - **percentOfPredicted** — distance ÷ Enright-predicted × 100, placed in
+ *     a green/yellow/red band (≥ 80% green; 60–80% yellow; < 60% red),
+ *     `null` when the demographics the equation needs are absent (sex,
+ *     adult age, height, AND weight — the published full equation). With no
+ *     band the metric still surfaces the raw distance + trend, never a
+ *     fabricated placement.
+ *   - **trend** — signed latest-vs-prior delta, surfaced only once ≥ 3
+ *     readings exist (the catalogue's trend gate).
+ *
+ * Standard: Enright & Sherrill 1998 (reference equations) + ATS 2002 (the
+ * test standard) — cited in `norms.ts`. Apple's value is framed as
+ * "estimated", surfaced + trended, never re-derived. No diagnosis: a low
+ * percent is a functional-capacity awareness signal, not a verdict.
+ *
+ * Server-only — reads the latest `SIX_MINUTE_WALK_DISTANCE` + `WEIGHT` rows
+ * via Prisma; age/height/sex come from the caller's profile. The placement
+ * helper is exported pure for the unit tests.
+ */
+import type { MeasurementType } from "@/generated/prisma/client";
+import { prisma } from "@/lib/db";
+import {
+  buildInsufficient,
+  buildOk,
+  deriveCoverage,
+  nowProvenanceTimestamp,
+} from "./coverage";
+import { predictSixMinuteWalkDistance } from "./norms";
+import type { BaselineProfile } from "./baseline";
+import type { Derived, DerivedProvenanceSource } from "./types";
+
+/** Band placement, same green/yellow/red vocabulary the tokens speak. */
+export type SixMinuteWalkBand = "green" | "yellow" | "red";
+
+const SIX_MINUTE_WALK_TYPE: MeasurementType = "SIX_MINUTE_WALK_DISTANCE";
+const WEIGHT_TYPE: MeasurementType = "WEIGHT";
+/** Readings needed before the latest-vs-prior trend delta is surfaced. */
+const MIN_TREND_READINGS = 3;
+/**
+ * The estimate refreshes at most every few days; widen the read window so the
+ * latest value + trend survive sparse cadence (matches `fitness-age.ts`).
+ */
+const DEFAULT_WINDOW_DAYS = 180;
+/** A weight reading older than this no longer reflects current capacity. */
+const WEIGHT_WINDOW_DAYS = 90;
+
+/** Percent-of-predicted band thresholds (% of Enright-predicted). */
+const GREEN_PCT = 80;
+const YELLOW_PCT = 60;
+
+/** The successful `value` payload for the 6-minute-walk band. */
+export interface SixMinuteWalkValue {
+  /** The latest device-estimated 6-minute-walk distance (m). */
+  distanceM: number;
+  /** Enright-predicted distance for the profile (m), or `null` without demographics. */
+  predictedM: number | null;
+  /** Distance ÷ predicted × 100, rounded; `null` without a prediction. */
+  percentOfPredicted: number | null;
+  /** Green/yellow/red placement, or `null` without a prediction. */
+  band: SixMinuteWalkBand | null;
+  /** Signed latest-vs-prior delta (m); `null` until ≥ 3 readings. */
+  trendDelta: number | null;
+  /** Distinct readings in the window. */
+  readingCount: number;
+}
+
+/**
+ * Place a percent-of-predicted in a band. Pure. ≥ 80% green; 60–80% yellow;
+ * < 60% red; `null` when the percent is absent.
+ */
+export function placeSixMinuteWalkBand(
+  percentOfPredicted: number | null,
+): SixMinuteWalkBand | null {
+  if (percentOfPredicted == null) return null;
+  if (percentOfPredicted >= GREEN_PCT) return "green";
+  if (percentOfPredicted >= YELLOW_PCT) return "yellow";
+  return "red";
+}
+
+/**
+ * Estimated six-minute-walk band — passthrough re-frame of
+ * `SIX_MINUTE_WALK_DISTANCE`. Returns `insufficient` when no reading exists;
+ * otherwise an `ok` value carrying the latest distance, its
+ * percent-of-predicted placement (when demographics allow), and a trend once
+ * ≥ 3 readings exist. With incomplete demographics the band is `null` and the
+ * value + trend still surface — never a fabricated placement.
+ */
+export async function computeSixMinuteWalkBand(
+  userId: string,
+  profile: BaselineProfile,
+  opts?: { windowDays?: number; now?: Date },
+): Promise<Derived<SixMinuteWalkValue>> {
+  const now = opts?.now ?? new Date();
+  const windowDays = opts?.windowDays ?? DEFAULT_WINDOW_DAYS;
+  const computedAt = nowProvenanceTimestamp(now);
+  const since = new Date(now.getTime() - windowDays * 24 * 60 * 60 * 1000);
+
+  const rows = await prisma.measurement.findMany({
+    where: {
+      userId,
+      type: SIX_MINUTE_WALK_TYPE,
+      deletedAt: null,
+      measuredAt: { gte: since },
+    },
+    orderBy: { measuredAt: "desc" },
+    select: { value: true },
+  });
+
+  if (rows.length === 0) {
+    const { coverage } = deriveCoverage({
+      requiredInputs: 1,
+      presentInputs: 0,
+      historyDays: 0,
+      missing: [SIX_MINUTE_WALK_TYPE],
+      fullHistoryDays: windowDays,
+    });
+    return buildInsufficient<SixMinuteWalkValue>({
+      coverage,
+      provenance: {
+        inputs: [SIX_MINUTE_WALK_TYPE],
+        source: "none",
+        windowDays,
+        computedAt,
+      },
+      reason: "no_readings_in_window",
+    });
+  }
+
+  const distanceM = rows[0].value;
+
+  // The Enright equation needs a recent weight; read the latest in a tighter
+  // window. Absent → predicted is null and the band is suppressed.
+  const weightSince = new Date(
+    now.getTime() - WEIGHT_WINDOW_DAYS * 24 * 60 * 60 * 1000,
+  );
+  const weightRow = await prisma.measurement.findFirst({
+    where: {
+      userId,
+      type: WEIGHT_TYPE,
+      deletedAt: null,
+      measuredAt: { gte: weightSince },
+    },
+    orderBy: { measuredAt: "desc" },
+    select: { value: true },
+  });
+
+  const predictedM = predictSixMinuteWalkDistance(
+    profile.ageYears,
+    profile.heightCm ?? null,
+    weightRow?.value ?? null,
+    profile.sex,
+  );
+  const percentOfPredicted =
+    predictedM != null && predictedM > 0
+      ? Math.round((distanceM / predictedM) * 100)
+      : null;
+  const band = placeSixMinuteWalkBand(percentOfPredicted);
+  const trendDelta =
+    rows.length >= MIN_TREND_READINGS ? rows[0].value - rows[1].value : null;
+
+  const source: DerivedProvenanceSource = "live";
+  const { coverage, confidence } = deriveCoverage({
+    requiredInputs: 1,
+    presentInputs: 1,
+    historyDays: rows.length,
+    missing: [],
+    fullHistoryDays: MIN_TREND_READINGS,
+  });
+
+  return buildOk<SixMinuteWalkValue>({
+    value: {
+      distanceM,
+      predictedM: predictedM != null ? Math.round(predictedM) : null,
+      percentOfPredicted,
+      band,
+      trendDelta,
+      readingCount: rows.length,
+    },
+    coverage,
+    confidence,
+    provenance: {
+      inputs: [SIX_MINUTE_WALK_TYPE],
+      source,
+      windowDays,
+      computedAt,
+    },
+  });
+}