fix(labs): stop projecting lab trends from stale or short series

A marker whose newest reading is more than a year old is now reported
as of that reading (projection "stale"), with no exit date and no
already-outside verdict. The projection horizon is capped at the span
the readings cover, so a line is never carried further ahead than the
data reaches back. The detail read keeps the newest 2000 readings
rather than the oldest.

docs/api/openapi.yaml

@@ -74758,7 +74758,11 @@ components:
               description: The line's value on `asOf`.
             asOf:
               type: string
-              description: YYYY-MM-DD the line was evaluated on.
+              description: "YYYY-MM-DD the line was evaluated on: today, or `lastAt` when `projection` is `stale`."
+            horizonYears:
+              type: number
+              description: "How far ahead a bound may be met and still count as `exits`: three years, or the readings' span when
+                shorter."
             projection:
               type: string
               enum:
@@ -74768,6 +74772,7 @@ components:
                 - already_outside
                 - no_clear_trend
                 - no_band
+                - stale
             exitDate:
               description: "Only for `exits`: the day the straight line meets `exitBound`. A projection, never a forecast."
               type:
@@ -74791,6 +74796,7 @@ components:
             - pValue
             - fittedNow
             - asOf
+            - horizonYears
             - projection
             - exitDate
             - exitBound
@@ -74822,8 +74828,9 @@ components:
       description: "v1.44 — the least-squares line through every numeric reading of the marker (all stored in the marker's
         unit). Needs at least three readings spanning at least 365 days, else `insufficient`. `projection` places the
         line against the marker's band: `exits` (with `exitDate`) only when the slope's 95 % interval excludes zero, the
-        line is inside the band today and reaches a bound within three years. Server-computed; clients render it as
-        given."
+        line is inside the band today and reaches a bound within `horizonYears` (three years, or the readings' span when
+        shorter). `stale` when the newest reading is more than 365 days old: the line is then reported as of `lastAt`,
+        with no projection. Server-computed; clients render it as given."
     UpdateBiomarkerResponse:
       type: object
       properties:

messages/de.json

@@ -10207,10 +10207,11 @@
           "high": "Liefe diese Gerade so weiter, erreichte sie um den {date} das obere Ende deines Referenzbereichs. Das ist eine Fortschreibung, keine Vorhersage.",
           "low": "Liefe diese Gerade so weiter, erreichte sie um den {date} das untere Ende deines Referenzbereichs. Das ist eine Fortschreibung, keine Vorhersage."
         },
-        "beyond_horizon": "In diesem Tempo bleibt die Gerade noch mindestens drei Jahre in deinem Referenzbereich.",
+        "beyond_horizon": "In diesem Tempo bleibt die Gerade länger als {years} Jahre in deinem Referenzbereich, so weit reichen deine Werte zurück.",
         "no_exit": "Die Gerade läuft von den Grenzen deines Referenzbereichs weg.",
         "already_outside": "Die Gerade liegt bereits außerhalb deines Referenzbereichs.",
-        "no_clear_trend": "Über diese Werte ist die Veränderung nicht klar von keiner Veränderung zu unterscheiden, deshalb wird nichts fortgeschrieben."
+        "no_clear_trend": "Über diese Werte ist die Veränderung nicht klar von keiner Veränderung zu unterscheiden, deshalb wird nichts fortgeschrieben.",
+        "stale": "Der neueste Wert ist vom {date}, also älter als ein Jahr. Die Gerade gilt für diesen Stand, ohne Projektion."
       },
       "interval": "95-%-Intervall der jährlichen Veränderung: {lo} bis {hi} {unit}."
     }

messages/en.json

@@ -10207,10 +10207,11 @@
           "high": "If this straight line continued, it would reach the upper end of your reference range around {date}. That is a projection, not a forecast.",
           "low": "If this straight line continued, it would reach the lower end of your reference range around {date}. That is a projection, not a forecast."
         },
-        "beyond_horizon": "At this pace the line stays inside your reference range for at least three more years.",
+        "beyond_horizon": "At this pace the line stays inside your reference range for more than {years} years, the span your readings cover.",
         "no_exit": "The line heads away from the edges of your reference range.",
         "already_outside": "The line already sits outside your reference range.",
-        "no_clear_trend": "Across these readings the change is not clearly different from no change, so no projection is drawn."
+        "no_clear_trend": "Across these readings the change is not clearly different from no change, so no projection is drawn.",
+        "stale": "The newest reading is from {date}, more than a year ago. The line is shown as of then, without a projection."
       },
       "interval": "95 % interval of the yearly change: {lo} to {hi} {unit}."
     }

messages/es.json

@@ -10207,10 +10207,11 @@
           "high": "Si esta línea recta continuara, llegaría al límite superior de tu rango de referencia hacia el {date}. Es una proyección, no un pronóstico.",
           "low": "Si esta línea recta continuara, llegaría al límite inferior de tu rango de referencia hacia el {date}. Es una proyección, no un pronóstico."
         },
-        "beyond_horizon": "A este ritmo, la línea se mantiene dentro de tu rango de referencia al menos tres años más.",
+        "beyond_horizon": "A este ritmo, la línea se mantiene dentro de tu rango de referencia más de {years} años, el periodo que cubren tus valores.",
         "no_exit": "La línea se aleja de los límites de tu rango de referencia.",
         "already_outside": "La línea ya está fuera de tu rango de referencia.",
-        "no_clear_trend": "En estos valores, el cambio no se distingue con claridad de la ausencia de cambio, así que no se proyecta nada."
+        "no_clear_trend": "En estos valores, el cambio no se distingue con claridad de la ausencia de cambio, así que no se proyecta nada.",
+        "stale": "El valor más reciente es del {date}, hace más de un año. La línea se muestra a esa fecha, sin proyección."
       },
       "interval": "Intervalo del 95 % del cambio anual: de {lo} a {hi} {unit}."
     }

messages/fr.json

@@ -10207,10 +10207,11 @@
           "high": "Si cette droite se prolongeait, elle atteindrait la limite haute de ta plage de référence vers le {date}. C'est une projection, pas une prévision.",
           "low": "Si cette droite se prolongeait, elle atteindrait la limite basse de ta plage de référence vers le {date}. C'est une projection, pas une prévision."
         },
-        "beyond_horizon": "À ce rythme, la droite reste dans ta plage de référence pendant au moins trois ans encore.",
+        "beyond_horizon": "À ce rythme, la droite reste dans ta plage de référence plus de {years} ans, la durée couverte par tes valeurs.",
         "no_exit": "La droite s'éloigne des limites de ta plage de référence.",
         "already_outside": "La droite est déjà hors de ta plage de référence.",
-        "no_clear_trend": "Sur ces valeurs, la variation ne se distingue pas clairement d'une absence de variation, donc aucune projection n'est tracée."
+        "no_clear_trend": "Sur ces valeurs, la variation ne se distingue pas clairement d'une absence de variation, donc aucune projection n'est tracée.",
+        "stale": "La valeur la plus récente date du {date}, il y a plus d’un an. La droite est montrée à cette date, sans projection."
       },
       "interval": "Intervalle à 95 % de la variation annuelle : de {lo} à {hi} {unit}."
     }

messages/it.json

@@ -10207,10 +10207,11 @@
           "high": "Se questa retta proseguisse, raggiungerebbe il limite superiore del tuo intervallo di riferimento verso il {date}. È una proiezione, non una previsione.",
           "low": "Se questa retta proseguisse, raggiungerebbe il limite inferiore del tuo intervallo di riferimento verso il {date}. È una proiezione, non una previsione."
         },
-        "beyond_horizon": "A questo ritmo la retta resta nel tuo intervallo di riferimento per almeno altri tre anni.",
+        "beyond_horizon": "A questo ritmo la retta resta nel tuo intervallo di riferimento per più di {years} anni, il periodo coperto dai tuoi valori.",
         "no_exit": "La retta si allontana dai limiti del tuo intervallo di riferimento.",
         "already_outside": "La retta è già fuori dal tuo intervallo di riferimento.",
-        "no_clear_trend": "Su questi valori la variazione non si distingue chiaramente dall'assenza di variazione, quindi non si proietta nulla."
+        "no_clear_trend": "Su questi valori la variazione non si distingue chiaramente dall'assenza di variazione, quindi non si proietta nulla.",
+        "stale": "Il valore più recente è del {date}, più di un anno fa. La retta è mostrata a quella data, senza proiezione."
       },
       "interval": "Intervallo al 95 % della variazione annua: da {lo} a {hi} {unit}."
     }

messages/ko.json

@@ -10207,10 +10207,11 @@
           "high": "이 직선이 그대로 이어진다면 {date}쯤 참고 범위의 상한에 닿습니다. 이는 연장선일 뿐 예측이 아닙니다.",
           "low": "이 직선이 그대로 이어진다면 {date}쯤 참고 범위의 하한에 닿습니다. 이는 연장선일 뿐 예측이 아닙니다."
         },
-        "beyond_horizon": "이 속도라면 적어도 3년 동안은 참고 범위 안에 머뭅니다.",
+        "beyond_horizon": "이 속도라면 {years}년 넘게 참고 범위 안에 머뭅니다. 측정값이 다루는 기간입니다.",
         "no_exit": "직선이 참고 범위의 경계에서 멀어지고 있습니다.",
         "already_outside": "직선이 이미 참고 범위 밖에 있습니다.",
-        "no_clear_trend": "이 값들에서는 변화가 '변화 없음'과 뚜렷이 구별되지 않아 연장선을 그리지 않습니다."
+        "no_clear_trend": "이 값들에서는 변화가 '변화 없음'과 뚜렷이 구별되지 않아 연장선을 그리지 않습니다.",
+        "stale": "가장 최근 값은 {date}로 1년이 넘었습니다. 직선은 그 시점 기준으로 표시하며 예측은 하지 않습니다."
       },
       "interval": "연간 변화의 95% 구간: {lo}~{hi} {unit}."
     }

messages/nl.json

@@ -10207,10 +10207,11 @@
           "high": "Als deze rechte lijn zo doorliep, zou ze rond {date} de bovengrens van je referentiebereik bereiken. Dat is een doortrekking, geen voorspelling.",
           "low": "Als deze rechte lijn zo doorliep, zou ze rond {date} de ondergrens van je referentiebereik bereiken. Dat is een doortrekking, geen voorspelling."
         },
-        "beyond_horizon": "In dit tempo blijft de lijn nog minstens drie jaar binnen je referentiebereik.",
+        "beyond_horizon": "In dit tempo blijft de lijn langer dan {years} jaar binnen je referentiebereik, de periode die je waarden beslaan.",
         "no_exit": "De lijn loopt weg van de grenzen van je referentiebereik.",
         "already_outside": "De lijn ligt al buiten je referentiebereik.",
-        "no_clear_trend": "Over deze waarden is de verandering niet duidelijk te onderscheiden van geen verandering, dus er wordt niets doorgetrokken."
+        "no_clear_trend": "Over deze waarden is de verandering niet duidelijk te onderscheiden van geen verandering, dus er wordt niets doorgetrokken.",
+        "stale": "De nieuwste waarde is van {date}, meer dan een jaar geleden. De lijn staat op die datum, zonder projectie."
       },
       "interval": "95%-interval van de jaarlijkse verandering: {lo} tot {hi} {unit}."
     }

messages/pl.json

@@ -10207,10 +10207,11 @@
           "high": "Gdyby ta prosta biegła dalej, osiągnęłaby górną granicę twojego zakresu referencyjnego około {date}. To ekstrapolacja, nie prognoza.",
           "low": "Gdyby ta prosta biegła dalej, osiągnęłaby dolną granicę twojego zakresu referencyjnego około {date}. To ekstrapolacja, nie prognoza."
         },
-        "beyond_horizon": "W tym tempie prosta pozostaje w twoim zakresie referencyjnym jeszcze co najmniej trzy lata.",
+        "beyond_horizon": "W tym tempie prosta pozostaje w twoim zakresie referencyjnym dłużej niż {years} lat, czyli okres objęty twoimi wynikami.",
         "no_exit": "Prosta oddala się od granic twojego zakresu referencyjnego.",
         "already_outside": "Prosta jest już poza twoim zakresem referencyjnym.",
-        "no_clear_trend": "Na podstawie tych wyników zmiana nie różni się wyraźnie od braku zmiany, więc nie jest wyznaczana ekstrapolacja."
+        "no_clear_trend": "Na podstawie tych wyników zmiana nie różni się wyraźnie od braku zmiany, więc nie jest wyznaczana ekstrapolacja.",
+        "stale": "Najnowszy wynik pochodzi z {date}, sprzed ponad roku. Prosta jest pokazana na ten dzień, bez projekcji."
       },
       "interval": "95% przedział rocznej zmiany: od {lo} do {hi} {unit}."
     }

src/app/api/biomarkers/[id]/route.ts

@@ -74,7 +74,9 @@ export const GET = apiHandler(
           deletedAt: null,
           value: { not: null },
         },
-        orderBy: { takenAt: "asc" },
+        // Newest first, so a capped read keeps the recent end of the series
+        // (the staleness check reads the newest reading); the fit sorts.
+        orderBy: { takenAt: "desc" },
         take: LAB_TREND_READ_CAP,
         select: { takenAt: true, value: true },
       }),

src/components/labs/__tests__/lab-trend-card.test.tsx

@@ -20,6 +20,7 @@ const OK: BiomarkerTrendDto = {
   pValue: 0.02,
   fittedNow: 130,
   asOf: "2026-10-21",
+  horizonYears: 3,
   projection: "exits",
   exitDate: "2027-11-02",
   exitBound: "high",
@@ -71,4 +72,25 @@ describe("<LabTrendCard>", () => {
     ).toBe("");
     expect(render(undefined)).toBe("");
   });
+
+  it("words a stale trend as of its newest reading, and a span-bound horizon", () => {
+    const stale = render({
+      ...OK,
+      asOf: "2026-01-10",
+      projection: "stale",
+      exitDate: null,
+      exitBound: null,
+    });
+    expect(stale).toContain('data-projection="stale"');
+    expect(stale).toContain("more than a year ago");
+    expect(stale).not.toContain("forecast");
+    const beyond = render({
+      ...OK,
+      horizonYears: 1.5,
+      projection: "beyond_horizon",
+      exitDate: null,
+      exitBound: null,
+    });
+    expect(beyond).toContain("for more than 1.5 years");
+  });
 });

src/components/labs/lab-trend-card.tsx

@@ -48,7 +48,15 @@ export function LabTrendCard({
         })
       : trend.projection === "no_band"
         ? null
-        : t(`labs.trend.projection.${trend.projection}`);
+        : trend.projection === "stale"
+          ? t("labs.trend.projection.stale", {
+              date: fmt.dateShortSmartCalendar(trend.lastAt),
+            })
+          : trend.projection === "beyond_horizon"
+            ? t("labs.trend.projection.beyond_horizon", {
+                years: fmt.number(trend.horizonYears, 1),
+              })
+            : t(`labs.trend.projection.${trend.projection}`);
 
   return (
     <Card data-slot="lab-trend">

src/components/labs/types.ts

@@ -125,13 +125,15 @@ export type BiomarkerTrendDto =
       pValue: number;
       fittedNow: number;
       asOf: string;
+      horizonYears: number;
       projection:
         | "exits"
         | "beyond_horizon"
         | "no_exit"
         | "already_outside"
         | "no_clear_trend"
-        | "no_band";
+        | "no_band"
+        | "stale";
       exitDate: string | null;
       exitBound: "low" | "high" | null;
     }

src/lib/labs/__tests__/lab-trend.test.ts

@@ -128,4 +128,50 @@ describe("computeLabTrend", () => {
       computeLabTrend(falling, { low: 90, high: 140 }, atYears(2)),
     ).toMatchObject({ projection: "exits", exitBound: "low" });
   });
+
+  it("never carries the line further ahead than the readings reach back", () => {
+    // 10 a year over one year (span 1.0); band top 125 sits 1.5 years past
+    // the last reading. Inside the three-year cap, outside the one-year span.
+    const short = readings([
+      [0, 100],
+      [0.5, 105],
+      [1, 110],
+    ]);
+    expect(
+      computeLabTrend(short, { low: 70, high: 125 }, atYears(1)),
+    ).toMatchObject({ projection: "beyond_horizon", horizonYears: 1 });
+    // The same line with a top of 118 meets it 0.8 years out: projected.
+    expect(
+      computeLabTrend(short, { low: 70, high: 118 }, atYears(1)),
+    ).toMatchObject({ projection: "exits", exitBound: "high" });
+  });
+
+  it("reports a stale series as of its last reading, without a projection", () => {
+    const line = readings([
+      [0, 100],
+      [1, 110],
+      [2, 120],
+    ]);
+    // Last reading two years before "now": evaluated on that day.
+    const stale = computeLabTrend(line, { low: 70, high: 125 }, atYears(4));
+    expect(stale).toMatchObject({
+      status: "ok",
+      projection: "stale",
+      exitDate: null,
+      exitBound: null,
+      fittedNow: 120,
+      slopePerYear: 10,
+    });
+    if (stale.status !== "ok") throw new Error("expected ok");
+    expect(stale.asOf).toBe(stale.lastAt);
+    // Carried to today the line would read 140, above the band: a stale
+    // series never says "already outside".
+    expect(
+      computeLabTrend(line, { low: 70, high: 115 }, atYears(4)),
+    ).toMatchObject({ projection: "stale" });
+    // Eleven months after the last reading it is still current.
+    expect(
+      computeLabTrend(line, { low: 70, high: 200 }, atYears(2.9)),
+    ).toMatchObject({ projection: "beyond_horizon" });
+  });
 });

src/lib/labs/lab-trend.ts

@@ -13,7 +13,14 @@
  * The slope carries its 95 % confidence interval (Student t at n − 2 degrees
  * of freedom). A projection is offered only when that interval excludes zero,
  * the line is inside the band today and heads toward a bound it reaches
- * within {@link LAB_PROJECTION_HORIZON_YEARS} years. It is a straight-line
+ * within the horizon: {@link LAB_PROJECTION_HORIZON_YEARS} years, or the span
+ * the readings cover when that is shorter, so the line is never carried
+ * further ahead than the data reaches back.
+ *
+ * A marker whose newest reading is older than {@link LAB_TREND_STALE_DAYS}
+ * days gets no projection at all (`stale`): the line is evaluated on the day
+ * of that reading and reported as of then, with no exit date and no
+ * "already outside" verdict about a today the readings say nothing about. It is a straight-line
  * extrapolation, labelled as one wherever it is shown, never a forecast of
  * the body and never a risk statement: lab values plateau, respond to
  * treatment and carry assay noise a line does not know about. With three
@@ -29,6 +36,8 @@ import { dateOnlyKey } from "@/lib/tz/date-only";
 export const LAB_TREND_MIN_VALUES = 3;
 export const LAB_TREND_MIN_SPAN_DAYS = 365;
 export const LAB_PROJECTION_HORIZON_YEARS = 3;
+/** Newest reading older than this: the trend is reported as of that reading. */
+export const LAB_TREND_STALE_DAYS = 365;
 
 const DAY_MS = 86_400_000;
 const YEAR_DAYS = 365.25;
@@ -45,7 +54,12 @@ export type LabTrendProjection =
   /** The slope's interval includes zero: no projection is drawn. */
   | "no_clear_trend"
   /** The marker has no reference band to leave. */
-  | "no_band";
+  | "no_band"
+  /**
+   * The newest reading is older than {@link LAB_TREND_STALE_DAYS} days: the
+   * line is reported as of that reading (`asOf` = `lastAt`), not projected.
+   */
+  | "stale";
 
 export interface LabTrendOk {
   status: "ok";
@@ -62,7 +76,13 @@ export interface LabTrendOk {
   pValue: number;
   /** The line's value on `asOf`. */
   fittedNow: number;
+  /** Today, or the newest reading's day when the trend is `stale`. */
   asOf: string;
+  /**
+   * How far ahead a bound may be met and still count as `exits`: three years,
+   * or the readings' span when shorter.
+   */
+  horizonYears: number;
   projection: LabTrendProjection;
   /** Set only for `exits`: the day the line meets `exitBound`. */
   exitDate: string | null;
@@ -136,14 +156,23 @@ export function computeLabTrend(
         : 0
       : twoSidedPFromT(Math.abs(fit.slope / se), df);
 
-  const xNow = (now.getTime() - t0) / DAY_MS / YEAR_DAYS;
+  const tLast = points[n - 1].t;
+  const stale = now.getTime() - tLast > LAB_TREND_STALE_DAYS * DAY_MS;
+  // A stale series is read on its own last day, never carried to today.
+  const tAsOf = stale ? tLast : now.getTime();
+  const xNow = (tAsOf - t0) / DAY_MS / YEAR_DAYS;
   const fittedNow = fit.intercept + fit.slope * xNow;
+  const horizonYears = Math.min(
+    LAB_PROJECTION_HORIZON_YEARS,
+    (tLast - t0) / DAY_MS / YEAR_DAYS,
+  );
 
   let projection: LabTrendProjection;
   let exitDate: string | null = null;
   let exitBound: "low" | "high" | null = null;
   const hasBand = band.low != null || band.high != null;
-  if (!hasBand) projection = "no_band";
+  if (stale) projection = "stale";
+  else if (!hasBand) projection = "no_band";
   else if (!(lo > 0 || hi < 0)) projection = "no_clear_trend";
   else if (
     (band.low != null && fittedNow < band.low) ||
@@ -156,7 +185,7 @@ export function computeLabTrend(
     else {
       const xCross = (bound - fit.intercept) / fit.slope;
       const yearsAhead = xCross - xNow;
-      if (yearsAhead > LAB_PROJECTION_HORIZON_YEARS) {
+      if (yearsAhead > horizonYears) {
         projection = "beyond_horizon";
       } else {
         projection = "exits";
@@ -176,7 +205,8 @@ export function computeLabTrend(
     slopeCi95: [round(lo, 4), round(hi, 4)],
     pValue: round(pValue, 6),
     fittedNow: round(fittedNow, 4),
-    asOf: dayOf(now.getTime()),
+    asOf: dayOf(tAsOf),
+    horizonYears: round(horizonYears, 2),
     projection,
     exitDate,
     exitBound,

src/lib/openapi/routes/biomarkers.ts

@@ -93,7 +93,16 @@ const labTrend = z
         .describe("95 % interval of the slope (Student t at n − 2 df)."),
       pValue: z.number(),
       fittedNow: z.number().describe("The line's value on `asOf`."),
-      asOf: z.string().describe("YYYY-MM-DD the line was evaluated on."),
+      asOf: z
+        .string()
+        .describe(
+          "YYYY-MM-DD the line was evaluated on: today, or `lastAt` when `projection` is `stale`.",
+        ),
+      horizonYears: z
+        .number()
+        .describe(
+          "How far ahead a bound may be met and still count as `exits`: three years, or the readings' span when shorter.",
+        ),
       projection: z.enum([
         "exits",
         "beyond_horizon",
@@ -101,6 +110,7 @@ const labTrend = z
         "already_outside",
         "no_clear_trend",
         "no_band",
+        "stale",
       ]),
       exitDate: z
         .string()
@@ -120,7 +130,7 @@ const labTrend = z
   .meta({
     id: "BiomarkerTrend",
     description:
-      "v1.44 — the least-squares line through every numeric reading of the marker (all stored in the marker's unit). Needs at least three readings spanning at least 365 days, else `insufficient`. `projection` places the line against the marker's band: `exits` (with `exitDate`) only when the slope's 95 % interval excludes zero, the line is inside the band today and reaches a bound within three years. Server-computed; clients render it as given.",
+      "v1.44 — the least-squares line through every numeric reading of the marker (all stored in the marker's unit). Needs at least three readings spanning at least 365 days, else `insufficient`. `projection` places the line against the marker's band: `exits` (with `exitDate`) only when the slope's 95 % interval excludes zero, the line is inside the band today and reaches a bound within `horizonYears` (three years, or the readings' span when shorter). `stale` when the newest reading is more than 365 days old: the line is then reported as of `lastAt`, with no projection. Server-computed; clients render it as given.",
   });
 
 const biomarkerDetail = biomarkerRow