diff --git a/docs/api/openapi.yaml b/docs/api/openapi.yaml
index f00512ce5..148febd8d 100644
--- a/docs/api/openapi.yaml
+++ b/docs/api/openapi.yaml
@@ -904,7 +904,8 @@ paths:
       tags:
         - Cycle
       summary: Change the calendar subscription's options (#1350)
-      description: Field-by-field update of the options. The URL does not change; the feed's next fetch serves the new content.
+      description: Field-by-field update of the options. The URL does not change; the feed's next fetch serves the new
+        content. A change saved while the link is being replaced applies to the link that stays live.
       requestBody:
         required: true
         content:
@@ -927,6 +928,13 @@ paths:
             application/json:
               schema:
                 $ref: "#/components/schemas/ErrorEnvelope"
+        "409":
+          description: The link was replaced twice while the change was being saved (`cycle.feed.exists`); nothing changed, and
+            sending it again applies it to the link that is live now.
+          content:
+            application/json:
+              schema:
+                $ref: "#/components/schemas/ErrorEnvelope"
         "422": *a4
         "429": *a12
     delete:
@@ -959,7 +967,8 @@ paths:
       summary: Replace the calendar subscription's link (#1350)
       description: "One transaction: the live link is revoked and a new one minted with the same options, the forecast style
         included. Returns the new URL EXACTLY ONCE. Calendars using the old link stop updating. Of two rotations racing,
-        the one that loses answers 409 `cycle.feed.exists` and the winner's link stands."
+        the one that loses answers 409 `cycle.feed.exists` and the winner's link stands; a rotation racing the
+        subscription being turned off answers 404 `cycle.feed.none` and the subscription stays off."
       responses:
         "201": *a13
         "401": *a14
diff --git a/messages/de.json b/messages/de.json
index c9df357c7..e7bc53513 100644
--- a/messages/de.json
+++ b/messages/de.json
@@ -4019,7 +4019,7 @@
       "gki": {
         "description": "Blutzucker geteilt durch Ketone, für jeden Ketonwert mit einem Blutzuckerwert innerhalb von 15 Minuten.",
         "emptyTitle": "Noch kein Index",
-        "emptyDescription": "Er erscheint, sobald zu einem Ketonwert ein Blutzuckerwert zur selben Zeit oder innerhalb von 15 Minuten vorliegt.",
+        "emptyDescription": "Er erscheint, sobald zu einem Ketonwert über null ein Blutzuckerwert zur selben Zeit oder innerhalb von 15 Minuten vorliegt.",
         "latest": "Zuletzt {value}: Blutzucker {glucose} {unit} durch Ketone {ketones} {unit}, {date}."
       }
     },
@@ -13710,7 +13710,7 @@
     "valuesAllFew": "Alle {count} Werte",
     "valuesAllOther": "Alle {count} Werte",
     "valuesFewer": "Weniger Werte",
-    "gkiPair": "Blutzucker {glucose} / Ketone {ketones}",
+    "gkiPair": "Blutzucker {glucose} {unit} / Ketone {ketones} {unit}",
     "gkiCountOne": "Letzter von {count}",
     "gkiCountFew": "Letzter von {count}",
     "gkiCountOther": "Letzter von {count}",
diff --git a/messages/en.json b/messages/en.json
index 48ed32245..f2d3a970d 100644
--- a/messages/en.json
+++ b/messages/en.json
@@ -4019,7 +4019,7 @@
       "gki": {
         "description": "Glucose divided by ketones, for each ketone reading with a glucose reading within 15 minutes.",
         "emptyTitle": "No index yet",
-        "emptyDescription": "It appears once a ketone reading has a glucose reading taken at the same time or within 15 minutes.",
+        "emptyDescription": "It appears once a ketone reading above zero has a glucose reading taken at the same time or within 15 minutes.",
         "latest": "Latest {value}: glucose {glucose} {unit} over ketones {ketones} {unit}, {date}."
       }
     },
@@ -13710,7 +13710,7 @@
     "valuesAllFew": "All {count} values",
     "valuesAllOther": "All {count} values",
     "valuesFewer": "Fewer values",
-    "gkiPair": "Glucose {glucose} / ketones {ketones}",
+    "gkiPair": "Glucose {glucose} {unit} / ketones {ketones} {unit}",
     "gkiCountOne": "Latest of {count}",
     "gkiCountFew": "Latest of {count}",
     "gkiCountOther": "Latest of {count}",
diff --git a/messages/es.json b/messages/es.json
index 6ea863120..aea9a878c 100644
--- a/messages/es.json
+++ b/messages/es.json
@@ -4019,7 +4019,7 @@
       "gki": {
         "description": "Glucosa dividida por cetonas, para cada lectura de cetonas con una de glucosa en un margen de 15 minutos.",
         "emptyTitle": "Aún no hay índice",
-        "emptyDescription": "Aparece cuando una lectura de cetonas tiene una de glucosa tomada a la misma hora o en un margen de 15 minutos.",
+        "emptyDescription": "Aparece cuando una lectura de cetonas mayor que cero tiene una de glucosa tomada a la misma hora o en un margen de 15 minutos.",
         "latest": "Último {value}: glucosa {glucose} {unit} entre cetonas {ketones} {unit}, {date}."
       }
     },
@@ -13710,7 +13710,7 @@
     "valuesAllFew": "Los {count} valores",
     "valuesAllOther": "Los {count} valores",
     "valuesFewer": "Menos valores",
-    "gkiPair": "Glucosa {glucose} / cetonas {ketones}",
+    "gkiPair": "Glucosa {glucose} {unit} / cetonas {ketones} {unit}",
     "gkiCountOne": "Último de {count}",
     "gkiCountFew": "Último de {count}",
     "gkiCountOther": "Último de {count}",
diff --git a/messages/fr.json b/messages/fr.json
index 0f19fac15..8ee397390 100644
--- a/messages/fr.json
+++ b/messages/fr.json
@@ -4019,7 +4019,7 @@
       "gki": {
         "description": "Glycémie divisée par les cétones, pour chaque relevé de cétones accompagné d’une glycémie à 15 minutes près.",
         "emptyTitle": "Pas encore d’indice",
-        "emptyDescription": "Il apparaît dès qu’un relevé de cétones a une glycémie prise au même moment ou à 15 minutes près.",
+        "emptyDescription": "Il apparaît dès qu’un relevé de cétones supérieur à zéro a une glycémie prise au même moment ou à 15 minutes près.",
         "latest": "Dernier {value} : glycémie {glucose} {unit} sur cétones {ketones} {unit}, {date}."
       }
     },
@@ -13710,7 +13710,7 @@
     "valuesAllFew": "Les {count} valeurs",
     "valuesAllOther": "Les {count} valeurs",
     "valuesFewer": "Moins de valeurs",
-    "gkiPair": "Glycémie {glucose} / cétones {ketones}",
+    "gkiPair": "Glycémie {glucose} {unit} / cétones {ketones} {unit}",
     "gkiCountOne": "Dernier sur {count}",
     "gkiCountFew": "Dernier sur {count}",
     "gkiCountOther": "Dernier sur {count}",
diff --git a/messages/it.json b/messages/it.json
index 17b61f5a1..13db50090 100644
--- a/messages/it.json
+++ b/messages/it.json
@@ -4019,7 +4019,7 @@
       "gki": {
         "description": "Glicemia divisa per i chetoni, per ogni lettura di chetoni con una glicemia entro 15 minuti.",
         "emptyTitle": "Ancora nessun indice",
-        "emptyDescription": "Compare quando una lettura di chetoni ha una glicemia presa allo stesso momento o entro 15 minuti.",
+        "emptyDescription": "Compare quando una lettura di chetoni superiore a zero ha una glicemia presa allo stesso momento o entro 15 minuti.",
         "latest": "Ultimo {value}: glicemia {glucose} {unit} su chetoni {ketones} {unit}, {date}."
       }
     },
@@ -13710,7 +13710,7 @@
     "valuesAllFew": "Tutti i {count} valori",
     "valuesAllOther": "Tutti i {count} valori",
     "valuesFewer": "Meno valori",
-    "gkiPair": "Glicemia {glucose} / chetoni {ketones}",
+    "gkiPair": "Glicemia {glucose} {unit} / chetoni {ketones} {unit}",
     "gkiCountOne": "Ultimo di {count}",
     "gkiCountFew": "Ultimo di {count}",
     "gkiCountOther": "Ultimo di {count}",
diff --git a/messages/ko.json b/messages/ko.json
index 213235474..0e4464586 100644
--- a/messages/ko.json
+++ b/messages/ko.json
@@ -4019,7 +4019,7 @@
       "gki": {
         "description": "15분 이내에 혈당 측정값이 있는 케톤 측정마다 혈당을 케톤으로 나눈 값이에요.",
         "emptyTitle": "아직 지수가 없어요",
-        "emptyDescription": "케톤 측정과 같은 시각이나 15분 이내에 잰 혈당이 있으면 나타나요.",
+        "emptyDescription": "0보다 큰 케톤 측정과 같은 시각이나 15분 이내에 잰 혈당이 있으면 나타나요.",
         "latest": "최근 {value}: 혈당 {glucose} {unit} ÷ 케톤 {ketones} {unit}, {date}."
       }
     },
@@ -13710,7 +13710,7 @@
     "valuesAllFew": "수치 {count}개 모두",
     "valuesAllOther": "수치 {count}개 모두",
     "valuesFewer": "수치 줄여 보기",
-    "gkiPair": "혈당 {glucose} / 케톤 {ketones}",
+    "gkiPair": "혈당 {glucose} {unit} / 케톤 {ketones} {unit}",
     "gkiCountOne": "{count}개 중 최근",
     "gkiCountFew": "{count}개 중 최근",
     "gkiCountOther": "{count}개 중 최근",
diff --git a/messages/nl.json b/messages/nl.json
index 57be9591e..c78d5a4ab 100644
--- a/messages/nl.json
+++ b/messages/nl.json
@@ -4019,7 +4019,7 @@
       "gki": {
         "description": "Glucose gedeeld door ketonen, voor elke ketonmeting met een glucosemeting binnen 15 minuten.",
         "emptyTitle": "Nog geen index",
-        "emptyDescription": "Hij verschijnt zodra een ketonmeting een glucosemeting op hetzelfde moment of binnen 15 minuten heeft.",
+        "emptyDescription": "Hij verschijnt zodra een ketonmeting boven nul een glucosemeting op hetzelfde moment of binnen 15 minuten heeft.",
         "latest": "Laatst {value}: glucose {glucose} {unit} gedeeld door ketonen {ketones} {unit}, {date}."
       }
     },
@@ -13710,7 +13710,7 @@
     "valuesAllFew": "Alle {count} waarden",
     "valuesAllOther": "Alle {count} waarden",
     "valuesFewer": "Minder waarden",
-    "gkiPair": "Glucose {glucose} / ketonen {ketones}",
+    "gkiPair": "Glucose {glucose} {unit} / ketonen {ketones} {unit}",
     "gkiCountOne": "Laatste van {count}",
     "gkiCountFew": "Laatste van {count}",
     "gkiCountOther": "Laatste van {count}",
diff --git a/messages/pl.json b/messages/pl.json
index 5f4636245..a411d2f18 100644
--- a/messages/pl.json
+++ b/messages/pl.json
@@ -4019,7 +4019,7 @@
       "gki": {
         "description": "Glukoza podzielona przez ketony, dla każdego odczytu ketonów z odczytem glukozy w ciągu 15 minut.",
         "emptyTitle": "Brak jeszcze indeksu",
-        "emptyDescription": "Pojawi się, gdy do odczytu ketonów będzie odczyt glukozy z tej samej chwili lub w ciągu 15 minut.",
+        "emptyDescription": "Pojawi się, gdy do odczytu ketonów powyżej zera będzie odczyt glukozy z tej samej chwili lub w ciągu 15 minut.",
         "latest": "Ostatnio {value}: glukoza {glucose} {unit} przez ketony {ketones} {unit}, {date}."
       }
     },
@@ -13710,7 +13710,7 @@
     "valuesAllFew": "Wszystkie {count} wartości",
     "valuesAllOther": "Wszystkie {count} wartości",
     "valuesFewer": "Mniej wartości",
-    "gkiPair": "Glukoza {glucose} / ketony {ketones}",
+    "gkiPair": "Glukoza {glucose} {unit} / ketony {ketones} {unit}",
     "gkiCountOne": "Ostatni z {count}",
     "gkiCountFew": "Ostatni z {count}",
     "gkiCountOther": "Ostatni z {count}",
diff --git a/messages/pt-BR.json b/messages/pt-BR.json
index 3d09866b4..754f44ed9 100644
--- a/messages/pt-BR.json
+++ b/messages/pt-BR.json
@@ -4019,7 +4019,7 @@
       "gki": {
         "description": "Glicose dividida pelas cetonas, para cada leitura de cetonas com uma de glicose em até 15 minutos.",
         "emptyTitle": "Ainda não há índice",
-        "emptyDescription": "Ele aparece quando uma leitura de cetonas tem uma de glicose feita no mesmo horário ou em até 15 minutos.",
+        "emptyDescription": "Ele aparece quando uma leitura de cetonas acima de zero tem uma de glicose feita no mesmo horário ou em até 15 minutos.",
         "latest": "Último {value}: glicose {glucose} {unit} sobre cetonas {ketones} {unit}, {date}."
       }
     },
@@ -13710,7 +13710,7 @@
     "valuesAllFew": "Todos os {count} valores",
     "valuesAllOther": "Todos os {count} valores",
     "valuesFewer": "Menos valores",
-    "gkiPair": "Glicose {glucose} / cetonas {ketones}",
+    "gkiPair": "Glicose {glucose} {unit} / cetonas {ketones} {unit}",
     "gkiCountOne": "Último de {count}",
     "gkiCountFew": "Último de {count}",
     "gkiCountOther": "Último de {count}",
diff --git a/messages/ru.json b/messages/ru.json
index 9a206fa9f..f3c9d7077 100644
--- a/messages/ru.json
+++ b/messages/ru.json
@@ -4019,7 +4019,7 @@
       "gki": {
         "description": "Глюкоза, делённая на кетоны, для каждого измерения кетонов с измерением глюкозы в пределах 15 минут.",
         "emptyTitle": "Индекса пока нет",
-        "emptyDescription": "Он появится, когда к измерению кетонов будет измерение глюкозы в то же время или в пределах 15 минут.",
+        "emptyDescription": "Он появится, когда к измерению кетонов выше нуля будет измерение глюкозы в то же время или в пределах 15 минут.",
         "latest": "Последний {value}: глюкоза {glucose} {unit} на кетоны {ketones} {unit}, {date}."
       }
     },
@@ -13710,7 +13710,7 @@
     "valuesAllFew": "Все {count} значения",
     "valuesAllOther": "Все {count} значений",
     "valuesFewer": "Меньше значений",
-    "gkiPair": "Глюкоза {glucose} / кетоны {ketones}",
+    "gkiPair": "Глюкоза {glucose} {unit} / кетоны {ketones} {unit}",
     "gkiCountOne": "Последний из {count}",
     "gkiCountFew": "Последний из {count}",
     "gkiCountOther": "Последний из {count}",
diff --git a/src/__tests__/dense-measurement-read-guard.test.ts b/src/__tests__/dense-measurement-read-guard.test.ts
index 34880beb6..1ddba1dce 100644
--- a/src/__tests__/dense-measurement-read-guard.test.ts
+++ b/src/__tests__/dense-measurement-read-guard.test.ts
@@ -151,8 +151,6 @@ const ALLOWED_SQL: Record<string, string> = {
     "Selects from `unnest` of the type list; `measurements` is read only inside COUNT scalar subqueries, before the fold window for a type the DAY rollups cover.",
   "lib/measurements/read-glucose-ketone-index.ts::1":
     "Ketone readings in the window: typed off a fingerstick meter, a few a day at most. Each one is paired with a glucose reading, so the rows themselves are needed.",
-  "lib/measurements/read-glucose-ketone-index.ts::2":
-    "Glucose rows only within 15 minutes of one of those ketone readings (`EXISTS`): a handful per fingerstick even under a sensor, never the window's glucose series.",
   "lib/dashboard/summary-reads.ts::2":
     "Selects from `generate_series` of the streak window's local days; `measurements` is read inside `EXISTS`, one row per day at most.",
 };
diff --git a/src/components/day/day-gki-tile.tsx b/src/components/day/day-gki-tile.tsx
index d078a2e8a..1dd807099 100644
--- a/src/components/day/day-gki-tile.tsx
+++ b/src/components/day/day-gki-tile.tsx
@@ -4,6 +4,7 @@ import Link from "next/link";
 
 import type { DayResponse } from "@/lib/day/contract";
 import { useFormatters, useTranslations } from "@/lib/i18n/context";
+import { GKI_COMPONENT_UNIT } from "@/lib/measurements/glucose-ketone-index";
 
 type DayGki = NonNullable<DayResponse["glucoseKetoneIndex"]>[number];
 
@@ -38,6 +39,7 @@ export function DayGkiTile({ points }: { points: readonly DayGki[] }) {
             : t("day.gkiPair", {
                 glucose: fmt.number(latest.glucoseMmol, 1),
                 ketones: fmt.number(latest.ketonesMmol, 1),
+                unit: GKI_COMPONENT_UNIT,
               })}
         </span>
       </Link>
diff --git a/src/lib/measurements/__tests__/glucose-ketone-index.test.ts b/src/lib/measurements/__tests__/glucose-ketone-index.test.ts
index 2c91dee3c..27ead05d2 100644
--- a/src/lib/measurements/__tests__/glucose-ketone-index.test.ts
+++ b/src/lib/measurements/__tests__/glucose-ketone-index.test.ts
@@ -115,6 +115,18 @@ describe("pairGlucoseKetoneIndex", () => {
     expect(byTime?.glucoseId).toBe("g-earlier");
   });
 
+  it("gives the same pair for a full tie whatever order the rows came in", () => {
+    const a = reading("g-a", 0, 90, "APPLE_HEALTH");
+    const b = reading("g-b", 0, 110, "NIGHTSCOUT");
+    for (const glucose of [
+      [a, b],
+      [b, a],
+    ]) {
+      const [point] = pairGlucoseKetoneIndex([reading("k1", 0, 1)], glucose);
+      expect(point?.glucoseId).toBe("g-a");
+    }
+  });
+
   it("answers in ketone order whatever order the readings came in", () => {
     const points = pairGlucoseKetoneIndex(
       [reading("k2", 60, 2), reading("k1", 0, 1)],
diff --git a/src/lib/measurements/glucose-ketone-index.ts b/src/lib/measurements/glucose-ketone-index.ts
index 46bf54dfa..50e130994 100644
--- a/src/lib/measurements/glucose-ketone-index.ts
+++ b/src/lib/measurements/glucose-ketone-index.ts
@@ -106,8 +106,12 @@ export function pairGlucoseKetoneIndex(
   ketones: readonly GkiReading[],
   glucose: readonly GkiReading[],
 ): GlucoseKetoneIndexPoint[] {
+  // The id breaks the last tie, so two glucose readings alike in time and
+  // source always give the same pair, whatever order the rows came in.
   const sortedGlucose = [...glucose].sort(
-    (a, b) => a.measuredAt.getTime() - b.measuredAt.getTime(),
+    (a, b) =>
+      a.measuredAt.getTime() - b.measuredAt.getTime() ||
+      a.id.localeCompare(b.id),
   );
   const sortedKetones = [...ketones].sort(
     (a, b) =>
diff --git a/src/lib/measurements/read-glucose-ketone-index.ts b/src/lib/measurements/read-glucose-ketone-index.ts
index cc3afe988..bb17fb7a6 100644
--- a/src/lib/measurements/read-glucose-ketone-index.ts
+++ b/src/lib/measurements/read-glucose-ketone-index.ts
@@ -15,7 +15,6 @@ import { prisma } from "@/lib/db";
 
 import {
   GKI_PAIRING_WINDOW_MINUTES,
-  GKI_PAIRING_WINDOW_MS,
   pairGlucoseKetoneIndex,
   type GkiReading,
   type GlucoseKetoneIndexPoint,
@@ -62,25 +61,24 @@ export async function readGlucoseKetoneIndex(args: {
   if (ketones.length === 0) return [];
   // An interval between two stored instants: no zone enters the arithmetic.
   const reach = `${GKI_PAIRING_WINDOW_MINUTES} minutes`;
+  // Driven from the ketone side: one index range per ketone reading on
+  // (user_id, type, measured_at), so a person with years of CGM glucose
+  // reads only the glucose around their fingersticks, never the series. A
+  // correlated EXISTS over a range had no equality to drive it the other
+  // way and walked every glucose row in the window.
+  const at = ketones.map((k) => k.measured_at);
   const glucose = await prisma.$queryRaw<Row[]>`
-    SELECT g."id", g."value", g."measured_at", g."source"::text AS "source"
-    FROM measurements g
-    WHERE g."user_id" = ${userId}
-      AND g."type" = 'BLOOD_GLUCOSE'::"measurement_type"
-      AND g."deleted_at" IS NULL
-      AND g."measured_at" >= ${new Date(from.getTime() - GKI_PAIRING_WINDOW_MS)}
-      AND g."measured_at" <= ${new Date(to.getTime() + GKI_PAIRING_WINDOW_MS)}
-      AND EXISTS (
-        SELECT 1 FROM measurements k
-        WHERE k."user_id" = ${userId}
-          AND k."type" = 'BLOOD_KETONES'::"measurement_type"
-          AND k."deleted_at" IS NULL
-          AND k."measured_at" >= ${from}
-          AND k."measured_at" < ${to}
-          AND k."value" > 0
-          AND k."measured_at" BETWEEN g."measured_at" - ${reach}::interval
-                                  AND g."measured_at" + ${reach}::interval
-      )
+    SELECT DISTINCT g."id", g."value", g."measured_at", g."source"
+    FROM unnest(${at}::timestamp(3)[]) AS k("at")
+    CROSS JOIN LATERAL (
+      SELECT m."id", m."value", m."measured_at", m."source"::text AS "source"
+      FROM measurements m
+      WHERE m."user_id" = ${userId}
+        AND m."type" = 'BLOOD_GLUCOSE'::"measurement_type"
+        AND m."deleted_at" IS NULL
+        AND m."measured_at" BETWEEN k."at" - ${reach}::interval
+                                AND k."at" + ${reach}::interval
+    ) g
   `;
   return pairGlucoseKetoneIndex(ketones.map(toReading), glucose.map(toReading));
 }