diff --git a/src/components/insights/mood/mood-dimension-trends.tsx b/src/components/insights/mood/mood-dimension-trends.tsx
index b9aa7af6e..2b06f7ca8 100644
--- a/src/components/insights/mood/mood-dimension-trends.tsx
+++ b/src/components/insights/mood/mood-dimension-trends.tsx
@@ -12,7 +12,11 @@ import {
 } from "recharts";
 
 import { useTranslations } from "@/lib/i18n/context";
-import { MOOD_DIMENSIONS } from "@/lib/mood/dimensions";
+import {
+  MOOD_DIMENSIONS,
+  MOOD_DIMENSION_WINDOWS,
+  type MoodDimensionWindow,
+} from "@/lib/mood/dimensions";
 import { cn } from "@/lib/utils";
 
 /**
@@ -50,9 +54,6 @@ export interface MoodDimensionSummaryData {
   series: MoodDimensionPointData[];
 }
 
-const WINDOWS = [7, 30, 90] as const;
-type Window = (typeof WINDOWS)[number];
-
 /** One colour per dimension, from the same semantic set the other charts use. */
 const COLOR_BY_KEY: Record<string, string> = {
   a1: "var(--chart-1)",
@@ -64,7 +65,7 @@ const COLOR_BY_KEY: Record<string, string> = {
 
 function meanForWindow(
   summary: MoodDimensionSummaryData,
-  window: Window,
+  window: MoodDimensionWindow,
 ): number | null {
   if (window === 7) return summary.avg7;
   if (window === 30) return summary.avg30;
@@ -77,7 +78,7 @@ export function MoodDimensionTrends({
   dimensions: MoodDimensionSummaryData[];
 }) {
   const { t } = useTranslations();
-  const [window, setWindow] = useState<Window>(30);
+  const [window, setWindow] = useState<MoodDimensionWindow>(30);
 
   const present = dimensions.filter((d) => d.present);
   const missing = dimensions.filter((d) => !d.present);
@@ -115,7 +116,7 @@ export function MoodDimensionTrends({
   return (
     <div className="space-y-3" data-slot="mood-dimension-trends">
       <div className="flex flex-wrap items-center gap-1.5">
-        {WINDOWS.map((option) => (
+        {MOOD_DIMENSION_WINDOWS.map((option) => (
           <button
             key={option}
             type="button"
diff --git a/src/lib/insights/mood-aggregates.ts b/src/lib/insights/mood-aggregates.ts
index 6beb8b343..2db2d22ab 100644
--- a/src/lib/insights/mood-aggregates.ts
+++ b/src/lib/insights/mood-aggregates.ts
@@ -41,7 +41,6 @@ import {
 } from "@/lib/insights/mood-dimension-series";
 export {
   computeMoodDimensionSeries,
-  MOOD_DIMENSION_WINDOWS,
   type MoodDimensionPoint,
   type MoodDimensionSummary,
 } from "@/lib/insights/mood-dimension-series";
diff --git a/src/lib/insights/mood-dimension-series.ts b/src/lib/insights/mood-dimension-series.ts
index 841741d69..9a221e051 100644
--- a/src/lib/insights/mood-dimension-series.ts
+++ b/src/lib/insights/mood-dimension-series.ts
@@ -14,14 +14,14 @@
  * is indistinguishable from a given one — and five is the answer somebody
  * gives on a genuinely average day.
  */
-import { MOOD_DIMENSIONS, type MoodDimensionKey } from "@/lib/mood/dimensions";
+import {
+  MOOD_DIMENSIONS,
+  MOOD_DIMENSION_WINDOWS,
+  type MoodDimensionKey,
+} from "@/lib/mood/dimensions";
 import { dayKeyAgeInDays } from "@/lib/insights/measurement-freshness";
 import { round } from "@/lib/insights/status-shared";
 
-/** Windows the trend reports, in days. Concept §10.1. */
-export const MOOD_DIMENSION_WINDOWS = [7, 30, 90] as const;
-export type MoodDimensionWindow = (typeof MOOD_DIMENSION_WINDOWS)[number];
-
 /** One day's mean for one dimension. */
 export interface MoodDimensionPoint {
   /** `YYYY-MM-DD`, the row's own local day key. */
diff --git a/src/lib/mood/dimensions.ts b/src/lib/mood/dimensions.ts
index 8f692d6cd..3f359ea8e 100644
--- a/src/lib/mood/dimensions.ts
+++ b/src/lib/mood/dimensions.ts
@@ -107,6 +107,19 @@ export const MOOD_DIMENSIONS: readonly MoodDimension[] = [
   },
 ] as const;
 
+/**
+ * Windows the per-dimension trend reports, in days. Concept §10.1.
+ *
+ * Here rather than beside the calculator that averages over them, because the
+ * chart offering the choice needs the same three numbers and cannot import
+ * that module: it reaches Prisma two hops down, and a client component that
+ * pulled it in would drag the database client into the browser bundle. This
+ * module is pure by construction, which is what makes it the one place both
+ * ends can agree on.
+ */
+export const MOOD_DIMENSION_WINDOWS = [7, 30, 90] as const;
+export type MoodDimensionWindow = (typeof MOOD_DIMENSION_WINDOWS)[number];
+
 /** Lowest value any dimension accepts. */
 export const MOOD_DIMENSION_MIN = 0;
 /** Highest value any dimension accepts. */