diff --git a/CHANGELOG.md b/CHANGELOG.md
index e93ca89f7..f7e8b3a4f 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -2,6 +2,27 @@
 
 ## [Unreleased]
 
+## [1.32.27] — 2026-07-25
+
+Target and threshold panels now follow the metric and imperial preference. The
+previous release listed this as the one place still reading in kilograms and
+Celsius: with imperial selected a weight chart read in pounds while the target
+reference right below it read in kilograms.
+
+- **Target ranges read in your unit.** On the weight insight page the target
+  band, the range bar, the status pill, and the 30 day average all read in
+  pounds when imperial is selected. Body water and bone mass follow the same
+  rule in the threshold settings.
+- **Editing a target works in the unit you see.** The target editor and the
+  threshold settings seed their fields from the stored value converted to your
+  unit, check what you type against limits expressed in that same unit, and
+  convert back before saving. A value typed at the displayed limit is accepted
+  instead of being rejected against a kilogram bound you never saw. Saving and
+  reopening shows the number you typed.
+- **Storage is unchanged.** Targets are still kept in canonical SI, and a metric
+  account's saved values are untouched by this release.
+- **Known remaining.** Height is still entered in centimetres.
+
 ## [1.32.26] — 2026-07-25
 
 The metric and imperial display preference is now applied everywhere your
diff --git a/docs/api/openapi.yaml b/docs/api/openapi.yaml
index 35d684eff..68f1a5e20 100644
--- a/docs/api/openapi.yaml
+++ b/docs/api/openapi.yaml
@@ -1,7 +1,7 @@
 openapi: 3.1.0
 info:
   title: HealthLog API
-  version: 1.32.26
+  version: 1.32.27
   description: >-
     Self-hosted personal-health-tracking PWA — public API surface for the iOS native client and external ingest.
 
diff --git a/package.json b/package.json
index a39b086fa..3acabb0c1 100644
--- a/package.json
+++ b/package.json
@@ -1,6 +1,6 @@
 {
   "name": "healthlog",
-  "version": "1.32.26",
+  "version": "1.32.27",
   "description": "Self-hosted personal-health-tracking PWA with Withings integration, AI insights, and doctor-report PDF export.",
   "license": "PolyForm-Noncommercial-1.0.0",
   "homepage": "https://healthlog.dev",
diff --git a/public/sw.js b/public/sw.js
index b965a2c19..f7112ce6e 100644
--- a/public/sw.js
+++ b/public/sw.js
@@ -36,7 +36,7 @@ try {
 // v1.4.38.4 → v1.4.42. Do not hand-edit; bump `package.json` and rebuild.
 const CACHE_VERSION =
   (typeof self !== "undefined" && self.__APP_VERSION__) ||
-  /* @sw-version-fallback */ "v1.32.26";
+  /* @sw-version-fallback */ "v1.32.27";
 const STATIC_CACHE = `healthlog-static-${CACHE_VERSION}`;
 const PAGE_CACHE = `healthlog-pages-${CACHE_VERSION}`;
 // v1.18.6 — read-only data cache for a curated allowlist of safe GET `/api/*`
diff --git a/src/__tests__/unit-preference-display-guard.test.ts b/src/__tests__/unit-preference-display-guard.test.ts
index ff91da3c0..0a7c638ec 100644
--- a/src/__tests__/unit-preference-display-guard.test.ts
+++ b/src/__tests__/unit-preference-display-guard.test.ts
@@ -31,13 +31,32 @@ const TRANSFORMED_UNITS: ReadonlySet<string> = new Set(
   ]),
 );
 
-/** Swept surfaces: the dashboard client + every insights sub-page. */
+/**
+ * v1.32.27 — the target/threshold subsystem. These three files are the
+ * coupled display+edit unit: the reference panel that RENDERS a target
+ * band, the sheet that EDITS it, and the settings editor that edits the
+ * same thresholds from the other end. A partial wire here is worse than
+ * none — a converted display over a canonical save silently rewrites
+ * the user's stored target — so they are swept for hardcoded units AND
+ * asserted to route through the preference hook.
+ */
+const TARGET_SURFACES = [
+  join(SRC, "components", "insights", "metric-target-summary.tsx"),
+  join(SRC, "components", "targets", "target-edit-sheet.tsx"),
+  join(SRC, "components", "settings", "thresholds-editor-section.tsx"),
+];
+
+/**
+ * Swept surfaces: the dashboard client, every insights sub-page, and the
+ * target/threshold surfaces.
+ */
 function sweptFiles(): string[] {
   return [
     join(SRC, "app", "page-client.tsx"),
     ...globSync("app/insights/**/page.tsx", { cwd: SRC }).map((rel) =>
       join(SRC, rel),
     ),
+    ...TARGET_SURFACES,
   ];
 }
 
@@ -74,6 +93,37 @@ describe("unit-preference display guard", () => {
     expect(offenders).toEqual([]);
   });
 
+  it("every target/threshold surface resolves its unit from the preference", () => {
+    // The tripwire for a silent un-wire: delete the hook import from any
+    // of the three and the surface falls back to canonical kilograms
+    // while its sibling still shows pounds.
+    // The call site, not the import — swapping the hook out for a
+    // hardcoded "metric" literal while leaving the import behind is
+    // exactly the un-wire this has to catch.
+    const offenders = TARGET_SURFACES.filter(
+      (file) => !readFileSync(file, "utf8").includes("useUnitDisplay()"),
+    );
+    expect(offenders).toEqual([]);
+  });
+
+  it("every target/threshold surface converts through the shared adapter", () => {
+    // One adapter owns seed, guardrail, save, and unit label for all
+    // three surfaces. A surface that hand-rolls its own conversion (or
+    // announces `METRIC_BOUNDS[metric].unit`, the canonical symbol)
+    // is how the display and the edit halves drift apart.
+    const offenders: string[] = [];
+    for (const file of TARGET_SURFACES) {
+      const src = readFileSync(file, "utf8");
+      if (!src.includes("resolveTargetUnitAdapter")) {
+        offenders.push(`${file}: no adapter`);
+      }
+      if (/METRIC_BOUNDS\[[^\]]+\]\.unit/.test(src)) {
+        offenders.push(`${file}: canonical bound unit rendered`);
+      }
+    }
+    expect(offenders).toEqual([]);
+  });
+
   it("every transformed type carries both a metric and an imperial branch", () => {
     for (const type of TRANSFORMED_TYPES) {
       const metric = getDisplayTransform(type, "metric");
diff --git a/src/components/insights/__tests__/metric-target-summary-unit-preference.test.tsx b/src/components/insights/__tests__/metric-target-summary-unit-preference.test.tsx
new file mode 100644
index 000000000..91d0a0c75
--- /dev/null
+++ b/src/components/insights/__tests__/metric-target-summary-unit-preference.test.tsx
@@ -0,0 +1,89 @@
+import { describe, it, expect, vi } from "vitest";
+import { renderToStaticMarkup } from "react-dom/server";
+
+import { I18nProvider } from "@/lib/i18n/context";
+
+/**
+ * v1.32.27 — the target reference panel follows the metric/imperial
+ * preference.
+ *
+ * `/api/insights/targets` stays canonical (kg for weight); the panel
+ * converts once and hands the converted pair to the range bar, the
+ * status pill, and the edit sheet's seed. These assertions read the
+ * range bar's axis labels out of the SSR markup — the one place the
+ * band endpoints and their unit are rendered as plain text rather than
+ * inside a portalled tooltip.
+ */
+
+const authUser = vi.hoisted(() => ({
+  value: null as { unitPreference?: string } | null,
+}));
+
+vi.mock("@/hooks/use-auth", () => ({
+  useAuth: vi.fn(() => ({ isAuthenticated: true, user: authUser.value })),
+}));
+
+const useQueryMock = vi.fn();
+vi.mock("@tanstack/react-query", () => ({
+  useQuery: (opts: unknown) => useQueryMock(opts),
+  useMutation: () => ({ mutate: vi.fn(), isPending: false }),
+  useQueryClient: () => ({ invalidateQueries: vi.fn() }),
+}));
+
+const { MetricTargetSummary } = await import("../metric-target-summary");
+
+/** A weight target as the route emits it: canonical kilograms. */
+const weightPayload = {
+  targets: [
+    {
+      type: "WEIGHT",
+      label: "Weight",
+      current: 72.5,
+      average30: 73.1,
+      unit: "kg",
+      range: { min: 60, max: 80 },
+      classification: { category: "Normal", color: "green" },
+      source: "WHO",
+      daysInRange7d: 5,
+      daysLogged7d: 7,
+      daysInRange30d: 20,
+      daysLogged30d: 30,
+      insufficientData: false,
+      consistency7d: ["in", "in", "out", "in", "in", "near", "in"] as const,
+    },
+  ],
+  bpDiastolic: { current: null, average30: null, range: null },
+};
+
+function renderWeightPanel(unitPreference: string | null): string {
+  authUser.value = unitPreference ? { unitPreference } : null;
+  useQueryMock.mockReturnValue({ data: weightPayload });
+  return renderToStaticMarkup(
+    <I18nProvider initialLocale="en">
+      <MetricTargetSummary slug="weight" />
+    </I18nProvider>,
+  );
+}
+
+describe("<MetricTargetSummary> under a unit preference", () => {
+  it("renders the weight band in pounds for an imperial account", () => {
+    const html = renderWeightPanel("imperial");
+    // 60 kg → 132.3 lb, 80 kg → 176.4 lb.
+    expect(html).toContain("132.3 lb");
+    expect(html).toContain("176.4 lb");
+    expect(html).not.toContain("60 kg");
+    expect(html).not.toContain("80 kg");
+  });
+
+  it("leaves the weight band in kilograms for a metric account", () => {
+    const html = renderWeightPanel("metric");
+    expect(html).toContain("60 kg");
+    expect(html).toContain("80 kg");
+    expect(html).not.toContain("lb");
+  });
+
+  it("treats a payload with no preference as metric", () => {
+    // A stale `/api/auth/me` payload must never silently rescale a band.
+    expect(renderWeightPanel(null)).toBe(renderWeightPanel("metric"));
+  });
+});
diff --git a/src/components/insights/metric-target-summary.tsx b/src/components/insights/metric-target-summary.tsx
index aec8c9079..2718c3b1b 100644
--- a/src/components/insights/metric-target-summary.tsx
+++ b/src/components/insights/metric-target-summary.tsx
@@ -5,9 +5,11 @@ import { useQuery } from "@tanstack/react-query";
 import { ExternalLink, Target } from "lucide-react";
 
 import { useAuth } from "@/hooks/use-auth";
+import { useUnitDisplay } from "@/hooks/use-unit-display";
 import { queryKeys } from "@/lib/query-keys";
 import { useTranslations } from "@/lib/i18n/context";
 import { convertGlucose, resolveGlucoseUnit } from "@/lib/glucose";
+import { resolveTargetUnitAdapter } from "@/lib/targets/target-unit-display";
 import { Card, CardContent, CardHeader } from "@/components/ui/card";
 import { RangeBar } from "@/components/targets/range-bar";
 import { ConsistencyStrip } from "@/components/targets/consistency-strip";
@@ -229,8 +231,29 @@ function TargetReferencePanel({
 }: TargetReferencePanelProps) {
   const { t } = useTranslations();
   const adjust = useTargetAdjust();
+  const { preference } = useUnitDisplay();
 
-  const { range, unit } = target;
+  // v1.32.27 — the panel renders in the user's preferred unit. The
+  // `/api/insights/targets` payload is canonical (kg for weight); the
+  // adapter converts it once, here, and everything downstream — the
+  // range bar, the status pill, the 30-day average, and the edit
+  // sheet's seed — consumes the converted pair. Glucose contexts are
+  // pre-converted by the caller above and carry no display transform,
+  // so they take the adapter's identity path and are never scaled
+  // twice. For a metric account the adapter is the exact identity, so
+  // this panel is byte-identical to the previous release.
+  const units = resolveTargetUnitAdapter(target.type, target.unit, preference);
+  const unit = units.unit;
+  const range = target.range
+    ? {
+        min: units.toDisplay(target.range.min),
+        max: units.toDisplay(target.range.max),
+      }
+    : null;
+  const currentValue =
+    target.current == null ? null : units.toDisplay(target.current);
+  const average30 =
+    target.average30 == null ? null : units.toDisplay(target.average30);
 
   // Register this metric as the header gear's edit target. The effect
   // re-runs when the seeded range / unit / label changes (e.g. a glucose
@@ -282,11 +305,11 @@ function TargetReferencePanel({
   // the exception: it has no `<MetricPrimaryTile>` (this richer panel IS
   // its primary tile), so it keeps the stitched S/D 30-day average inline.
   let averageLabel: string | null = null;
-  if (isBp && target.average30 != null) {
+  if (isBp && average30 != null) {
     const avgValue =
       bpDiastolic?.average30 != null
-        ? `${Math.round(target.average30)}/${Math.round(bpDiastolic.average30)}`
-        : String(Math.round(target.average30 * 10) / 10);
+        ? `${Math.round(average30)}/${Math.round(bpDiastolic.average30)}`
+        : String(Math.round(average30 * 10) / 10);
     averageLabel = `${t("targets.average30d")} ${avgValue} ${unit}`;
   }
 
@@ -338,9 +361,9 @@ function TargetReferencePanel({
       </CardHeader>
       <CardContent className="space-y-3">
         {/* Row 2: range bar — where today's value sits inside the band. */}
-        {target.current != null ? (
+        {currentValue != null ? (
           <RangeBar
-            value={target.current}
+            value={currentValue}
             min={range.min}
             max={range.max}
             unit={unit}
diff --git a/src/components/settings/thresholds-editor-section.tsx b/src/components/settings/thresholds-editor-section.tsx
index 2cb89e1ba..a0cdde8be 100644
--- a/src/components/settings/thresholds-editor-section.tsx
+++ b/src/components/settings/thresholds-editor-section.tsx
@@ -19,6 +19,8 @@ import {
   type EffectiveRange,
 } from "@/lib/analytics/effective-range";
 import { apiFetchRaw, apiGet } from "@/lib/api/api-fetch";
+import { useUnitDisplay } from "@/hooks/use-unit-display";
+import { resolveTargetUnitAdapter } from "@/lib/targets/target-unit-display";
 import { SettingsCard } from "@/components/settings/settings-card";
 
 interface ThresholdsApiResponse {
@@ -215,14 +217,35 @@ function MetricRow({
 }: MetricRowProps) {
   const { t } = useTranslations();
   const fmt = useFormatters();
-  const bounds = METRIC_BOUNDS[metric];
+  const { preference } = useUnitDisplay();
+  const canonicalBounds = METRIC_BOUNDS[metric];
+
+  // v1.32.27 — the row reads and writes in the user's preferred unit
+  // while `User.thresholdsJson` stays canonical SI. Everything the row
+  // receives (`override`, `effective.default`, `METRIC_BOUNDS`) is
+  // canonical, so it converts on the way into the fields and inverts on
+  // the way back out in `onSave`. Guardrails round inward so a value
+  // typed at the displayed limit still passes the server's canonical
+  // check. Metrics without a transform — and every metric for a metric
+  // user — take the adapter's identity path untouched.
+  const units = resolveTargetUnitAdapter(
+    metric,
+    canonicalBounds.unit,
+    preference,
+  );
+  const bounds = { ...units.bounds(canonicalBounds), unit: units.unit };
+
+  /** Canonical seed → the string the field shows, falling back to the bound. */
+  const seedString = (canonical: number | undefined, fallback: number) =>
+    String(canonical == null ? fallback : units.toDisplay(canonical));
+
   const hasOverride = override !== null;
   const [overrideMode, setOverrideMode] = useState(hasOverride);
   const [minStr, setMinStr] = useState(
-    String(override?.min ?? effective?.default?.greenMin ?? bounds.min),
+    seedString(override?.min ?? effective?.default?.greenMin, bounds.min),
   );
   const [maxStr, setMaxStr] = useState(
-    String(override?.max ?? effective?.default?.greenMax ?? bounds.max),
+    seedString(override?.max ?? effective?.default?.greenMax, bounds.max),
   );
 
   // v1.30.1 M9 — the row is keyed on the stable `metric`, so a per-row
@@ -244,10 +267,10 @@ function MetricRow({
     setSyncedIdentity(overrideIdentity);
     setOverrideMode(hasOverride);
     setMinStr(
-      String(override?.min ?? effective?.default?.greenMin ?? bounds.min),
+      seedString(override?.min ?? effective?.default?.greenMin, bounds.min),
     );
     setMaxStr(
-      String(override?.max ?? effective?.default?.greenMax ?? bounds.max),
+      seedString(override?.max ?? effective?.default?.greenMax, bounds.max),
     );
   }
 
@@ -269,7 +292,7 @@ function MetricRow({
           <p className="text-sm font-medium">{t(METRIC_LABEL_KEYS[metric])}</p>
           <p className="text-muted-foreground text-xs">
             {defaultRange
-              ? `${t("thresholds.defaultLabel")}: ${fmt.number(defaultRange.greenMin, 1)}–${fmt.number(defaultRange.greenMax, 1)} ${bounds.unit}`
+              ? `${t("thresholds.defaultLabel")}: ${fmt.number(units.toDisplay(defaultRange.greenMin), 1)}–${fmt.number(units.toDisplay(defaultRange.greenMax), 1)} ${bounds.unit}`
               : t("thresholds.unsetExplanation")}
           </p>
         </div>
@@ -316,7 +339,7 @@ function MetricRow({
                 type="number"
                 inputMode={metric === "ACTIVITY_STEPS" ? "numeric" : "decimal"}
                 enterKeyHint="next"
-                step={metric === "ACTIVITY_STEPS" ? 100 : 0.1}
+                step={units.step}
                 min={bounds.min}
                 max={bounds.max}
                 value={minStr}
@@ -334,7 +357,7 @@ function MetricRow({
                 type="number"
                 inputMode={metric === "ACTIVITY_STEPS" ? "numeric" : "decimal"}
                 enterKeyHint="done"
-                step={metric === "ACTIVITY_STEPS" ? 100 : 0.1}
+                step={units.step}
                 min={bounds.min}
                 max={bounds.max}
                 value={maxStr}
@@ -344,7 +367,13 @@ function MetricRow({
             </div>
             <div className="flex items-end gap-2">
               <Button
-                onClick={() => valid && onSave({ min: minNum, max: maxNum })}
+                onClick={() =>
+                  valid &&
+                  onSave({
+                    min: units.toCanonical(minNum),
+                    max: units.toCanonical(maxNum),
+                  })
+                }
                 disabled={busy || !valid}
                 size="sm"
                 className="min-h-11 sm:min-h-9"
diff --git a/src/components/targets/__tests__/target-edit-sheet.test.tsx b/src/components/targets/__tests__/target-edit-sheet.test.tsx
index 115c8ba2c..3a6f72606 100644
--- a/src/components/targets/__tests__/target-edit-sheet.test.tsx
+++ b/src/components/targets/__tests__/target-edit-sheet.test.tsx
@@ -116,6 +116,29 @@ describe("<TargetEditSheet>", () => {
     ).not.toThrow();
   });
 
+  it("mounts a weight target seeded in pounds without throwing", () => {
+    // v1.32.27 — an imperial account gets `unit="lb"` and a
+    // pound-converted seed from the panel; the sheet projects the
+    // kilogram guardrails into the same unit and inverts on save. The
+    // arithmetic itself is pinned in `target-unit-display.test.ts`
+    // (Radix portals the body, so SSR cannot read the fields back);
+    // this covers the mount path composing cleanly.
+    expect(() =>
+      renderToStaticMarkup(
+        withProviders(
+          <TargetEditSheet
+            targetType="WEIGHT"
+            targetLabel="Weight"
+            unit="lb"
+            initialRange={{ min: 132.3, max: 176.4 }}
+            open={true}
+            onOpenChange={vi.fn()}
+          />,
+        ),
+      ),
+    ).not.toThrow();
+  });
+
   it("mounts the body without throwing for a derived metric (BMI)", () => {
     // BMI is derived from weight + height — the body shows the
     // explanatory hint instead of the editable inputs.
diff --git a/src/components/targets/target-edit-sheet.tsx b/src/components/targets/target-edit-sheet.tsx
index 9edd6110a..ad0342bec 100644
--- a/src/components/targets/target-edit-sheet.tsx
+++ b/src/components/targets/target-edit-sheet.tsx
@@ -17,6 +17,8 @@ import {
   type EffectiveRange,
 } from "@/lib/analytics/effective-range";
 import { convertGlucose, toCanonicalMgdl } from "@/lib/glucose";
+import { resolveTargetUnitAdapter } from "@/lib/targets/target-unit-display";
+import { useUnitDisplay } from "@/hooks/use-unit-display";
 import { apiDelete, apiGet, apiPut } from "@/lib/api/api-fetch";
 
 /**
@@ -133,10 +135,38 @@ function TargetEditSheetBody({
   // is rejected by the 40–400 mg/dL bounds or stored verbatim as 5.5.
   const isGlucoseMmol =
     metric != null && metric.startsWith("BLOOD_GLUCOSE") && unit === "mmol/L";
-  const toDisplay = (mgdl: number) =>
-    isGlucoseMmol ? convertGlucose(mgdl, "mmol/L") : mgdl;
+
+  // v1.32.27 — the same coupled treatment now covers the metric/imperial
+  // preference. Weight-class thresholds are stored in kg; an imperial
+  // user seeds, validates, and types in lb, and the adapter inverts the
+  // typed number back to kg before the PUT. Glucose keeps its own
+  // mg/dL ↔ mmol/L dialect (it carries no display transform, so the two
+  // never compose); every other metric takes the adapter's identity
+  // path and is numerically untouched.
+  const { preference } = useUnitDisplay();
+  const units = resolveTargetUnitAdapter(
+    isBp ? "BLOOD_PRESSURE_SYS" : (metric ?? ""),
+    unit,
+    preference,
+  );
+
+  const toDisplay = (canonical: number) =>
+    isGlucoseMmol
+      ? convertGlucose(canonical, "mmol/L")
+      : units.toDisplay(canonical);
   const toCanonical = (displayValue: number) =>
-    isGlucoseMmol ? toCanonicalMgdl(displayValue, "mmol/L") : displayValue;
+    isGlucoseMmol
+      ? toCanonicalMgdl(displayValue, "mmol/L")
+      : units.toCanonical(displayValue);
+  // Guardrails the typed value is checked against, expressed in the
+  // display unit. Glucose projects its mg/dL window through the same
+  // conversion the fields use; every other metric rounds the window
+  // INWARD so a value typed at the display bound never inverts to a
+  // canonical value the server rejects.
+  const toDisplayBounds = (canonical: { min: number; max: number }) =>
+    isGlucoseMmol
+      ? { min: toDisplay(canonical.min), max: toDisplay(canonical.max) }
+      : units.bounds(canonical);
 
   // Lazy-load the thresholds payload so the dialog also catches any
   // already-persisted override even when the seeded `initialRange`
@@ -166,10 +196,7 @@ function TargetEditSheetBody({
       return { min: toDisplay(override.min), max: toDisplay(override.max) };
     }
     if (fallback) return fallback;
-    if (m) {
-      const bounds = METRIC_BOUNDS[m];
-      return { min: toDisplay(bounds.min), max: toDisplay(bounds.max) };
-    }
+    if (m) return toDisplayBounds(METRIC_BOUNDS[m]);
     return { min: 0, max: 100 };
   };
 
@@ -281,11 +308,7 @@ function TargetEditSheetBody({
   // display unit so a mmol/L glucose entry is checked against the
   // mmol/L-projected 40–400 mg/dL window, not the raw mg/dL numbers.
   const primaryBounds = canonicalPrimaryBounds
-    ? {
-        min: toDisplay(canonicalPrimaryBounds.min),
-        max: toDisplay(canonicalPrimaryBounds.max),
-        unit,
-      }
+    ? { ...toDisplayBounds(canonicalPrimaryBounds), unit }
     : null;
 
   const primaryValid =
@@ -466,7 +489,7 @@ function TargetEditSheetBody({
                   id="target-edit-min"
                   ref={firstInputRef}
                   type="number"
-                  step={targetType === "ACTIVITY_STEPS" ? 100 : 0.1}
+                  step={units.step}
                   min={primaryBounds.min}
                   max={primaryBounds.max}
                   value={displayMin}
@@ -485,7 +508,7 @@ function TargetEditSheetBody({
                 <Input
                   id="target-edit-max"
                   type="number"
-                  step={targetType === "ACTIVITY_STEPS" ? 100 : 0.1}
+                  step={units.step}
                   min={primaryBounds.min}
                   max={primaryBounds.max}
                   value={displayMax}
diff --git a/src/lib/targets/__tests__/target-unit-display.test.ts b/src/lib/targets/__tests__/target-unit-display.test.ts
new file mode 100644
index 000000000..da8702179
--- /dev/null
+++ b/src/lib/targets/__tests__/target-unit-display.test.ts
@@ -0,0 +1,226 @@
+import { describe, it, expect } from "vitest";
+
+import { METRIC_BOUNDS } from "@/lib/analytics/effective-range";
+import { resolveTargetUnitAdapter } from "../target-unit-display";
+
+/**
+ * v1.32.27 — the target/threshold unit adapter.
+ *
+ * The dangerous failure mode this subsystem exists to avoid is a HALF
+ * wire: display converted, edit seed or save left canonical, so the
+ * user's typed number silently changes meaning between save and reopen.
+ * These assertions pin the whole loop — seed, guardrail, save, reopen —
+ * for the weight class (a pure scale) and for temperature (the affine
+ * one, where an offset leaking into a delta is the classic bug).
+ */
+
+const KG_PER_LB = 0.45359237;
+
+describe("resolveTargetUnitAdapter — metric account (identity)", () => {
+  it("leaves a weight threshold bit-for-bit untouched", () => {
+    const units = resolveTargetUnitAdapter("WEIGHT", "kg", "metric");
+    expect(units.rescales).toBe(false);
+    expect(units.unit).toBe("kg");
+    // Not "close to" — exactly the same double, in both directions.
+    for (const value of [30, 68.04, 72.5, 300, 88.123456789]) {
+      expect(units.toDisplay(value)).toBe(value);
+      expect(units.toCanonical(value)).toBe(value);
+      expect(units.toDisplayDelta(value)).toBe(value);
+    }
+    expect(units.bounds(METRIC_BOUNDS.WEIGHT)).toEqual({ min: 30, max: 300 });
+    expect(units.step).toBe(0.1);
+  });
+
+  it("leaves an untransformed metric alone under either preference", () => {
+    for (const preference of ["metric", "imperial"] as const) {
+      const units = resolveTargetUnitAdapter(
+        "BLOOD_PRESSURE_SYS",
+        "mmHg",
+        preference,
+      );
+      expect(units.rescales).toBe(false);
+      expect(units.unit).toBe("mmHg");
+      expect(units.toDisplay(118)).toBe(118);
+      expect(units.toCanonical(118)).toBe(118);
+      expect(units.bounds(METRIC_BOUNDS.BLOOD_PRESSURE_SYS)).toEqual({
+        min: 80,
+        max: 220,
+      });
+    }
+  });
+
+  it("is inert for the keys the edit sheet passes on its non-metric paths", () => {
+    // A derived card (BMI, mood, medication compliance) has no editable
+    // threshold and the sheet resolves the adapter with an empty key;
+    // glucose keeps its own mg/dL ↔ mmol/L dialect and must never pick
+    // up a second conversion on top.
+    for (const key of ["", "BMI", "BLOOD_GLUCOSE_FASTING"]) {
+      const units = resolveTargetUnitAdapter(key, "mmol/L", "imperial");
+      expect(units.rescales).toBe(false);
+      expect(units.unit).toBe("mmol/L");
+      expect(units.toDisplay(5.5)).toBe(5.5);
+      expect(units.toCanonical(5.5)).toBe(5.5);
+    }
+  });
+
+  it("keeps the whole-hundred step for a step-count target", () => {
+    for (const preference of ["metric", "imperial"] as const) {
+      expect(
+        resolveTargetUnitAdapter("ACTIVITY_STEPS", "steps", preference).step,
+      ).toBe(100);
+    }
+  });
+});
+
+describe("resolveTargetUnitAdapter — imperial weight class", () => {
+  const units = resolveTargetUnitAdapter("WEIGHT", "kg", "imperial");
+
+  it("announces pounds and a one-decimal step", () => {
+    expect(units.rescales).toBe(true);
+    expect(units.unit).toBe("lb");
+    expect(units.step).toBe(0.1);
+  });
+
+  it("seeds a stored kilogram threshold into pounds", () => {
+    // 68.04 kg is what 150 lb persists as; it must read back as 150.
+    expect(units.toDisplay(68.04)).toBe(150);
+    expect(units.toDisplay(80)).toBe(176.4);
+  });
+
+  it("saves a typed pound value back as canonical kilograms", () => {
+    expect(units.toCanonical(150)).toBe(68.04);
+    // 80 kg renders as 176.4 lb; typing 176.4 back lands on 80.01 kg,
+    // one hundredth off — the unavoidable cost of a one-decimal pound
+    // field. What must NOT drift is the number the user typed, which
+    // the round-trip sweep below pins.
+    expect(units.toCanonical(176.4)).toBe(80.01);
+  });
+
+  it("round-trips every typed value it can render (save → reopen)", () => {
+    // The property that matters: type a number, save, reopen, see the
+    // same number. Swept across the whole editable window at the
+    // input's own step granularity.
+    for (let typed = 70; typed <= 660; typed += 0.1) {
+      const shown = Math.round(typed * 10) / 10;
+      const canonical = units.toCanonical(shown);
+      expect(units.toDisplay(canonical)).toBe(shown);
+    }
+  });
+
+  it("rounds guardrails inward so a value typed at the limit still saves", () => {
+    const bounds = units.bounds(METRIC_BOUNDS.WEIGHT);
+    // A naive round of the 30 kg floor gives 66.1 lb, which inverts to
+    // 29.98 kg and the server rejects it. The ceiling keeps it legal.
+    expect(bounds.min).toBe(66.2);
+    expect(bounds.max).toBe(661.3);
+    expect(units.toCanonical(bounds.min)).toBeGreaterThanOrEqual(
+      METRIC_BOUNDS.WEIGHT.min,
+    );
+    expect(units.toCanonical(bounds.max)).toBeLessThanOrEqual(
+      METRIC_BOUNDS.WEIGHT.max,
+    );
+  });
+
+  it("accepts an imperial-valid value a kilogram bound would have rejected", () => {
+    const bounds = units.bounds(METRIC_BOUNDS.WEIGHT);
+    // 150 lb sails past the raw canonical 30–300 check as a NUMBER only
+    // because the window is now expressed in pounds. Against the
+    // unconverted kilogram window a 400 lb target would have been read
+    // as "400 > 300, rejected" while it is a legitimate 181.44 kg.
+    for (const typed of [150, 400, 660]) {
+      expect(typed).toBeGreaterThanOrEqual(bounds.min);
+      expect(typed).toBeLessThanOrEqual(bounds.max);
+      const canonical = units.toCanonical(typed);
+      expect(canonical).toBeGreaterThanOrEqual(METRIC_BOUNDS.WEIGHT.min);
+      expect(canonical).toBeLessThanOrEqual(METRIC_BOUNDS.WEIGHT.max);
+    }
+  });
+
+  it("still rejects a genuinely out-of-range value", () => {
+    const bounds = units.bounds(METRIC_BOUNDS.WEIGHT);
+    for (const typed of [12, 66.1, 661.4, 900]) {
+      expect(typed < bounds.min || typed > bounds.max).toBe(true);
+    }
+  });
+
+  it("carries the same treatment across the whole weight class", () => {
+    for (const metric of ["TOTAL_BODY_WATER", "BONE_MASS"] as const) {
+      const adapter = resolveTargetUnitAdapter(metric, "kg", "imperial");
+      expect(adapter.unit).toBe("lb");
+      const bounds = adapter.bounds(METRIC_BOUNDS[metric]);
+      expect(adapter.toCanonical(bounds.min)).toBeGreaterThanOrEqual(
+        METRIC_BOUNDS[metric].min,
+      );
+      expect(adapter.toCanonical(bounds.max)).toBeLessThanOrEqual(
+        METRIC_BOUNDS[metric].max,
+      );
+    }
+  });
+
+  it("matches the exact pound definition, not an approximation", () => {
+    expect(units.toCanonical(100)).toBe(
+      Math.round(100 * KG_PER_LB * 100) / 100,
+    );
+  });
+});
+
+describe("resolveTargetUnitAdapter — temperature (the affine one)", () => {
+  const units = resolveTargetUnitAdapter(
+    "BODY_TEMPERATURE",
+    "celsius",
+    "imperial",
+  );
+
+  it("shifts absolute readings but never a difference", () => {
+    expect(units.unit).toBe("°F");
+    expect(units.toDisplay(37)).toBe(98.6);
+    expect(units.toDisplay(38)).toBe(100.4);
+    // A one-degree-Celsius spread is a 1.8-degree-Fahrenheit spread. If
+    // the delta ever picked up the +32 absolute shift it would read
+    // 33.8 — the exact bug `applyDisplayTransformDelta` exists to stop.
+    expect(units.toDisplayDelta(1)).toBe(1.8);
+    expect(units.toDisplayDelta(1)).not.toBe(33.8);
+  });
+
+  it("keeps a rendered difference offset-free by construction", () => {
+    // The range bar computes its "x above target" sentence from two
+    // already-converted absolutes. That subtraction must agree with the
+    // factor-only delta conversion, or the two would disagree by 32.
+    for (const [a, b] of [
+      [38, 37],
+      [37.4, 36.6],
+      [41, 35],
+    ]) {
+      const difference = units.toDisplay(a) - units.toDisplay(b);
+      expect(difference).toBeCloseTo(units.toDisplayDelta(a - b), 6);
+    }
+  });
+
+  it("round-trips a typed Fahrenheit target back to itself", () => {
+    for (let typed = 95; typed <= 106; typed += 0.1) {
+      const shown = Math.round(typed * 10) / 10;
+      expect(units.toDisplay(units.toCanonical(shown))).toBe(shown);
+    }
+  });
+
+  it("is the exact identity for a metric account", () => {
+    const metricUnits = resolveTargetUnitAdapter(
+      "BODY_TEMPERATURE",
+      "celsius",
+      "metric",
+    );
+    expect(metricUnits.rescales).toBe(false);
+    expect(metricUnits.toDisplay(37)).toBe(37);
+    expect(metricUnits.toCanonical(37)).toBe(37);
+    expect(metricUnits.toDisplayDelta(1)).toBe(1);
+  });
+
+  it("rounds an affine guardrail inward on both ends", () => {
+    const bounds = units.bounds({ min: 30, max: 45 });
+    // 30 °C = 86 °F and 45 °C = 113 °F exactly; inward rounding must not
+    // drift a clean bound off its own value.
+    expect(bounds).toEqual({ min: 86, max: 113 });
+    expect(units.toCanonical(bounds.min)).toBeGreaterThanOrEqual(30);
+    expect(units.toCanonical(bounds.max)).toBeLessThanOrEqual(45);
+  });
+});
diff --git a/src/lib/targets/target-unit-display.ts b/src/lib/targets/target-unit-display.ts
new file mode 100644
index 000000000..ae3b2e4e5
--- /dev/null
+++ b/src/lib/targets/target-unit-display.ts
@@ -0,0 +1,162 @@
+/**
+ * v1.32.27 — the target/threshold subsystem's unit adapter.
+ *
+ * v1.32.26 wired the metric/imperial preference across every READING
+ * surface but deliberately left target ranges canonical: a target panel
+ * is a coupled display+edit unit, and converting only the display half
+ * would corrupt the edit seed and the save round-trip. This module is
+ * the missing half — one adapter that owns every direction of the
+ * conversion so the three target surfaces (the Insights reference
+ * panel, the per-metric edit sheet, the settings threshold editor)
+ * cannot drift apart.
+ *
+ * Storage never changes. `User.thresholdsJson`, `METRIC_BOUNDS`, the
+ * `/api/user/thresholds` wire contract, the effective-range resolver,
+ * the doctor report, and the AI snapshot all stay canonical SI. The
+ * adapter converts at the render boundary and inverts at the entry
+ * boundary, exactly like `measurement-form.tsx` does for a raw reading.
+ *
+ * The four rules that make the round-trip safe:
+ *
+ *   1. `toDisplay` rounds to the transform's `decimals`, so the field
+ *      shows "150" and not "150.00000000000003".
+ *   2. `toCanonical` rounds the inverted value to 2 decimals — the same
+ *      dialect the measurement entry form uses — so 150 lb persists as
+ *      68.04 kg, not 68.03885550000001.
+ *   3. Rules 1 + 2 compose back to the typed number: 150 lb → 68.04 kg
+ *      → 150 lb. Save-then-reopen is stable.
+ *   4. Guardrails round INWARD (min up, max down). A naive round of the
+ *      30 kg floor gives 66.1 lb, which inverts to 29.98 kg and the
+ *      server rejects it. Ceiling it to 66.2 lb inverts to 30.03 kg and
+ *      passes.
+ *
+ * For a metric user every transformed type resolves to factor 1 /
+ * offset 0, `rescales` is false, and all four helpers return their
+ * argument untouched — no rounding, no re-derivation. A metric
+ * account's stored thresholds are therefore bit-for-bit unchanged by
+ * this release.
+ */
+import {
+  applyDisplayTransform,
+  applyDisplayTransformDelta,
+  getDisplayTransform,
+  hasDisplayTransform,
+  invertDisplayTransform,
+  type UnitPreference,
+} from "@/lib/measurements/display-transform";
+
+/** Canonical decimals a converted threshold value persists with. */
+const CANONICAL_DECIMALS = 2;
+
+/** Numeric `step` for a step-counting target — whole hundreds, not 0.1. */
+const STEP_COUNT_INPUT_STEP = 100;
+
+/** Fallback input step for a metric with no registered transform. */
+const DEFAULT_INPUT_STEP = 0.1;
+
+export interface TargetUnitAdapter {
+  /** Unit symbol every label, hint, and tooltip on the surface announces. */
+  unit: string;
+  /** `step` for a display-unit numeric input on this metric. */
+  step: number;
+  /**
+   * True when the adapter actually rescales the number (the imperial
+   * branch of a transformed type). False for a metric user and for
+   * every untransformed metric, in which case every helper below is the
+   * exact identity.
+   */
+  rescales: boolean;
+  /** Canonical stored value → the number the surface renders. */
+  toDisplay(canonical: number): number;
+  /** Typed display number → the canonical value that gets persisted. */
+  toCanonical(display: number): number;
+  /**
+   * Canonical DELTA / band width / spread → display. Factor only, never
+   * the affine offset: a 1 °C spread is a 1.8 °F spread, not 33.8 °F.
+   */
+  toDisplayDelta(canonicalDelta: number): number;
+  /**
+   * Canonical guardrail pair → the display window a typed value is
+   * validated against, rounded inward so the inverted value never falls
+   * outside the canonical guardrail the server enforces.
+   */
+  bounds(canonical: { min: number; max: number }): {
+    min: number;
+    max: number;
+  };
+}
+
+function roundTo(value: number, decimals: number): number {
+  const scale = 10 ** decimals;
+  return Math.round(value * scale) / scale;
+}
+
+function ceilTo(value: number, decimals: number): number {
+  const scale = 10 ** decimals;
+  return Math.ceil(value * scale) / scale;
+}
+
+function floorTo(value: number, decimals: number): number {
+  const scale = 10 ** decimals;
+  return Math.floor(value * scale) / scale;
+}
+
+/** The pass-through adapter: canonical unit, no arithmetic at all. */
+function identityAdapter(metric: string, unit: string): TargetUnitAdapter {
+  return {
+    unit,
+    step:
+      metric === "ACTIVITY_STEPS" ? STEP_COUNT_INPUT_STEP : DEFAULT_INPUT_STEP,
+    rescales: false,
+    toDisplay: (canonical) => canonical,
+    toCanonical: (display) => display,
+    toDisplayDelta: (canonicalDelta) => canonicalDelta,
+    bounds: (canonical) => ({ min: canonical.min, max: canonical.max }),
+  };
+}
+
+/**
+ * Resolve the unit adapter for one threshold metric / target-card type.
+ *
+ * `metric` is the threshold-metric literal (`"WEIGHT"`,
+ * `"BLOOD_PRESSURE_SYS"`, …); for the transformed set those literals are
+ * the measurement-type literals the display-transform registry is keyed
+ * on, so a metric participates exactly when it has a registered
+ * transform. `canonicalUnit` is the unit the surface announced before
+ * this release (`METRIC_BOUNDS[metric].unit` or the targets payload's
+ * `unit`) and is what an untransformed metric keeps.
+ */
+export function resolveTargetUnitAdapter(
+  metric: string,
+  canonicalUnit: string,
+  preference: UnitPreference,
+): TargetUnitAdapter {
+  if (!hasDisplayTransform(metric))
+    return identityAdapter(metric, canonicalUnit);
+
+  const transform = getDisplayTransform(metric, preference);
+  const rescales = transform.factor !== 1 || (transform.offset ?? 0) !== 0;
+
+  // A transformed type on the metric branch keeps the transform's
+  // DISPLAY symbol (which is the canonical symbol for every threshold
+  // metric in the registry today) but no arithmetic — the identity
+  // adapter guarantees the stored value is untouched.
+  if (!rescales) return identityAdapter(metric, transform.displayUnit);
+
+  const { decimals } = transform;
+  return {
+    unit: transform.displayUnit,
+    step: metric === "ACTIVITY_STEPS" ? STEP_COUNT_INPUT_STEP : 10 ** -decimals,
+    rescales: true,
+    toDisplay: (canonical) =>
+      roundTo(applyDisplayTransform(canonical, transform), decimals),
+    toCanonical: (display) =>
+      roundTo(invertDisplayTransform(display, transform), CANONICAL_DECIMALS),
+    toDisplayDelta: (canonicalDelta) =>
+      roundTo(applyDisplayTransformDelta(canonicalDelta, transform), decimals),
+    bounds: (canonical) => ({
+      min: ceilTo(applyDisplayTransform(canonical.min, transform), decimals),
+      max: floorTo(applyDisplayTransform(canonical.max, transform), decimals),
+    }),
+  };
+}