diff --git a/scripts/convert-noncanonical-measurement-units.ts b/scripts/convert-noncanonical-measurement-units.ts
new file mode 100644
index 000000000..18a75cbda
--- /dev/null
+++ b/scripts/convert-noncanonical-measurement-units.ts
@@ -0,0 +1,104 @@
+/**
+ * Convert measurement rows stored in a RECOGNISED non-canonical unit to
+ * canonical SI, in place. Companion to
+ * `diagnose-noncanonical-measurement-units.ts` — run the diagnose first.
+ *
+ * SAFETY:
+ *   - Dry-run by default. Writes ONLY when called with `--execute`.
+ *   - Touches ONLY rows whose stored `unit` differs from the type's canonical
+ *     unit AND resolves through the shared alias resolver (lb/lbs/pound(s),
+ *     in/inch(es), °F, mmol/L). A row whose unit is already canonical, or whose
+ *     unit is unrecognised, is never touched.
+ *   - Each row is rewritten to the canonical `{ value, unit }` the same
+ *     resolver the CSV importer + MCP write path use produces, so the number is
+ *     re-expressed, never re-labelled in place (which would corrupt it).
+ *   - Affected users' measurement caches are busted at the end.
+ *
+ * This repairs the storage LABEL + value for the recognised-alias legacy rows
+ * (the MCP-leak class). It cannot repair a row whose unit was already canonical
+ * but whose value was a foreign unit — that class is not mechanically
+ * identifiable (see the diagnose script).
+ *
+ * Run (inside the app container):
+ *   pnpm dlx tsx scripts/convert-noncanonical-measurement-units.ts            # dry-run
+ *   pnpm dlx tsx scripts/convert-noncanonical-measurement-units.ts --execute  # write
+ */
+import "dotenv/config";
+
+import { prisma } from "@/lib/db";
+import { getUnitForType } from "@/lib/validations/measurement";
+import { resolveToCanonicalUnit } from "@/lib/measurements/unit-aliases";
+import { invalidateUserMeasurements } from "@/lib/cache/invalidate";
+
+async function main(): Promise<void> {
+  const execute = process.argv.includes("--execute");
+
+  const groups = await prisma.measurement.groupBy({
+    by: ["type", "unit"],
+    _count: { _all: true },
+  });
+  const convertibleGroups = groups.filter((g) => {
+    if (g.unit === null || g.unit === getUnitForType(g.type)) return false;
+    return resolveToCanonicalUnit(g.type, 1, g.unit) !== null;
+  });
+
+  if (convertibleGroups.length === 0) {
+    console.log(
+      "Nothing to convert — no recognised non-canonical units found.",
+    );
+    return;
+  }
+
+  const affectedUsers = new Set<string>();
+  let converted = 0;
+
+  for (const g of convertibleGroups) {
+    const canonical = getUnitForType(g.type);
+    const rows = await prisma.measurement.findMany({
+      where: { type: g.type, unit: g.unit },
+      select: { id: true, userId: true, value: true, unit: true },
+    });
+    for (const row of rows) {
+      const resolved = resolveToCanonicalUnit(
+        g.type,
+        row.value,
+        row.unit as string,
+      );
+      if (!resolved) continue; // defensive; group already filtered
+      converted += 1;
+      affectedUsers.add(row.userId);
+      console.log(
+        `  ${execute ? "convert" : "would convert"} ${g.type} ${row.id}: ` +
+          `${row.value} ${row.unit} -> ${resolved.value} ${resolved.unit}`,
+      );
+      if (execute) {
+        await prisma.measurement.update({
+          where: { id: row.id },
+          data: { value: resolved.value, unit: canonical },
+        });
+      }
+    }
+  }
+
+  if (execute) {
+    for (const userId of affectedUsers) {
+      invalidateUserMeasurements(userId, { evict: true });
+    }
+    console.log(
+      `\nConverted ${converted} row(s) across ${affectedUsers.size} user(s). ` +
+        "Rollups recompute on the next read/backfill.",
+    );
+  } else {
+    console.log(
+      `\nDry run: ${converted} row(s) across ${affectedUsers.size} user(s) ` +
+        "would be converted. Re-run with --execute to write.",
+    );
+  }
+}
+
+main()
+  .catch((err) => {
+    console.error(err);
+    process.exitCode = 1;
+  })
+  .finally(() => prisma.$disconnect());
diff --git a/scripts/diagnose-noncanonical-measurement-units.ts b/scripts/diagnose-noncanonical-measurement-units.ts
new file mode 100644
index 000000000..9c0667bda
--- /dev/null
+++ b/scripts/diagnose-noncanonical-measurement-units.ts
@@ -0,0 +1,76 @@
+/**
+ * Read-only diagnostic for measurement rows stored in a NON-canonical unit.
+ *
+ * Canonical storage is SI: every write path stamps `getUnitForType(type)`. The
+ * one historical leak was the MCP `log_measurement` tool, which persisted a
+ * caller-supplied `unit` verbatim (closed in v1.32.26). A row whose `unit`
+ * column differs from its type's canonical unit is such a legacy row, and it
+ * mislabels every display surface that trusts the column.
+ *
+ * This groups measurements by `(type, unit)` and prints every group whose
+ * `unit` is not the canonical unit for its type, flagging whether the stored
+ * unit is a RECOGNISED alias (mechanically convertible by the companion
+ * convert script) or UNKNOWN (needs a manual look). Nothing is written.
+ *
+ * NOT auto-fixable and deliberately out of scope: a row whose stored unit IS
+ * already canonical but whose VALUE was a foreign unit (e.g. a lb reading typed
+ * into the old kg-labelled entry form). Those are indistinguishable from real
+ * canonical readings; the reporter edits them via the record list.
+ *
+ * Run (inside the app container, which has DATABASE_URL):
+ *   pnpm dlx tsx scripts/diagnose-noncanonical-measurement-units.ts
+ */
+import "dotenv/config";
+
+import { prisma } from "@/lib/db";
+import { getUnitForType } from "@/lib/validations/measurement";
+import { resolveToCanonicalUnit } from "@/lib/measurements/unit-aliases";
+
+async function main(): Promise<void> {
+  const groups = await prisma.measurement.groupBy({
+    by: ["type", "unit"],
+    _count: { _all: true },
+  });
+
+  const mismatches = groups.filter((g) => {
+    if (g.unit === null) return false;
+    return g.unit !== getUnitForType(g.type);
+  });
+
+  if (mismatches.length === 0) {
+    console.log("No non-canonical measurement units found. Storage is clean.");
+    return;
+  }
+
+  let convertible = 0;
+  let unknown = 0;
+  console.log(
+    `Found ${mismatches.length} non-canonical (type, unit) group(s):\n`,
+  );
+  for (const g of mismatches.sort((a, b) => b._count._all - a._count._all)) {
+    const canonical = getUnitForType(g.type);
+    // Probe convertibility with a neutral value — only the recognition matters.
+    const recognised = resolveToCanonicalUnit(g.type, 1, g.unit as string);
+    const status = recognised ? "CONVERTIBLE" : "UNKNOWN — manual review";
+    if (recognised) convertible += g._count._all;
+    else unknown += g._count._all;
+    console.log(
+      `  ${g.type}: stored="${g.unit}" canonical="${canonical}" ` +
+        `rows=${g._count._all} [${status}]`,
+    );
+  }
+  console.log(
+    `\nTotals: ${convertible} row(s) convertible, ${unknown} row(s) unknown.`,
+  );
+  console.log(
+    "Convert the recognised aliases with:\n" +
+      "  pnpm dlx tsx scripts/convert-noncanonical-measurement-units.ts --execute",
+  );
+}
+
+main()
+  .catch((err) => {
+    console.error(err);
+    process.exitCode = 1;
+  })
+  .finally(() => prisma.$disconnect());
diff --git a/src/__tests__/unit-preference-display-guard.test.ts b/src/__tests__/unit-preference-display-guard.test.ts
new file mode 100644
index 000000000..ff91da3c0
--- /dev/null
+++ b/src/__tests__/unit-preference-display-guard.test.ts
@@ -0,0 +1,87 @@
+/**
+ * Structural guard (a tripwire, not a proof) for the metric/imperial unit
+ * fix (issue #627). The dangerous failure mode is a PARTIAL fix: entry converts
+ * but a display surface still hardcodes the canonical unit, so an imperial user
+ * sees converted-then-mislabelled soup. This walks the dashboard + insight page
+ * sources and asserts none of them passes a transformed type's DISPLAY UNIT
+ * (kg / lb / cm / in / °C / °F / km/h / mph / km / mi) or a hardcoded value
+ * scale as a literal prop — those must resolve from the user's preference
+ * through `useUnitDisplay()` instead.
+ *
+ * Mutation check: add `unit="kg"` back to any swept page and this goes red.
+ */
+import { readFileSync } from "node:fs";
+import { globSync } from "node:fs";
+import { join } from "node:path";
+
+import { describe, it, expect } from "vitest";
+
+import {
+  getDisplayTransform,
+  TRANSFORMED_TYPES,
+} from "@/lib/measurements/display-transform";
+
+const SRC = join(process.cwd(), "src");
+
+/** The set of display-unit strings a transformed type can render. */
+const TRANSFORMED_UNITS: ReadonlySet<string> = new Set(
+  [...TRANSFORMED_TYPES].flatMap((type) => [
+    getDisplayTransform(type, "metric").displayUnit,
+    getDisplayTransform(type, "imperial").displayUnit,
+  ]),
+);
+
+/** Swept surfaces: the dashboard client + every insights sub-page. */
+function sweptFiles(): string[] {
+  return [
+    join(SRC, "app", "page-client.tsx"),
+    ...globSync("app/insights/**/page.tsx", { cwd: SRC }).map((rel) =>
+      join(SRC, rel),
+    ),
+  ];
+}
+
+describe("unit-preference display guard", () => {
+  it("sweeps a non-empty set of surfaces", () => {
+    // Guards against a glob that silently matches nothing (a green void).
+    expect(sweptFiles().length).toBeGreaterThan(10);
+  });
+
+  it("no swept surface hardcodes a transformed type's display unit", () => {
+    const offenders: string[] = [];
+    for (const file of sweptFiles()) {
+      const src = readFileSync(file, "utf8");
+      for (const unit of TRANSFORMED_UNITS) {
+        // Match `unit="kg"` / `yAxisUnit="°C"` exactly (closing quote pinned so
+        // `unit="kg/m²"` — the excluded BMI unit — never trips it).
+        for (const prop of ["unit", "yAxisUnit"]) {
+          if (src.includes(`${prop}="${unit}"`)) {
+            offenders.push(`${file}: ${prop}="${unit}"`);
+          }
+        }
+      }
+    }
+    expect(offenders).toEqual([]);
+  });
+
+  it("no insights page hardcodes a numeric valueScale literal", () => {
+    // Transformed metrics resolve their scale from the transform; a literal
+    // `valueScale={3.6}` is the pre-fix hand-rolled scaling that double-scales.
+    const literal = /valueScale=\{\s*-?\d/;
+    const offenders = sweptFiles().filter((file) =>
+      literal.test(readFileSync(file, "utf8")),
+    );
+    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");
+      const imperial = getDisplayTransform(type, "imperial");
+      expect(metric.displayUnit).toBeTruthy();
+      expect(imperial.displayUnit).toBeTruthy();
+      expect(Number.isFinite(metric.factor)).toBe(true);
+      expect(Number.isFinite(imperial.factor)).toBe(true);
+    }
+  });
+});
diff --git a/src/components/measurements/__tests__/measurement-form-unit-label.test.tsx b/src/components/measurements/__tests__/measurement-form-unit-label.test.tsx
new file mode 100644
index 000000000..b53d0d50a
--- /dev/null
+++ b/src/components/measurements/__tests__/measurement-form-unit-label.test.tsx
@@ -0,0 +1,66 @@
+import { describe, expect, it, vi } from "vitest";
+import { renderToStaticMarkup } from "react-dom/server";
+
+/**
+ * v1.32.26 (issue #627) — the manual entry form labels its value field in the
+ * user's preferred unit for a type with a metric/imperial transform. A metric
+ * user sees "kg"; an imperial user sees "lb". The field is the entry boundary
+ * that converts the typed number back to canonical SI on submit, so the label
+ * and the stored unit must agree with the preference.
+ */
+
+let preference: "metric" | "imperial" = "metric";
+
+vi.mock("@/hooks/use-auth", () => ({
+  useAuth: () => ({
+    user: {
+      id: "u1",
+      username: "testuser",
+      role: "USER",
+      unitPreference: preference,
+    },
+    isAuthenticated: true,
+    isLoading: false,
+  }),
+}));
+
+vi.mock("@tanstack/react-query", () => ({
+  useQueryClient: () => ({
+    invalidateQueries: vi.fn(),
+    refetchQueries: vi.fn(),
+  }),
+}));
+
+vi.mock("@/lib/api/api-fetch", () => ({
+  apiPost: vi.fn().mockResolvedValue({}),
+}));
+
+import { I18nProvider } from "@/lib/i18n/context";
+import { MeasurementForm } from "../measurement-form";
+
+function render(): string {
+  return renderToStaticMarkup(
+    <I18nProvider initialLocale="en">
+      <MeasurementForm defaultType="WEIGHT" />
+    </I18nProvider>,
+  );
+}
+
+describe("MeasurementForm — preferred-unit value label", () => {
+  it("labels the weight field in kg for a metric user", () => {
+    preference = "metric";
+    const html = render();
+    expect(html).toContain("kg");
+    expect(html).not.toContain("lb");
+    // The metric placeholder (kg) is shown, not the imperial one.
+    expect(html).toContain('placeholder="75.5"');
+  });
+
+  it("labels the weight field in lb for an imperial user", () => {
+    preference = "imperial";
+    const html = render();
+    expect(html).toContain("lb");
+    // The imperial placeholder (lb) is shown.
+    expect(html).toContain('placeholder="165"');
+  });
+});
diff --git a/src/lib/mcp/__tests__/writes.test.ts b/src/lib/mcp/__tests__/writes.test.ts
index 32776ebf2..22c1eea9f 100644
--- a/src/lib/mcp/__tests__/writes.test.ts
+++ b/src/lib/mcp/__tests__/writes.test.ts
@@ -89,6 +89,52 @@ describe("logMcpMeasurement", () => {
     );
   });
 
+  it("converts a lb unit hint to canonical kg before writing", async () => {
+    const result = await logMcpMeasurement({
+      userId: "u-1",
+      type: "WEIGHT",
+      value: 210,
+      unit: "lb",
+      idempotencyKey: "key-lb",
+    });
+
+    expect(result.status).toBe("written");
+    const data = measurement.create.mock.calls[0][0].data;
+    expect(data.unit).toBe("kg");
+    // 210 lb → 95.25 kg (stored canonical, never the caller's lb verbatim).
+    expect(data.value).toBeCloseTo(210 * 0.45359237, 5);
+    if (result.status === "written") {
+      expect(result.measurement.unit).toBe("kg");
+    }
+  });
+
+  it("refuses an unsupported unit hint without writing", async () => {
+    const result = await logMcpMeasurement({
+      userId: "u-1",
+      type: "WEIGHT",
+      value: 12,
+      unit: "stone",
+      idempotencyKey: "key-stone",
+    });
+
+    expect(result.status).toBe("unsupported_unit");
+    expect(measurement.create).not.toHaveBeenCalled();
+  });
+
+  it("stamps canonical kg when the unit hint is omitted", async () => {
+    const result = await logMcpMeasurement({
+      userId: "u-1",
+      type: "WEIGHT",
+      value: 80,
+      idempotencyKey: "key-none",
+    });
+
+    expect(result.status).toBe("written");
+    const data = measurement.create.mock.calls[0][0].data;
+    expect(data.unit).toBe("kg");
+    expect(data.value).toBe(80);
+  });
+
   it("refuses a non-capturable / clinical-only type without writing", async () => {
     const result = await logMcpMeasurement({
       userId: "u-1",
diff --git a/src/lib/measurements/__tests__/display-transform.test.ts b/src/lib/measurements/__tests__/display-transform.test.ts
index 48165c42a..e6203f227 100644
--- a/src/lib/measurements/__tests__/display-transform.test.ts
+++ b/src/lib/measurements/__tests__/display-transform.test.ts
@@ -2,7 +2,11 @@ import { describe, it, expect } from "vitest";
 
 import {
   applyDisplayTransform,
+  applyDisplayTransformDelta,
+  invertDisplayTransform,
   getDisplayTransform,
+  hasDisplayTransform,
+  TRANSFORMED_TYPES,
   DEFAULT_UNIT_PREFERENCE,
 } from "../display-transform";
 
@@ -65,4 +69,116 @@ describe("display-transform", () => {
       getDisplayTransform("WALKING_SPEED", "metric"),
     );
   });
+
+  // ── v1.32.26 — weight-class / length / temperature registry ──
+
+  it("converts WEIGHT kg → lb on the imperial branch", () => {
+    const metric = getDisplayTransform("WEIGHT", "metric");
+    expect(metric.factor).toBe(1);
+    expect(metric.displayUnit).toBe("kg");
+    // Metric is the identity on the number — byte-identical to storage.
+    expect(applyDisplayTransform(95.25, metric)).toBe(95.25);
+
+    const imperial = getDisplayTransform("WEIGHT", "imperial");
+    expect(imperial.displayUnit).toBe("lb");
+    // 95.25 kg → 210.0 lb.
+    expect(applyDisplayTransform(95.25, imperial)).toBeCloseTo(210.0, 1);
+  });
+
+  it("shares the mass branch across every body-mass metric", () => {
+    for (const type of [
+      "TOTAL_BODY_WATER",
+      "BONE_MASS",
+      "FAT_MASS",
+      "FAT_FREE_MASS",
+      "MUSCLE_MASS",
+      "LEAN_BODY_MASS",
+      "GRIP_STRENGTH",
+    ]) {
+      expect(getDisplayTransform(type, "imperial").displayUnit).toBe("lb");
+      expect(getDisplayTransform(type, "metric").displayUnit).toBe("kg");
+      // 10 kg → 22.05 lb.
+      expect(
+        applyDisplayTransform(10, getDisplayTransform(type, "imperial")),
+      ).toBeCloseTo(22.0462, 3);
+    }
+  });
+
+  it("converts WAIST_CIRCUMFERENCE cm → in", () => {
+    const imperial = getDisplayTransform("WAIST_CIRCUMFERENCE", "imperial");
+    expect(imperial.displayUnit).toBe("in");
+    // 84 cm → 33.07 in.
+    expect(applyDisplayTransform(84, imperial)).toBeCloseTo(33.07, 2);
+  });
+
+  it("converts an ABSOLUTE temperature °C → °F affinely (factor + offset)", () => {
+    const metric = getDisplayTransform("BODY_TEMPERATURE", "metric");
+    expect(metric.displayUnit).toBe("°C");
+    expect(metric.offset ?? 0).toBe(0);
+
+    const imperial = getDisplayTransform("BODY_TEMPERATURE", "imperial");
+    expect(imperial.displayUnit).toBe("°F");
+    expect(imperial.factor).toBe(1.8);
+    expect(imperial.offset).toBe(32);
+    // 36.6 °C → 97.88 °F (the +32 shift MUST apply to an absolute reading).
+    expect(applyDisplayTransform(36.6, imperial)).toBeCloseTo(97.88, 2);
+    // 0 °C → 32 °F (not 0).
+    expect(applyDisplayTransform(0, imperial)).toBe(32);
+  });
+
+  it("skin + wrist temperature share the affine temperature branch", () => {
+    for (const type of ["SKIN_TEMPERATURE", "WRIST_TEMPERATURE"]) {
+      const imperial = getDisplayTransform(type, "imperial");
+      expect(imperial.displayUnit).toBe("°F");
+      expect(imperial.offset).toBe(32);
+    }
+  });
+
+  it("BODY_TEMPERATURE_DEVIATION scales °C→°F WITHOUT the offset (it is a Δ)", () => {
+    const imperial = getDisplayTransform(
+      "BODY_TEMPERATURE_DEVIATION",
+      "imperial",
+    );
+    expect(imperial.displayUnit).toBe("°F");
+    expect(imperial.factor).toBe(1.8);
+    // A signed deviation is a delta: 1 Δ°C is a 1.8 Δ°F, NEVER 33.8 °F.
+    expect(imperial.offset ?? 0).toBe(0);
+    expect(applyDisplayTransform(1, imperial)).toBeCloseTo(1.8, 5);
+  });
+
+  it("the delta helper NEVER applies the affine offset", () => {
+    const imperial = getDisplayTransform("BODY_TEMPERATURE", "imperial");
+    // Same absolute transform (offset 32), but a delta must be factor-only.
+    expect(applyDisplayTransform(1, imperial)).toBe(33.8);
+    expect(applyDisplayTransformDelta(1, imperial)).toBeCloseTo(1.8, 5);
+    // A 2 °C rise reads as a 3.6 °F rise, not a 35.6 °F reading.
+    expect(applyDisplayTransformDelta(2, imperial)).toBeCloseTo(3.6, 5);
+  });
+
+  it("inverse round-trips every registered branch (entry ⇄ display)", () => {
+    for (const type of TRANSFORMED_TYPES) {
+      for (const pref of ["metric", "imperial"] as const) {
+        const transform = getDisplayTransform(type, pref);
+        for (const raw of [0, 1, 36.6, 84, 95.25, 210]) {
+          const shown = applyDisplayTransform(raw, transform);
+          expect(invertDisplayTransform(shown, transform)).toBeCloseTo(raw, 6);
+        }
+      }
+    }
+  });
+
+  it("hasDisplayTransform + TRANSFORMED_TYPES agree, and exclude BMI/glucose", () => {
+    expect(hasDisplayTransform("WEIGHT")).toBe(true);
+    expect(hasDisplayTransform("BODY_TEMPERATURE")).toBe(true);
+    expect(hasDisplayTransform("PULSE")).toBe(false);
+    // Deliberately excluded (own preference / universal unit).
+    expect(TRANSFORMED_TYPES.has("BLOOD_GLUCOSE")).toBe(false);
+    expect(TRANSFORMED_TYPES.has("BODY_MASS_INDEX")).toBe(false);
+    // Every registered type resolves a non-identity or symbol-only metric
+    // branch, and both branches exist.
+    for (const type of TRANSFORMED_TYPES) {
+      expect(getDisplayTransform(type, "metric").displayUnit).toBeTruthy();
+      expect(getDisplayTransform(type, "imperial").displayUnit).toBeTruthy();
+    }
+  });
 });
diff --git a/src/lib/measurements/__tests__/unit-aliases.test.ts b/src/lib/measurements/__tests__/unit-aliases.test.ts
new file mode 100644
index 000000000..a12f4d860
--- /dev/null
+++ b/src/lib/measurements/__tests__/unit-aliases.test.ts
@@ -0,0 +1,70 @@
+import { describe, it, expect } from "vitest";
+
+import { resolveToCanonicalUnit } from "../unit-aliases";
+
+describe("resolveToCanonicalUnit", () => {
+  it("passes the canonical unit through case-insensitively", () => {
+    expect(resolveToCanonicalUnit("WEIGHT", 80, "kg")).toEqual({
+      value: 80,
+      unit: "kg",
+    });
+    expect(resolveToCanonicalUnit("WEIGHT", 80, "KG")).toEqual({
+      value: 80,
+      unit: "kg",
+    });
+    expect(resolveToCanonicalUnit("BLOOD_GLUCOSE", 95, "MG/DL")).toEqual({
+      value: 95,
+      unit: "mg/dL",
+    });
+  });
+
+  it("converts a lb weight to canonical kg (exact factor)", () => {
+    const out = resolveToCanonicalUnit("WEIGHT", 210, "lb");
+    expect(out?.unit).toBe("kg");
+    expect(out?.value).toBeCloseTo(210 * 0.45359237, 6);
+    // aliases
+    for (const alias of ["lbs", "pound", "pounds", "LB"]) {
+      expect(resolveToCanonicalUnit("WEIGHT", 1, alias)?.unit).toBe("kg");
+    }
+  });
+
+  it("converts lb for every body-mass metric, not just WEIGHT", () => {
+    for (const type of ["MUSCLE_MASS", "FAT_MASS", "BONE_MASS"]) {
+      const out = resolveToCanonicalUnit(type, 22.0462, "lb");
+      expect(out?.unit).toBe("kg");
+      expect(out?.value).toBeCloseTo(10, 3);
+    }
+  });
+
+  it("converts waist inches to canonical cm", () => {
+    const out = resolveToCanonicalUnit("WAIST_CIRCUMFERENCE", 33, "in");
+    expect(out?.unit).toBe("cm");
+    expect(out?.value).toBeCloseTo(83.82, 2);
+  });
+
+  it("converts an absolute °F reading to canonical celsius", () => {
+    const out = resolveToCanonicalUnit("BODY_TEMPERATURE", 98.6, "°F");
+    expect(out?.unit).toBe("celsius");
+    expect(out?.value).toBeCloseTo(37, 5);
+    // an explicit celsius spelling also normalises to the canonical string
+    expect(resolveToCanonicalUnit("BODY_TEMPERATURE", 37, "°C")).toEqual({
+      value: 37,
+      unit: "celsius",
+    });
+  });
+
+  it("converts glucose mmol/L to canonical mg/dL", () => {
+    const out = resolveToCanonicalUnit("BLOOD_GLUCOSE", 5.3, "mmol/L");
+    expect(out?.unit).toBe("mg/dL");
+    expect(out?.value).toBeCloseTo(5.3 * 18.016, 3);
+  });
+
+  it("refuses an unrecognised or type-mismatched unit (never mis-stores)", () => {
+    expect(resolveToCanonicalUnit("WEIGHT", 12, "stone")).toBeNull();
+    expect(resolveToCanonicalUnit("WEIGHT", 12, "°F")).toBeNull();
+    // lb is not a waist unit
+    expect(resolveToCanonicalUnit("WAIST_CIRCUMFERENCE", 12, "lb")).toBeNull();
+    // mmol/L is not a weight unit
+    expect(resolveToCanonicalUnit("WEIGHT", 12, "mmol/L")).toBeNull();
+  });
+});