diff --git a/src/components/insights/__tests__/health-score-pillar-detail-bp-basis.test.tsx b/src/components/insights/__tests__/health-score-pillar-detail-bp-basis.test.tsx
new file mode 100644
index 000000000..6c952ca25
--- /dev/null
+++ b/src/components/insights/__tests__/health-score-pillar-detail-bp-basis.test.tsx
@@ -0,0 +1,208 @@
+/**
+ * v1.34.5 — the route from the blood-pressure score to its reason.
+ *
+ * A pillar reading 56 gave no way to find out why: the popover held the
+ * reference band, the personal target and the source, and nothing said
+ * which of the two axes had set the number, how far over its ceiling that
+ * axis sat, or that a reading exactly at the ceiling reads 85 rather than
+ * 100. These pin the three lines that answer it, in the two locales the
+ * maintainer reads, against the real bundles.
+ *
+ * The lines live behind a Radix popover, which only mounts once opened,
+ * so they are asserted through the pure formatter the card feeds it —
+ * the same strings the card shows, not a second copy of the copy.
+ */
+import { describe, expect, it } from "vitest";
+import { renderToStaticMarkup } from "react-dom/server";
+
+import { I18nProvider, useTranslations } from "@/lib/i18n/context";
+import type { Locale } from "@/lib/i18n/config";
+import type { BpScoreBasis } from "@/lib/analytics/bp-grade";
+import type { ScorePillarResult } from "@/lib/analytics/score/types";
+import {
+  pillarDetailLines,
+  type Translate,
+} from "../health-score-pillar-detail";
+
+function translator(locale: Locale = "en"): Translate {
+  let captured: Translate | null = null;
+  function Probe() {
+    captured = useTranslations().t;
+    return null;
+  }
+  renderToStaticMarkup(
+    <I18nProvider initialLocale={locale}>
+      <Probe />
+    </I18nProvider>,
+  );
+  if (!captured) throw new Error("translator probe did not run");
+  return captured;
+}
+
+function bloodPressure(scoreBasis?: BpScoreBasis): ScorePillarResult {
+  return {
+    id: "BLOOD_PRESSURE",
+    domain: "cardiometabolic",
+    result: {
+      status: "ok",
+      value: {
+        score: 56,
+        ...(scoreBasis ? { scoreBasis } : {}),
+        observed: {
+          value: 137,
+          unit: "mmHg",
+          label: "137/87 mmHg",
+          asOf: "2026-07-30T08:00:00.000Z",
+          sources: ["MANUAL"],
+        },
+        reference: {
+          kind: "clinical-threshold",
+          low: 120,
+          high: 129,
+          label: "120 to 129/70 to 79 mmHg",
+          source: "ESH 2023",
+        },
+        noiseFloor: 1,
+        deltaEligible: true,
+        deltaIdentity: "graded_bp_pair_series",
+      },
+      coverage: {
+        requiredInputs: 12,
+        presentInputs: 12,
+        historyDays: 60,
+        missing: [],
+      },
+      confidence: { score: 100, band: "high" },
+      provenance: {
+        inputs: ["BLOOD_PRESSURE"],
+        source: "live",
+        windowDays: 90,
+        computedAt: "2026-07-30T12:00:00.000Z",
+      },
+    },
+  };
+}
+
+const ABOVE_CEILING: BpScoreBasis = {
+  axis: "systolic",
+  relation: "above_ceiling",
+  offsetMmHg: 8,
+  boundaryMmHg: 129,
+};
+
+describe("blood-pressure score basis in the popover", () => {
+  it("leads with the binding axis, its distance and its ceiling", () => {
+    const lines = pillarDetailLines(bloodPressure(ABOVE_CEILING), {
+      t: translator(),
+      glucoseUnit: "mg/dL",
+    });
+    expect(lines[0]).toBe(
+      "Systolic sets this score: about 8 mmHg over its ceiling of 129 mmHg.",
+    );
+  });
+
+  it("names the diastolic axis when that is the one that bound", () => {
+    const lines = pillarDetailLines(
+      bloodPressure({
+        axis: "diastolic",
+        relation: "above_ceiling",
+        offsetMmHg: 9,
+        boundaryMmHg: 79,
+      }),
+      { t: translator(), glucoseUnit: "mg/dL" },
+    );
+    expect(lines[0]).toBe(
+      "Diastolic sets this score: about 9 mmHg over its ceiling of 79 mmHg.",
+    );
+  });
+
+  it("measures a hypotensive reading from the low-pressure floor", () => {
+    const lines = pillarDetailLines(
+      bloodPressure({
+        axis: "systolic",
+        relation: "below_floor",
+        offsetMmHg: 4,
+        boundaryMmHg: 90,
+      }),
+      { t: translator(), glucoseUnit: "mg/dL" },
+    );
+    expect(lines[0]).toBe(
+      "Systolic sets this score: about 4 mmHg under the low-pressure floor of 90 mmHg.",
+    );
+  });
+
+  it("says both axes are in band without naming a distance", () => {
+    const lines = pillarDetailLines(
+      bloodPressure({
+        axis: "systolic",
+        relation: "in_band",
+        offsetMmHg: 5,
+        boundaryMmHg: 129,
+      }),
+      { t: translator(), glucoseUnit: "mg/dL" },
+    );
+    expect(lines[0]).toBe(
+      "Both values are at or below their reference ceilings.",
+    );
+  });
+
+  it("explains the scale and the averaged reading, then the shipped lines", () => {
+    const lines = pillarDetailLines(bloodPressure(ABOVE_CEILING), {
+      t: translator(),
+      glucoseUnit: "mg/dL",
+    });
+    expect(lines[1]).toBe(
+      "At the ceiling the score is 85; 100 means roughly 12 mmHg below it.",
+    );
+    // The window comes off the pillar's own provenance, so the sentence
+    // cannot drift from the window the score was actually read over.
+    expect(lines[2]).toBe(
+      "Based on a recency-weighted average of the last 90 days, so it may not match any single reading.",
+    );
+    expect(lines).toHaveLength(5);
+    expect(lines[3]).toContain("ESH 2023");
+    expect(lines[4]).toContain("Source: MANUAL");
+  });
+
+  it("reads in German too", () => {
+    const lines = pillarDetailLines(bloodPressure(ABOVE_CEILING), {
+      t: translator("de"),
+      glucoseUnit: "mg/dL",
+    });
+    expect(lines[0]).toBe(
+      "Ausschlaggebend: Systolisch, etwa 8 mmHg über der Obergrenze von 129 mmHg.",
+    );
+    expect(lines[1]).toBe(
+      "An der Obergrenze liegt der Wert bei 85; 100 bedeutet rund 12 mmHg darunter.",
+    );
+    expect(lines[2]).toBe(
+      "Beruht auf einem Durchschnitt der letzten 90 Tage, der neuere Messungen stärker gewichtet, und kann deshalb von jeder einzelnen Messung abweichen.",
+    );
+  });
+
+  it("says nothing at all when the server published no basis", () => {
+    // The field is optional and blood-pressure-only: an older payload, or
+    // a pillar that has nothing of the kind to say, must fall back to the
+    // shipped lines rather than to an empty or invented sentence.
+    const lines = pillarDetailLines(bloodPressure(), {
+      t: translator(),
+      glucoseUnit: "mg/dL",
+    });
+    expect(lines).toHaveLength(2);
+    expect(lines[0]).toContain("ESH 2023");
+    expect(lines.join("\n")).not.toContain("mmHg over its ceiling");
+  });
+
+  it("leaves other pillars untouched", () => {
+    const glycaemia: ScorePillarResult = {
+      ...bloodPressure(ABOVE_CEILING),
+      id: "GLYCAEMIA",
+    };
+    const lines = pillarDetailLines(glycaemia, {
+      t: translator(),
+      glucoseUnit: "mg/dL",
+    });
+    expect(lines.join("\n")).not.toContain("sets this score");
+    expect(lines.join("\n")).not.toContain("At the ceiling");
+  });
+});
diff --git a/src/lib/analytics/__tests__/bp-grade.test.ts b/src/lib/analytics/__tests__/bp-grade.test.ts
index f3c330416..b0c6e8b6a 100644
--- a/src/lib/analytics/__tests__/bp-grade.test.ts
+++ b/src/lib/analytics/__tests__/bp-grade.test.ts
@@ -7,6 +7,8 @@
  * (low-to-mid 50s), not in the catastrophic band.
  */
 import { describe, expect, it } from "vitest";
+import { readFileSync } from "node:fs";
+import { join } from "node:path";
 import {
   gradeBpScore,
   gradeBpScoreFromSeries,
@@ -474,3 +476,53 @@ describe("gradeBpScoreFromSeries — the basis travels with the score", () => {
     expect(personal.score).toBeGreaterThan(clinical.score);
   });
 });
+
+/**
+ * The popover's scale line quotes two numbers out of this curve ("at the
+ * ceiling the score is 85; 100 means roughly 12 mmHg below it") because
+ * the sentence has to read naturally in six languages. That makes the
+ * copy and the anchors two places that must agree, so this pins them to
+ * each other: re-anchoring the curve turns this red and the six strings
+ * have to follow.
+ */
+describe("the scale the popover quotes", () => {
+  const AT_CEILING_SCORE = 85;
+  const OPTIMAL_OFFSET_MMHG = 12;
+
+  it("still scores 85 at the ceiling and 100 at twelve below it", () => {
+    expect(
+      bpScore({ sys: UNDER65.sysHigh, dia: UNDER65.diaHigh, target: UNDER65 }),
+    ).toBe(AT_CEILING_SCORE);
+    expect(
+      bpScore({
+        sys: UNDER65.sysHigh - OPTIMAL_OFFSET_MMHG,
+        dia: UNDER65.diaHigh - OPTIMAL_OFFSET_MMHG,
+        target: UNDER65,
+      }),
+    ).toBe(100);
+    // Twelve is the SMALLEST distance that reaches 100 — one less does not.
+    expect(
+      bpScore({
+        sys: UNDER65.sysHigh - (OPTIMAL_OFFSET_MMHG - 1),
+        dia: UNDER65.diaHigh - (OPTIMAL_OFFSET_MMHG - 1),
+        target: UNDER65,
+      }),
+    ).toBeLessThan(100);
+  });
+
+  it.each(["en", "de", "fr", "es", "it", "pl"])(
+    "quotes those same two numbers in %s",
+    (locale) => {
+      const bundle = JSON.parse(
+        readFileSync(
+          join(__dirname, "../../../../messages", `${locale}.json`),
+          "utf8",
+        ),
+      ) as { insights: { healthScore: Record<string, string> } };
+      const line = bundle.insights.healthScore.bpScale;
+      expect(line).toContain(String(AT_CEILING_SCORE));
+      expect(line).toContain(String(OPTIMAL_OFFSET_MMHG));
+      expect(line).toContain("100");
+    },
+  );
+});