diff --git a/src/app/api/insights/correlations/route.ts b/src/app/api/insights/correlations/route.ts
index dea015144..383c5df54 100644
--- a/src/app/api/insights/correlations/route.ts
+++ b/src/app/api/insights/correlations/route.ts
@@ -26,11 +26,27 @@ import { wallClockInTz } from "@/lib/tz/wall-clock";
 import type { MeasurementType } from "@/generated/prisma/client";
 import {
   discoverCorrelations,
+  discoveryMeasurementTypes,
   DISCOVERY_BEHAVIOURS,
   DISCOVERY_OUTCOMES,
+  MEDICATION_COMPLIANCE_CHANNEL_KEY,
+  SYMPTOM_SEVERITY_CHANNEL_KEY,
   type DailySeriesPoint,
   type NamedSeries,
 } from "@/lib/insights/correlation-discovery";
+import {
+  buildComplianceMedicationContext,
+  buildMedicationComplianceBundle,
+  lastNonSkippedTakenAt,
+  SCHEDULE_COMPLIANCE_SELECT,
+} from "@/lib/analytics/compliance";
+import {
+  buildComplianceDailySeries,
+  buildSymptomSeverityDailySeries,
+  type SymptomDayLogRow,
+  type SymptomEpisodeSpan,
+} from "@/lib/insights/correlation-series-builders";
+import type { DoseHistoryRow } from "@/lib/medications/scheduling/dose-history";
 
 export const dynamic = "force-dynamic";
 
@@ -65,6 +81,148 @@ function toDailyMeans(
     .sort((a, b) => (a.day < b.day ? -1 : 1));
 }
 
+/**
+ * v1.21.0 (FDREXTEND) — build the user's MEDICATION_COMPLIANCE daily series.
+ *
+ * Pools every active, non-PRN medication's unified dose-history ledger over the
+ * window, then collapses to one per-day adherence rate (user-tz day keys). A
+ * user with no active medications (or no resolved slots) yields an empty
+ * series, so the channel degrades to absent.
+ */
+async function buildUserComplianceSeries(
+  userId: string,
+  since: Date,
+  tz: string,
+): Promise<NamedSeries> {
+  const medications = await prisma.medication.findMany({
+    // PRN (as-needed) medications have no expected doses → no defensible rate.
+    where: { userId, active: true, asNeeded: false },
+    include: {
+      schedules: { select: SCHEDULE_COMPLIANCE_SELECT },
+      scheduleRevisions: { orderBy: { validFrom: "asc" } },
+    },
+    orderBy: { name: "asc" },
+  });
+  if (medications.length === 0) {
+    return {
+      key: MEDICATION_COMPLIANCE_CHANNEL_KEY,
+      role: "behaviour",
+      points: [],
+    };
+  }
+
+  const events = await prisma.medicationIntakeEvent.findMany({
+    where: {
+      userId,
+      deletedAt: null,
+      medicationId: { in: medications.map((med) => med.id) },
+      scheduledFor: { gte: since },
+    },
+    orderBy: { scheduledFor: "asc" },
+    select: {
+      medicationId: true,
+      scheduledFor: true,
+      takenAt: true,
+      skipped: true,
+    },
+  });
+
+  const now = new Date();
+  const ledgerRows: DoseHistoryRow[] = [];
+  for (const medication of medications) {
+    const medEvents = events.filter((e) => e.medicationId === medication.id);
+    const ctx = buildComplianceMedicationContext(
+      medication,
+      lastNonSkippedTakenAt(medEvents),
+      tz,
+    );
+    const bundle = buildMedicationComplianceBundle(
+      medEvents,
+      medication.schedules,
+      ctx,
+      now,
+    );
+    ledgerRows.push(...bundle.ledgerRows);
+  }
+
+  return buildComplianceDailySeries(ledgerRows, tz);
+}
+
+/**
+ * v1.21.0 (FDREXTEND) — build the user's SYMPTOM_SEVERITY daily series (role set
+ * by the caller). Reads every in-window illness episode + its day-logs; the
+ * builder zero-fills healthy days ONLY across real episode spans, so a user
+ * with no episodes yields an empty series that degrades to absent.
+ */
+async function buildUserSymptomSeries(
+  userId: string,
+  since: Date,
+  now: Date,
+  tz: string,
+): Promise<NamedSeries> {
+  const episodes = await prisma.illnessEpisode.findMany({
+    // An episode overlaps the window when it onset before `now` and either is
+    // ongoing or resolved at/after the window start.
+    where: {
+      userId,
+      deletedAt: null,
+      onsetAt: { lte: now },
+      OR: [{ resolvedAt: null }, { resolvedAt: { gte: since } }],
+    },
+    select: { id: true, onsetAt: true, resolvedAt: true },
+  });
+  if (episodes.length === 0) {
+    return { key: SYMPTOM_SEVERITY_CHANNEL_KEY, role: "outcome", points: [] };
+  }
+
+  const dayLogRows = await prisma.illnessDayLog.findMany({
+    where: {
+      userId,
+      deletedAt: null,
+      episodeId: { in: episodes.map((e) => e.id) },
+    },
+    select: {
+      date: true,
+      functionalImpact: true,
+      symptomLinks: { select: { severity: true } },
+    },
+  });
+
+  // Collapse each day-log to one burden value (functionalImpact, else the day's
+  // max linked symptom severity) — the same rule the recovery-gap track uses.
+  const dayLogs: SymptomDayLogRow[] = [];
+  for (const row of dayLogRows) {
+    if (row.functionalImpact != null) {
+      dayLogs.push({ day: row.date, impact: row.functionalImpact });
+      continue;
+    }
+    let maxSeverity: number | null = null;
+    for (const link of row.symptomLinks) {
+      if (link.severity == null) continue;
+      maxSeverity =
+        maxSeverity === null
+          ? link.severity
+          : Math.max(maxSeverity, link.severity);
+    }
+    if (maxSeverity != null)
+      dayLogs.push({ day: row.date, impact: maxSeverity });
+  }
+
+  const spans: SymptomEpisodeSpan[] = episodes.map((e) => ({
+    onsetAt: e.onsetAt,
+    resolvedAt: e.resolvedAt,
+  }));
+
+  return buildSymptomSeverityDailySeries({
+    dayLogs,
+    episodes: spans,
+    tz,
+    windowStart: since,
+    windowEnd: now,
+    role: "outcome",
+  });
+}
+
 export const GET = apiHandler(async () => {
   const { user } = await requireAuth();
 
@@ -85,16 +243,19 @@ export const GET = apiHandler(async () => {
     select: { timezone: true },
   });
   const tz = profile?.timezone ?? "Europe/Berlin";
-  const since = new Date(Date.now() - WINDOW_DAYS * MS_PER_DAY);
+  const now = new Date();
+  const since = new Date(now.getTime() - WINDOW_DAYS * MS_PER_DAY);
 
-  // MOOD is backed by mood entries, not measurements — it appears as both a
-  // behaviour and (v1.11.5 F3) an outcome channel, so filter it out of the
-  // measurement type list on either side.
-  const behaviourTypes = DISCOVERY_BEHAVIOURS.filter(
-    (k) => k !== "MOOD",
+  // Non-MeasurementType channels are backed by other models, not measurements —
+  // MOOD (MoodEntry), MEDICATION_COMPLIANCE (the dose-history ledger), and
+  // SYMPTOM_SEVERITY (the illness day-log). `discoveryMeasurementTypes` drops
+  // them so the `type IN (...)` query carries only real enum values; each is
+  // built from its own source below and folded into the series.
+  const behaviourTypes = discoveryMeasurementTypes(
+    DISCOVERY_BEHAVIOURS,
   ) as MeasurementType[];
-  const outcomeTypes = DISCOVERY_OUTCOMES.filter(
-    (k) => k !== "MOOD",
+  const outcomeTypes = discoveryMeasurementTypes(
+    DISCOVERY_OUTCOMES,
   ) as MeasurementType[];
 
   const [measurements, moodEntries] = await Promise.all([
@@ -134,20 +295,33 @@ export const GET = apiHandler(async () => {
     tz,
   );
 
+  // v1.21.0 (FDREXTEND) — build the two non-measurement, non-mood channels from
+  // their own sources. Each degrades to an empty series when the user has no
+  // data, so the discovery loop drops the channel (it cannot clear n ≥ 20).
+  const complianceSeries = await buildUserComplianceSeries(user.id, since, tz);
+  const symptomSeries = await buildUserSymptomSeries(user.id, since, now, tz);
+
+  const points = (key: string): DailySeriesPoint[] =>
+    key === "MOOD"
+      ? moodDaily
+      : toDailyMeans(measurementsByType.get(key) ?? [], tz);
+
   const series: NamedSeries[] = [];
   for (const key of DISCOVERY_BEHAVIOURS) {
-    const points =
-      key === "MOOD"
-        ? moodDaily
-        : toDailyMeans(measurementsByType.get(key) ?? [], tz);
-    series.push({ key, role: "behaviour", points });
+    if (key === MEDICATION_COMPLIANCE_CHANNEL_KEY) {
+      series.push(complianceSeries);
+    } else if (key === SYMPTOM_SEVERITY_CHANNEL_KEY) {
+      series.push({ ...symptomSeries, role: "behaviour" });
+    } else {
+      series.push({ key, role: "behaviour", points: points(key) });
+    }
   }
   for (const key of DISCOVERY_OUTCOMES) {
-    const points =
-      key === "MOOD"
-        ? moodDaily
-        : toDailyMeans(measurementsByType.get(key) ?? [], tz);
-    series.push({ key, role: "outcome", points });
+    if (key === SYMPTOM_SEVERITY_CHANNEL_KEY) {
+      series.push({ ...symptomSeries, role: "outcome" });
+    } else {
+      series.push({ key, role: "outcome", points: points(key) });
+    }
   }
 
   const result = discoverCorrelations(series);
@@ -158,6 +332,10 @@ export const GET = apiHandler(async () => {
       pairs_tested: result.pairsTested,
       discovered: result.discovered.length,
       fdr_q: result.fdrQ,
+      // FDREXTEND — per-channel day-counts so a dashboard can see whether the
+      // two sparse new channels reached the n ≥ 20 floor or degraded to absent.
+      compliance_days: complianceSeries.points.length,
+      symptom_days: symptomSeries.points.length,
     },
   });
 
diff --git a/src/lib/insights/__tests__/correlation-discovery.test.ts b/src/lib/insights/__tests__/correlation-discovery.test.ts
index 18845fcc5..8eb2bff08 100644
--- a/src/lib/insights/__tests__/correlation-discovery.test.ts
+++ b/src/lib/insights/__tests__/correlation-discovery.test.ts
@@ -366,3 +366,166 @@ describe("D2-2 — effect-size floor on discovered drivers", () => {
     expect(pair!.interpretation).toMatch(/never a cause/);
   });
 });
+
+// ── FDREXTEND — medication compliance + symptom severity channels ─────
+
+import {
+  DISCOVERY_BEHAVIOURS,
+  MEDICATION_COMPLIANCE_CHANNEL_KEY,
+  SYMPTOM_SEVERITY_CHANNEL_KEY,
+} from "../correlation-discovery";
+
+describe("compliance + symptom channels (FDREXTEND)", () => {
+  it("registers compliance as a behaviour and symptom in both roles", () => {
+    expect(DISCOVERY_BEHAVIOURS).toContain(MEDICATION_COMPLIANCE_CHANNEL_KEY);
+    expect(DISCOVERY_BEHAVIOURS).toContain(SYMPTOM_SEVERITY_CHANNEL_KEY);
+    expect(DISCOVERY_OUTCOMES).toContain(SYMPTOM_SEVERITY_CHANNEL_KEY);
+  });
+
+  it("each new channel is its own metricFamily (no shared collapse)", () => {
+    expect(metricFamily(MEDICATION_COMPLIANCE_CHANNEL_KEY)).toBe(
+      MEDICATION_COMPLIANCE_CHANNEL_KEY,
+    );
+    expect(metricFamily(SYMPTOM_SEVERITY_CHANNEL_KEY)).toBe(
+      SYMPTOM_SEVERITY_CHANNEL_KEY,
+    );
+    // Neither shares a family with a vital / sleep / mood channel, so they can
+    // pair cross-domain.
+    expect(metricFamily(MEDICATION_COMPLIANCE_CHANNEL_KEY)).not.toBe(
+      metricFamily(SYMPTOM_SEVERITY_CHANNEL_KEY),
+    );
+    expect(metricFamily(MEDICATION_COMPLIANCE_CHANNEL_KEY)).not.toBe(
+      metricFamily("RESTING_HEART_RATE"),
+    );
+  });
+
+  it("surfaces an adherence-dip → next-day symptom-flare link at a confident tier", () => {
+    // 70 contiguous days. Lower adherence on day D drives a higher symptom
+    // burden on day D+1 (the flagship cross-metric link). Adherence oscillates
+    // 100/70/40; symptom[d+1] = (100 - adherence[d]) scaled into 0..3.
+    const n = 70;
+    const adherence = Array.from({ length: n }, (_, i) =>
+      i % 3 === 0 ? 100 : i % 3 === 1 ? 70 : 40,
+    );
+    const symptom = [
+      0,
+      ...adherence
+        .slice(0, n - 1)
+        // (100 - a) maps 0..60 → ~0..3, plus a tiny deterministic jitter so the
+        // pair is not a perfect line (a real-world-shaped strong link).
+        .map((a, i) => ((100 - a) / 20) * (i % 2 === 0 ? 1.0 : 0.98)),
+    ];
+    const result = discoverCorrelations([
+      {
+        key: MEDICATION_COMPLIANCE_CHANNEL_KEY,
+        role: "behaviour",
+        points: longSeries(adherence),
+      },
+      {
+        key: SYMPTOM_SEVERITY_CHANNEL_KEY,
+        role: "outcome",
+        points: longSeries(symptom),
+      },
+    ]);
+    const pair = result.discovered.find(
+      (p) =>
+        p.behaviour === MEDICATION_COMPLIANCE_CHANNEL_KEY &&
+        p.outcome === SYMPTOM_SEVERITY_CHANNEL_KEY,
+    );
+    expect(pair).toBeDefined();
+    expect(pair!.n).toBeGreaterThanOrEqual(20);
+    // Negative: higher adherence → lower next-day symptom burden.
+    expect(pair!.r).toBeLessThan(0);
+    expect(pair!.tier).toBe("high");
+    expect(pair!.interpretation).toMatch(/medication compliance/);
+    expect(pair!.interpretation).toMatch(/symptom severity/);
+    expect(pair!.interpretation).toMatch(/not a cause/);
+  });
+
+  it("does NOT surface a link when the overlap is below the n ≥ 20 floor", () => {
+    // A real adherence→symptom relationship but only ~10 paired days: sparse
+    // logging must withhold, never fabricate a confident driver.
+    const n = 12;
+    const adherence = Array.from({ length: n }, (_, i) =>
+      i % 2 === 0 ? 100 : 40,
+    );
+    const symptom = [
+      0,
+      ...adherence.slice(0, n - 1).map((a) => (100 - a) / 30),
+    ];
+    const result = discoverCorrelations([
+      {
+        key: MEDICATION_COMPLIANCE_CHANNEL_KEY,
+        role: "behaviour",
+        points: longSeries(adherence),
+      },
+      {
+        key: SYMPTOM_SEVERITY_CHANNEL_KEY,
+        role: "outcome",
+        points: longSeries(symptom),
+      },
+    ]);
+    // Below the floor the pair is never even tested.
+    expect(result.pairsTested).toBe(0);
+    expect(result.discovered).toHaveLength(0);
+  });
+
+  it("never tests the symptom → symptom self-lag", () => {
+    const n = 40;
+    const symptom = Array.from({ length: n }, (_, i) => (i % 4) / 2);
+    const result = discoverCorrelations([
+      {
+        key: SYMPTOM_SEVERITY_CHANNEL_KEY,
+        role: "behaviour",
+        points: longSeries(symptom),
+      },
+      {
+        key: SYMPTOM_SEVERITY_CHANNEL_KEY,
+        role: "outcome",
+        points: longSeries(symptom),
+      },
+    ]);
+    expect(
+      result.discovered.find(
+        (p) =>
+          p.behaviour === SYMPTOM_SEVERITY_CHANNEL_KEY &&
+          p.outcome === SYMPTOM_SEVERITY_CHANNEL_KEY,
+      ),
+    ).toBeUndefined();
+    expect(result.pairsTested).toBe(0);
+  });
+
+  it("compliance can pair with a vital outcome (cross-domain)", () => {
+    // Adherence dip today → resting HR drift up tomorrow. Confirms the channel
+    // is free to pair with vitals, not just symptom.
+    const n = 70;
+    const adherence = Array.from({ length: n }, (_, i) =>
+      i % 3 === 0 ? 100 : i % 3 === 1 ? 65 : 35,
+    );
+    const rhr = [
+      55,
+      ...adherence
+        .slice(0, n - 1)
+        .map((a, i) => 55 + (100 - a) / 6 + (i % 2 === 0 ? 0.1 : -0.1)),
+    ];
+    const result = discoverCorrelations([
+      {
+        key: MEDICATION_COMPLIANCE_CHANNEL_KEY,
+        role: "behaviour",
+        points: longSeries(adherence),
+      },
+      {
+        key: "RESTING_HEART_RATE",
+        role: "outcome",
+        points: longSeries(rhr),
+      },
+    ]);
+    const pair = result.discovered.find(
+      (p) =>
+        p.behaviour === MEDICATION_COMPLIANCE_CHANNEL_KEY &&
+        p.outcome === "RESTING_HEART_RATE",
+    );
+    expect(pair).toBeDefined();
+    expect(pair!.r).toBeLessThan(0); // higher adherence → lower next-day RHR
+  });
+});
diff --git a/src/lib/insights/__tests__/correlation-series-builders.test.ts b/src/lib/insights/__tests__/correlation-series-builders.test.ts
new file mode 100644
index 000000000..5c3b9a78c
--- /dev/null
+++ b/src/lib/insights/__tests__/correlation-series-builders.test.ts
@@ -0,0 +1,264 @@
+import { describe, it, expect } from "vitest";
+
+import {
+  buildComplianceDailySeries,
+  buildSymptomSeverityDailySeries,
+  type SymptomDayLogRow,
+  type SymptomEpisodeSpan,
+} from "../correlation-series-builders";
+import {
+  discoverCorrelations,
+  MEDICATION_COMPLIANCE_CHANNEL_KEY,
+  SYMPTOM_SEVERITY_CHANNEL_KEY,
+  type NamedSeries,
+} from "../correlation-discovery";
+import type { DoseHistoryRow } from "@/lib/medications/scheduling/dose-history";
+
+/** Minimal slot ledger row at a UTC instant with a given status. */
+function slot(at: string, status: DoseHistoryRow["status"]): DoseHistoryRow {
+  return { kind: "slot", at: new Date(at), status } as DoseHistoryRow;
+}
+
+const MS_PER_DAY = 24 * 60 * 60 * 1000;
+
+describe("buildComplianceDailySeries", () => {
+  it("computes a per-day rate pooled across slots, keyed in the user tz", () => {
+    const rows: DoseHistoryRow[] = [
+      // 2026-03-02 (Berlin): 1 taken, 1 missed → 50%.
+      slot("2026-03-02T07:00:00Z", "taken_on_time"),
+      slot("2026-03-02T19:00:00Z", "missed"),
+      // 2026-03-03 (Berlin): both taken → 100%.
+      slot("2026-03-03T07:00:00Z", "taken_on_time"),
+      slot("2026-03-03T19:00:00Z", "taken_late"),
+    ];
+    const series = buildComplianceDailySeries(rows, "Europe/Berlin");
+    expect(series.key).toBe(MEDICATION_COMPLIANCE_CHANNEL_KEY);
+    expect(series.role).toBe("behaviour");
+    expect(series.points).toEqual([
+      { day: "2026-03-02", value: 50 },
+      { day: "2026-03-03", value: 100 },
+    ]);
+  });
+
+  it("re-keys late-night instants into the correct user-tz day (not UTC)", () => {
+    // 2026-03-02T23:30Z is 2026-03-03 00:30 in Berlin (UTC+1) — must bucket on
+    // the Berlin day, proving the day-key is tz-aware, not a UTC slice.
+    const rows: DoseHistoryRow[] = [
+      slot("2026-03-02T23:30:00Z", "taken_on_time"),
+    ];
+    const series = buildComplianceDailySeries(rows, "Europe/Berlin");
+    expect(series.points).toEqual([{ day: "2026-03-03", value: 100 }]);
+  });
+
+  it("excludes skipped / upcoming / ad-hoc rows from the denominator", () => {
+    const rows: DoseHistoryRow[] = [
+      slot("2026-03-02T07:00:00Z", "taken_on_time"),
+      slot("2026-03-02T12:00:00Z", "skipped"),
+      slot("2026-03-02T19:00:00Z", "upcoming"),
+      {
+        kind: "ad_hoc",
+        at: new Date("2026-03-02T15:00:00Z"),
+        status: "ad_hoc",
+      } as DoseHistoryRow,
+    ];
+    const series = buildComplianceDailySeries(rows, "Europe/Berlin");
+    // Only the one taken slot counts → 100%, denominator 1.
+    expect(series.points).toEqual([{ day: "2026-03-02", value: 100 }]);
+  });
+
+  it("degrades to an empty series when no resolved slots exist", () => {
+    const rows: DoseHistoryRow[] = [
+      slot("2026-03-02T07:00:00Z", "skipped"),
+      slot("2026-03-02T19:00:00Z", "upcoming"),
+    ];
+    const series = buildComplianceDailySeries(rows, "Europe/Berlin");
+    expect(series.points).toHaveLength(0);
+  });
+});
+
+describe("buildSymptomSeverityDailySeries", () => {
+  const tz = "Europe/Berlin";
+
+  it("zero-fills healthy days only across a real episode span", () => {
+    // Episode runs 2026-03-01 → 2026-03-05. Logs: impact 2 on the 2nd, 3 on the
+    // 3rd. The other in-span days fill to 0 (healthy).
+    const windowStart = new Date("2026-02-01T00:00:00Z");
+    const windowEnd = new Date("2026-03-31T00:00:00Z");
+    const episodes: SymptomEpisodeSpan[] = [
+      {
+        onsetAt: new Date("2026-03-01T08:00:00Z"),
+        resolvedAt: new Date("2026-03-05T08:00:00Z"),
+      },
+    ];
+    const dayLogs: SymptomDayLogRow[] = [
+      { day: "2026-03-02", impact: 2 },
+      { day: "2026-03-03", impact: 3 },
+    ];
+    const series = buildSymptomSeverityDailySeries({
+      dayLogs,
+      episodes,
+      tz,
+      windowStart,
+      windowEnd,
+      role: "outcome",
+    });
+    expect(series.key).toBe(SYMPTOM_SEVERITY_CHANNEL_KEY);
+    expect(series.role).toBe("outcome");
+    const byDay = new Map(series.points.map((p) => [p.day, p.value]));
+    // Span days 01..05 present; logged days carry their impact, others 0.
+    expect(byDay.get("2026-03-01")).toBe(0);
+    expect(byDay.get("2026-03-02")).toBe(2);
+    expect(byDay.get("2026-03-03")).toBe(3);
+    expect(byDay.get("2026-03-04")).toBe(0);
+    expect(byDay.get("2026-03-05")).toBe(0);
+    // A day far outside the span is NOT fabricated.
+    expect(byDay.has("2026-02-15")).toBe(false);
+    // Genuine variance exists (0 ↔ >0), so the series is usable by Pearson.
+    const values = series.points.map((p) => p.value);
+    expect(Math.max(...values)).toBeGreaterThan(Math.min(...values));
+  });
+
+  it("degrades to an empty series when the user has no episodes", () => {
+    const series = buildSymptomSeverityDailySeries({
+      dayLogs: [],
+      episodes: [],
+      tz,
+      windowStart: new Date("2026-02-01T00:00:00Z"),
+      windowEnd: new Date("2026-03-31T00:00:00Z"),
+      role: "outcome",
+    });
+    expect(series.points).toHaveLength(0);
+  });
+
+  it("clamps an ongoing episode (null resolvedAt) to the window end", () => {
+    const windowStart = new Date("2026-03-01T00:00:00Z");
+    const windowEnd = new Date("2026-03-04T00:00:00Z");
+    const episodes: SymptomEpisodeSpan[] = [
+      { onsetAt: new Date("2026-03-02T08:00:00Z"), resolvedAt: null },
+    ];
+    const series = buildSymptomSeverityDailySeries({
+      dayLogs: [{ day: "2026-03-02", impact: 1 }],
+      episodes,
+      tz,
+      windowStart,
+      windowEnd,
+      role: "outcome",
+    });
+    const days = series.points.map((p) => p.day);
+    // Span clamps to windowEnd (03-04); no day past it is fabricated.
+    expect(days).toContain("2026-03-02");
+    expect(days).toContain("2026-03-04");
+    expect(days.every((d) => d <= "2026-03-04")).toBe(true);
+  });
+});
+
+describe("integration — built series flow through the discovery gates", () => {
+  const tz = "Europe/Berlin";
+
+  it("a sparse, thin-overlap compliance series produces NO confident driver", () => {
+    // Only ~8 days of compliance data: below the n ≥ 20 floor → withheld.
+    const rows: DoseHistoryRow[] = [];
+    for (let i = 0; i < 8; i++) {
+      const day = new Date(Date.UTC(2026, 2, 1 + i, 7, 0, 0));
+      rows.push(
+        slot(day.toISOString(), i % 2 === 0 ? "taken_on_time" : "missed"),
+      );
+    }
+    const compliance = buildComplianceDailySeries(rows, tz);
+
+    // A symptom outcome over the same thin span.
+    const episodes: SymptomEpisodeSpan[] = [
+      {
+        onsetAt: new Date("2026-03-01T08:00:00Z"),
+        resolvedAt: new Date("2026-03-09T08:00:00Z"),
+      },
+    ];
+    const symptom = buildSymptomSeverityDailySeries({
+      dayLogs: Array.from({ length: 8 }, (_, i) => ({
+        day: `2026-03-0${i + 1}`,
+        impact: i % 2 === 0 ? 0 : 2,
+      })),
+      episodes,
+      tz,
+      windowStart: new Date("2026-02-01T00:00:00Z"),
+      windowEnd: new Date("2026-03-31T00:00:00Z"),
+      role: "outcome",
+    });
+
+    const result = discoverCorrelations([compliance, symptom]);
+    expect(result.pairsTested).toBe(0);
+    expect(result.discovered).toHaveLength(0);
+  });
+
+  it("a sufficient adherence-dip → symptom-flare built series surfaces the link", () => {
+    // 50 days of daily compliance + a 50-day episode span with logged flares on
+    // low-adherence days → a discoverable next-day link.
+    const start = Date.UTC(2026, 0, 1, 7, 0, 0);
+    const rows: DoseHistoryRow[] = [];
+    const dayLogs: SymptomDayLogRow[] = [];
+    for (let i = 0; i < 50; i++) {
+      const at = new Date(start + i * MS_PER_DAY);
+      const low = i % 3 === 2; // every third day is a big adherence dip
+      rows.push(slot(at.toISOString(), low ? "missed" : "taken_on_time"));
+      // Symptom on day D+1 flares after a dip on day D.
+      const prevLow = i > 0 && (i - 1) % 3 === 2;
+      const dayKey = new Date(start + i * MS_PER_DAY)
+        .toISOString()
+        .slice(0, 10);
+      dayLogs.push({ day: dayKey, impact: prevLow ? 3 : 0 });
+    }
+    const compliance = buildComplianceDailySeries(rows, tz);
+    const symptom = buildSymptomSeverityDailySeries({
+      dayLogs,
+      episodes: [
+        {
+          onsetAt: new Date(start),
+          resolvedAt: new Date(start + 50 * MS_PER_DAY),
+        },
+      ],
+      tz,
+      windowStart: new Date(start - 5 * MS_PER_DAY),
+      windowEnd: new Date(start + 55 * MS_PER_DAY),
+      role: "outcome",
+    });
+
+    const result = discoverCorrelations([compliance, symptom]);
+    const pair = result.discovered.find(
+      (p) =>
+        p.behaviour === MEDICATION_COMPLIANCE_CHANNEL_KEY &&
+        p.outcome === SYMPTOM_SEVERITY_CHANNEL_KEY,
+    );
+    expect(pair).toBeDefined();
+    expect(pair!.n).toBeGreaterThanOrEqual(20);
+    expect(pair!.r).toBeLessThan(0); // higher adherence → lower next-day symptom
+    expect(pair!.interpretation).toMatch(/not a cause/);
+  });
+
+  it("the two built channels keep the never-causal framing", () => {
+    const series: NamedSeries[] = [
+      buildComplianceDailySeries(
+        Array.from({ length: 40 }, (_, i) =>
+          slot(
+            new Date(Date.UTC(2026, 0, 1 + i, 7)).toISOString(),
+            i % 4 === 0 ? "missed" : "taken_on_time",
+          ),
+        ),
+        tz,
+      ),
+    ];
+    // Pair against a vital with a clean linear lag so a driver surfaces.
+    const start = Date.UTC(2026, 0, 1);
+    series.push({
+      key: "RESTING_HEART_RATE",
+      role: "outcome",
+      points: Array.from({ length: 40 }, (_, i) => ({
+        day: new Date(start + i * MS_PER_DAY).toISOString().slice(0, 10),
+        value: 55 + (i > 0 && (i - 1) % 4 === 0 ? 8 : 0) + (i % 2) * 0.1,
+      })),
+    });
+    const result = discoverCorrelations(series);
+    for (const p of result.discovered) {
+      expect(p.interpretation).toMatch(/not a cause|never a cause/);
+    }
+  });
+});
diff --git a/src/lib/insights/correlation-discovery.ts b/src/lib/insights/correlation-discovery.ts
index 9ebc9cf0c..54c4d3f05 100644
--- a/src/lib/insights/correlation-discovery.ts
+++ b/src/lib/insights/correlation-discovery.ts
@@ -26,9 +26,17 @@
  * already-fetched daily series — the DB read lives in the route.
  *
  * Framing discipline: descriptive, never causal; every pair carries n, r,
- * p, and the BH-adjusted q; medication compliance is NOT yet a behaviour
- * channel (the cadence-aware per-day rate needs the compliance engine — a
- * later wave), documented here so the omission is intentional, not a gap.
+ * p, and the BH-adjusted q.
+ *
+ * v1.21.0 (FDREXTEND) — medication compliance (a daily adherence rate from the
+ * compliance engine's dose-history ledger) and symptom severity (the illness
+ * day-log functional-impact / symptom-burden track) are now first-class daily
+ * channels in the matrix, so the high-value "adherence dip → symptom flare" and
+ * "compliance↓ → a vital drifting" links can finally be discovered. They are
+ * the sparsest, noisiest inputs in the system — they flow through the SAME
+ * n ≥ 20 / p < 0.05 / BH-FDR / effect-size-floor / shrinkage gates as every
+ * other channel, so a thin series degrades to absent rather than to a spurious
+ * link. The series builders live in `correlation-series-builders.ts`.
  */
 import { pearson, MIN_PAIRED_N } from "@/lib/insights/correlations";
 
@@ -94,6 +102,14 @@ export function metricFamily(key: string): string {
   // tautology as MOOD→MOOD and is excluded too.
   if (key.startsWith(FACTOR_CHANNEL_PREFIX) || key === "MOOD") return "MOOD";
   if (key.startsWith("BLOOD_PRESSURE")) return "BLOOD_PRESSURE";
+  // v1.21.0 (FDREXTEND) — medication compliance and symptom severity each form
+  // their OWN single-channel family, so the loop's same-family guard collapses
+  // only the self-lag (compliance→compliance, symptom→symptom). The returned
+  // key equals the channel key for both, so neither shares a family with any
+  // vital / sleep / mood channel — they remain free to pair cross-domain
+  // (the whole point: adherence↓ → next-day symptom↑, or compliance↓ → a vital
+  // drifting). No special-case branch is needed; the `return key` fall-through
+  // already isolates them. This comment documents the deliberate decision.
   return key;
 }
 
@@ -286,6 +302,62 @@ function humanise(key: string): string {
 /** Namespace prefix for a RATED-mood-factor discovery channel (v1.14.0). */
 export const FACTOR_CHANNEL_PREFIX = "FACTOR:";
 
+/**
+ * v1.21.0 (FDREXTEND) — stable channel key for the daily medication-compliance
+ * adherence rate (per-day taken/scheduled, 0–100). Sourced from the compliance
+ * engine's unified dose-history ledger, NOT a `MeasurementType`, so the caller
+ * builds its series separately (the way MOOD is read from MoodEntry) and folds
+ * it in. A BEHAVIOUR channel: the actionable, high-value direction is
+ * "adherence dip today → a worse outcome tomorrow" (next-day symptom flare or a
+ * vital drifting), so compliance lags the outcome by a day like every other
+ * behaviour. It forms its own `metricFamily`, so the only pair the loop skips is
+ * the compliance→compliance self-lag.
+ */
+export const MEDICATION_COMPLIANCE_CHANNEL_KEY = "MEDICATION_COMPLIANCE";
+
+/**
+ * v1.21.0 (FDREXTEND) — stable channel key for the daily symptom-severity /
+ * functional-impact burden (0–3; 0 = healthy, 3 = bedbound). Sourced from the
+ * illness day-log (`functionalImpact`, else max linked symptom severity), NOT a
+ * `MeasurementType`. It rides BOTH roles like MOOD: as an OUTCOME it surfaces
+ * "adherence dip today → symptom flare tomorrow"; as a BEHAVIOUR it surfaces
+ * "symptom burden today → a vital drifting tomorrow". The same-family guard
+ * skips only the symptom→symptom self-lag. The series is built only across the
+ * span the user actually logs illness (healthy days inside that span = 0); a
+ * user who never logs illness yields an EMPTY series that degrades to absent —
+ * never a spurious all-zero constant that could fabricate a link.
+ */
+export const SYMPTOM_SEVERITY_CHANNEL_KEY = "SYMPTOM_SEVERITY";
+
+/**
+ * v1.21.0 (FDREXTEND) — discovery channels that are NOT `MeasurementType` enum
+ * values: each is backed by a different model (MOOD → MoodEntry,
+ * MEDICATION_COMPLIANCE → the dose-history ledger, SYMPTOM_SEVERITY → the
+ * illness day-log). EVERY caller that derives a `MeasurementType[]` list from
+ * `DISCOVERY_BEHAVIOURS` / `DISCOVERY_OUTCOMES` to feed a Prisma
+ * `measurement.findMany({ where: { type: { in } } })` MUST exclude these — a
+ * non-enum string in the `IN (...)` list errors the Postgres enum cast. Use
+ * {@link discoveryMeasurementTypes} (or this set) rather than re-spelling the
+ * `k !== "MOOD"` filter, so a future non-measurement channel cannot be missed at
+ * one call site and crash its query.
+ */
+export const NON_MEASUREMENT_DISCOVERY_CHANNELS: ReadonlySet<string> = new Set([
+  "MOOD",
+  MEDICATION_COMPLIANCE_CHANNEL_KEY,
+  SYMPTOM_SEVERITY_CHANNEL_KEY,
+]);
+
+/**
+ * v1.21.0 (FDREXTEND) — the subset of `keys` that ARE real `MeasurementType`
+ * enum values (i.e. excluding every {@link NON_MEASUREMENT_DISCOVERY_CHANNELS}
+ * channel), safe to splice into a Prisma `type IN (...)` filter. The cast is the
+ * caller's existing `as MeasurementType[]` assertion — this only drops the
+ * non-enum keys first.
+ */
+export function discoveryMeasurementTypes(keys: readonly string[]): string[] {
+  return keys.filter((k) => !NON_MEASUREMENT_DISCOVERY_CHANNELS.has(k));
+}
+
 /**
  * Run the FDR-controlled discovery over the behaviour × outcome matrix.
  *
@@ -382,9 +454,15 @@ export function discoverCorrelations(
 
 /**
  * The curated discovery matrix — the channels the engine pairs. Behaviours
- * (lag sources) on the left, outcomes (lag targets) on the right. Medication
- * compliance is deliberately NOT yet a behaviour channel — its cadence-aware
- * per-day rate needs the compliance engine; folding it in is a later wave.
+ * (lag sources) on the left, outcomes (lag targets) on the right.
+ *
+ * v1.21.0 (FDREXTEND) — medication compliance is NOW a behaviour channel (its
+ * cadence-aware per-day rate comes from the compliance engine's dose-history
+ * ledger; the caller builds the series and folds it in, the way MOOD is read
+ * from MoodEntry). Symptom severity rides both roles (see the OUTCOMES note).
+ * Both are sparse, noisy inputs — the engine's existing n ≥ 20 / p < 0.05 /
+ * BH-FDR / effect-size-floor / shrinkage gates apply UNCHANGED, so a thin
+ * compliance or symptom series cannot surface a confident driver.
  */
 export const DISCOVERY_BEHAVIOURS = [
   "TIME_IN_DAYLIGHT",
@@ -392,6 +470,12 @@ export const DISCOVERY_BEHAVIOURS = [
   "BLOOD_GLUCOSE",
   "BLOOD_PRESSURE_SYS",
   "ACTIVITY_STEPS",
+  // v1.21.0 (FDREXTEND) — daily adherence rate as a lag source: the high-value
+  // "adherence dip today → a worse outcome tomorrow" direction.
+  MEDICATION_COMPLIANCE_CHANNEL_KEY,
+  // v1.21.0 (FDREXTEND) — symptom burden as a lag source too: "more symptomatic
+  // today → a vital drifting tomorrow". Mirrored as an outcome below.
+  SYMPTOM_SEVERITY_CHANNEL_KEY,
 ] as const;
 
 export const DISCOVERY_OUTCOMES = [
@@ -406,6 +490,11 @@ export const DISCOVERY_OUTCOMES = [
   // to the existing "mood today → next-day outcome" direction. BH-FDR
   // already controls the larger pair family this opens up.
   "MOOD",
+  // v1.21.0 (FDREXTEND) — symptom severity as an OUTCOME: the flagship
+  // "adherence dip today → symptom flare tomorrow" link (compliance behaviour →
+  // symptom outcome). The same-family guard skips the symptom→symptom self-lag;
+  // BH-FDR controls the wider family the dual-role channel opens up.
+  SYMPTOM_SEVERITY_CHANNEL_KEY,
   // Wrist temperature is a credible future OUTCOME channel (near-daily, so
   // n ≥ 20 is reachable; "did a hard workout / late alcohol raise next-night
   // temperature?"), but it is deliberately NOT a channel yet: it is
diff --git a/src/lib/insights/correlation-series-builders.ts b/src/lib/insights/correlation-series-builders.ts
new file mode 100644
index 000000000..b387fa643
--- /dev/null
+++ b/src/lib/insights/correlation-series-builders.ts
@@ -0,0 +1,193 @@
+/**
+ * v1.21.0 (FDREXTEND) — daily-series builders for the two cross-metric channels
+ * the FDR correlation matrix could not previously see: medication compliance
+ * and symptom severity.
+ *
+ * These are the SPARSEST, noisiest inputs in the system, so the builders are
+ * deliberately conservative:
+ *
+ *  - **Compliance** is the per-day adherence rate (0–100) from the compliance
+ *    engine's unified dose-history ledger. Only days the cadence ACTUALLY
+ *    expected a dose produce a point (off-cadence / off-week days emit nothing),
+ *    so a sparse schedule never fabricates a 0%-or-100% point on a day it did
+ *    not dose. The ledger's `at` instant is re-keyed to the user's display tz
+ *    here (the engine's `dailyComplianceRatesFromLedger` keys in fixed Berlin),
+ *    so the day-key basis aligns with every other discovery series.
+ *
+ *  - **Symptom severity** is the illness day-log functional-impact / symptom
+ *    burden (0–3). The logged days are SPARSE and, on their own, often
+ *    constant (a short flare logged at impact 2 for three days is a flat line
+ *    with no variance — Pearson cannot use it). To make the actionable
+ *    "adherence dip → symptom flare" link discoverable we zero-fill HEALTHY
+ *    days, but ONLY across the span of the user's real episodes (onset →
+ *    resolved/window-end) intersected with the window. A user who never logs an
+ *    illness episode yields an EMPTY series, so the channel DEGRADES TO ABSENT
+ *    rather than to a spurious all-zero constant. Within an episode span, days
+ *    the user didn't log are treated as 0 (healthy) — the same constant-0
+ *    healthy baseline the recovery-gap symptom track already uses.
+ *
+ * Both series then flow UNCHANGED through `discoverCorrelations` — the n ≥ 20
+ * paired-day floor, the BH-FDR control, the effect-size floor, and the
+ * James-Stein shrinkage all apply exactly as they do to every vital channel.
+ * Nothing here computes a statistic; these are pure series shapers.
+ *
+ * Pure over already-fetched rows — the DB reads live in the caller (the route),
+ * mirroring how the engine itself is pure over `NamedSeries[]`.
+ */
+import { dayKeyForUserTz } from "@/lib/measurements/consolidation-tz";
+import type { DoseHistoryRow } from "@/lib/medications/scheduling/dose-history";
+import {
+  MEDICATION_COMPLIANCE_CHANNEL_KEY,
+  SYMPTOM_SEVERITY_CHANNEL_KEY,
+  type DailySeriesPoint,
+  type NamedSeries,
+} from "@/lib/insights/correlation-discovery";
+
+const MS_PER_DAY = 24 * 60 * 60 * 1000;
+
+/**
+ * Build the daily MEDICATION_COMPLIANCE behaviour series from the user's pooled
+ * dose-history ledger rows (every medication's `slot` rows over the window).
+ *
+ * One point per calendar day (user tz) that had at least one scheduled,
+ * resolved slot (`taken_on_time` / `taken_late` / `missed`). The rate is the
+ * day's pooled `taken / (taken + missed)`, 0–100 — the SAME numerator /
+ * denominator the window tally uses. `skipped` (deliberate), `upcoming` (window
+ * not open), and `ad_hoc` (off-schedule top-up) rows never enter the day's
+ * counts, exactly as the engine excludes them, so a day whose only rows are
+ * skips emits no point (no fabricated 0%).
+ *
+ * Returns a behaviour `NamedSeries`. When no day clears the slot test the
+ * `points` array is empty — the discovery loop then drops the channel (it
+ * cannot clear the n ≥ 20 floor), so the channel degrades to absent.
+ */
+export function buildComplianceDailySeries(
+  ledgerRows: DoseHistoryRow[],
+  tz: string,
+): NamedSeries {
+  const byDay = new Map<string, { taken: number; missed: number }>();
+  for (const row of ledgerRows) {
+    // Only scheduled slots have a defensible denominator (ad-hoc top-ups are
+    // excluded from the rate exactly as the ledger tally excludes them).
+    if (row.kind !== "slot") continue;
+    const isTaken =
+      row.status === "taken_on_time" || row.status === "taken_late";
+    const isMissed = row.status === "missed";
+    if (!isTaken && !isMissed) continue;
+
+    const day = dayKeyForUserTz(row.at, tz);
+    const bucket = byDay.get(day) ?? { taken: 0, missed: 0 };
+    if (isTaken) bucket.taken += 1;
+    else bucket.missed += 1;
+    byDay.set(day, bucket);
+  }
+
+  const points: DailySeriesPoint[] = [];
+  for (const [day, { taken, missed }] of byDay) {
+    const denom = taken + missed;
+    if (denom === 0) continue;
+    points.push({ day, value: Math.min(100, (taken / denom) * 100) });
+  }
+  points.sort((a, b) => (a.day < b.day ? -1 : a.day > b.day ? 1 : 0));
+  return {
+    key: MEDICATION_COMPLIANCE_CHANNEL_KEY,
+    role: "behaviour",
+    points,
+  };
+}
+
+/** A logged symptom-burden day (already keyed in the user's local tz). */
+export interface SymptomDayLogRow {
+  /** Stored `date` string — already a user-tz `YYYY-MM-DD` day key. */
+  day: string;
+  /** The day's burden (0–3): functionalImpact, else max linked severity. */
+  impact: number;
+}
+
+/** An episode's active span (instants), used to bound the healthy-day fill. */
+export interface SymptomEpisodeSpan {
+  onsetAt: Date;
+  /** NULL = ongoing → bounded by the window end at build time. */
+  resolvedAt: Date | null;
+}
+
+/** Inclusive `YYYY-MM-DD` day key for an instant in the user's tz. */
+function dayKey(at: Date, tz: string): string {
+  return dayKeyForUserTz(at, tz);
+}
+
+/**
+ * Build the daily SYMPTOM_SEVERITY series (rides both roles; this returns it in
+ * the requested `role`). Healthy days are zero-filled — but ONLY across the
+ * span of the user's real episodes intersected with `[windowStart, windowEnd]`,
+ * so a user with no episodes yields an EMPTY series (the channel degrades to
+ * absent, never a spurious all-zero constant).
+ *
+ * Algorithm:
+ *  1. Compute the set of in-window calendar days covered by ANY episode span
+ *     (onset → resolved, an ongoing episode clamped to `windowEnd`). This is
+ *     the only span where a "healthy = 0" claim is defensible: the user was in
+ *     a logging-relevant period.
+ *  2. Initialise every such day to 0 (healthy baseline).
+ *  3. Overlay the logged impacts (a day logged at impact k → k; multiple logs
+ *     on a day → the MAX, the most-symptomatic reading).
+ *
+ * The result is a dense-within-episode-spans series with genuine 0↔>0 variance
+ * when the user had symptomatic days, and NOTHING at all when they had no
+ * episodes. Pure.
+ */
+export function buildSymptomSeverityDailySeries(args: {
+  dayLogs: SymptomDayLogRow[];
+  episodes: SymptomEpisodeSpan[];
+  tz: string;
+  windowStart: Date;
+  windowEnd: Date;
+  role: "behaviour" | "outcome";
+}): NamedSeries {
+  const { dayLogs, episodes, tz, windowStart, windowEnd, role } = args;
+
+  const startKey = dayKey(windowStart, tz);
+  const endKey = dayKey(windowEnd, tz);
+
+  // Step 1+2 — zero-fill the healthy baseline across episode spans (clamped to
+  // the window). An episode with no in-window days contributes nothing.
+  const byDay = new Map<string, number>();
+  for (const ep of episodes) {
+    const epStart = ep.onsetAt.getTime();
+    const epEnd = (ep.resolvedAt ?? windowEnd).getTime();
+    // Clamp the iteration to the window so we never fabricate days outside it.
+    const from = Math.max(epStart, windowStart.getTime());
+    const to = Math.min(epEnd, windowEnd.getTime());
+    if (from > to) continue;
+    // Walk calendar days from `from` to `to`, keying each in the user's tz.
+    // Step by a day in ms; the tz-key collapses any DST hour drift to the
+    // right local day (we never index by the raw ms, only by the day key).
+    for (let t = from; t <= to + MS_PER_DAY; t += MS_PER_DAY) {
+      const key = dayKey(new Date(t), tz);
+      if (key < startKey || key > endKey) continue;
+      if (!byDay.has(key)) byDay.set(key, 0);
+      if (key === endKey) break;
+    }
+  }
+
+  // If no episode put a single day on the board, the channel is absent.
+  if (byDay.size === 0) {
+    return { key: SYMPTOM_SEVERITY_CHANNEL_KEY, role, points: [] };
+  }
+
+  // Step 3 — overlay logged impacts (MAX per day). A logged day outside every
+  // episode span is still honoured (it is, by definition, a symptomatic day the
+  // user recorded), so it joins the series even if the span walk missed it.
+  for (const log of dayLogs) {
+    if (log.day < startKey || log.day > endKey) continue;
+    if (!Number.isFinite(log.impact)) continue;
+    const prev = byDay.get(log.day);
+    byDay.set(log.day, prev == null ? log.impact : Math.max(prev, log.impact));
+  }
+
+  const points: DailySeriesPoint[] = [...byDay.entries()]
+    .map(([day, value]) => ({ day, value }))
+    .sort((a, b) => (a.day < b.day ? -1 : a.day > b.day ? 1 : 0));
+
+  return { key: SYMPTOM_SEVERITY_CHANNEL_KEY, role, points };
+}
diff --git a/src/lib/insights/metric-correlation-context.ts b/src/lib/insights/metric-correlation-context.ts
index f9b404cc9..2d18cd396 100644
--- a/src/lib/insights/metric-correlation-context.ts
+++ b/src/lib/insights/metric-correlation-context.ts
@@ -25,6 +25,7 @@ import { prisma } from "@/lib/db";
 import { wallClockInTz } from "@/lib/tz/wall-clock";
 import {
   discoverCorrelations,
+  discoveryMeasurementTypes,
   DISCOVERY_BEHAVIOURS,
   DISCOVERY_OUTCOMES,
   type DailySeriesPoint,
@@ -103,13 +104,17 @@ export async function getRelevantCorrelationsForMetric(
     const tz = profile?.timezone ?? "Europe/Berlin";
     const since = new Date(Date.now() - WINDOW_DAYS * MS_PER_DAY);
 
-    // MOOD is mood-entry backed, not a measurement type — strip it from the
-    // measurement query and source it separately, exactly like the route.
-    const behaviourTypes = DISCOVERY_BEHAVIOURS.filter(
-      (k) => k !== "MOOD",
+    // Non-measurement channels (MOOD, and v1.21.0 MEDICATION_COMPLIANCE /
+    // SYMPTOM_SEVERITY) are backed by other models — `discoveryMeasurementTypes`
+    // strips them from the measurement `type IN (...)` query (a non-enum string
+    // would error the cast). This per-metric-card surface does not populate the
+    // compliance / symptom channels (they degrade to absent here); the
+    // canonical `/api/insights/correlations` route builds them.
+    const behaviourTypes = discoveryMeasurementTypes(
+      DISCOVERY_BEHAVIOURS,
     ) as MeasurementType[];
-    const outcomeTypes = DISCOVERY_OUTCOMES.filter(
-      (k) => k !== "MOOD",
+    const outcomeTypes = discoveryMeasurementTypes(
+      DISCOVERY_OUTCOMES,
     ) as MeasurementType[];
 
     const [measurements, moodEntries] = await Promise.all([
diff --git a/src/lib/insights/narrative/period-narrative.ts b/src/lib/insights/narrative/period-narrative.ts
index 12f14a004..96ce3adc6 100644
--- a/src/lib/insights/narrative/period-narrative.ts
+++ b/src/lib/insights/narrative/period-narrative.ts
@@ -34,6 +34,7 @@ import { prisma } from "@/lib/db";
 import { wallClockInTz } from "@/lib/tz/wall-clock";
 import {
   discoverCorrelations,
+  discoveryMeasurementTypes,
   DISCOVERY_BEHAVIOURS,
   DISCOVERY_OUTCOMES,
   FACTOR_CHANNEL_PREFIX,
@@ -532,13 +533,19 @@ export async function buildPeriodNarrativeContext(
   );
 
   // The full set of types any beat needs: delta metrics ∪ banded vitals ∪
-  // discovery channels (minus MOOD, which is mood-entry backed).
+  // discovery channels (minus the NON-measurement channels: MOOD is mood-entry
+  // backed; v1.21.0 MEDICATION_COMPLIANCE / SYMPTOM_SEVERITY are
+  // ledger / illness-day-log backed — none are MeasurementType enum values, so
+  // `discoveryMeasurementTypes` drops them from the `type IN (...)` query).
+  // Those two channels are not populated on the period-narrative surface (they
+  // degrade to absent here); the canonical `/api/insights/correlations` route
+  // builds them.
   const measurementTypes = Array.from(
     new Set<string>([
       ...DELTA_METRICS.map((m) => m.type),
       ...VITALS_BASELINE_TYPES,
-      ...DISCOVERY_BEHAVIOURS.filter((k) => k !== "MOOD"),
-      ...DISCOVERY_OUTCOMES.filter((k) => k !== "MOOD"),
+      ...discoveryMeasurementTypes(DISCOVERY_BEHAVIOURS),
+      ...discoveryMeasurementTypes(DISCOVERY_OUTCOMES),
     ]),
   ) as MeasurementType[];
 
diff --git a/src/lib/insights/status-cache.ts b/src/lib/insights/status-cache.ts
index 62fe5e86e..2e309ba98 100644
--- a/src/lib/insights/status-cache.ts
+++ b/src/lib/insights/status-cache.ts
@@ -10,6 +10,7 @@ import {
 } from "@/lib/jobs/insight-status-generate-shared";
 import { hashInsightSnapshot } from "@/lib/insights/snapshot-hash";
 import {
+  discoveryMeasurementTypes,
   DISCOVERY_BEHAVIOURS,
   DISCOVERY_OUTCOMES,
 } from "@/lib/insights/correlation-discovery";
@@ -25,10 +26,19 @@ import { annotate } from "@/lib/logging/context";
  * relation would be silently skipped for the day. `MOOD` is mood-entry backed
  * (folded separately via `includeMood`), so it is excluded from the
  * measurement-type set here.
+ *
+ * v1.21.0 (FDREXTEND) — `MEDICATION_COMPLIANCE` (dose-history ledger) and
+ * `SYMPTOM_SEVERITY` (illness day-log) are likewise NON-measurement channels;
+ * `discoveryMeasurementTypes` excludes them too, or the `type IN (...)` groupBy
+ * below would try to cast a non-enum string to `MeasurementType` and error.
+ * Their own data changes still flip a card's gate through their source models —
+ * they simply do not belong in the measurement fingerprint set.
  */
-const CORRELATION_CHANNEL_TYPES: readonly MeasurementType[] = Array.from(
-  new Set<string>([...DISCOVERY_BEHAVIOURS, ...DISCOVERY_OUTCOMES]),
-).filter((key) => key !== "MOOD") as MeasurementType[];
+const CORRELATION_CHANNEL_TYPES: readonly MeasurementType[] =
+  discoveryMeasurementTypes([
+    ...DISCOVERY_BEHAVIOURS,
+    ...DISCOVERY_OUTCOMES,
+  ]) as MeasurementType[];
 
 /**
  * Shared cache-read for the seven `*-status.ts` insight generators.