diff --git a/src/app/api/measurement-reminders/[id]/satisfy/route.ts b/src/app/api/measurement-reminders/[id]/satisfy/route.ts
index 574a88edd..95233b768 100644
--- a/src/app/api/measurement-reminders/[id]/satisfy/route.ts
+++ b/src/app/api/measurement-reminders/[id]/satisfy/route.ts
@@ -13,10 +13,7 @@ import { auditLog } from "@/lib/auth/audit";
 import { apiHandler, requireAuth } from "@/lib/api-handler";
 import { apiSuccess, apiError, getClientIp } from "@/lib/api-response";
 import { annotate } from "@/lib/logging/context";
-import {
-  computeReminderNextDueAt,
-  type ReminderScheduleInput,
-} from "@/lib/measurement-reminders/scheduling";
+import { satisfyReminder } from "@/lib/measurement-reminders/satisfy";
 import { toMeasurementReminderDto } from "@/lib/measurement-reminders/dto";
 
 type RouteParams = { params: Promise<{ id: string }> };
@@ -42,19 +39,14 @@ export const POST = apiHandler(
     const timezone = userRow?.timezone || DEFAULT_TIMEZONE;
 
     const now = new Date();
-    const scheduleInput: ReminderScheduleInput = {
-      intervalDays: existing.intervalDays,
-      rrule: existing.rrule,
-      anchorDate: existing.anchorDate,
-      notifyHour: existing.notifyHour,
-      lastSatisfiedAt: now,
-      createdAt: existing.createdAt,
-    };
-    const nextDueAt = computeReminderNextDueAt(scheduleInput, timezone, now);
+    // The ONE shared satisfaction primitive — same code the cron
+    // auto-resolve and the eventful worker use. A manual "Erledigt" is
+    // always strictly after any prior satisfy, so the forward-only guard
+    // advances it.
+    await satisfyReminder(prisma, existing, timezone, now);
 
-    const updated = await prisma.measurementReminder.update({
+    const updated = await prisma.measurementReminder.findUniqueOrThrow({
       where: { id },
-      data: { lastSatisfiedAt: now, nextDueAt },
     });
 
     await auditLog("measurementReminder.satisfy", {
diff --git a/src/lib/jobs/measurement-reminder.ts b/src/lib/jobs/measurement-reminder.ts
index 230f398bb..0d960d838 100644
--- a/src/lib/jobs/measurement-reminder.ts
+++ b/src/lib/jobs/measurement-reminder.ts
@@ -42,6 +42,8 @@ import {
   computeReminderNextDueAt,
   type ReminderScheduleInput,
 } from "@/lib/measurement-reminders/scheduling";
+import { findSatisfyingEvent } from "@/lib/measurement-reminders/resolve";
+import { satisfyReminder } from "@/lib/measurement-reminders/satisfy";
 
 /**
  * v1.18.0 — map a reminder's `measurementType` to the toggleable module
@@ -137,17 +139,6 @@ export function buildMeasurementReminderPayload(
   return { title: t("measurementReminders.pushTitle"), body };
 }
 
-/**
- * The canonical sentinel measurement type the cron queries for
- * auto-resolve. BP is two rows (SYS + DIA); SYS is the "a BP was measured"
- * anchor (matching both would double-count).
- */
-function autoResolveQueryType(
-  reminderType: MeasurementType | null,
-): MeasurementType | null {
-  return reminderType;
-}
-
 /**
  * Run one Vorsorge-reminder cron tick. Iterates every live, enabled
  * reminder, auto-resolves the typed ones against incoming readings,
@@ -216,47 +207,27 @@ export async function runMeasurementReminderTick(
     try {
       const timezone = reminder.user.timezone || "Europe/Berlin";
 
-      // ── Auto-resolve from an incoming measurement ──────────────────
-      // Cheap guard, in the cron (not on the ingest path). Only typed
-      // reminders auto-resolve; free-text ones wait for a manual satisfy.
-      const queryType = autoResolveQueryType(reminder.measurementType);
-      if (queryType !== null) {
-        // Match readings logged AFTER the last satisfy (or, never
-        // satisfied, after the anchor). A reading inside the current due
-        // cycle means the user already measured — re-anchor + skip the
-        // nudge. `deletedAt: null` so a tombstoned reading never counts.
-        const sinceFloor =
-          reminder.lastSatisfiedAt ??
-          reminder.anchorDate ??
-          reminder.createdAt;
-        const match = await prisma.measurement.findFirst({
-          where: {
-            userId: reminder.user.id,
-            type: queryType,
-            deletedAt: null,
-            measuredAt: { gt: sinceFloor },
-          },
-          orderBy: { measuredAt: "desc" },
-          select: { measuredAt: true },
-        });
-        if (match) {
-          const scheduleInput: ReminderScheduleInput = {
-            intervalDays: reminder.intervalDays,
-            rrule: reminder.rrule,
-            anchorDate: reminder.anchorDate,
-            notifyHour: reminder.notifyHour,
-            lastSatisfiedAt: match.measuredAt,
-            createdAt: reminder.createdAt,
-          };
-          const nextDueAt = computeReminderNextDueAt(
-            scheduleInput,
-            timezone,
-            match.measuredAt,
-          );
-          await prisma.measurementReminder.update({
-            where: { id: reminder.id },
-            data: { lastSatisfiedAt: match.measuredAt, nextDueAt },
-          });
+      // ── Auto-resolve from an incoming event ────────────────────────
+      // Cheap safety-net poll, in the cron (the eventful `reminder-satisfy`
+      // worker is the fast path). A typed reminder resolves from a matching
+      // Measurement; a free-text reminder resolves from a LabResult (the
+      // Lab↔Vorsorge link). Both go through the shared `findSatisfyingEvent`
+      // + `satisfyReminder` primitives so the cron and the worker can never
+      // diverge. A reading inside the current due cycle means the user
+      // already measured — re-anchor + skip the nudge.
+      const satisfiedAt = await findSatisfyingEvent(
+        prisma,
+        reminder.user.id,
+        reminder,
+      );
+      if (satisfiedAt) {
+        const result = await satisfyReminder(
+          prisma,
+          reminder,
+          timezone,
+          satisfiedAt,
+        );
+        if (result.satisfied) {
           summary.autoResolved += 1;
           continue;
         }
@@ -360,6 +331,105 @@ export async function runMeasurementReminderTick(
   return summary;
 }
 
+export interface ReminderSatisfySummary {
+  candidatesScanned: number;
+  satisfied: number;
+  skippedModuleDisabled: number;
+  skippedNoEvent: number;
+  failed: number;
+}
+
+/**
+ * v1.18.1 — eventful satisfaction for one user. Called by the
+ * `reminder-satisfy` worker right after a measurement / lab write lands
+ * (from any ingest path: manual create, batch, or a device sync). The
+ * 15-min cron remains the idempotent safety-net behind this.
+ *
+ * Loads the user's live, enabled reminders that could auto-resolve (typed
+ * → a Measurement; free-text → a LabResult), and for each runs the SAME
+ * `findSatisfyingEvent` + `satisfyReminder` primitives the cron uses, so
+ * "I just weighed myself, stop reminding me" resolves immediately instead
+ * of waiting up to 15 minutes.
+ *
+ * Respects the module toggle: a reminder whose measurement type belongs to
+ * a disabled module produces no engine activity (the same gate the cron
+ * dispatch applies). Forward-only `satisfyReminder` makes a duplicate
+ * enqueue + the trailing cron poll converge without double-stamping.
+ */
+export async function runReminderSatisfyForUser(
+  prisma: PrismaClient,
+  userId: string,
+  now: Date,
+  options: { isModuleEnabled?: typeof isModuleEnabled } = {},
+): Promise<ReminderSatisfySummary> {
+  void now;
+  const moduleGate = options.isModuleEnabled ?? isModuleEnabled;
+
+  const summary: ReminderSatisfySummary = {
+    candidatesScanned: 0,
+    satisfied: 0,
+    skippedModuleDisabled: 0,
+    skippedNoEvent: 0,
+    failed: 0,
+  };
+
+  const user = await prisma.user.findUnique({
+    where: { id: userId },
+    select: { timezone: true },
+  });
+  const timezone = user?.timezone || "Europe/Berlin";
+
+  const reminders = await prisma.measurementReminder.findMany({
+    where: { userId, deletedAt: null, enabled: true },
+  });
+
+  for (const reminder of reminders) {
+    summary.candidatesScanned += 1;
+    try {
+      // Module toggle — no engine activity for a reminder whose type
+      // belongs to a disabled module. Core-vital + free-text reminders map
+      // to no module and are never gated.
+      const gatedModule = moduleForMeasurementType(reminder.measurementType);
+      if (
+        gatedModule !== null &&
+        !(await moduleGate(userId, gatedModule))
+      ) {
+        summary.skippedModuleDisabled += 1;
+        continue;
+      }
+
+      const satisfiedAt = await findSatisfyingEvent(prisma, userId, reminder);
+      if (!satisfiedAt) {
+        summary.skippedNoEvent += 1;
+        continue;
+      }
+
+      const result = await satisfyReminder(
+        prisma,
+        reminder,
+        timezone,
+        satisfiedAt,
+      );
+      if (result.satisfied) {
+        summary.satisfied += 1;
+        getEvent()?.addMeta("measurement_reminder.satisfied_eventful", reminder.id);
+      } else {
+        // Forward-only no-op — the cron or a prior enqueue already
+        // advanced this row past the event.
+        summary.skippedNoEvent += 1;
+      }
+    } catch (err: unknown) {
+      summary.failed += 1;
+      const message = err instanceof Error ? err.message : String(err);
+      getEvent()?.addWarning(
+        `reminder-satisfy per-reminder resolve failed for ${reminder.id}: ${message}`,
+      );
+    }
+  }
+
+  return summary;
+}
+
 /**
  * Advance `nextDueAt` to the next occurrence strictly after `now`. Used
  * after a successful dispatch (and after a client-managed skip) as the
diff --git a/src/lib/measurement-reminders/__tests__/resolve.test.ts b/src/lib/measurement-reminders/__tests__/resolve.test.ts
new file mode 100644
index 000000000..1ef49016b
--- /dev/null
+++ b/src/lib/measurement-reminders/__tests__/resolve.test.ts
@@ -0,0 +1,112 @@
+/**
+ * v1.18.1 — `findSatisfyingEvent`: the shared "did a satisfying event
+ * land?" matcher. A typed reminder resolves from a Measurement; a
+ * free-text reminder resolves from a LabResult (the Lab↔Vorsorge link, D2).
+ */
+import { describe, expect, it, vi } from "vitest";
+
+import { findSatisfyingEvent, satisfactionFloor } from "../resolve";
+
+type FindFirstArgs = { where: Record<string, unknown> };
+
+function makePrisma(opts: {
+  measurement?: { measuredAt: Date } | null;
+  lab?: { takenAt: Date } | null;
+}) {
+  return {
+    measurement: {
+      findFirst: vi.fn((args: FindFirstArgs) => {
+        void args;
+        return Promise.resolve(opts.measurement ?? null);
+      }),
+    },
+    labResult: {
+      findFirst: vi.fn((args: FindFirstArgs) => {
+        void args;
+        return Promise.resolve(opts.lab ?? null);
+      }),
+    },
+  };
+}
+
+const base = {
+  measurementType: null,
+  anchorDate: null,
+  lastSatisfiedAt: null,
+  createdAt: new Date("2026-06-01T00:00:00Z"),
+} as const;
+
+describe("satisfactionFloor", () => {
+  it("prefers lastSatisfiedAt, then anchorDate, then createdAt", () => {
+    const last = new Date("2026-06-10T00:00:00Z");
+    const anchor = new Date("2026-06-05T00:00:00Z");
+    expect(
+      satisfactionFloor({ ...base, lastSatisfiedAt: last, anchorDate: anchor }),
+    ).toEqual(last);
+    expect(satisfactionFloor({ ...base, anchorDate: anchor })).toEqual(anchor);
+    expect(satisfactionFloor(base)).toEqual(base.createdAt);
+  });
+});
+
+describe("findSatisfyingEvent", () => {
+  it("resolves a typed reminder from a matching Measurement, not a lab", async () => {
+    const measuredAt = new Date("2026-06-14T18:00:00Z");
+    const prisma = makePrisma({ measurement: { measuredAt }, lab: { takenAt: new Date() } });
+
+    const at = await findSatisfyingEvent(prisma as never, "u1", {
+      ...base,
+      measurementType: "WEIGHT",
+    });
+
+    expect(at).toEqual(measuredAt);
+    expect(prisma.measurement.findFirst).toHaveBeenCalledTimes(1);
+    expect(prisma.labResult.findFirst).not.toHaveBeenCalled();
+    // Queries the right type, non-deleted, after the floor.
+    const where = prisma.measurement.findFirst.mock.calls[0]![0].where as {
+      type: string;
+      deletedAt: null;
+      measuredAt: { gt: Date };
+    };
+    expect(where.type).toBe("WEIGHT");
+    expect(where.deletedAt).toBeNull();
+    expect(where.measuredAt.gt).toEqual(base.createdAt);
+  });
+
+  it("returns null for a typed reminder with no matching reading", async () => {
+    const prisma = makePrisma({ measurement: null });
+    const at = await findSatisfyingEvent(prisma as never, "u1", {
+      ...base,
+      measurementType: "BLOOD_PRESSURE_SYS",
+    });
+    expect(at).toBeNull();
+  });
+
+  it("resolves a free-text reminder from any LabResult (D2)", async () => {
+    const takenAt = new Date("2026-06-15T09:00:00Z");
+    const prisma = makePrisma({ lab: { takenAt } });
+
+    const at = await findSatisfyingEvent(prisma as never, "u1", {
+      ...base,
+      measurementType: null,
+    });
+
+    expect(at).toEqual(takenAt);
+    expect(prisma.labResult.findFirst).toHaveBeenCalledTimes(1);
+    expect(prisma.measurement.findFirst).not.toHaveBeenCalled();
+    const where = prisma.labResult.findFirst.mock.calls[0]![0].where as {
+      deletedAt: null;
+      takenAt: { gt: Date };
+    };
+    expect(where.deletedAt).toBeNull();
+    expect(where.takenAt.gt).toEqual(base.createdAt);
+  });
+
+  it("returns null for a free-text reminder with no lab landed", async () => {
+    const prisma = makePrisma({ lab: null });
+    const at = await findSatisfyingEvent(prisma as never, "u1", {
+      ...base,
+      measurementType: null,
+    });
+    expect(at).toBeNull();
+  });
+});
diff --git a/src/lib/measurement-reminders/__tests__/satisfy.test.ts b/src/lib/measurement-reminders/__tests__/satisfy.test.ts
new file mode 100644
index 000000000..8fdcec82f
--- /dev/null
+++ b/src/lib/measurement-reminders/__tests__/satisfy.test.ts
@@ -0,0 +1,117 @@
+/**
+ * v1.18.1 — the shared `satisfyReminder` primitive: forward-only guard +
+ * re-anchored reschedule. The cron, the manual satisfy route, and the
+ * eventful worker all route through it, so these tests pin the invariants
+ * every caller relies on.
+ */
+import { describe, expect, it, vi } from "vitest";
+
+import { satisfyReminder } from "../satisfy";
+
+const TZ = "Europe/Berlin";
+
+function makePrisma() {
+  const updates: Array<{ id: string; data: Record<string, unknown> }> = [];
+  const prisma = {
+    measurementReminder: {
+      update: vi.fn(
+        async ({
+          where,
+          data,
+        }: {
+          where: { id: string };
+          data: Record<string, unknown>;
+        }) => {
+          updates.push({ id: where.id, data });
+          return { id: where.id, ...data };
+        },
+      ),
+    },
+  };
+  return { prisma, updates };
+}
+
+function reminder(overrides: Partial<Parameters<typeof satisfyReminder>[1]> = {}) {
+  return {
+    id: "r1",
+    intervalDays: 7,
+    rrule: null,
+    anchorDate: null,
+    notifyHour: 9,
+    lastSatisfiedAt: null,
+    createdAt: new Date("2026-06-01T00:00:00Z"),
+    ...overrides,
+  };
+}
+
+describe("satisfyReminder", () => {
+  it("stamps lastSatisfiedAt + recomputes nextDueAt when never satisfied", async () => {
+    const { prisma, updates } = makePrisma();
+    const at = new Date("2026-06-14T18:00:00Z");
+
+    const result = await satisfyReminder(
+      prisma as never,
+      reminder(),
+      TZ,
+      at,
+    );
+
+    expect(result.satisfied).toBe(true);
+    expect(result.nextDueAt).toBeInstanceOf(Date);
+    expect(updates).toHaveLength(1);
+    expect(updates[0].data.lastSatisfiedAt).toEqual(at);
+    // Rolling +7d from the satisfy instant — strictly in the future.
+    expect((updates[0].data.nextDueAt as Date).getTime()).toBeGreaterThan(
+      at.getTime(),
+    );
+  });
+
+  it("advances when the event is strictly after the existing lastSatisfiedAt", async () => {
+    const { prisma, updates } = makePrisma();
+    const prev = new Date("2026-06-10T08:00:00Z");
+    const at = new Date("2026-06-17T08:00:00Z");
+
+    const result = await satisfyReminder(
+      prisma as never,
+      reminder({ lastSatisfiedAt: prev }),
+      TZ,
+      at,
+    );
+
+    expect(result.satisfied).toBe(true);
+    expect(updates[0].data.lastSatisfiedAt).toEqual(at);
+  });
+
+  it("is a forward-only no-op when the event is older than lastSatisfiedAt", async () => {
+    const { prisma, updates } = makePrisma();
+    const prev = new Date("2026-06-17T08:00:00Z");
+    const stale = new Date("2026-06-10T08:00:00Z");
+
+    const result = await satisfyReminder(
+      prisma as never,
+      reminder({ lastSatisfiedAt: prev }),
+      TZ,
+      stale,
+    );
+
+    expect(result.satisfied).toBe(false);
+    expect(result.nextDueAt).toBeNull();
+    expect(prisma.measurementReminder.update).not.toHaveBeenCalled();
+    expect(updates).toHaveLength(0);
+  });
+
+  it("is a no-op when the event equals lastSatisfiedAt (cron behind an applied hook)", async () => {
+    const { prisma } = makePrisma();
+    const same = new Date("2026-06-17T08:00:00Z");
+
+    const result = await satisfyReminder(
+      prisma as never,
+      reminder({ lastSatisfiedAt: same }),
+      TZ,
+      same,
+    );
+
+    expect(result.satisfied).toBe(false);
+    expect(prisma.measurementReminder.update).not.toHaveBeenCalled();
+  });
+});
diff --git a/src/lib/measurement-reminders/resolve.ts b/src/lib/measurement-reminders/resolve.ts
new file mode 100644
index 000000000..cc04cc7f3
--- /dev/null
+++ b/src/lib/measurement-reminders/resolve.ts
@@ -0,0 +1,83 @@
+/**
+ * v1.18.1 — the shared "did a satisfying event land?" matcher for the
+ * Vorsorge engine.
+ *
+ * One reminder, one question: since the last satisfy (or the anchor when
+ * never satisfied), did a reading land that fulfils this reminder's
+ * cadence? Both the 15-min cron and the eventful ingest-driven worker call
+ * this, so the suppression logic lives in exactly one place.
+ *
+ * Two satisfaction sources:
+ *
+ *   1. **Typed reminder** (`measurementType` non-NULL): a non-deleted
+ *      `Measurement` of that type measured after the floor. BP matches on
+ *      `BLOOD_PRESSURE_SYS` (the SYS sentinel) so SYS + DIA don't
+ *      double-count — the validation allow-list only ever stores SYS.
+ *   2. **Free-text reminder** (`measurementType` NULL): an "annual blood
+ *      panel" / lab Vorsorge has no Measurement to match. v1.18.1 closes
+ *      the clinical loop (gap D2): a non-deleted `LabResult` taken after
+ *      the floor satisfies it. Without this a lab reminder could only ever
+ *      resolve on a manual "Erledigt".
+ */
+import type { PrismaClient } from "@/generated/prisma/client";
+
+/** The reminder fields the matcher reads. */
+export interface ResolvableReminder {
+  measurementType: import("@/generated/prisma/client").MeasurementType | null;
+  anchorDate: Date | null;
+  lastSatisfiedAt: Date | null;
+  createdAt: Date;
+}
+
+/**
+ * The floor a satisfying event must land strictly after: the last satisfy,
+ * else the anchor, else the create instant. A reading inside the current
+ * due cycle means the user already measured.
+ */
+export function satisfactionFloor(reminder: ResolvableReminder): Date {
+  return reminder.lastSatisfiedAt ?? reminder.anchorDate ?? reminder.createdAt;
+}
+
+/**
+ * Find the most recent satisfying event instant for a reminder, or `null`
+ * when none has landed since the floor.
+ *
+ * A typed reminder resolves from a matching `Measurement`; a free-text
+ * reminder resolves from any `LabResult` (the Lab↔Vorsorge link, D2).
+ */
+export async function findSatisfyingEvent(
+  prisma: PrismaClient,
+  userId: string,
+  reminder: ResolvableReminder,
+): Promise<Date | null> {
+  const floor = satisfactionFloor(reminder);
+
+  if (reminder.measurementType !== null) {
+    const match = await prisma.measurement.findFirst({
+      where: {
+        userId,
+        type: reminder.measurementType,
+        deletedAt: null,
+        measuredAt: { gt: floor },
+      },
+      orderBy: { measuredAt: "desc" },
+      select: { measuredAt: true },
+    });
+    return match?.measuredAt ?? null;
+  }
+
+  // Free-text / checklist reminder → a lab panel fulfils it. Match on
+  // `takenAt` (the sample instant), mirroring the measurement path's
+  // `measuredAt`. Any analyte counts: a "Großes Blutbild" reminder is
+  // satisfied the moment the user records any value from that panel.
+  const lab = await prisma.labResult.findFirst({
+    where: {
+      userId,
+      deletedAt: null,
+      takenAt: { gt: floor },
+    },
+    orderBy: { takenAt: "desc" },
+    select: { takenAt: true },
+  });
+  return lab?.takenAt ?? null;
+}
diff --git a/src/lib/measurement-reminders/satisfy.ts b/src/lib/measurement-reminders/satisfy.ts
new file mode 100644
index 000000000..d0fd8ce43
--- /dev/null
+++ b/src/lib/measurement-reminders/satisfy.ts
@@ -0,0 +1,101 @@
+/**
+ * v1.18.1 — the ONE shared satisfaction primitive for the Vorsorge /
+ * measurement-reminder engine.
+ *
+ * Every path that marks a reminder's cadence fulfilled routes through
+ * `satisfyReminder`: the manual "Erledigt" route, the cron auto-resolve,
+ * and the eventful ingest-driven satisfaction worker. No duplicated
+ * reschedule logic — one place stamps `lastSatisfiedAt` and recomputes the
+ * server-authoritative `nextDueAt`.
+ *
+ * Two invariants the primitive owns:
+ *
+ *   1. **Forward-only.** `lastSatisfiedAt` only ever moves forward. A
+ *      cron poll and an ingest enqueue can both fire for the same reading;
+ *      the second is a no-op (returns `false`) rather than re-stamping an
+ *      older instant. This is what makes the cron a safe idempotent
+ *      safety-net behind the eventful hook.
+ *   2. **Re-anchored reschedule.** `nextDueAt` is recomputed from the
+ *      satisfy instant via the canonical recurrence engine
+ *      (`computeReminderNextDueAt`), so a freshly-satisfied reminder rolls
+ *      strictly past the current due cycle and the self-tracker never gets
+ *      nagged.
+ *
+ * Pure-ish: it reads the row fields it is handed and issues one Prisma
+ * update. The caller supplies the reminder row + the user's timezone.
+ */
+import type { PrismaClient } from "@/generated/prisma/client";
+import {
+  computeReminderNextDueAt,
+  type ReminderScheduleInput,
+} from "@/lib/measurement-reminders/scheduling";
+
+/**
+ * The reminder fields `satisfyReminder` needs. A subset of the Prisma row
+ * so callers (and tests) can construct it without the full model.
+ */
+export interface SatisfiableReminder {
+  id: string;
+  intervalDays: number | null;
+  rrule: string | null;
+  anchorDate: Date | null;
+  notifyHour: number;
+  lastSatisfiedAt: Date | null;
+  createdAt: Date;
+}
+
+export interface SatisfyResult {
+  /** True when the reminder was advanced; false when the event was older
+   *  than (or equal to) the existing `lastSatisfiedAt` (forward-only
+   *  no-op). */
+  satisfied: boolean;
+  /** The recomputed next-due instant when satisfied, else `null`. */
+  nextDueAt: Date | null;
+}
+
+/**
+ * Mark a reminder's cadence satisfied at `satisfiedAt` and reschedule.
+ *
+ * Forward-only: if `satisfiedAt` is not strictly after the existing
+ * `lastSatisfiedAt`, nothing is written and `{ satisfied: false }` is
+ * returned. Otherwise stamps `lastSatisfiedAt = satisfiedAt`, recomputes
+ * `nextDueAt` from the satisfy instant, persists both, and returns
+ * `{ satisfied: true, nextDueAt }`.
+ */
+export async function satisfyReminder(
+  prisma: PrismaClient,
+  reminder: SatisfiableReminder,
+  timezone: string,
+  satisfiedAt: Date,
+): Promise<SatisfyResult> {
+  // Forward-only guard. A null `lastSatisfiedAt` always advances. Equal
+  // instants are a no-op so a cron poll behind an already-applied ingest
+  // hook doesn't churn the row.
+  if (
+    reminder.lastSatisfiedAt !== null &&
+    satisfiedAt.getTime() <= reminder.lastSatisfiedAt.getTime()
+  ) {
+    return { satisfied: false, nextDueAt: null };
+  }
+
+  const scheduleInput: ReminderScheduleInput = {
+    intervalDays: reminder.intervalDays,
+    rrule: reminder.rrule,
+    anchorDate: reminder.anchorDate,
+    notifyHour: reminder.notifyHour,
+    lastSatisfiedAt: satisfiedAt,
+    createdAt: reminder.createdAt,
+  };
+  const nextDueAt = computeReminderNextDueAt(
+    scheduleInput,
+    timezone,
+    satisfiedAt,
+  );
+
+  await prisma.measurementReminder.update({
+    where: { id: reminder.id },
+    data: { lastSatisfiedAt: satisfiedAt, nextDueAt },
+  });
+
+  return { satisfied: true, nextDueAt };
+}