diff --git a/docs/api/openapi.yaml b/docs/api/openapi.yaml
index a45cb99dd..63dc3cdf8 100644
--- a/docs/api/openapi.yaml
+++ b/docs/api/openapi.yaml
@@ -1663,6 +1663,8 @@ components:
           type: integer
           minimum: 1
           maximum: 100
+        notificationsEnabled:
+          type: boolean
         startsOn:
           description: Date the medication course begins (ISO `YYYY-MM-DD`). Anchors RRULE BYDAY / BYMONTHDAY patterns and the
             rolling-interval countdown's first window. NULL = active from creation (the legacy implicit behaviour).
diff --git a/src/app/api/medications/route.ts b/src/app/api/medications/route.ts
index cc0dfdce8..dd599a02d 100644
--- a/src/app/api/medications/route.ts
+++ b/src/app/api/medications/route.ts
@@ -121,6 +121,7 @@ export const POST = apiHandler(async (request: NextRequest) => {
     category,
     treatmentClass,
     dosesPerUnit,
+    notificationsEnabled,
     schedules,
     startsOn,
     endsOn,
@@ -180,6 +181,10 @@ export const POST = apiHandler(async (request: NextRequest) => {
       // wire schema; Prisma fills the default GENERIC when omitted.
       ...(treatmentClass !== undefined && { treatmentClass }),
       ...(dosesPerUnit !== undefined && { dosesPerUnit }),
+      // v1.5 — wizard's reminders toggle now ships through the create
+      // payload (was orphaned in the initial diff). Prisma defaults to
+      // true when omitted, matching the legacy form's behaviour.
+      ...(notificationsEnabled !== undefined && { notificationsEnabled }),
       // v1.5 scheduling primitives — pass-through when supplied.
       ...(startsOn !== undefined && { startsOn }),
       ...(normalisedEndsOn !== undefined && { endsOn: normalisedEndsOn }),
diff --git a/src/lib/validations/medication.ts b/src/lib/validations/medication.ts
index e53e98b10..20ad7ebdc 100644
--- a/src/lib/validations/medication.ts
+++ b/src/lib/validations/medication.ts
@@ -143,6 +143,17 @@ export const scheduleSchema = z
       path: ["rrule"],
     },
   )
+  .refine(
+    (s) =>
+      s.rollingIntervalDays === undefined ||
+      s.rollingIntervalDays === null ||
+      !s.timesOfDay ||
+      s.timesOfDay.length <= 1,
+    {
+      message: "rolling-cadence schedules accept at most one time of day",
+      path: ["timesOfDay"],
+    },
+  )
   .meta({
     id: "MedicationScheduleInput",
     description:
@@ -203,9 +214,22 @@ export const createMedicationSchema = z
     treatmentClass: z.enum(MEDICATION_TREATMENT_CLASS_VALUES).optional(),
     /** v1.4.25 W4d — doses per pen/vial for inventory tracking. */
     dosesPerUnit: z.number().int().min(1).max(100).optional(),
+    notificationsEnabled: z.boolean().optional(),
     ...courseWindowFields,
     schedules: z.array(scheduleSchema).min(1, "Mindestens ein Zeitfenster"),
   })
+  .refine((b) => b.oneShot !== true || !!b.startsOn, {
+    message: "startsOn is required when oneShot is true",
+    path: ["startsOn"],
+  })
+  .refine(
+    (b) =>
+      !b.startsOn || !b.endsOn || b.endsOn.getTime() >= b.startsOn.getTime(),
+    {
+      message: "endsOn must be on or after startsOn",
+      path: ["endsOn"],
+    },
+  )
   .meta({
     id: "CreateMedicationRequest",
     description:
@@ -224,6 +248,18 @@ export const updateMedicationSchema = z
     ...courseWindowFields,
     schedules: z.array(scheduleSchema).optional(),
   })
+  .refine((b) => b.oneShot !== true || !!b.startsOn, {
+    message: "startsOn is required when oneShot is true",
+    path: ["startsOn"],
+  })
+  .refine(
+    (b) =>
+      !b.startsOn || !b.endsOn || b.endsOn.getTime() >= b.startsOn.getTime(),
+    {
+      message: "endsOn must be on or after startsOn",
+      path: ["endsOn"],
+    },
+  )
   .meta({
     id: "UpdateMedicationRequest",
     description: