diff --git a/prisma/migrations/0023_ios_adapters_idempotency_devices/migration.sql b/prisma/migrations/0023_ios_adapters_idempotency_devices/migration.sql
new file mode 100644
index 000000000..a3c1c9abf
--- /dev/null
+++ b/prisma/migrations/0023_ios_adapters_idempotency_devices/migration.sql
@@ -0,0 +1,55 @@
+-- v1.3: iOS adapter endpoints + idempotency cache + device registration
+--
+-- Purely additive:
+--   • users.display_name, users.healthkit_config_json, users.healthkit_last_synced_at
+--   • new tables: idempotency_keys, devices
+
+-- ── users new columns ─────────────────────────────────────────────────
+
+ALTER TABLE "users"
+  ADD COLUMN "display_name" TEXT,
+  ADD COLUMN "healthkit_config_json" JSONB,
+  ADD COLUMN "healthkit_last_synced_at" TIMESTAMP(3);
+
+-- ── idempotency_keys ──────────────────────────────────────────────────
+
+CREATE TABLE "idempotency_keys" (
+  "id"              TEXT PRIMARY KEY,
+  "user_id"         TEXT NOT NULL,
+  "key"             TEXT NOT NULL,
+  "method"          TEXT NOT NULL,
+  "path"            TEXT NOT NULL,
+  "response_status" INTEGER NOT NULL,
+  "response_body"   TEXT NOT NULL,
+  "expires_at"      TIMESTAMP(3) NOT NULL,
+  "created_at"      TIMESTAMP(3) NOT NULL DEFAULT CURRENT_TIMESTAMP,
+  CONSTRAINT "idempotency_keys_user_id_fkey"
+    FOREIGN KEY ("user_id") REFERENCES "users"("id") ON DELETE CASCADE
+);
+
+CREATE UNIQUE INDEX "idempotency_keys_user_id_key_method_path_key"
+  ON "idempotency_keys" ("user_id", "key", "method", "path");
+
+CREATE INDEX "idempotency_keys_expires_at_idx"
+  ON "idempotency_keys" ("expires_at");
+
+-- ── devices ───────────────────────────────────────────────────────────
+
+CREATE TABLE "devices" (
+  "id"          TEXT PRIMARY KEY,
+  "user_id"     TEXT NOT NULL,
+  "platform"    TEXT NOT NULL,
+  "token"       TEXT NOT NULL,
+  "bundle_id"   TEXT NOT NULL,
+  "locale"      TEXT,
+  "app_version" TEXT,
+  "model"       TEXT,
+  "last_seen"   TIMESTAMP(3) NOT NULL DEFAULT CURRENT_TIMESTAMP,
+  "created_at"  TIMESTAMP(3) NOT NULL DEFAULT CURRENT_TIMESTAMP,
+  "updated_at"  TIMESTAMP(3) NOT NULL,
+  CONSTRAINT "devices_user_id_fkey"
+    FOREIGN KEY ("user_id") REFERENCES "users"("id") ON DELETE CASCADE
+);
+
+CREATE UNIQUE INDEX "devices_token_key" ON "devices" ("token");
+CREATE INDEX "devices_user_id_idx" ON "devices" ("user_id");
diff --git a/prisma/schema.prisma b/prisma/schema.prisma
index 8768cf22d..52213ee66 100644
--- a/prisma/schema.prisma
+++ b/prisma/schema.prisma
@@ -74,6 +74,14 @@ model User {
   // Onboarding
   onboardingCompletedAt DateTime? @map("onboarding_completed_at")
 
+  // HealthKit (iOS) integration config — list of per-metric direction toggles.
+  // Shape: { entries: [{ id, kind, direction, enabled }], lastSyncedAt }
+  healthKitConfigJson Json?     @map("healthkit_config_json")
+  healthKitLastSyncedAt DateTime? @map("healthkit_last_synced_at")
+
+  // Display name (optional override of username for greetings).
+  displayName String? @map("display_name")
+
   // Relations
   passkeys    Passkey[]
   sessions    Session[]
@@ -90,6 +98,8 @@ model User {
   dataBackups          DataBackup[]
   achievements         UserAchievement[]
   feedback             Feedback[]
+  idempotencyKeys      IdempotencyKey[]
+  devices              Device[]
 
   @@map("users")
 }
@@ -559,6 +569,52 @@ model RateLimit {
   @@map("rate_limits")
 }
 
+// ─── Idempotency Keys (mobile-client replay protection) ──
+
+/// Caches the response of a POST/PUT/PATCH/DELETE request keyed by
+/// (userId, key, method, path) so retries within the TTL replay the
+/// original outcome instead of producing a duplicate side-effect.
+model IdempotencyKey {
+  id             String   @id @default(cuid())
+  userId         String   @map("user_id")
+  key            String
+  method         String
+  path           String
+  responseStatus Int      @map("response_status")
+  responseBody   String   @map("response_body") // serialized JSON envelope
+  expiresAt      DateTime @map("expires_at")
+  createdAt      DateTime @default(now()) @map("created_at")
+
+  user User @relation(fields: [userId], references: [id], onDelete: Cascade)
+
+  @@unique([userId, key, method, path])
+  @@index([expiresAt])
+  @@map("idempotency_keys")
+}
+
+// ─── Devices (APNs / mobile push targets) ────────────────
+
+/// Registered native-client device for push delivery. Token is unique
+/// across users; re-registering on a different account moves ownership.
+model Device {
+  id          String   @id @default(cuid())
+  userId      String   @map("user_id")
+  platform    String   // "ios"
+  token       String   @unique
+  bundleId    String   @map("bundle_id")
+  locale      String?
+  appVersion  String?  @map("app_version")
+  model       String?
+  lastSeen    DateTime @default(now()) @map("last_seen")
+  createdAt   DateTime @default(now()) @map("created_at")
+  updatedAt   DateTime @updatedAt @map("updated_at")
+
+  user User @relation(fields: [userId], references: [id], onDelete: Cascade)
+
+  @@index([userId])
+  @@map("devices")
+}
+
 // ─── User Achievements ───────────────────────────────────────
 
 model UserAchievement {