diff --git a/src/app/api/auth/profile/route.ts b/src/app/api/auth/profile/route.ts
index 56bb228d8..62c806960 100644
--- a/src/app/api/auth/profile/route.ts
+++ b/src/app/api/auth/profile/route.ts
@@ -1,62 +1,30 @@
-import { prisma } from "@/lib/db";
-import { profileSchema } from "@/lib/validations/auth";
-import { auditLog } from "@/lib/auth/audit";
 import { apiSuccess, apiError, getClientIp, safeJson } from "@/lib/api-response";
 import { NextRequest } from "next/server";
 import { apiHandler, requireAuth } from "@/lib/api-handler";
 import { annotate } from "@/lib/logging/context";
+import { applyProfileUpdate } from "@/lib/auth/profile-update";
 
 export const PUT = apiHandler(async (request: NextRequest) => {
   const { user } = await requireAuth();
 
   const { data: body, error: jsonError } = await safeJson(request);
-
   if (jsonError) return jsonError;
-  const parsed = profileSchema.safeParse(body);
 
-  if (!parsed.success) {
-    return apiError(parsed.error.issues[0].message, 422);
+  const result = await applyProfileUpdate(user.id, body, getClientIp(request));
+  if (!result.ok) {
+    return apiError(result.message, result.status);
   }
 
-  const data = parsed.data;
-  const normalizedEmail = data.email ? data.email.trim().toLowerCase() : null;
-
-  if (data.email !== undefined && normalizedEmail) {
-    const existingUser = await prisma.user.findUnique({
-      where: { email: normalizedEmail },
-      select: { id: true },
-    });
-
-    if (existingUser && existingUser.id !== user.id) {
-      return apiError("Email already in use", 409);
-    }
-  }
-
-  const updatedUser = await prisma.user.update({
-    where: { id: user.id },
-    data: {
-      ...(data.email !== undefined ? { email: normalizedEmail } : {}),
-      heightCm: data.heightCm ?? null,
-      dateOfBirth: data.dateOfBirth ? new Date(data.dateOfBirth) : null,
-      ...(data.gender !== undefined ? { gender: data.gender } : {}),
-    },
-  });
-
-  await auditLog("profile.update", {
-    userId: updatedUser.id,
-    ipAddress: getClientIp(request),
-  });
-
   annotate({ action: { name: "auth.profile.update" } });
 
   return apiSuccess({
-    id: updatedUser.id,
-    username: updatedUser.username,
-    email: updatedUser.email,
-    role: updatedUser.role,
-    heightCm: updatedUser.heightCm,
-    dateOfBirth: updatedUser.dateOfBirth,
-    gender: updatedUser.gender,
-    timezone: updatedUser.timezone,
+    id: result.user.id,
+    username: result.user.username,
+    email: result.user.email,
+    role: result.user.role,
+    heightCm: result.user.heightCm,
+    dateOfBirth: result.user.dateOfBirth,
+    gender: result.user.gender,
+    timezone: result.user.timezone,
   });
 });
diff --git a/src/app/api/user/profile/__tests__/route.test.ts b/src/app/api/user/profile/__tests__/route.test.ts
new file mode 100644
index 000000000..af1d9078d
--- /dev/null
+++ b/src/app/api/user/profile/__tests__/route.test.ts
@@ -0,0 +1,131 @@
+import { describe, it, expect, vi, beforeEach } from "vitest";
+import { NextRequest } from "next/server";
+
+vi.mock("@/lib/db", () => ({
+  prisma: {
+    user: { findUnique: vi.fn(), update: vi.fn() },
+  },
+}));
+
+vi.mock("@/lib/auth/session", () => ({ getSession: vi.fn() }));
+
+vi.mock("@/lib/auth/audit", () => ({
+  auditLog: vi.fn().mockResolvedValue(undefined),
+}));
+
+vi.mock("@/lib/logging/transports", () => ({ emitIfSampled: vi.fn() }));
+
+vi.mock("@/lib/db-compat", () => ({
+  ensureDbCompatibility: vi.fn().mockResolvedValue(undefined),
+}));
+
+vi.mock("next/headers", () => ({
+  headers: vi.fn(async () => ({ get: () => null })),
+  cookies: vi.fn(async () => ({ get: () => undefined, set: () => {}, delete: () => {} })),
+}));
+
+import { GET, PATCH } from "../route";
+import { prisma } from "@/lib/db";
+import { getSession } from "@/lib/auth/session";
+
+const SESSION_OK = {
+  session: { id: "sess-1", expiresAt: new Date(Date.now() + 3_600_000) },
+  user: { id: "user-1", username: "marc", role: "USER" as const },
+};
+
+beforeEach(() => {
+  vi.resetAllMocks();
+});
+
+const callGet = GET as unknown as (req: NextRequest) => Promise<Response>;
+function makeGetReq(): NextRequest {
+  return new NextRequest("http://localhost/api/user/profile");
+}
+
+describe("GET /api/user/profile", () => {
+  it("returns 401 when unauthenticated", async () => {
+    vi.mocked(getSession).mockResolvedValue(null);
+    const res = await callGet(makeGetReq());
+    expect(res.status).toBe(401);
+  });
+
+  it("returns flattened iOS-style fields", async () => {
+    vi.mocked(getSession).mockResolvedValue(SESSION_OK as never);
+    vi.mocked(prisma.user.findUnique).mockResolvedValue({
+      username: "marc",
+      displayName: "Marc B.",
+      email: "marc@example.com",
+      dateOfBirth: new Date("1985-03-12T00:00:00.000Z"),
+      gender: "MALE",
+      heightCm: 180,
+      locale: "de",
+      timezone: "Europe/Berlin",
+    } as never);
+
+    const res = await callGet(makeGetReq());
+    expect(res.status).toBe(200);
+    const body = (await res.json()) as {
+      data: {
+        username: string;
+        displayName: string | null;
+        heightCm: number;
+        locale: string | null;
+      };
+    };
+    expect(body.data.username).toBe("marc");
+    expect(body.data.displayName).toBe("Marc B.");
+    expect(body.data.heightCm).toBe(180);
+    expect(body.data.locale).toBe("de");
+  });
+});
+
+describe("PATCH /api/user/profile", () => {
+  function req(body: unknown): NextRequest {
+    return new NextRequest("http://localhost/api/user/profile", {
+      method: "PATCH",
+      headers: { "content-type": "application/json" },
+      body: JSON.stringify(body),
+    });
+  }
+
+  it("returns 401 when unauthenticated", async () => {
+    vi.mocked(getSession).mockResolvedValue(null);
+    const res = await PATCH(req({ displayName: "Test" }));
+    expect(res.status).toBe(401);
+  });
+
+  it("returns 422 for invalid heightCm", async () => {
+    vi.mocked(getSession).mockResolvedValue(SESSION_OK as never);
+    const res = await PATCH(req({ heightCm: 9999 }));
+    expect(res.status).toBe(422);
+  });
+
+  it("persists displayName + locale via shared helper", async () => {
+    vi.mocked(getSession).mockResolvedValue(SESSION_OK as never);
+    vi.mocked(prisma.user.findUnique).mockResolvedValue(null);
+    vi.mocked(prisma.user.update).mockResolvedValue({
+      id: "user-1",
+      username: "marc",
+      displayName: "Marc B.",
+      email: null,
+      role: "USER",
+      heightCm: null,
+      dateOfBirth: null,
+      gender: null,
+      timezone: "Europe/Berlin",
+      locale: "de",
+    } as never);
+
+    const res = await PATCH(req({ displayName: "Marc B.", locale: "de" }));
+    expect(res.status).toBe(200);
+    expect(prisma.user.update).toHaveBeenCalledWith(
+      expect.objectContaining({
+        where: { id: "user-1" },
+        data: expect.objectContaining({
+          displayName: "Marc B.",
+          locale: "de",
+        }),
+      }),
+    );
+  });
+});
diff --git a/src/app/api/user/profile/route.ts b/src/app/api/user/profile/route.ts
new file mode 100644
index 000000000..6101276b2
--- /dev/null
+++ b/src/app/api/user/profile/route.ts
@@ -0,0 +1,71 @@
+/**
+ * iOS-friendly user profile endpoint.
+ *
+ * GET   → flattened profile fields (camelCase) for the native client.
+ *         Aliased over the same data exposed by `/api/auth/me`.
+ * PATCH → delegates to the shared `applyProfileUpdate` helper used by
+ *         `/api/auth/profile` PUT — same validation, same audit log.
+ */
+import { NextRequest } from "next/server";
+import { apiHandler, requireAuth } from "@/lib/api-handler";
+import { apiError, apiSuccess, getClientIp, safeJson } from "@/lib/api-response";
+import { annotate } from "@/lib/logging/context";
+import { applyProfileUpdate } from "@/lib/auth/profile-update";
+import { prisma } from "@/lib/db";
+
+export const dynamic = "force-dynamic";
+
+export const GET = apiHandler(async () => {
+  const { user } = await requireAuth();
+  annotate({ action: { name: "user.profile.get" } });
+
+  const dbUser = await prisma.user.findUnique({
+    where: { id: user.id },
+    select: {
+      username: true,
+      displayName: true,
+      email: true,
+      dateOfBirth: true,
+      gender: true,
+      heightCm: true,
+      locale: true,
+      timezone: true,
+    },
+  });
+
+  return apiSuccess({
+    username: dbUser?.username ?? user.username,
+    displayName: dbUser?.displayName ?? null,
+    email: dbUser?.email ?? null,
+    dateOfBirth: dbUser?.dateOfBirth?.toISOString() ?? null,
+    gender: dbUser?.gender ?? null,
+    heightCm: dbUser?.heightCm ?? null,
+    locale: dbUser?.locale ?? null,
+    timezone: dbUser?.timezone ?? "Europe/Berlin",
+  });
+});
+
+export const PATCH = apiHandler(async (request: NextRequest) => {
+  const { user } = await requireAuth();
+
+  const { data: body, error } = await safeJson(request);
+  if (error) return error;
+
+  const result = await applyProfileUpdate(user.id, body, getClientIp(request));
+  if (!result.ok) {
+    return apiError(result.message, result.status);
+  }
+
+  annotate({ action: { name: "user.profile.update" } });
+
+  return apiSuccess({
+    username: result.user.username,
+    displayName: result.user.displayName,
+    email: result.user.email,
+    dateOfBirth: result.user.dateOfBirth?.toISOString() ?? null,
+    gender: result.user.gender,
+    heightCm: result.user.heightCm,
+    locale: result.user.locale,
+    timezone: result.user.timezone,
+  });
+});
diff --git a/src/lib/auth/profile-update.ts b/src/lib/auth/profile-update.ts
new file mode 100644
index 000000000..03c0de7c3
--- /dev/null
+++ b/src/lib/auth/profile-update.ts
@@ -0,0 +1,114 @@
+/**
+ * Shared profile-update logic. The web client hits `/api/auth/profile` PUT
+ * and the iOS client hits `/api/user/profile` PATCH — both funnel through
+ * `applyProfileUpdate` so we don't fork the validation/audit path.
+ */
+import { prisma } from "@/lib/db";
+import { auditLog } from "@/lib/auth/audit";
+import { profileSchema } from "@/lib/validations/auth";
+import { z } from "zod/v4";
+
+const extendedProfileSchema = profileSchema.extend({
+  displayName: z.string().min(1).max(80).nullable().optional(),
+  locale: z.enum(["de", "en"]).nullable().optional(),
+  timezone: z.string().min(1).max(64).optional(),
+});
+
+export type ApplyProfileInput = z.infer<typeof extendedProfileSchema>;
+
+export interface ApplyProfileResult {
+  ok: true;
+  user: {
+    id: string;
+    username: string;
+    displayName: string | null;
+    email: string | null;
+    role: string;
+    heightCm: number | null;
+    dateOfBirth: Date | null;
+    gender: string | null;
+    timezone: string;
+    locale: string | null;
+  };
+}
+
+export interface ApplyProfileError {
+  ok: false;
+  status: number;
+  message: string;
+}
+
+/**
+ * Validate and persist profile updates for `userId`. Returns either an
+ * `ApplyProfileResult` on success or `ApplyProfileError` with a status
+ * code so callers can shape the wire response themselves.
+ */
+export async function applyProfileUpdate(
+  userId: string,
+  body: unknown,
+  ipAddress?: string | null,
+): Promise<ApplyProfileResult | ApplyProfileError> {
+  const parsed = extendedProfileSchema.safeParse(body);
+  if (!parsed.success) {
+    return {
+      ok: false,
+      status: 422,
+      message: parsed.error.issues[0]?.message ?? "Validation error",
+    };
+  }
+
+  const data = parsed.data;
+  const normalizedEmail = data.email ? data.email.trim().toLowerCase() : null;
+
+  if (data.email !== undefined && normalizedEmail) {
+    const existing = await prisma.user.findUnique({
+      where: { email: normalizedEmail },
+      select: { id: true },
+    });
+    if (existing && existing.id !== userId) {
+      return { ok: false, status: 409, message: "Email already in use" };
+    }
+  }
+
+  const updates: Record<string, unknown> = {};
+  if (data.email !== undefined) updates.email = normalizedEmail;
+  if (data.heightCm !== undefined) updates.heightCm = data.heightCm ?? null;
+  if (data.dateOfBirth !== undefined) {
+    updates.dateOfBirth = data.dateOfBirth ? new Date(data.dateOfBirth) : null;
+  }
+  if (data.gender !== undefined) updates.gender = data.gender;
+  if (data.displayName !== undefined) {
+    updates.displayName =
+      data.displayName === null || data.displayName === ""
+        ? null
+        : data.displayName.trim();
+  }
+  if (data.locale !== undefined) updates.locale = data.locale;
+  if (data.timezone !== undefined) updates.timezone = data.timezone;
+
+  const updatedUser = await prisma.user.update({
+    where: { id: userId },
+    data: updates,
+  });
+
+  await auditLog("profile.update", {
+    userId: updatedUser.id,
+    ipAddress: ipAddress ?? null,
+  });
+
+  return {
+    ok: true,
+    user: {
+      id: updatedUser.id,
+      username: updatedUser.username,
+      displayName: updatedUser.displayName,
+      email: updatedUser.email,
+      role: updatedUser.role,
+      heightCm: updatedUser.heightCm,
+      dateOfBirth: updatedUser.dateOfBirth,
+      gender: updatedUser.gender,
+      timezone: updatedUser.timezone,
+      locale: updatedUser.locale,
+    },
+  };
+}