diff --git a/packages/api/src/lib/handle.ts b/packages/api/src/lib/handle.ts
index b3f6c57..7617cda 100644
--- a/packages/api/src/lib/handle.ts
+++ b/packages/api/src/lib/handle.ts
@@ -96,3 +96,39 @@ export function validateUsername(raw: string): UsernameValidation {
   }
   return { ok: true, value };
 }
+
+/**
+ * Wandelt den anzeigefertigen Handle in eine URL-taugliche Form um:
+ * "KochHeld#A12B" -> "KochHeld-A12B". Das '#' ist als URL-Fragment-Zeichen
+ * nicht im Pfad nutzbar, daher der Bindestrich als Trenner.
+ */
+export function handleToSlug(
+  username: string | null | undefined,
+  discriminator: string | null | undefined,
+): string | null {
+  if (!username || !discriminator) return null;
+  return `${username}-${discriminator}`;
+}
+
+/**
+ * Zerlegt einen URL-Slug ("KochHeld-A12B") zurück in Username + Discriminator.
+ * Es wird am LETZTEN Bindestrich getrennt, weil der Username selbst Bindestriche
+ * enthalten darf. Gibt null zurück, wenn der Slug keine gültige Form hat.
+ */
+export function parseHandleSlug(
+  slug: string,
+): { username: string; discriminator: string } | null {
+  const trimmed = slug.trim();
+  const lastDash = trimmed.lastIndexOf("-");
+  if (lastDash <= 0 || lastDash === trimmed.length - 1) return null;
+
+  const username = trimmed.slice(0, lastDash);
+  const discriminator = trimmed.slice(lastDash + 1).toUpperCase();
+
+  if (validateUsername(username).ok !== true) return null;
+  if (discriminator.length !== DISCRIMINATOR_LENGTH) return null;
+  for (const ch of discriminator) {
+    if (!DISCRIMINATOR_ALPHABET.includes(ch)) return null;
+  }
+  return { username, discriminator };
+}
diff --git a/packages/api/src/trpc/handle.test.ts b/packages/api/src/trpc/handle.test.ts
index 5c41f95..e945d15 100644
--- a/packages/api/src/trpc/handle.test.ts
+++ b/packages/api/src/trpc/handle.test.ts
@@ -7,6 +7,8 @@ import {
   formatHandle,
   generateDiscriminator,
   generateUniqueDiscriminator,
+  handleToSlug,
+  parseHandleSlug,
   validateUsername,
 } from "../lib/handle";
 
@@ -65,11 +67,11 @@ test("generateUniqueDiscriminator wirft, wenn nach maxAttempts kein freier gefun
 });
 
 test("formatHandle baut Username#Discriminator", () => {
-  assert.equal(formatHandle("Held", "A12B"), "Held#A12B");
+  assert.equal(formatHandle("Held", "A23B"), "Held#A23B");
 });
 
 test("formatHandle liefert null ohne Username", () => {
-  assert.equal(formatHandle(null, "A12B"), null);
+  assert.equal(formatHandle(null, "A23B"), null);
 });
 
 test("formatHandle liefert null ohne Discriminator", () => {
@@ -100,3 +102,50 @@ test("validateUsername lehnt Umlaute ab (Handle bleibt URL-tauglich)", () => {
 test("Bio-Limit ist 280", () => {
   assert.equal(BIO_MAX_LENGTH, 280);
 });
+
+test("handleToSlug baut Username-Discriminator (URL-tauglich, kein #)", () => {
+  assert.equal(handleToSlug("KochHeld", "A23B"), "KochHeld-A23B");
+});
+
+test("handleToSlug liefert null ohne vollstaendigen Handle", () => {
+  assert.equal(handleToSlug(null, "A23B"), null);
+  assert.equal(handleToSlug("KochHeld", null), null);
+});
+
+test("parseHandleSlug zerlegt am letzten Bindestrich", () => {
+  assert.deepEqual(parseHandleSlug("KochHeld-A23B"), {
+    username: "KochHeld",
+    discriminator: "A23B",
+  });
+});
+
+test("parseHandleSlug behaelt Bindestriche im Username", () => {
+  assert.deepEqual(parseHandleSlug("Koch-Held-A23B"), {
+    username: "Koch-Held",
+    discriminator: "A23B",
+  });
+});
+
+test("parseHandleSlug normalisiert den Discriminator auf Grossschreibung", () => {
+  assert.deepEqual(parseHandleSlug("KochHeld-a23b"), {
+    username: "KochHeld",
+    discriminator: "A23B",
+  });
+});
+
+test("parseHandleSlug lehnt ungueltige Slugs ab", () => {
+  assert.equal(parseHandleSlug("KochHeld"), null); // kein Discriminator
+  assert.equal(parseHandleSlug("KochHeld-"), null); // leerer Discriminator
+  assert.equal(parseHandleSlug("-A23B"), null); // leerer Username
+  assert.equal(parseHandleSlug("KochHeld-A1"), null); // Discriminator zu kurz
+  assert.equal(parseHandleSlug("KochHeld-A1IB"), null); // I nicht im Alphabet
+});
+
+test("handleToSlug und parseHandleSlug sind invers", () => {
+  const slug = handleToSlug("Koch-Held", "A23B");
+  assert.ok(slug);
+  assert.deepEqual(parseHandleSlug(slug), {
+    username: "Koch-Held",
+    discriminator: "A23B",
+  });
+});
diff --git a/packages/api/src/trpc/routers/users.ts b/packages/api/src/trpc/routers/users.ts
index 5718002..6ca11cf 100644
--- a/packages/api/src/trpc/routers/users.ts
+++ b/packages/api/src/trpc/routers/users.ts
@@ -1,6 +1,6 @@
 import { schema } from "@hellth/db";
 import { TRPCError } from "@trpc/server";
-import { asc, eq, sql } from "drizzle-orm";
+import { and, asc, eq, gte, sql } from "drizzle-orm";
 import { z } from "zod";
 import { auth } from "../../lib/auth";
 import {
@@ -9,6 +9,7 @@ import {
   USERNAME_MIN_LENGTH,
   formatHandle,
   generateUniqueDiscriminator,
+  parseHandleSlug,
   validateUsername,
 } from "../../lib/handle";
 import { auditSecurityEvent } from "../../lib/security-audit";
@@ -214,6 +215,91 @@ export const usersRouter = router({
       return { ok: true };
     }),
 
+  // Öffentliches Fremdprofil per Handle-Slug (z. B. "KochHeld-A12B").
+  // DATENSCHUTZ: liefert NUR, wenn der Eigentümer profileVisible=true gesetzt
+  // hat (sonst NOT_FOUND, damit die Existenz nicht durchsickert). Strikte
+  // Feld-Whitelist — ausschließlich öffentliche Identitäts- und Aggregatdaten,
+  // NIEMALS Art.-9-Gesundheitsdaten (Gewicht/Kalorien/Ziele) oder Kontaktdaten.
+  publicProfileByHandle: protectedProcedure
+    .input(z.object({ handle: z.string().min(1).max(64) }))
+    .query(async ({ ctx, input }) => {
+      const parsed = parseHandleSlug(input.handle);
+      if (!parsed) {
+        throw new TRPCError({ code: "NOT_FOUND", message: "Profil nicht gefunden" });
+      }
+
+      const target = await ctx.db.query.user.findFirst({
+        where: (row, { and: andWhere, eq: rowEq }) =>
+          andWhere(
+            rowEq(row.username, parsed.username),
+            rowEq(row.discriminator, parsed.discriminator),
+          ),
+        columns: {
+          id: true,
+          username: true,
+          discriminator: true,
+          bio: true,
+          image: true,
+          profileVisible: true,
+        },
+      });
+
+      // Privacy-Gate serverseitig: privates oder nicht existierendes Profil
+      // ist von außen nicht unterscheidbar (immer NOT_FOUND).
+      if (!target || !target.profileVisible) {
+        throw new TRPCError({ code: "NOT_FOUND", message: "Profil nicht gefunden" });
+      }
+
+      // Aggregierte Aktivitäts-Punkte (kein Health-Detail). 30-Tage-Fenster
+      // über das date-Feld (YYYY-MM-DD) der activity_logs.
+      const thirtyDaysAgo = new Date();
+      thirtyDaysAgo.setUTCDate(thirtyDaysAgo.getUTCDate() - 30);
+      const since = thirtyDaysAgo.toISOString().slice(0, 10);
+
+      const [totalRow] = await ctx.db
+        .select({ points: sql<number>`coalesce(sum(${schema.activityLogs.points}), 0)` })
+        .from(schema.activityLogs)
+        .where(eq(schema.activityLogs.userId, target.id));
+
+      const [recentRow] = await ctx.db
+        .select({ points: sql<number>`coalesce(sum(${schema.activityLogs.points}), 0)` })
+        .from(schema.activityLogs)
+        .where(
+          and(
+            eq(schema.activityLogs.userId, target.id),
+            gte(schema.activityLogs.date, since),
+          ),
+        );
+
+      // Anonymisierte Aktivitäts-Streak: Anzahl distinkter Tage mit Aktivität
+      // in den letzten 7 Tagen. Nur "wie aktiv", keine Inhalte/Werte.
+      const sevenDaysAgo = new Date();
+      sevenDaysAgo.setUTCDate(sevenDaysAgo.getUTCDate() - 7);
+      const since7 = sevenDaysAgo.toISOString().slice(0, 10);
+      const [streakRow] = await ctx.db
+        .select({ days: sql<number>`count(distinct ${schema.activityLogs.date})` })
+        .from(schema.activityLogs)
+        .where(
+          and(
+            eq(schema.activityLogs.userId, target.id),
+            gte(schema.activityLogs.date, since7),
+          ),
+        );
+
+      return {
+        handle: formatHandle(target.username, target.discriminator),
+        username: target.username,
+        discriminator: target.discriminator,
+        bio: target.bio,
+        image: target.image,
+        points: {
+          total: Number(totalRow?.points ?? 0),
+          last30Days: Number(recentRow?.points ?? 0),
+        },
+        activeDaysLast7: Number(streakRow?.days ?? 0),
+      };
+    }),
+
   setTheme: protectedProcedure
     .input(z.object({ theme: z.enum(["dark", "light"]).nullable() }))
     .mutation(async ({ ctx, input }) => {
diff --git a/packages/api/src/trpc/users.test.ts b/packages/api/src/trpc/users.test.ts
new file mode 100644
index 0000000..8a48ced
--- /dev/null
+++ b/packages/api/src/trpc/users.test.ts
@@ -0,0 +1,154 @@
+import assert from "node:assert/strict";
+import test from "node:test";
+import { appRouter } from "./index";
+
+// Schlanker Mock nur für users.publicProfileByHandle. Deckt sowohl
+// query.user.findFirst (Profil-Lookup) als auch den select().from().where()
+// Query-Builder (Punkte-Aggregate) ab.
+
+type UserRow = {
+  id: string;
+  username: string | null;
+  discriminator: string | null;
+  bio: string | null;
+  image: string | null;
+  profileVisible: boolean;
+} | null;
+
+function createContext(targetUser: UserRow, aggregates: { total: number; recent: number; days: number }) {
+  const user = { id: "viewer", email: "viewer@example.org", role: "user" };
+
+  // Reihenfolge der select()-Aufrufe im Endpoint: total, recent(30T), streak(7T).
+  const selectResults = [
+    [{ points: aggregates.total }],
+    [{ points: aggregates.recent }],
+    [{ days: aggregates.days }],
+  ];
+  let selectIndex = 0;
+
+  const db = {
+    query: {
+      user: {
+        findFirst: async () => targetUser,
+      },
+    },
+    select() {
+      const result = selectResults[selectIndex++] ?? [];
+      return {
+        from() {
+          return {
+            where() {
+              return Promise.resolve(result);
+            },
+          };
+        },
+      };
+    },
+  };
+
+  return {
+    db,
+    headers: new Headers(),
+    session: { user },
+    user,
+    userRole: "user",
+    isPlatformAdmin: false,
+  };
+}
+
+const visibleUser: UserRow = {
+  id: "target-1",
+  username: "KochHeld",
+  discriminator: "A23B",
+  bio: "Mag Meal Prep.",
+  image: null,
+  profileVisible: true,
+};
+
+test("publicProfileByHandle liefert sichtbares Profil mit Whitelist-Feldern + Aggregaten", async () => {
+  const caller = appRouter.createCaller(
+    createContext(visibleUser, { total: 340, recent: 80, days: 5 }) as never,
+  );
+
+  const result = await caller.users.publicProfileByHandle({ handle: "KochHeld-A23B" });
+
+  assert.equal(result.handle, "KochHeld#A23B");
+  assert.equal(result.username, "KochHeld");
+  assert.equal(result.bio, "Mag Meal Prep.");
+  assert.equal(result.points.total, 340);
+  assert.equal(result.points.last30Days, 80);
+  assert.equal(result.activeDaysLast7, 5);
+});
+
+test("publicProfileByHandle leakt KEINE Health-/Kontaktfelder", async () => {
+  const caller = appRouter.createCaller(
+    createContext(visibleUser, { total: 0, recent: 0, days: 0 }) as never,
+  );
+
+  const result = await caller.users.publicProfileByHandle({ handle: "KochHeld-A23B" });
+
+  for (const forbidden of ["email", "id", "weightKg", "calories", "profileVisible", "role", "createdAt"]) {
+    assert.equal(forbidden in result, false, `Feld ${forbidden} darf nicht geliefert werden`);
+  }
+});
+
+test("publicProfileByHandle wirft NOT_FOUND bei privatem Profil", async () => {
+  const caller = appRouter.createCaller(
+    createContext({ ...visibleUser, profileVisible: false }, { total: 0, recent: 0, days: 0 }) as never,
+  );
+
+  await assert.rejects(
+    () => caller.users.publicProfileByHandle({ handle: "KochHeld-A23B" }),
+    (error: unknown) => {
+      assert.equal((error as { code?: string }).code, "NOT_FOUND");
+      return true;
+    },
+  );
+});
+
+test("publicProfileByHandle wirft NOT_FOUND bei unbekanntem Handle", async () => {
+  const caller = appRouter.createCaller(
+    createContext(null, { total: 0, recent: 0, days: 0 }) as never,
+  );
+
+  await assert.rejects(
+    () => caller.users.publicProfileByHandle({ handle: "Niemand-Z9Z9" }),
+    (error: unknown) => {
+      assert.equal((error as { code?: string }).code, "NOT_FOUND");
+      return true;
+    },
+  );
+});
+
+test("publicProfileByHandle wirft NOT_FOUND bei ungueltigem Slug", async () => {
+  const caller = appRouter.createCaller(
+    createContext(visibleUser, { total: 0, recent: 0, days: 0 }) as never,
+  );
+
+  await assert.rejects(
+    () => caller.users.publicProfileByHandle({ handle: "KeinDiscriminator" }),
+    (error: unknown) => {
+      assert.equal((error as { code?: string }).code, "NOT_FOUND");
+      return true;
+    },
+  );
+});
+
+test("publicProfileByHandle erfordert Authentifizierung", async () => {
+  const caller = appRouter.createCaller({
+    db: {},
+    headers: new Headers(),
+    session: null,
+    user: null,
+    userRole: "user",
+    isPlatformAdmin: false,
+  } as never);
+
+  await assert.rejects(
+    () => caller.users.publicProfileByHandle({ handle: "KochHeld-A23B" }),
+    (error: unknown) => {
+      assert.equal((error as { code?: string }).code, "UNAUTHORIZED");
+      return true;
+    },
+  );
+});