feat: manage waitlist and remove group members

- Add group-waitlist module (list/promote/remove entries)
- Remove attendee with optional atomic promotion from waitlist
- Block removal when attendee has payments (attendee_has_payments)
- Waitlist detail modal matching members UI; optimistic add-to-waitlist
- Responsive tweaks for the members/waitlist tabs

apps/backend/src/http/problem-builders.ts

@@ -116,4 +116,11 @@ export function alreadyWaitlistedProblem(): ProblemDetails {
     detail: 'Este número de teléfono ya está en la lista de espera del grupo.',
     code: 'already_waitlisted',
   });
+}
+
+export function attendeeHasPaymentsProblem(): ProblemDetails {
+  return conflictProblem({
+    detail: 'Este miembro tiene cobros asociados. Gestiona o cancela sus cobros antes de quitarlo del grupo.',
+    code: 'attendee_has_payments',
+  });
 }

apps/backend/src/modules/attendees/features/remove/route.ts

@@ -0,0 +1,24 @@
+import { type RemoveAttendeeQuery, RemoveAttendeeQuerySchema } from '@gruperly/shared';
+import { Hono } from 'hono';
+import { problemJson, resultJson, unauthorizedProblem } from '@/http/problem-details';
+import { validate } from '@/http/validate';
+import { RemoveAttendee } from './use-case';
+
+const route = new Hono();
+
+route.delete('/:groupId/attendees/:attendeeId', validate.query(RemoveAttendeeQuerySchema), async (c) => {
+  const user = c.get('user');
+  if (!user) {
+    return problemJson(c, unauthorizedProblem(c.req.path));
+  }
+  const groupId = c.req.param('groupId');
+  const attendeeId = c.req.param('attendeeId');
+  const query = c.req.valid('query') as RemoveAttendeeQuery;
+  const useCase = new RemoveAttendee();
+  const result = await useCase.execute(groupId, attendeeId, user.id, {
+    promoteFromWaitlist: query.promoteFromWaitlist,
+  });
+  return resultJson(c, result);
+});
+
+export default route;

apps/backend/src/modules/attendees/features/remove/use-case.ts

@@ -0,0 +1,73 @@
+import type { Prisma, PrismaClient } from '@generated/prisma/client';
+import type { ProblemDetails, RemoveAttendeeResult, Result } from '@gruperly/shared';
+import { err, ok } from '@gruperly/shared';
+import { attendeeHasPaymentsProblem, notFoundResourceProblem } from '@/http/problem-builders';
+import { default as prisma, UnitOfWork } from '@/lib/prisma';
+import {
+  findGroupOwnedByUser,
+  toGroupWaitlistEntryDto,
+} from '@/modules/group-waitlist/lib/helpers';
+import { promoteFirstPendingWaitlistEntry } from '@/modules/group-waitlist/lib/promote';
+
+type RemoveAttendeeDeps = {
+  db?: Pick<PrismaClient, 'group' | 'attendee' | 'payment'>;
+  unitOfWork?: UnitOfWork;
+};
+
+type RemoveAttendeeOptions = {
+  promoteFromWaitlist?: boolean;
+};
+
+export class RemoveAttendee {
+  constructor(private readonly deps: RemoveAttendeeDeps = {}) {}
+
+  async execute(
+    groupId: string,
+    attendeeId: string,
+    userId: string,
+    options: RemoveAttendeeOptions = {},
+  ): Promise<Result<RemoveAttendeeResult, ProblemDetails>> {
+    const db = this.deps.db ?? prisma;
+    const unitOfWork = this.deps.unitOfWork ?? new UnitOfWork(prisma);
+
+    const groupResult = await findGroupOwnedByUser(db, groupId, userId);
+    if (!groupResult.ok) {
+      return groupResult;
+    }
+    const group = groupResult.value;
+
+    const attendee = await db.attendee.findFirst({ where: { id: attendeeId, groupId } });
+    if (!attendee) {
+      return err(notFoundResourceProblem('Attendee', attendeeId));
+    }
+
+    const paymentsCount = await db.payment.count({ where: { attendeeId } });
+    if (paymentsCount > 0) {
+      return err(attendeeHasPaymentsProblem());
+    }
+
+    return unitOfWork.executeResult(
+      async (tx: Prisma.TransactionClient): Promise<Result<RemoveAttendeeResult, ProblemDetails>> => {
+        await tx.attendee.delete({ where: { id: attendeeId } });
+
+        if (!options.promoteFromWaitlist) {
+          return ok({ removedAttendeeId: attendeeId, promoted: null });
+        }
+
+        const promoteResult = await promoteFirstPendingWaitlistEntry(tx, group);
+        if (!promoteResult.ok) {
+          return err(promoteResult.error);
+        }
+        if (!promoteResult.value) {
+          return ok({ removedAttendeeId: attendeeId, promoted: null });
+        }
+
+        await tx.groupWaitlistEntry.delete({ where: { id: promoteResult.value.entry.id } });
+        return ok({
+          removedAttendeeId: attendeeId,
+          promoted: toGroupWaitlistEntryDto(promoteResult.value.entry),
+        });
+      },
+    );
+  }
+}

apps/backend/src/modules/group-waitlist/features/get-all/route.ts

@@ -0,0 +1,21 @@
+import { type GroupWaitlistQuery, GroupWaitlistQuerySchema } from '@gruperly/shared';
+import { Hono } from 'hono';
+import { problemJson, resultJson, unauthorizedProblem } from '@/http/problem-details';
+import { validate } from '@/http/validate';
+import { ListGroupWaitlistEntries } from './use-case';
+
+const route = new Hono();
+
+route.get('/:groupId/waitlist', validate.query(GroupWaitlistQuerySchema), async (c) => {
+  const user = c.get('user');
+  if (!user) {
+    return problemJson(c, unauthorizedProblem(c.req.path));
+  }
+  const groupId = c.req.param('groupId');
+  const query = c.req.valid('query') as GroupWaitlistQuery;
+  const useCase = new ListGroupWaitlistEntries();
+  const result = await useCase.execute(groupId, user.id, query);
+  return resultJson(c, result);
+});
+
+export default route;

apps/backend/src/modules/group-waitlist/features/get-all/use-case.ts

@@ -0,0 +1,43 @@
+import type { PrismaClient } from '@generated/prisma/client';
+import type { GroupWaitlistList, GroupWaitlistQuery, ProblemDetails, Result } from '@gruperly/shared';
+import { ok } from '@gruperly/shared';
+import { getPaginationMetadata, getPaginationOffset } from '@/lib/pagination';
+import prisma from '@/lib/prisma';
+import { findGroupForUser, type GroupWaitlistEntryRecord, toGroupWaitlistEntryDto } from '../../lib/helpers';
+
+type ListGroupWaitlistEntriesDeps = {
+  db?: Pick<PrismaClient, 'group' | 'groupWaitlistEntry'>;
+};
+
+export class ListGroupWaitlistEntries {
+  constructor(private readonly deps: ListGroupWaitlistEntriesDeps = {}) {}
+
+  async execute(
+    groupId: string,
+    userId: string,
+    query: GroupWaitlistQuery,
+  ): Promise<Result<GroupWaitlistList, ProblemDetails>> {
+    const db = this.deps.db ?? prisma;
+
+    const groupResult = await findGroupForUser(db, groupId, userId);
+    if (!groupResult.ok) {
+      return groupResult;
+    }
+
+    const where = { groupId, status: 'PENDING' as const };
+    const [records, total] = await Promise.all([
+      db.groupWaitlistEntry.findMany({
+        where,
+        skip: getPaginationOffset(query),
+        take: query.pageSize,
+        orderBy: { createdAt: 'asc' },
+      }),
+      db.groupWaitlistEntry.count({ where }),
+    ]);
+
+    return ok({
+      data: records.map((record) => toGroupWaitlistEntryDto(record as unknown as GroupWaitlistEntryRecord)),
+      pagination: getPaginationMetadata(query, total),
+    });
+  }
+}

apps/backend/src/modules/group-waitlist/features/promote/route.ts

@@ -0,0 +1,19 @@
+import { Hono } from 'hono';
+import { problemJson, resultJson, unauthorizedProblem } from '@/http/problem-details';
+import { PromoteGroupWaitlistEntry } from './use-case';
+
+const route = new Hono();
+
+route.post('/:groupId/waitlist/:entryId/promote', async (c) => {
+  const user = c.get('user');
+  if (!user) {
+    return problemJson(c, unauthorizedProblem(c.req.path));
+  }
+  const groupId = c.req.param('groupId');
+  const entryId = c.req.param('entryId');
+  const useCase = new PromoteGroupWaitlistEntry();
+  const result = await useCase.execute(groupId, entryId, user.id);
+  return resultJson(c, result);
+});
+
+export default route;

apps/backend/src/modules/group-waitlist/features/promote/use-case.ts

@@ -0,0 +1,56 @@
+import type { Prisma, PrismaClient } from '@generated/prisma/client';
+import type { ProblemDetails, PromoteGroupWaitlistEntryResult, Result } from '@gruperly/shared';
+import { err, ok } from '@gruperly/shared';
+import { notFoundResourceProblem } from '@/http/problem-builders';
+import { default as prisma, UnitOfWork } from '@/lib/prisma';
+import {
+  findGroupOwnedByUser,
+  type GroupWaitlistEntryRecord,
+} from '../../lib/helpers';
+import { promoteWaitlistEntryRecord } from '../../lib/promote';
+
+type PromoteGroupWaitlistEntryDeps = {
+  db?: Pick<PrismaClient, 'group' | 'attendee' | 'groupWaitlistEntry'>;
+  unitOfWork?: UnitOfWork;
+};
+
+export class PromoteGroupWaitlistEntry {
+  constructor(private readonly deps: PromoteGroupWaitlistEntryDeps = {}) {}
+
+  async execute(
+    groupId: string,
+    entryId: string,
+    userId: string,
+  ): Promise<Result<PromoteGroupWaitlistEntryResult, ProblemDetails>> {
+    const db = this.deps.db ?? prisma;
+    const unitOfWork = this.deps.unitOfWork ?? new UnitOfWork(prisma);
+
+    const groupResult = await findGroupOwnedByUser(db, groupId, userId);
+    if (!groupResult.ok) {
+      return groupResult;
+    }
+
+    const entry = await db.groupWaitlistEntry.findFirst({
+      where: { id: entryId, groupId },
+    });
+    if (!entry) {
+      return err(notFoundResourceProblem('GroupWaitlistEntry', entryId));
+    }
+
+    return unitOfWork.executeResult(
+      async (tx: Prisma.TransactionClient) => {
+        const promoteResult = await promoteWaitlistEntryRecord(
+          tx,
+          groupResult.value,
+          entry as unknown as GroupWaitlistEntryRecord,
+        );
+        if (!promoteResult.ok) {
+          return promoteResult;
+        }
+
+        await tx.groupWaitlistEntry.delete({ where: { id: entry.id } });
+        return ok({ attendee: promoteResult.value });
+      },
+    );
+  }
+}

apps/backend/src/modules/group-waitlist/features/remove/route.ts

@@ -0,0 +1,19 @@
+import { Hono } from 'hono';
+import { problemJson, resultJson, unauthorizedProblem } from '@/http/problem-details';
+import { RemoveGroupWaitlistEntry } from './use-case';
+
+const route = new Hono();
+
+route.delete('/:groupId/waitlist/:entryId', async (c) => {
+  const user = c.get('user');
+  if (!user) {
+    return problemJson(c, unauthorizedProblem(c.req.path));
+  }
+  const groupId = c.req.param('groupId');
+  const entryId = c.req.param('entryId');
+  const useCase = new RemoveGroupWaitlistEntry();
+  const result = await useCase.execute(groupId, entryId, user.id);
+  return resultJson(c, result);
+});
+
+export default route;

apps/backend/src/modules/group-waitlist/features/remove/use-case.ts

@@ -0,0 +1,37 @@
+import type { PrismaClient } from '@generated/prisma/client';
+import type { ProblemDetails, RemoveGroupWaitlistEntryResult, Result } from '@gruperly/shared';
+import { err, ok } from '@gruperly/shared';
+import { notFoundResourceProblem } from '@/http/problem-builders';
+import prisma from '@/lib/prisma';
+import { findGroupOwnedByUser } from '../../lib/helpers';
+
+type RemoveGroupWaitlistEntryDeps = {
+  db?: Pick<PrismaClient, 'group' | 'groupWaitlistEntry'>;
+};
+
+export class RemoveGroupWaitlistEntry {
+  constructor(private readonly deps: RemoveGroupWaitlistEntryDeps = {}) {}
+
+  async execute(
+    groupId: string,
+    entryId: string,
+    userId: string,
+  ): Promise<Result<RemoveGroupWaitlistEntryResult, ProblemDetails>> {
+    const db = this.deps.db ?? prisma;
+
+    const groupResult = await findGroupOwnedByUser(db, groupId, userId);
+    if (!groupResult.ok) {
+      return groupResult;
+    }
+
+    const existing = await db.groupWaitlistEntry.findFirst({
+      where: { id: entryId, groupId },
+    });
+    if (!existing) {
+      return err(notFoundResourceProblem('GroupWaitlistEntry', entryId));
+    }
+
+    await db.groupWaitlistEntry.delete({ where: { id: entryId } });
+    return ok({ deleted: true });
+  }
+}

apps/backend/src/modules/group-waitlist/index.ts

@@ -0,0 +1 @@
+export { default as groupWaitlistRoutes } from './routes';

apps/backend/src/modules/group-waitlist/lib/helpers.ts

@@ -0,0 +1,65 @@
+import type { Group, PrismaClient } from '@generated/prisma/client';
+import type { GroupWaitlistEntryDto, ProblemDetails, Result } from '@gruperly/shared';
+import { err, ok } from '@gruperly/shared';
+import { noGroupAccessProblem, notFoundResourceProblem } from '@/http/problem-builders';
+
+export type GroupWaitlistEntryRecord = {
+  id: string;
+  groupId: string;
+  fullName: string;
+  phone: string;
+  email: string | null;
+  notes: string | null;
+  status: GroupWaitlistEntryDto['status'];
+  createdAt: Date;
+  updatedAt: Date;
+};
+
+export function toGroupWaitlistEntryDto(record: GroupWaitlistEntryRecord): GroupWaitlistEntryDto {
+  return {
+    id: record.id,
+    groupId: record.groupId,
+    fullName: record.fullName,
+    phone: record.phone,
+    email: record.email,
+    notes: record.notes,
+    status: record.status,
+    createdAt: record.createdAt.toISOString(),
+    updatedAt: record.updatedAt.toISOString(),
+  };
+}
+
+export async function findGroupForUser(
+  db: Pick<PrismaClient, 'group'>,
+  groupId: string,
+  userId: string,
+): Promise<Result<Group, ProblemDetails>> {
+  const group = await db.group.findUnique({
+    where: { id: groupId },
+    include: { members: { where: { userId } } },
+  });
+  if (!group) {
+    return err(notFoundResourceProblem('Group', groupId));
+  }
+  const isOwner = group.createdById === userId;
+  const isMember = group.members.length > 0;
+  if (!isOwner && !isMember) {
+    return err(noGroupAccessProblem());
+  }
+  return ok(group);
+}
+
+export async function findGroupOwnedByUser(
+  db: Pick<PrismaClient, 'group'>,
+  groupId: string,
+  userId: string,
+): Promise<Result<Group, ProblemDetails>> {
+  const group = await db.group.findUnique({ where: { id: groupId } });
+  if (!group) {
+    return err(notFoundResourceProblem('Group', groupId));
+  }
+  if (group.createdById !== userId) {
+    return err(noGroupAccessProblem());
+  }
+  return ok(group);
+}

apps/backend/src/modules/group-waitlist/lib/promote.ts

@@ -0,0 +1,83 @@
+import type { PrismaClient } from '@generated/prisma/client';
+import type { AttendeeDto, ProblemDetails, Result } from '@gruperly/shared';
+import { err, ok } from '@gruperly/shared';
+import { capacityReachedProblem, conflictProblem } from '@/http/problem-builders';
+import { type AttendeeRecord, toAttendeeDto } from '@/modules/attendees/lib/helpers';
+import { type GroupWaitlistEntryRecord } from './helpers';
+
+export type PromoteDb = Pick<PrismaClient, 'attendee' | 'groupWaitlistEntry'>;
+
+type PromoteGroup = {
+  id: string;
+  capacity: number | null;
+};
+
+export async function findFirstPendingWaitlistEntry(
+  db: PromoteDb,
+  groupId: string,
+): Promise<GroupWaitlistEntryRecord | null> {
+  const record = await db.groupWaitlistEntry.findFirst({
+    where: { groupId, status: 'PENDING' },
+    orderBy: { createdAt: 'asc' },
+  });
+  return record as GroupWaitlistEntryRecord | null;
+}
+
+export async function promoteWaitlistEntryRecord(
+  db: PromoteDb,
+  group: PromoteGroup,
+  entry: GroupWaitlistEntryRecord,
+): Promise<Result<AttendeeDto, ProblemDetails>> {
+  if (group.capacity !== null) {
+    const currentCount = await db.attendee.count({ where: { groupId: group.id } });
+    if (currentCount >= group.capacity) {
+      return err(capacityReachedProblem(group.capacity));
+    }
+  }
+
+  const existing = await db.attendee.findFirst({
+    where: { groupId: group.id, phone: entry.phone },
+  });
+  if (existing) {
+    return err(
+      conflictProblem({
+        detail: 'Ya existe un alumno registrado con este número de teléfono en este grupo.',
+        code: 'attendee_already_registered',
+      }),
+    );
+  }
+
+  const attendee = await db.attendee.create({
+    data: {
+      groupId: group.id,
+      fullName: entry.fullName,
+      phone: entry.phone,
+      email: entry.email,
+      notes: entry.notes,
+    },
+  });
+
+  return ok(toAttendeeDto(attendee as unknown as AttendeeRecord));
+}
+
+export type PromoteFirstResult = {
+  attendee: AttendeeDto;
+  entry: GroupWaitlistEntryRecord;
+};
+
+export async function promoteFirstPendingWaitlistEntry(
+  db: PromoteDb,
+  group: PromoteGroup,
+): Promise<Result<PromoteFirstResult | null, ProblemDetails>> {
+  const entry = await findFirstPendingWaitlistEntry(db, group.id);
+  if (!entry) {
+    return ok(null);
+  }
+
+  const result = await promoteWaitlistEntryRecord(db, group, entry);
+  if (!result.ok) {
+    return result;
+  }
+
+  return ok({ attendee: result.value, entry });
+}

apps/backend/src/modules/group-waitlist/routes.ts

@@ -0,0 +1,12 @@
+import { Hono } from 'hono';
+import getAllRoute from './features/get-all/route';
+import promoteRoute from './features/promote/route';
+import removeRoute from './features/remove/route';
+
+const routes = new Hono();
+
+routes.route('/', getAllRoute);
+routes.route('/', promoteRoute);
+routes.route('/', removeRoute);
+
+export default routes;

apps/backend/src/modules/groups/routes.ts

@@ -2,6 +2,8 @@ import { Hono } from 'hono';
 import addToGroupWaitlistRoute from '../attendees/features/add-to-waitlist/route';
 import bulkCreateAttendeesRoute from '../attendees/features/bulk-create/route';
 import createAttendeeRoute from '../attendees/features/create/route';
+import removeAttendeeRoute from '../attendees/features/remove/route';
+import groupWaitlistRoutes from '../group-waitlist/routes';
 import createFromOrganizationRoute from './features/create-from-organization/route';
 import getAllRoute from './features/get-all/route';
 import getByIdRoute from './features/get-by-id/route';
@@ -18,5 +20,7 @@ routes.route('/', createAttendeeRoute);
 routes.route('/', bulkCreateAttendeesRoute);
 routes.route('/', getByIdRoute);
 routes.route('/', addToGroupWaitlistRoute);
+routes.route('/', groupWaitlistRoutes);
+routes.route('/', removeAttendeeRoute);
 
 export default routes;

apps/backend/test/waitlist-management.test.ts

@@ -0,0 +1,352 @@
+import { beforeEach, describe, expect, it, mock, vi } from 'bun:test';
+import { Hono } from 'hono';
+
+const db = {
+  group: {
+    findUnique: mock(),
+  },
+  attendee: {
+    findFirst: mock(),
+    findMany: mock(),
+    count: mock(),
+    create: mock(),
+    delete: mock(),
+  },
+  groupWaitlistEntry: {
+    findMany: mock(),
+    findFirst: mock(),
+    count: mock(),
+    create: mock(),
+    delete: mock(),
+  },
+  payment: {
+    count: mock(),
+  },
+};
+
+mock.module('@/lib/prisma', () => ({
+  default: db,
+  getPrismaClient: mock(),
+  UnitOfWork: class {
+    executeResult = mock(async (cb: (tx: unknown) => Promise<unknown>) => cb(db));
+    execute = mock(async (cb: (tx: unknown) => Promise<unknown>) => cb(db));
+  },
+}));
+
+import prisma from '@/lib/prisma';
+import { groupsRoutes } from '@/modules/groups';
+
+const teacherId = 'teacher-1';
+const mockGroup = {
+  id: 'group-1',
+  name: 'Taller de Pintura',
+  description: null,
+  createdById: teacherId,
+  inviteToken: null,
+  createdAt: new Date('2026-09-01T10:00:00.000Z'),
+  updatedAt: new Date('2026-09-01T10:00:00.000Z'),
+  days: ['MONDAY'],
+  time: '18:00',
+  capacity: 20,
+  price: 1500,
+  billingType: 'MONTHLY',
+  dueDay: 10,
+  members: [],
+};
+
+const waitlistEntry = (overrides: Record<string, unknown> = {}) => ({
+  id: 'wl-1',
+  groupId: 'group-1',
+  fullName: 'Martín Gómez',
+  phone: '+5491133445566',
+  email: null,
+  notes: null,
+  status: 'PENDING',
+  createdAt: new Date('2026-09-10T10:00:00.000Z'),
+  updatedAt: new Date('2026-09-10T10:00:00.000Z'),
+  ...overrides,
+});
+
+const attendee = (overrides: Record<string, unknown> = {}) => ({
+  id: 'att-1',
+  groupId: 'group-1',
+  fullName: 'Martín Gómez',
+  phone: '+5491133445566',
+  email: null,
+  guardianName: null,
+  guardianPhone: null,
+  notes: null,
+  createdAt: new Date('2026-09-18T10:00:00.000Z'),
+  updatedAt: new Date('2026-09-18T10:00:00.000Z'),
+  ...overrides,
+});
+
+function makeApp(userValue: unknown) {
+  const app = new Hono();
+  app.use('*', async (c, next) => {
+    c.set('user', userValue as never);
+    await next();
+  });
+  app.route('/groups', groupsRoutes);
+  return app;
+}
+
+describe('group waitlist management', () => {
+  beforeEach(() => {
+    vi.clearAllMocks();
+  });
+
+  describe('GET /groups/:groupId/waitlist', () => {
+    it('lists pending entries in FIFO order with pagination', async () => {
+      prisma.group.findUnique.mockResolvedValue(mockGroup as never);
+      prisma.groupWaitlistEntry.findMany.mockResolvedValue([
+        waitlistEntry({ id: 'wl-1', fullName: 'Ana García', createdAt: new Date('2026-09-08T10:00:00.000Z') }),
+        waitlistEntry({ id: 'wl-2', fullName: 'Pedro López', createdAt: new Date('2026-09-09T10:00:00.000Z') }),
+      ] as never);
+      prisma.groupWaitlistEntry.count.mockResolvedValue(2);
+
+      const res = await makeApp({ id: teacherId }).request('/groups/group-1/waitlist');
+
+      expect(res.status).toBe(200);
+      const data = await res.json();
+      expect(data.data).toHaveLength(2);
+      expect(data.data[0].fullName).toBe('Ana García');
+      expect(data.pagination).toEqual({ page: 1, pageSize: 10, total: 2, totalPages: 1 });
+      expect(prisma.groupWaitlistEntry.findMany).toHaveBeenCalledWith({
+        where: { groupId: 'group-1', status: 'PENDING' },
+        skip: 0,
+        take: 10,
+        orderBy: { createdAt: 'asc' },
+      });
+    });
+
+    it('rejects user without access to the group', async () => {
+      prisma.group.findUnique.mockResolvedValue(mockGroup as never);
+
+      const res = await makeApp({ id: 'other-user' }).request('/groups/group-1/waitlist');
+
+      expect(res.status).toBe(403);
+      expect(prisma.groupWaitlistEntry.findMany).not.toHaveBeenCalled();
+    });
+  });
+
+  describe('POST /groups/:groupId/waitlist/:entryId/promote', () => {
+    it('creates an attendee from the entry and removes it from the waitlist', async () => {
+      prisma.group.findUnique.mockResolvedValue(mockGroup as never);
+      prisma.groupWaitlistEntry.findFirst.mockResolvedValue(waitlistEntry() as never);
+      prisma.attendee.count.mockResolvedValue(5);
+      prisma.attendee.findFirst.mockResolvedValue(null);
+      prisma.attendee.create.mockResolvedValue(attendee() as never);
+
+      const res = await makeApp({ id: teacherId }).request('/groups/group-1/waitlist/wl-1/promote', {
+        method: 'POST',
+      });
+
+      expect(res.status).toBe(200);
+      const data = await res.json();
+      expect(data.attendee.fullName).toBe('Martín Gómez');
+      expect(prisma.attendee.create).toHaveBeenCalledWith({
+        data: expect.objectContaining({ groupId: 'group-1', fullName: 'Martín Gómez', phone: '+5491133445566' }),
+      });
+      expect(prisma.groupWaitlistEntry.delete).toHaveBeenCalledWith({ where: { id: 'wl-1' } });
+    });
+
+    it('rejects with 409 when the group reached its capacity', async () => {
+      prisma.group.findUnique.mockResolvedValue({ ...mockGroup, capacity: 5 } as never);
+      prisma.groupWaitlistEntry.findFirst.mockResolvedValue(waitlistEntry() as never);
+      prisma.attendee.count.mockResolvedValue(5);
+
+      const res = await makeApp({ id: teacherId }).request('/groups/group-1/waitlist/wl-1/promote', {
+        method: 'POST',
+      });
+
+      expect(res.status).toBe(409);
+      const body = await res.json();
+      expect(body.code).toBe('group_capacity_reached');
+      expect(prisma.attendee.create).not.toHaveBeenCalled();
+      expect(prisma.groupWaitlistEntry.delete).not.toHaveBeenCalled();
+    });
+
+    it('rejects with 409 when the phone already belongs to an attendee', async () => {
+      prisma.group.findUnique.mockResolvedValue(mockGroup as never);
+      prisma.groupWaitlistEntry.findFirst.mockResolvedValue(waitlistEntry() as never);
+      prisma.attendee.count.mockResolvedValue(5);
+      prisma.attendee.findFirst.mockResolvedValue({ id: 'att-existing' } as never);
+
+      const res = await makeApp({ id: teacherId }).request('/groups/group-1/waitlist/wl-1/promote', {
+        method: 'POST',
+      });
+
+      expect(res.status).toBe(409);
+      const body = await res.json();
+      expect(body.code).toBe('attendee_already_registered');
+      expect(prisma.attendee.create).not.toHaveBeenCalled();
+    });
+
+    it('returns 404 when the entry does not exist', async () => {
+      prisma.group.findUnique.mockResolvedValue(mockGroup as never);
+      prisma.groupWaitlistEntry.findFirst.mockResolvedValue(null);
+
+      const res = await makeApp({ id: teacherId }).request('/groups/group-1/waitlist/wl-missing/promote', {
+        method: 'POST',
+      });
+
+      expect(res.status).toBe(404);
+    });
+
+    it('rejects a non-owner user', async () => {
+      prisma.group.findUnique.mockResolvedValue(mockGroup as never);
+
+      const res = await makeApp({ id: 'other-user' }).request('/groups/group-1/waitlist/wl-1/promote', {
+        method: 'POST',
+      });
+
+      expect(res.status).toBe(403);
+      expect(prisma.attendee.create).not.toHaveBeenCalled();
+    });
+  });
+
+  describe('DELETE /groups/:groupId/waitlist/:entryId', () => {
+    it('removes a waitlist entry', async () => {
+      prisma.group.findUnique.mockResolvedValue(mockGroup as never);
+      prisma.groupWaitlistEntry.findFirst.mockResolvedValue(waitlistEntry() as never);
+
+      const res = await makeApp({ id: teacherId }).request('/groups/group-1/waitlist/wl-1', {
+        method: 'DELETE',
+      });
+
+      expect(res.status).toBe(200);
+      const data = await res.json();
+      expect(data.deleted).toBe(true);
+      expect(prisma.groupWaitlistEntry.delete).toHaveBeenCalledWith({ where: { id: 'wl-1' } });
+    });
+
+    it('returns 404 when the entry does not exist', async () => {
+      prisma.group.findUnique.mockResolvedValue(mockGroup as never);
+      prisma.groupWaitlistEntry.findFirst.mockResolvedValue(null);
+
+      const res = await makeApp({ id: teacherId }).request('/groups/group-1/waitlist/wl-missing', {
+        method: 'DELETE',
+      });
+
+      expect(res.status).toBe(404);
+      expect(prisma.groupWaitlistEntry.delete).not.toHaveBeenCalled();
+    });
+
+    it('rejects a non-owner user', async () => {
+      prisma.group.findUnique.mockResolvedValue(mockGroup as never);
+
+      const res = await makeApp({ id: 'other-user' }).request('/groups/group-1/waitlist/wl-1', {
+        method: 'DELETE',
+      });
+
+      expect(res.status).toBe(403);
+      expect(prisma.groupWaitlistEntry.delete).not.toHaveBeenCalled();
+    });
+  });
+
+  describe('DELETE /groups/:groupId/attendees/:attendeeId', () => {
+    it('removes an attendee without promotion', async () => {
+      prisma.group.findUnique.mockResolvedValue(mockGroup as never);
+      prisma.attendee.findFirst.mockResolvedValue(attendee() as never);
+      prisma.payment.count.mockResolvedValue(0);
+
+      const res = await makeApp({ id: teacherId }).request('/groups/group-1/attendees/att-1', {
+        method: 'DELETE',
+      });
+
+      expect(res.status).toBe(200);
+      const body = await res.json();
+      expect(body.removedAttendeeId).toBe('att-1');
+      expect(body.promoted).toBeNull();
+      expect(prisma.attendee.delete).toHaveBeenCalledWith({ where: { id: 'att-1' } });
+    });
+
+    it('removes an attendee and promotes the first pending waitlist entry atomically', async () => {
+      prisma.group.findUnique.mockResolvedValue(mockGroup as never);
+      prisma.attendee.findFirst.mockImplementation(async ({ where }: { where?: { id?: string } }) => {
+        if (where?.id) return attendee() as never;
+        return null;
+      });
+      prisma.payment.count.mockResolvedValue(0);
+      prisma.groupWaitlistEntry.findFirst.mockResolvedValue(
+        waitlistEntry({ id: 'wl-1', fullName: 'Sofía Ruiz', phone: '+5491133778899' }) as never,
+      );
+      prisma.attendee.count.mockResolvedValue(5);
+      prisma.attendee.create.mockResolvedValue(
+        attendee({ id: 'att-2', fullName: 'Sofía Ruiz', phone: '+5491133778899' }) as never,
+      );
+
+      const res = await makeApp({ id: teacherId }).request(
+        '/groups/group-1/attendees/att-1?promoteFromWaitlist=true',
+        { method: 'DELETE' },
+      );
+
+      expect(res.status).toBe(200);
+      const body = await res.json();
+      expect(body.removedAttendeeId).toBe('att-1');
+      expect(body.promoted).toMatchObject({ id: 'wl-1', fullName: 'Sofía Ruiz' });
+      expect(prisma.attendee.delete).toHaveBeenCalledWith({ where: { id: 'att-1' } });
+      expect(prisma.groupWaitlistEntry.delete).toHaveBeenCalledWith({ where: { id: 'wl-1' } });
+      expect(prisma.attendee.create).toHaveBeenCalledWith({
+        data: expect.objectContaining({ fullName: 'Sofía Ruiz', phone: '+5491133778899' }),
+      });
+    });
+
+    it('removes the attendee when promote requested but waitlist is empty', async () => {
+      prisma.group.findUnique.mockResolvedValue(mockGroup as never);
+      prisma.attendee.findFirst.mockResolvedValue(attendee() as never);
+      prisma.payment.count.mockResolvedValue(0);
+      prisma.groupWaitlistEntry.findFirst.mockResolvedValue(null);
+
+      const res = await makeApp({ id: teacherId }).request(
+        '/groups/group-1/attendees/att-1?promoteFromWaitlist=true',
+        { method: 'DELETE' },
+      );
+
+      expect(res.status).toBe(200);
+      const body = await res.json();
+      expect(body.removedAttendeeId).toBe('att-1');
+      expect(body.promoted).toBeNull();
+      expect(prisma.attendee.create).not.toHaveBeenCalled();
+    });
+
+    it('blocks removal when the attendee has payments', async () => {
+      prisma.group.findUnique.mockResolvedValue(mockGroup as never);
+      prisma.attendee.findFirst.mockResolvedValue(attendee() as never);
+      prisma.payment.count.mockResolvedValue(2);
+
+      const res = await makeApp({ id: teacherId }).request('/groups/group-1/attendees/att-1', {
+        method: 'DELETE',
+      });
+
+      expect(res.status).toBe(409);
+      const body = await res.json();
+      expect(body.code).toBe('attendee_has_payments');
+      expect(prisma.attendee.delete).not.toHaveBeenCalled();
+    });
+
+    it('returns 404 when the attendee does not belong to the group', async () => {
+      prisma.group.findUnique.mockResolvedValue(mockGroup as never);
+      prisma.attendee.findFirst.mockResolvedValue(null);
+
+      const res = await makeApp({ id: teacherId }).request('/groups/group-1/attendees/att-missing', {
+        method: 'DELETE',
+      });
+
+      expect(res.status).toBe(404);
+      expect(prisma.attendee.delete).not.toHaveBeenCalled();
+    });
+
+    it('rejects a non-owner user', async () => {
+      prisma.group.findUnique.mockResolvedValue(mockGroup as never);
+
+      const res = await makeApp({ id: 'other-user' }).request('/groups/group-1/attendees/att-1', {
+        method: 'DELETE',
+      });
+
+      expect(res.status).toBe(403);
+      expect(prisma.attendee.delete).not.toHaveBeenCalled();
+    });
+  });
+});