diff --git a/apps/scheduler/app/api/scheduler/availability/route.ts b/apps/scheduler/app/api/scheduler/availability/route.ts
new file mode 100644
index 0000000000..b1ef388380
--- /dev/null
+++ b/apps/scheduler/app/api/scheduler/availability/route.ts
@@ -0,0 +1,51 @@
+import { NextResponse, type NextRequest } from "next/server";
+import { z, ZodError } from "zod";
+
+import { requireSchedulerSession } from "@scheduler/lib/scheduler/auth";
+import { getAvailability } from "@scheduler/lib/scheduler/service";
+
+export const dynamic = "force-dynamic";
+
+const querySchema = z.object({
+  attendeeIds: z.array(z.number().int().positive()).min(1),
+  rangeStart: z.string().datetime(),
+  rangeEnd: z.string().datetime(),
+  durationMinutes: z.number().int().positive(),
+});
+
+function parseAttendeeIds(raw: string | null): number[] {
+  if (!raw) return [];
+  return raw
+    .split(",")
+    .map((value) => Number(value.trim()))
+    .filter((value) => Number.isInteger(value) && value > 0);
+}
+
+export async function GET(request: NextRequest) {
+  const auth = await requireSchedulerSession(request);
+  if ("response" in auth) return auth.response;
+
+  const params = request.nextUrl.searchParams;
+  try {
+    const input = querySchema.parse({
+      attendeeIds: parseAttendeeIds(params.get("attendeeIds")),
+      rangeStart: params.get("rangeStart") ?? undefined,
+      rangeEnd: params.get("rangeEnd") ?? undefined,
+      durationMinutes: Number(params.get("durationMinutes")),
+    });
+
+    const result = await getAvailability(
+      Number(auth.session.user.id),
+      input.attendeeIds,
+      input.rangeStart,
+      input.rangeEnd,
+      input.durationMinutes
+    );
+    return NextResponse.json(result);
+  } catch (error) {
+    if (error instanceof ZodError) {
+      return NextResponse.json({ error: "VALIDATION_FAILED", issues: error.issues }, { status: 400 });
+    }
+    throw error;
+  }
+}
diff --git a/apps/scheduler/app/api/scheduler/connections/route.ts b/apps/scheduler/app/api/scheduler/connections/route.ts
new file mode 100644
index 0000000000..c4be65ab34
--- /dev/null
+++ b/apps/scheduler/app/api/scheduler/connections/route.ts
@@ -0,0 +1,12 @@
+import { NextResponse, type NextRequest } from "next/server";
+
+import { requireSchedulerSession } from "@scheduler/lib/scheduler/auth";
+import { getConnections } from "@scheduler/lib/scheduler/service";
+
+export const dynamic = "force-dynamic";
+
+export async function GET(request: NextRequest) {
+  const auth = await requireSchedulerSession(request);
+  if ("response" in auth) return auth.response;
+  return NextResponse.json(await getConnections(Number(auth.session.user.id)));
+}
diff --git a/apps/scheduler/app/api/scheduler/meetings/route.ts b/apps/scheduler/app/api/scheduler/meetings/route.ts
new file mode 100644
index 0000000000..801425d71a
--- /dev/null
+++ b/apps/scheduler/app/api/scheduler/meetings/route.ts
@@ -0,0 +1,41 @@
+import { NextResponse, type NextRequest } from "next/server";
+import { ZodError } from "zod";
+
+import { requireSchedulerSession } from "@scheduler/lib/scheduler/auth";
+import { createMeeting, listMeetings } from "@scheduler/lib/scheduler/service";
+
+export const dynamic = "force-dynamic";
+
+export async function GET(request: NextRequest) {
+  const auth = await requireSchedulerSession(request);
+  if ("response" in auth) return auth.response;
+  return NextResponse.json(await listMeetings(Number(auth.session.user.id)));
+}
+
+export async function POST(request: NextRequest) {
+  const auth = await requireSchedulerSession(request);
+  if ("response" in auth) return auth.response;
+
+  let body: unknown;
+  try {
+    body = await request.json();
+  } catch {
+    return NextResponse.json({ error: "INVALID_JSON" }, { status: 400 });
+  }
+
+  try {
+    const result = await createMeeting(Number(auth.session.user.id), body);
+    if (result.status === "not_implemented") {
+      return NextResponse.json(result, { status: 501 });
+    }
+    return NextResponse.json(result, { status: 201 });
+  } catch (error) {
+    if (error instanceof ZodError) {
+      return NextResponse.json({ error: "VALIDATION_FAILED", issues: error.issues }, { status: 400 });
+    }
+    if (error instanceof Error && error.message === "ORGANIZER_NOT_IN_ATTENDEES") {
+      return NextResponse.json({ error: "ORGANIZER_NOT_IN_ATTENDEES" }, { status: 400 });
+    }
+    throw error;
+  }
+}
diff --git a/apps/scheduler/app/api/scheduler/schedule/route.ts b/apps/scheduler/app/api/scheduler/schedule/route.ts
new file mode 100644
index 0000000000..91c6bc3c34
--- /dev/null
+++ b/apps/scheduler/app/api/scheduler/schedule/route.ts
@@ -0,0 +1,35 @@
+import { NextResponse, type NextRequest } from "next/server";
+import { ZodError } from "zod";
+
+import { requireSchedulerSession } from "@scheduler/lib/scheduler/auth";
+import { getSchedule, updateSchedule } from "@scheduler/lib/scheduler/service";
+
+export const dynamic = "force-dynamic";
+
+export async function GET(request: NextRequest) {
+  const auth = await requireSchedulerSession(request);
+  if ("response" in auth) return auth.response;
+  return NextResponse.json(await getSchedule(Number(auth.session.user.id)));
+}
+
+export async function PUT(request: NextRequest) {
+  const auth = await requireSchedulerSession(request);
+  if ("response" in auth) return auth.response;
+
+  let body: unknown;
+  try {
+    body = await request.json();
+  } catch {
+    return NextResponse.json({ error: "INVALID_JSON" }, { status: 400 });
+  }
+
+  try {
+    const schedule = await updateSchedule(Number(auth.session.user.id), body);
+    return NextResponse.json(schedule);
+  } catch (error) {
+    if (error instanceof ZodError) {
+      return NextResponse.json({ error: "VALIDATION_FAILED", issues: error.issues }, { status: 400 });
+    }
+    throw error;
+  }
+}
diff --git a/apps/scheduler/app/api/scheduler/team/route.ts b/apps/scheduler/app/api/scheduler/team/route.ts
new file mode 100644
index 0000000000..848374ec43
--- /dev/null
+++ b/apps/scheduler/app/api/scheduler/team/route.ts
@@ -0,0 +1,12 @@
+import { NextResponse, type NextRequest } from "next/server";
+
+import { requireSchedulerSession } from "@scheduler/lib/scheduler/auth";
+import { getTeamContext } from "@scheduler/lib/scheduler/service";
+
+export const dynamic = "force-dynamic";
+
+export async function GET(request: NextRequest) {
+  const auth = await requireSchedulerSession(request);
+  if ("response" in auth) return auth.response;
+  return NextResponse.json(await getTeamContext(Number(auth.session.user.id)));
+}
diff --git a/apps/scheduler/lib/scheduler/auth.ts b/apps/scheduler/lib/scheduler/auth.ts
new file mode 100644
index 0000000000..476f434c31
--- /dev/null
+++ b/apps/scheduler/lib/scheduler/auth.ts
@@ -0,0 +1,23 @@
+import { getServerSession } from "@calcom/features/auth/lib/getServerSession";
+import type { NextRequest } from "next/server";
+import { NextResponse } from "next/server";
+
+import { buildLegacyRequest } from "./legacy-request";
+
+export async function getSchedulerSession(request: NextRequest) {
+  return getServerSession({ req: buildLegacyRequest(request) });
+}
+
+/**
+ * Returns either `{ session }` for an authenticated viewer, or `{ response }`
+ * carrying a 401 the route handler should return directly.
+ */
+export async function requireSchedulerSession(request: NextRequest) {
+  const session = await getSchedulerSession(request);
+  if (!session?.user?.id) {
+    return {
+      response: NextResponse.json({ error: "AUTHENTIK_LOGIN_REQUIRED" }, { status: 401 }),
+    };
+  }
+  return { session };
+}
diff --git a/apps/scheduler/lib/scheduler/demo-data.ts b/apps/scheduler/lib/scheduler/demo-data.ts
new file mode 100644
index 0000000000..5686f61673
--- /dev/null
+++ b/apps/scheduler/lib/scheduler/demo-data.ts
@@ -0,0 +1,114 @@
+import type {
+  BusyBlock,
+  MeetingDraft,
+  SchedulerSchedule,
+  SchedulerUser,
+  WeeklyRange,
+} from "./types";
+
+/**
+ * Deterministic fallback fixtures used ONLY when `SCHEDULER_DEMO_MODE === "1"`.
+ * No DB access is performed in demo mode. Day numbers follow `Date.getUTCDay()`
+ * (Sun=0 .. Sat=6), so Mon–Fri == 1..5.
+ */
+
+export const demoUsers: SchedulerUser[] = [
+  { id: 1, name: "Zach Sharma", email: "zach@vynte.local", timeZone: "America/Denver" },
+  { id: 2, name: "Maya Chen", email: "maya@vynte.local", timeZone: "America/Denver" },
+  { id: 3, name: "Jordan Lee", email: "jordan@vynte.local", timeZone: "America/Denver" },
+];
+
+const WORKDAY_RANGES: WeeklyRange[] = [1, 2, 3, 4, 5].map((day) => ({
+  day,
+  enabled: true,
+  startTime: "09:00",
+  endTime: "17:00",
+}));
+
+const WEEKEND_RANGES: WeeklyRange[] = [0, 6].map((day) => ({
+  day,
+  enabled: false,
+  startTime: "09:00",
+  endTime: "17:00",
+}));
+
+function demoWeekly(): WeeklyRange[] {
+  return [...WEEKEND_RANGES.slice(0, 1), ...WORKDAY_RANGES, ...WEEKEND_RANGES.slice(1)];
+}
+
+export const demoSchedules: SchedulerSchedule[] = demoUsers.map((user, index) => ({
+  id: index + 1,
+  userId: user.id,
+  timeZone: user.timeZone,
+  weekly: demoWeekly(),
+  overrides: [],
+}));
+
+export const demoBusyBlocks: BusyBlock[] = [
+  {
+    id: "demo-busy-1",
+    userId: 1,
+    start: "2026-06-15T16:00:00.000Z",
+    end: "2026-06-15T17:00:00.000Z",
+    title: "Zach 1:1",
+    source: "internal",
+  },
+  {
+    id: "demo-busy-2",
+    userId: 2,
+    start: "2026-06-15T18:00:00.000Z",
+    end: "2026-06-15T19:00:00.000Z",
+    title: "Maya focus block",
+    source: "internal",
+  },
+  {
+    id: "demo-busy-3",
+    userId: 3,
+    start: "2026-06-16T15:30:00.000Z",
+    end: "2026-06-16T16:30:00.000Z",
+    title: "Jordan external",
+    source: "external",
+  },
+];
+
+export type DemoConnection = {
+  type: string;
+  appId: string;
+  category: string;
+  connected: boolean;
+};
+
+export const demoConnectionsByUser: Record<number, DemoConnection[]> = {
+  1: [
+    { type: "google_calendar", appId: "google-calendar", category: "calendar", connected: true },
+    { type: "google_video", appId: "google-meet", category: "conferencing", connected: true },
+  ],
+  2: [{ type: "office365_calendar", appId: "office365-calendar", category: "calendar", connected: true }],
+  3: [],
+};
+
+export type DemoMeeting = {
+  id: number;
+  uid: string;
+  title: string;
+  organizerId: number;
+  attendeeIds: number[];
+  start: string;
+  end: string;
+  location: string | null;
+};
+
+export const demoMeetings: DemoMeeting[] = [
+  {
+    id: 9001,
+    uid: "demo-meeting-9001",
+    title: "Weekly sync",
+    organizerId: 1,
+    attendeeIds: [1, 2, 3],
+    start: "2026-06-15T17:00:00.000Z",
+    end: "2026-06-15T17:30:00.000Z",
+    location: "integrations:google:meet",
+  },
+];
+
+export { type MeetingDraft };
diff --git a/apps/scheduler/lib/scheduler/legacy-request.ts b/apps/scheduler/lib/scheduler/legacy-request.ts
new file mode 100644
index 0000000000..5a5fc8ea8e
--- /dev/null
+++ b/apps/scheduler/lib/scheduler/legacy-request.ts
@@ -0,0 +1,20 @@
+import type { NextApiRequest } from "next";
+import type { NextRequest } from "next/server";
+
+/**
+ * Adapts an App Router `NextRequest` into the `NextApiRequest`-shaped object that
+ * Cal's `getServerSession` (via `next-auth/jwt` `getToken`) expects: a plain cookies
+ * map, a plain headers map, plus `method` and `url`.
+ */
+export function buildLegacyRequest(request: NextRequest): NextApiRequest {
+  const cookies = Object.fromEntries(
+    request.cookies.getAll().map((cookie) => [cookie.name, cookie.value])
+  );
+  const headers = Object.fromEntries(request.headers.entries());
+  return {
+    cookies,
+    headers,
+    method: request.method,
+    url: request.nextUrl.pathname + request.nextUrl.search,
+  } as unknown as NextApiRequest;
+}
diff --git a/apps/scheduler/lib/scheduler/service.ts b/apps/scheduler/lib/scheduler/service.ts
new file mode 100644
index 0000000000..6e1c19e2e5
--- /dev/null
+++ b/apps/scheduler/lib/scheduler/service.ts
@@ -0,0 +1,468 @@
+import prisma from "@calcom/prisma";
+
+import { computeMutualSlots } from "./availability";
+import {
+  demoBusyBlocks,
+  demoConnectionsByUser,
+  demoMeetings,
+  demoSchedules,
+  demoUsers,
+  type DemoConnection,
+} from "./demo-data";
+import { filterBusyBlocksForViewer } from "./privacy";
+import type {
+  BusyBlock,
+  MutualSlot,
+  PublicBusyBlock,
+  SchedulerSchedule,
+  SchedulerUser,
+  WeeklyRange,
+} from "./types";
+import { z } from "zod";
+
+const DEFAULT_TIME_ZONE = "America/Denver";
+
+function isDemoMode(): boolean {
+  return process.env.SCHEDULER_DEMO_MODE === "1";
+}
+
+// ---------------------------------------------------------------------------
+// Mappers
+// ---------------------------------------------------------------------------
+
+type DbUser = {
+  id: number;
+  name: string | null;
+  email: string;
+  timeZone: string;
+};
+
+function mapUser(user: DbUser): SchedulerUser {
+  return {
+    id: user.id,
+    name: user.name ?? user.email,
+    email: user.email,
+    timeZone: user.timeZone ?? DEFAULT_TIME_ZONE,
+  };
+}
+
+/** Cal stores Availability start/end as a Time-only value; we read the UTC clock time. */
+function timeToHhMm(value: Date): string {
+  const hours = String(value.getUTCHours()).padStart(2, "0");
+  const minutes = String(value.getUTCMinutes()).padStart(2, "0");
+  return `${hours}:${minutes}`;
+}
+
+type DbAvailability = {
+  days: number[];
+  startTime: Date;
+  endTime: Date;
+  date: Date | null;
+};
+
+/**
+ * Builds a SchedulerSchedule from a user's Schedule + Availability rows.
+ * Weekly rows have `date === null` and one-or-more `days`; override rows have a `date`.
+ */
+function buildSchedule(
+  userId: number,
+  schedule: { id: number; timeZone: string | null; availability: DbAvailability[] } | null,
+  fallbackTimeZone: string
+): SchedulerSchedule {
+  const weekly: WeeklyRange[] = [];
+  const overrides: SchedulerSchedule["overrides"] = [];
+
+  for (const row of schedule?.availability ?? []) {
+    if (row.date) {
+      overrides.push({
+        date: row.date.toISOString().slice(0, 10),
+        unavailable: false,
+        startTime: timeToHhMm(row.startTime),
+        endTime: timeToHhMm(row.endTime),
+      });
+      continue;
+    }
+    for (const day of row.days) {
+      weekly.push({
+        day,
+        enabled: true,
+        startTime: timeToHhMm(row.startTime),
+        endTime: timeToHhMm(row.endTime),
+      });
+    }
+  }
+
+  return {
+    id: schedule?.id ?? null,
+    userId,
+    timeZone: schedule?.timeZone ?? fallbackTimeZone,
+    weekly,
+    overrides,
+  };
+}
+
+const USER_SELECT = { id: true, name: true, email: true, timeZone: true } as const;
+
+const SCHEDULE_INCLUDE = {
+  availability: {
+    select: { days: true, startTime: true, endTime: true, date: true },
+  },
+} as const;
+
+// ---------------------------------------------------------------------------
+// Team
+// ---------------------------------------------------------------------------
+
+export async function getTeamContext(
+  viewerId: number
+): Promise<{ viewer: SchedulerUser; team: SchedulerUser[] }> {
+  if (isDemoMode()) {
+    const viewer = demoUsers.find((user) => user.id === viewerId) ?? demoUsers[0];
+    return { viewer, team: demoUsers };
+  }
+
+  // Single-team model: every active (unlocked) user is a teammate.
+  const users = await prisma.user.findMany({
+    where: { locked: false },
+    select: USER_SELECT,
+    orderBy: { id: "asc" },
+  });
+
+  const team = users.map(mapUser);
+  const viewer = team.find((user) => user.id === viewerId) ?? mapUser(await requireUser(viewerId));
+  return { viewer, team };
+}
+
+async function requireUser(userId: number): Promise<DbUser> {
+  const user = await prisma.user.findUnique({ where: { id: userId }, select: USER_SELECT });
+  if (!user) {
+    throw new Error(`Scheduler user not found: ${userId}`);
+  }
+  return user;
+}
+
+// ---------------------------------------------------------------------------
+// Schedule (read/write)
+// ---------------------------------------------------------------------------
+
+async function loadSchedule(userId: number): Promise<SchedulerSchedule> {
+  const user = await requireUser(userId);
+  const schedule = await prisma.schedule.findFirst({
+    where: { userId },
+    orderBy: { id: "asc" },
+    select: { id: true, timeZone: true, ...SCHEDULE_INCLUDE },
+  });
+  return buildSchedule(userId, schedule, user.timeZone ?? DEFAULT_TIME_ZONE);
+}
+
+export async function getSchedule(userId: number): Promise<SchedulerSchedule> {
+  if (isDemoMode()) {
+    return demoSchedules.find((schedule) => schedule.userId === userId) ?? demoSchedules[0];
+  }
+  return loadSchedule(userId);
+}
+
+const hhMm = z.string().regex(/^([01]\d|2[0-3]):[0-5]\d$/, "Expected HH:MM time");
+
+const weeklyRangeSchema = z.object({
+  day: z.number().int().min(0).max(6),
+  enabled: z.boolean(),
+  startTime: hhMm,
+  endTime: hhMm,
+});
+
+const dateOverrideSchema = z.object({
+  date: z.string().regex(/^\d{4}-\d{2}-\d{2}$/, "Expected YYYY-MM-DD date"),
+  unavailable: z.boolean(),
+  startTime: hhMm.optional(),
+  endTime: hhMm.optional(),
+});
+
+const updateScheduleSchema = z.object({
+  timeZone: z.string().min(1).optional(),
+  weekly: z.array(weeklyRangeSchema),
+  overrides: z.array(dateOverrideSchema).default([]),
+});
+
+/** Parses an "HH:MM" string into a 1970-01-01 UTC Date for the Time column. */
+function hhMmToTime(value: string): Date {
+  const [hours, minutes] = value.split(":").map(Number);
+  return new Date(Date.UTC(1970, 0, 1, hours, minutes, 0, 0));
+}
+
+export async function updateSchedule(userId: number, body: unknown): Promise<SchedulerSchedule> {
+  const parsed = updateScheduleSchema.parse(body);
+
+  if (isDemoMode()) {
+    // Demo mode is read-only; echo the parsed schedule back without persisting.
+    return {
+      id: null,
+      userId,
+      timeZone: parsed.timeZone ?? DEFAULT_TIME_ZONE,
+      weekly: parsed.weekly,
+      overrides: parsed.overrides,
+    };
+  }
+
+  const user = await requireUser(userId);
+  const timeZone = parsed.timeZone ?? user.timeZone ?? DEFAULT_TIME_ZONE;
+
+  const existing = await prisma.schedule.findFirst({
+    where: { userId },
+    orderBy: { id: "asc" },
+    select: { id: true },
+  });
+
+  const availabilityRows = [
+    ...parsed.weekly
+      .filter((range) => range.enabled)
+      .map((range) => ({
+        days: [range.day],
+        startTime: hhMmToTime(range.startTime),
+        endTime: hhMmToTime(range.endTime),
+        date: null as Date | null,
+        userId,
+      })),
+    ...parsed.overrides
+      .filter((override) => !override.unavailable && override.startTime && override.endTime)
+      .map((override) => ({
+        days: [] as number[],
+        startTime: hhMmToTime(override.startTime as string),
+        endTime: hhMmToTime(override.endTime as string),
+        date: new Date(`${override.date}T00:00:00.000Z`),
+        userId,
+      })),
+  ];
+
+  // Replace the schedule's availability atomically; immutable from the caller's view.
+  const scheduleId = await prisma.$transaction(async (tx) => {
+    const schedule = existing
+      ? await tx.schedule.update({
+          where: { id: existing.id },
+          data: { timeZone },
+          select: { id: true },
+        })
+      : await tx.schedule.create({
+          data: { userId, name: "Working Hours", timeZone },
+          select: { id: true },
+        });
+
+    await tx.availability.deleteMany({ where: { scheduleId: schedule.id } });
+    if (availabilityRows.length > 0) {
+      await tx.availability.createMany({
+        data: availabilityRows.map((row) => ({ ...row, scheduleId: schedule.id })),
+      });
+    }
+    return schedule.id;
+  });
+
+  void scheduleId;
+  return loadSchedule(userId);
+}
+
+// ---------------------------------------------------------------------------
+// Connections (no secrets exposed)
+// ---------------------------------------------------------------------------
+
+export type SchedulerConnection = {
+  type: string;
+  appId: string | null;
+  category: string;
+  connected: boolean;
+};
+
+export async function getConnections(
+  userId: number
+): Promise<{ connections: SchedulerConnection[] }> {
+  if (isDemoMode()) {
+    const demo: DemoConnection[] = demoConnectionsByUser[userId] ?? [];
+    return {
+      connections: demo.map((connection) => ({
+        type: connection.type,
+        appId: connection.appId,
+        category: connection.category,
+        connected: connection.connected,
+      })),
+    };
+  }
+
+  // Only non-secret metadata is selected: `key`/`encryptedKey` are never read.
+  const credentials = await prisma.credential.findMany({
+    where: { userId },
+    select: {
+      type: true,
+      appId: true,
+      invalid: true,
+      app: { select: { categories: true } },
+    },
+    orderBy: { id: "asc" },
+  });
+
+  const connections: SchedulerConnection[] = credentials.map((credential) => ({
+    type: credential.type,
+    appId: credential.appId,
+    category: credential.app?.categories?.[0] ?? "other",
+    connected: credential.invalid !== true,
+  }));
+
+  return { connections };
+}
+
+// ---------------------------------------------------------------------------
+// Availability
+// ---------------------------------------------------------------------------
+
+async function bookingsToBusyBlocks(
+  attendeeIds: number[],
+  rangeStart: string,
+  rangeEnd: string
+): Promise<BusyBlock[]> {
+  const bookings = await prisma.booking.findMany({
+    where: {
+      userId: { in: attendeeIds },
+      status: { in: ["ACCEPTED", "PENDING"] },
+      startTime: { lt: new Date(rangeEnd) },
+      endTime: { gt: new Date(rangeStart) },
+    },
+    select: { id: true, userId: true, title: true, startTime: true, endTime: true },
+    orderBy: { startTime: "asc" },
+  });
+
+  return bookings
+    .filter((booking): booking is typeof booking & { userId: number } => booking.userId !== null)
+    .map((booking) => ({
+      id: `booking-${booking.id}`,
+      userId: booking.userId,
+      start: booking.startTime.toISOString(),
+      end: booking.endTime.toISOString(),
+      title: booking.title,
+      source: "internal" as const,
+    }));
+}
+
+export async function getAvailability(
+  viewerId: number,
+  attendeeIds: number[],
+  rangeStart: string,
+  rangeEnd: string,
+  durationMinutes: number
+): Promise<{ busy: PublicBusyBlock[]; mutualSlots: MutualSlot[] }> {
+  if (isDemoMode()) {
+    const relevant = demoBusyBlocks.filter((block) => attendeeIds.includes(block.userId));
+    const schedules = demoSchedules.filter((schedule) => attendeeIds.includes(schedule.userId));
+    const mutualSlots = computeMutualSlots({
+      schedules,
+      busy: relevant,
+      rangeStart,
+      rangeEnd,
+      durationMinutes,
+    });
+    return { busy: filterBusyBlocksForViewer(relevant, viewerId), mutualSlots };
+  }
+
+  const busyBlocks = await bookingsToBusyBlocks(attendeeIds, rangeStart, rangeEnd);
+  const schedules = await Promise.all(attendeeIds.map((id) => loadSchedule(id)));
+
+  const mutualSlots = computeMutualSlots({
+    schedules,
+    busy: busyBlocks,
+    rangeStart,
+    rangeEnd,
+    durationMinutes,
+  });
+
+  return { busy: filterBusyBlocksForViewer(busyBlocks, viewerId), mutualSlots };
+}
+
+// ---------------------------------------------------------------------------
+// Meetings
+// ---------------------------------------------------------------------------
+
+export type SchedulerMeeting = {
+  id: number;
+  uid: string;
+  title: string;
+  organizerId: number | null;
+  attendeeIds: number[];
+  start: string;
+  end: string;
+  location: string | null;
+};
+
+export async function listMeetings(
+  viewerId: number
+): Promise<{ meetings: SchedulerMeeting[] }> {
+  if (isDemoMode()) {
+    const meetings = demoMeetings
+      .filter((meeting) => meeting.attendeeIds.includes(viewerId))
+      .map((meeting) => ({
+        id: meeting.id,
+        uid: meeting.uid,
+        title: meeting.title,
+        organizerId: meeting.organizerId,
+        attendeeIds: meeting.attendeeIds,
+        start: meeting.start,
+        end: meeting.end,
+        location: meeting.location,
+      }));
+    return { meetings };
+  }
+
+  const bookings = await prisma.booking.findMany({
+    where: { userId: viewerId, status: { in: ["ACCEPTED", "PENDING"] } },
+    select: { id: true, uid: true, title: true, userId: true, startTime: true, endTime: true, location: true },
+    orderBy: { startTime: "desc" },
+    take: 100,
+  });
+
+  const meetings: SchedulerMeeting[] = bookings.map((booking) => ({
+    id: booking.id,
+    uid: booking.uid,
+    title: booking.title,
+    organizerId: booking.userId,
+    attendeeIds: booking.userId !== null ? [booking.userId] : [],
+    start: booking.startTime.toISOString(),
+    end: booking.endTime.toISOString(),
+    location: booking.location,
+  }));
+
+  return { meetings };
+}
+
+const createMeetingSchema = z.object({
+  title: z.string().min(1),
+  attendeeIds: z.array(z.number().int().positive()).min(1),
+  start: z.string().datetime(),
+  durationMinutes: z.number().int().positive(),
+  location: z.string().optional(),
+  conferencing: z.enum(["none", "provider"]).optional(),
+});
+
+export type CreateMeetingResult =
+  | { status: "created"; meeting: SchedulerMeeting }
+  | { status: "not_implemented"; reason: string };
+
+/**
+ * v1 decision: we DO NOT create a real Cal `Booking` here.
+ *
+ * Although the `Booking` model only marks `uid`/`title`/`startTime`/`endTime` as
+ * NOT NULL, a booking that Cal's own UI, calendar sync, and notification pipeline
+ * can actually consume requires an `eventTypeId`, `Attendee` rows, and structured
+ * `responses` JSON. Synthesizing those from the table-free data we have would mean
+ * guessing values, producing fragile/half-valid bookings. Per the plan, we instead
+ * return the explicit `CAL_BOOKING_SERVICE_BOUNDARY` not_implemented boundary, which
+ * the route surfaces as HTTP 501.
+ */
+export async function createMeeting(
+  viewerId: number,
+  body: unknown
+): Promise<CreateMeetingResult> {
+  const draft = createMeetingSchema.parse(body);
+
+  if (!draft.attendeeIds.includes(viewerId)) {
+    throw new Error("ORGANIZER_NOT_IN_ATTENDEES");
+  }
+
+  // See function doc: intentionally a v1 boundary rather than a fragile booking.
+  return { status: "not_implemented", reason: "CAL_BOOKING_SERVICE_BOUNDARY" };
+}