diff --git a/src/lib/webrtc/broadcaster.ts b/src/lib/webrtc/broadcaster.ts
new file mode 100644
index 0000000..fa4b7f6
--- /dev/null
+++ b/src/lib/webrtc/broadcaster.ts
@@ -0,0 +1,127 @@
+import { supabase } from '@/integrations/supabase/client';
+import {
+  generateRoomCode,
+  joinSignalingChannel,
+  sendSignal,
+  ICE_SERVERS,
+  type SignalMessage,
+} from './signaling';
+import type { RealtimeChannel } from '@supabase/supabase-js';
+
+export interface BroadcasterHandle {
+  code: string;
+  stop: () => Promise<void>;
+  onViewerCountChange: (cb: (n: number) => void) => () => void;
+}
+
+const MAX_VIEWERS = 5;
+
+/**
+ * Starts broadcasting a MediaStream under a fresh room code.
+ * Returns a handle exposing the code and a stop() to teardown.
+ */
+export async function startBroadcast(stream: MediaStream): Promise<BroadcasterHandle> {
+  const code = generateRoomCode();
+
+  // Insert room
+  const { error: insErr } = await supabase.from('share_rooms').insert({ code, is_active: true });
+  if (insErr) throw new Error(`Falha ao criar sala: ${insErr.message}`);
+
+  const peers = new Map<string, RTCPeerConnection>();
+  const listeners = new Set<(n: number) => void>();
+  const notify = () => listeners.forEach((cb) => cb(peers.size));
+
+  let channel: RealtimeChannel | null = null;
+
+  const handleMessage = async (msg: SignalMessage) => {
+    if (msg.type === 'viewer-join') {
+      if (peers.size >= MAX_VIEWERS) return;
+      const pc = new RTCPeerConnection({ iceServers: ICE_SERVERS });
+      peers.set(msg.viewerId, pc);
+
+      stream.getTracks().forEach((t) => pc.addTrack(t, stream));
+
+      pc.onicecandidate = (ev) => {
+        if (ev.candidate && channel) {
+          sendSignal(channel, {
+            type: 'ice',
+            viewerId: msg.viewerId,
+            from: 'broadcaster',
+            candidate: ev.candidate.toJSON(),
+          });
+        }
+      };
+
+      pc.onconnectionstatechange = () => {
+        if (['failed', 'closed', 'disconnected'].includes(pc.connectionState)) {
+          peers.delete(msg.viewerId);
+          pc.close();
+          notify();
+          updateViewerCount(code, peers.size);
+        }
+      };
+
+      const offer = await pc.createOffer();
+      await pc.setLocalDescription(offer);
+      if (channel) {
+        sendSignal(channel, { type: 'offer', viewerId: msg.viewerId, sdp: offer });
+      }
+      notify();
+      updateViewerCount(code, peers.size);
+    } else if (msg.type === 'answer') {
+      const pc = peers.get(msg.viewerId);
+      if (pc && pc.signalingState !== 'stable') {
+        await pc.setRemoteDescription(msg.sdp);
+      }
+    } else if (msg.type === 'ice' && msg.from === 'viewer') {
+      const pc = peers.get(msg.viewerId);
+      if (pc) {
+        try {
+          await pc.addIceCandidate(msg.candidate);
+        } catch (e) {
+          console.warn('[broadcaster] addIceCandidate failed', e);
+        }
+      }
+    } else if (msg.type === 'viewer-leave') {
+      const pc = peers.get(msg.viewerId);
+      if (pc) {
+        pc.close();
+        peers.delete(msg.viewerId);
+        notify();
+        updateViewerCount(code, peers.size);
+      }
+    }
+  };
+
+  channel = joinSignalingChannel(code, handleMessage);
+
+  // Stop when the underlying stream ends
+  stream.getTracks().forEach((t) => {
+    t.addEventListener('ended', () => stop());
+  });
+
+  let stopped = false;
+  const stop = async () => {
+    if (stopped) return;
+    stopped = true;
+    peers.forEach((pc) => pc.close());
+    peers.clear();
+    notify();
+    if (channel) await supabase.removeChannel(channel);
+    await supabase.from('share_rooms').update({ is_active: false, viewer_count: 0 }).eq('code', code);
+  };
+
+  return {
+    code,
+    stop,
+    onViewerCountChange: (cb) => {
+      listeners.add(cb);
+      cb(peers.size);
+      return () => listeners.delete(cb);
+    },
+  };
+}
+
+async function updateViewerCount(code: string, n: number) {
+  await supabase.from('share_rooms').update({ viewer_count: n }).eq('code', code);
+}
diff --git a/src/lib/webrtc/signaling.ts b/src/lib/webrtc/signaling.ts
new file mode 100644
index 0000000..ab48542
--- /dev/null
+++ b/src/lib/webrtc/signaling.ts
@@ -0,0 +1,40 @@
+import { supabase } from '@/integrations/supabase/client';
+import type { RealtimeChannel } from '@supabase/supabase-js';
+
+export type SignalMessage =
+  | { type: 'viewer-join'; viewerId: string }
+  | { type: 'viewer-leave'; viewerId: string }
+  | { type: 'offer'; viewerId: string; sdp: RTCSessionDescriptionInit }
+  | { type: 'answer'; viewerId: string; sdp: RTCSessionDescriptionInit }
+  | { type: 'ice'; viewerId: string; from: 'broadcaster' | 'viewer'; candidate: RTCIceCandidateInit };
+
+export function joinSignalingChannel(
+  code: string,
+  onMessage: (msg: SignalMessage) => void,
+): RealtimeChannel {
+  const channel = supabase.channel(`share:${code}`, {
+    config: { broadcast: { self: false, ack: false } },
+  });
+
+  channel
+    .on('broadcast', { event: 'signal' }, ({ payload }) => onMessage(payload as SignalMessage))
+    .subscribe();
+
+  return channel;
+}
+
+export function sendSignal(channel: RealtimeChannel, msg: SignalMessage) {
+  return channel.send({ type: 'broadcast', event: 'signal', payload: msg });
+}
+
+export function generateRoomCode(): string {
+  const chars = 'ABCDEFGHJKLMNPQRSTUVWXYZ23456789'; // unambiguous
+  let out = '';
+  for (let i = 0; i < 6; i++) out += chars[Math.floor(Math.random() * chars.length)];
+  return out;
+}
+
+export const ICE_SERVERS: RTCIceServer[] = [
+  { urls: 'stun:stun.l.google.com:19302' },
+  { urls: 'stun:stun1.l.google.com:19302' },
+];
diff --git a/src/lib/webrtc/viewer.ts b/src/lib/webrtc/viewer.ts
new file mode 100644
index 0000000..fd0d329
--- /dev/null
+++ b/src/lib/webrtc/viewer.ts
@@ -0,0 +1,89 @@
+import {
+  joinSignalingChannel,
+  sendSignal,
+  ICE_SERVERS,
+  type SignalMessage,
+} from './signaling';
+import type { RealtimeChannel } from '@supabase/supabase-js';
+
+export interface ViewerHandle {
+  stop: () => Promise<void>;
+}
+
+/**
+ * Connects to a broadcaster's room and renders the incoming stream into the given <video>.
+ */
+export async function joinAsViewer(
+  code: string,
+  videoEl: HTMLVideoElement,
+  onState: (s: 'connecting' | 'waiting' | 'live' | 'error', detail?: string) => void,
+): Promise<ViewerHandle> {
+  const viewerId = crypto.randomUUID();
+  let pc: RTCPeerConnection | null = null;
+  let channel: RealtimeChannel | null = null;
+
+  onState('connecting');
+
+  const handleMessage = async (msg: SignalMessage) => {
+    if (msg.type === 'offer' && msg.viewerId === viewerId) {
+      pc = new RTCPeerConnection({ iceServers: ICE_SERVERS });
+
+      pc.ontrack = (ev) => {
+        videoEl.srcObject = ev.streams[0];
+        videoEl.play().catch(() => {/* autoplay may need user gesture */});
+        onState('live');
+      };
+
+      pc.onicecandidate = (ev) => {
+        if (ev.candidate && channel) {
+          sendSignal(channel, {
+            type: 'ice',
+            viewerId,
+            from: 'viewer',
+            candidate: ev.candidate.toJSON(),
+          });
+        }
+      };
+
+      pc.onconnectionstatechange = () => {
+        if (pc && ['failed', 'disconnected'].includes(pc.connectionState)) {
+          onState('error', 'Conexão perdida');
+        }
+      };
+
+      await pc.setRemoteDescription(msg.sdp);
+      const answer = await pc.createAnswer();
+      await pc.setLocalDescription(answer);
+      if (channel) sendSignal(channel, { type: 'answer', viewerId, sdp: answer });
+    } else if (msg.type === 'ice' && msg.viewerId === viewerId && msg.from === 'broadcaster') {
+      if (pc) {
+        try {
+          await pc.addIceCandidate(msg.candidate);
+        } catch (e) {
+          console.warn('[viewer] addIceCandidate failed', e);
+        }
+      }
+    }
+  };
+
+  channel = joinSignalingChannel(code, handleMessage);
+
+  // Wait a tick for subscribe, then announce join
+  setTimeout(() => {
+    if (channel) {
+      sendSignal(channel, { type: 'viewer-join', viewerId });
+      onState('waiting');
+    }
+  }, 600);
+
+  const stop = async () => {
+    if (channel) {
+      try { sendSignal(channel, { type: 'viewer-leave', viewerId }); } catch {}
+      const { supabase } = await import('@/integrations/supabase/client');
+      await supabase.removeChannel(channel);
+    }
+    if (pc) pc.close();
+  };
+
+  return { stop };
+}