Add multi-bot voice architecture with audio channels and progressive updates

COORDINATION_PATTERNS.md

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+# Coordination Patterns for Music Playback
+
+> **Status**: Implemented (Broadcast Architecture)  
+> **Last Updated**: December 2025
+
+## Overview
+
+This document describes the coordination patterns used in the music playback system, based on the broadcast architecture with `IAudioBroadcast` and `IAudioSink` contracts.
+
+## Architecture Summary
+
+```
+┌─────────────────────────────────────────────────────────┐
+│                 plugin-music-player                      │
+│   MusicQueue → Broadcast (IAudioBroadcast) → Multiplex  │
+└─────────────────────────────────────────────────────────┘
+                          │
+          Events: 'track:started', 'track:finished'
+          Method: subscribe() / unsubscribe()
+                          │
+┌─────────────────────────▼───────────────────────────────┐
+│                  plugin-discord                          │
+│   DiscordAudioSink (IAudioSink) ← feed(stream)          │
+│   Events: 'statusChange'                                 │
+└─────────────────────────────────────────────────────────┘
+```
+
+## Pattern 1: Contract-Based Decoupling
+
+### Problem
+Plugins need to communicate without tight coupling.
+
+### Solution
+Define contracts (interfaces) that each plugin owns:
+
+```typescript
+// plugin-music-player owns IAudioBroadcast
+interface IAudioBroadcast {
+  subscribe(consumerId: string): AudioSubscription;
+  unsubscribe(consumerId: string): void;
+  feedAudio(stream: Readable, metadata?: AudioBroadcastMetadata): Promise<void>;
+  // ...
+}
+
+// plugin-discord owns IAudioSink  
+interface IAudioSink {
+  feed(stream: Readable): Promise<void>;
+  connect(channelId: string): Promise<void>;
+  disconnect(): Promise<void>;
+  // ...
+}
+```
+
+### Benefits
+- Plugins only depend on contracts, not implementations
+- Either plugin can be replaced or upgraded independently
+- Clear ownership boundaries
+
+## Pattern 2: Event-Based Coordination
+
+### Problem
+External plugins (radio, DJ) need to know when tracks start/finish.
+
+### Solution
+Use EventEmitter for state change notifications:
+
+```typescript
+// IAudioBroadcast emits events
+broadcast.on('track:started', (metadata) => {
+  console.log(`Now playing: ${metadata.title}`);
+});
+
+broadcast.on('track:finished', (metadata) => {
+  // Trigger next action
+});
+
+broadcast.on('silence:started', () => {
+  // Queue is empty
+});
+
+// IAudioSink emits status changes
+sink.on('statusChange', (status) => {
+  // 'connected' | 'disconnected' | 'connecting' | 'error'
+});
+```
+
+### Use Cases
+- Radio plugin listening for tracks to announce
+- DJ plugin waiting for track finish to add commentary
+- Web UI updating now-playing display
+
+## Pattern 3: Auto-Wiring via Service Discovery
+
+### Problem
+Plugins need to connect to each other at runtime.
+
+### Solution
+Use `runtime.getService()` for discovery and wire automatically:
+
+```typescript
+// In MusicService (plugin-music-player)
+async autoSubscribeDiscord(guildId: string, broadcast: IAudioBroadcast) {
+  const discordService = this.runtime.getService('discord');
+  if (!discordService) return; // Graceful degradation
+
+  const sink = discordService.getAudioSink(guildId);
+  if (!sink) return;
+
+  // Auto-wire on connection
+  sink.on('statusChange', async (status) => {
+    if (status === 'connected') {
+      const subscription = broadcast.subscribe(`discord-${guildId}`);
+      await sink.feed(subscription.stream);
+    }
+  });
+}
+```
+
+### Benefits
+- Zero manual configuration
+- Works when both plugins loaded
+- Gracefully degrades when one is missing
+
+## Pattern 4: Reconnection Handling
+
+### Problem
+Network hiccups cause Discord disconnections; playback should resume.
+
+### Solution
+Use `statusChange` events for automatic recovery:
+
+```typescript
+sink.on('statusChange', async (status) => {
+  if (status === 'connected') {
+    // Re-subscribe to get fresh stream from live point
+    const subscription = broadcast.subscribe(`discord-${guildId}`);
+    await sink.feed(subscription.stream);
+    logger.info('Discord reconnected, re-subscribed to broadcast');
+  }
+});
+```
+
+### Key Insight
+Re-subscribing gets the current position in the broadcast, not the beginning. This is because the broadcast is always "live" - like tuning into a radio station.
+
+## Pattern 5: Non-Blocking Multiplexing
+
+### Problem
+Slow consumers (laggy web clients) could block the main stream.
+
+### Solution
+Each consumer gets an independent `PassThrough` stream with backpressure handling:
+
+```typescript
+// In StreamMultiplexer
+source.on('data', (chunk) => {
+  for (const [id, consumer] of consumers) {
+    if (!consumer.write(chunk)) {
+      // Consumer buffer full - drop frame for this consumer
+      logger.debug(`Backpressure on ${id}, dropping chunk`);
+    }
+  }
+});
+```
+
+### Result
+- Discord playback unaffected by web client performance
+- Each consumer independent
+- No blocking the source stream
+
+## Pattern 6: Silence Injection
+
+### Problem
+Empty queue causes Discord voice connection timeout.
+
+### Solution
+`StreamCore` injects silence frames when no audio is being fed:
+
+```typescript
+// In StreamCore
+startSilence() {
+  this.silenceInterval = setInterval(() => {
+    this.output.write(OPUS_SILENCE_FRAME); // 10ms of silence
+  }, 10);
+}
+
+feed(stream: Readable) {
+  this.stopSilence(); // Real audio coming
+  stream.pipe(this.output, { end: false });
+  stream.on('end', () => this.startSilence());
+}
+```
+
+### Benefits
+- Voice connection stays alive indefinitely
+- Seamless transition when new tracks added
+- No manual connection management needed
+
+## Pattern Summary
+
+| Pattern | Use Case | Key Mechanism |
+|---------|----------|---------------|
+| **Contracts** | Plugin decoupling | IAudioBroadcast / IAudioSink |
+| **Events** | State notifications | EventEmitter |
+| **Auto-Wiring** | Runtime connection | runtime.getService() |
+| **Reconnection** | Resilience | statusChange event |
+| **Multiplexing** | Multiple consumers | PassThrough + backpressure |
+| **Silence** | Connection keep-alive | Interval-based frame injection |
+
+## Implementation Locations
+
+### This Package (plugin-discord)
+
+| Pattern | File |
+|---------|------|
+| IAudioSink | `src/contracts.ts` |
+| Discord sink | `src/sinks/discordAudioSink.ts` |
+
+### External Package (plugin-music-player)
+
+> **Note**: The following files are located in `packages/plugin-music-player/` within the monorepo.
+
+| Pattern | File |
+|---------|------|
+| IAudioBroadcast | `packages/plugin-music-player/src/contracts.ts` |
+| Auto-wiring | `packages/plugin-music-player/src/service.ts` |
+| Multiplexing | `packages/plugin-music-player/src/core/streamMultiplexer.ts` |
+| Silence injection | `packages/plugin-music-player/src/core/streamCore.ts` |
+
+## Related Documentation
+
+- [MUSIC_ARCHITECTURE.md](./MUSIC_ARCHITECTURE.md) - Full architecture overview
+- [plugin-music-player README](../plugin-music-player/README.md) - Usage guide