voice-subsystem-keeper

name	voice-subsystem-keeper
description	Work with DiscordPHP's voice subsystem — voice gateway protocol opcodes, encryption (VoiceGroupCrypto), voice packets, audio streaming, and Discord.php voice integration. Use when touching Voice/*, joinVoiceChannel, or voice encryption/packet logic.

Skill: voice-subsystem-keeper

Use this skill when work touches src/Discord/Voice/*, Discord::joinVoiceChannel(), voice event handlers in Discord.php, or anything involving audio encryption and packets.

Architecture overview

Voice support is split across three locations. Understand the boundary before touching any of them:

Location	What lives here
src/Discord/Voice/*	Internal protocol types: opcodes (Hello, Ready, Speaking), session description, voice packets, encryption classes and traits. These are pure data/crypto — no audio I/O.
src/Discord/Discord.php	Runtime integration: joinVoiceChannel(), voice state update handlers, voice server update handlers. This is where the external voice client is wired to gateway events.
discord-php-helpers/voice (external package)	Manager and VoiceClient: actual audio I/O, Opus encoding, UDP transport, stream management. DiscordPHP delegates audio work here.

Rule: do not blur these boundaries. Protocol types belong in Voice/*, audio I/O belongs in the external package, and wiring belongs in Discord.php.

Read in this order

1. src/Discord/Voice/VoiceGroupCrypto.php — encryption/decryption base class
2. src/Discord/Voice/VoiceGroupCryptoTrait.php — mixin providing group-based AEAD crypto
3. src/Discord/Voice/VoiceGroupCryptoInterface.php — contract
4. src/Discord/Voice/VoicePacket.php — encrypted RTP packet encapsulation
5. src/Discord/Voice/SessionDescription.php — session key and mode negotiation
6. src/Discord/Voice/Speaking.php, src/Discord/Voice/Hello.php, src/Discord/Voice/Ready.php, src/Discord/Voice/Resumed.php — voice gateway opcodes
7. src/Discord/Voice/Platform.php, src/Discord/Voice/Region.php — enum helpers
8. src/Discord/Discord.php — search for joinVoiceChannel, VOICE_STATE_UPDATE, VOICE_SERVER_UPDATE
9. src/Discord/Helpers/Buffer.php — writable stream for audio buffering (extends EventEmitter)

Core concepts

Voice gateway protocol

Discord voice uses a separate WebSocket gateway from the main gateway. The handshake sequence is:

1. Hello — server sends heartbeat interval
2. Identify — client sends token + session
3. Ready — server sends UDP endpoint + SSRC
4. Select Protocol — client sends chosen encryption mode
5. Session Description — server sends secret key
6. Speaking — sent before/after transmitting audio

The classes in src/Discord/Voice/ model these protocol steps as typed value objects.

Encryption

VoiceGroupCrypto provides AEAD encryption for RTP packets. It depends on libsodium (ext-sodium). The trait VoiceGroupCryptoTrait provides the implementation; concrete classes select the cipher mode (e.g., aead_xchacha20poly1305_ietf).

• LibSodiumNotFoundException is thrown at runtime if the extension is absent — do not suppress it
• Cipher mode is negotiated via SessionDescription

VoicePacket

VoicePacket encapsulates an encrypted RTP packet:

• SSRC identifies the audio source
• Sequence number and timestamp are required for RTP ordering
• The packet is encrypted before transmission using the session secret key

Audio I/O (external package)

discord-php-helpers/voice owns all audio work:

• Opus codec encoding/decoding
• UDP socket management
• OGG/Opus stream handling
• FFmpeg process integration

Do not replicate any of this in src/Discord/Voice/. If you need to add audio capability, contribute to the external package or wrap it.

Old* files

OldVoiceClient.php, OldBuffer.php, OldOggStream.php, OldOggPage.php, OldOpusHead.php, OldOpusTags.php, OldReceiveStream.php are legacy implementations. They are preserved for compatibility only.

Do not extend, copy patterns from, or add new features to any Old* class. Fix bugs in them only when the fix is isolated and does not require architectural change.

Companion surfaces

When touching voice code, also inspect:

Touching	Also inspect
VoiceGroupCrypto or crypto mode	SessionDescription, VoicePacket, VoiceGroupCryptoInterface, LibSodiumNotFoundException
Speaking or voice gateway opcode	Hello, Ready, Resumed, SessionDescription — full handshake chain
Discord.php voice handlers	Voice gateway opcodes, Buffer, external voice package Manager
Buffer.php	Multipart.php (similar streaming pattern), external voice package stream classes
Any new voice encryption mode	VoiceGroupCryptoInterface, crypto trait, SessionDescription mode list

Playbook: adding a new voice encryption mode

1. Add the mode constant to SessionDescription.
2. Implement the mode in a class using VoiceGroupCryptoTrait or extending VoiceGroupCrypto.
3. Register the mode in the external voice package's cipher negotiation if needed.
4. Update VoiceGroupCryptoInterface if the contract changes.
5. Verify libsodium function availability — throw LibSodiumNotFoundException if missing.
6. Add tests for encrypt/decrypt round-trip.

Playbook: adding a voice gateway opcode

1. Create a typed value class under src/Discord/Voice/ mirroring the Discord voice gateway docs.
2. Wire the opcode handler in Discord.php (find the voice WebSocket message handler).
3. Document the opcode sequence in the class docblock.
4. Do not put audio I/O logic in the opcode class — keep it as a typed payload.

Design tripwires

• Adding audio codec, UDP, or FFmpeg logic inside src/Discord/Voice/ — that belongs in the external voice package
• Extending any Old* class for new features
• Skipping libsodium availability check before using sodium functions
• Hard-coding a cipher mode instead of reading it from SessionDescription
• Blocking I/O inside voice packet or stream handlers — everything must be async/Promise-based
• Catching LibSodiumNotFoundException silently instead of surfacing it to the caller

Reference files

• src/Discord/Voice/VoiceGroupCrypto.php — encryption base
• src/Discord/Voice/VoicePacket.php — RTP packet wrapper
• src/Discord/Voice/SessionDescription.php — session key/mode
• src/Discord/Voice/Speaking.php — voice speaking opcode
• src/Discord/Helpers/Buffer.php — writable stream helper
• src/Discord/Exceptions/LibSodiumNotFoundException.php — crypto dependency guard
• src/Discord/Exceptions/OpusNotFoundException.php — codec dependency guard
• src/Discord/Exceptions/FFmpegNotFoundException.php — audio tool dependency guard