Description

Voice/audio messages (OGG Opus) are saved as 0-byte empty files when using NOWEB engine with S3 media storage. Images download correctly through the same pipeline.

Version

• WAHA: 2026.2.1 (also confirmed in latest core branch source)
• Engine: NOWEB
• Tier: PLUS
• Media storage: S3 (AWS, eu-central-1)

Steps to reproduce

1. Configure WAHA with WAHA_MEDIA_STORAGE=S3 and a valid S3 bucket
2. Start a NOWEB session
3. Receive an image message → file saved to S3 with correct size (e.g. 143KB) ✅
4. Receive a voice message (PTT / audio/ogg) → file saved to S3 as 0 bytes ❌

Expected behavior

Voice/audio files should be saved with their actual content, same as images.

Actual behavior

• hasMedia: true in webhook ✅
• media.url present, pointing to S3 ✅
• File exists in S3 bucket ✅
• File size: 0 bytes ❌
• No errors in WAHA logs — the save appears successful

Analysis

The NOWEB media processor in session.noweb.core.ts calls:

return (await downloadMediaMessage(
  message,
  'buffer',   // <-- this mode
  {},
  {
    logger: this.logger,
    reuploadRequest: this.session.sock.updateMediaMessage,
  },
).finally(() => {
  content.url = url;
})) as Buffer;

The 'buffer' mode in Baileys silently returns an empty buffer for audio/voice messages without throwing an error. This is a known Baileys issue:

• [BUG] Bad decrypt while downloading media document WhiskeySockets/Baileys#681 (wrong HKDF key for audio-as-document)
• [BUG] WhatsApp voice messages download as 0-byte files (Baileys downloadMediaMessage returns empty buffer) openclaw/openclaw#4636 (0-byte voice, fix = switch to 'stream' mode)

Images are unaffected because they go through a different decryption path in Baileys.

Suggested fix

Switch from 'buffer' to 'stream' mode and collect chunks manually:

const stream = await downloadMediaMessage(
  message,
  'stream',
  {},
  {
    logger: this.logger,
    reuploadRequest: this.session.sock.updateMediaMessage,
  },
);
const chunks = [];
for await (const chunk of stream) {
  chunks.push(chunk);
}
return Buffer.concat(chunks);

This is the fix confirmed working in openclaw/openclaw#4636.

Environment

• OS: Linux x64 (Docker on AWS EC2)
• Deployment: Coolify
• S3 config: WAHA_S3_PROXY_FILES=false, WHATSAPP_FILES_LIFETIME=86400
• No WHATSAPP_FILES_MIMETYPES restriction (all types enabled)
• WHATSAPP_DOWNLOAD_MEDIA not set (defaults true)