fix: handle unknown websocket control messages

[ash1shkumar]

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• I am assigned to this issue.
• I verified that this PR ONLY touches the required files.

Warning

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📋 PR Summary & Link

• **Closes [Bug/UnboundLocalError] Potential UnboundLocalError under ASR WebSocket connection errors #2097 **
• Summary:
  • Fixed a WebSocket edge case in apps/ml/routers/asr.py.
  • Added handling for unsupported control message types during streaming transcription.
  • The endpoint now returns a structured error response and closes the connection gracefully instead of leaving the session open.
  • Prevents unexpected client messages from causing undefined behavior in the streaming ASR flow.

📸 Proof of Work (Screenshots / Logs)

Backend change (no UI changes).

Manual Verification

• Started WebSocket streaming session successfully.
• Sent valid "start" message → received "ready" response.
• Sent valid "stop" message → received "final" response and connection closed normally.
• Sent unsupported control message type → received:

{
  "type": "error",
  "error": "Unknown control message type."
}

• Connection closed with code 1003 as expected.

🏷️ PR Type

• 🐛 type: bug
• ✨ type: feature
• 📖 type: docs
• 🧪 type: testing
• 🔒 type: security
• ⚡ type: performance
• 🎨 type: design
• ♻️ type: refactor
• 🛠️ type: devops
• ♿ type: accessibility

✅ Checklist

• My PR has a linked issue (Closes #2097 )
• I have pulled the latest main and resolved any conflicts

[github-actions]

🎉 Congratulations @ash1shkumar! Your Pull Request "fix: handle unknown websocket control messages" has been successfully merged by @dipexplorer.

Thank you for your valuable contribution to SahiDawa! 🇮🇳
If this was for GSSoC 2026, your work is officially merged and valid. Keep up the great work and feel free to claim other open issues. 🚀

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